JPH0749664B2 - Hydraulic drive circuit for attachment translation operation of loader for agricultural machinery tractor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydraulic drive circuit for parallel movement of an attachment of a loader for an agricultural machine tractor, and more particularly to a tilt cylinder for driving an attachment rather than a lift cylinder for driving a lift arm. Can be made smaller, the attachment can be moved in parallel accurately, and the hydraulic circuit can be simplified. Moreover, the dump swing speed or the tilt-down swing speed is fast, the discharge performance is improved, and the agricultural machine tractor The present invention relates to a hydraulic drive circuit for parallel movement of an attachment of a loader for an agricultural machine tractor, in which one of existing hydraulic directional control valves can be used as it is.

<Prior art> A loader used for civil engineering work or construction work is usually operated by a person who is familiar with the operation of the loader, whereas a loader of an agricultural tractor that drives an agricultural machine is operated by a person engaged in plain agriculture. Therefore, it is not possible to expect advanced driving technology such as adjusting and operating the lift arm and attachments such as buckets and forks at the same time. Therefore, in a hydraulic drive device for a loader of an agricultural machine tractor, as shown in, for example, Japanese Patent Publication No. Sho 62-23719, the attachment can be moved in parallel while the posture is kept constant when the lift arm is moved up and down. There is a device configured as described above to facilitate the operation.

For example, as shown in the above-mentioned publication or FIGS. 4 and 5, the hydraulic drive system 2 ′ that can move the attachment of the conventional agricultural machine tractor loader 1 in parallel is used for raising or lowering the lift arm 5 for swinging or attaching. (For example, a bucket) 6 tilt-up swing operation or tilt-down swing operation, lift arm 5 raise and swing operation, and automatically tilt attachment 6 down while keeping the posture of attachment 6 constant. A structure for performing a parallel ascending movement operation for ascending, a swinging operation for descending the lift arm 5 and automatically tilting up the attachment 6 to perform a parallel descending movement operation for descending in parallel while keeping the posture of the attachment 6 constant. Has been done.

That is, the hydraulic drive device 2 ′ of the agricultural machine tractor loader 1 is provided with the lift operation valve 3 and the tilt operation valve 4, and when the tilt operation valve 4 is positioned at the neutral position, the hydraulic pressure is changed by switching the lift operation valve 3. The pressure oil discharged from the pump 7 is supplied to the pressure feed path P at the lift operation position of the lift operation valve 3.
The extension drive oil chamber 8 _L or the shortening drive oil chamber 8 _S of the lift cylinder 8 is pressed into the extension drive oil chamber 8 _{L of} the lift cylinder 8 or the extension drive oil chamber 8 _{S of the} lift cylinder 8 through the pressure feed path P _{LD of LU} or the lowering operation position. _The pressure oil discharged from _L is passed through the return path D _LU of the lift operation valve 3 at the ascending operation position or the return path D _LD of the descending operation position to return oil guide path 9, pressure feed relay path 10,
Relay path C _{NR in} the neutral position of tilt control valve 4, return relay path 1
1. Return to the oil tank 13 through the relay passage C _LU in the lift operation position of the lift operation valve 3 or the relay passage C _{LD in the} lower operation position and the return oil passage 12, and _extend and retract the lift cylinder 4 to move the lift arm 5 up and down. The hydraulic pump 7 is configured to swing, and the tilt operation valve 4 is switched while the lift operation valve 3 is in the neutral position.
The pressure oil discharged from the lift control valve 3 through the pressure feed path N _{PL at} the neutral position, the pressure feed relay path 10, the tilt up operation position pressure feed path P _{TU of} the tilt operation valve 4 or the tilt down operation position pressure feed path P _TD . While press-fitting into the tilt-up drive oil chamber 14 _S or tilt-down drive oil chamber 14 _L of the tilt cylinder 14, the tilt-down drive oil chamber 14 _{L of the} tilt cylinder 14
Alternatively, the pressure oil discharged from the tilt-up drive oil chamber 14 _S may be returned to the tilt-up operation position return path D _{TU of the} lift operation valve 4.
And through the return oil passage 12 or the return passage D _{TD at} the tilt-down operation position, the return relay passage 11, the return passage N _{DL at} the neutral position of the lift operation valve 3 and the return oil passage 12 and return to the oil tank 13, and tilt. The cylinder 14 is expanded and contracted to swing the attachment 6 in a tilt-up or tilt-down manner. As shown in FIG. 4, the lift operating valve 3 is placed in the raising operating position and the tilt operating valve 4 is tilted. In the parallel rising operation state in which the hydraulic pump 7 is placed in the down operation position, the pressure oil discharged from the hydraulic pump 7 is press-fitted into the extension drive oil chamber 8 _L of the lift cylinder 8 through the pressure feed path P _LU of the lift operation valve 3 in the raising operation position, The lift cylinder 5 is extended to extend the lift arm 5.
While increasing swing, increase the operating position of the return path D _LU of the lift operating valve 3 to return oil pushed from the extended drive oil chamber 8 _S of the lift cylinder 8, tilting down the return oil guide passage 9 and a tilt operation valve 4 The pressure oil, which is pressed into the tilt-down drive oil chamber 14 _L of the tilt cylinder 14 through the pressure feed path P _TD at the operation position and is pushed out from the tilt-up drive oil chamber 14 _{S of the} tilt cylinder 14, tilts down the tilt operation valve 4. Return to the oil tank 13 via the return path D _{TD in} the operation position, the return relay path 11, the relay path C _{LU in} the raising operation position of the lift operation valve 3 and the return oil path 12, and operate the tilt cylinder 14 to the tilt down side. The attachment 6 is configured to be moved up in parallel by swinging the attachment 6 in a tilt-down manner, and as shown in FIG. 5, the lift operating valve 3 is put in the descending operating position. In parallel descending operating conditions which supplied the belt operation valve 4 in the tilt-up operation position, pressure oil discharged from the hydraulic pump 7 passes through the pumping path P _LD in lowering operation position of the lift operating valve 3, shortening the driving of the lift cylinders 8 While being press-fitted into the oil chamber 8 _S , the lift cylinder 8 is contracted to swing the lift arm 5 downward, the return oil pushed out from the extension drive oil chamber 8 _{L of} the lift cylinder 8 is transferred to the lower operation position of the lift operation valve 3. Return path D _LD , check valve 15, return oil guide path 9, check valve 16 and pressure feed path P _TU of tilt up operation position of tilt operation valve 4 to tilt up drive oil chamber 14 _S of tilt cylinder 14. The pressure oil that is pressed in and pushed out from the tilt-down drive oil chamber 14 _{L of} the tilt cylinder 14 is pushed out by the return path D _TU of the tilt-up operation position of the tilt operation valve 4.
Return to the oil tank 13 via the return oil passage 12, and tilt cylinder 14
To move the attachment 6 to the tilt-up side to drive the attachment 6 to tilt-up and swing.
Is configured to be moved in parallel downward movement. Further, the lift cylinder 8 is moved during the parallel downward movement rather than during the parallel upward movement.
A large amount of oil is discharged from the tilt cylinder 14
Since the amount of oil that is press-fitted into is reduced, the throttle passage 32 is connected to the return passage D _LD of the lowering operation position of the lift operating valve 3 in common with the check valve 15 during parallel downward movement, and is discharged from the lift cylinder 8. A part of the oil amount is throttled through the passage 32 to the oil tank.
It is supposed to return to 13.

