JPH022949Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Field of Application) The present invention relates to improvements in variable displacement piston pumps or variable displacement vane pumps used in hydraulic equipment and the like.

(Prior Art) Conventional variable discharge pumps, whether piston pumps or vane pumps, have an adjustment mechanism that varies the discharge amount between the low pressure maximum discharge amount and the dead head pressure flow rate. The displacement amount of the displacement part is varied between the maximum displacement amount (low pressure maximum discharge amount) and the dead head displacement amount (dead head pressure flow rate) to make the discharge amount variable.

In such conventional variable discharge amount pumps, the displacement part is, for example, a ring in a variable discharge amount vane pump, and the maximum displacement amount for the low pressure maximum discharge amount is determined by the maximum displacement (eccentricity) eMAX of the ring center with respect to the rotor center. stipulated. This maximum displacement is generally achieved by a spring and/or a hydraulic piston pushing the ring. Similarly, the movement of the ring to the deadhead displacement amount that results in the deadhead pressure flow rate is caused by the force of the second hydraulic piston resisting the spring/hydraulic piston or by the hydraulic pressure caused by tilting the discharge port position in the direction of rotation. This is done by pushing the ring in the opposite direction. A stopper for setting the dead head position from the outside is not provided, and a pressure adjusting member 26 and a pressure adjusting cylinder 20, which can be adjusted from the outside, are usually used to adjust the pressure by using a pressure adjusting member 26 and a pressure adjusting cylinder 20, as shown in, for example, Japanese Patent Laid-Open No. 53-139208. The elastic force of 16 can be adjusted in two steps. Therefore, in this case, the ring was made to be able to instantaneously move to the left of the position where the displacement amount is 0, as seen in FIG. 4B, to the position where the discharge amount is negative. Also, the 1970s
Even when a stopper that can be adjusted from the inside, such as the adjustable minimum discharge amount stopper 108 of Publication No. 16901, is provided, it should be set as close as possible to the position of zero displacement as seen in Figure 4B in order to obtain the discharge pressure. This left a considerable gap between the head displacement amount and the eDH position. Generally speaking, when the pressure suddenly increases to bring the ring into a deadhead state, the ring moves at high speed due to the force of the second hydraulic piston or the hydraulic pressure plus the inertia of the ring. It moves to a position where the discharge amount exceeds the amount eDH and becomes negative, or to a smaller displacement (eccentricity) amount eD2 that approaches the displacement amount O.
Next, it is pushed back by the spring/hydraulic piston to become a displacement eD3 that is larger than the dead head displacement (eccentricity) eDH, and as this is repeated, it stabilizes at the dead head displacement eDH.

As a result, the pump pressure near the deadhead repeatedly rises and falls in an unstable manner until it stabilizes at the deadhead pressure PDH as shown in Figure 1, which not only makes the pump pressure unstable but also causes noise and vibration. Summer.

(Problem to be solved by the invention) In other words, generally when the pump is operated at the deadhead pressure PDH to compensate for leakage from the pump high pressure chamber to the pump low pressure chamber and leakage in the control system beyond the pump, the pump is operated at the deadhead pressure PDH. The discharge amount is automatically set to be enough to replenish these leaks, and the displacement (eccentricity) amount of the displacement portion at that time, that is, the dead head displacement amount eDH, is thus automatically positioned by the variable discharge amount pump itself. However, as mentioned above, in the conventional product, until the pump stabilized at the dead head pressure, the pump would overshoot and swing back to a displacement smaller than the dead head displacement amount eDH, resulting in unstable pressure, noise, and vibration.

The present invention eliminates the drawbacks of the conventional products and prevents excessive movement of the displacement part of the variable displacement pump adjustment mechanism even when the pressure suddenly increases to the deadhead output, thereby stabilizing the pressure and eliminating noise and vibration. The purpose of this invention is to provide a variable discharge amount pump used in hydraulic equipment, etc.

(Means for Solving the Problems) The problems of the present invention described above have been solved by providing a variable discharge amount pump as described in the claims of the utility model registration.

(Function) When the variable discharge amount pump configured as described above is operated, the stopper will not operate if the circuit pressure, that is, the pump pressure, increases slowly, but if the circuit pressure increases rapidly, e.g. When a cylinder moving at high speed is suddenly stopped, in conventional products, the displacement part stop position is near the position of 0 displacement as shown in Figure 4 (b), so the displacement part is moved from the displacement (eccentric) position. Deadhead displacement (eccentricity) amount
In order to move at high speed to the eDH position, due to its inertia, it attempts to move to a displacement (eccentricity) amount eD2 smaller than the dead head displacement amount eDH. However, in this invention, the stopper is adjustable from the outside.
When the movement of the displacement part is stopped at a displacement eD0 position which is extremely slightly smaller than the dead head displacement eDH position, and when the end surface having the sub-piston closing device abuts against the flat surface of the stopper, and the abutment occurs. The oil chamber of the sub-piston is closed off between the stopper flat surface by the sub-piston closing device, and the pressure oil in the sub-piston is squeezed through the gap between the stopper flat surface and the sub-piston end surface. Since the cylinder is discharged by the cushioning action, the shock at the time of collision between the secondary piston and the stopper is prevented, and the displacement part is accurately adjusted by the displacement amount of the dead head.
At the position of displacement eD0, which is extremely slightly smaller than eDH,
It stopped while decelerating, and then converged at the position of the dead head displacement eDH. As a result, the range of pressure fluctuations when the pressure rises can be reduced, and the time required for the dead head pressure and flow rate to stabilize is shortened.

