JPH0749666B2 - Hydraulic drive device capable of translating an attachment of a loader for an agricultural machine tractor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention enables an attachment to be moved in parallel in a loader for agricultural machinery tractors by simply switching the lift operation valve and the tilt operation valve at the same time. Regarding hydraulic drive device, it is a technology that makes it possible to make the tilt cylinder small in diameter, move the attachment in parallel accurately, simplify the hydraulic circuit, and improve the discharge performance of the attachment. .

<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 publications or FIGS. 8 and 9, a hydraulic drive system 2 ′ capable of moving the attachment of the conventional agricultural machine tractor loader 1 in parallel is a lifting or lowering swing operation of the lift arm 5, and an attachment. (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.
While that is pressed into the extended drive oil chamber 8 _L or shortening the drive oil chamber 8 _S of the lift cylinder 8 through pumping path P _LD of _LU or lowered operating position, shortening the drive oil chamber 8 of the lift cylinder 8 _S or extended drive oil chamber 8 _L The pressure oil discharged from the lift control valve 3 passes through the return path D _LU of the lift operation position or the return path D _LD of the lower operation position, and returns to the return oil guide path 9 and the neutral path C _NR of the neutral position of the tilt operation valve 4. After returning to the oil tank 13, the lift cylinder 4 is expanded and contracted to swing the lift arm 5 up and down, and the tilt operation valve 4 is switched while the lift operation valve 3 is in the neutral position. By the hydraulic pump 7
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 is returned to the tilt-up operation position of the tilt operation valve 4 by the return path D _TU.
To the oil tank 13, or return to the oil tank 13 via the return path D _TD of the tilt-down operation position, the return relay path 11, the return path N _DL of the neutral position of the lift operation valve 3 and the return path 12, and the tilt cylinder. The attachment 6 is configured to be tilted up or tilted down by extending and retracting the attachment 14, and the lift operating valve 3 is put in the raising operating position and the tilt operating valve 4 is tilted down as shown in FIG. In the parallel rising operation state in which the hydraulic pump 7 is put into the operating 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 feeding path P _LU of the lifting operation position of the lift operating valve 3 to lift. Cylinder 8 is extended to lift arm 5
The return oil pushed out from the contraction drive oil chamber 8 _{S of} the lift cylinder 8 is returned to the lift operation position of the lift operation valve 3, the return path D _LU , the return oil guide path 9 and the tilt operation valve 4 are tilted down. 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 upward in parallel by swinging the attachment 6 in a tilt-down manner, and as shown in FIG. 9, the lift operation valve 3 is placed in the lowering operation position. In parallel descending operating conditions which supplied the belt operation valve 4 in the tilt-up operating position, it passes through the pumping path P _LD of lowering the operating position of the pressure oil lift operating valve 3 to be discharged from the hydraulic pump 7, the lift cylinder 8 contraction drive 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 pushed out and pushed out from the tilt-down drive oil chamber 14 _{L of} the tilt cylinder 14 is returned to the tilt-up operation position of the tilt operation valve 4 by the return path D _TU , the return oil path 1
After returning to the oil tank 13 via 2, the tilt cylinder 14 is actuated to the tilt-up side to tilt-oscillate the attachment 6 so that the attachment 6 is moved downward in parallel. Further, in the parallel descending state shown in FIG. 9, contrary to the parallel ascending state shown in FIG. 8, the hydraulic oil pushed out from the extension drive oil chamber 8 _L on the side of the lift cylinder 8 having a large cross-sectional area is the tilt cylinder. Shrinkage of the smaller sectional area of 14 Drive side Tilt up drive Oil chamber 14 _S
Since the tilt-up operation speed of the tilt cylinder 14 becomes too fast, the attachment 6 changes from the horizontal posture to the forward upward leaning posture.

In order to eliminate this problem, in the parallel downward movement state, the throttle passage 32 is connected to the check valve 15 of the return oil guide passage 9 in a shunt manner to the return passage D _LD at the lowering operation position of the lift operation valve 2 to lift the lift cylinder. A part of the amount of oil discharged from the extension drive oil chamber 8 _L of No. 8 is released from the throttle passage 32 to the oil tank 13.

<Problems to be Solved by the Invention> The conventional example configured as described above has the following problems (1) to (5).