<Problems to be Solved by the Invention> The conventional example configured as described above has the following problems (1) to (6).

That is, (1) the oil chamber on the contraction drive side of the tilt cylinder 14 is made the oil chamber for tilt up drive 14 _S, and the oil chamber on the extension drive side is made the oil chamber for tilt down drive 14 _L. it is necessary to increase only the cross-sectional area occupied by the piston rod in a tilt-up force cylinder cross-sectional area required to obtain the tilt-up drive oil chamber 14 _S necessary. Further, the tilt down force only needs to be such that the attachment 6 is grounded and the front wheel of the tractor can be lifted, and it may be smaller than the tilt up force, so the tilt cylinder 14 becomes larger than necessary and becomes expensive. There is a problem.

(2) Since the amount of pressure oil discharged from the contraction drive oil chamber 8 _{S of the} lift cylinder 8 and the amount of pressure oil pressed into the tilt-down drive oil chamber 14 _L of the tilt cylinder 14 are equal according to the law of continuity, tilt As the cylinder 14 has a large diameter, the lift cylinder 8 also needs to be unnecessarily increased in size, which causes a problem that the lift cylinder 8 becomes expensive.

(3) The distribution of the amount of oil press-fitted into the tilt cylinder 6 and the amount of oil released from the throttle passage 32 during the parallel downward movement is determined by the pressure of the tilt-up drive oil chamber 14 _S and the throttle diameter of the throttle passage 32. Therefore, if the discharge pressure of the hydraulic pump 7 changes or the load of the attachment 6 changes due to a change in the engine speed of the tractor that determines the rotation speed of the hydraulic pump 7, the tilt cylinder 6 is press-fitted. There is a problem in that the distribution ratio between the amount of oil that is discharged from the throttle passage 32 and the amount of oil that is released from the throttle passage 32 changes, and the attitude control such as the leveling of the attachment 6 is disturbed.

(4) The amount of oil discharged from the lift cylinder 8 and the tilt cylinder 14 in the parallel ascending operation state and the parallel descending operation state.
Since the amount of oil press-fitted into the oil passage is different, it is necessary to switch the connection between the oil passage to which the throttle passage 32 is not connected and the oil passage to which the throttle passage 32 is connected, which complicates the circuit configuration of the hydraulic drive system 2 '. There is a problem that it becomes expensive.

