JPH0813658B2 - Steering device for work vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides a steering clutch that is biased to return to the entry side in each of transmission systems for a pair of traveling devices.
A steering hydraulic cylinder for operating each of these steering clutches, two states in which pressure oil is selectively supplied to the hydraulic cylinder, and a neutral state in which the pressure oil is discharged from these hydraulic cylinders are freely switchable. Based on an electromagnetically operated three-position switching valve, an electromagnetically operated two-position switching valve that is switchable between a state in which pressure oil is discharged from each of the hydraulic cylinders and a state in which drainage is stopped, and a clutch disengagement operation command. , A control means for switching the three-position switching valve to a state in which pressure oil is supplied to a commanded hydraulic cylinder, and for intermittently switching the two-position switching valve between an oil discharge state and an oil discharge stop state. The present invention relates to a steering device for a work vehicle provided.

[Conventional technology]

Some work vehicles, such as combine harvesters, are configured so that one of the left and right steering clutches is intermittently disengaged to slow down the drive speed of one of the left and right traveling devices to change the direction of the vehicle body. .

Generally, as shown in FIG. 6, an electromagnetically operated three-position switching valve has a delay time from when power is supplied to switch to a pressure oil supply state until the pressure actually starts to rise, and a neutral state. There is a long delay time from when the power is turned on for switching operation to when the pressure actually starts to drop. On the other hand, the two-position switching valve (for example, poppet valve) is switched to the oil drain stop state and the delay time from the time when power is supplied to switch to the oil drain state until the pressure oil is actually discharged. There is a short delay time from when electricity is supplied for operation to when discharge is actually stopped. In other words, the three-position switching valve has a long delay time and thus is not suitable for intermittent switching operation, and the two-position switching valve has a short delay time and is therefore suitable for intermittent switching operation.

From the above, in the conventional steering apparatus for a work vehicle, for example, as disclosed in JP-A-62-163871,
When either one of the clutch disengagement operation commands is received, the three-position switching valve is switched to the pressure oil supply state to the instructed one, and then the two-position switching valve is set to the drainage state and the drainage stop state. The instructed clutch is intermittently disengaged by intermittently performing switching operation at time intervals of.

[Problems to be Solved by the Invention]

In order to swiftly and smoothly change the direction of the vehicle body, it is necessary to shorten the disengagement time and the engagement time of the steering clutch. For that purpose, it is necessary to switch the two-position switching valve in a short time. Switching the two-position switching valve in a short time is relatively easy because the normal cycle may be shortened. However, there is a short delay time from the switching operation of the two-position switching valve to the oil discharge stop state until the hydraulic cylinder reaches the stroke end on the clutch disengagement side. There are variations due to fluctuations. Therefore, even if the two-position switching valve is switched to the oil drainage stopped state, it may be switched to the oil drained state without waiting for the hydraulic cylinder to reach the stroke end on the clutch disengagement side.

In short, if the two-position switching valve is switched in a short time, the instructed steering clutch may not be sufficiently disengaged, resulting in a defective clutch state, which may prevent a quick and smooth direction change. is there.

The present invention has been made in view of such an actual situation, and an object thereof is to enable quick and smooth direction change without causing the above-mentioned clutch failure.

[Means for solving the problem]

In the steering apparatus for a work vehicle according to the present invention, a sensor that detects whether or not the hydraulic cylinder has reached the stroke end on the clutch disengagement side each time the two-position switching valve is switched to the oil drain stop state. The control means is provided
When the sensor detects that the hydraulic cylinder has reached the stroke end, the two-position switching valve is switched to the oil draining state for a set time, and then the oil draining stop state is set after switching to the oil draining state for the set time. The first feature is that the switching operation is intermittently performed in the switching state.

The second feature is that the sensor is a pressure sensor that detects the hydraulic pressure supplied to the hydraulic cylinder.

[Work]

According to the first feature, when one of the clutch disengagement operation commands is received, the control means switches the three-position switching valve to the pressure oil supply state to the instructed one, and the instructed one of the hydraulic pressures. Supply pressure oil to the cylinder. When the pressure oil supply is started, the hydraulic cylinder operates and the steering clutch is disengaged. Shortly thereafter, the hydraulic cylinder reaches the end of the stroke, and when it is detected by the sensor, the control means
The two-position switching valve is switched to the oil draining state, and this oil draining state is maintained for a set time. Then, when the set time has elapsed, the control means switches the two-position switching valve to the oil discharge stop state, and supplies the pressure oil again to the designated hydraulic cylinder. The switching operation of the two-position switching valve between the oil discharge state and the oil discharge stop state is repeatedly performed until the clutch disengagement operation command is released. By the way, the set time can be arbitrarily changed.

The second feature identifies the sensor in the first feature. Whether or not the hydraulic cylinder has reached the stroke end is detected by the hydraulic pressure supplied to the hydraulic cylinder. In this case, the pressure detected by the sensor is set to be higher than the pressure at which the steering clutch is reliably entered and operated.

〔The invention's effect〕

According to the first feature, since the two-position switching valve is immediately switched to the oil draining state when the steering clutch is reliably disengaged, the steering clutch disengagement time can be made extremely short. , It will be possible to change direction more quickly and smoothly than before.

In particular, since the switching operation is intermittently performed in the state of switching to the oil draining state over a preset set time, even if the steering clutch is rapidly switched to the disengaged state depending on the driving state of the hydraulic pump, it is slowly disengaged. Even if you switch to
The steering clutch is operated in the engaged state for a set time, and the faster the steering clutch is switched to the disengaged state, the shorter the time interval in which the steering clutch is operated in the engaged state becomes. Since the number of times the on-and-off clutch is turned on and off per unit time is increased, quick and smooth direction change can be performed according to the driving state of the hydraulic pump.

The second feature provides the most suitable sensor for implementing the present invention. In short, when it is attempted to detect whether or not the hydraulic cylinder has reached the stroke end by a mechanical operation, it must be detected for each hydraulic cylinder, and at least two sensors must be provided. However, if it is a pressure sensor, if it is between the hydraulic pump and the 3-position switching valve or the 2-position switching valve,
Only one needs to be provided.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 5, the combine as a working vehicle is
Mowing part (2) of the rice field, wheat, etc. in the field is cut and raised, and the cutting stem (2) is transferred to the feed chain (1) by changing the posture to a sideways posture while transporting the cutting culm.
Equipped with a threshing device (3) for threshing culms sandwiched and conveyed by the feed chain (1) to select and collect grains, and a pair of left and right crawler type traveling devices (4L), (4R) There is.

The attachment frames (6) and (6) for the weeding tools (5L) and (5R) provided at the left and right ends on the tip side of the mowing section (2) respectively have a lateral direction of the body with respect to the stem (H). The scanning sensors (S ₁ ) and (S ₂ ) are provided to detect the deviation amount of. As shown in FIG. 3 and FIG. 4, these scanning sensors (S ₁ ) and (S ₂ ) are forward of the fuselage at the root of the stem (H) introduced into the cutting section (2). A sensor bar (7) that abuts in a biased state and rotates an angle corresponding to the abutting position toward the rear side of the machine body, and a potentiometer (R) that detects a rotation angle of the sensor bar (7). The control parameter for controlling the vehicle body (V) to automatically travel along the stalk (H) during the cutting operation is detected and provided to the control device (C).

In addition, since the stem culm (H) planted in the field contacts the sensor bar (7) intermittently, the output signal of the potentiometer (R) changes intermittently. The control device (C) is configured by using a microcomputer, and after performing signal processing such as averaging the output signal of the potentiometer (R) and detecting the maximum value per unit time, The amount of lateral displacement is detected.

A pair of left and right steering clutches (12L) and (12R) that are biased toward the entrance side are provided in each transmission system for the left and right crawler steering devices (4L) and (4R), and a pair of steering clutches Operate the hydraulic cylinders (13L) and (13R) so that the steering clutches (12L) and (12R) are disengaged by extension operation.
Each steering clutch (12L), (12R) is linked to form a steering device.