That is, (1) since the oil chamber on the contraction drive side of the tilt cylinder 14 is the tilt-up drive oil chamber 14 _S and the oil chamber on the extension drive side is the tilt-down drive oil chamber 14 _L ,
Work it is necessary to increase only the cross-sectional area occupied by the piston rod in a tilt-up tilt up driving oil cylinder cross-sectional area required to achieve the force 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) In the parallel rising state shown in FIG. 8, since the entire amount of hydraulic oil pushed out from the contraction drive oil chamber 8 _S of the lift cylinder 8 is press-fitted into the tilt-down drive oil chamber 14 _L of the tilt cylinder 14, The cylinder 14 needs to be as large as the lift cylinder 8.

(3) The distribution of the amount of oil press-fitted into the tilt cylinder 14 and the amount of oil escaped from the throttle passage 32 during the parallel downward movement depends on the pressure of the tilt-up drive oil chamber 14 _S of the tilt cylinder 14 and the throttle diameter of the throttle passage 32. Therefore, if the discharge pressure of the hydraulic pump 7 changes due to a change in the engine speed of the tractor that determines the rotational speed of the hydraulic pump 7, the amount of oil press-fitted into the tilt cylinder 14 and the throttle passage 32 There is a problem that the distribution ratio with respect to the amount of oil to be released 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.

<Means for Solving Problems> The hydraulic drive device capable of moving the attachment of the agricultural machine tractor loader in parallel according to the present invention was proposed for the purpose of solving the above problems. , For example, FIGS. 1 and 2, FIG. 3, FIG. 4, and FIG.
As shown in FIG. 6, FIG. 7, or FIG. 7, the lift operating valve 3 is attached to the hydraulic drive unit 2 of the loader 1 for the agricultural machine tractor.
And a tilt operation valve 4 are provided, the lift cylinder 8 is expanded and contracted by switching the lift operation valve 3, and the lift arm 5 is movable up and down. The tilt cylinder 14 is expanded and contracted by the switching operation of the tilt operation valve 4. It is configured so that the attachment 6 at the tip of the lift arm 5 is driven to tilt and swing, and the lift operating valve 3 is put in the raising operation position and the tilt operating valve 4 is put in the tilt down operating position. Then, the pressure oil discharged from the hydraulic pump 7 is forced into the extension drive oil chamber 8 _L of the lift cylinder 8 through the pressure feed path P _LU at the lift operation position of the lift operation valve 3 to extend the lift cylinder 8 and lift arm. While rocking 5 up,
The return oil pushed out from the contraction drive oil chamber 8 _S of the lift cylinder 8 is the return path D _{LU of} the lift operation valve 3 in the lift operation position, the return oil guide path 9 and the pressure feed path P _{TD of the} tilt operation valve 4 in the tilt down operation position. Through the tilt-down drive oil chamber 14 _L of the tilt cylinder 14, and the tilt cylinder 14 is actuated to the tilt-down side to tilt-oscillate the attachment 6 to move the attachment 6 in parallel. In the parallel lowering operation state in which the lift operating valve 3 is put in the lowering operating position and the tilt operating valve 4 is put in the tilting up operating position, the pressure oil discharged from the hydraulic pump 7 is the lowering operating position of the lift operating valve 3. Through the pressure feeding path P _LD of the lift cylinder 8 and is press-fitted into the contraction drive oil chamber 8 _S of the lift cylinder 8 to contract the lift cylinder 8 and swing the lift arm 5 downward. One
The return oil pushed out from the extension drive oil chamber 8 _L of the lift cylinder 8 is the return path D _{LD at} the lowering operation position of the lift operation valve 3, the return oil guide path 9 and the pressure feed path P _{TU at} the tilt-up operation position of the tilt operation valve 4. Through the tilt-up drive oil chamber 14 _S of the tilt cylinder 14, and the tilt cylinder 14 is actuated to the tilt-up side to tilt-oscillate the attachment 6 so that the attachment 6 is moved in parallel. In the configured hydraulic drive device capable of moving the attachment of the agricultural machine tractor loader in parallel, the tilt cylinder 14 is interlockingly connected to the attachment 6 so as to drive to the tilt-up side during extension operation and to the tilt-down side during contraction operation. Te, with the oil chamber of the extension drive side of the tilt cylinder 14 to tilt up the drive oil chamber 14 _S,
The oil chamber on the contraction drive side is set to the tilt-down drive oil chamber 14 _L , the return oil pressure-fed to the return oil guide passage 9 is diverted by the shunt valve 17, and a part of the oil amount is guided to the tilt operation valve 4. In addition, the balance of the oil amount is returned to the oil tank 13.

<Operation> Since the present invention is configured as described above, it operates as follows.

For example, in the parallel rising operation state shown in FIG. 1, the return oil pushed out from the contraction drive oil chamber 8 _S on the side where the cross-sectional area of the lift cylinder 8 is small is diverted by the shunt valve 17, and a part of the return oil is tilted. The cylinder 14 has a small cross-sectional area and is press-fitted into the tilt-down drive oil chamber 14 _L on the contraction drive side.

