JP7531451B2 - Grass trimmer - Google Patents

Description

The present invention relates to a grass cutter that is provided with a grass cutting device that is detachably supported on a connecting frame provided at one end of the machine body in the front-rear direction, and a power transmission mechanism that transmits power from the machine body to the grass cutting device, and in which the connecting frame to which the grass cutting device can be detached is connected to the machine body via a three-point link mechanism and a lifting/lowering mechanism that lifts and lowers the three-point link mechanism.

One type of lawnmower has a structure in which the grass cutting device is detachably supported on a connecting frame, and the connecting frame is connected to the body via a three-point link mechanism and a lifting operating mechanism so that it can be raised and lowered and swung up and down.
In this structure, a three-point link mechanism is formed by a lower link whose base end is supported near the rear wall of the machine body and whose free end extends rearward, and a top link provided from near the rear wall of the machine body to the upper end of the connecting frame. The lifting mechanism is configured such that the lower link is connected via a lift rod to the free end of a lift arm whose swing fulcrum is located above the rear of the machine body, and the lift arm can be raised and lowered by a lifting cylinder provided inside the machine body (not shown). The power transmission mechanism is configured such that a transmission shaft with universal joints at both ends is connected to a PTO shaft (power take-off shaft) taken out from the rear of the machine body, and a PIC shaft (power input shaft) to the grass cutting device is connected to the rear end of the transmission shaft, so that the grass cutting device is driven by power from an engine mounted on the machine body (see Patent Document 1).

JP 2003-250304 A

The structure described in the above-mentioned Patent Document 1 is configured so that the mowing height of the grass cutting device can be changed by changing the height of the rear end of the lower link through the swinging action of the lift arm.
In such a structure, for example, if the length of the lower link or the top link is set short and the mower is moved closer to the machine body in order to shorten the overall length of the mower, the swing angle of the lower link or the top link and the swing angle of the lift arm change in response to the change in the mowing height become large. As a result, the angle of the transmission shaft relative to the PTO shaft and the angle of the PIC shaft relative to the transmission shaft tend to become large. In this case, the power transmitted to the mower by the power transmission mechanism is transmitted at an extremely non-uniform rotation speed, which may reduce the mowing performance and power transmission efficiency. Therefore, a certain length is required for the lower link or the top link, making it difficult to further shorten the overall length of the mower.

The present invention aims to provide a grass cutter equipped with a grass cutting device that can change the cutting height using a three-point link mechanism, which can prevent the power transmitted to the grass cutting device by the power transmission mechanism from rotating at extremely non-uniform speeds even if the length of the lower link is relatively short and the connecting frame is brought close to the machine body, thereby making it easy to perform good grass cutting work.

The features of the grass cutter of the present invention are as follows:
Right and left running gears supporting the aircraft body;
A connecting frame provided at one end of the aircraft in the front-rear direction;
A grass cutting device detachably supported on the connecting frame;
A power transmission mechanism that transmits power from the machine body to the grass mowing device is provided,
the connecting frame is connected to the airframe via a three-point link mechanism having a pair of left and right lower links and a top link attached to the airframe so as to be able to swing up and down around a horizontal axis along the left-right direction, and a lifting and lowering mechanism that lifts and lowers the three-point link mechanism;
The power transmission mechanism is supported across the machine body and the connecting frame, and the power transmission mechanism is provided with a power take-off shaft provided at the one end of the machine body, a power input shaft that transmits power to the grass cutting device supported by the connecting frame, and a transmission shaft that connects the power take-off shaft and the power input shaft via universal joints provided at both ends,
the lifting mechanism includes a lift arm whose base end is pivotally supported on the vehicle body, a lift rod that connects a free end of the lift arm to the lower link, and a lifting cylinder that swings the lift arm up and down;
The lifting mechanism has a mowing lifting operation range from a lower limit mowing position where the mowing device performs mowing work at a minimum ground clearance near the ground to an upper limit mowing position where the mowing device performs mowing work at a position higher than the lower limit mowing position,
The three-point link mechanism is configured to be swingable such that, with respect to a vertical line passing through a pivot point at the base end of the top link connected to the machine body side, when the grass mowing device is in the lower limit mowing position, the free end of the top link is located away from the machine body than the vertical line, and when the grass mowing device is in the upper limit mowing position, the free end of the top link is swingable so as to cross the vertical line and approach the machine body side,
A pivot point at a base end of the top link connected to the machine body side is set at a position lower than the uppermost position of the power input shaft of the power transmission mechanism in a posture raised to the upper limit mowing position and higher than the transmission shaft ,
The lifting cylinder has a lower end connected to a bracket that protrudes from a vertical wall at one end of the body toward the side where the connecting frame is located, and an upper end connected to a position closer to the base end of the lift arm than the connection point of the lift rod to the lift arm .

According to the present invention, the free end of the top link in the three-point link mechanism is configured to be able to swing between a position farther from the aircraft body than the vertical line passing through the pivot point at the base end of the top link and a position beyond the vertical line approaching the aircraft body. In other words, by expanding the swinging range of the top link not only to a position farther from the aircraft body than the vertical line but also to a position beyond the vertical line approaching the aircraft body, a large swinging range of the top link is ensured and the amount of movement of the free end of the top link is increased.
The position of the pivot point at the base end of the top link is set lower than the uppermost position of the input shaft of the power transmission mechanism when the top link is raised to the upper limit mowing position and higher than the transmission shaft, so that the top link is positioned as low as possible without interfering with the lifting and lowering operation range of the power transmission mechanism. In this way, by setting the pivot point at the base end of the top link as low as possible, the length of the top link itself can be kept relatively long. As a result, the inclination angle of the line segment connecting the free end of the top link and the free end of the lower link with respect to the horizontal line becomes greater as the free end of the top link approaches the machine body. In other words, the connecting frame becomes greater as the free end of the top link approaches the machine body, so that the connecting frame becomes closer to horizontal.

In comparison, if the position of the pivot point at the base end of the top link were set at a position approximately equal to the height of the free end of the top link, the length of the top link itself would inevitably be shorter, and the swing trajectory of the free end of the top link would draw an arc of relatively short radius of curvature. In such a structure, if the free end of the top link attempts to move further toward the aircraft beyond the vertical line passing through the pivot point at the base end of the top link, the more the free end of the top link moves toward the aircraft, the more it will act in a direction that gradually pushes down the lower link. In reality, this movement will be in the opposite direction to the lifting direction of the lower link by the lift arm, and will become inoperable. In other words, in a structure in which such a short top link is pivoted at a high position, it will be impossible to move the free end of the top link further toward the aircraft beyond the vertical line passing through the pivot point at the base end of the top link. For this reason, the angle of inclination of the line segment connecting the free end of the top link and the free end of the lower link with respect to the horizontal line does not incline very much even when the free end of the top link is brought as close to the aircraft as possible, and there is little change from the upright state, compared to a structure in which a long top link is pivoted at a low position. In other words, even when the free end of the top link is brought as close to the aircraft as possible, the connecting frame does not incline very much and is close to the upright state.

For these reasons, in the present invention, in which a long top link is pivoted at a low position, the closer the free end of the top link is to the machine body, the greater the inclination angle of the power input shaft to the grass cutting device supported by the connecting frame relative to the horizontal line, compared to a structure in which a short top link is pivoted at a high position. This makes it easier to reduce the degree to which the power transmitted to the grass cutting device by the power transmission mechanism rotates at an uneven speed.
In other words, when the mowing height is changed to a higher side, the connecting frame is also lifted with the lifting of the lower link by the lift arm, and the mowing height of the grass cutting device connected to the connecting frame is changed. At this time, the power input shaft of the power transmission mechanism supported by the connecting frame is also lifted, and the end of the power input shaft side of the transmission shaft connected to the power take-off shaft provided at one end of the machine body is also lifted. Then, the transmission shaft, which is in a position where its axis intersects with the power take-off shaft, rotates at a non-uniform speed with respect to the power take-off shaft. In this state, if the transmission shaft and the power input shaft rotate at the same non-uniform speed, a driving force at a non-uniform speed will be transmitted to the grass cutting device. However, in the present invention, the connecting frame, which is lifted with the lifting of the lower link, is inclined so that the free end of the top link approaches the machine body and becomes closer to horizontal, so that the end of the power input shaft side of the transmission shaft is also changed in position so that the axis of the power input shaft intersects with the transmission shaft.
When the position of the power input shaft is changed in this manner so that the axis of the power input shaft intersects with the transmission shaft, the angle of intersection of the transmission shaft with the power take-off shaft becomes slightly gentler, reducing the degree of non-uniform rotation of the transmission shaft with respect to the power take-off shaft. In addition, the intersection of the axis of the power input shaft with the transmission shaft acts to offset the non-uniform rotation of the transmission shaft with respect to the power take-off shaft, so that the transmitted power from the power take-off shaft is transmitted to the grass cutting device with a reduced degree of non-uniform rotation.

