JPS6182006A - Cushion controlling unit of hydraulic actuator - Google Patents

Abstract

PURPOSE:To reduce the manufacturing cost of hydraulic actuator by sensing a cushion pressure when the hydraulic actuator starts a cushion stroke, and then controlling opening of a controlling spool as to have the sensed pressure coincide with the target cushion value. CONSTITUTION:When a hydraulic actuator starts a cushion stroke, a cushion pressure P2 is sensed. The sensed pressure P2 is sent to an operating pat 38 to compute traveling speed of the controlling spool. A signal related to the speed is then integrated by a primary delay circuit 39 to calculate a displacement of a valve of the controlling spool. The controlling spool is controlled by a signal related to the valve displacement. Since the controlling pressure can be controlled to have a cushion pressure thereof coincide with the target cushion pressure, cushion pressure will be prevented from being increased to an abnormal value. The need for increasing the strength of a cylinder over demanded value will therefore be eliminated, whereby reducing the manufacturing cost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control device that exerts a cushioning effect at a stroke end portion of a hydraulic actuator such as a cylinder.

(Prior Art) The conventional cushion device shown in FIG. has been established. Further, a small diameter chamber C is formed at the stroke end portion of the rod side chamber, and when the cushion ring 3 enters the small diameter chamber C, a slight gap is created between them.

A communication hole 4 opened to the bottom side chamber B and a communication hole 5 opened to the small diameter chamber C are connected to the switching valve V.

In the conventional device as described above, when the piston 1 reaches the stroke end portion, the cushion ring 3 enters the small diameter chamber C. When the cushion ring 3 enters the small diameter chamber C in this way, a throttling effect is given to the discharge flow from the rod side chamber, so that the operating speed of the piston 1 is reduced.

(Problems to be Solved by the Present Invention) The conventional device as described above has a problem in that the pressure in the rod side chamber increases. In other words, the pressure in the bottom side chamber B during the cushion stroke increases to the set pressure of the relief valve, and the pressure in the rod side chamber is: (relief valve set pressure XS+)/(Sl 32 )
+ It rises to the inertia pressure due to the load, so it becomes a fairly high pressure.

When the pressure in the rod side chamber becomes high as described above, the pressure resistance of the cylinder must be sufficiently increased, which poses a problem of increasing costs.

Furthermore, in order to reduce the impact at the stroke end portion, the cushion stroke must be increased. However, in this case, if the length of the cylinder is not changed, its effective stroke will be shortened; if the cylinder is made longer, the effective stroke can be maintained longer, but the cost will increase accordingly.

Moreover, since this conventional device has a cushion device configured at the end of the cylinder, there is a problem that it cannot be applied to, for example, a hydraulic cylinder whose operating stroke is adjusted.

Furthermore, since the orifice consisting of a small diameter chamber and a cushion ring is fixed, if the viscosity of the hydraulic oil changes due to temperature conditions, etc., especially if the viscosity decreases due to an increase in the temperature of the hydraulic oil, the above-mentioned There was also the problem that the squeezing effect was reduced, and as a result, the effectiveness of the cushion was reduced.

An object of the present invention is to provide a device that detects the operating state of the hydraulic actuator and controls a cushion valve according to the operating state to obtain a desired cushioning effect.

(Means for Solving the Problems) In order to achieve the above object, the present invention adjusts the opening degree of the control section according to the amount of movement of the control spool, and also adjusts the opening degree of the control section. In the cushion control device equipped with a cushion valve that controls the cushion pressure of the hydraulic actuator, the control spool is configured to:
The amount of movement is controlled, and the cushion pressure is detected when the cushion stroke begins.
The pressure signal is input to the calculation section, and based on the signal, the moving speed of the control spool is calculated, and this moving speed signal is input to the first-order delay circuit, which integrates the speed signal. The valve displacement of the control spool is calculated using the control spool, and this valve displacement signal is converted into an electric signal input to the electric actuator and transmitted to the electric actuator.

(Operation of the present invention) Since the present invention is configured as described above, the opening degree of the control spool can be controlled so that the cushion pressure becomes the target cushion pressure.

(Effects of the Invention) As described above, since the cushion pressure can be controlled to the target cushion pressure, the cushion pressure will not increase abnormally. Therefore, there is no need to increase the strength of the cylinder more than necessary.

In addition, for example, the cushioning effect can be set freely without increasing the effective stroke of the hydraulic cylinder.Moreover, by arbitrarily extracting oil temperature conditions, etc., the cushioning effect can be adjusted according to the conditions. It has the advantage of being adjustable.