Further, for example, in the parallel lowering operation state shown in FIG. 2, the return oil pushed out from the extension drive oil chamber 8 _L on the side where the cross-sectional area of the lift cylinder 8 is large is diverted by the shunt valve, and a part of the return oil is The tilt cylinder 14 has a large cross-sectional area and is press-fitted into the tilt-up drive oil chamber 14 _S on the extension drive side.

As described above, with respect to the cross-sectional area ratio between the contraction drive oil chamber 8 _{S of} the lift cylinder 8 and the tilt-down drive oil chamber 14 _L of the tilt cylinder 14, which exchange the return oil in the parallel rising operation state of FIG. The extension drive oil chamber 8 _{L of} the lift cylinder 8 and the tilt cylinder that exchange the return oil in the parallel descending operation state of FIG.
The cross-sectional area ratio of the tilt-up drive oil chamber 14 _S of 14 becomes almost the same ratio.

As a result, the return oil from the lift cylinder 8 is simply diverted by the shunt valve 17, and a part of the amount of the returned oil is tilted.
Simply press fit into 14 and
Even in the parallel descending operation state of FIG. 2, the attachment 6 is correctly moved in parallel.

<Effects of the Invention> The present invention is configured and operates as described above,
It has the following effects.

A. For example, in both the parallel ascending state shown in FIG. 1 and the parallel descending state shown in FIG. 2, the return oil extruded from the lift cylinder is shunted by the shunt valve, and only part of the return oil is press-fitted into the tilt cylinder. .

As a result, unlike the conventional example shown in FIGS. 8 and 9, it is not necessary to use a tilt cylinder having a size as large as a lift cylinder, and a tilt cylinder having a size small enough to tilt-drive the attachment is used. Just do it.

B. The tilt-up drive oil chamber that receives a larger load than the tilt-down drive oil chamber of the tilt cylinder is composed of the extension drive-side oil chamber, and the piston rod does not pass through. The tilt cylinder can be made small in diameter because the piston rod is not inserted in the cross-sectional area.

C. Even if the discharge pressure of the hydraulic pump changes or the viscosity of the hydraulic oil changes as the engine speed changes,
The return oil from the lift cylinder is always diverted by the shunt valve at a constant flow rate and supplied to the tilt cylinder. Therefore, for example, in both the parallel raising operation state of FIG. 1 and the parallel lowering operation state of FIG. You can always translate correctly.

D. The hydraulic circuit portion that guides the return oil from the lift cylinder to the tilt operation valve from the lift operation valve can have the same circuit configuration in both the parallel ascending operation state of FIG. 1 and the parallel descending operation state of FIG. In comparison with the conventional circuit configuration shown in FIGS. 8 and 9 which requires different circuit configurations, the circuit configuration of the lift operation valve and the hydraulic circuit portion is simplified as apparent from the figures. be able to.

E. Since the tilt-down drive oil chamber of the tilt cylinder is composed of a contraction-drive oil chamber, the cross-sectional area is small as much as the piston rod passes, and the tilt-down drive speed per unit amount of oil is faster. , When the attachment is dump driven by itself, its release performance is high.

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

The hydraulic drive unit 2 of the agricultural machine tractor loader 1 is provided with a lift operation valve 3 and a tilt operation valve 4.

The lift operation valve 3 can be switched between three positions of a neutral position, and an ascending operation position and a descending operation position which are distributed around the neutral position, and the hydraulic pump 7 is compressed at the neutral position. A pressure feed line N _PL connected to
At the raising operation position, the hydraulic pump 7 is connected to the extension drive oil chamber 8 _L of the lift cylinder 8 and the pressure feed passage P _LU is connected, and at the raising operation position, the shortening drive oil chamber 8 _S of the lift cylinder 8 is connected to the return oil guide passage 9. The return path D _LU and the pressure feed path P _LD that connects the hydraulic pump 7 to the shortening drive oil chamber 8 _S of the lift cylinder 8 in the lowering operation position.
And the extension drive oil chamber 8 _L of the lift cylinder 8 at the lowering operation position.
And a return path D _LD which connects to the return oil guide passage 9.