In particular, in a grass cutter, the grass cutting device to be raised and lowered is not raised and lowered below the ground surface, i.e., into the ground, but is raised and lowered in a range above the ground surface, and the mowing height is adjusted to an appropriate level for mowing work. In the present invention, when the grass cutting height is adjusted by raising and lowering only above the ground surface, with the lower limit being close to the ground surface, power can be transmitted to the grass cutting device in a state in which the degree to which the power transmitted to the grass cutting device by the power transmission mechanism rotates at an uneven speed is reliably reduced, so a grass cutter with excellent grass cutting performance can be provided.
According to the present invention, the lift cylinder can perform a predetermined lifting and lowering operation with a relatively short stroke by effectively utilizing the length of the lift arm, so that the lift cylinder itself can be constructed in a small size.
The features of the grass cutter of the present invention are as follows:
Right and left running gears supporting the aircraft body;
A connecting frame provided at one end of the aircraft in the front-rear direction;
A grass cutting device supported detachably on the connecting frame;
A power transmission mechanism that transmits power from the machine body to the grass mowing device is provided,
the connecting frame is connected to the airframe via a three-point link mechanism having a pair of left and right lower links and a top link attached to the airframe so as to be able to swing up and down around a horizontal axis along the left-right direction, and a lifting and lowering mechanism that lifts and lowers the three-point link mechanism;
The power transmission mechanism is supported across the machine body and the connecting frame, and the power transmission mechanism is provided with a power take-off shaft provided at the one end of the machine body, a power input shaft that transmits power to the grass cutting device supported by the connecting frame, and a transmission shaft that connects the power take-off shaft and the power input shaft via universal joints provided at both ends,
the lifting mechanism includes a lift arm whose base end is pivotally supported on the vehicle body, a lift rod that connects a free end of the lift arm to the lower link, and a lifting cylinder that swings the lift arm up and down;
The lifting mechanism has a mowing lifting operation range from a lower limit mowing position where the mowing device performs mowing work at a minimum ground clearance near the ground to an upper limit mowing position where the mowing device performs mowing work at a position higher than the lower limit mowing position,
The three-point link mechanism is configured to be swingable such that, with respect to a vertical line passing through a pivot point at the base end of the top link connected to the machine body side, when the grass mowing device is in the lower limit mowing position, the free end of the top link is located away from the machine body than the vertical line, and when the grass mowing device is in the upper limit mowing position, the free end of the top link is swingable so as to cross the vertical line and approach the machine body side,
A pivot point at a base end of the top link connected to the machine body is set at a position lower than the uppermost position of the power input shaft of the power transmission mechanism in a posture raised to the upper limit mowing position and higher than the transmission shaft,
The left and right lift arms are connected to each other at their base ends so that they can swing together, and either the left or right lift arm is driven and raised and lowered by a single lifting cylinder to swing both the left and right arms simultaneously.
According to the present invention, the free end of the top link in the three-point link mechanism is configured to be able to swing between a position farther from the aircraft body than the vertical line passing through the pivot point at the base end of the top link and a position beyond the vertical line approaching the aircraft body. In other words, by expanding the swinging range of the top link not only to a position farther from the aircraft body than the vertical line but also to a position beyond the vertical line approaching the aircraft body, a large swinging range of the top link is ensured and the amount of movement of the free end of the top link is increased.
The position of the pivot point at the base end of the top link is set lower than the uppermost position of the input shaft of the power transmission mechanism when the top link is raised to the upper limit mowing position and higher than the transmission shaft, so that the top link is positioned as low as possible without interfering with the lifting and lowering operation range of the power transmission mechanism. In this way, by setting the pivot point at the base end of the top link as low as possible, the length of the top link itself can be kept relatively long. As a result, the inclination angle of the line segment connecting the free end of the top link and the free end of the lower link with respect to the horizontal line becomes greater as the free end of the top link approaches the machine body. In other words, the connecting frame becomes greater as the free end of the top link approaches the machine body, so that the connecting frame becomes closer to horizontal.
In comparison, if the position of the pivot point at the base end of the top link were set at a position approximately equal to the height of the free end of the top link, the length of the top link itself would inevitably be shorter, and the swing trajectory of the free end of the top link would draw an arc with a relatively short radius of curvature. In such a structure, if the free end of the top link attempts to move further toward the aircraft body beyond the vertical line passing through the pivot point at the base end of the top link, the more the free end of the top link moves toward the aircraft body, the more it acts in a direction that gradually pushes down the lower link. In reality, this movement is in a direction opposite to the lifting direction of the lower link by the lift arm, and the operation becomes impossible. In other words, in a structure in which such a short top link is pivoted at a high position, it is impossible to move the free end of the top link further toward the aircraft body beyond the vertical line passing through the pivot point at the base end of the top link. For this reason, the angle of inclination of the line segment connecting the free end of the top link and the free end of the lower link with respect to the horizontal line does not incline very much even when the free end of the top link is brought as close to the aircraft as possible, and there is little change from the upright state, compared to a structure in which a long top link is pivoted at a low position. In other words, even when the free end of the top link is brought as close to the aircraft as possible, the connecting frame does not incline very much and is close to the upright state.
For these reasons, in the present invention, in which a long top link is pivoted at a low position, the closer the free end of the top link is to the machine body, the greater the inclination angle of the power input shaft to the grass cutting device supported by the connecting frame relative to the horizontal line, compared to a structure in which a short top link is pivoted at a high position. This makes it easier to reduce the degree to which the power transmitted to the grass cutting device by the power transmission mechanism rotates at an uneven speed.
In other words, when the mowing height is changed to a higher side, the connecting frame is also lifted with the lifting of the lower link by the lift arm, and the mowing height of the grass cutting device connected to the connecting frame is changed. At this time, the power input shaft of the power transmission mechanism supported by the connecting frame is also lifted, and the end of the power input shaft side of the transmission shaft connected to the power take-off shaft provided at one end of the machine body is also lifted. Then, the transmission shaft, which is in a position where its axis intersects with the power take-off shaft, rotates at a non-uniform speed with respect to the power take-off shaft. In this state, if the transmission shaft and the power input shaft rotate at the same non-uniform speed, a driving force at a non-uniform speed will be transmitted to the grass cutting device. However, in the present invention, the connecting frame, which is lifted with the lifting of the lower link, is inclined so that the free end of the top link approaches the machine body and becomes closer to horizontal, so that the end of the power input shaft side of the transmission shaft is also changed in position so that the axis of the power input shaft intersects with the transmission shaft.
When the position of the power input shaft is changed in this manner so that the axis of the power input shaft intersects with the transmission shaft, the angle of intersection of the transmission shaft with the power take-off shaft becomes slightly gentler, reducing the degree of non-uniform rotation of the transmission shaft with respect to the power take-off shaft. In addition, the intersection of the axis of the power input shaft with the transmission shaft acts to offset the non-uniform rotation of the transmission shaft with respect to the power take-off shaft, so that the transmitted power from the power take-off shaft is transmitted to the grass cutting device with a reduced degree of non-uniform rotation.
In particular, in a grass cutter, the grass cutting device to be raised and lowered is not raised and lowered below the ground surface, i.e., into the ground, but is raised and lowered in a range above the ground surface, and the mowing height is adjusted to an appropriate level for mowing work. In the present invention, when the grass cutting height is adjusted by raising and lowering only above the ground surface, with the lower limit being close to the ground surface, power can be transmitted to the grass cutting device in a state in which the degree to which the power transmitted to the grass cutting device by the power transmission mechanism rotates at an uneven speed is reliably reduced, so a grass cutter with excellent grass cutting performance can be provided.
According to the present invention, the left and right lift arms can be raised and lowered by a single lift cylinder, which makes it easy to reduce costs by reducing the number of parts.
The features of the grass cutter of the present invention are as follows:
Right and left running gears supporting the aircraft body;
A connecting frame provided at one end of the aircraft in the front-rear direction;
A grass cutting device supported detachably on the connecting frame;
A power transmission mechanism that transmits power from the machine body to the grass mowing device is provided,
the connecting frame is connected to the airframe via a three-point link mechanism having a pair of left and right lower links and a top link attached to the airframe so as to be able to swing up and down around a horizontal axis along the left-right direction, and a lifting and lowering mechanism that lifts and lowers the three-point link mechanism;
The power transmission mechanism is supported across the machine body and the connecting frame, and the power transmission mechanism is provided with a power take-off shaft provided at the one end of the machine body, a power input shaft that transmits power to the grass cutting device supported by the connecting frame, and a transmission shaft that connects the power take-off shaft and the power input shaft via universal joints provided at both ends,
the lifting mechanism includes a lift arm whose base end is pivotally supported on the vehicle body, a lift rod that connects a free end of the lift arm to the lower link, and a lifting cylinder that swings the lift arm up and down;
The lifting mechanism has a mowing lifting operation range from a lower limit mowing position where the mowing device performs mowing work at a minimum ground clearance near the ground to an upper limit mowing position where the mowing device performs mowing work at a position higher than the lower limit mowing position,
The three-point link mechanism is configured to be swingable such that, with respect to a vertical line passing through a pivot point at the base end of the top link connected to the machine body side, when the grass mowing device is in the lower limit mowing position, the free end of the top link is located away from the machine body than the vertical line, and when the grass mowing device is in the upper limit mowing position, the free end of the top link is swingable so as to cross the vertical line and approach the machine body side,
A pivot point at a base end of the top link connected to the machine body side is set at a position lower than the uppermost position of the power input shaft of the power transmission mechanism in a posture raised to the upper limit mowing position and higher than the transmission shaft,
The top link has a curved portion formed in a portion of its length from the base end to the free end in order to avoid interference with other objects provided on the aircraft body.
According to the present invention, the free end of the top link in the three-point link mechanism is configured to be able to swing between a position farther from the aircraft body than the vertical line passing through the pivot point at the base end of the top link and a position beyond the vertical line approaching the aircraft body. In other words, by expanding the swinging range of the top link not only to a position farther from the aircraft body than the vertical line but also to a position beyond the vertical line approaching the aircraft body, a large swinging range of the top link is ensured and the amount of movement of the free end of the top link is increased.
The position of the pivot point at the base end of the top link is set lower than the uppermost position of the input shaft of the power transmission mechanism when the top link is raised to the upper limit mowing position and higher than the transmission shaft, so that the top link is positioned as low as possible without interfering with the lifting and lowering operation range of the power transmission mechanism. In this way, by setting the pivot point at the base end of the top link as low as possible, the length of the top link itself can be kept relatively long. As a result, the inclination angle of the line segment connecting the free end of the top link and the free end of the lower link with respect to the horizontal line becomes greater as the free end of the top link approaches the machine body. In other words, the connecting frame becomes greater as the free end of the top link approaches the machine body, so that the connecting frame becomes closer to horizontal.
In comparison, if the position of the pivot point at the base end of the top link were set at a position approximately equal to the height of the free end of the top link, the length of the top link itself would inevitably be shorter, and the swing trajectory of the free end of the top link would draw an arc with a relatively short radius of curvature. In such a structure, if the free end of the top link attempts to move further toward the aircraft body beyond the vertical line passing through the pivot point at the base end of the top link, the more the free end of the top link moves toward the aircraft body, the more it acts in a direction that gradually pushes down the lower link. In reality, this movement is in a direction opposite to the lifting direction of the lower link by the lift arm, and the operation becomes impossible. In other words, in a structure in which such a short top link is pivoted at a high position, it is impossible to move the free end of the top link further toward the aircraft body beyond the vertical line passing through the pivot point at the base end of the top link. For this reason, the angle of inclination of the line segment connecting the free end of the top link and the free end of the lower link with respect to the horizontal line does not incline very much even when the free end of the top link is brought as close to the aircraft as possible, and there is little change from the upright state, compared to a structure in which a long top link is pivoted at a low position. In other words, even when the free end of the top link is brought as close to the aircraft as possible, the connecting frame does not incline very much and is close to the upright state.
For these reasons, in the present invention, in which a long top link is pivoted at a low position, the closer the free end of the top link is to the machine body, the greater the inclination angle of the power input shaft to the grass cutting device supported by the connecting frame relative to the horizontal line, compared to a structure in which a short top link is pivoted at a high position. This makes it easier to reduce the degree to which the power transmitted to the grass cutting device by the power transmission mechanism rotates at an uneven speed.
In other words, when the mowing height is changed to a higher side, the connecting frame is also lifted with the lifting of the lower link by the lift arm, and the mowing height of the grass cutting device connected to the connecting frame is changed. At this time, the power input shaft of the power transmission mechanism supported by the connecting frame is also lifted, and the end of the power input shaft side of the transmission shaft connected to the power take-off shaft provided at one end of the machine body is also lifted. Then, the transmission shaft, which is in a position where its axis intersects with the power take-off shaft, rotates at a non-uniform speed with respect to the power take-off shaft. In this state, if the transmission shaft and the power input shaft rotate at the same non-uniform speed, a driving force at a non-uniform speed will be transmitted to the grass cutting device. However, in the present invention, the connecting frame, which is lifted with the lifting of the lower link, is inclined so that the free end of the top link approaches the machine body and becomes closer to horizontal, so that the end of the power input shaft side of the transmission shaft is also changed in position so that the axis of the power input shaft intersects with the transmission shaft.
When the position of the power input shaft is changed in this manner so that the axis of the power input shaft intersects with the transmission shaft, the angle of intersection of the transmission shaft with the power take-off shaft becomes slightly gentler, reducing the degree of non-uniform rotation of the transmission shaft with respect to the power take-off shaft. In addition, the intersection of the axis of the power input shaft with the transmission shaft acts to offset the non-uniform rotation of the transmission shaft with respect to the power take-off shaft, so that the transmitted power from the power take-off shaft is transmitted to the grass cutting device with a reduced degree of non-uniform rotation.
In particular, in a grass cutter, the grass cutting device to be raised and lowered is not raised and lowered below the ground surface, i.e., into the ground, but is raised and lowered in a range above the ground surface, and the mowing height is adjusted to an appropriate level for mowing work. In the present invention, when the grass cutting height is adjusted by raising and lowering only above the ground surface, with the lower limit being close to the ground surface, power can be transmitted to the grass cutting device in a state in which the degree to which the power transmitted to the grass cutting device by the power transmission mechanism rotates at an uneven speed is reliably reduced, so a grass cutter with excellent grass cutting performance can be provided.
According to the present invention, the presence of the curved portion ensures a wide swing range for the top link, while making it easier to avoid contact with the top link even when a component with a larger protruding amount is used as a component attached to the aircraft body, such as an oil filter.

