JPS60245804A - Control circuit for variable capacity pump - Google Patents

Abstract

PURPOSE:To reduce the number of parts in control circuit thus to reduce the size by varying the opening area of orifice through manual changeover valve and leading the pilot pressure produced across said orifice to a regulator for setting the inclination angle of pump. CONSTITUTION:The control port 11a of manual changeover valve 11 will constitute a variable orifice for varying the opening with correspondence to the movement of spool section 11h of said valve 11. Upon switching of said valve 11 from neutral position to the left or right, pilot pressure is produced in a branch path 15 in the upstream of said valve 11 while corresponding with the changing amount. Said pilot pressure is led to a regulator 19 and functions to vary the delivery of variable capacity pump P1.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a control circuit that controls the discharge amount of a variable displacement pump according to the operation amount of a switching valve. It is ideal for construction vehicles and the like that control the operating speed of the actuator.

(Prior Art) As this type of control circuit, the one disclosed in Japanese Patent Application Laid-Open No. 131303/1983 has been known.

The biggest feature of this conventional control circuit is that the manually operated switching valve is equipped with a cam mechanism, and by operating the switching valve,
The point is that the pressure reducing valve is operated by the above cam mechanism.

FIG. 3 shows an application example in which a control circuit is constructed by combining a pilot operated switching valve and the conventional manually operated switching valve.

A manually operated switching valve 1 and a pilot operated switching valve 2 are connected in parallel to the variable displacement pump P1 of FIG.

Then, the pyro chamber 2 of the pilot operation switching valve 2 is
Each of a and 2b is a pressure reducing valve 3 of a pilot operated valve 3.
Connected to secondary boats a and 3b. This pressure reducing valve 3
The primary boats a and 3b are connected to a constant discharge pilot pump P2 via a passage 4.

Therefore, when the lever 3c of the pilot operating valve 3 is tilted to either the left or right, one of the pressure reducing valves is activated, and the pilot pressure is adjusted according to the inclination angle of the operating lever 3c described in -1-, that is, the amount of operation thereof. Occurs on the secondary boat. The pilot pressure generated in this secondary boat is the pilot chamber 2a or 2b of the pilot I/switching valve 2.
The pilot operated switching valve 2 is switched by an amount proportional to the pilot pressure.

The manually operated switching valve 1 also has a spool portion 1.
A cam mechanism 5 that interlocks with a is provided.

Then, the primary boat of the pressure reducing valve 6 is connected to the passage 4, and the piston 6b provided at the tip of the pressure setting spring 6a of the pressure reducing valve 6 is connected to the cam groove 5 of the cam mechanism 5.
It is in contact with a.

Therefore, when the manually operated switching valve 1 is switched to either the left or right side, the cam mechanism 5 moves accordingly, and the piston 6b moves along the cam groove 5a to compress the spring 6a. Pilot pressure is generated in the secondary boat of the pressure reducing valve 6 in response to the spring force of the compressed spring 6a.

And the pilot chamber 2 of the pilot operation switching valve 2
The highest pressure of the pilot pressure acting on a and 2b and the pilot pressure generated in the secondary boat of the pressure reducing valve 6 is,
It is selected by the shuttle valve 7.8 and acts on the regulator 9 which adjusts the tilting angle of the variable displacement pump P. When the pilot pressure acts on the regulator 9 of the variable displacement pump PI in this manner, the discharge amount of the variable displacement pump P is increased by an amount corresponding to the pilot pressure.

In addition, the reference numeral 10 in the figure is an unload valve, and the regulator 9
When no pilot pressure acts on the variable displacement pump P,
This is to offload the minimum discharge amount.

(Problems to be Solved by the Present Invention) - In the conventional control circuit as described above, the cam mechanism 5 must be provided in the manually operated switching valve 1, and furthermore, the cam mechanism 5 must be connected to the cam mechanism 5. A working pressure reducing valve 6 must be specially provided.

However, as mentioned above, since the cam mechanism 5 and the pressure reducing valve 6 are required, there is a drawback that the number of parts increases, and furthermore, there is also a drawback that the entire size increases accordingly.

This invention eliminates the need for the cam mechanism 5 and pressure reducing valve 6,
The purpose of the present invention is to provide a control circuit that reduces the number of parts and enables miniaturization.

