JP2563883Y2 - Hydraulic lifting device for work vehicles - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic lifting device for a working vehicle such as a tractor.

[0002]

2. Description of the Related Art
In a working vehicle that raises and lowers the working unit using a hydraulic cylinder, a throttle valve is provided in the hydraulic path to set the rising operation speed of the working unit, but when a throttle valve is provided in the hydraulic path In this case, there is a disadvantage that the pump load increases as the pressure loss increases. Therefore, conventionally, a relief valve is provided in a hydraulic path from a hydraulic pump to a hydraulic cylinder, and excess oil is returned to the tank by the relief valve, thereby avoiding an increase in pump load. However, in the case where the hydraulic path between the relief valve and the hydraulic cylinder is provided with a hydraulic pressure extracting section for branching hydraulic pressure to an attachment or the like, sufficient hydraulic pressure cannot be extracted when the relief valve operates. Therefore, there has been a problem that an attachment or the like that receives a hydraulic pressure supply from the hydraulic pressure take-out unit cannot perform a stable hydraulic operation. Also,
Conventionally, a throttle valve is provided on a control valve that controls the expansion and contraction operation of a hydraulic cylinder, and is configured to be switchable between a low-speed extension operation state via the throttle valve and a high-speed extension operation state bypassing the throttle valve. However, in such a method, there is a single case in which the working section height is automatically controlled as in so-called automatic plowing depth control, and a case in which the operation is switched to a low speed immediately before the stop in order to reduce the shock at the time of ascent and stop. , The operating speed is too high during automatic control, causing a so-called hunting phenomenon (a phenomenon in which the working unit moves up and down because it exceeds the target height), resulting in poor working accuracy, In the case where the impact at the time of stoppage is reduced, the operating speed is too slow, which results in a decrease in work efficiency.

[0003]

SUMMARY OF THE INVENTION The present invention has been conceived in view of the above-described circumstances, and has as its object to provide a hydraulic lifting device for a working vehicle that can eliminate these disadvantages. , a working unit connected to the vehicle body, a single
To lift based on the expansion and contraction operation of Doshiki of the hydraulic cylinder
In the configuration and formed by traveling machine body, an oil passage from the hydraulic pump
To the oil passage below the hydraulic take-out block
A control valve for performing the expansion and contraction operation of the hydraulic cylinder is provided,
A check valve that opens only in the cylinder contraction direction, and a pressure oil that is supplied into the cylinder when the cylinder extends.
Throttle valve to be throttled
The outlet differential pressure overcomes the biasing force of the aforementioned
Above for controlling the cylinder extension velocity comprises a return valve back to the tank the excess oil can not pass through the Riben, the
A lift valve unit is provided . In this case, the ascending valve unit
A switching valve for selectively switching between a low-speed extension operation state via a throttle valve and a high-speed extension operation state bypassing the throttle valve is further provided . The present invention makes it possible to take out a large amount of hydraulic pressure with this configuration. In the case of switching to a low speed, the operation is made as quick as possible to improve the working efficiency.

[0004]

Next, an embodiment of the present invention will be described with reference to the drawings. In the drawings, reference numeral 1 denotes a traveling body of a tractor, and a rotary tilling type working unit 3 is connected to a rear portion of the traveling body 1 via a lifting link mechanism 2 so as to be able to move up and down. The vertical movement of the lift arm 5 based on the expansion and contraction of the single-acting hydraulic cylinder 4 causes the lift arm 5 to move up and down. However, these basic configurations are all conventional.

Reference numeral 6 denotes a hydraulic mechanism provided in the traveling machine body 1. The hydraulic mechanism 6 includes a hydraulic mechanism 7 for elevating and lowering the working unit and a hydraulic mechanism 8 for power steering. A hydraulic pump P for pumping the oil in the hydraulic tank T to a hydraulic path from the tank T to the hydraulic cylinder 4, and surplus oil is supplied to the hydraulic tank T when the pressure in the working unit elevating hydraulic mechanism 7 exceeds a predetermined pressure. A relief valve 9 for returning the hydraulic pressure to the hydraulic cylinder 4, a hydraulic pressure take-out block 10 for supplying hydraulic pressure to the attachment and the like, a control valve 11 for controlling the extending, reducing and stopping operations of the hydraulic cylinder 4, and an oil discharge path for the hydraulic cylinder 4. And a descending speed adjusting valve 12 that can be variably throttled. That is, in the working unit lifting / lowering hydraulic mechanism 7, the hydraulic cylinder 4 is extended by supplying hydraulic pressure to the cylinder based on the switching operation of the control valve 11, while the oil in the cylinder is
The hydraulic cylinder 4 is reduced by permitting discharge by its own weight, and the hydraulic cylinder 4 is stopped by restricting discharge of oil in the cylinder.