The tilt operation valve 4 can be switched to three positions of a neutral position and a tilt-up operation position and a tilt-down operation position which are distributed to both sides around the neutral position. The tilt operation valve 4 returns through the return oil guide path 9 at the neutral position. Relay path C _NR connected to oil path 12 and return oil guide path 9 at tilt-up operation position
A pumping path P _TU connecting to tilt up the drive oil chamber 14 _S of the tilt cylinder 14, and a return path D _TU to be connected to the oil path 12 returns the tilt-down drive oil chamber 14 _L of the tilt cylinder 14 in the tilt-up operation position , At the tilt down operation position, the return oil guide path 9 is connected to the tilt down drive oil chamber 14 _L of the tilt cylinder 14, and the pressure feed path P _TD and at the tilt down operation position, the tilt up drive oil chamber 14 _S is returned. A return path D _TD connected to the oil path 12 is provided.

The return oil guide passage 9 is provided with a shunt valve 17 for distributing the pressure oil pushed out from the lift cylinder 8 via the lift operation valve 3 to the tilt operation valve 4 and the return oil passage 12 at a constant ratio. To be

The lift cylinder 8 has its end on the contraction drive oil chamber 8 _S side pivotably supported by a base frame 31 fixed to a tractor (not shown), and has its end on the extension drive oil chamber 8 _L side lift shaft. 5 is pivotally supported on the lower side of the middle part of the unit 5. Then, when pressure oil is supplied from the hydraulic pump 7 to the extension drive oil chamber 8 _L , it extends and swings the lift arm 5 upward, and when pressure oil is supplied from the hydraulic pump 7 to the contraction drive oil chamber 8 _S. It contracts to swing the lift arm 5 downward.

The tilt cylinder 14 has its end on the contraction drive oil chamber side pivotally supported so as to be swingable above the tip of the lift arm 5, and its end on the extension drive oil chamber side swings to the lift arm 5. A trunnion is swingably supported at an intermediate portion of a lever 29 that is movably pivoted, and extends when the pressure oil is pressed into the tilt-up drive oil chamber (extension drive oil chamber) 14 _S to move the lever 29 rearward. Link 30 that connects the upper end of the lever 29 and the upper part of the attachment 6 by swinging in the direction (clockwise in the figure).
The attachment 6 is tilted up and rocked through the
When pressure oil is pressed into the tilt-down drive oil chamber (contraction drive oil chamber) 14 _L , it contracts and swings the lever 29 forward,
The attachment 6 is tiltably swingingly driven via the link 30. That is, the tilt cylinder
The reference numeral 14 designates the oil chamber on the extension drive side as the tilt-up drive oil chamber 14 _S and the oil chamber on the contraction drive side as the tilt-down drive oil chamber.
It is set to 14 _L.

According to the hydraulic drive device 2 configured as described above, the lift arm 5 is lifted or swung down, the attachment 6 is tilted up or tilted down, and the lift arm 5 is swung up. When the attachment 6 is operated and automatically tilted down, the attachment 6 is lifted in parallel while keeping the posture of the attachment 6 constant, and the lift arm 5 is lowered and rocked, and the attachment 6 is automatically tilted up. By doing so, a parallel descending movement operation of descending in parallel while keeping the posture of the attachment 6 constant can be performed.

That is, the hydraulic pump 7 is operated by switching the lift operation valve 3 with the tilt operation valve 4 in the neutral position.
While that is pressed into the extended drive oil chamber 8 _L or contraction drive oil chamber 8 _S of the lift cylinder 8 through pumping path P _LD pumping path P _LU or lowered position of the discharged raised position of the lift operating valve 3 pressure oil from, return path D _LD return path D _LU or lowered position of the raised position of the lift operating valve 3 to the hydraulic fluid extruded from a contracted drive oil chamber 8 _S or extended drive oil chamber 8 _L of the lift cylinder 8
Through the return oil guide passage 9, the shunt valve 17 or the relay passage C _NR of the tilt operation valve 4 and the return oil passage 12 to return to the oil tank 13, whereby only the lift cylinder 8 is expanded and contracted to lift the lift arm 5. Can be oscillated up and down.

Further, by switching the tilt operation valve 4 while the lift operation valve 3 is located at the neutral position, the pressure oil discharged from the hydraulic pump 7 is transferred to the neutral position of the lift operation valve 3 by the pressure feed path N _PL and the pressure feed relay. Through the pressure feed path P _{TU at} the tilt up operation position of the tilt operation valve 4 or the pressure feed path P _{TD at the} tilt down operation position of the tilt operation valve 4 into the tilt up drive oil chamber 14 _S or the tilt down drive oil chamber 14 _L of the tilt cylinder 14 On the other hand, the pressure oil pushed out from the tilt-down drive oil chamber 14 _L or the tilt-up drive oil chamber 14 _{S of} the tilt cylinder 14 is returned to the tilt-up operation position return path D _TU or the tilt-down operation position return path D of the tilt operation valve 4. _Pass through the _TD , return to the oil tank 13 via the return oil passage 12, and extend and retract the tilt cylinder 14 to swing the attachment 6 up or down. You can

Here, 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 moved to the tilt-up drive oil chamber. The oil chamber on the contraction drive side is set to 14 _S and the tilt-down drive oil chamber 14
Since the diameter of the tilt-up drive oil chamber 14 _{S that} needs to bear the load of the attachment 6 is set to _L , the oil chamber on the shortening drive side is the tilt-up drive oil chamber 14 _S compared to the chamber 14 _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, it is possible to reduce the size and cost reduction of the tilt cylinder 14.

