JPH0365121B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic control device for operating a hydraulic device for lifting and lowering a working machine of a tractor.

A tractor's hydraulic system is equipped with a hydraulic control device that raises and lowers the towed work equipment, maintains a constant height, and performs so-called position control and draft control to maintain constant traction resistance. There is.

Generally, a hydraulic control device has a valve mechanism that supplies and discharges hydraulic oil to the hydraulic device, and a position lever and a draft lever that switch the valve mechanism to neutral, ascending, and descending states via a link mechanism. The link mechanism is actuated by the rotation of both levers and the movement of a member that detects an increase in the traction resistance of the work equipment, and the pilot spool of the valve mechanism is moved from the neutral position by rotation of the spool restraining lever of the link mechanism. The pilot spool is slid to the raised or lowered position, and a return spring is used to return the pilot spool from the raised position to the neutral position.

By the way, in rotary tillage work, for example, the same field may be tilled two or three times to achieve a more complete tillage state. In that case, during the second or third plowing operation, the impact applied to the work equipment will be extremely small.
If the working machine is slightly raised in such a state, the pilot spool will stop at an intermediate position between the neutral position and the raised (discharge) position, and will not return completely to the neutral position.

This is mainly because there is play in the moving parts of the link mechanism due to manufacturing errors, and frictional resistance is generated due to the sliding contact parts, and this frictional resistance maintains a static balance with the return spring of the pilot spool. This is thought to be due to If the pilot spool does not return completely to the neutral position in this way, the oil passage that sends oil to the hydraulic cylinder will remain slightly open, causing the hydraulic pressure in the valve mechanism to rise incompletely, causing the pump and valve mechanism to fail. Damage may occur.

In view of these problems, the present invention uses an impact to disrupt the static balance between the restoring force of the spool return spring and the frictional resistance of the link mechanism, so that the pilot spool always returns completely to the neutral position. The object of the present invention is to provide a hydraulic control device for a tractor.

A feature of the present invention for achieving this object is that in order to operate the valve mechanism 31 for controlling the hydraulic device 11, the link mechanism 73 via the spool holding lever 34
The pilot spool 32, which is in elastic contact with the pilot spool 32, is pushed back by the spring 46, and the spool holding lever 34 is moved in conjunction with the rise of the lift arm 17.
In a hydraulic control system for a tractor in which the pilot spool 32 is returned to the neutral position by a return spring 46 when the pilot spool 32 swings back, the position lever 51 is attached to a position lever shaft 57 so as to be integrally rotatable. The brake lever 51B includes a swinging lever 51A that is rotated upwardly, and a brake lever 51B that rotates with the swinging lever 51A through play α when the swinging lever 51A is rotated upward.
A rotational friction resistance means is provided between the member supporting the position lever shaft 57, and a rotational friction resistance means is provided between the swinging lever 51A and the brake lever 51B, and when the swinging lever 51A is released from the swinging operation, Pressing member 9 that returns and swings the movable lever 51A by the amount of play α
5 and a collision portion 97 for return collision.

Embodiments of the present invention will be described below based on the drawings.

In Figs. 1 to 3 and 5, reference numeral 1 denotes a load spring mounting base, which is attached to a rear solid member 2 of the tractor body. Reference numeral 3 designates a load spring arm, which hooks the upper link of a working machine (not shown) and senses the compression reaction force applied to the upper link. move. 4
is a draft cam lever, which is pivotally supported at a proper position on the hydraulic cylinder case 5 by a support shaft 6. A draft cam link 7 connects the load spring arm 3 and the draft cam lever 4 together. Reference numeral 8 denotes a draft cam, which is pivotally supported on the support shaft 6 and inside the case 5.

A hydraulic cylinder 10 is housed in a hydraulic cylinder case 5, into which a hydraulic piston 12 is slidably inserted. A hydraulic rod 13 transmits the movement of the hydraulic piston 12 to the hydraulic arm 15 via a hydraulic arm pin 14. 16
is a hydraulic arm shaft, which is inserted and supported by a spline or the like to rotate together with the hydraulic arm 15, and at both ends of the coaxial shaft 16 and outside the hydraulic cylinder case 5, a lift arm 17 is fixed to rotate together with the hydraulic arm 15. These components constitute a hydraulic system 11.

Reference numeral 25 denotes a position cam plate, which is fixed to one side of the hydraulic arm 15 via bolts 26, and has a position cam 27 on its circumferential surface.
is formed. In FIGS. 2 and 6, reference numeral 31 represents a control valve serving as a valve mechanism for switching the hydraulic system between neutral, upward, and downward modes, and is housed within the hydraulic cylinder case 5 and fixed in place.
32 is a pilot spool (hereinafter simply referred to as spool), which is a control function component of the control valve 31. A spool pin 33 is implanted at one end of the spool 32 and allows the spool 32 to slide through the pin 33.

