JPS6131244Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an automatic transmission valve in a hydraulic drive system.

A hydraulic drive device in which a variable pump and a variable motor are connected in a closed circuit and the variable motor drives a traveling body is equipped with a servo cylinder to control the discharge direction and discharge amount of the variable pump. The pressure oil discharged from the control pump driven by the engine is supplied by the forward/reverse speed control valve.

Then, between the control pump and the forward/reverse speed control valve, when the engine speed decreases, the supply pressure to the servo cylinder is reduced, the discharge amount of the variable pump is reduced, the engine speed is restored, and the load is adjusted. It is equipped with an automatic transmission valve that keeps the engine speed constant.

As this automatic transmission valve, one has been proposed in which the output pressure is controlled by utilizing the pressure difference before and after the throttle provided in the discharge passage of the control pump.

However, with these structures, if the differential pressure is small, the operation becomes uncertain, and if the load changes again before the differential pressure changes and the operation has not finished, the device cannot operate quickly and a time delay occurs. This has the problem of poor responsiveness.

The present invention was developed in view of the above circumstances, and its purpose is to be able to control the output pressure using the differential pressure before and after the throttle provided in the discharge path of the control pump, and to ensure reliable operation even when the differential pressure is small. Furthermore, it is an object of the present invention to provide an automatic transmission valve for a hydraulic drive device that can operate without any time delay and has good responsiveness when the load changes again during the end of the operation when the differential pressure changes.

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

The hydraulic drive device A connects a variable pump 1 driven by an engine E and a variable motor 2 in a closed circuit via main circuits 3 and 4, so that the variable motor 2 drives a traveling body (not shown). 1, the discharge direction and discharge amount are controlled by a servo cylinder 5, and the discharge pressure of a control pump 6 driven by the engine E is applied to the servo cylinder 5 via an automatic transmission valve 7 and a forward/reverse speed control valve 8. Supply controlled.

The automatic transmission valve 7 includes a valve body 9.
A valve hole 10 is bored in the valve hole 10, first, second, third, and fourth ports 11, 12, 13, and 14 are formed in the valve hole 10, and a spool 15 is inserted into the valve hole 10,
The spool 15 has a first port 11 and a second port 1.
A notch 16 is formed to allow the passage between the two.

The first port 11 is connected to the inlet port 8a of the forward/reverse speed control 8 via the first passage 17.
The second port 12 is connected to the discharge passage 6a of the control pump 6, and the third port 13 is spool 1
The fourth port 14 is connected to the discharge passage 6a of the control pump 6 through a second passage 21 which is open to the other end surface 15a of the control pump 6 and is equipped with a throttle 20.
It is connected to.

A first load piston 22 is in contact with one end surface 15a of the spool 15, and its pressure receiving chamber 23 is connected to the discharge passage 6a.
A second load piston 24 is in contact with the other end surface 15b, and its pressure receiving chamber 25 is open to the fourth port 14.

26 is a pressure accumulator, and a spool 28 is inserted into the valve hole 27 of the valve body 9 and pushed in one direction by a spring 29 to form a pressure receiving chamber 30 that resists the spring force. It has a structure in which two passages 21 are connected. In addition, 31 connects the spring chamber 32 to the drain 3
This is the drain port connected to 3.

The discharge passage 6a is provided with a variable throttle 35 and a relief valve 36 linked to the rotation speed control lever 34 of the engine E.
The pressure receiving chamber 23 is connected to the downstream side of the variable throttle 35, and the pressure receiving chamber 25 is connected to the upstream side of the variable throttle 35.

Therefore, the pressure P ₁ in the pressure receiving chamber 23 is lower than the pressure P ₂ in the pressure receiving chamber 24 by the pressure drop of the variable throttle 35, and the pressure P 3 of the first port 11 (that is, the output pressure) is lower than the pressure P ₂ of the pressure receiving chamber 24. The spool 15 is moved to the left by acting on both end surfaces 15a and 15b, and the first port 11 and the second port 12 are communicated with each other through the notch 16.

In this state, when the load on the hydraulic drive device A increases and the pressure in the main circuits 3 and 4 rises rapidly, the rotational resistance of the variable pump 1 increases, the load on the engine E increases, and the rotation of the engine E decreases. .

As a result, the rotation of the control pump 6 is reduced and the discharge amount is reduced, so that the pressure difference (differential pressure) before and after the variable orifice 35 is reduced. On the other hand, since the pressure P ₁ in the pressure receiving chamber 23 is set to a constant pressure by the relief valve 36, when the differential pressure decreases, the pressure in the pressure receiving chamber 25 increases.
_P2 decreases.

This causes the pressure acting on the spool 15 to become unbalanced, causing the spool 15 to move to the right.
The opening area of the first port 11 and the second port 12 decreases, and the pressure of the first port 11, that is, the output pressure _P3 decreases.