Furthermore, even if this device is used in a hydraulic cylinder whose stroke is adjusted, it does not have any effect on the stroke adjustment.

(Embodiment of the present invention) Fig. 1 is a circuit diagram of the present invention, in which a rod side chamber of a cylinder S for raising and lowering a load W is connected to a switching valve V via a passage 11, while a bottom side chamber B is connected to a switching valve V through a passage 11. In addition to connecting the passage 12, a cushion valve is connected to the passageway 2.

The cushion valve has first to fourth ports 14 to 17 formed in its main body I3.

And the above ml boat! 4 is connected to the switching valve V through the passage I8, the second boat 15 is connected to the passage 12, and the third port XB is connected to the tank T. Furthermore, the fourth boat 17 has a pilot pump ρ
Connected to P.

The main body made like this! 3 is roughly formed with a valve hole I9, and one end of this valve hole I9 is closed with a closing member 2°, while the other end is closed with a button 1" according to the excitation current.
21 Proportional solenoid 2 that controls the stroke amount of a
An electrically driven actuator is also provided.

A zero control spool C8 is installed in the valve hole I3, and a pilot spool PS is installed in the control spool C5 so as to be relatively movable.

A spring 23 is interposed between the control spool C8 and a spring receiver 22 provided on the closing member 2o side, and normally the proportional solenoid 21 is operated by the action of this spring 23.
The spacer 24 is brought into contact with the end face of the spacer 24 provided adjacent to the spacer 24 .

Furthermore, the pilot spool PS has a spring receiver 22.
A spring 25 is interposed between the pilot spool PS and the tip end surface of the a-shaped portion 22a, and normally this pilot spool PS comes into contact with a stepped portion 24a formed on the inner diameter of the spacer 24.

A proportional solenoid 2 is placed at the tip of the biloft spool PS, that is, at the end opposite to the spring 25.
The specific configuration of both spools PS and C5 is as follows.

That is, the control spool C8 has a first annular recess g82.
8, and a control portion 27 that is disposed toward the front side toward the first annular recess 2B.

When the first annular recess 2B configured as described above is in the normal position shown in FIG. maintain. When the control spool C8 moves against the spring 23, it gradually narrows the flow path between both ports 14 and 15, and finally the control section 2
7 to narrow down this flow path.

In addition to the first annular recess 26, a second annular fourth portion 2B is also provided.
, while forming the third annular recess 29, the spacer 24
An annular passageway 4 is opened to the pilot chamber 30 on the side and forms a passageway.

The second annular recess 2B always communicates with the third port 1B regardless of the movement position of the control spool C5, and via the hole 32 formed at the bottom of the annular recess 2B,
It communicates with the hollow portion 33 of the control spool C5.

Further, the third annular portion 29 always communicates with the fourth port 17 regardless of the movement position of the control spool C5, and the hole 34 formed at the bottom of this annular portion 23 allows the pilot spool PS to move. It opens and closes depending on the position. That is, when both spools cs and ps are in the normal position shown in the figure, the hole 34 is covered by the pilot spool PS, but when the pilot spool PS moves against the spring 25, the hole 34 and the pilot spool PS are closed. The annular groove 35 communicates with the annular groove 35.

Further, the annular passage 31 is always in communication with the annular groove 35 through a hole 36 formed in the control spool C5.

A communication hole 37 is formed in the pilot spool PS, and when only the control spool C8 moves to the left in the spool drawing from a state where both spools AS and PS are in the positional relationship shown, the communication hole 37 is formed in the pilot spool PS. is pilot room 30
It is designed to open on the side.

When the proportional renoid 21 is excited, the bushing rod 21a strokes in accordance with the exciting current, and the pilot spool ρS is moved leftward in the drawing against the spring 25 in accordance with the stroke amount.

When the pilot spool PS moves in this way, the third
Since the f5-shaped recess 29 and the annular groove 35 communicate with each other, the pressure oil from the pilot pump Pρ is transferred from the fourth boat 17 to the third boat.
It flows into the pilot chamber 30 via the annular recess 28 → hole 34 → annular groove 35 → annular passage 3B → the annular passage 31, and its pressure acts on the end surface of the control spool C5.

When this pilot pressure acts, the control spool C8 moves to the left in the drawing against the spool 23, and the hole 34 of the control spool C8 opens into the pilot spool P.
Stop at the position blocked by S. In this way, the opening degree of the flow path between the first boat 14 and the second boat 15 is determined depending on the position where the control spool C8 stops, but it is ultimately proportional to the exciting current of the proportional solenoid 21, The opening of the road will be narrowed down.

