JPH0633772B2 - Variable displacement pump controller - Google Patents

Description

The present invention relates to a variable displacement pump for constant horsepower control, which has a cutoff function (an energy saving function that reduces the discharge amount of the pump to near zero when the operating pressure exceeds a predetermined value). Regarding the control device.

(Conventional Hydraulic Circuit) FIG. 1 shows a controller for a variable displacement pump for constant horsepower control having a cutoff function which has been widely and conventionally used. The variable displacement pump 1 will be described later. Control cylinder 2 that constitutes a control device together with regulator 5
The discharge amount is controlled according to the moving amount of the piston.

The variable displacement pump 1 is connected to the main passage 3, and a branch passage 4 branches off from the main passage 3, and the rod side chamber 2a of the control cylinder 2 is connected to the main passage 3 (the branch passage 4 May be present).

In the case of the present embodiment, the regulator 5 that constitutes the control device together with the control cylinder 2 is configured as a servo valve because the position feedback system is taken as an example. The first port 5a of the regulator 5 communicates with the branch passage 4 and the second port 5b directly communicates with the bottom side chamber 2b of the control cylinder 2.

The pilot chamber 5e of the spool portion 5d of the regulator 5 communicates with the branch passage 4 and is provided with a spring 6 on the side opposite to the pilot chamber 5e. Also, the sleeve portion 5f of the regulator 5
Are mechanically connected to the piston rod 2c of the control cylinder 2 via an interlocking mechanism 12.

A cutoff valve 7 is connected in tandem on the upstream side of the regulator 5. The cut-off valve 7 has its first port 7a connected to the branch passage 4 and its second port 7b connected to the third port 5c of the regulator 5, while the other third port 7c is connected to the tank 8. is doing.

Further, the pilot chamber 7d of the cutoff valve 7 is directly connected to the branch passage 4, and the spring 9 acts on the side opposite to the pilot chamber 7d. Therefore, when the discharge pressure of the variable displacement pump 1 is equal to or lower than the set pressure determined by the spring 9, the cutoff valve 7 holds the left position shown in the drawing, and in this state, the cutoff valve 7 operates as a regulator. 3rd port 5c of 5
Is communicated with the tank 8 via the second port 7b and the third port 7c, and when the discharge pressure of the variable displacement pump 1 exceeds the set pressure determined by the spring 9, this time it is switched to the right position in the drawing. The branch passage 4 to the first port 7a of the cutoff valve 7 and the second port 7b.
Through the third port 5c of the regulator 5.

Therefore, when the variable displacement pump 1 is driven, its discharge pressure acts on the rod side chamber 2a of the control cylinder 2 from the main passage 3, and the regulator 5 and the pilot chamber 5e of the cutoff valve 7 via the branch passage 4, Also works for 7d.

Then, first, the piston rod 2c of the control cylinder 2 tries to move to the right in the drawing by the pressure acting on the rod side chamber 2a of the control cylinder 2, but at the same time, the regulator 5 causes the spring by the pressure acting on the pilot chamber 5e. While pressing 6 it moves to the left and switches to the right position in the drawing. As a result, the discharge pressure of the variable displacement pump 1 changes from the branch passage 4 to the first port 5a and the second port 5b.
Will also act on the bottom side chamber 2b of the control cylinder 2 via the piston rod 2c of the control cylinder 2.
Starts to move to the left in the drawing under the pressure acting on the rod side chamber 2a and the bottom side chamber 2b due to the difference in pressure receiving area between the two.

On the other hand, the piston rod 2c in this control cylinder 2
The discharge amount of the variable displacement pump 1 decreases as the valve moves to the left, and the sleeve portion 5f of the regulator 5 decreases.
However, while moving a little behind the spool portion 5d through the interlocking mechanism 12, that is, while keeping the regulator 5 at the switching position to the right side position in the drawing, the regulator 5 follows it and moves in the same direction.

Then, when the leftward force due to the pressure in the pilot chamber 5e (the discharge pressure of the variable displacement pump 1) and the rightward force due to the spring 6 are balanced, the spool portion 5d of the regulator 5
Is stopped and the sleeve part 5 is slightly delayed.
f catches up, and the regulator 5 becomes in a state in which the illustrated neutral position, that is, the second port 5b does not communicate with the first port 5a or the third port 5c, whereby the bottom side chamber 2b of the control cylinder 2 is blocked. The piston rod 2c also stops, thus controlling the discharge amount of the variable displacement pump 1 according to the discharge pressure at that time.