Embodiments The invention will now be described in more detail, by way of example, with reference to the accompanying drawings, which show embodiments as variable displacement vane pumps. 3 and 4 show the structure of a variable discharge amount vane pump to which the present invention is applied, and is provided with a stopper 15 and a stopper adjustment screw 16 to prevent excessive movement of the ring 7 of the vane pump without causing an impact. It is characterized by Adjustment screws of this type are adjustable from the outside of the variable displacement vane pump, as will be apparent to those skilled in the art. A ring 7 is held between a sub piston 5 and a main piston 4 within the housing 1. In FIG. 3, the center ₀₁ of the ring 7 is maximally displaced (eccentric) from the center 0 of the rotor 8 in which the vanes 9 are inserted radially, and is at the position of the lowest pressure maximum discharge amount. In the embodiment, the adjustment mechanism that makes the discharge amount variable includes a sub-piston 5 on one side, a spring 10 that urges the sub-piston toward the ring 7 which is a receiving part, and a spring-side oil chamber 22 of the sub-piston 5. The pump discharge pressure constantly guided through the passage 20 urges the ring 7 toward the maximum displacement eMAX, and on the other hand, the passage 21 is connected to the main piston 4 and the oil chamber 23 on the side opposite to the ring of the main piston. , 26, and the pump discharge oil acts through the pressure compensator 3 to bias the ring 7 toward the deadhead displacement amount eDH, that is, the deadhead pressure flow rate of the pump. In the embodiment, the ring 7 is moved in the 0 direction (to the left) at a position where the displacement eD0 is very slightly smaller than the dead head displacement eDH of the ring 7, which is the displacement part of the adjustment mechanism necessary to maintain the dead head pressure flow rate. A stopper 15 is provided behind the sub-piston 5 to stop its movement, and the position of contact between the stopper 15 and the sub-piston 5 can be adjusted from the outside of the pump with a stopper adjustment screw 16. Oil chamber 23 of main piston 4
is in communication with the drain via the throttle 12 and the passage 25, and the force _Fp of the pump pressure oil pushing the pressure receiving surface 61 of the spool 6 is smaller than the force Fs of the spring 11 set with a pressure adjustment screw (not shown ₎ . At some point, the pressure in the oil chamber 23 is 0, and therefore the maximum displacement eMAX set by the ring 7 and the flow rate adjustment screw 13
It is located at the position (Fig. 3). Oil chamber 2 of sub-piston 5
2 has a pressure receiving surface for pump discharge oil on the spring 10 side, and the inner diameter of the oil chamber 22 is connected to the flat end surface 5 of the stopper 15.
3, and when the sub-piston 5 contacts the flat surface 53, that is, when the stopper 15 stops the movement of the ring 7, the inner diameter edge 52 of the sub-piston 5 is The oil chamber 22 is closed off by a shutoff device 52 formed by.

Next, the operation will be explained. When the rotor 8 is rotated in the direction of the arrow, suction is performed at the bottom of the figure and discharge is performed at the top. The discharge pressure P at this time acts on the pressure receiving surface of the sub piston 5, and also acts on the pressure compensator 3.
acts on the pressure receiving surface 61 of the spool 6. As mentioned above, the hydraulic pressure acting on the pressure receiving surface 61 of the spool 6
When Fp is smaller than the force Fs of the spring 11, the state shown in FIG _.
is being pushed to the right by The hydraulic pressure now acting on the pressure receiving surface 61 is the force of the spring 11.
When Fs is overcome, the spool 6 gradually moves to the right, and as shown in FIG.
are in communication via the passage 26, and pressurized oil begins to flow into the oil chamber 23. A part of this inflowing pressure oil flows into the throttle 1
2 and passage 25 to the drain outside the pump, but as the pump discharge pressure P increases, the amount of movement of the spool 6 increases and the inflow pressure oil increases, so the pressure in the oil chamber 23 gradually increases. Therefore, the hydraulic pressure F _B acting on the main piston 4 increases, and the resultant force of the hydraulic pressure acting on the sub piston 5 and the spool force
When the pump becomes larger than F _A , the ring 7 is moved to the left, the pump discharge amount is reduced, and a deadhead state is established. As the pressure increases gradually, the moving speed of ring 7 becomes slower, and ring 7 reaches its maximum displacement (eccentricity).
From the amount eMAX to the dead head displacement (eccentricity) amount eDH
However, if the pressure suddenly increases (such as when the cylinder connected to the pump strokes out), the ring 7 moves at high speed from the eMAX to the eDH position, and its inertia causes it to move smoothly.
Displacement (eccentricity) smaller than dead head displacement eDH
Try to move up to the amount eD2. But stoppa 1
The end face 51 of the sub-piston 5 hits the ring 7
The displacement amount stops moving in the 0 direction, that is, to the left, at the position eD0, which is extremely slightly smaller than eDH, and then converges to the dead head displacement amount eDH. At this time
eDH≒eD0>eD2. When the end surface 51 of the sub-piston 5 comes into contact with the stopper 15, the oil chamber 22 of the sub-piston 5 is closed to the flat surface of the stopper 15 by the closing device 52 formed by the inner diameter edge of the sub-piston.
3, and the pressure oil in the oil chamber 22 is discharged in the direction of the arrow while being squeezed through the gap δ between the flat surface 53 of the stopper 15 and the end surface 51 of the secondary piston 5. This prevents the shock caused by the impact of the stopper 15. This makes it possible to reduce the range of pressure fluctuations when pressure increases.
In addition, the time required for the dead head pressure and flow rate to stabilize was shortened. FIG. 2 shows a pressure graph near the deadhead pressure according to the present invention, and it can be seen that the pressure has been stabilized compared to FIG. 1. Therefore, it has become a device that eliminates noise and vibration.