In the present invention, it is preferable that the power transmission mechanism is configured so that the axis of the power take-off shaft connected to the transmission shaft and the axis of the power input shaft are linearly connected at the lower limit mowing position, and that the crossing angle between the axis of the power take-off shaft and the axis of the power input shaft and the axis of the transmission shaft are the same or nearly the same in the mowing lifting range from the lower limit mowing position to the upper limit mowing position.

According to this configuration, in the mowing lifting operation range from the lower limit mowing position to the upper limit mowing position, the crossing angle between the axis of the power take-off shaft and the axis of the power transmission shaft is the same or nearly the same as the crossing angle between the axis of the power input shaft and the axis of the power transmission shaft. This reduces non-uniform rotation of the power transmitted to the grass cutting device at all mowing heights within the mowing lifting operation range, making it easier to perform good grass cutting work.
In particular, near the lower limit mowing position, which is the area where the lawnmower is used most frequently, the axis of the power take-off shaft connected to the transmission shaft and the axis of the power input shaft are connected in a straight line, and there is almost no uneven rotation, making it easy to transmit power more efficiently.

In the present invention, it is preferable that the universal joint that flexibly connects the transmission shaft and the power input shaft is provided at a position closer to the connection point of the lower link to the aircraft body than the connection point of the lower link and the connecting frame.

With this configuration, the universal joint located between the transmission shaft and the power input shaft is bent at a specified bending angle as the attitude of the connecting frame relative to the aircraft body is changed, making it easier to connect in a state that corrects speed fluctuations due to non-uniform rotation.

In the present invention, it is preferable that the angle formed by the line segment connecting the base end and free end of the top link at the lower limit mowing position with respect to a vertical line passing through the pivot point at the base end of the top link and the angle formed by the line segment connecting the base end and free end of the top link at the upper limit mowing position with respect to a vertical line passing through the pivot point at the base end of the top link are set to be approximately the same.

This configuration makes it possible to set the swing range of the top link over a wide range that exceeds the vertical line passing through the pivot point at the base end of the top link, and makes it easier to correct speed fluctuations due to non-uniform rotation throughout that wide swing range.

In the present invention, it is preferable that the connection point of the base end of the top link to the aircraft body is located farther toward the connecting frame than the connection point of the lower link to the aircraft body.

With this configuration, the connection point of the base end of the top link to the aircraft is located farther toward the connecting frame than the connection point of the lower link to the aircraft, making it easier to effectively use the space between the aircraft and the connecting frame and to set a larger swing range for the top link.

In the present invention, it is preferable that the left and right lift arms are positioned laterally closer to the center of the aircraft than the left and right lower links.

With this configuration, the lift arm, which is positioned laterally closer to the center of the aircraft than the lower link, is protected on both sides by the lower link, making it easier to avoid contact with other objects such as weeds or trees.

In the present invention, it is preferable that the grass cutting device is equipped with a flail mower that is driven to rotate around a horizontal axis that runs along the left-right direction.

With this configuration, even if the swing range of the top link is widened and the change in the tilt angle of the connecting frame in the fore-and-aft direction increases, because the grass cutting device is a flail mower, there is no significant change in grass cutting performance, as with grass cutting devices that use blades that rotate around vertical axes.
Therefore, it is possible to obtain a grass cutter that allows easy mowing work with a large change in mowing height.

FIG. 2 is a right side view showing the entire grass mower. FIG. 2 is a plan view showing the entire grass cutter. FIG. 2 is an exploded perspective view showing a connection mechanism and a power transmission mechanism between the machine body and the grass cutting device. 4 is a side view showing a connection mechanism and a power transmission mechanism between the machine body and the grass cutting device. FIG. FIG. FIG. 13 is an explanatory side view showing the connecting mechanism and the power transmission mechanism at a lower limit position. FIG. 13 is an explanatory side view showing the connecting mechanism and the power transmission mechanism at an upper limit position. 10A and 10B are explanatory diagrams showing the operation form of the connecting frame and the power transmission mechanism using a three-point link mechanism. 11A and 11B are explanatory diagrams showing the operation form of a connecting frame and a power transmission mechanism using a three-point link mechanism in a comparative example. FIG. 11 is a side view showing a connecting mechanism and a power transmission mechanism in another embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the description of this embodiment, the front-rear and left-right directions are described as follows unless otherwise specified. That is, the forward traveling direction (see arrow F in Figs. 1 and 2) when the mower to which the present invention is applied is traveling for work is "forward", the backward traveling direction (see arrow B in Figs. 1 and 2) is "rear", the direction corresponding to the right side based on the forward posture in the front-rear direction (see arrow R in Fig. 2) is "right", and similarly the direction corresponding to the left side (see arrow L in Fig. 2) is "left". Arrow U in Figs. 3 and 4 indicates "up" of the mower, and arrow D indicates "down".