Further, when the discharge pressure of the variable displacement pump 1 further increases from the above state, the spool portion 5d of the regulator 5 is again provided.
Moves to the left to a position where the force acting on the pilot chamber 5e and the force of the spring 6 are unbalanced and the forces of these two are balanced, and accordingly the regulator 5 switches to the right position in the drawing and the control cylinder 2 The piston rod 2c moves to the left to decrease the discharge amount of the variable displacement pump 1 in the same manner as described above, and when the sleeve portion 5f of the regulator 5 catches up with the spool portion 5d, the regulator 5 is returned to the neutral position. Go back and stop.

On the other hand, when the discharge pressure of the variable displacement pump 1 is reduced, the force acting on the pilot chamber 5e of the regulator 5 is reduced, so that the spool portion 5d of the regulator 5 is affected by the force of the spring 6. The spring force is pushed rightward to a position where it balances the force acting on the pilot chamber 5e, and the regulator 5 is switched to the left position in the drawing. Thereby, the bottom side chamber 2b of the control cylinder 2
Is communicated with the tank 8 from the second and third ports 5b and 5c of the regulator 5 via the second and third ports 7b and 7c of the cutoff valve 7, so that the piston rod 2c
Moves in the right direction in the drawing together with the sleeve portion 5f of the regulator 5 to increase the discharge amount of the variable displacement pump 1, and the sleeve portion 5f of the regulator 5 catches up with the spool portion 5d to be in the neutral position shown. Stop when you return.

Further, assuming that the discharge pressure of the variable displacement pump 1 rises from these states and exceeds the set pressure determined by the spring 9 of the cutoff valve 7, the regulator 5 is switched to the right position in the drawing in the same manner as described above. , Control cylinder 2
The piston rod 2c of is controlled to move to the left to decrease the discharge amount of the variable displacement pump 1, and at the same time, the pressure acting on the pilot chamber 7d of the cut-off valve 7 resists the spring 9 from the left position shown in the figure. Switch to the right position.

As a result, the third port 5c of the regulator 5, which has been connected to the tank 8 via the second and third ports 7b and 7c of the cutoff valve 7 until now, is the second and first ports of the cutoff valve 7. To the branch passage 4 via the ports 7b and 7a. Therefore, in this case, the regulator due to the fluctuation of the discharge pressure of the variable displacement pump 1 (generally, the discharge pressure of the variable displacement pump 1 constantly fluctuates with a certain width during the operation of the circuit). 5 is switched to either the right side or the left side of the drawing, the fluid discharged from the variable displacement pump 1 is irrespective of them, through the first and second ports 5a and 5b of the regulator 5, or The first and second ports 7a and 7b of the cutoff valve 7 flow into the bottom side chamber 2b of the control cylinder 2 through the third and second ports 5c and 5b of the regulator 5. Therefore, in any case, the piston rod 2c of the control cylinder 2 moves toward the left end of the drawing to the end thereof, thereby maintaining the discharge amount of the variable displacement pump 1 to a minimum.

From the above, the characteristic of the spring 6 in the control mechanism including the control cylinder 2 and the regulator 5 is set so that the product of the discharge amount Q and the discharge pressure P of the variable displacement pump 1 is always constant, that is, "P".・ If set to approximate a constant horsepower curve of “Q = constant”, the discharge amount automatically changes along the constant horsepower curve in response to the change in the discharge pressure of the variable displacement pump 1, and When the discharge pressure of the variable displacement pump 1 rises above the set pressure of the cutoff valve 7, this time the discharge amount is reduced to almost zero, and wasteful energy loss is prevented. The above-mentioned control characteristics are shown in the characteristic diagrams of a, b, c, d and e in FIG.

Thus, the control device for the variable displacement pump described above,
It can be said that the circuit is highly efficient and excellent in energy saving, but when such a variable displacement pump control device is used in, for example, a construction vehicle, the following problems occur. In other words, when there is an obstacle that must be overcome while traveling on a rough road, the discharge pressure of the variable displacement pump exceeds the set pressure and the cutoff valve operates, and the discharge amount drops to near zero and cuts. In order to enter the off control, the power is inevitably inevitable and it is impossible to get over such an obstacle.