Further, 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 drive the tilt-down side during the contraction operation, and the oil chamber on the extension driving side of the tilt cylinder 14 is tilted up to drive the oil chamber 14 _S. And the oil chamber on the contraction drive side is tilted down to drive the oil chamber 14 _L
Since then are, tilt cylinder corresponding to the volume occupied by the piston rod in a tilt-down drive oil chamber 14 _L as compared with the conventional tilt cylinder 14 that is the oil chamber contraction drive side to the tilt-down drive oil chamber 14 _S The contraction speed of 14 can be made higher than the expansion speed of the tilt cylinder 14.

Further, as shown in FIG. 1, in the parallel ascending operation state in which the lift operating valve 3 is put in the raising operation position and the tilt operating valve 4 is put in the tilt down operating position, the pressure oil discharged from the hydraulic pump 7 is lifted. The lift cylinder 5 is press-fitted into the extension drive oil chamber 8 _L of the lift cylinder 8 through the pressure feed path P _{LU at} the raising operation position of the operation valve 3 to extend the lift cylinder 8 to swing the lift arm 5 upward, while the contraction drive of the lift cylinder 8 is performed. The return oil pushed out from the oil chamber 8 _S passes through the return passage D _LU of the lift operation valve 3 in the raising operation position, the return oil guide passage 9 and the pressure feed passage P _TD in the tilt down operation position of the tilt operation valve 4 and the tilt cylinder 14 thereby pressed into the tilt-down drive oil chamber 14 _L, tilting up the drive oil chamber of the tilt cylinder 14
The pressure oil pushed out from 14 _S is returned to the oil tank 13 via the return path D _TD of the tilt down operation position of the tilt operation valve 4 and the return oil path 12, and the tilt cylinder 14 is operated to the tilt down side to tilt the attachment 6. The attachment 6 can be moved upward in parallel by driving it to swing down.

Furthermore, as shown in FIG. 2, in the parallel lowering operation state in which the lift operation valve 3 is put in the lowering operation position and the tilt operation valve 4 is put in the tilting up operation position, the pressure oil discharged from the hydraulic pump 7 is through the pumping path P _LD in lowering operation position of the lift operating valve 3, it is pressed into the reduced drive oil chamber 8 _S of the lift cylinder 8, while lowering rocking the lift arm 5 to contract the lift cylinder 8, the lift cylinder 8
The return oil pushed out of the extension drive oil chamber 8 _L of the lift operation valve 3 is returned to the lowering position of the lift operation valve D _LD , the diversion valve 17 and the check valve 1.
While passing through the return oil guide passage 9 and the pressure feed passage P _TU at the tilt-up operation position of the tilt operation valve 4 with the 5, 5 interposed, the oil is pressed into the tilt-up drive oil chamber 14 _S of the tilt cylinder 14 and the tilt cylinder 14 The pressure oil pushed out from the tilt-down drive oil chamber 14 _L is returned to the oil tank 13 via the return path D _TU of the tilt-up operation position of the tilt operation valve 4 and the return oil path 12, and the tilt cylinder 14 is operated to the tilt-up side. By tilting the attachment 6 to swing it up, the attachment 6 can be moved downward in parallel.

As described above, the tilt cylinder 14 is attached to the attachment 6
To, to tilt up side during extended operation, is operatively connected to drive the tilt-down side during contraction operation, the oil chamber of the extension drive side of the tilt cylinder 14 tilting up drive oil chamber 14 _S
In addition, since the oil chamber on the contraction drive side is set to the tilt-down drive oil chamber 14 _L , the diameter of the tilt-up drive oil chamber 14 _{S that} needs to bear the load of the attachment 6 is shortened. the compared with the conventional tilt-up drive oil chamber 14 _S that is in the tilt-up drive oil chamber 14 _S, can be reduced to correspond to the cross-sectional area of the piston rod has been occupied by the conventional tilt-up drive oil chamber 14 _S, Tilt cylinder 14
It is possible to reduce the size and cost of the device.