[Overall configuration of the lawnmower]
1 and 2, the grass cutter is configured to be self-propelled and includes a body 1, a pair of left and right crawler-type traveling devices 2 that support the body 1, and a grass cutting device 3 located in front of the body 1. The grass cutting device 3 is connected to the body 1 via a connecting mechanism K, and is supported in a state in which it can be raised and lowered relative to the body 1.

The machine body 1 is provided with a machine body frame 10 located between the left and right traveling devices 2. On this machine body frame 10, a driving part 11 having an engine 12, a transmission case 13, etc. is mounted.
As shown in Fig. 5, power output from the engine 12 is input to a transmission case 13 and is changed in speed within the transmission case 13 into propulsion power and working power. The propulsion power is branched to the left and right within the transmission case 13 and is output to the left and right traveling devices 2 via a pair of left and right hydrostatic continuously variable transmissions 14 serving as main transmissions. The working power is branched to the front within the transmission case 13 and is output from a PTO shaft 16 via a working clutch 15. The rotational power extracted by this PTO shaft 16 is transmitted as driving force for the grass cutting device 3 located in front of the machine body 1 via a power transmission mechanism 7 described below.

The traveling device 2 has a drive wheel 22 attached to a drive shaft 21 to which power is transmitted from the hydrostatic continuously variable transmission 14, and is equipped with a rubber crawler belt 25 wound around the drive wheel 22, an idler wheel 23, and a number of guide rollers 24. The idler wheels 23 and guide rollers 24 are supported by the forward/rearward frame portions 10A on both the left and right sides of the vehicle frame 10. In other words, the forward/rearward frame portions 10A are used as track frames for supporting the idler wheels 23 and guide rollers 24.

The machine body 1 is equipped with a steering control device (not shown) for operating the traveling device 2 and the grass cutting device 3. This steering control device is configured to receive control signals from an external radio control device (not shown) and operate the engine 12 and hydrostatic continuously variable transmission 14, etc., based on the received control commands to drive, stop, steer, etc. the traveling device 2. The steering control device is also configured to receive control signals from an external radio control device (not shown) and operate the working clutch 15 based on the received control commands to drive, stop, etc. the grass cutting device 3. In other words, this grass cutting machine is a so-called radio-controlled grass cutting machine that can be remotely controlled by a radio control device.

[About the grass cutting device]
1 to 4, the grass cutting device 3 has an upper part covered by a blade housing 30 and is provided with a blade drive shaft 31 that extends elongatedly to the left and right along the lateral direction of the machine body 1. A number of knife blades 32 are attached to and driven to rotate on this blade drive shaft 31. In other words, the grass cutting device 3 is a so-called flail mower that is configured to drive and rotate the knife blades 32 about the lateral axis x1 of the blade drive shaft 31.

As shown in Figures 3 to 5, power is transmitted from the engine 12 to the grass cutting device 3 via the power transmission mechanism 7. That is, an input case 37 is fixed to the rear of the blade housing 30, and a power input shaft 33 that constitutes part of the power transmission mechanism 7 is supported on this input case 37. The input case 37 also supports an end of a lateral transmission shaft 34 that extends laterally outward along the blade drive shaft 31, and power is transmitted from the power input shaft 33 to the lateral transmission shaft 34 via a bevel gear interlocking mechanism provided inside the input case 37. The power transmitted to the lateral transmission shaft 34 is transmitted to the blade drive shaft 31 via a belt transmission mechanism 35.

On both sides of the blade housing 30, there is provided a sled-shaped ground support 36 with a downward bent central portion in the front-to-rear direction. This ground support 36 is attached so that it slides on the ground during grass cutting work, and is intended to stably maintain the cutting height of the grass cutting device 3. It is pivoted to the blade housing 30 around the front horizontal axis x2 so that it can swing up and down, and is configured so that the cutting height can be changed and adjusted by changing the mounting height of the rear end relative to the blade housing 30.

[Connecting mechanism]
The connecting mechanism K, which supports the grass cutting device 3 in a state in which it can be raised and lowered relative to the machine body 1, is configured as follows.
As shown in Figures 1 to 4, the connecting mechanism K includes a connecting frame 4 for detachably supporting the grass cutting device 3, a pair of left and right lower links 50 attached to the machine body 1 so as to be able to swing up and down about a horizontal axis x3 along the left-right direction, and a three-point link mechanism 5 having a top link 51 attached to the machine body 1 so as to be able to swing up and down about another horizontal axis x4 along the left-right direction, and a lifting operation mechanism 6 for raising and lowering the three-point link mechanism 5.

[About the consolidated frame]
The connecting frame 4 is composed of a combination of an intermediate frame 40 connected to the three-point link mechanism 5 and an engagement/disengagement frame 41 that is detachable from the intermediate frame 40 and is attached so as to be capable of rotating relatively to the grass cutting device 3 around the front-to-rear axis z1.
The relay frame 40 has a lower end pivotally supported to the free end of the lower link 50 so as to be rotatable relative to the lower link 50 about a horizontal axis x5 extending in the left-right direction. The relay frame 40 has an upper end pivotally supported to the free end of the top link 51 so as to be rotatable relative to the top link 51 about a horizontal axis x6 extending in the left-right direction.

A U-shaped recess 40a is formed in the lower part of both the left and right sides of the relay frame 40, and a support shaft 41a protruding laterally outward from both the left and right sides of the engagement/disengagement frame 41 is configured to be engageable and disengageable from the front side into this recess 40a.
An engagement recess 40b for engaging with a locking pin 41b provided on the upper part of the engagement frame 41 is formed on the upper part of the relay frame 40, forward of the connection point with the top link 51. The engagement frame 41 is connected to the relay frame 40 in a vertically engaged state by engaging the locking pin 41b with the engagement recess 40b and engaging the support shaft 41a with the U-shaped recess 40a.

A tubular shaft portion 41c protrudes forward from the front side of the engagement/disengagement frame 41. An attachment frame 42 that is connected integrally to the grass cutting device 3 is disposed at a position facing the front side of the engagement/disengagement frame 41, and a boss portion 42a that fits onto the tubular shaft portion 41c of the engagement/disengagement frame 41 is integrally formed on the attachment frame 42. By fitting the boss portion 42a onto the tubular shaft portion 41c, the attachment frame 42 can be attached to the engagement/disengagement frame 41 so as to be relatively rotatable around the front-to-rear axis z1 of the tubular shaft portion 41c. This allows the grass cutting device 3 to be supported so as to be swingable around the front-to-rear axis z1.

[About the three-point link mechanism]
As shown in FIGS. 2 to 7, the three-point link mechanism 5 includes a pair of left and right lower links 50 and a single top link 51 located near the center of both lower links 50 in the left-right direction.
A rising frame 10B, which is shaped like a gate when viewed from the front, is erected on the front end of a pair of left and right front-rear frame portions 10A of the vehicle frame 10. A pair of left and right support brackets 10C that are long in the vertical direction, and a horizontal frame 10D that extends horizontally along the left-right direction so as to span the left and right support brackets 10C are attached to the front surface of this rising frame 10B. The rising frame 10B, support brackets 10C, and horizontal frame 10D are part of the vehicle frame 10 and are configured to also serve as the vertical wall 8 at the front of the vehicle 1.

The left and right lower links 50 have their base ends pivoted to a pivot shaft 80 provided near the bottom of the support bracket 10C. This pivot shaft 80 has a horizontal axis x3 that is the axis around which the lower links 50 swing up and down. The free ends of the lower links 50 are connected to the lower part of the connecting frame 4 so as to be relatively rotatable about the horizontal axis x5. In other words, the support shafts 41a that protrude laterally outward from both the left and right sides of the engagement/disengagement frame 41 are inserted into bosses 50a provided at the free ends of the lower links 50, and the free ends of the lower links 50 are connected to the connecting frame 4 so as to be relatively rotatable about the horizontal axis x5, which is the axis of the support shafts 41a.

The top link 51 is pivoted at its base end to a support shaft 81a provided at the protruding end of a pair of left and right mounting brackets 81 attached to the front of the horizontal frame 10D of the vertical wall 8. The top link 51 is supported by the aircraft body 1 so as to be swingable around the horizontal axis x4, which is the axis of this support shaft 81a. In other words, the horizontal axis x4 (corresponding to the connection point), which is the pivot point to the aircraft body 1 at the base end of the top link 51, is located further toward the connecting frame 4 than the horizontal axis x3 (corresponding to the connection point) of the lower link 50 relative to the aircraft body 1. The free end of the top link 51 is connected to the upper part of the relay frame 40 in the connecting frame 4 so as to be relatively rotatable around the horizontal axis x6.