(Object of the Invention) Accordingly, an object of the present invention is to provide a control device for a variable displacement pump for constant horsepower control having a cut-off function, while making the most of the characteristics of the device, and further enabling the device to perform cut-off control. If special power conditions are required to enter and sufficient power is required, for example, if you want to get over an obstacle, you can arbitrarily increase the cutoff control set pressure, that is, set the circuit pressure to enter cutoff control. Raise it
It is an object of the present invention to provide an improved controller for a variable displacement pump of this type, which can take out sufficient power.

(Embodiment of the present invention) Hereinafter, the present invention will be described based on embodiments shown in FIG.

The embodiment of the present invention shown in FIG. 3 has a variable displacement pump 1, a control cylinder 2, a regulator 5 and a cutoff valve 7, which is exactly the same as the conventional one, and
Their configuration is also similar to the conventional one. Therefore, regarding the same constituent elements as those in the conventional art, the first constituent element in FIG.
Description will be given by attaching the same reference numerals to the drawings.

Therefore, in this embodiment, the cutoff valve 7 is
The cylinder 10 is provided so as to face the spring 9 of the cylinder 10, the piston rod 10a of the cylinder 10 is brought into contact with the spring 9 of the cutoff valve 7, and the branch passage 4 is manually switched together with the regulator 5 and the cutoff valve 7. Valve 11 is connected in parallel.

When the manual switching valve 11 is in the left position shown in the drawing, the bottom side chamber 10b of the cylinder 10 is connected to the tank 8 via the second and third ports 11b and 11c. Therefore, in this case, the set pressure of the cutoff valve 7 is determined only by the set force of the spring 9, and the cutoff valve 7 is set so that the discharge pressure of the variable displacement pump 1 is determined by the spring 9. When the pressure is exceeded, it switches to the right position in the drawing, which is no different from the conventional case described above.

However, when the manual switching valve 11 is switched to the right position in the drawing, the bottom side chamber 10b of the cylinder 10 now communicates with the branch passage 4 via the second and first ports 11b and 11a of the manual switching valve 11. To do. As a result, a part of the fluid discharged from the variable displacement pump 1 is guided to the bottom side chamber 10b of the cylinder 10 through the manual switching valve 11 and the piston rod
The spring 9 of the cutoff valve 7 is compressed by 10a.
Therefore, the spring 9 has a stronger force as much as it is compressed, and the set pressure of the cutoff valve 7 is increased.

From this, in the state where the manual switching valve 11 is switched to the right position as described above, even if the discharge pressure of the variable displacement pump 16 becomes the set pressure of the cutoff valve 7 only by the conventional spring 9, The cut-off valve 7 does not switch, but only when the set pressure of the spring 9 increased by the operation of the cylinder 10 is exceeded, the cut-off valve 7 switches. Therefore, if the set pressure of the cut-off valve 7 at this time is f, the circuit pressure at that time can be used up to point f, as can be seen from FIG. 2, and the power of the variable displacement pump 1 can be made full. It can also be utilized.

Although the cylinder 10 is arranged in series with the spring 9 of the cutoff valve 7 in the embodiment of FIG. 3, the cylinder 10A is arranged as the spring 9 of the cutoff valve 7 as shown in the embodiment of FIG. They may be arranged in parallel, or, instead of this, as shown in FIGS. 5, 6, and 7, for example, as the pilot chamber 7a of the cut-off valve 7, a two-stage cylinder 10B or a parallel cylinder 10C or By using the differential cylinder 10D and switching the pressure receiving areas of these cylinders 10B, 10C, and 10D with the manual switching valve 11, the force on the pilot chamber 7d side that opposes the spring 9 is controlled, and the apparent appearance of the cutoff valve 7 is controlled. The set pressure may be adjusted.

On the other hand, although each of the embodiments shown in FIGS. 3 to 7 shows the case of the self-pressure control, an auxiliary pump may be used instead of the control, and the set pressure of the cut-off valve 7 may be controlled. Although the manual switching valve 11 was used for switching,
It is also possible to allow the operator to freely operate the remote controller 11 in the operator room by switching this with a hydraulic pilot or a solenoid.

Further, in each of the above-described embodiments, the cutoff valve 7 is connected to the control cylinder 2 as in FIG. 6, for example.
And the regulator 5 may be arranged between them and the regulator 5 may be a force feedback system shown in FIG. 7 instead of the position feedback system. Further, it goes without saying that each of these embodiments can be used not only in the case of composite control using a plurality of pumps, but also in combination with another control method such as positive control, negative control, or load sensing.

