JPH0463246B2 - - Google Patents

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. There are 3. Further, a small diameter chamber C is formed at the stroke end portion of the rod side chamber L, 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 of the rod side chamber L, so that the operating speed of the piston 1 is reduced.

(Problems to be Solved by the Invention) In the conventional apparatus as described above, there was a problem in that the pressure in the rod side chamber L became too high. In other words, the pressure in the bottom side chamber B during the above cushion stroke increases to the set pressure of the relief valve, and the pressure in the rod side chamber L becomes (relief valve set pressure x S ₁ )/(S ₁ - S ₂ ) + As it rises to the inertial pressure due to the load, it becomes a fairly high pressure.

When the pressure in the rod side chamber L 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, 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 the cushion device configured at the end of the cylinder,
For example, there are some problems that cannot be applied to hydraulic cylinders that adjust the operating stroke.

Furthermore, since the orifice consisting of a small diameter chamber and a cushion ring is fixed, it is possible to prevent the viscosity of the hydraulic oil from changing due to temperature conditions, especially when the viscosity decreases due to an increase in the temperature of the hydraulic oil. However, there was also the problem that the above-mentioned squeezing effect deteriorated, and the effectiveness of the cushion deteriorated as a matter of course.

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 in accordance with 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 according to the amount of movement of the control spool. In a hydraulic actuator cushion control device equipped with a cushion valve that exhibits a cushion effect by adjustment, the control spool controls its movement in response to an electric signal input from an electric actuator such as a proportional solenoid or a servo motor. The amount is controlled by a timer circuit that outputs a time signal at each time from the time when the hydraulic actuator enters the cushion stroke, and the opening characteristics of the control section are memorized in advance, and from the timer circuit. a target opening setting circuit that specifies the target opening of the control section at each output time; and a target displacement that outputs the target displacement of the control spool in accordance with the opening signal from the target opening setting circuit. A setting circuit is provided, and the electric actuator is controlled based on the displacement signal output from the target displacement setting circuit to adjust the opening degree of the control section.

(Operation of the present invention) With the above structure, from the time when the cushion stroke starts, the opening degree of the control part corresponding to the preset target opening degree of the control part is determined. The control spool is controlled to correspond to the opening degree.

(Effects of the Invention) Therefore, since the target opening degree can be set arbitrarily, the cushion fixing time and cushion effectiveness (deceleration rate) can be freely selected.

In addition, for example, you can freely set the cushioning effect without increasing the effective stroke of the hydraulic cylinder, and you can arbitrarily extract oil temperature conditions and adjust the cushioning effect according to those conditions. There are advantages that can be achieved.

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.
while connecting to the switching valve V through the bottom side chamber B.
A passage 12 is connected to the passage 12, and a cushion valve D is connected to the passage 12.

The above-mentioned cushion valve D has first to
Four ports 14 to 17 are formed.

The first port 14 is connected to the switching valve V via a passage 18, the second port 15 is connected to the passage 12, and the third port 15 is connected to the passage 12.
6 is connected to tank t. Furthermore, the fourth port 17 is connected to a pilot pump PP.

The main body 13 thus constructed further includes a valve hole 19.
One end of this valve hole 19 is closed with a closing member 20, while an electrically driven actuator consisting of a proportional solenoid 21 that controls the stroke amount of the push rod 21a according to the excitation current is provided at the other end. .

A control spool CS is installed in the valve hole 19, and a pilot spool PS is installed in the control spool CS so as to be relatively movable.

A spring 23 is interposed between the control spool CS and a spring receiver 22 provided on the closing member 20 side, and normally, due to the action of this spring 23, the end face of a spacer 24 provided adjacent to the proportional solenoid 21 is I am in contact with it.

Further, the pilot spool PS has a spring 25 interposed between it and the tip end surface of the rod portion 22a of the spring receiver 22, and normally this pilot spool PS comes into contact with a step portion 24a formed on the inner diameter of the spacer 24. That's what I do.

And the tip of the pilot spool PS above,
That is, the push rod 21a of the proportional solenoid 21 acts on the opposite end of the spring 25, and the specific configurations of these spools PS and CS are as follows.

That is, the control spool CS is formed with a first annular recess 26 and a control portion 27 that tapers toward the first annular recess 26 side.

When the first annular recess 26 is in the normal position shown in the figure, the first annular recess 26 is connected to the first port 14 and the second port 26.
The port 15 is communicated with the port 15 to maintain a free flow state in the flow path between the ports 14 and 15. When the control spool CS moves against the spring 23, it gradually narrows the flow path between the ports 14 and 15, and finally the control section 27
We are trying to narrow down this flow path.

In addition to the first annular recess 26, a second annular recess 28 and a third annular recess 29 are formed, as well as an annular passage 31 open to the pilot chamber 30 on the spacer 24 side.

The second annular recess 28 always communicates with the third port 16, regardless of the movement position of the control spool CS. It is connected to 33.

Further, the third annular recess 29 always communicates with the fourth port 17 regardless of the movement position of the control spool CS, but the hole 34 formed at the bottom of the annular recess 29 allows the pilot spool PS to move. It opens and closes depending on the position. In other words, when both spools CS and PS are in the normal position shown, the hole 34 is connected to the pilot spool PS.
However, when the pilot spool PS moves against the spring 25, this hole 34 and an annular groove 35 formed in the pilot spool PS communicate with each other.

Further, the annular passage 31 is connected to a control spool.
It is in constant communication with the annular groove 35 through a hole 36 formed in the CS.

A communication hole 37 is formed in the pilot spool PS, and when only the control spool CS moves to the left in the spool drawing from a state where both spools CS and PS are in the positional relationship shown, the communication hole 37 is formed in the pilot spool PS. is opened to the pilot chamber 30 side.

Therefore, when the proportional solenoid 21 is excited, the push rod 21a is adjusted according to the exciting current.
As the stroke moves, the pilot spool PS is adjusted according to the stroke amount, and the spring 2
5 to the left in the drawing.

When the pilot spool PS moves in this way, the third annular recess 29 and the annular groove 35 communicate with each other, so that the pressure oil from the pilot pump PP is transferred to the fourth annular recess 29 and the annular groove 35.
The pressure flows into the pilot chamber 30 via the port 17 → third annular recess 29 → hole 34 → annular groove 35 → hole 36 → annular passage 31, and the pressure is applied to the control spool.
Acts on the end face of CS.

When this pilot pressure is applied, the control spool
As the CS moves to the left in the drawing against the spring 23, it stops at a position where the hole 34 of the control spool CS is covered by the pilot spool PS.
In this way, the opening degree of the flow path between the first port 14 and the second port 15 is determined depending on the position where the control spool CS 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 CS moves following the pilot spool PS, and when the control spool CS catches up with the pilot spool PS and both spools CS and PS maintain the relative relationship shown, the control spool CS moves following the pilot spool PS. stops, the amount of movement of this control spool CS is proportional to the amount of movement of the pilot spool PS. The amount of movement of the pilot spool PS is proportional to the stroke of the push rod 21a as described above, but since the stroke of the push rod 21a is proportional to the excitation current of the proportional solenoid 21, the amount of movement of the control spool CS 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 figure, the oil discharged from the pump P flows through the passage 18 → first port 14 → first annular recess 26 → second port 15. It is supplied to the bottom side chamber B via the rod side chamber L.
Since the oil returns to the tank via the passage 11, the load W increases.

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

Then, when the piston 1 reaches the stroke end portion, if the opening degree of the flow path communicating with the first port 14 and the second port 15 is narrowed, in other words, the control unit 27 controls the opening of the flow path. By reducing the area, a cushioning effect can be obtained.

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 is provided with a comparison circuit cp that compares the cushion stroke start position _xp of the cylinder S with the actual operating stroke position x.
This comparator circuit _cp is
A signal of =0 is input to the timer circuit TC, and a signal of τ=1 is input to the timer circuit TC when x≦x _p when the cushion stroke position is reached.

In the above timer circuit TC, the above τ=
1 is input, a time signal T is output at each predetermined time, and the time signal T is input to the target opening degree setting circuit OC.

This target opening setting circuit OC calculates a target opening signal for the control unit 27 at each time T along a preset target opening curve from the time when the cushion stroke begins (T=0). and output it.

The target opening degree signal is input to the target displacement setting circuit DC, and the target displacement setting circuit DC calculates the target displacement of the control spool CS and outputs the target displacement signal. input to amplifier 38. The target displacement signal amplified by the amplifier 38 is sent to the proportional solenoid 21,
Input as an electrical signal.

Note that the target opening setting circuit OC includes, for example,
Detects the oil temperature in the tank and memorizes the calculation formula for correcting changes in oil viscosity due to changes in oil temperature.
The opening degree may be determined to match the viscosity of the oil.

When the electric signal is input to the proportional solenoid 21, the control spool CS moves in accordance with the signal, and the opening degree of the control section 27 is adjusted.

Since the target opening curve in the target opening setting circuit OC can be set arbitrarily, the cushion stroke time and cushion effectiveness (deceleration rate) can be set as desired.
can be freely selected.

In the above embodiment, the proportional solenoid 21 is used to operate the cushion valve, but the present invention is not necessarily limited to this proportional solenoid. Of course, a servo motor or the like may be used as long as the electric actuator is driven in accordance with the electric signal outputted from the control circuit.

[Brief explanation of the drawing]

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 cushion device. S...Cylinder, D...Cushion valve, 1...
Proportional solenoid, CS… as electric actuator
...Control spool, 27...Control unit, TC...Timer circuit, OC...Target opening setting circuit, DC...Target displacement setting circuit.

Claims (1)

[Claims] 1.Cushion control of a hydraulic actuator equipped with a cushion valve that adjusts the opening degree of the control section according to the amount of movement of the control spool, and exerts a cushion effect by adjusting the opening degree of this control section. In the device, the control spool is configured such that its movement amount is controlled in response to an electric signal input from an electric actuator such as a proportional solenoid or a servo motor, and from the time when the hydraulic actuator enters the cushion stroke,
a timer circuit that outputs a time signal at each time; and a target opening setting circuit that stores the opening characteristics of the control section in advance and specifies the target opening of the control section at each time output from the timer circuit. and a target displacement setting circuit that outputs a target displacement of the control spool according to the opening signal from the target opening setting circuit, and , a cushion control device for a hydraulic actuator that controls the electric actuator to adjust the opening degree of the control section;