The swing range of the free end of the top link 51 is set so that it can move back and forth beyond the vertical line y1 passing through the horizontal axis x4, which is the axis of the support shaft 81a that serves as the pivot point at the base end of the top link 51. More specifically, as shown in FIG. 7, the angle θ1 that the line segment Ld that connects the base end and free end of the top link 51 with the vertical line y1 when the grass cutting device 3 is in the lower limit mowing position is approximately the same as the angle θ2 that the line segment Lu that connects the base end and free end of the top link 51 with the vertical line y1 when the grass cutting device 3 is in the upper limit mowing position is approximately the same.

Furthermore, the vertical position of the support shaft 81a, which is the pivot point at the base end of the top link 51, is determined in consideration of the positional relationship with the power transmission mechanism 7 so that the length of the top link 51 can be set as long as possible. In other words, when the grass cutting device 3 is raised to the upper limit position, the support shaft 81a is positioned lower than the uppermost position of the power input shaft 33 of the power transmission mechanism 7 and higher than the transmission shaft 17. The uppermost position of the power input shaft 33 will be described later.
In this way, by setting the height position of the pivot point at the base end of the top link 51 to the lowest position possible without interfering with the lifting and lowering range of the power transmission mechanism 7, the distance between the base end and the free end of the top link 51 is made as large as possible, and the length of the top link 51 is ensured to be as long as possible.

[Lifting mechanism]
The lifting/lowering mechanism 6 comprises a pair of left and right lift arms 60 pivotally supported at their base ends on the machine body 1, a lift rod 61 connecting the free end of each lift arm 60 to the lower link 50, and a lifting cylinder 62 which causes the lift arms 60 to swing up and down.
2 to 4, the left and right lift arms 60 are connected at their base ends via a connecting tube 63 so as to rotate together on the left and right. A horizontal support shaft (not shown) connected and fixed to the support bracket 10C of the vertical wall 8 is fitted inside the connecting tube 63. This allows the connecting tube 63 and the left and right lift arms 60 to be supported rotatably around the horizontal axis x7.
A lift rod 61 that connects the lower link 50 in a suspended state is pivotally supported on the free end of the lift arm 60 so as to be rotatable about a horizontal axis x8. The lower end of the lift rod 61 is connected to a longitudinal midpoint of the lower link 50. The left and right lift arms 60 are disposed closer to the center of the aircraft than the left and right lower links 50 in the left-right direction.

The lower end of the lift cylinder 62 is connected to the support bracket 10C, which is a bracket that protrudes from the vertical wall 8 at one end of the body 1 toward the side where the connecting frame 4 is located. In other words, the lower end is supported by the support bracket 10C so as to be swingable around the horizontal axis x10 at a position that protrudes toward the side where the connecting frame 4 is located further away from the point where the base end of the lower link 50 is supported. The upper end of the lift cylinder 62 is connected to the lift arm 60 so as to be swingable around the horizontal axis x11 at a position closer to the base end of the lift arm 60 than the connection point of the lift rod 61 to the lift arm 60.

The length from the horizontal axis x3 at the base end of the lower link 50 to the horizontal axis x9 at the connection point of the lift rod 61 is approximately the same as the length from the horizontal axis x7 at the base end of the lift arm 60 to the horizontal axis x8 at the connection point of the lift rod 61, but the length from the horizontal axis x7 at the base end of the lift arm 60 to the horizontal axis x11 at the connection point of the upper end of the lift cylinder 62 is set shorter than these. As a result, the amount of extension and contraction of the lift cylinder 62 is shorter than the amount of vertical movement of the horizontal axis x8 or x9 at the connection point of the lift rod 61.
Therefore, although not shown, for example, compared to a structure in which one end of the lifting cylinder 62 is supported on the upper part of the aircraft body 1 and the other end is directly connected to the lower link 50, without using a lift arm 60 or lift rod 61, and the lower link 50 is raised and lowered in a suspended state, the amount of extension and contraction of the lifting cylinder 62 can be reduced, making the lifting cylinder 62 more compact.

Furthermore, the lift cylinder 62 is composed of a single hydraulic cylinder connected only to the right lift arm 60 of the left and right lift arms 60, and is not connected to the left lift arm 60. However, since the base ends of the left and right lift arms 60 are connected via the connecting tube 63 so as to rotate integrally on the left and right, the single lift cylinder 62 can be used to lift and lower the left and right lift arms 60 by the same amount at the same time.
As shown in FIG. 2, the left and right lift arms 60 are disposed closer to the center of the aircraft in the left-right direction than the left and right lower links 50, so the lift cylinders 62 that raise and lower the lift arms 60 are also disposed closer to the center of the aircraft than the left and right lower links 50.

[Power transmission mechanism]
As shown in Figures 3 to 5, the power transmission mechanism 7 includes a PTO shaft 16 supported by the body 1, a power input shaft 33 of the grass cutting device 3, and a transmission shaft 17 that is connected to the PTO shaft 16 and the power input shaft 33 with universal joints 18, 18 at both ends between the PTO shaft 16 and the power input shaft 33.

The PTO shaft 16 protrudes horizontally from the front surface of the transmission case 13 and extends forward, and a universal joint 18 on the rear end side of the transmission shaft 17 is connected to its front end.
The vertical height of the PTO shaft 16 is set to be approximately the same as the height of the lower link 50 at the lowest mowing position in a side view. Also, the bending point of the universal joint 18 connecting the front end of the PTO shaft 16 and the rear end of the transmission shaft 17, i.e., bending center point p1, is at a height position approximately the same as the horizontal axis x3 of the base end of the lower link 50 in a side view and is located slightly rearward, but this bending center point p1 and the horizontal axis x3 may be in exactly the same position in a side view.
The bending center point p1 is the intersection point of the central axis L1 of the PTO shaft 16 and the central axis L2 of the transmission shaft 17.

The transmission shaft 17 is equipped with universal joints 18, 18 at both ends, with the universal joint 18 at one end connected to the PTO shaft 16 and the universal joint 18 at the other end connected to the power input shaft 33 so that its relative position can be changed. The bending point of the universal joint 18 connecting the front end of the transmission shaft 17 and the rear end of the power input shaft 33, i.e., bending center point p2, is located further rearward and closer to the aircraft 1 than the horizontal axis x5 of the free end of the lower link 50 in a side view. This bending center point p2 is the intersection of the central axis L2 of the transmission shaft 17 and the central axis L3 of the power input shaft 33.

The PTO shaft 16 is supported by the transmission case 13, and the power input shaft 33 is supported by the grass cutting device 3, but the transmission shaft 17 is not supported by the transmission case 13 or the grass cutting device 3. Instead, the transmission shaft 17 is located between the PTO shaft 16 and the power input shaft 33, and is supported by the PTO shaft 16 and the power input shaft 33 via universal joints 18, 18.
When the ground support 36 of the grass cutting device 3 is in the lower limit mowing position in contact with the ground surface, the central axis L2 of the transmission shaft 17 is aligned in a straight line with the central axis L1 of the PTO shaft 16 and the central axis L3 of the power input shaft 33. As a result, power is transmitted to the grass cutting device 3 by the concentric rotation of the PTO shaft 16, the transmission shaft 17, and the power input shaft 33, with the central axes L1, L2, and L3 of the three being aligned in a straight line. Therefore, grass cutting work is performed with the least power loss.

When the grass cutting device 3 is lifted via the connecting frame 4 by the lifting operating mechanism 6 and the three-point link mechanism 5, the front end of the transmission shaft 17 is also lifted via the universal joint 18 as the lifted connecting frame 4 and the power input shaft 33 supported by the grass cutting device 3 rise.
As shown in Fig. 7, the connecting frame 4 and the grass cutting device 3 are gradually tilted backward as they are raised, with the upper side gradually approaching the machine body 1. At this time, the central axis L3 of the power input shaft 33 is changed from a nearly horizontal position when it was in the lower limit mowing position to a front-up position in which the side farther from the machine body 1 is at a higher position. Accordingly, the front end of the transmission shaft 17 connected via the universal joint 18 is also raised, but since the connecting frame 4 and the grass cutting device 3 are changed to a rearward tilt, the bending center point p2, which is the intersection of the central axis L3 of the power input shaft 33 and the central axis L2 of the transmission shaft 17, is located closer to the machine body 1 than the horizontal axis x5 of the free end of the lower link 50, and is therefore not raised to the same height as the horizontal axis x5 but is located lower than the horizontal axis x5.

As a result, the central axis L3 of the power input shaft 33 bends with respect to the central axis L2 of the transmission shaft 17, and the central axis L3 of the power input shaft 33 is inclined by the crossing angle β with respect to the central axis L2 of the transmission shaft 17. Then, because the front end of the transmission shaft 17 is lifted, the central axis L2 of the transmission shaft 17 bends with respect to the central axis L1 of the PTO shaft 16, and is inclined by the crossing angle α.
This crossing angle α and the crossing angle β mentioned above change as the height of the horizontal axis x5 of the free end of the lower link 50 changes over the entire lifting and lowering range of the grass mower 3, from the lower limit mowing position of the grass mower 3 shown in Fig. 6 to the upper limit mowing position shown in Fig. 7. However, in a comparison under conditions where the horizontal axis x5 is at the same height, the rotation radius of the lower link 50 and the top link 51 in the three-point linkage 5, and the positions of the horizontal axis x3, the horizontal axis x4, the horizontal axis x5, and the horizontal axis x6, as well as the positional relationship with the vertical line y1 are determined so that the crossing angles α and β are approximately the same.

