JPS6318802Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a hydraulic servo device, and more particularly to a hydraulic servo device that damps sustained vibrations of a main valve and improves stability in a multi-stage control valve.

BACKGROUND ART FIG. 1 shows an example of a conventional hydraulic servo device.
That is, this is a case where a so-called hydraulic position servo system is configured in which the control valve 5 controls the amount of liquid in the liquid chamber 3 of the hydraulic cylinder consisting of the ram 1 and the cylinder casing 2. The input to the control valve 5 is given by calculating and amplifying the difference between the command 8 and the position detector 6 by the control device 7. In this example, the control valve 5 is a so-called two-stage control valve, the pilot valve 13 is a four-way valve type, and the main valve 10 is a three-way valve type. (hydraulic pressure
P _SP ) to main valve drive cylinder 14 (hydraulic pressure
P _C1 ), thereby driving the main valve 10, and the liquid flows from the hydraulic pressure source 9 (hydraulic pressure P _SM ) to the hydraulic cylinder 2 (hydraulic pressure P _C ). In addition, with a negative signal, the liquid flows from the hydraulic pressure source 9 (hydraulic pressure P _SP ) to the main valve drive cylinder 14 (hydraulic pressure P _C2 ), which drives the main valve 10, and the liquid flows from the hydraulic cylinder (hydraulic pressure P _C ) to the tank (hydraulic pressure P _t ).

In such a system, the block diagram is generally shown in FIG. The transfer function G(s) from the command C(s) to the displacement Y(s) of the ram 1 is as follows: G(s) = Y(s)/C(s) = G ₁ (s)・G ₂ (s)・G ₃ (s)・G ₄ (s)・G ₅ (s
)・G ₆ (s)/1+G ₁ (s)・G ₂ (s)・G ₃ (s)・G ₄
(s)・G ₅ (s)・G ₆ (s)・G ₇ (s). Here, each transfer function is as follows.

G ₁ (s): Transfer function of control device 7 G ₂ (s): Transfer function of pilot valve 13 G ₃ (s): Transfer function of hydraulic pipes 11 and 12 G ₄ (s): Transfer of main valve 10 Function (including main valve drive cylinder 14) G ₅ (s): Transfer function of hydraulic line 4 G ₆ (s): Transfer function of hydraulic cylinder G ₇ (s): Transfer function of detector 6 G ₈ ( s): Transfer function of the detector 18 Such a hydraulic servo device is used when it is necessary to operate and control a large volume of liquid, and at that time, the hydraulic servo device does not require high responsiveness. It was hot.

However, there are high demands for large capacity, high pressure, and high response, making it necessary to improve the response of this multistage control valve. In order to improve the responsiveness of this two-stage control valve, it is necessary to improve the responsiveness of each of the transfer functions G ₂ (s) to _{G 4} (s). Specifically, G ₂ (s) ~ adopts a high-response pilot valve G ₃ (s) ~ shortens the hydraulic pressure line and improves the hydraulic pressure characteristic value G ₄ (s) ~ reduces the mass of the main valve spool, etc. reduce It also aims to improve the spring constant and reduce hysteresis.

Problems that the invention aims to solve However, in order to improve responsiveness, the problem cannot be solved simply by increasing the responsiveness of each element; it is also necessary to improve the stability of each element. In this case, vibration of the main valve poses a particular stability problem. To solve this problem, the following measures have been taken in the past.

1. Reduce the force that occurs when hydraulic pressure flows through the main valve from the hydraulic side to the cylinder side and from the cylinder side to the tank side, that is, the flow force.

2 Detects the speed and acceleration of the main valve and provides feedback.

3 Remove with an electric filter, etc.

In this case, the measure for 1) is when the pressure is high and the capacity is large.
It is extremely difficult to eliminate it completely. 2) and 3) were problems because they were measures taken after a problem occurred, so they had little effect and could not improve basic stability.