Further, reference numeral 13 is provided in the cylinder head 14 of the hydraulic cylinder 4 together with the descending speed adjusting valve 12.
An ascending valve unit, said valve unit 1
3 includes a hollow cylindrical poppet 17 which constitutes a check valve located in a path from the pump port 15 of the cylinder head 14 to the descending speed adjusting valve 12, and the poppet 17 is used when the hydraulic cylinder 4 is contracted. Spring 1
8, while allowing the oil in the cylinder to be discharged by receiving the weight of the working unit, which exceeds the urging force of the working port 8, the pump port 15
The hydraulic path is closed by the hydraulic pressure supplied from the side,
A small-diameter raising orifice 17a (throttle valve) is formed in the poppet 17 to allow the hydraulic pressure to be supplied to the cylinder even in the closed state. The hydraulic cylinder is supplied by supplying hydraulic pressure to the cylinder via the raising orifice 17a. 4 to control the elongation speed.

Further, a spool 19 is provided inside the hollow portion of the poppet 17 so as to be slidable in the axial direction. The spool 19 is urged by a spring 20 in a direction opposite to the poppet 17. Is always tank port T
The communication hole 17b of the poppet 17 communicating with P is closed,
The pressure oil supplied from the pump port 15 is
The spool 19 is connected to the spring 20 via the fiss 17a.
And the orifice 17a
Through the small hole 17c and spool 19
The spool 19 to the biasing force of the spring 20
If the differential pressure with the force on the outlet side that pushes the spring 20 exceeds the biasing force of the spring 20, the spool 19 will move against the spring 20, and in this case, the poppet 17
The hollow portion communicates with the tank port TP through the communication hole 17b to return excess oil to the tank T. That is, if the oil passage is restricted to control the extension operation speed of the hydraulic cylinder 4, excess oil is generated and the pump load increases. However, when this is not an abnormal pressure but a normal pressure range, the relief valve 9 The excess oil is returned to the tank T at a valve unit 13 provided on the lower side of the hydraulic pressure take-out block 10 without activating the valve.

In the embodiment of the present invention constructed as described above, when the hydraulic cylinder 4 is extended, the operating speed is controlled by supplying hydraulic pressure into the cylinder via the throttle valve. The surplus oil generated due to the passage through the valve unit 13 is returned to the tank T in the valve unit 13 provided in the cylinder head 14 without returning to the tank T in the relief valve 9 as in the related art. That is, since excess oil is returned on the lower side of the hydraulic pressure take-out block 10, there is no inconvenience that the relief valve works and a sufficient amount of hydraulic pressure cannot be taken out as in the prior art. As a result, the hydraulic take-off block It is possible to take out a large amount of hydraulic pressure from 10 and to stabilize the hydraulic operation of the attachment receiving the hydraulic pressure . Also, the hydraulic system
The working unit's own weight is
The valve unit is opened to overcome the biasing force of
After all, return oil from the hydraulic cylinder 4 is not throttled.
Therefore, the descent operation is performed by the descent speed adjusting valve 12.
It will not be affected by the downward adjustment.

Furthermore, this means that the return of the surplus oil may perform the two steps in the relief valve 9 and Barubuyunitsuto 13, kill tank load and cylinder actuation also stable.

In addition, the valve unit 13 is not provided with a return valve in the throttle valve, but the valve unit 13 is provided in the cylinder head 14 .
It is possible to measure the downsizing.

The present invention is, of course, not limited to the above-described embodiment. For example, as shown in the second embodiment, the valve unit 13 is set to a low-speed extension operation state through a throttle valve. Alternatively, a switching valve capable of selectively switching between a high-speed extension operation state in which the throttle valve is bypassed may be provided. That is, the poppet 1
A rotatable outer cylinder 21 is provided on the outer periphery of the cylinder 7, and a communication hole 21a for communicating the pump port 15 with the poppet housing and a branch passage 22 of the pump port 15 are communicated with the cylinder chamber. The extension operation speed of the hydraulic cylinder 4 can be switched by providing a communication groove 21b and selecting which one to pass based on the rotation operation of the outer cylinder 21. In this case, since the extension speed setting in the valve unit 13 and the extension speed setting in the control valve 23 can be performed, the rotation of the outer cylinder 21 is controlled by operating the raising / lowering operation lever 24 of the working unit 3 (plowing). (Operation to the deep automatic position) in conjunction with the extension speed set in the valve unit 13 in the plowing depth automatic control, while using the extension speed set in the control valve 23 as the shock buffering speed at the time of stopping the ascent. The condition can be completely satisfied. Therefore, a single operation speed has been adopted in the case where the working unit height is automatically controlled as in the automatic plowing control, and in the case where the operation is switched to a low speed immediately before the stop in order to reduce the shock at the time of ascent and stop. as is conventional, resulting hunting too fast actuation speed during automatic control, also, since that will be erased disintegrated disadvantages such operating speed is too slow in the case to soften the impact at the time of rising is stopped, the working The accuracy and work efficiency can be improved .