Further, the size and cost of the lift cylinder 8 can be reduced corresponding to the size reduction of the tilt cylinder 14.

Further, since the attachment 6 is configured to tilt up when the tilt cylinder 14 is extended,
The contraction speed of the tilt cylinder 14 becomes faster than the extension speed of the tilt cylinder 14 by an amount corresponding to the volume occupied by the piston rod in the tilt-down cylinder chamber 14 _L , and the discharging performance at the time of damping becomes high.

Furthermore, the return oil tilt cylinder in parallel upward movement operation state extruded from the contracted drive oil chamber 8 _S of the lift cylinder 8
The tilt-down drive oil chamber 14 _{L of} the tilt cylinder 14, that is, the return oil that is press-fitted into the contraction drive-side oil chamber and is pushed out from the extension drive oil chamber 8 _L of the lift cylinder 8 in the parallel downward movement operation state is tilted up. Since it is adapted to be press-fitted into the drive oil chamber 14 _S , that is, the oil chamber on the extension drive side, the tilt cylinder out of the pressure oil discharged from the lift cylinder 8 in the parallel ascending movement operation state and the parallel descending movement operation state. It is possible to make the distribution ratio of the pressure oil divided to 14 the same and to provide the return oil guide passage 9 from the lift cylinder 8 to the tilt cylinder 14 with a distribution valve 17 having a constant distribution ratio. Throttle passage 32 to switch the amount of oil press-fitted into 14
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, and as a result, the circuit configuration of the hydraulic drive system 2 can be simplified.

Further, the distribution of the amount of oil press-fitted into the tilt cylinder 14 and the amount of oil returned to the oil tank does not depend on the throttle passage 32 in which the flow rate changes due to the discharge pressure of the hydraulic pump 7 or the load on the attach mechanism 6, and thus the flow is divided. As it is composed of valve 17,
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 can be made 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.

<Embodiment 2> In another embodiment of the present invention shown in FIG. 3, an ascending speed increasing valve 18 is provided in addition to the above embodiment. The rising speed increases valve 18, the lift cylinder is introduced into the pressure oil extension drive oil chamber 8 _L extruded from a contracted drive oil chamber 8 _S silt cylinder 8 by switching operation, as necessary, when parallel upward movement operation The extension speed of the lift arm 5 is increased to increase the lift speed of the lift arm 5.

Further, in this embodiment, a bypass valve 19 is provided. This bypass valve 19 is a lift cylinder 8 and a tilt cylinder.
By switching operation as necessary during the combined operation of operating the 14 operation, the upstream side portion and the downstream side portion of the diversion valve 17 of the return oil guide passage 9 are communicated with each other, and a part of the pressure oil is not released from the diversion valve 17. The entire amount of pressure oil discharged from the hydraulic pump 7 is pressure-fed to the tilt cylinder 14, and the pressure oil discharged from the hydraulic pump 7 can be used for tilt-up operation or tilt-down operation without waste.

Further, in this embodiment, an automatic horizontal return operation valve 20 is provided. This automatic horizontal return operation valve 20 is switched as necessary when the lift arm 5 is swung up and the attachment 6 is tilted down for damping from a high position, and then the parallel down movement operation is performed. by operating further drive to the tilt-up side of the parallel descending drive state the tilt cylinder 14 to guide the pressure oil to be extruded in the tilt-up drive oil chamber 14 _S from the tilt-down drive oil chamber 14 _L of the tilt cylinder 14, The attachment 6 is in a horizontal state when the lift arm 5 is lowered to a low position (here, the state where the rake surface of the bucket is parallel to the ground).
It is designed to be tilted up to.

The automatic horizontal return operation valve 20, as shown in FIG. 4, may be obtained by incorporating a shunt circuit 20a for distributing the hydraulic fluid extruded from the tilt-down drive oil chamber 14 _L at a predetermined ratio. In this case, becomes parallel downward movement operation when the flow rate of the hydraulic fluid lowering speed of the lift arm is pushed out from the slow tilt-down drive oil chamber 14 _L is small, the lowering speed is fast tilt-down drive oil chamber 14 of the lift arm 5 _L When the flow rate of the pressure oil pushed out from is large, the attachment 6 is automatically tilted up to the horizontal state.

Furthermore, in this embodiment, a brake valve for preventing the attachment 6 from tilting down due to a load.
21 are provided. The brake valve 21 is an on-off valve 22 which is closed when the internal pressure of the tilt-down drive oil chamber 14 _L of the tilt cylinder 14 becomes a predetermined value or less and prevents the pressure oil from being pushed out of the tilt-up drive oil chamber 14 _S. , And a check valve 23 connected in parallel with the tilt-up drive oil chamber 14 _S to allow pressure oil to be pressed into the tilt-up drive oil chamber 14 _S. The structure of the brake valve 21 is not limited to this embodiment, and the brake valve 21 can be composed of a normal throttle valve, for example.