The power input shaft 33 is supported with its rear end inserted in an input case 37 of the grass cutting device 3, and is linked to the lateral transmission shaft 34 by a bevel gear inside the input case 37 as shown in FIG.
The symbol p3 shown in Figures 4, 6, and 7 indicates a position corresponding to the axial center line of the horizontal transmission shaft 34. However, since this is a position very close to the bevel gear 33a provided at the end (front end) of the power input shaft 33 in the power transmission mechanism 7, for convenience, it is shown as the uppermost position of the power input shaft 33 in the power transmission mechanism 7.
In other words, the uppermost position of the power input shaft 33 of the power transmission mechanism 7 when the grass cutting device 3 is lifted to the upper limit cutting position is the position of the end (front end) of the power input shaft 33 at the upper limit cutting position, but for convenience of drawing, this is represented by the symbol p3 shown in Figures 4, 6, and 7.

The horizontal axis x4, which is the axis of the support shaft 81a that serves as the pivot point at the base end of the top link 51 described above, is set at a position lower than the position indicated by symbol p3, which corresponds to the position of the end (front end) of the power input shaft 33, and higher than the transmission shaft 17 at the upper limit cutting position. In this way, the height of the pivot point at the base end of the top link 51 is set to the lowest position that does not interfere with the lifting and lowering operating range of the power transmission mechanism 7.

The horizontal position of the pivot point at the base end of the top link 51 is located in the center between the left and right lower links 50, 50 in the left-right direction. In other words, the base end is pivoted to a support shaft 81a provided at the forward protruding end of a pair of left and right mounting brackets 81 attached to the front surface of the cross frame 10D of the front vertical wall 8 of the front part of the aircraft body 1. The pair of left and right mounting brackets 81 are provided on both left and right sides so as to cover the lateral sides of the oil filter 13a that protrudes forward from the vertical wall 8 from the transmission case 13.
The mounting bracket 81 extends forward beyond the front end of the oil filter 13a, and the support shaft 81a extending between the left and right mounting brackets 81, 81 is supported by the mounting bracket 81 at a position forward of the front end of the oil filter 13a. In other words, the horizontal axis x4, which is the axis of the support shaft 81a that serves as the pivot point at the base end of the top link 51, is set at a position forward of the front vertical wall 8 of the airframe 1. This allows the swing range of the free end of the top link 51 to be a range in which the free end of the top link 51 can move back and forth beyond the vertical line y1 that passes through the horizontal axis x4 that serves as the pivot point at the base end of the top link 51.

[Regarding lift-related operations]
8 and 9, the associated operations of the lifting/lowering mechanism 6, the connecting frame 4, the three-point link mechanism 5, and the power transmission mechanism 7 when the grass cutting device 3 is lifted and lowered will be described.
FIG. 8 shows a schematic diagram of the operation of the grass cutter according to the present invention, and FIG. 9 shows a schematic diagram of the operation of the grass cutter according to the comparative example.

[Operation in the embodiment of the present invention]
In the structure shown in Fig. 8, when the lift arm 60 is in a substantially horizontal lower limit position as shown by a thick solid line so as to position the grass cutting device 3 at the lower limit mowing position, the line segment connecting the horizontal axis x3 of the base end of the lower link 50 and the horizontal axis x5 of the free end is in a substantially horizontal position as shown by a thick solid line. The symbol a0 in the figure indicates the position of the horizontal axis x5 of the free end at this lower limit position. The symbol b0 in the figure indicates the position of the horizontal axis x6, which is the connection point between the free end of the top link 51 and the upper end of the connecting frame 4 at this lower limit position. The positions of the top link 51 and the connecting frame 4 at this lower limit position are also indicated by thick solid lines.

When the lift arm 60 is in the upper limit position as shown by the thin solid line, the line segment connecting the horizontal axis x3 of the base end of the lower link 50 and the horizontal axis x5 of the free end is inclined with the front raised as shown by the thin solid line with the upper end at symbol a4 in the figure. Symbol a4 represents the position of the horizontal axis x5 of the free end at this upper limit position. Symbol b4 in the figure represents the position of the horizontal axis x6, which is the connection point between the free end of the top link 51 and the upper end of the connecting frame 4 at this upper limit position. The positions of the top link 51 and connecting frame 4 at this upper limit position are also shown by thin solid lines.

In FIG. 8, the symbol a1 indicates the position where the horizontal axis x5 on the free end side of the lower link 50 is raised 10 degrees from the lowest position, and the symbol b1 indicates the position of the horizontal axis x6, which is the connection point between the free end of the top link 51 and the upper end of the connecting frame 4 at that point in time.
The symbol b2 in the same figure indicates a state in which the horizontal axis x6, which is the connection point between the free end of the top link 51 and the upper end of the connecting frame 4, is on the vertical line y1 that passes through the horizontal axis x4, which is the pivot point on the base end side of the top link 51, and the symbol a2 indicates the position of the horizontal axis x5 on the free end side of the lower link 50 at that time.
The symbol a3 in FIG. 8 indicates the position where the horizontal axis x5 on the free end side of the lower link 50 is raised by 20 degrees from the lowest position, and the symbol b3 indicates the position of the horizontal axis x6, which is the connection point between the free end of the top link 51 and the upper end of the connecting frame 4 at that point in time.

When the horizontal axis x5 on the free end side of the lower link 50 is in the lower limit position indicated by the symbol a0, and the horizontal axis x6, which is the connection point between the free end of the top link 51 and the upper end of the connecting frame 4, is in the position indicated by the symbol b0, the grass cutting device 3 is in the lower limit cutting position.
When the grass cutting device 3 is positioned in the lowermost cutting position in this manner, the central axes L1, L2, and L3 of the PTO shaft 16, the transmission shaft 17, and the power input shaft 33 of the power transmission mechanism 7 are aligned in a straight line, as shown by the thick dotted line.

When the horizontal axis x5 of the free end of the lower link 50 moves to the upper limit position indicated by a4, the position of the horizontal axis x6, which is the connecting point between the upper end of the connecting frame 4 and the free end of the top link 51, moves to the upper limit position of the swing range of the top link 51 indicated by b4, and the grass cutting device 3 is also located at the upper limit mowing position. In this state, the positional relationships of the central axes L1, L2, L3 of the PTO shaft 16, the transmission shaft 17, and the power input shaft 33 in the power transmission mechanism 7 change as follows, as indicated by thin two-dot chain lines.
In other words, the central axis L2 of the transmission shaft 17 bends at a cross angle α at a cross point p1 relative to the central axis L1 of the PTO shaft 16, and the central axis L3 of the power input shaft 33 bends at a cross angle β at a cross point p2 relative to the central axis L2 of the transmission shaft 17. The cross angles α and β are approximately equal to each other.

Similarly, when the horizontal axis x5 of the free end of the lower link 50 moves sequentially to the positions indicated by the symbols a1, a2, a3, etc., the position of the horizontal axis x6, which is the connection point between the upper end of the connecting frame 4 and the free end of the top link 51, also moves sequentially to the positions indicated by the symbols b1, b2, b3, etc.
Although not shown, when the horizontal axis x5 and the horizontal axis x6 move to any of the positions indicated by symbols a1, a2, a3 and symbols b1, b2, b3, the central axis L2 of the transmission shaft 17 bends a predetermined crossing angle α at the position of the bending center point p1 relative to the central axis L1 of the PTO shaft 16, and the central axis L3 of the power input shaft 33 bends a predetermined crossing angle β at the position of the bending center point p2 relative to the central axis L2 of the transmission shaft 17. The crossing angles α and β at the two bending center points p1 and p2 are approximately equal to each other.

[Operation in Comparative Example]
Next, the operation of the comparative example structure shown in FIG. 9 will be described.
In the structure of the comparative example shown in FIG. 9, the vertical height position of the horizontal axis x4, which is the pivot point on the base end side of the top link 51, is as follows:
It is located at a position approximately as high as the connection point between the upper end of the connecting frame 4, which is in the lowermost position, and the horizontal axis x6 on the free end side of the top link 51.
In other words, the height position of the horizontal axis x4, which is the pivot point at the base end of the top link 51, is not lower than the position indicated by p3, which corresponds to the position of the end (front end) of the power input shaft 33 when the grass mower 3 is in the upper limit mowing position, as in the structure shown in Fig. 8, but is much higher. For this reason, the length from the horizontal axis x4, which is the pivot point on the base end side of the top link 51 itself, to the horizontal axis x6 on the free end side is significantly shorter than in the structure shown in Fig. 8.
Other aspects, such as the length of the lower link 50, the vertical height of the connecting frame 4, and the structure of the power transmission mechanism 7, are similar to those of the structure shown in FIG.

Even in the structure shown in FIG. 9, when the lift arm 60 is in the lower limit position shown by the thick solid line so as to position the grass cutting device 3 at the lower limit cutting position, the line segment connecting the horizontal axis x3 of the base end of the lower link 50 and the horizontal axis x5 of the free end is in a substantially horizontal position as shown by the thick solid line. The symbol a0 in the figure represents the position of the horizontal axis x5 of the free end at this lower limit position. Also, the symbol b0 in the figure represents the position of the horizontal axis x6, which is the connection point between the free end of the top link 51 and the upper end of the connecting frame 4 at this lower limit position. The positions of the top link 51 and the connecting frame 4 at this lower limit position are also shown by thick solid lines.