(Structure of the present invention) In order to achieve the above object, the present invention connects a manually operated switching valve and a pilot operated switching valve to a variable displacement pump, and a pilot chamber of the pilot operated switching valve is provided with a pilot operated switching valve.・The pilot pressure generated in proportion to the amount of operation of the pilot operated valve connected to the engine pump is guided, while the manually operated switching valve is opened to the maximum when the manual switching valve is in the neutral position. A variable orifice that reduces the amount of melon opening according to the amount of switching is provided, and the pilot pump is communicated with the tank through this variable orifice, and the pilot pressure that acts on the pilot-operated switching valve and the manually-operated switching valve are switched to make it variable. The higher of the pilot pressures generated by narrowing the orifice is set as the variable displacement pump's rectifier.
/-A configuration that works in the evening is adopted.

(Operation of the present invention) Since the configuration is as described in -, the opening area of the variable orifice is determined by switching the manually operated switching valve, and the pyrotron is installed before and after the variable orifice according to this opening area. Pressure is generated. The pilot pressure thus generated acts on a regulator that adjusts the tilt angle of the variable displacement pump.

Further, when the pilot operation valve is operated, a pilot operation switching valve is generated and the pilot operation switching valve is switched, and this pilot pressure acts on the regulator to control the discharge amount of the variable displacement pump.

Furthermore, when both switching valves are operated simultaneously, the higher pilot pressure generated at that time acts on the regulator, and according to this higher pilot pressure,
The discharge amount of the variable displacement pump is controlled.

(Embodiment of the present invention) A manually operated switching valve 11 and a pilot operated switching valve 12 are connected in parallel to the variable displacement pump P in the embodiment shown in FIG.

Then, the pilot chambers +2a, 12b of the pilot operation switching valve 12 are connected to the pressure reducing valve 13 of the pilot operation valve 13.
Although it is connected to the secondary side boats 13a and 13b, this pilot operated valve 13 is completely the same as the conventional one.

In other words, this viroft operation valve 13 is the pressure reducing valve 13
The primary ports of a and 13b are connected via a passage 14 to a constant discharge pilot pump P2.

A constant pressure relief valve V is connected to the passage 14,
The pressure in this passage 14 is always kept constant. Therefore, when the operating lever +3c is operated, a pilot pressure proportional to the operating amount is generated in the secondary boat and acts on either the pilot chamber +2a or 12b.

A branch passage 15 branched off from the passage 14 is provided with a fixed throttle 16, and the downstream side of the fixed throttle 16 is communicated with the tank T via the control valve hlla of the manually operated switching valve 11. There is. And this control bow)
The control boat 11a opens to the maximum when the manually operated switching valve 11 is in the neutral position shown in the figure, and gradually closes when the manually operated switching valve 11 is switched. Spool portion 11 of operation switching valve 11
A variable orifice whose opening degree is changed according to the amount of movement of b is configured. However, in this embodiment, the variable orifice, ie, the control bow Nla, is set to a size such that the pressure in the branch passage 15 is approximately equal to the tank pressure when the variable orifice is fully open.

Since the fixed throttle 16 is provided in the branch passage 15 as described above, even if the control valve 11a is fully open, the pressure on the passage 14 side is always maintained at a constant pressure by the action of the constant pressure relief valve V. be done.

Then, in the branch passage 15, the pressure oil whose pressure has been dropped by the fixed throttle 16 enters the branch passage 15, but the pressure in this branch passage 15 is
It changes depending on the switching amount of the manual switching valve 11.

This is because the opening degree of the variable orifice made up of the control boat Ila decreases depending on the amount of movement of the spool portion 11b, so when the manual switching valve 11 is switched, the differential pressure before and after the variable orifice changes accordingly. be. Therefore, the branch i on the upstream side of the manually operated switching valve 11
A pilot pressure corresponding to the switching amount is generated in the line 15.

Furthermore, the pilot chamber 12 of the pilot switching valve 12
a and 12b are connected to the shuttle valve 17, and the pilot pressure 'selected by this shuttle valve 17 is guided to one inlet of another shuttle valve 18, and the other inlet of this shuttle valve 18 is connected to a branch. The pressure in the passage 15, that is, the pressure between the fixed throttle 16 and the control port lla is guided.