(Structure of the present invention) The present invention relates to a variable displacement pump, a control mechanism that detects the discharge pressure of the variable displacement pump and adjusts the discharge amount thereof, and the discharge pressure of the variable displacement pump reaches a set pressure In addition, the present invention is premised on a control device for a variable displacement pump that includes a cutoff valve that operates a control mechanism so as to reduce the discharge amount of the variable displacement pump.

Then, the first and second inventions are provided with a control means for increasing the set pressure of the cutoff valve while applying the discharge pressure of the variable displacement pump to the pilot chamber of the cutoff valve. It is the main element.

In both inventions, the main invention is made common, while the first invention is such that a control means is provided on the side facing the pilot chamber and controls the set pressure of the cart-off valve, and one of the cylinders. It is composed of a switching valve that connects the chamber to the tank or to the pressure source.When the pressure of the pressure source is applied to the chamber of the cylinder by switching this switching valve, the set pressure of the cutoff valve rises. It is characterized in that it is configured to.

In addition, a second aspect of the present invention includes a control unit that sets the pressure receiving surface of the pilot chamber in two stages and increases the apparent set pressure of the cutoff valve as necessary.
It consists of a switching valve that selects the pressure receiving surface of the stage, and by switching this switching valve, the pressure of the pressure source is applied to both pressure receiving surfaces or one of the pressure receiving surfaces, and the operating force of the pilot chamber is controlled. It is characterized by

(Effects of the Invention) In any of the first and second inventions, the operator can operate the switching valve to raise the set pressure of the cutoff valve when needed, so that, for example, a construction vehicle It is possible to exert sufficient power when overcoming obstacles, and it will not hinder driving on rough roads.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a conventional controller for a variable displacement pump, FIG. 2 is a control characteristic diagram, and FIG. 3 is a circuit diagram showing an embodiment of the present invention, FIGS. , Figures 6 and 7
Each of the drawings is a circuit diagram showing another embodiment of the present invention. 1 ... Variable displacement pump, 2 ... Control cylinder, 5 ... Regulator that cooperates with the control cylinder to form a control mechanism, 7 ... Cutoff valve, 9 ... Spring, 10, 10
A, 10B, 10C, 10D ... Cylinder, 11 ... A manual switching valve that forms control means in cooperation with the cylinder.

Continuation of the front page (56) References JP-A-58-222991 (JP, A) JP-A-58-210388 (JP, A) JP-A-56-54982 (JP, A) Actual development 55-4362 (JP , U) Japanese Patent Publication Sho 55-47641 (JP, B1)

Claims (2)

[Claims] 1. A variable capacity pump, a control mechanism for detecting the discharge pressure of the variable capacity pump and adjusting the discharge pressure, and a variable capacity pump when the discharge pressure of the variable capacity pump reaches a set pressure. In a control device for a variable displacement pump equipped with a cutoff valve that operates a control mechanism to reduce the discharge amount of the variable displacement pump, the discharge pressure of the variable displacement pump is applied to the pilot chamber of the cutoff valve while Control means for increasing the set pressure of the cutoff valve,
This control means is composed of a cylinder provided on the side facing the pilot chamber and for controlling the set pressure of the cutoff valve, and a switching valve for communicating this cylinder chamber with a tank or with a pressure source. A control device for a variable displacement pump configured to raise a set pressure of a cutoff valve when the pressure of a pressure source is applied to one chamber of a cylinder by switching the switching valve. 2. A variable displacement pump, a control mechanism for detecting the discharge pressure of the variable displacement pump and adjusting the discharge pressure, and a variable displacement pump when the discharge pressure of the variable displacement pump reaches a set pressure. In a control device for a variable displacement pump equipped with a cut-off valve for operating a control mechanism so as to reduce the discharge amount of the variable displacement pump, the discharge pressure of the variable displacement pump is applied to the pilot chamber of the cut-off valve. Is provided with a control means for setting the pressure receiving surface in two stages and increasing the apparent set pressure of the cut-off valve if necessary, and the control means comprises a switching valve for selecting the pressure receiving surface in two stages. A variable displacement pump characterized in that the switching valve is switched so that the pressure of the pressure source acts on both pressure receiving surfaces or on one of the pressure receiving surfaces to control the operating force of the pilot chamber. The control device.