The purpose of this invention is to provide a simple and reliable method to
To provide a hydraulic servo device equipped with a multi-stage control valve capable of effectively absorbing vibrations of a main valve and capable of stable control.

Means for Solving the Problems In order to achieve the above object, the present invention includes a hydraulic cylinder for controlling hydraulic pressure or displacement, and a control valve for controlling the liquid volume or hydraulic pressure in this hydraulic cylinder. , a hydraulic servo device consisting of a detector that directly or indirectly detects the hydraulic pressure or displacement of the hydraulic cylinder, and a control device that calculates and amplifies the output of this detector to provide an operation signal to the control valve. The control valve is a multistage control valve consisting of a pilot valve and a main valve driven by a driving piston cylinder operated by the pilot valve, and the driving piston driving the main valve divides the control valve into two chambers. The chambers are disposed through orifices either directly in each chamber of the divided drive cylinder or in the middle of each conduit connecting each chamber of the drive cylinder and the pilot valve.

Function The present invention uses a multistage control valve consisting of a pilot valve that constitutes the control valve and a main valve that is driven by a drive piston cylinder that is operated by the pilot valve, so that commands can be sent to the pilot valve. When the pressure is applied, a certain amount of liquid flows from the pilot valve into one of the hydraulic pressure lines, which increases the pressure in one chamber in the drive cylinder that drives the main valve, and moves the main valve. When the main valve moves, hydraulic pressure flows from the hydraulic pressure source (P _SM ) to the hydraulic cylinder (P _C ), but at this time, a flow force acts in the opposite direction to the direction in which the main valve moves, causing pressure to flow inside the driving cylinder. The pressure in one of the chambers increases further, which causes
The main valve starts moving again, and then the same state repeats when a flow force occurs, and when the damping of the main valve is small, vibrations and fluid pressure fluctuations occur.

That is, each hydraulic pressure line, the main valve drive cylinder, and each chamber are filled with working fluid, and this working fluid has compressibility. That is, the hydraulic fluid is compressed when the pressure is high, and expands when the pressure is low.

Now, when the main valve tries to move to the left due to the flow force, the main valve driving cylinder is also moved to the left, and one hydraulic line is compressed.
Boost the pressure. At the same time, the other hydraulic line is expanded and depressurized. This in turn causes fluid pressure fluctuations.

Therefore, in the present invention, each pipe is connected directly to each chamber of the drive cylinder, which is divided into two chambers by the drive piston that drives the main valve, or connects each chamber of the drive cylinder to the pilot valve. By disposing a chamber through an orifice in the middle of the chamber, an apparent increase in liquid volume commensurate with the increase in pressure due to fluid pressure fluctuations is released into the chamber through the orifice, or an apparent increase in fluid volume corresponding to the pressure decrease due to fluid pressure fluctuations is released into the chamber through the orifice. The reduced amount of liquid is discharged from the chamber into the conduit through the orifice to reduce pressure fluctuations, and the orifice's throttling effect further improves the damping effect.

In other words, the vibration phenomenon of the main valve of a multistage control valve is caused by pressure fluctuations caused by switching the pilot valve.
This is largely due to forced vibration caused by the flow force of the main valve. Vibrations caused by these are absorbed by the chamber and throttle, increasing the stability (damping coefficient) of the main valve.

Example A hydraulic servo device, which is an example of the present invention, is shown in the third example.
As shown in the figure.

Note that the explanation of the parts common to FIG. 1 will be omitted, and only the different parts will be explained.

This figure shows a case where a main valve drive cylinder is provided with a chamber and a throttle for each cylinder liquid chamber.

First, the vibration mechanism of the main valve due to flow force will be explained. When a command is given, a constant amount of liquid flows from the pilot valve 13 into the hydraulic line 11, thereby increasing the pressure within the cylinder 14 and causing the main valve 10 to move. When the main valve 10 moves, hydraulic pressure flows from the hydraulic pressure source (P _SM ) to the cylinder (P _C ), and at this time, the main valve 10
The flow force acts in the opposite direction to the direction in which the cylinder 14 moves, further increasing the pressure inside the cylinder 14, which causes the main valve to start moving again.Then, when the flow force occurs, the above state is repeated, and the damping of the main valve is small. Vibrations and fluid pressure fluctuations occur.