The control valve 31 has a housing 41
Lower link valve 42 parallel to spool 32 inside
However, check valves 43 are housed vertically. Reference numeral 44 designates a shutter-off spool disposed within the spool 32, and is pressed toward the left in FIG. 6 by a spring 45. Reference numeral 46 denotes a return spring for the spool 32, which can return the spool 32 from the raised position E to the neutral position and press it from the neutral position toward the lowered position G.

FIG. 6A shows the neutral state, and oil pumped from the hydraulic pump enters from the port 40 and flows from the outer periphery of the spool 32 to the inside, moving the shaft-off spool 44 to the right. The oil that has passed through the oil passage 47 is then returned into the transmission case from the port 48. On the other hand, the oil from the hydraulic cylinder 10 is
The check valve 43 and lower link valve 42 are shut off to maintain the working machine at a constant height.

FIG. 6B shows the rising state, in which the spool 32 is moved from the neutral position by the spool restraining lever 34 to the left against the return spring 46 and is in the raised position E. Therefore, the shaft-off spool 44 is moved to the left by the spring pressure of the internal spring 45, the oil passage 47 between the spool 32 and the shaft-off spool 44 is closed, and the oil that has been pressure-fed is transferred to the shaft-off spool 44. It passes through the outer periphery and pushes open the check valve 43, is supplied into the hydraulic cylinder 10, and raises the working machine.

Although the valve state is not shown during the descent, the spool 32 is moved from the neutral state to the descent position G by the return spring 46, and at the same time, the lower link valve 42 is moved to the right. As a result, the oil sent from the hydraulic pump is discharged from the port 48 to the transmission case, and at the same time, the oil in the hydraulic cylinder 10 also passes through the lower link valve 42 and from the port 49 due to the weight of the work equipment. The water is discharged into the mission case, and the falling speed of the working machine at this time is adjusted by adjusting the flow rate with the throttle valve 50.

In FIG. 2, the spool restraining lever 34 is pivoted on the fixed side at a slightly upper position of the spool 32 with a pin 35 so as to be rotatable around a horizontal axis. The lower end of the same lever 34 is the push metal fitting 3.
6 are connected, and a cam rod 37 is connected to the upper end. The length of the cam rod 37 can be freely adjusted with a turnbuckle 38, and is connected to a pin 39 installed in the upper part of the position cam plate 25.
Therefore, the cam rod 37 is connected to the spool holding lever 3.
4 and the position cam 27 are interlocked.

In FIG. 2 and FIG. 4 A and B, 51 is a position lever, and 52 is a draft lever, which are located outside the hydraulic cylinder case 5 and are guided by guide plates 53 and independently rotated. It is free. Reference numeral 55 denotes a draft lever shaft, which is a hollow shaft that is supported by penetrating the side wall of the hydraulic cylinder case 5. A draft cam pin 56 is erected at the inner end of the shaft so as to be offset from the rotation center of the same shaft 55. . Further, 57 is a position lever shaft, which is supported within the draft lever shaft 55, and has a coaxial shaft 5 at its inner end.
A position connector pin 58 is erected offset from the center of rotation of the connector 7.

The position lever 51 includes a swing lever 51A fixed to the outer end of a lever shaft 57 via a retaining pin 54, and a swing lever 51A that is located closer to the draft lever 52 than the swing lever 51A and is loosely fitted into the lever shaft 57. It has a brake lever 51B.

59 is a support member fixed to the hydraulic cylinder case 5 to support the draft lever shaft 55;
3 is also fixed, and a brake mechanism 88 is provided on a pin 60 protruding from this support member 59. Reference numeral 89 designates a bracket for the brake mechanism 88, which has a cylindrical member 90 fitted onto the pin 60 and a stop plate 91 fixed to one end of the cylindrical member 90.
The two brake plates 92a and 92b are fitted, and the brake plate 92a is connected to the draft lever 5.
2 and the brake lever 51B, the brake plate 92b is arranged on the outside of the brake lever 51B. 93 is a friction plate, 94 is a push spring fitted to the lever shaft 57 between the brake lever 51B and the stop plate 91, and this push spring 94 is connected to the levers 51B, 52, the brake plate 92a,
92b is pressed against a fixed support member 59 to provide a braking force for holding the levers 51B and 52 in the rotated position, and together with the friction plate 93, serves as rotational friction resistance means.

A pressure member 95 is provided between the swing lever 51A and the brake lever 51B. This elastic member 95 is formed of a spring that springs or pulls both levers 51A, 51B.

In addition, the swing lever 51A and the brake lever 51
A gripping member 96 (position setting member) is fitted to the upper end of B. This gripping member 96 is fitted onto the swing lever 51A, and is movable relative to the brake lever 51B by a required angle α (play). That is, the gripping member 96 serves as a first restricting portion 9 that restricts the relative rocking of the rocking lever 51A further toward the lowering side from a position shifted by an angle α with respect to the brake lever 51B.
7 (collision part), and a second part that rotates the brake lever 51B together from the position where it overlaps with the brake lever 51B when the swinging lever 51A is rotated upward.
It has a regulating part 98. Both regulating parts 97, 98
Alternatively, a tongue piece may be welded to one of the levers 51A, 51B, and the tongue piece may be brought into contact with the other lever.

The angle α approximately corresponds to the dead zone of the position lever 51. In other words, there is play within the link mechanism (described later) due to manufacturing errors,
Even if the position lever 51 is rotated, the spool 32
There is a dead zone (a type of play) in which the hydraulic system 11 does not respond and the hydraulic system 11 does not respond, and the position lever 51 passes through this dead zone and rotates in the upward direction to move the spool 32 to the upward position for the first time. Can be pushed to

When the gripping member 96 is rotated in the upward direction, only the swinging lever 51A is swung by the angle α, and the brake lever 51B is rotated from the overlapping position via the second regulating portion 98, and at this time, the spool 32 is rotated. Swing substantially in the upward direction. After that, when the grip member 96 is released, the swing lever 51A is elastically returned to swing by the action of the elastic member 95 until the first restriction portion 97 comes into contact with the brake lever 51B, that is, by the angle α. Since this return swing of the swing lever 51A is within the dead band, it does not substantially move the spool 32, but due to the return swing, the swing lever 51A is moved so that the first regulating portion 97 is 51B, thereby applying an impact to the link mechanism 73.

The position lever 51 is two levers 51.
A and 51B, both levers 51A and 51B are shifted by an angle α, and first and second regulating portions 97 and 98 are formed on the gripping member 96, thereby forming a load canceling means.

In FIG. 2, a position connector 61 is shaped like a shamisen plectrum, and its proximal end is connected to the position connector pin 58. The other end has an upper cam surface 62 on the upper and lower surfaces that widens at the end.
A lower cam surface 63 is carved. 64 is a spring connector, 65 is a position balancer, and the spring connector 6 is arranged laterally.
4 and a position balancer 65 arranged laterally.
The middle portions thereof intersect in a substantially cross shape, and the intersecting portions are pivotably supported on the fixed side by a horizontal common support shaft 66 so as to be rotatable independently of each other. Therefore, the common support shaft 66 is supported by passing through the hydraulic cylinder case 5 in the lateral direction, but it is of course equally effective if it is cantilevered. A roller 6 is attached to one end of the position balancer 65.
7, which is in contact with the lower cam surface 63 of the position connector 61, and the other end is provided with a pin 68, which is brought into contact with the position cam 27. Similarly, a roller 69 is provided at the upper end of the spring connector 64, which can come into contact with the upper cam surface 62 of the position connector 61, and a pin 70 is fixedly installed at the lower end, and the pusher fitting 36 is connected via the pin 70. It is connected to a pushing piece 71 inserted and supported at the other end. A spring 72 is inserted inside the pusher fitting 36, and the spring 72 can be pressed by the pushing piece 71.

Reference numeral 81 indicates a first draft link, which is arranged horizontally, and reference numeral 82 indicates a draft second link, which is arranged vertically.
3, and each end has a draft cam pin 5.
6 and a pin 84 provided near the pin 70 of the spring connector 64. The second draft
A side portion of the link 82 is disposed close to one side of the draft cam 8 so as to be able to freely come into contact with the lever shafts 56, 57 and the load spring arm 3.
A link mechanism 73 is constituted by the power transmission member from the spool holding lever 34 to the spool holding lever 34.

The hydraulic control device shown in the above embodiment can perform position control, draft control, and mix control that combines both of these controls, but since the draft and mix control are the same as the conventional device,
Only position control will be explained next.