A relief valve 24 is provided at a portion of the return oil passage 9 upstream of the flow dividing valve 17.
Are connected. As a result, since the return oil from the lift cylinder 8 is returned from the relief valve 24 to the oil tank 13 when the tilt cylinder 14 reaches the stroke end during the parallel movement of the attachment 6, the lift arm 5 is It can be moved further.

In addition, an on-off valve 25 for floating operation is provided. When the lift operation valve 3 is located at the lowering operation position and the opening / closing valve 25 is opened, the pressure oil that has passed through the pressure feed path P _LD of the lift operation valve 3 escapes to the tilt operation valve 4 side, and the lift cylinder 8
Becomes floating.

When the tilt cylinder 4 is set to the neutral position and the opening / closing valve 25 is opened, the lift cylinder 8 operates as a single acting cylinder.

<Embodiment 3> In yet another embodiment of the present invention shown in FIG. 5, the lift control valve 3 has an internal pressure in the pressure feed passage N _PL in the neutral position, the return passage D _{LU in the} raised position or the return passage D _{LD in} the lowered position. A brake valve 26 pilot-operated by is provided. In FIG. 5, in order to clearly show the flow path for supplying the pilot operation pressure to the brake valve 26 at each position of the lift operation valve 3, the relay path N _CL at the neutral position, the relay path C _{LU at the} ascending operation position and the descending operation are shown. Although it is illustrated that the brake valve 26 is interposed in each of the relay paths C _LD at the positions, one brake valve 26 is actually provided.

The brake valve 26 is provided on the return path of the lift operation valve 3 when the lift operation valve 3 is located at the up position or the down position and the tilt operation valve 4 is located at the tilt down operation position.
The valve is closed when the internal pressure of D _LU or the return path D _LD is less than or equal to a predetermined value, the pressure oil is prevented from being pushed out of the tilt-up drive oil chamber 14 _{S of the} tilt cylinder 14, and the attachment 6 swings to the tilt-down side. Is prevented. Lift operation valve 3
Is located in the neutral position, the relay path N
The tilt-up drive oil chamber 14 _{S of the} tilt cylinder 14 is communicated with the oil tank 13 via the return path N _DL in the neutral position that bypasses _CL , and the tilt cylinder 14 can be freely expanded and contracted.

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

<Embodiment 4> Another embodiment of the present invention shown in FIG. 6 is a brake in which the lift operation valve 3 and the tilt operation valve 4 are each formed of a dedicated valve, and the attachment 6 is prevented from tilting down. It is essentially the same as the one embodiment described above except that the valve 28 is a throttle valve.

<Fifth Embodiment> In each of the first to fourth embodiments described above, the tilt cylinder 14 is arranged above the lift arm 5, but as shown in FIG. 7, the tilt cylinder 14 is arranged below the lift arm 5. You may arrange. In this case, an intermediate portion of the bar 29 is pivotally supported by the lift arm 5, and an end portion of the tilt cylinder 14 on the tilt-down drive oil chamber 14 _L side is swingably connected to a lower end portion thereof.
The upper portion of the attachment 6 is connected to the upper end of the attachment 6 via a link 30. An end of the tilt cylinder 14 on the tilt-up drive oil chamber 14 _S side is pivotally supported below the intermediate portion of the lift arm 5 so as to be swingable. The rest of the configuration is essentially the same as that of the above-mentioned embodiment, and therefore its explanation is omitted.

In each of the above-described embodiments, the return oil that is pressure-fed to the return oil guide passage 9 is diverted by the shunt valve 17, a part of the shunt is guided to the tilt operation valve 4, and the remaining amount of the oil is returned to the return oil passage 12. It is configured to be returned to the oil tank 13 via the flow path, but the rest of the oil amount is returned from the shunt valve 17 to the neutral oil passage connected downstream of the hydraulic circuit 2 of the loader, and returned from the neutral oil passage to the oil tank 13. It may be configured as follows.