(5) Since the attachment 6 when the tilt cylinder 14 is extended is configured to tilt down, extension rate of the amount corresponding to the tilt cylinder 14 corresponding to the volume occupied by the piston rod in a tilt-up cylinder chamber 14 _S Is slower than the shortening speed of the tilt cylinder 14, and there is a problem that the emission performance at the time of damping becomes low.

(6) Lift operation valve 3 used in the hydraulic drive circuit 2 '
Also, since the internal oil passages of the tilt operation valve 4 are complicated, these valves 3 and 4 are made as dedicated valves separate from the directional control valve installed in the tractor, so the number of parts is large and the price is low. There is a problem that it will be disadvantageous in terms of commercialization.

<Means for Solving Problems> The hydraulic drive circuit for attachment parallel movement operation of the agricultural machine tractor loader according to the present invention has been proposed for the purpose of solving the above problems. For example, as shown in FIG. 1 and FIG. 2 or FIG. 3, the extension force of the lift cylinder 8 of the lift arm 5 of the loader 1 for agricultural machinery tractor is used to drive up and down and the contraction force to drive down and up. And the attachment 6 attached to the tip of the lift arm 5 is configured so that the extension force of the tilt cylinder 14 drives the tilt-up swing and the contraction force swings the tilt-down. The hydraulic drive device 2 is provided with a pressure feed direction switching valve 3 and a drive type selection valve 4, and the pressure feed direction switching valve 3 has a neutral position, a forward direction pressure feeding position, and a reverse direction pressure feeding position. , And the drive type selection valve 4 is selectively switchable between a tilt cylinder selection position, a parallel rising selection position, and a parallel lowering selection position. In the tilt-down operation state in which the drive type selection valve 4 is placed in the tilt cylinder selection position while the drive type selection valve 4 is placed in the positive direction delivery position, the pressure oil discharged from the hydraulic pump 7 is in the forward delivery position of the delivery direction switching valve 3. P _P
And the contraction drive oil chamber 14 _S of the tilt cylinder 14 through the tilt-down drive oil passage P _TD at the tilt cylinder selection position of the drive type selection valve 4, and the tilt cylinder 14 is contracted so that the tip end of the lift arm 5 is closed. In the tilt-up operation state, the attachment 6 is configured to perform tilt-down rocking drive, the pressure feed direction switching valve 3 is closed to the reverse pressure feed position, and the drive type selection valve 4 is closed to the tilt cylinder selection position. The pressure oil discharged from the pressure feed passage P _{N at} the reverse pressure feed position of the pressure feed direction switching valve 3
And the tilt-up drive oil passage P _TU at the tilt-cylinder selection position of the drive type selection valve 4 is press-fitted into the extension drive device of the tilt cylinder 14, and the tilt cylinder 14 is extended to drive the attachment 6 to tilt-up swing. The drive type selection valve 4 to the parallel rising selection position
_LU , lift return path D _LU , tilt-down pressure feed path P _TD, and tilt-down return path D _TD are provided, and the hydraulic pump 7 pumps pressure at the parallel lift operation position where the drive type selection valve 4 is placed in the parallel lift selection position. The pressure oil supplied to the drive type selection valve 4 through the direction switching valve passes through the ascending pressure feed path P _LU and is press-fitted into the extension drive oil chamber 8 _L of the lift cylinder 8 to extend the lift cylinder 8 and lift arm. 5 is driven upward, and the return oil pushed out from the contraction drive oil chamber 8 _{S of the} lift cylinder 8 passes through the return path D _LU for ascent and is _divided by the shunt valve 17 into the oil tank 13.
An attachment is diverted to the pumping for tilt-down path P _TD, is pressed from the pumping tilt down path contraction drive chamber 14 _S of the tilt cylinder 14, by tilting down swing the attachment 6 by contracting the tilt cylinder 14 6
Is configured to drive in parallel, and the pressure feed path P for lowering is set to the parallel lowering selection position of the drive type selection valve 4.
_LD , descending return path D _LD , tilting up pressure feeding path P _TU and tilting up return path D _TU are provided, and in the parallel lowering operation state in which the drive type selection valve 4 is put in the parallel lowering selection position, pressure is fed from the hydraulic pump. The pressure oil supplied to the drive type selection valve 4 via the direction switching valve 3 passes through the descending pressure feed path P _LD and is press-fitted into the contraction drive oil chamber 8 _S of the lift cylinder 8 to contract the lift cylinder 8 and lift. While the arm 5 is driven to descend and swing, the return oil pushed out from the extension drive oil chamber 8 _{L of} the lift cylinder 8 passes through the return path D _LD for descending and is divided by the flow dividing valve 17 into the oil tank 13 and the pressure feed path P _TU for tilt-up. _{Is divided} into two parts, and is pressed into the extension drive chamber 14 _L of the tilt cylinder 14 from the tilt-up pressure feed path P _TU to extend the tilt cylinder 14,
It is characterized in that the attachment 6 is configured to be driven to descend in parallel by swinging the attachment 6 to tilt up.