The stopper 1 is positioned at a displacement eD0 that is extremely slightly smaller than the dead head displacement eDH.
The method of adjusting the position No. 5 will be explained. The adjustment screw (not shown) of the pressure compensator 3 is used to adjust the pump so that the pump has a desired pressure required for work and a dead head displacement eDH, that is, the ring 7 is adjusted to the left with a displacement of 0 in Figure 4 (b). Suppose that the robot is stopped from moving in that direction and is currently in a dead head state. Therefore, pressure compensator 3
Adjust the adjustment screw (not shown) to set the desired pressure lower than the desired deadhead pressure required for the job, and then adjust the stopper adjustment screw 16 to move the stopper 15 to the right as seen in the figure. The adjustment is completed by fixing the stopper 15 at the position where the pump pressure starts to rise to the desired low pressure set by the pressure compensator 3. The eccentricity of the ring 7 at this time is the displacement eD0
The pressure difference between the dead head pressure necessary for work and the above-mentioned arbitrary pressure is preferably small because it increases stability.

(Effect of the invention) As described above, in the present invention, in a variable discharge amount pump having an adjustment mechanism that makes the discharge amount variable, the amount of deadhead displacement eDH of the displacement part of the adjustment mechanism required to maintain the deadhead pressure flow rate is much lower than that of the deadhead displacement amount eDH. This system is equipped with an externally adjustable stopper and sub-piston that stops the movement of the displacement part in the 0 direction without a shock at the position of a slightly small displacement eD0, and prevents excessive movement of the displacement part when the pump pressure suddenly increases. This reduces pressure fluctuations such as pressure drops caused by pressure rises and pressure rises due to reaction, improving the pressure stability of the pump and eliminating noise and vibration. Although the vane pump has been described, the present invention can also be applied to a variable displacement piston pump, such as a variable displacement piston pump having an adjustment mechanism that is variable by tilting a swash plate.

[Brief explanation of the drawing]

Figure 1 is a graph showing pressure fluctuations of a conventional variable discharge pump near the dead head, Figure 2 is a graph showing pressure fluctuations of a similar variable discharge pump of the present invention, and Figures 3 and 4 are graphs of the present invention. FIG. 4B is a schematic structural diagram of a variable discharge amount vane pump showing an embodiment, and FIG.
Part A of Figure A is shown. 1...Housing, 5...Sub-piston, 7...
Ring (displacement part), 10... Spring, 15...
...Stopper, 16...Stopper adjustment screw, 22...
...oil chamber, 52...closing device, 53...flat surface.

Claims (1)

[Scope of utility model registration request] In a variable discharge pump having an adjustment mechanism that varies the discharge amount between a low pressure maximum discharge amount and a dead head pressure flow rate, the dead head displacement amount eDH of the displacement part of the adjustment mechanism necessary to maintain the dead head pressure flow rate is Extremely small amount of displacement
A stopper that can be adjusted from the outside of the pump is provided in the housing to stop the movement of the displacement part in the O direction at the eDO position while decelerating the movement, and a sub-piston is interposed between the displacement part and the stopper. The sub-piston has one end in contact with the displacement part and is configured to press the displacement part against the housing by a spring, and the other end is connected to an oil chamber having a pressure receiving surface facing the stopper and a flat surface of the stopper. A variable discharge amount pump characterized by comprising a shutoff device having a smaller diameter than the outer diameter of the stopper, which closes off the oil chamber when the displacement portion stops moving in the O direction by coming into contact with the stopper.