In the structure of this comparative example, when the lift arm 60 is in the lowermost position so as to position the grass cutting device 3 at the lowermost mowing position, and the lower link 50 extending from the horizontal axis x3 of the base end of the lower link 50 to the horizontal axis x5 of the free end of the lower link 50 is in a substantially horizontal position, the central axes L1, L2, and L3 of the PTO shaft 16, the transmission shaft 17, and the power input shaft 33 of the power transmission mechanism 7 are aligned in a straight line as shown by the thick two-dot chain line, similar to the structure shown in FIG. 8.

In FIG. 9, the symbol a1 indicates the position where the horizontal axis x5 on the free end side of the lower link 50 is raised 10 degrees from the lowest position, and the symbol b1 indicates the position of the horizontal axis x6, which is the connection point between the free end of the top link 51 and the upper end of the connecting frame 4 at that point in time.
In the same figure, symbol a2 indicates the position where the horizontal axis x5 on the free end side of the lower link 50 is raised 20 degrees from the lower limit position, and symbol b2 indicates the position of the horizontal axis x6, which is the connection point between the free end of the top link 51 and the upper end of the connecting frame 4 at that time.
The symbol b3 in the same figure indicates a state in which the horizontal axis x6, which is the connection point between the free end of the top link 51 and the upper end of the connecting frame 4, is on the vertical line y1 that passes through the horizontal axis x4, which is the pivot point on the base end side of the top link 51, and the symbol a3 indicates the position of the horizontal axis x5 on the free end side of the lower link 50 at that point in time.

In the figure, the reference symbol b4 indicates the state in which the horizontal axis x6, which is the connection point between the free end of the top link 51 and the upper end of the connecting frame 4, has passed the vertical line y1 that passes through the horizontal axis x4, which is the pivot point on the base end side of the top link 51, and has moved rearward of the vertical line y1 (towards the aircraft body 1), and the reference symbol a4 indicates the position of the horizontal axis x5 on the free end side of the lower link 50 at that point in time.

The symbol b5 in the figure indicates a state in which the horizontal axis x6, which is the connection point between the free end of the top link 51 and the upper end of the connecting frame 4, has passed the vertical line y1 that passes through the horizontal axis x4, which is the pivot point on the base end side of the top link 51, and has moved further rearward (towards the aircraft body 1) than the vertical line y1 and the position of symbol b4. The symbol a5 indicates the position of the horizontal axis x5 on the free end side of the lower link 50 at that point in time.

Reference symbol b6 in the figure indicates a state in which the horizontal axis x6, which is the connection point between the free end of the top link 51 and the upper end of the connecting frame 4, has passed the vertical line y1 passing through the horizontal axis x4, which is the pivot point on the base end side of the top link 51, and has moved further rearward (toward the aircraft body 1) than the vertical line y1 and the positions of reference symbols b4 and b5. Reference symbol a6 indicates the position of the horizontal axis x5 on the free end side of the lower link 50 at that time.
The position of this symbol b6 is located on a virtual line Lx that is located on the opposite side (machine body 1 side) of the vertical line y1 at an angle θ2 that is approximately the same as the angle θ1 that the line Ld connecting the base end and free end of the top link 51 makes with the vertical line y1 when the grass cutting device 3 is in the lowermost mowing position.

When the horizontal axis x6, which is the connection point between the free end of the top link 51 and the upper end of the connecting frame 4, is at the position shown by the symbols b5 and b6 above, in the drawing, the connecting frame 4 has moved past the position of the horizontal axis x4, which is the pivot point of the top link 51, to the rear side (towards the aircraft body 1).
The symbols a5 and a6, which indicate the position of the horizontal axis x5 on the free end side of the lower link 50, corresponding to the positions indicated by symbols b5 and b6, move in a direction returning closer to the position of the horizontal axis x5 of the free end at the lower limit position, indicated by symbol a0, than the position indicated by symbol b4 in the drawing.

However, the movement of the horizontal axis x5 position on the free end of the lower link 50 in the return direction approaching the lower limit position, which is related to the positions of symbols a5 and a6, is a movement in the opposite direction to the lifting direction by the lift arm 60. Therefore, the movement of the lift arm 60 in the lifting direction and the movement of the lower link 50 in the downward direction by the top link 51 and connecting frame 4 act in opposite directions and cancel each other out.

In other words, in the area where the symbols a5 and a6 are present on the drawing, the movement of the lift arm 60, the lower link 50, the top link 51 and the connecting frame 4 are all stopped, so in reality they cannot reach the positions of symbols a5 and a6.
The position that the horizontal axis x6 can reach without stopping the above movement is the position indicated by the symbol b4. However, even at the position indicated by the symbol b4, the top link 51 and the connecting frame 4 are too close in the swinging direction, so in reality, the top link 51 abuts against the connecting frame 4 and cannot approach that close. As a result, the position indicated by the symbol b3 on the vertical line y1 is the achievable position at which the grass cutting device 3 can be lifted as high as possible in this structure, and this position corresponds to the upper limit mowing position.

In the power transmission mechanism 7 in the structure of this comparative example, when the lift arm 60 is in the lowermost position, as described above, the central axes L1, L2, L3 of the PTO shaft 16, the transmission shaft 17, and the power input shaft 33 of the power transmission mechanism 7 are aligned in a straight line.
When the horizontal axis x5 of the free end of the lower link 50 moves to the position indicated by the symbol a3, the position of the horizontal axis x6, which is the connection point between the upper end of the connecting frame 4 and the free end of the top link 51, moves to the substantial upper limit position of the swing range of the top link 51 indicated by the symbol b3, and the grass cutting device 3 is positioned at a height equivalent to the upper limit cutting position.
When this grass cutting device 3 is located in the upper limit cutting position, the central axis L2 of the transmission shaft 17 bends at a cross angle α relative to the central axis L1 of the PTO shaft 16 at a bending center point p1, and the central axis L3 of the power input shaft 33 bends at a cross angle β relative to the central axis L2 of the transmission shaft 17 at a bending center point p2.
Comparing the crossing angle α with the crossing angle β, the crossing angle α at the position of the refraction center point p1 is much larger than the crossing angle β at the position of the refraction center point p2.
For this reason, the relatively large non-uniform rotation speed that occurs between the PTO shaft 16 and the transmission shaft 17 cannot be eliminated by the relatively small cross angle β between the transmission shaft 17 and the power input shaft 33, and power is transmitted with the non-uniform rotation speed corresponding to the angle difference remaining.

Similarly, when the horizontal axis x5 of the free end of the lower link 50 moves sequentially to the positions indicated by the symbols a1, a2, etc., the position of the horizontal axis x6, which is the connection point between the upper end of the connecting frame 4 and the free end of the top link 51, also moves sequentially to the positions indicated by the symbols b1, b2, etc.
Although not shown in the figure, when the above-mentioned horizontal axis x5 and horizontal axis x6 move to any of the positions indicated by symbols a1, a2, and symbols b1, b2, the central axis L2 of the transmission shaft 17 bends by a predetermined crossing angle α at the position of the bending center point p1 relative to the central axis L1 of the PTO shaft 16, and the central axis L3 of the power input shaft 33 bends by a predetermined crossing angle β at the position of the bending center point p2 relative to the central axis L2 of the transmission shaft 17.
The difference between the crossing angle α and the crossing angle β at the two bending center points p1 and p2 is equal to or greater than the case where the horizontal axis x5 of the free end of the lower link 50 is located at the position indicated by the symbol a3, and the crossing angle α at the bending center point p1 is far greater than the crossing angle β at the bending center point p2. Therefore, power is transmitted with non-uniform rotation according to the angle difference remaining.

[Another embodiment 1]
In the above embodiment, the top link 51 is configured as a straight rod-shaped member connecting the horizontal axis x4 of the base end and the horizontal axis x6 of the free end, but the present invention is not limited to this structure. For example, as shown in Fig. 10, the side closer to the base end may be configured as a curved rod-shaped portion 51a (corresponding to the curved portion). This curved rod-shaped portion 51a is intended to easily avoid contact with the top link 51 even when a member with a larger protruding amount is used as a member provided on the aircraft body 1 side, such as the oil filter 13a.
The other configurations may be the same as those of the above-described embodiment.

[Another embodiment 2]
In the above embodiment, a structure in which the grass cutting device 3 is located in front of the machine body 1 has been exemplified, but a structure in which the grass cutting device 3 is located in the rear of the machine body 1 may also be used.
The other configurations may be the same as those of the above-described embodiment.

[Another embodiment 3]
In the above-described embodiment, an example was given of a structure in which the upper limit of the height range in which mowing work can be performed by the grass cutting device 3 coincides with the upper limit of the lifting and lowering adjustment range by the lifting and lowering operating mechanism 6 and the three-point link mechanism 5, but this structure is not necessarily limited to this.
For example, the mechanical upper limit of the lifting adjustment range by the lifting operating mechanism 6 and the three-point link mechanism 5 may be set at a position higher than the upper limit cutting position, which is set as the upper limit of the height range in which mowing work can be performed by the grass cutting device 3, so that the grass cutting device 3 can be lifted to a position higher than the upper limit cutting position without performing grass cutting work.
The other configurations may be the same as those of the above-described embodiment.

