JPH0155321B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an actuator drive circuit that drives an actuator by controlling discharge pressure fluid from a pressure fluid source with a directional control valve.

In the actuator drive circuit, the actuator of the circuit drives the load, so if the start and stop times of the actuator are short compared to the inertia of the load, a shock occurs. This impact can be caused by, for example, construction machinery falling over, damage to piping, etc.
This caused various problems, such as hindering the operation of the device. As a circuit for preventing these problems, there has been an actuator drive circuit disclosed in Japanese Utility Model Application No. 53-95979.

The actuator drive circuit includes a pressure fluid circuit including a pressure fluid source, a directional control valve, and a fluid motor connected to the directional control valve via two main circuits. Two pressure control valves are provided, and the main circuit is connected to the tank via the pilot valve which is operated by a pressure difference within the main circuit. When the directional control valve is operated from the neutral position to one switching position, the pilot valve connects the pilot section of one pressure control valve and the high pressure side of the main circuit due to the pressure difference between the main circuits. However, by connecting the pilot portion of the other pressure control valve to the tank, the one pressure control valve secures fluid pressure to the fluid motor and drives the fluid motor. In this way, when the directional control valve is operated to the neutral position while the fluid motor is operating, both main circuits are closed, but the fluid in the main circuit on the discharge side of the fluid motor is transferred to the other pressure control valve. The fluid flows into the main circuit on the supply side through the main circuit on the supply side, and by maintaining the fluid pressure set by the other pressure control valve in the main circuit on the discharge side, it performs a braking action, and when the directional control valve is operated, the fluid motor This was to prevent the occurrence of impact.

In the conventional actuator drive circuit described above, when the directional switching valve is operated to one switching position to start the actuator and then the directional switching valve is operated to the neutral position, a braking force is applied by the pressure control valve. However, when attempting to control the braking force by operating the directional switching valve to the opposite switching position from the starting position during this braking operation, the hydraulic pressure of the main circuit acts on the pilot section of the pressure control valve. ,
The pressure control valve has a high set pressure, so
A large braking force is applied to the actuator.
For this reason, the braking force of the actuator cannot be controlled reliably, making it difficult to control the stop position of the actuator.

The technical means of the present invention to solve the above problems is to connect an actuator to a directional control valve to which a pressure fluid source is connected via two main circuits, and to provide a pressure control valve between these two main circuits. In the actuator drive circuit, a second circuit is provided between the main circuit, which is formed by connecting a brake valve having a pilot circuit and a check valve whose forward direction is the direction of the main circuit from the brake valve. The brake valve of a circuit is connected to a notch where the main valve of the brake valve forms a restriction between one main circuit and the other main circuit, and this notch is between one main circuit and the other main circuit. Before forming the throttle, the spring chamber to which the pilot circuit is connected is connected to the other main circuit via a check valve, and the pilot circuit of the brake valve is provided between the main circuits and has low pressure. A switching position that connects the pilot circuit of the brake valve of the second circuit connected to the main circuit on the side to the tank and closes the pilot circuit of the brake valve of the second circuit connected to the main circuit on the high pressure side, and the brake of the second circuit. The pilot circuit of the brake valve of the second circuit is connected to a pilot valve having a neutral position that closes both of the pilot circuits of the valve, and the pilot circuit of the brake valve of the second circuit is connected to the tank on the upstream side of the second circuit of the two main circuits. When the second
A residual pressure valve is provided to maintain hydraulic pressure in the main circuit to move the main valve of the brake valve of the circuit to its final end position against the spring of the spring chamber.

The present invention having the above technical means is such that when the directional control valve is operated from its central position to the switching position,
The pilot valve is switched by the main circuit on the high pressure side, connecting the pilot circuit of the brake valve connected to the main circuit on the low pressure side to the tank, and closing the pilot circuit of the brake valve connected to the main circuit on the high pressure side. do. The main circuit on the low pressure side is maintained at a predetermined oil pressure by the residual pressure valve, so the main valve of the brake valve connected to the main circuit on the low pressure side is held in the moved position. The circuit's hydraulic pressure is isolated from the low pressure side by a check valve connected to the brake valve. In this way, the main valve of the brake valve connected to the low pressure side main circuit is held in the moving position at startup, so when the directional control valve is operated from the switching position to the neutral position, the pilot valve moves to the neutral position. As a result, the pilot section of the brake valve is shut off, but in the main circuit, due to the inertia of the actuator, the high pressure side becomes low pressure and the low pressure side becomes high pressure during driving, so the main circuit of the brake valve is connected to the main circuit with the spring chamber on the low pressure side. Since it is connected to, it can be pulled to the moving position. Therefore, the hydraulic pressure due to the inertia of the actuator is controlled by the brake valve. At this time, when the directional switching valve is operated to a position opposite to the above-mentioned switching position, the amount of oil supplied to the brake valve increases, so the amount of oil passing through the notch of the main valve of the brake valve increases. As a result, the oil pressure on the upstream side of the notch increases, that is, the braking force applied to the actuator increases. Therefore,
The strength of the braking force can be controlled by a directional valve.

Hereinafter, in FIG. 1 showing a circuit diagram describing an embodiment of the present invention, an actuator drive circuit A is a main circuit 3a connected to the discharge side of a pressure fluid source 1 (hereinafter referred to as pump 1) and an actuator 4. , 3b are connected, and the neutral position 2a connects the discharge side to the tank T and closes the main circuits 3a and 3b, and the switching positions 2b and 2 to be described later.
a directional control valve 2 having a control lever 2d and a control lever 2d;
Provided between the residual pressure valves 17a, 17b provided in the main circuits 3a, 3b, respectively, and the downstream main circuits 3a 1, 3b ₁ on the actuator 4 side of the residual pressure valves 17a, 17b of the main circuits _3a , 3b. Yes, the first part will be explained later.
A circuit B formed by circuit B ₁ and second circuit B ₂ ;
It is provided between the upstream main circuits 3a 2 and 3b 2 on the directional control valve 2 side of the residual pressure valves _17a and _17b of the main circuits 3a and 3b, and the fluid pressure difference in the upstream main circuits 3a ₂ and 3b ₂ The pilot valve 13 is operated by the pilot valve 13.

The first circuit _B1 of the circuit B includes a pressure control valve 5a,
The check valve 6b is connected in series with the common circuit 18, one end of which is connected to the downstream main circuit 3a ₁ of the main circuit 3a, and the other end is connected to the downstream main circuit 3b ₁ of the main circuit 3b. The valve circuit 7a, the pressure control valve 5b, and the check valve 6a are connected in series through a common circuit 18, with one end connected to the downstream main circuit 3b 1 and the other end connected to the downstream main circuit _{3a 1 .}
The second pressure control valve circuit 7b is connected to the second pressure control valve circuit 7b. The second circuit _B2 includes the first pressure control valve circuit 7.
A brake valve 8a is provided in parallel with the pressure control valve 5a of a, and is connected to the pilot valve 13 via the pilot circuit 9a, and has one end connected to the downstream main circuit _3a1 and the other end connected to the common circuit 18. The first brake circuit 19a provided with the pressure control valve 19a is similarly provided in parallel with the pressure control valve 5b of the second pressure control valve circuit 7b, and the pilot valve 1 is connected to the first brake circuit 19a via the pilot circuit 9b.
3, one end of which is connected to the downstream main circuit _3b1, and the other end of which is connected to the common circuit 18.
The second brake circuit 19b includes a second brake circuit 19b.

The pilot valve 13 to which the pilot circuits 9a and 9b of the first and second brake circuits 19a and 19b are connected has a neutral position 10a where the pilot circuits 9a and 9b are closed, and a neutral position 10a where the pilot circuit 9a is closed to the tank T.
A switching position 10b connects the pilot circuit 9b to the tank T and closes the pilot circuit 9b; a switching position 10c connects the pilot circuit 9b to the tank T and closes the pilot circuit 9a;
Pilot parts 11a, 11b connected to upstream main circuits 3a ₂ , 3b ₂ and neutral position return springs 12a, 1
2b, and the upstream main circuit 3a ₂ ,
3b ₂ is switched to the switching position 10b or 10c depending on the fluid pressure difference with respect to the switching position 10b or 10c.

The first and second brake circuits 19a, 19b
The brake valves 8a, 8b are the brake valves 8a, 8b.
They have the same configuration as shown in FIG. 2, which is an enlarged view of the second circuit _B2 including the cross-sectional view of FIG. Therefore, only the brake valve 8a will be explained, and the brake valve 8b will be explained as necessary, using the same numbers for the same parts and adding the letter "b" as a suffix.

In FIG. 2, the brake valve 8a is connected to the main circuit 3.
Connection port 21a connected to the downstream speed main circuit 3a ₁ of a
A main valve 22a is connected to this connection port 21a.
is slidably inserted and connected to the common circuit 18.
Inner hole 2 in which each of the hole 32a and the second hole 33a opens
3a and a pilot hole 24a to which a pilot circuit 9a is connected, and a main valve 22a that is slidably fitted into an inner hole 23a of the main body 25a. The main valve 22a has a hole 28a that accommodates a spring 27a stretched between the inner hole 23a and the bottom 26a, and the connection port 21a.
A throttle 31a connects the chamber 36a connected to the hole 28a via a throttle 30a, and a hole 3 connects to the second hole 33a when the main valve 22a is retracted.
4a and a notch 35a that forms a diaphragm between the first hole 32a and the chamber 36a. The tension of the spring 27a is equal to the tension of the upstream main circuit 3a ₂
Fluid pressure which is provided between the downstream main circuit _3b1 and the downstream main circuit _3b1 and held by a residual pressure valve 17a, which will be described later, acts on the chamber 36a, and the pilot circuit 9a is activated by the pilot valve 13. This is a value that produces a pressing force that is weaker than the pressing force acting on the main valve 22a due to the fluid pressure in the chamber 36a when the main valve 22a is connected to the tank T. When the main valve 22a is connected, the hole 28a is connected to the second hole 33a, and the notch 35a forms a throttle between the chamber 36a and the first hole 32a.

Upstream main circuit 3a ₂ , 3b ₂ and downstream main circuit 3a ₁ ,
Since the residual pressure valves _17a and 17b provided between the residual pressure valve 17a and 17b have the same configuration, only the residual pressure valve 17a will be explained, and for the residual pressure valve 17b, the same numbers will be used for parts that are the same as the residual pressure valve 17a, and the alphabet "b" will be used. Subscript and describe as necessary.

The residual pressure valve 17a is installed in a direction that allows pressure fluid to pass from the downstream main circuit 3a ₁ to the upstream main circuit 3a ₂ , and applies fluid pressure to the downstream main circuit 3a ₁ to operate the main valve 22a of the brake valve 8a. a check valve 14a equipped with a spring _14a1 having the necessary tension to maintain the
It is provided in parallel with this check valve 14a, and is composed of a check valve 15a that allows pressure fluid to pass from the upstream main circuit _3a2 to the downstream main circuit _3a1 , and a throttle 16a that secures a passage area. . Therefore, when pressure fluid is supplied to the upstream main circuit 3a ₂ and the upstream main circuit 3b ₂ is connected to the tank T, the residual pressure valves 17a and 17b allow the pressure fluid in the upstream main circuit to reach the residual pressure valve 1.
7a, and flows into the actuator 4 through the check valve 15a and the throttle 16a. The discharged fluid from the actuator 4 flows into the tank T via the downstream main circuit 3b ₁ , the check valve 14b of the residual pressure valve 17b, and the throttle 16b, and the upstream main circuit 3b ₂ . At this time, a fluid pressure corresponding to the tension of the spring 14b ₁ of the check valve 14b of the residual pressure valve 17b is maintained in the downstream main circuit 3b ₁ .
When pressure fluid is supplied to the upstream main circuit 3b ₂ and the upstream main circuit 3a ₂ is connected to the tank, the residual pressure valve 1
It has a function of maintaining fluid pressure in the downstream main circuit 3a ₁ corresponding to the tension of the spring 14a ₁ of the check valve 14a of 7a.

The operation of this embodiment having the above configuration will be described with reference to FIG. 3, which shows changes in pressure in the main circuits 3a and 3b when the actuator 4 is started and stopped.

As shown in Fig. 1, the directional control valve 2 is in the neutral position 2.
In position a, the discharge pressure fluid of the pump 1 flows out to the tank T via the directional valve 2 and the main circuits 3a, 3b are closed.

Next, when the directional control valve 2 is operated to the switching position 2C to start the actuator 4, the main circuit 3a,
3b is connected to the pump 1 and the tank T. Therefore, the discharge pressure fluid of the pump 1 is transferred to the directional control valve 2, the upstream main circuit 3a ₂ of the main circuit 3a, and the residual pressure valve 17.
a check valve 15a, throttle 16a, downstream main circuit 3
A ₁ flows into the actuator 4, but since a load is acting on the actuator 4, the fluid pressure in the main circuit 3a rises as shown in part A of curve c ₁ in Figure 3. . On the other hand, actuator 4
The main circuit 3b connected to the tank T is connected to the tank T via the directional control valve 2, so that when the fluid pressure in the main circuit 3a reaches the pressure that drives the load, the actuator 4 is driven in the direction of arrow E. do. At this time, the fluid pressure in the main circuit 3a is equal to the pressure control valve 5a of the first circuit _B1 and the brake valve 8a of the second circuit _B2 .
and the pilot portion 11a of the pilot valve 13, but since the pilot circuit 9a of the brake valve 8a is closed by the pilot valve 13, its main valve 22a maintains the position shown in FIG. At this time, the pilot valve 13 is switched to the switching position 10c because the pilot part 11b is connected to the tank T via the upstream main circuit _3b2 .
Connect the pilot circuit 9b to the tank T while keeping the pilot circuit 9a closed. Pressure control valve 5
Since a is set to a value that ensures the driving pressure of the actuator 4, for example, by limiting the fluid pressure that acts upon starting the actuator to a constant level, surge pressure at the time of starting is eliminated.

When the actuator 4 starts to be driven by the supply of pressure fluid from the main circuit 3a, the discharged fluid is transferred to the downstream main circuit 3b ₁ , the check valve 14b of the residual pressure valve 17b,
It flows out to the tank T via the throttle 16b, the upstream main circuit _3b2 , and the directional control valve 2. Therefore, the fluid pressure in the downstream main circuit _3b1 depends on the tension of the spring 14b1 provided in the check valve 14b of the residual pressure valve 17b, as shown in part _d of curve c2 in _FIG . value. This fluid pressure is controlled by the pressure control valve 5b of the first circuit _B1 ,
Each acts on the brake valve 8b of the second circuit _B2 ,
The pressure control valve 5b does not operate because it has the same set value as the pressure control valve 5a described above.
However, the brake valve 8b has its pilot circuit 9
b is connected to the tank T by the pilot valve 13, so the pressure fluid in the downstream main circuit _3b1 flows through the first brake circuit 19b and the throttle 30 of the brake valve 8b.
b, chamber 36b, throttle 31b of main valve 22b, hole 28
b, flows out to tank T via pilot circuit 9b and pilot valve 13. At this time, fluid pressure is maintained in the chamber 36b by the throttle 31b, and this fluid pressure acts on the main valve 22b and pushes the main valve 22b against the spring 27b to open the notch 35b of the main valve 22b.
and hole 34b are moved until they are connected to the first hole 33b. In this way, the actuator 4
When the main circuit 3a starts to be driven in the direction of the arrow E, the surge pressure acting on the actuator 4 at the time of startup disappears, and the fluid pressure in the main circuit 3a becomes a substantially constant value as shown in part B of the curve _C1 . While the actuator 4 is being driven in this way, the main circuit 3 on the downstream side of the main circuit 3b
Since the fluid pressure in b ₁ is also maintained at a nearly constant value shown in part d of curve C ₂ by the residual pressure valve 17b, the second
The main valve 22b of the brake valve 8b of circuit _B2 remains in the state described above.

In order to stop the actuator 4 that is being driven in the direction of the arrow E, the directional control valve 2 is moved to the neutral position 2.
When switched to a, the main circuits 3a and 3b are closed and the discharge side of the pump 1 is connected to the tank T. Therefore, the supply of pressure fluid to the actuator 4 is cut off, but the actuator 4 continues to be driven in the direction of arrow E due to the inertia of the load, sucks the fluid in the main circuit 3a, and supplies the pressure fluid to the main circuit 3b. Exhale.

When the directional switching valve 2 is operated to the neutral position, the pilot valve 13 is switched to the switching position 10b by the hydraulic pressure of the main circuit 3b, and the pilot circuit 9b of the brake valve 8b is closed. However, brake valve 8
The spring chamber b is connected to the tank by a pilot valve 13 when the actuator 4 is started, and its main valve is
It is in the position moved by the residual pressure valve 17b.
Then, in this state, when the main circuit 3a becomes low voltage and the main circuit 3b becomes high voltage, the spring chamber is connected to the main circuit 3a via the common circuit 18. After this happens, the pilot circuit 9 of the brake valve 8b
b is closed, its main valve 22b remains in the moved position.

As the fluid in the main circuit 3a is sucked by the actuator 4, the fluid pressure in the main circuit 3a drops rapidly, as shown in part C of the curve _c1 . On the other hand, the discharge pressure fluid of the actuator 4 flows into the downstream main circuit 3b1 of the main circuit _3b , and this pressure fluid flows into the first brake circuit 19b,
The first from the aperture 30b, the chamber 36b, and the notch 35b.
Hole 32b and throttle 31b of main valve 22b, hole 28
b, the common passageway 1 through the hole 34b and the second hole 33b.
8. Flows into the downstream main circuit 3a ₁ of the main circuit 3a via the check valve 6a. Therefore, the fluid pressure in the downstream main circuit _3b1 of the main circuit 3b is reduced by the throttle 30b and the first hole 3.
2b and chamber 36b maintains a fluid pressure determined by the characteristics due to the throttling effect of the notch 35b formed between the notch 35b and the chamber 36b. Therefore, a braking force based on the characteristics of the brake valve _8b of the second circuit _B2 acts on the inertia of the load of the actuator 4, as shown in part E of the curve c2. Then, as the inertial force begins to decrease, the fluid pressure in the downstream main circuit 3b1 of the main circuit _3b also decreases as shown in the section G of the curve _C2 .
That is, the actuator 4 has a second circuit B ₂
The brake force from the brake valve 8b is applied to stop the vehicle without impact.

The above explanation is about the normal brake action, but in construction machinery, etc., to prevent danger,
Needs to be stopped urgently. We will discuss such a case.

By operating the directional control valve 2 from the switching position 2C to the switching position 2b on the opposite side beyond the neutral position 2a while the actuator 4 is being driven, the main circuits 3a, 3
b are connected to the tank T and the pump 1, respectively, so that both the pressure fluid due to the inertia of the load of the actuator 4 and the discharge pressure fluid of the pump 1 flow into the downstream main circuit 3b1 of the main circuit _3b . At this time, when the brake valve 8b operates the direction switching valve 2c to start the actuator 4, its pilot circuit 9
b is connected to the tank through the pilot valve 13, the main valve 22b is the residual pressure valve 17b, and the notch 35a connects the main circuit 3b and the common circuit 18. When the directional control valve 2 is operated to the switching position 2b in this state, the brake valve 8b spring chamber is connected to the second hole 33a, the common circuit 1
8. Since it is connected to the main circuit 3a via the check valve 16a, the main valve 22b maintains the position set at startup, regardless of the operating position of the pilot valve 13.

Therefore, as the flow rate of the pressure oil supplied to the main circuit 3b increases, the oil pressure on the upstream side of the main valve 22b of the brake valve 8b increases. Therefore, the fluid pressure remains at a high fluid pressure despite the decrease in load inertia, as shown in the section of curve _C2 .
That is, in the brake valve 8b of the second circuit _B2 ,
Since the discharge pressure fluid of the pump 1 is supplied according to the operation amount of the directional switching valve 2, even if the discharge pressure fluid of the actuator 4 decreases due to a decrease in inertia, the fluid pressure in the downstream main circuit _3b1 will be reduced. is held at a high pressure to apply a large braking force to the actuator 4. In this way, a large braking force is applied to the actuator 4, and the directional control valve 2 is returned to the neutral position 2a depending on the deceleration state of the actuator 4, so that the actuator 4 is stopped.

The above description has been made regarding the case where the directional switching valve 2 is operated from the neutral position 2a to the switching position 2c, but when the directional switching valve 2 is operated from the neutral position 2a to the switching position 2b, the main circuits 3a and 3b are switched to the tank T. and the pump 1, and the discharge pressure fluid of the pump 1 flows into the actuator 4 via the main circuit 3b, so the actuator 4 operates in the direction of arrow F and the pilot valve 13 moves to the switching position 10b.
The pilot circuit 9a is connected to the tank T. Therefore, the brake valve 8a of the second circuit _B2 is
Since it operates in the same manner as the brake valve 8b described above, and the braking force to the actuator 4 also operates in the same manner as described above, a detailed explanation thereof will be omitted.

As described above, the present invention provides a second circuit equipped with a brake valve having a pilot circuit between the main circuit that connects the actuator and the directional control valve, and also provides a second circuit equipped with a brake valve having a pilot circuit. a pilot valve that is activated and connects only one of the pilot circuits of the brake valve to the tank; and a residual pressure valve that maintains a pressure in the main circuit that is capable of operating the brake valve when the pilot circuit is connected to the tank. When the directional control valve is operated, the brake valve is held in the operating position by the actuator drive circuit, so that a predetermined braking force can be obtained regardless of subsequent operation of the pilot valve. In addition, once the brake valve operates to a predetermined position, it remains in that position, so by operating the directional valve from one position to the other, for example, an emergency stop or braking force corresponding to the size of the load can be applied. It has an effect on the actuator.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of the actuator drive circuit according to the present invention, Fig. 2 is an enlarged circuit diagram of the second circuit including a sectional view of the brake valve, and Fig. 3 shows the pressure in the main circuit from start to stop of the actuator. It is a line diagram showing a change. DESCRIPTION OF SYMBOLS 1... Pressure fluid source (pump), 2... Directional switching valve, 3a, 3b... Main circuit, 4... Actuator, {{5a, 5b... Pressure control valve, 6a, 6b...
...Check valve}...B ₁ first circuit, {8a, 8b...Brake valve}...B ₂ second circuit}...B...circuit,
9a, 9b...Pilot circuit, 13...Pilot valve, 17a, 17a...Residual pressure valve.

Claims (1)

[Claims] 1. In an actuator drive circuit in which an actuator is connected to a directional control valve to which a pressure fluid source is connected via two main circuits, and a pressure control valve is provided between these two main circuits, a pilot circuit is connected between the main circuits. A second circuit is provided in which a brake valve having a brake valve and a check valve whose main circuit direction is a forward direction are connected from the brake valve, and the brake valve of the second circuit is connected to the brake valve, and the main valve of the brake valve is A notch forming a diaphragm between one main circuit and the other main circuit, and a spring to which the pilot circuit connects before this notch forms a diaphragm between one main circuit and the other main circuit. The pilot circuit of the brake valve is connected to the other main circuit via a check valve, and the pilot circuit of the brake valve is provided between the main circuits and connects the pilot circuit of the brake valve of the second circuit connected to the main circuit on the low pressure side. It has a switching position that closes the pilot circuit of the brake valve of the second circuit that connects the pilot circuit to the tank and the main circuit on the high pressure side, and a neutral position that closes both the pilot circuit of the brake valve of the second circuit. When the pilot circuit of the brake valve of the second circuit is connected to the tank, the second circuit of the two main circuits is connected to the pilot valve.
An actuator drive circuit characterized by being provided with a residual pressure valve that causes the main circuit to use hydraulic pressure to move the main valve of the brake valve of the circuit to its final end position against a spring in a spring chamber.