<Operation> Since the present invention is configured as described above, the following (a)
It works like (f).

(A) The tilt cylinder 14 is interlockingly connected to the attachment 6 so as to drive to the tilt-up side during the extension operation and to the tilt-down side during the contraction operation, and the oil chamber on the extension drive side of the tilt cylinder 14 is used for the tilt-up drive. while the oil chamber 14 _L, so are the oil chamber of the contraction drive side to the tilt-down driving oil chamber 14 _S, in particular the diameter of the tilt-up drive oil chamber 14 _L that must withstand the load of the attachment 6 the oil chamber contraction drive side as compared with the conventional tilt cylinder 14 that is in the tilt-down driving oil chamber 14 _S, corresponding to the cross-sectional area of the piston rod has been occupied by the conventional tilt-up drive oil chamber 14 _S Can be made smaller.

(B) Since the amount of pressure oil discharged from the list-down oil chamber 8 _{S of the} lift cylinder 8 and the amount of pressure oil pressed into the tilt-down drive oil chamber 14 _S of the tilt cylinder 14 are equal according to the law of continuity, tilt The lift cylinder 14 can be downsized correspondingly to the fact that the cylinder 14 can be downsized.

(C) Oil amount and oil tank press-fitted into the tilt cylinder 14
The distribution of the amount of oil to be returned to 13 is made up of the diversion valve 17 regardless of the throttle passage 32 whose flow rate changes due to the discharge pressure of the hydraulic pump 7 or the load of the attachment 6, so that it is press-fitted into the tilt cylinder 14. The distribution ratio of the amount of oil to be supplied to the oil tank 13 is constant without being affected by the discharge pressure of the hydraulic pump 7, the load of the attachment 6, the viscosity of the pressure oil, or the like.

(D) In the parallel ascending operation state, the return oil pushed out from the contraction drive oil chamber 8 _S of the lift cylinder 8 is reduced by the diversion valve 17 at a fixed ratio, and the tilt down drive oil chamber of the tilt cylinder 14 is driven.
14 _S , that is, the return oil that is press-fitted into the shortening drive-side oil chamber and is pushed out from the extension drive oil chamber 8 _L of the lift cylinder 8 in the parallel lowering operation state is reduced by the diversion valve 17 at a fixed ratio and the tilt cylinder 14 tilts. Since it is adapted to be press-fitted into the up drive oil chamber 14 _L , that is, the oil chamber on the extension drive side, the throttle passage 32 is used to switch the amount of oil press-fitted into the tilt cylinder 14 between the parallel ascending operation state and the parallel descending operation state. It is not necessary to switch the connection between the oil passage not connected with the oil passage and the oil passage connected with the throttle passage 32.

(E) The tilt cylinder 14 is interlockingly connected to the attachment 6 so as to drive to the tilt-up side during the extension operation and to the tilt-down side during the contraction operation, and the oil chamber on the extension drive side of the tilt cylinder 14 is driven to the tilt-up drive oil. The oil chamber on the contraction drive side is tilted down while the chamber is set to 14 _L.
Since it is set to 14 _S , compared to the conventional tilt cylinder 14 in which the oil chamber on the extension drive side is tilt down drive oil chamber 14 _S , it corresponds to the volume occupied by the piston rod in tilt down drive oil chamber 14 _S. The tilt cylinder 14 can be shortened faster than the tilt cylinder 14 is extended.

(F) The pressure feed directional control valve 3 may be any one that can be selectively switched between the neutral position, the positive pressure feed position and the reverse pressure feed position, and a commercially available inexpensive directional control valve is used. ,
The price can be reduced.

<Effects of the Invention> Since the hydraulic drive system capable of moving the attachment of the agricultural machine tractor loader in parallel according to the present invention operates as described above, the following effects A to F are achieved.

A. As described in (a) above, the tilt cylinder can be configured with a cylinder with a small output that can handle the load received by the attachment. And cost reduction can be achieved.

B. Since the amount of pressure oil discharged from the lift-down oil chamber of the lift cylinder and the amount of pressure oil injected into the tilt-up drive oil chamber of the tilt cylinder are equal according to the law of continuity,
Since the tilt cylinder can be made smaller, the lift cylinder can be made smaller and the lift cylinder can be made lower in price.

C. As described in (c) above, the distribution ratio between the amount of oil press-fitted into the tilt cylinder and the amount of oil returned to the oil tank is affected by the discharge pressure of the hydraulic pump, the load of the attachment, the viscosity of the pressure oil, etc. Since it becomes constant without moving, it is possible to prevent the attitude control of the attachment from being misaligned during the parallel upward movement or the parallel downward movement.