In other words, the hydraulic pressure lines 11 and 12, the main valve drive cylinder 14, and the chamber 15 are filled with working fluid, and this working fluid has compressibility. That is, the hydraulic fluid is compressed when the pressure is high, and expands when the pressure is low.

Now, when the main valve 10 tries to move to the left due to the flow force, the main valve driving cylinder 14 is also moved to the left, compressing the hydraulic pressure line 11 and increasing the pressure. At the same time, the hydraulic line 12 is expanded and depressurized.

Therefore, if the chamber 15 is provided, and the fluid pressure fluctuates, for example, toward the rising side, an apparent increase in fluid volume commensurate with the pressure increase passes through the throttle 16 and is discharged into the chamber 15. On the other hand, if the fluid pressure fluctuation is on the downward side, by replenishing the decreased fluid amount from the chamber 15 to the cylinder 14, the pressure fluctuation inside the cylinder 14 is reduced, and at the same time, the pressure fluctuation in the cylinder 14 is reduced. A damping effect occurs, damping the vibrations of the main valve.

A specific example is shown in FIG. 4 (when there is no pulsation in the hydraulic pressure lines 11 and 12). In the figure, b and c are the characteristics when there is no flow force and no chamber.
The pressure and displacement of the main valve are stable, but if there is a flow force, the pressure and displacement both oscillate greatly as shown in d and e. Therefore, when a chamber is provided, f and g become like this, and although there is an influence of the flow force, it does not vibrate and becomes stable.

Other application examples are shown in FIGS. 5 to 7. Fifth
The figure shows a chamber 15 in the middle of hydraulic pipes 11 and 12.
This is the case where a diaphragm 16 and an aperture 16 are provided. Figure 6 shows
This is a case where a chamber 15 and a throttle 16 are provided between the hydraulic pressure pipes 11 and 12. FIG. 7 shows a case where a pipe 17 and a throttle 16 are provided in the middle of the hydraulic pipeline.

Effects of the Invention According to the present invention, vibrations of the main valve can be damped by combining a multistage control valve with a chamber or a pipe and a throttle, thereby increasing the responsiveness of the multistage control valve.

[Brief explanation of drawings]

Fig. 1 is a conventional configuration diagram, Fig. 2 is a block diagram of the conventional configuration, Fig. 3 is a configuration diagram of an embodiment of the present invention, Fig. 4 is a graph showing the effects of the present invention, and Fig. 5 7 to 7 are block diagrams of other embodiments of the present invention. 1... Ram, 2... Cylinder, 3... Liquid chamber, 4
...Hydraulic pressure line, 5...Control valve, 6...Detector, 7
...control device, 8 ...command circuit, 9 ...hydraulic pressure source,
10...Main valve, 11 and 12...Hydraulic pressure line, 13...Pilot valve, 14...Main valve drive cylinder, 15...Chamber, 16
...Aperture, 17...Pipe, 18...Detector.

Claims (1)

[Scope of utility model registration request] A hydraulic cylinder for controlling hydraulic pressure or displacement, a control valve for controlling the liquid amount or hydraulic pressure in the hydraulic cylinder, and a detection system for directly or indirectly detecting the hydraulic pressure or displacement of the hydraulic cylinder. In a hydraulic servo device comprising a detector and a control device that calculates and amplifies the output of the detector and provides an operation signal to the control valve,
The control valve is a multi-stage control valve consisting of a pilot valve and a main valve driven by a drive piston cylinder operated by the pilot valve, and is divided into two chambers by the drive piston that drives the main valve. A hydraulic servo device characterized in that a chamber is disposed through an orifice directly in each chamber of the drive cylinder or in the middle of each conduit connecting each chamber of the drive cylinder and the pilot valve.