Further, the lift operation valve 3 is composed of a three-position switching valve, but it may be composed of a four-position switching valve including a floating position.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of an embodiment of the present invention in a parallel ascending movement operation state, FIG. 2 is a hydraulic circuit diagram of an embodiment of the present invention in a parallel descending drive operation state, and FIG. FIG. 4 is a hydraulic circuit diagram of another embodiment of the present invention, and FIG. 4 is an automatic horizontal return operation valve 20 of FIG.
Fig. 5 is a hydraulic circuit diagram showing a modified example of Fig. 5, Fig. 5 is a hydraulic circuit of another embodiment of the present invention, Fig. 6 is a hydraulic circuit diagram of another embodiment of the present invention, and Fig. 7 is a tilt of the present invention. FIG. 8 is a hydraulic circuit diagram showing a modified example of a cylinder mounting structure, FIG. 8 is a hydraulic circuit diagram of a conventional example in a parallel ascending movement operation state, and FIG. 9 is a hydraulic circuit diagram of a conventional example in a parallel descending drive operation state. . 1 ... loader, 2 ... hydraulic drive device, 3 ... lift operating valve, 4 ... tilt operating 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, 13 ... Oil tank, 14 ... Tilt cylinder, 14 _L ... Tilt down drive oil path, 14 _S ... Tilt up drive oil path, 17 ... Dividing valve, P _LD ... Lift operation Pumping path for the lowering operation position of the valve 3, P _LU ...... Pressing path for the lifting operation position of the lift operating valve 3, D _LD ...... Return path for the lowering operation position of the lift operating valve 3, D _LU ...... Lift operating valve 3 Return path of the rising operation position of P _TD , the pressure feeding path of the lowering operation position of the tilt operation valve 4, P _TU: The pressure feeding path of the rising operation position of the tilt operation valve 4.

Claims (1)

[Claims] 1. A lift operating valve 3 and a tilt operating valve 4 are provided in a hydraulic drive unit 2 of an agricultural machine tractor loader 1, and a lift cylinder 5 is extended and contracted by a switching operation of the lift operating valve 3 to lift a lift arm 5. The tilt operation valve 4 is configured to be movable up and down, and the tilt cylinder 14 is expanded and contracted by a switching operation of the tilt operation valve 4 so that the attachment 6 at the tip of the lift arm 5 is tilt-oscillated. Pressure oil discharged from the hydraulic pump 7 passes through the pressure feed path P _LU at the lift operation position of the lift operation valve 3 in the parallel lift operation state in which the tilt operation valve 4 is moved to the tilt down operation position and the tilt cylinder is lifted. 8 is press-fitted into the extension drive oil chamber 8 _L to extend the lift cylinder 8 and swing the lift arm 5 upward,
The return oil pushed out from the contraction drive oil chamber 8 _S of the lift cylinder 8 is the return path D _{LU of} the lift operation valve 3 in the lift operation position, the return oil guide path 9 and the pressure feed path P _{TD of the} tilt operation valve 4 in the tilt down operation position. Through the tilt-down drive oil chamber 14 _L of the tilt cylinder 14, and the tilt cylinder 14 is actuated to the tilt-down side to tilt-oscillate the attachment 6 to move the attachment 6 in parallel. In the parallel lowering operation state in which the lift operating valve 3 is put in the lowering operating position and the tilt operating valve 4 is put in the tilting up operating position, the pressure oil discharged from the hydraulic pump 7 is the lowering operating position of the lift operating valve 3. Through the pressure feeding path P _LD of the lift cylinder 8 and is press-fitted into the contraction drive oil chamber 8 _S of the lift cylinder 8 to contract the lift cylinder 8 and swing the lift arm 5 downward. One
The return oil pushed out from the extension drive oil chamber 8 _L of the lift cylinder 8 is the return path D _{LD at} the lowering operation position of the lift operation valve 3, the return oil guide path 9 and the pressure feed path P _{TU at} the tilt-up operation position of the tilt operation valve 4. Through the tilt-up drive oil chamber 14 _S of the tilt cylinder 14, and the tilt cylinder 14 is actuated to the tilt-up side to tilt-oscillate the attachment 6 so that the attachment 6 is moved in parallel. In the configured hydraulic drive device capable of moving the attachment of the agricultural machine tractor loader in parallel, the tilt cylinder 14 is interlockingly connected to the attachment 6 so as to drive to the tilt-up side during extension operation and to the tilt-down side during contraction operation. Te, with the oil chamber of the extension drive side of the tilt cylinder 14 to tilt up the drive oil chamber 14 _S,
The oil chamber on the contraction drive side is set to the tilt-down drive oil chamber 14 _L , the return oil pressure-fed to the return oil guide passage 9 is diverted by the shunt valve 17, and a part of the oil amount is guided to the tilt operation valve 4. In addition, the hydraulic drive device capable of moving the attachment of the agricultural machine tractor loader in parallel is characterized in that the remaining amount of the oil is returned to the oil tank 13.