[Alternative embodiment 4]
The travelling device is not limited to a crawler travelling device, but may be a wheel travelling device.
The other configurations may be the same as those of the above-described embodiment.

[Alternative embodiment 5]
The grass cutting device 3 is not limited to a flail mower, and may be of a structure equipped with a blade that rotates around a vertical axis.
The other configurations may be the same as those of the above-described embodiment.

[Alternative embodiment 6]
In the above embodiment, the engine 12 is used as the driving source mounted on the prime mover 11, but the present invention is not limited to this. For example, an electric motor (not shown) may be used as the driving source.

The present invention can be applied not only to lawnmowers that can be remotely controlled by a radio control device, but also to riding lawnmowers that can be operated by an operator.

REFERENCE SIGNS LIST 1 Machine body 2 Traveling device 3 Grass cutting device 4 Connecting frame 5 Three-point link mechanism 6 Lifting operation mechanism 7 Power transmission mechanism 8 Vertical wall 16 Power take-off shaft 17 Transmission shaft 18 Universal joint 32 Knife blade 33 Power input shaft 50 Lower link 51 Top link 51a Curved portion 60 Lift arm 61 Lift rod 62 Lifting cylinder
10C bracket L1 Center axis L2 Center axis L3 Center axis Ld Line segment Lu Line segment y1 Vertical line x1 Horizontal axis x3 Connection point x4 Connection point α Intersection angle β Intersection angle θ1 Angle θ2 Angle

Claims (9)

Right and left running gears supporting the aircraft body;
A connecting frame provided at one end of the aircraft in the front-rear direction;
A grass cutting device detachably supported on the connecting frame;
A power transmission mechanism that transmits power from the machine body to the grass mowing device is provided,
the connecting frame is connected to the airframe via a three-point link mechanism having a pair of left and right lower links and a top link attached to the airframe so as to be able to swing up and down around a horizontal axis along the left-right direction, and a lifting and lowering mechanism that lifts and lowers the three-point link mechanism;
The power transmission mechanism is supported across the machine body and the connecting frame, and the power transmission mechanism is provided with a power take-off shaft provided at the one end of the machine body, a power input shaft that transmits power to the grass cutting device supported by the connecting frame, and a transmission shaft that connects the power take-off shaft and the power input shaft via universal joints provided at both ends,
the lifting mechanism includes a lift arm whose base end is pivotally supported on the vehicle body, a lift rod that connects a free end of the lift arm to the lower link, and a lifting cylinder that swings the lift arm up and down;
The lifting mechanism has a mowing lifting operation range from a lower limit mowing position where the mowing device performs mowing work at a minimum ground clearance near the ground to an upper limit mowing position where the mowing device performs mowing work at a position higher than the lower limit mowing position,
The three-point link mechanism is configured to be swingable such that, with respect to a vertical line passing through a pivot point at the base end of the top link connected to the machine body side, when the grass mowing device is in the lower limit mowing position, the free end of the top link is located away from the machine body than the vertical line, and when the grass mowing device is in the upper limit mowing position, the free end of the top link is swingable so as to cross the vertical line and approach the machine body side,
A pivot point at a base end of the top link connected to the machine body is set at a position lower than the uppermost position of the power input shaft of the power transmission mechanism in a posture raised to the upper limit mowing position and higher than the transmission shaft ,
The lifting cylinder has a lower end connected to a bracket that protrudes from a vertical wall at one end of the body toward the side where the connecting frame is located, and an upper end connected to a position closer to the base end of the lift arm than the connection point of the lift rod to the lift arm . Right and left running gears supporting the aircraft body;
A connecting frame provided at one end of the aircraft in the front-rear direction;
A grass cutting device detachably supported on the connecting frame;
A power transmission mechanism that transmits power from the machine body to the grass mowing device is provided,
the connecting frame is connected to the airframe via a three-point link mechanism having a pair of left and right lower links and a top link attached to the airframe so as to be able to swing up and down around a horizontal axis along the left-right direction, and a lifting and lowering mechanism that lifts and lowers the three-point link mechanism;
The power transmission mechanism is supported across the machine body and the connecting frame, and the power transmission mechanism is provided with a power take-off shaft provided at the one end of the machine body, a power input shaft that transmits power to the grass cutting device supported by the connecting frame, and a transmission shaft that connects the power take-off shaft and the power input shaft via universal joints provided at both ends,
the lifting mechanism includes a lift arm whose base end is pivotally supported on the vehicle body, a lift rod that connects a free end of the lift arm to the lower link, and a lifting cylinder that swings the lift arm up and down;
The lifting mechanism has a mowing lifting operation range that ranges from a lower limit mowing position where the mowing device performs mowing work at a minimum ground clearance close to the ground to an upper limit mowing position where the mowing device performs mowing work at a position higher than the lower limit mowing position,
The three-point link mechanism is configured to be swingable such that, with respect to a vertical line passing through a pivot point at the base end of the top link connected to the machine body side, when the grass mowing device is in the lower limit mowing position, the free end of the top link is located away from the machine body than the vertical line, and when the grass mowing device is in the upper limit mowing position, the free end of the top link is swingable so as to cross the vertical line and approach the machine body side,
A pivot point at a base end of the top link connected to the machine body side is set at a position lower than the uppermost position of the power input shaft of the power transmission mechanism in a posture raised to the upper limit mowing position and higher than the transmission shaft ,
The left and right lift arms are connected to each other at their base ends so that they can swing together, and the grass cutter is configured so that either the left or right lift arm is driven and raised and lowered by a single lifting cylinder to swing the left and right arms simultaneously . Right and left running gears supporting the aircraft body;
A connecting frame provided at one end of the aircraft in the front-rear direction;
A grass cutting device detachably supported on the connecting frame;
A power transmission mechanism that transmits power from the machine body to the grass mowing device is provided,
the connecting frame is connected to the airframe via a three-point link mechanism having a pair of left and right lower links and a top link attached to the airframe so as to be able to swing up and down around a horizontal axis along the left-right direction, and a lifting and lowering mechanism that lifts and lowers the three-point link mechanism;
The power transmission mechanism is supported across the machine body and the connecting frame, and the power transmission mechanism is provided with a power take-off shaft provided at the one end of the machine body, a power input shaft that transmits power to the grass cutting device supported by the connecting frame, and a transmission shaft that connects the power take-off shaft and the power input shaft via universal joints provided at both ends,
the lifting mechanism includes a lift arm whose base end is pivotally supported on the vehicle body, a lift rod that connects a free end of the lift arm to the lower link, and a lifting cylinder that swings the lift arm up and down;
The lifting mechanism has a mowing lifting operation range from a lower limit mowing position where the mowing device performs mowing work at a minimum ground clearance near the ground to an upper limit mowing position where the mowing device performs mowing work at a position higher than the lower limit mowing position,
The three-point link mechanism is configured to be swingable such that, with respect to a vertical line passing through a pivot point at the base end of the top link connected to the machine body side, when the grass mowing device is in the lower limit mowing position, the free end of the top link is located away from the machine body than the vertical line, and when the grass mowing device is in the upper limit mowing position, the free end of the top link is swingable so as to cross the vertical line and approach the machine body side,
A pivot point at a base end of the top link connected to the machine body is set at a position lower than the uppermost position of the power input shaft of the power transmission mechanism in a posture raised to the upper limit mowing position and higher than the transmission shaft ,
The top link has a curved portion formed in a portion of its length from the base end to the free end to avoid interference with other objects provided on the machine body . The power transmission mechanism is configured such that the central axis of the power take-off shaft connected to the transmission shaft and the central axis of the power input shaft are linearly connected at the lower limit mowing position, and that in the mowing lifting operating range extending from the lower limit mowing position to the upper limit mowing position, the crossing angle formed by the central axis of the power take-off shaft with respect to the central axis of the transmission shaft and the crossing angle formed by the central axis of the power input shaft with respect to the central axis of the transmission shaft are identical or nearly identical to each other . The grass mower according to any one of claims 1 to 4, wherein the universal joint that flexibly connects the transmission shaft and the power input shaft is provided at a position closer to a connection point of the lower link to the body than to a connection point between the lower link and the connecting frame. An angle formed by a line segment connecting the base end and the free end of the top link at the lower limit mowing position with respect to a vertical line passing through a pivot point at the base end of the top link;
A grass mower according to any one of claims 1 to 5, wherein an angle formed by a line segment connecting the base end and free end of the top link at the upper limit mowing position and a vertical line passing through a pivot point at the base end of the top link is set to be approximately the same. The grass mower according to any one of claims 1 to 6, wherein the connection point to the body at the base end of the top link is located further toward the connecting frame than the connection point of the lower link to the body. The grass mower according to any one of claims 1 to 7 , wherein the left and right lift arms are arranged closer to the center of the machine body in the left-right direction than the left and right lower links. The grass cutter according to any one of claims 1 to 8 , wherein the grass cutter is a flail mower equipped with a knife blade that is driven to rotate about a horizontal axis along the left-right direction.

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