Therefore, the pilot pressure generated by operating the pilot operation valve 13 and the pilot pressure generated by operating the manual operation switching valve 11, whichever is higher, is
Selected by shuttle valve 18. The pilot pressure selected in this way is guided to the regulator 19, and the discharge amount of the variable displacement pump PI is gradually increased from the minimum discharge amount.

In addition, the reference numeral 20 in the figure is an unload valve, and the spring force of a spring 21 is applied to one end of the valve, and a pilot chamber 20a is provided on the opposite side of the spring 21. The pilot pressure guided by the

Therefore, when both the switching valves 11 and 12 are held at the neutral position shown in the drawing, pilot pressure to be guided to the regulator 19 is not generated, so the discharge amount of the variable displacement pump P1 becomes the minimum, and the minimum discharge amount is Returns to tank T via unload valve 20.

When the manually operated switching valve 11 is switched from the illustrated neutral position to either the left or the right, pilot pressure is generated in the branch passage 15 on the upstream side of the manually operated switching valve 11 depending on the switching amount. The pilot pressure generated in this manner acts on the regulator 19 via the shuttle valve 18, and also acts on the pilot chamber 20a of the unload valve 20.
It also acts to switch the unload valve 20 to the closed position, which is the lower position in the drawing.

The regulator 19 includes the manually operated switching valve 1 as described above.
A pilot pressure corresponding to the switching amount of 1 is applied, and at this time, the variable displacement pump P1 secures a discharge amount corresponding to the pilot pressure.

Furthermore, when the operating lever +3c of the pilot operating valve 13 is operated while the manually operated switching valve 11 is held in the neutral position of the drawing line, the pilot operating switching valve 1
2 is switched, while the pilot pressure is transferred to the shuttle valve 17.
．． It acts on the regulator 18 and also acts on the pilot chamber 20a of the unload valve 20 over the course of one day, and functions in the same way as when the manual operation switching valve 11 is switched.

Furthermore, while switching the manual operation switching valve 11, the pilot operation valve 13 is operated to switch the pilot operation switching valve 12.
When these are switched simultaneously, the higher pilot pressure between the pilot pressure generated on the branch passage 15 side and the pilot pressure generated on the shuttle valve 17 side is selected by the shuttle valve 18, and the selected pilot pressure is applied to the regulator. 19
and acts on the pilot chamber 20a of the unload valve 20.

In the above embodiment, the control boat 11a is a variable orifice, but in this way, the manually operated switching valve I
Instead of directly providing a variable orifice in the t, for example, as shown in FIG. It may be provided.

Further, in the above embodiment, the unload valve 20 is provided, but if the switching valves 11 and 12 are of the center bypass type or if the discharge amount of the variable displacement pump P1 can be controlled to zero, the unload valve 20 can be becomes unnecessary.

(Effects of the Present Invention) The present invention can eliminate the need for a conventional cam mechanism or pressure reducing valve by providing a variable orifice in the manual switching valve. Since a cam mechanism and a pressure reducing valve are not required, the circuit is simplified and costs are reduced.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a symbolic diagram of a manual switching valve showing another embodiment, and FIG. 3 is a conventional circuit diagram. Pl...variable displacement pump, P2...pyro/)
Pump, 11...Manual operation switching valve, 12...Pilot operation switching valve, 13...Pilot operation-valve, 18
···regulator. Representative Patent Attorney Nobuyuki Shima 1. Large 2. Figure 11 m-------------.

Claims (1)

[Claims] A manually operated switching valve and a pilot operated switching valve are connected to the variable displacement pump, and the pilot chamber of the pilot operated switching valve described in section 2 has a valve that is proportional to the operating amount of the pilot operated valve connected to the pilot pump via a passage. The manually operated switching valve is connected to a branch passage branching off from the passage, and is opened to the maximum when the manual switching valve is in a neutral position;
A variable orifice that reduces the opening degree according to the switching amount is provided, and a fixed throttle is installed in the branch passage upstream of the variable orifice (the pilot pump is communicated with the tank through the fixed throttle and variable orifice). ,
The higher of either the pilot pressure acting on the pilot operation switching valve or the pilot pressure generated by switching the manual operation switching valve and narrowing the variable orifice is configured to act on the regulator of the variable displacement pump. Control circuit for variable displacement pump.