As shown in Fig. 2, steering clutches (12L), (12R)
And a pair of hydraulic cylinders (13L) and (13R) are linked by a swing arm (15) pivotally supported by each steering clutch shaft (14) to select one of the hydraulic cylinders (13L) and (13R). Two states for supplying pressure oil and their hydraulic cylinders (13
An electromagnetically operated three-position switching valve (17) is provided which can be switched to a neutral state in which pressure oil is discharged from L) and (13R) and which is urged to return to the neutral state by a spring (16). In addition, the pressure oil supply pressure to the hydraulic cylinders (13L) and (13R) can be switched to a state where the pressure oil supply pressure is reduced (drained state), and the spring (18) returns to the non-depressurized state (drained oil stopped state) side. An energized electromagnetically operated two-position switching valve (19) is provided. The 2-position switching valve (19) is a poppet valve capable of high-speed response. In addition, the hydraulic cylinder (13
A pressure sensor (20) for detecting the pressure of the pressure oil supplied to L) and (13R) is provided.

When the three-position switching valve (17) is switched to bring the pressure supply state from the neutral state to the one side, the swing arm (15) is moved along with the extension of the hydraulic cylinder (13L or 13R) to which the pressure is supplied. It swings and one of the left and right steering clutches (12L or 12L
R) is turned off, and when the pressure supply state is changed to the neutral state, the swing arm (15) swings in the opposite direction as the left or right hydraulic cylinder (13L or 13R) contracts, and the cut state is controlled. The directional clutch (12L or 12R) will be engaged and operated. Even if the three-position switching valve (17) is maintained on the pressure supply side, if the two-position switching valve (19) is switched to a depressurized state, the expanded hydraulic cylinder (13L or 13R) contracts and the cutoff state is turned off. The steering clutch (12L or 12R) in the state will be turned on and operated.

The three-position switching valve (17), the two-position switching valve (19), and the pressure sensor (20) are all connected to the control device (C). When turning on or off one of the steering clutches (12L) and (12R), the three-position switching valves (17) and 2 are operated based on the operation command of the clutch and the information from the pressure sensor (20). A steering device for switching the position switching valve (19) is configured.

In the above steering apparatus, as shown in FIG. 1, when a left or right clutch disengagement operation command is given, the control device (C) disengages the three-position switching valve (17). Switch to the side that supplies pressure oil to the hydraulic cylinder (13L or 13R) on that side, and operate the steering clutch (12L or 12R). When the pressure sensor (20) detects that the hydraulic pressure further rises and reaches the set pressure (the pressure at which the hydraulic cylinder extends and the steering clutch is reliably disengaged), the two-position switching valve (19 ) Is immediately switched to the decompression side, and the steering clutch (12L or 12R) is turned on and operated. After that, when the set time (T) elapses, the 2-position switching valve (19)
Steering clutch (12L or 12R)
Turn off again.

The hydraulic pressure rises again by returning the two-position switching valve (19) to the non-decompression side, but when the pressure sensor (20) detects that the set pressure has been reached, the two-position switching valve (19)
Is switched to the depressurizing side in the same manner as above. That is, the two-position switching valve (19) is intermittently switched between the depressurized state and the non-depressurized state unless the clutch disengagement operation command is released.

When one of the left and right clutch engagement operation commands is given, the control device (C) restores the three-position switching valve (17) to the neutral state and simultaneously restores the two-position switching valve (19) to the non-depressurized state side. Then, operate the steering clutch (12L or 12R).

When the steering clutches (12) and (12R) are intermittently disengaged in this manner, the driving force is intermittently interrupted and the driving speeds of the traveling devices (4L) and (4R) become slower. If only one becomes slower, the aircraft (V) is turned. In this combine, the left and right scanning sensors (S ₁ ),
Based on the control parameter provided from (S ₂ ), during the mowing operation, in order to maintain the lateral displacement of the mowing part (2) with respect to the stalks (H) in the aircraft lateral direction at an appropriate position, It is equipped with an automatic steering control function that automatically changes the direction of travel.

