JPS626306Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a capacity control device for a variable displacement vane pump.

In general, this type of displacement control device has a cam ring with a large diameter piston and a small diameter piston that opposes the cam ring, on which a vane rotates in sliding contact with each other. However, in this type of pump, when the pump capacity is controlled from the maximum to the minimum, the cam ring tends to move excessively, and for example, as shown in the first diagram, the discharge pressure curve A
has the drawback that the pressure fluctuates rapidly with a large overshoot state B and subsequent pressure drop C when the pump capacity changes, and furthermore, when switching between the minimum flow discharge state and the maximum flow discharge state D. There were other inconveniences such as a shock occurring and difficulty in adjusting the pressure response time.

The purpose of the present invention is to eliminate these drawbacks and inconveniences, and the capacity of the variable displacement vane pump 1 is reduced by a cam ring that is moved by being pushed by a large diameter piston 2 and a small diameter piston 3 opposing it. 4, the pump discharge pressure is applied to the small diameter piston 3 to actuate the cam ring 4 on the side where the pump capacity decreases, and the cam ring 4 is applied to the large diameter piston 2 on the side where the pump capacity increases. Pump discharge pressure is applied via a sequence valve 5 to operate the pump, and when the sequence valve 5 is operated by the pump discharge pressure, tank pressure acts on the large diameter piston 2. A first throttle 7 and a check valve 8 for blocking fluid flow from the piston 2 to the sequence valve 5 are sequentially provided in a circuit 6 leading from the sequence valve 5 to the large-diameter piston 2. A second diaphragm 9 having a smaller opening area than the first diaphragm 7 is provided in parallel with the first diaphragm 7.

FIG. 2 shows one example, in which a rotor 11 having radial vanes 10 on the outer periphery is rotatably provided inside the cam ring 4, and when the rotor 11 is rotated by a prime mover 12, the cam ring 4 The vane 10 slides and rotates on the inner surface of the pump to discharge pressure fluid to the discharge circuit 13. Further, the cam ring 4 is operated to increase the pump capacity by the pump discharge pressure of the discharge circuit 13 that acts on the large diameter piston 2 via the circuit 6 and the circuit 14, and
The pump discharge pressure of the discharge circuit 13 acting through the circuit 15 operates to reduce the pump capacity. When the pump discharge pressure of the discharge circuit 13 reaches the set pressure, the sequence valve 5 switches and the pressure acting on the large diameter piston 2 becomes the tank pressure, so the cam ring 4 is pushed by the small diameter piston 3 and decreases as described above. Move to the side. In addition, the first and second apertures 7,
9 is preferably configured as a variable aperture, and the first
It is assumed that the aperture area of the diaphragm 7 is not reduced to less than the aperture area of the second diaphragm 9.

Reference numeral 16 denotes a spring that presses the large diameter piston 2 toward the cam ring 4.

The second throttle 9 is adjusted to have an appropriate opening area so as to suppress the speed of the cam ring 4 when it moves in the direction of decreasing the pump capacity, and to prevent pressure overshoot, pressure drop, or shock. The first throttle 7 and the check valve 8, together with the second throttle 9, introduce the pump discharge pressure that acts on the large diameter piston 2 when the cam ring 4 moves in the direction of increasing the pump capacity. If the first throttle 7 and check valve 8 were not present, the pump discharge pressure would be introduced into the piston 2 only through the second throttle 9 again. Therefore, normally, the opening area suitable for controlling the speed at which the cam ring 4 moves to the side where the pump capacity decreases is quite small, and in that area, the speed at which the cam ring 4 moves to the side where the pump capacity increases decreases, and the response time decreases. The first throttle 7 and the check valve 8 are provided to prevent such a delay in response, which is undesirable.

In the test, the aperture area of the first diaphragm 7 was
If it is smaller than the orifice 9, the movement speed of the cam ring 4, both to the side of increasing the pump capacity and to the side of decreasing the pump capacity, depends mostly on the second aperture 9, and
The effect of the throttle 7 will not be achieved, and the first throttle 7 will not be able to control the speed of movement of the cam ring 4 toward the pump capacity increase side smoothly unless the opening area of the first throttle 7 reaches a level equal to or higher than the second throttle 9. I couldn't do it.

To explain its operation, when the pressure in the discharge circuit 13 does not reach the set pressure for switching the sequence valve 5, the pressure is
Acting on the large diameter piston 2 via the throttle 7, the check valve 8 and the second throttle 9, the cam ring 4 is in the position shown to maximize the pump capacity. When the pressure in the discharge circuit 13 exceeds the set pressure for switching the sequence valve 5, the circuit 6 is connected to the tank,
Since tank pressure acts on the large diameter piston 2, the cam ring 4 is pushed by the small diameter piston 3 and moves to minimize the pump capacity. In this case, the fluid behind the large-diameter piston 2 is discharged to the tank via the second throttle 9, which prevents shock caused by switching of the discharge state and also prevents the cam ring 4 from moving excessively. As a result, a curve E without a pressure overshoot and a pressure drop immediately after it as shown in FIG. 3 is obtained. Also, the second
By adjusting the aperture area of the diaphragm 9, the response time _T1 can be controlled. Further, when the pressure in the discharge circuit 13 falls from above the set pressure to below the set pressure, the sequence valve 5 switches to apply this pressure to the large diameter piston 2, and the fluid pressure in the circuit 6 is reduced to the first throttle 7.
This acts on the piston 2 through the check valve 8 and the second throttle 9. However, by setting the first throttle 7 to a larger opening area level than the second throttle 9 as described above, the first throttle 7 acts on the piston 2. 2 to prevent shock when the pump capacity goes from minimum to maximum. Incidentally, by changing the area of the first diaphragm 7, the response time _T2 shown in the third figure can be controlled.

In this way, according to the present invention, the first throttle 7 and the check valve 8 are sequentially provided in the circuit 6, and the second throttle 9 is provided in parallel with these, so that the maximum flow rate discharge state and the minimum flow rate discharge state can be changed. It is possible to prevent shock at the time of switching, to prevent pressure overshoot and pressure drop, and to easily adjust the response time.

[Brief explanation of the drawing]

Fig. 1 is a curve diagram of pump discharge pressure by a conventional variable displacement hydraulic pump displacement control device, Fig. 2 is a diagram of an example of the device of the present invention, and Fig. 3 is a curve diagram of pump discharge pressure by the device of the present invention. It is a diagram. 1... Variable displacement vane pump, 2... Large diameter piston, 3... Small diameter piston, 4... Cam ring, 5... Sequence valve, 6... Circuit, 7...
1st throttle, 8...check valve, 9...2nd throttle.

Claims (1)

[Scope of utility model registration request] The capacity of the variable displacement vane pump 1 is configured to be freely controllable by a cam ring 4 that is moved by being pushed by a large diameter piston 2 and a small diameter piston 3 opposing the cam ring 4, and the small diameter piston 3 is configured to have a pump capacity decreasing side. Pump discharge pressure is applied to the large diameter piston 2 to operate the cam ring 4 to increase the pump capacity, and pump discharge pressure is applied to the large diameter piston 2 via the sequence valve 5 to operate the cam ring 4 to increase the pump capacity. When the valve 5 is actuated by the pump discharge pressure, tank pressure acts on the large diameter piston 2, and a circuit 6 connected from the sequence valve 5 to the large diameter piston 2 has a first A variable valve is constructed by sequentially providing a throttle 7 and a check valve 8 for blocking fluid flow from the piston 2 to the sequence valve 5, and in parallel with these, a second throttle 9 having a smaller opening area than the first throttle 7. Capacity control device for positive displacement vane pump.