D. As described in (d) above, an oil passage to which the throttle passage is not connected and an oil passage to which the throttle passage is connected for switching the amount of oil press-fitted into the tilt cylinder between the parallel ascending operation state and the parallel descending operation state. Since it is not necessary to switch the connection, the circuit configuration of the hydraulic drive circuit is simplified and the cost is reduced.

E. As described in (f) above, the shortening speed of the tilt cylinder 14 can be made higher than the extension speed of the tilt cylinder 14, so that the discharging performance at the time of damping becomes high.

F. The pressure feed directional control valve may be one that can be selectively switched to the normal neutral position, the positive pressure feed position, and the reverse pressure feed position. For example, the existing standby hydraulic pressure directional control valve of the tractor can be used as it is. It can be used to reduce the price.

<Example 1> An example of the present invention will be described below with reference to Figs. 1 and 2.

A hydraulic drive circuit 2 of this agricultural machine tractor loader 1 is provided with a pressure-feed direction switching valve 3 and a drive type selection valve 4.

The pressure feeding direction switching valve 3 can be selectively switched to three positions of a neutral position and a forward pressure feeding position and a backward pressure feeding position which are distributed around the neutral position. The pressure oil discharged from the pump 7 passes through the relay path C _NR and is returned to the oil tank 13 via the return oil path 12. This pressure feed direction switching valve 3 uses an existing spare direction switching valve for a tractor (not shown) as it is, and the portion of the hydraulic drive circuit 2 on the drive type selection valve 4 side from this pressure feeding direction switching valve 3 is attached to the tractor as an option To be done.

The drive type selection valve 4 is configured to be selectively switchable between a tilt cylinder selection position, a parallel rising selection position, and a parallel falling selection position.

In the tilt-down operation state in which the pressure feed direction switching valve 3 is put in the forward pressure feed position and the drive type selection valve 4 is put in the tilt cylinder selection position, the pressure oil discharged from the hydraulic pump 7 is directly fed to the pressure feed direction switching valve 3. Direction pumping position pumping path
P _P , one relay passage 10 and the tilt-down drive pressure oil passage P _TD at the tilt cylinder selection position of the drive type selection valve 4 are pressed into the contraction drive oil chamber 14 _S of the tilt cylinder 14, and the tilt cylinder 14 is removed. While contracting to drive the attachment 6 at the tip of the lift arm 5 to tilt and swing, the pressure oil pushed out from the extension drive oil chamber 14 _{L of} the tilt cylinder 14 tilts down at the tilt cylinder selection position of the drive type selection valve 4. The other repeater 11, the pumping direction switching valve 3 and the return channel D _{P at the} forward pumping position and the return oil channel 12 are passed through the driving return channel D _TD.
And returned to the oil tank 13.

In the tilt-up operation state in which the pressure feed direction switching valve 3 is put in the reverse pressure feed position and the drive type selection valve 4 is put in the tilt cylinder selection position, the pressure oil discharged from the hydraulic pump 7 is in the reverse direction of the pressure feed direction change valve 3. Pumping path P _{N at} the pumping position,
It is press-fitted into the extension drive oil chamber 14 _L of the tilt cylinder 14 through the tilt-up drive pressure oil passage P _TU at the tilt cylinder selection position of the other relay device 11 and drive type selection valve 4 to extend the tilt cylinder 14. The attachment 6 is driven to tilt up and swing, while the tilt cylinder 14 contracts and drives the oil chamber.
14 tilting up driving return path D _TU of pressure oil to the tilt cylinder selection position of the drive type selection valve 4 extruded from _S, the return path D _N reverse pumping position of the one intermediate path 10 and the pumping direction switching valve 3 Passed back to the oil tank 13.

At the parallel rising selection position of the drive type selection valve 3, a lifting pressure feeding path is provided.
A _PLU , an ascending return path _DLU , a tilt-down pressure feed path _PTD, and a tilt-down return path _DTD are provided. In the parallel ascending operation state in which the drive type selection valve 4 is put into the parallel ascending selection position, the hydraulic pump 7 moves to the pressure direction switching valve 3 and one repeater.
The pressure oil supplied to the drive type selection valve 4 via 10 passes through the ascending pressure feed path P _LU, and the extension drive oil chamber 8 of the lift cylinder 8
Is pressed _{L, and} return oil return passage D _LU ascending extruded from contraction drive oil chamber 8 _S of Rifutoshirinta 8 with increasing drive the lift arm 5 by extending the lift cylinder 8
Through the shunt valve 17 to the oil tank 13 and the tilt-down pressure feed path.
Is split into a P _TD, attachment 6 by being pressed from the pumping tilt-down path P _TD contraction drive oil chamber 14 _S of the tilt cylinder 14, tilt down swing the attachment 6 the tilt cylinder 14 is吸縮While the parallel drive is performed, the pressure oil pushed out from the extension drive oil chamber 14 _{L of} the tilt cylinder 14 is returned to the tilt-down return path D _TD of the drive type selection valve 4, the other relay device 11, the pressure feed direction switching valve 3 and the return valve. It is returned to the oil tank 13 via the oil passage 12.