This output pressure acts on one end surface 15a of the spool (that is, back pressure chamber A) through the hole 18 and the blind hole 19, and acts on the other end surface 15b of the spool (that is, back pressure chamber B) through the throttle 20. Since the pressure stored in the pressure receiving chamber 30 of the pressure accumulator 26 acts on the chamber ₂₆ , the pressure decreases with a certain time delay compared to the decrease in the output pressure P3.

Therefore, immediately after the output pressure _P3 suddenly decreases, the pressure in the back pressure chamber A becomes lower than the pressure in the back pressure chamber B, and there is no force to move the spool 15 to the right, and the spool 15 stops at that position, and the decrease in output pressure _P3 is suppressed to a certain value.

Then, as time passes, the pressure in the back pressure chamber B decreases and approaches the pressure in the back pressure chamber A, so the spool 15 moves further to the right and the output pressure _P3 gradually decreases. When the pressure in the pressure chamber B becomes the same, the spool 15 stops and the output pressure _P3 becomes constant.

On the other hand, when the output pressure _P3 decreases, the servo cylinder 5
Since the pressure of the variable pump 1 decreases, the discharge amount of the variable pump 1 decreases and the engine rotation increases, so the differential pressure gradually increases.

That is, when the load suddenly increases, the spool 15 moves to the right, lowers the output pressure _P3 , and sets the engine speed to a value corresponding to the load, thereby making effective use of the engine output and preventing the engine from stopping.

The above-mentioned situation is illustrated in a table as shown in FIG.

Note that when the load decreases and the engine rotation increases, the output pressure _P3 is increased by operating in the opposite manner to the above, and is set to the best engine rotation speed corresponding to the load.

Also, due to the differential pressure, the first and second ports 11 and 12
Since it directly operates the spool 15 that disconnects the
The spool 15 moves according to the pressure difference to the first and second
The opening area of ports 11 and 12 can be controlled.

Therefore, as shown in the third diagram, even if the width of the differential pressure is small, the output pressure can be controlled as shown in d. It becomes different like t and t.

Also, when the differential pressure decreases, the spool 15 moves to the right and reduces the output pressure _P3 , but since the back pressures acting on both end surfaces 15a and 15b of the spool 15 are different, the moving speed of the spool 15 slows down. The output pressure P ₃ begins to gradually decrease, and when the differential pressure further decreases during this decrease, the balance of the forces acting on the spool 15 collapses and the spool 15 begins to move even more rapidly to the right.

Therefore, even if the differential pressure changes stepwise in a short period of time as shown in FIG. 4, the output pressure changes rapidly without delay in response to the change in differential pressure.

The present invention is as described above, and the throttle 3
When the differential pressure around 5 changes, the output pressure _P3 can be increased or decreased to lower the pressure to the servo cylinder 5 and control the engine speed according to the load.
5 is directly moved by the differential pressure, it operates reliably even when the differential pressure is small, and there is no time delay even if the load fluctuates further before the output pressure _P3 control ends due to load fluctuation. The output pressure _P3 can be controlled immediately without any problems, and the response is good.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention;
3 and 4 are tables explaining the operation. 1 is a variable pump, 2 is a motor, 5 is a servo cylinder, 6 is a control pump, 7 is an automatic transmission valve, 8 is a forward/reverse speed valve, 9 is a valve body, 11 is an outlet port, 12 is an inlet port, 15 is a Spool, 2
0 is the throttle, 26 is the pressure accumulation chamber, 35 is the throttle, and E is the engine.

Claims (1)

[Scope of utility model registration request] The motor 2 is driven by the variable pump 1 driven by the engine E, and the discharge amount of the variable pump 1 is
The discharge direction is changed by a servo cylinder 5, and the discharge pressure oil of a control pump 6 driven by the engine E is supplied to the servo cylinder 5 via an automatic transmission valve 7 and a forward/reverse speed valve 8. In the hydraulic drive device, the valve body 9 of the automatic transmission valve 7 has an inlet port 12 and an outlet port 11.
A spool 15 is provided to control the opening area of the spool 15, and an outlet port 11 is provided on one end surface 15a of the spool 15.
The pressure of the outlet port 11 is supplied to the other end face 15b through a throttle 20 and connected to the pressure accumulator 26, and a throttle 35 is provided in the discharge passage 6a of the control pump 6. The inlet port 12 and the outlet port 11 are connected to the spool 15 on the inflow side.
The outflow side is connected to the pressure receiving chamber 25 that applies a moving force in the direction of increasing the opening area, and the outflow side is connected to the spool 1.
Pressure receiving chamber 2 that applies a driving force in the direction of reducing the opening area of the inlet port 12 and the outlet port 11 to the pressure receiving chamber 5
3. An automatic transmission valve for a hydraulic drive device, characterized in that the automatic transmission valve is connected to a hydraulic drive device.