Move the draft lever 52 fully in the direction of symbol D to bring it into the "down" state. Then, when the position lever 51 is moved in the "up" direction indicated by the symbol U, the swing lever 51A moves first, and after rotating by an angle α, the second regulating portion 9 is moved to the brake lever 51B.
8 comes into contact with the brake lever (51B) and rotates the brake lever (51B) against the frictional force of the brake mechanism 88. Since the position lever shaft 57 and the position connector pin 58 rotate in the same direction from the beginning of rotation of the swing lever 51A, the position connector 61 is drawn in the direction of the symbol L. Then, the upper cam surface 62 of the connector 61 pushes up the roller 69, so the spring connector 64 rotates clockwise around the common support shaft 66, and the pin 70 pushes the pusher fitting 36 in the direction of symbol L. A spool holding lever 34 is attached. When the rattling of each member has been absorbed up to this point, the swing lever 51A is in a state where it starts to rotate together with the brake lever 51B, and when the accompanying rotation starts, the spool 32
is pushed in the direction of symbol L, and by controlling the passage of hydraulic oil, the hydraulic piston 12 is pushed down, and the hydraulic arm 15 is rotated counterclockwise. As the position cam plate 25 rotates in the same direction, the pin 68 that is in contact with the position cam 27
Due to this movement, the position balancer 65 also rotates slightly counterclockwise. Then, the lower cam surface 63 of the position connector 61 moves downward with the downward movement of the roller 67, the spring connector 64 returns to its original position, and as a result, the push metal fitting 36 and the spool holding lever 34 move in that order. As a result, the spool 32 is returned to the neutral position by the action of the return spring 46 which is in elastic contact with the spool holding lever 34. At this time, the frictional resistance of the power transmission members of the position control system from the position cam plate 25 and the position lever shaft 56 to the spool restraining lever 34 acts on the spool 32 against the elastic pressure of the return spring 46. When both of them are statically balanced, the spool 32 stops at an intermediate position between the raised position E and the neutral position, and the oil passage 47 becomes incompletely open. However, after the position lever 51 has been rotated to the target position, the operator's hand is removed, and the gripping member 96 is swung in the downward direction by the action of the elastic member 95, and the first
The restriction portion 97 collides with the brake lever 51B.
This collision generates an impact on the swing lever 51A due to the sudden stop, and the impact is transmitted to the position control system, destroying the static balance between the return spring 46 and the spool 32.
6 completely returns to the neutral position, the oil passage 47 is completely communicated with the port 48, and the pressure inside the control valve 31 is prevented from building up.

Incidentally, the load cancel means in the present invention is as follows:
Instead of the first restricting part 97, a tongue piece that collides with the other may be fixed to one of the swing lever 51A or the brake lever 51B to form a collision part.

According to the present invention described in detail above, the position lever 51 has a swing lever 51A attached to the position lever shaft 57 so as to be integrally rotatable, and when the swing lever 51A is rotated upward, there is a play α. It has a brake lever 51B that rotates together through the brake lever 51B,
This brake lever 51B is provided with rotational friction resistance means between it and a member that supports the position lever shaft 57, and is provided between the swinging lever 51A and the brake lever 51B to release the rotational operation of the swinging lever 51A. When the swing lever 51A is moved back, the spring 4 is provided to return the swing lever 51A by the play α and the collision portion 97 to return the swing lever 51A to the neutral position.
When returning by the restoring force of 6, even if the restoring force tries to reach a static balance state with the frictional resistance of the link mechanism 73, it will be broken by the impact caused by the collision between the swing lever 51A and the brake lever 51B. , the pilot spool 32 can always return completely to the neutral position, and can prevent incomplete rise of hydraulic pressure due to incomplete return, and can prevent damage to the hydraulic pump, valve mechanism 31, etc. with an extremely simple configuration. It is possible to prevent this from happening.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a cross-sectional view of a hydraulic device, FIG. 2 is a cross-sectional assembly view of the main parts of a hydraulic control device, and FIG. 3 is a cross-sectional view taken along line A-A in FIG. 4A is a sectional view taken along the line B-B in FIG. 2, FIG. 4B is a sectional view taken along the Ro-Ro line in FIG. 4A, FIG. B is a cross-sectional explanatory view showing the control valve in its neutral and raised states, respectively. 11... Hydraulic system, 17... Lift arm, 3
1...Control valve (valve mechanism), 32
... Pilot spool, 34 ... Spool holding lever, 46 ... Return spring, 51 ... Position lever, 51A ... Swing lever, 51B ... Brake lever, 52 ... Draft lever, 73 ...
Link mechanism, 95... Resilience member, 96... Gripping member (position setting member).

Claims (1)

[Claims] 1. In order to operate the valve mechanism 31 for controlling the hydraulic device 11, the spool restraining lever 34 is activated via the link mechanism 73 by upwardly rotating the position lever 51 provided on the position lever shaft 57. The lift arm 17 swings and pushes the pilot spool 32, which is in elastic contact with the pilot spool 32 via the return spring 46.
The spool holding lever 34 returns and swings in conjunction with the rise of the pilot spool 32 to return the spring 4.
6, the position lever 51 includes a swing lever 51A that is rotatably attached to a position lever shaft 57, and a swing lever 51A that is rotatably attached to a position lever shaft 57. When the brake lever 51B rotates upward, the brake lever 51B rotates along with the brake lever 51B through play α.
A rotational friction resistance means is provided between the member supporting the position lever shaft 57, and a rotational friction resistance means is provided between the swinging lever 51A and the brake lever 51B, and when the swinging lever 51A is released from the swinging operation, Pressing member 9 that returns and swings the movable lever 51A by the amount of play α
5 and a collision portion 97 for returning to collision.