The descending pressure feed path is provided at the parallel descending selection position of the drive type selection valve 4.
A P _LD , a descending return path D _LD , a tilt-up pressure feeding path P _TU, and a tilt-up return path D _TU are provided. In the parallel lowering operation state in which the drive type selection valve 4 is put in the parallel lowering selection position, the pressure oil supplied from the hydraulic pump 7 to the drive type selection valve 4 via the pressure feed direction switching valve 3 and the other relay 11 is lowered. It is pressed into the contraction drive oil chamber 8 _S of the lift cylinder 8 through the pressure feed path P _LD , contracts the lift cylinder 8 to drive the lift arm 5 to descend and swing, and also extends the drive cylinder 8 _{L of the} lift cylinder 8. The return oil extruded from the flow path is _divided into the oil tank 13 and the tilt-up pressure feed path P _TU by the diversion valve 17 through the descent return path D _LD, and the extension drive oil for the tilt cylinder 14 is extended from the tilt-up pressure feed path P _TU. Pressed into the chamber 14 _L , the tilt cylinder 14 is extended, and the attachment 6 is tilted up and rocked to drive the attachment 6 in parallel and downward, while the tilting cylinder 14 contraction drive oil chamber.
Pressure oil pushed out from 14 _S causes tilt up return path D _TU ,
It is returned to the oil tank 13 through one of the relays 10, the return passage _DN and the return oil passage 12 at the position of the reverse direction of the pressure-direction switching valve 3.

As described above, the tilt cylinder 14 is attached to the attachment 6
To, to tilt up side during extended operation, the interlocking is connected to drive the tilt-down side during contraction operation, as well as the extension drive oil chamber 14 _L of the tilt cylinder 14 to tilt up the drive oil chamber, the contraction Kaabura chamber Since 14 _S is a tilt-down drive oil chamber, the diameter of the extension drive oil chamber 14 _L required to obtain the tilt-up force required for work can be reduced by a size corresponding to the cross-sectional area occupied by the piston rod. ,
It is possible to reduce the diameter of the tilt cylinder 14 and reduce the price of the tilt cylinder 14. In addition, the lift cylinder 8 can be downsized in response to the downsizing of the tilt cylinder 14, and the lift cylinder 8 can be made low in cost.

Also, the amount of oil press-fitted into the tilt cylinder 14 and the oil tank 13
The distribution of the amount of oil to be returned to the throttle passage whose flow rate changes under the influence of the discharge pressure of the hydraulic pump 7 or the load of the attachment 6.
Since it is distributed by the flow dividing valve 17 regardless of 32, the distribution ratio between the amount of oil press-fitted into the tilt cylinder 14 and the amount of oil returned to the oil tank 13 is the discharge pressure of the hydraulic pump 7 or the load of the attachment 6, the pressure oil. It is constant without being affected by the viscosity of

Furthermore, increased in parallel operation state is pressed return oil pushed out from a contracted drive oil chamber 8 _S of the lift cylinder 8 is fixed ratio reduction in diversion valve 17 to shrink the drive oil chamber 14 _S of the tilt cylinder 14, lowered parallel operation state Is configured so that the return oil pushed back from the extension drive oil chamber 8 _{L of the} lift cylinder 8 is reduced by a certain ratio by the flow dividing valve 17 and press-fitted into the extension drive oil chamber 14 _L of the tilt cylinder 14, so that the parallel rise In order to switch the amount of oil press-fitted into the tilt cylinder 14 between the operating state and the descending parallel operating state, it is not necessary to switch the connection between the oil passage to which the throttle passage 17 is not connected and the oil passage to which the throttle passage 17 is connected. It is possible to reduce the cost by simplifying the circuit configuration of the drive circuit.

Furthermore, the tilt cylinder 14 presses the pressure oil into the extension drive oil chamber 14 _L during the extension operation to drive it to the tilt-up side during the extension operation, and presses the pressure oil into the contraction drive oil chamber 14 _S during the contraction operation. Since it is interlockingly connected to drive to the tilt-down side, the diameter of the tilt-up drive oil chamber 1414 _L , which needs to bear the load of the attachment 6 in particular, is set to the tilt-up drive oil chamber 14 compared to conventional tilt-down drive oil chamber 14 _S we have to _S, the sectional area of the piston rod has been occupied by the conventional tilt-up drive oil chamber 14 _S can be reduced correspondingly, the size and cost reduction Can be planned.