In the above embodiment, the lowering speed adjusting valve 12 is provided on the cylinder head 14. However, if the lowering speed adjusting valve 12 is provided on the control valve 25 as shown in the third embodiment, the lowering speed adjusting valve 12 is provided on the cylinder 25. The oil passage of the head 14 can be simplified. That is, in the third embodiment, the return port 26 through which the oil passes only when the hydraulic cylinder 4 is contracted.
In addition, a check valve 27 is provided on the outer peripheral surface of a ball 27a constituting the check valve 27, and a pilot screw 28 is provided on the outer end face.
Is contacted. And Pilot's Screen 28
The speed of the reduction operation can be adjusted by the gap adjustment based on the advance / retreat operation of the above, but in this case, the descent speed adjustment mechanism is provided in the oil passage through which oil passes only during the reduction operation,
The lifting force can be increased by reducing the resistance during the extension operation.

[0013]

[Effects] In summary, since the present invention is constructed as described above, the extension speed of the hydraulic cylinder is controlled.
The lifting valve unit for rolling is
Inside the cylinder head of the hydraulic cylinder below the section
The excess oil is returned to the cylinder head
It will be returned to the tank from the valve. As a result, hydraulic
The surplus oil will be returned on the lower side of the
Therefore, the relief valve works as in the past and a sufficient flow of oil
It can solve the inconvenience of pressure removal
It is possible to extract a large amount of hydraulic pressure from the pressure
The hydraulic operation of the attachment or the like that receives the supply can be stabilized . And this throttle valve opens only in the cylinder contraction direction
The cylinder is reduced due to the check valve.
Sometimes has no effect, and as a result
It will not be damaged. And the return valve is a throttle
The differential pressure between the pressure oil inlet and outlet sides of the valve causes the return valve to close
It opens when you win the energizing armament
Therefore, the extension speed of the hydraulic cylinder
May be used to supply a large amount of pressurized oil.
Will be controlled.

Still further, the cylinder head is provided with a switching valve capable of selectively switching between a low-speed extension operation state through the throttle valve and a high-speed extension operation state bypassing the throttle valve. In this case, the speed can be set in two stages: the setting of the extension speed in the switching valve and the setting of the extension speed in the normally provided control valve.
The speed conditions of both controls can be completely satisfied by using each set extension speed as the extension operation speed in the automatic plowing depth control and the shock buffering speed when the ascent stops. Therefore,
As in the past, a single operating speed was used when automatically controlling the height of the working unit, such as automatic plowing depth control, and when switching the operation to low speed immediately before stopping to reduce the shock at the time of rising and stopping. In the automatic control, the operating speed is too high to cause a hunting phenomenon, and when the shock at the time of rising and stopping is reduced, inconveniences such as the operating speed being too slow are eliminated, thereby improving the work accuracy and work efficiency. Can be improved.

[Brief description of the drawings]

FIG. 1 is a side view of a tractor.

FIG. 2 is a sectional view of a hydraulic cylinder.

FIG. 3 is an enlarged sectional view of a main part of the same.

FIG. 4 is a hydraulic circuit diagram showing the entire hydraulic mechanism.

FIG. 5 is a sectional view of a main part of a second embodiment showing an extended state.

FIG. 6 is a sectional view of the same, showing a contracted state.

FIG. 7A is a sectional view of the same, showing a high-speed extension state;
(B) is a sectional view of the same, showing a low-speed extension state.

FIG. 8 is a hydraulic circuit diagram of a second embodiment.

FIG. 9 is a sectional view of a control valve showing a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Traveling body 3 Working part 4 Hydraulic cylinder 13 Valve unit 14 Cylinder head 17 Poppet 17a Lifting orifice 19 Spool

Claims (2)

(57) [Scope of request for utility model registration] A work unit connected to a traveling body is a single-acting type.
In the traveling machine body configured to move up and down based on the expansion and contraction operation of the hydraulic cylinder, the hydraulic cylinder is installed in the oil passage from the hydraulic pump.
The oil passage below the hydraulic take-off block
A control valve is provided to extend and retract the pressure cylinder.
A check valve that opens only in the cylinder contraction direction, and a pressure oil that is supplied into the cylinder when the cylinder is in extension operation are supplied to the cylinder head of the hydraulic cylinder to which the oil passage from the control valve is connected.
Throttle valve to be throttled
The outlet differential pressure overcomes the biasing force of the aforementioned
Above for controlling the cylinder extension velocity comprises a return valve back to the tank the excess oil can not pass through the Riben, the
A hydraulic lift device for a working vehicle, comprising a lift valve unit . 2. The valve unit according to claim 1, wherein
In the low-speed extension operation state through the throttle valve,
Alternatively, there is further provided a switching valve capable of selectively switching between a high-speed extension operation state in which a throttle valve is bypassed, and a hydraulic lift device for a work vehicle, further comprising: