JPH0643522Y2 - Variable pump flow controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a device in which a throttle is provided in a neutral flow passage, and the flow rate of a variable discharge pump is controlled by the pressure on the upstream side of the throttle.

(Prior Art) As a device of this type, a conventionally known device is of a type in which only one throttle is provided in the neutral channel.

(Problems to be solved by the present invention) If there is only one throttle as described above, there is a problem that the pressure difference before and after that is too large, which causes cavitation and noise.

This invention aims to prevent the occurrence of cavitation and reduce noise.

(Means for Solving Problems) This invention connects a plurality of neutral passages of switching valves in series,
A variable pump is connected to the most upstream switching valve, while a throttle is interposed in the neutral channel and tank channel of the most downstream switching valve, and the upstream pressure of the throttle is used as pilot pressure to control the variable pump. It is assumed that the flow rate control device for the variable pump controls the discharge amount of the variable pump.

With this device as a premise, the present invention provides a housing in which a port communicating with the neutral channel and a valve chamber having a relief poppet for opening and closing a seat portion formed at one end of the port are formed, A first throttle opening to the port side, a second throttle opening to the tank passage side,
A back pressure chamber that communicates the first throttle and the second throttle is formed, and the flow path system of the first throttle, the back pressure chamber and the second throttle and the relief poppet are connected in parallel. However, it is characterized in that the pressure on the upstream side of the first throttle and the pressure on the downstream side of the second throttle are made to act against each other on the control mechanism via each pilot passage.

(Operation of the present invention) Since the two throttles are provided and the back pressure chamber is formed between the two throttles as described above, the pressure fluid flows from the first throttle to the second throttle through the back pressure chamber. When passing through the throttle, the back pressure due to the second throttle acts on the back pressure chamber. The pressure difference in the back pressure chamber reduces the pressure difference before and after the first throttle.

Also, when the circuit pressure rises abnormally, the relief poppet opens to prevent the pressure rise.

Then, the pressure on the upstream side of the first throttle and the pressure on the downstream side of the second throttle act on the control mechanism to control the flow rate of the variable pump.

(Effects of the present invention) Since the present invention is configured as described above, the first and second
The pressure difference before and after the throttling is not so large, so that the occurrence of cavitation can be prevented and the noise can be suppressed low.

Further, since the relief poppet is provided in the housing and the first diaphragm and the second diaphragm are formed in this housing, they can be compactly assembled.

Furthermore, since the pressure on the upstream side of the first throttle and the pressure on the downstream side of the second throttle are opposed via the control mechanism, the operation of this control mechanism can be stabilized.

(Embodiment of the Invention) In the embodiment shown in FIG. 1, three switching valves 1 to 3 are connected to the downstream side of a variable pump P. These switching valves 1 to 3 are
When it is in the neutral position shown in the figure, it is of a center open type that opens the neutral flow passages 4 to 6, and the neutral flow passages 4 to 6 of the respective switching valves 1 to 3 are connected in series.

The neutral flow path 6 of the most downstream switching valve 3 is connected to the tank T via the pilot pressure generating mechanism a. The structure of the pilot pressure generating mechanism a is as follows.

That is, a port 8 is formed in the housing h, and the port 8 and the neutral flow path 6 are connected via the passage 9.

One end of the first throttle 10 is opened to the port 8, but the other end of the first throttle 10 is communicated with the back pressure chamber 11, and the back pressure chamber 11 is connected to the second throttle. It communicates with the tank T through 12.

In addition, the valve chamber 7 of the housing h has both squeezers 10, 12
It is equipped with a relief poppet 13 that is parallel to. The relief poppet 13 is normally pressed against the seat portion 15 formed at one opening end of the port 8 by the action of the spring force of the spring 14 to close the seat portion 15.

When the pressure on the port 8 side exceeds the set pressure, the relief poppet 13 moves against the spring 14 and opens the seat portion 15. When the seat portion 15 is opened, the hydraulic oil in the port 8 is released into the valve chamber 7
It is returned to the tank T via the drain port 16 and the relay chamber 17 formed in 1.

Further, one of the control mechanisms C for controlling the discharge amount of the variable pump P is connected to the upstream side of the first throttle 10 via the pilot passage 18, and the other is connected to the second side via the pilot passage 19.
Is connected to the downstream side of the diaphragm 12.

Next, the operation of this embodiment will be described.

Now, when each of the switching valves 1 to 3 is held at the neutral position in the figure, the hydraulic oil from the pump P is supplied to each of the neutral flow passages 4 to 6 → the passage 9 → the port 8 → the first throttle 10 → the spine. Pressure chamber 11 → second throttle 12
To the tank T via.

When the hydraulic oil flows through both throttles 10 and 12 in this manner, a pressure difference occurs between the upstream side of the first throttle and the downstream side of the second throttle. The pressure on the upstream side of the first throttle 10 acts on one side of the control mechanism C via the pilot passage 18, and on the other side, the second pressure via the pilot passage 19 is applied. The pressure on the downstream side of the throttle 12 acts.

Therefore, a pressure difference equal to the pressure difference before and after the two throttles is generated on both sides of the control mechanism C, and the tilt angle of the pump P is controlled by the action of this pressure difference to reduce the discharge amount. .

When at least one switching valve is switched from the above-mentioned state to the left or right position from the neutral position shown in the figure, the neutral passage of the switched switching valve is closed, so that the working oil does not flow into the passage 9. Therefore, the pressure difference between the front and rear of the two throttles disappears, and the pressures on both sides of the control mechanism C become equal. When the pressures on both sides of the control mechanism C become equal, the control mechanism C operates to increase the discharge amount of the variable pump P.

In this embodiment as described above, the first diaphragm 10 and the second diaphragm 10
Since the diaphragm 12 and the diaphragm 12 are arranged in series and the back pressure chamber 11 is formed between these diaphragms, a back pressure is generated in this back pressure chamber. If pressure is applied to the back pressure chamber 11 in this way,
Since the pressure difference around 10 and 12 is small, cavitation is less likely to occur, and noise can be suppressed low.

Further, a relief poppet 13 is provided in the housing h, and the first throttle 10 and the second throttle 12 are formed in this housing, and further, the first throttle, the back pressure chamber and the second throttle are formed. Since the flow path system and the relief poppet are arranged in parallel, they can be compactly assembled.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, in which only a pilot pressure generating mechanism is shown in a concrete cross section. 1 to 3 ... switching valve, 4 to 6 ... neutral flow passage, 10 ... first throttle, 11 ... back pressure chamber, 12 second throttle, C ... control mechanism.

Claims (1)

[Scope of utility model registration request] 1. A neutral flow path of a plurality of switching valves is connected in series,
A variable pump is connected to the most upstream switching valve, while a throttle is interposed in the neutral channel and tank channel of the most downstream switching valve, and the variable discharge pump is controlled by using the upstream pressure of the throttle as a pilot pressure. In a flow control device for a variable discharge pump that controls a discharge amount of the variable discharge pump by acting on a mechanism, a port communicating with the neutral flow path and a relief poppet for opening and closing a seat portion formed at one end of the port A valve chamber in which the inside of the valve chamber is formed, and a first throttle opening to the port side, a second throttle opening to the tank passage side, and the first throttle and the second throttle are communicated with each other. And a back pressure chamber for allowing the first throttle to be formed,
The back pressure chamber and the flow path system of the second throttle and the relief poppet are connected in parallel, and the pressure on the upstream side of the first throttle,
A flow rate control device for a variable pump, characterized in that the pressure on the downstream side of the second throttle is made to act against each other on the control mechanism via each pilot passage.