That is, when the amount of deviation of the cutting unit (2) in the right lateral direction with respect to the stem (H) is large, a left clutch disengagement operation command is given to slow down the traveling speed of the left traveling device (4L), Turn the aircraft (V) slightly to the left. When the amount of deviation in the left lateral direction is large, a right clutch disengagement operation command is given to slow the traveling speed of the right traveling device (4R), and the vehicle body (V) is slightly turned to the left. Of. By this automatic steering control, the direction of the machine body (V) is changed so that the mowing part (2) is always maintained at an appropriate position with respect to the stem (H).

[Another embodiment]

In the above embodiment, only the steering clutches (12L) and (12R) are turned on and off by expanding and contracting the hydraulic cylinders (13L) and (13R), but the traveling devices (4L) are attached to the hydraulic cylinders (13L) and (13R). ), (4R) brakes are interlocked, and the hydraulic cylinders (13L), (13R) expand and contract to drive the traveling devices (4L), (4
R) may be braked.

In the above-described embodiment, whether or not the hydraulic cylinders (13L) and (13R) have reached the stroke end is hydraulically detected. However, the hydraulic cylinders (13L) and (13R) and the swing arm (15R) are not detected. ) Or other mechanical movement. For example, a limit switch may be provided near the swing end of the swing arm (15) for detection.

In the above embodiment, the case where the present invention is applied to a combine is described as an example, but the present invention can also be applied to another work vehicle such as a straw harvester.

It should be noted that reference numerals are added to the claims for convenience of comparison with the drawings, but the present invention is not limited to the structures of the accompanying drawings by the entry.

[Brief description of drawings]

The drawings show an embodiment of a steering apparatus for a work vehicle according to the present invention, and FIG. 1 is a timing chart showing a switching operation of a 3-position switching valve and a 2-position switching valve and a relationship between a pressure sensor and a hydraulic pressure.
FIG. 4 is a hydraulic circuit diagram, FIG. 3 is a schematic diagram showing a control configuration, and FIG.
FIG. 5 is a schematic plan view showing the mounting portion of the copying sensor, FIG. 5 is a side view of the combine, and FIG. 6 is a timing chart showing the relationship between the switching operation of the 3-position switching valve and the hydraulic pressure. (C) ... control means, (4L), (4R) ... traveling device,
(12L), (12R) ... Steering clutch, (13L), (13R)
...... Hydraulic cylinder, (17) …… 3-position switching valve, (19)…
… 2 position switching valve, (20) …… Sensor.

Claims (2)

[Claims] 1. A steering clutch (12L), (12R), which is biased toward the entry side, is provided in each of transmission systems for a pair of left and right traveling devices (4L), (4R). Steering hydraulic cylinders (13L) and (13R) for operating (12L) and (12R), respectively, and two states for selectively supplying hydraulic oil to the hydraulic cylinders (13L) and (13R). And these hydraulic cylinders (13L), (13
R) is a solenoid operated three-position switching valve (17) that can be switched to a neutral state in which pressure oil is discharged, and a state in which pressure oil is discharged from each of the hydraulic cylinders (13L) and (13R) and discharge oil. An electromagnetically operated two-position switching valve (19) that can be switched to a stopped state, and the hydraulic cylinders (13L), (13R) commanded by the three-position switching valve (17) based on a clutch disengagement operation command. )
Of a work vehicle provided with a control means (C) for switching to a state in which pressure oil is supplied to the engine and for intermittently switching the two-position switching valve (19) between an oil discharge state and an oil discharge stop state. In the steering device, whether or not the hydraulic cylinders (13L) and (13R) reach the stroke end on the clutch disengagement side each time the two-position switching valve (19) is switched to the oil discharge stopped state. Is provided with a sensor (20) for detecting that the control means (C) detects that the sensor (20) has reached the stroke end of the hydraulic cylinders (13L), (13R). The valve (19) is switched to the oil draining state for a set time, and after switching to the oil draining state for the set time, after switching to the oil drain stop state, the switching operation of the work vehicle is configured to be intermittently performed. Steering device. 2. The steering apparatus for a work vehicle according to claim 1, wherein the sensor (20) is a pressure sensor for detecting a hydraulic pressure supplied to the hydraulic cylinders (13L), (13R).