In other words, the control spool C8 moves following the pilot spool PS, the control spool C8 catches up with the pilot spool PS, and both spools cs
, ps maintain the illustrated relative relationship, the control spool C5 stops, so the amount of movement of the control spool C5 is proportional to the amount of movement of the pilot spool PS. The amount of movement of this pilot spool PS is proportional to the stroke of the bushing rod 21a as described above, but since the stroke of this bushing rod 21 & is proportional to the exciting current of the proportional solenoid 21, the amount of movement of the control spool C5 is , is proportional to the excitation current of the proportional solenoid 21.

Now, when the proportional solenoid 21 is de-energized and the switching valve V is switched to the left side position in the drawing, the oil discharged from the pump P will flow from the passage 18 to the first port 14 to the first annular recess 2B 4 to the second port. The oil in the rod side chamber is supplied to the bottom side chamber B via H5, and the oil in the rod side chamber returns to the tank via the passage 11, so that the load W increases.

Also, when the switching valve V is switched to the right position in the drawing, the pump P
Pressure oil is supplied to the rod side chamber, and hydraulic oil in the bottom side chamber B is supplied to the passage 12 → second port 15 → first annular recess 26 → first boat 14 → passage 18 pass switching valve V
It returns to tank T via , and the load W is lowered.

Then, when the piston l reaches the stroke end, the first port! 4 and the second bow H5, in other words, if the control unit 27 reduces the opening area of the flow path.

You can get the Cushigon effect.

The control circuit shown in FIG. 1 controls the excitation current of the proportional solenoid 21 in order to determine the opening degree of the control section 27.

This control circuit has an arithmetic unit 38 and a first-order lag circuit 39 as main elements, and outputs a signal from this -order lag circuit 33 to an amplifier 4.
0 to the proportional solenoid 23, so that an exciting current corresponding to the signal can be obtained.

Furthermore, this control circuit is provided with a comparison circuit cp, which compares the cushion stroke start position XO of the cylinder 5 (7) with the actual operating stroke position X, xo=X When the opening/closing part 4 is detected,
1 is closed and the pressure signal P2 of the bottom side chamber B is sent to the calculation unit 38.
I am trying to input it into .

When the pressure signal P2 is input to the calculation unit 3B as described above, the difference between the pressure signal P2 and the target pressure signal Pc is calculated, and the calculation result is input to the first-order lag circuit 39.

The minus-order delay circuit 39 multiplies the difference by γ, which is a coefficient for the moving speed, to obtain the moving speed. That is,
Find ci=γ(Pl−Pc).

Then, this t is further integrated to calculate the displacement of the control spool C5, and this valve displacement signal is sent to the amplifier 4.
0, and is input to the proportional solenoid 21 as an exciting current.

That is, the comparison circuit Cp detects that the cylinder S has entered the cushion stroke, and during that time period, the control unit 27 of the control spool C5 is opened so that the cushion pressure P2 becomes the target cushion pressure Pc. Control the degree.

Since the cushion pressure can be controlled in this way, the cushion pressure will not increase abnormally.

In the above embodiment, the proportional solenoid 21 is used to operate the cushion valve, but it is not necessarily limited to this proportional solenoid. Of course, a servo motor or the like may be used as long as it is an electric actuator for driving.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention; FIG. 1 is a circuit diagram, FIG. 2 is a sectional view of a cushion valve, and FIG. 3 is a sectional view of a conventional cooker. . S...Cylinder, D...Cushion valve, 21...
Proportional solenoid as electric actuator, C5...
Control spool, 27...control unit, 38...calculation unit,
38...-Next delay circuit.

Claims (1)

[Claims] By adjusting the opening degree of the control section according to the amount of movement of the control spool, and adjusting the opening degree of this control section,
In the cushion control device equipped with a cushion valve that controls the cushion pressure of the hydraulic actuator, the control spool has a configuration in which the amount of movement thereof is controlled in response to an electrical signal input from the electric actuator, and a cushion stroke that controls the cushion stroke. When it enters the cushion, the cushion pressure is detected, the pressure signal is input to the calculation section, the moving speed of the control spool is calculated based on that signal, and this moving speed signal is input to the first-order delay circuit. This circuit integrates the speed signal to calculate the valve displacement of the control spool, converts this valve displacement signal into an electric signal input to the electric actuator, and transmits the signal to the electric actuator. Actuator cushion control device.