In addition, as described above, since the tilt cylinder 14 is linked to the attachment 6 so as to drive it to the tilt-up side during the extension operation and to the tilt-down side during the contraction operation, the extension drive oil chamber 14 _L is tilted down. compared to conventional tilt cylinder 14 that is the drive oil chamber, faster than the contraction rate of the tilt cylinder 14 to the extension speed of the tilt cylinder 14 in response to the volume occupied by the piston rod in a tilt-down drive oil chamber 14 _L Therefore, the tilt-down speed can be increased to enhance the emission performance.

<Embodiment 2> FIG. 3 is a hydraulic drive circuit diagram of another embodiment of the present invention.
In this embodiment, the tilt-up speed increasing valve 1
8, a brake valve device 19, a single / double switching on-off valve 20, a mounting cylinder 21, and a connection switching valve 22 to be connected.

The tilt-up speed increasing valve 18 is tilted as necessary with the drive type selection valve 4 in the tilt cylinder selection position or the parallel descending selection position with the pressure-feed direction switching valve 3 in the forward direction pressure-feed position. Cylinder 14 contraction drive oil chamber
It is configured to connect 14 _S to the extension drive oil chamber 14 _L. Then, for example, after the attachment 6 is tilted down and damped while the lift arm 5 is raised, the pressure oil pushed out from the contraction drive oil chamber 14 _S during the parallel lowering operation is transferred to the extension drive oil chamber 14 _L. By press-fitting, the extension speed of the tilt cylinder 14 is increased, the attachment 6 is tilted up at a higher speed than in parallel descending, and when the lift arm 5 is lowered, the attachment 6 automatically becomes horizontal (here The bucket rake surface is parallel to the ground).

The brake operation valve 19 is interposed in an oil passage connecting the extension drive oil chamber 14 _L of the tilt cylinder 14 and the drive type selection valve 4, and the internal pressure of the contraction drive oil chamber 14 _S of the tilt cylinder 14 is a predetermined value. closed when made below, to prevent the extension drive oil chamber 14 _L of the hydraulic fluid is pushed out, the attachment 6
Is prevented from swinging in the tilt-down direction.

The single / double switching on-off valve 20 is for directly connecting the contraction drive oil chamber 8 _S of the lift cylinder 8 to the return oil passage 12 when only the lift cylinder 8 is operated to be lifted.

Examples of the mounting cylinder 21 include a cylinder for mounting the loader 1 on a tractor, a cylinder provided on the attachment 6 such as a glove opening / closing driving cylinder, or a lifting cylinder for another working device. For example, in the case of a cylinder in which the loader 1 is mounted on a tractor, the connection switching valve 22 can be used only when the loader 1 is attached or detached.
Also, pressure oil is press-fitted from the hydraulic pump 7 into the extension drive oil chamber 21 _L or the contraction drive oil chamber 21 _S via the pressure transfer direction switching valve 3,
The pressure oil pushed out from the other side is returned to the oil tank 13 via the connection switching valve 22, the pressure direction switching valve 3 and the return oil passage 12.

The rest of the configuration of this embodiment is the same as that of the above-mentioned one embodiment, and therefore its explanation is omitted.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of one embodiment of the present invention at the time of parallel raising operation, FIG. 2 is a hydraulic circuit diagram of one embodiment of the present invention at the time of parallel lowering operation, and FIG. 3 is another embodiment of the present invention. An example hydraulic circuit diagram, FIG. 4 is a hydraulic circuit diagram of a conventional example at the time of parallel raising operation, and FIG. 5 is a hydraulic circuit diagram of the conventional example at the time of parallel lowering operation. 1 ... loader, 2 ... hydraulic drive circuit, 3 ... pressurization direction switching valve, 4 ... drive type selection valve, 5 ... lift arm, 6
...... Attachment, 7 ...... Hydraulic pump, 8 ...... Lift cylinder, 8 _L ...... Extension drive oil chamber, 8 _S ...... Contraction drive oil chamber,
9 ...... Return oil guide path, 12 ...... Return oil path, 13 ...... Oil tank, 14 ...... Tilt cylinder, 14 _L ...... Extension drive oil chamber, 14 _S
...... Shrinkage drive oil chamber, 17 ...... Dividing valve, D _LD ...... Return path for descending drive of drive type selection valve 4, D _LU ...... Drive type selection valve 4
Return path for ascending drive, D _N ...... Return path of the pumping direction switching valve 3 in the reverse direction pumping position, D _P …… Return path of the pumping direction switching valve 3 in the forward direction pumping position, D _TD …… Drive type selection Return path for tilt-down operation of valve 4, D _TU ... drive type selection Return path for tilt-up drive of valve 4, P _LU ... drive type selection Pressure feed path for rising drive of valve 4, P _LD ... drive type selection Pressure feeding path for lowering operation of valve 4, P _N ... pressure feeding path of reverse direction pressure feeding position of pressure feeding direction switching valve 3, P _P ... pressure feeding path of forward direction pressure feeding position of pressure feeding direction switching valve 3, P _TD ... drive Tilt-down operation pressure feed path for type selection valve 4, P _TU ... Tilt-up operation pressure feed path for drive type selection valve 4.

Claims (1)

[Claims] 1. A lift arm (5) of a loader (1) for an agricultural machine tractor, which is configured to be driven to swing up by extension force of a lift cylinder (8) and to swing down to drive contraction force. The attachment (6) attached to the tip of (5) is configured so that the extension force of the tilt cylinder (14) drives the tilt-up swing and the contraction force swings the tilt-down, and the lift cylinder (8) and The hydraulic drive device (2) of the tilt cylinder (14) is provided with a pressure feed direction switching valve (3) and a drive type selection valve (4), and the pressure feed direction switching valve (3) is in the neutral position and in the forward direction and in the reverse direction. The drive type selection valve (4) is selectively switchable between a tilt cylinder selection position, a parallel rising selection position, and a parallel descending selection position. Set the switching valve (3) to the right The tilt-down operation state which supplied drive type selection valve (4) in the tilt cylinder selected position with introducing countercurrent pumping position, the hydraulic pump (7)
The pressure oil discharged from the pressure feed passage (P _P ) at the forward pressure feed position of the pressure feed direction switching valve (3) and the tilt down drive oil passage (P _TD ) at the tilt cylinder selection position of the drive type selection valve (4)
Through the contraction drive oil chamber (1
4 _S ) is press-fitted to contract the tilt cylinder (14),
The attachment (6) at the tip of the lift arm (5) is configured to be tilt-down rocking driven, and the pressure feed direction switching valve (3) is put in the reverse pressure feed position and the drive type selection valve (4) is tilted. In the tilt-up operation state in which the hydraulic pump (7) is thrown into the selector selection position, the pressure oil discharged from the hydraulic pump (7) is in the reverse direction pumping position of the pumping direction switching valve (3) and the drive type selection valve ( _PN ). 4) It is pressed into the extension drive device of the tilt cylinder (14) through the tilt-up drive oil passage (P _TU ) at the tilt cylinder selection position of 4) to extend the tilt cylinder (14) and tilt the attachment (6). It is configured to drive up and swing, and the pressure feed path for ascent (P _LU ), the return path for ascent (D _LU ), and the pressure feed path for tilt down (P _TD ) at the parallel ascent position of the drive type selection valve (4). And tilt dow Use the return path (D _TD) and is provided, in parallel increases the operation state which supplied drive type selection valve (4) to increase selection position parallel, from the hydraulic pump (7) via the pumping direction switching valve (3) driving type selection valve The pressure oil supplied to (4) passes through the ascending pressure feed path (P _LU ) and is press-fitted into the extension drive oil chamber (8 _L ) of the lift cylinder (8) to extend the lift cylinder (8). , The lift arm (5) is driven upward, and the return oil pushed out from the contraction drive oil chamber (8 _S ) of the lift cylinder (8) passes through the return path for rising (D _LU ) and is divided by the shunt valve (17). The flow is divided into the oil tank (13) and the tilt-down pressure feed path (P _TD ) and the contraction drive chamber (1) of the tilt cylinder (14) is fed from the tilt-down pressure feed path.
4 _S ) is press-fitted to contract the tilt cylinder (14),
By tilting the attachment (6) to tilt down, the attachment (6) is configured to be driven in parallel upward movement, and the descending pressure feed path (P _LD ) and the descending position are set to the parallel descending selection position of the drive type selection valve (4). A return path (D _LD ), a tilt-up pressure feed path (P _TU ) and a tilt-up return path (D _TU ) are provided, and the drive type selection valve (4) is placed in the parallel down selection position in the parallel lowering operation state. , Pressure oil supplied from the hydraulic pump to the drive type selection valve (4) through the pressure direction switching valve (3) passes through the descending pressure path (P _LD ) and the contraction drive oil chamber of the lift cylinder (8). The return oil is press-fitted into (8 _S ), contracts the lift cylinder (8), drives the lift arm (5) to descend and swing, and is pushed out from the extension drive oil chamber (8 _L ) of the lift cylinder (8). But the return path (D
_The flow is divided into the oil tank (13) and the tilt-up pressure feed path (P _TU ) by the flow dividing valve (17) through the _LD ), and the tilt drive chamber of the tilt cylinder (14) is extended from the tilt-up pressure feed path (P _TU ). (1
4 _L ) and press it to extend the tilt cylinder (14),
A hydraulic drive circuit for an attachment translational movement operation of an agricultural machine tractor loader, characterized in that the attachment (6) is configured to be tilted up and down to drive the attachment (6) in a parallel downward movement.