JPS5848763B2 - Actuator brake circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an actuator brake circuit.

Conventionally, this type of brake circuit is shown in Fig. 6 (
Utility Model Publication No. 52-74996).

The brake circuit Ia shown in FIG. 6 includes an actuator 6 (
Hereinafter, it will be referred to as a hydraulic motor 6.

), a hydraulic pump 1 is provided in a drive circuit for a hydraulic motor 6, which is connected to the switching valve 2 through supply and discharge pipes 4 and 5, and to which the supply and discharge pipes 4 and 5 and a discharge pipe 20 are connected. .

This brake circuit Ia is equipped with a balance piston type relief valve R3, and the inlet side of this IJ-F valve R3 is connected to the supply/discharge pipes 4 and 5 via a check valve 8at8a', and the outlet side is , and is connected to the tank 3 via the supply and discharge pipes 4 and 5 and the discharge pipe 20 via check valves 15a and 15a'.

This brake circuit operates when the hydraulic motor 6, which operates the switching valve 2 to the switching position b shown in the figure, is driving in the direction of the arrow b.
When the switching valve 2 is operated to the neutral position, the discharge side of the hydraulic pump 1 is connected to the tank 3, and the supply and discharge pipes 4 and 5 are cut off.

For this reason, the supply and discharge of pressure oil to the hydraulic motor 6 is cut off, but the hydraulic motor 6 is connected to a driven object (for example, a boom of a construction machine) driven by the hydraulic motor 6.

), even if the pressure oil supply and discharge is cut off, the hydraulic motor 6 is driven in the direction of the arrow b1 by the inertia of the driven body. Pressure oil is sent to 5.

This pressure oil is transferred from the discharge pipe 20 to the tank 3 via the check valve 8a' of the brake circuit Ia and the IJ-F valve R3.
Therefore, the hydraulic pressure in the supply/discharge pipe 5 is maintained at the set pressure of the IJ-F valve R3, and the hydraulic motor 6 is
A brake force corresponding to the set pressure of the IJ valve R3 is applied.

Relief valve R3 used in this brake circuit Ia
Since this is a balanced piston type, the override pressure of the override characteristic is small, resulting in a sudden change as shown by the dotted line in FIG.

Therefore, if the set pressure of the IJ IJ valve R3 is set to a high pressure, the hydraulic pressure in the supply/discharge pipe 5 will be maintained at a high pressure despite the decrease in the inertia of the hydraulic motor 6, and the brake pressure will be reduced by the inertia. becomes large, the hydraulic motor 6 is abruptly stopped, and a shock is generated.

In order to prevent this impact, if the setting pressure of the IJ IJ valve R3 is set to a low pressure, the brake force will be weakened and the switching valve 2
This increases the time from when the hydraulic motor 6 is switched from the switching position b to the neutral position a until the hydraulic motor 6 stops, making it difficult to control the stopping position of the hydraulic motor 6.

The technical object of the present invention is to reduce the braking force in an actuator drive circuit in accordance with the reduction in the inertia force acting on the actuator, and to stop the actuator in a short time without generating a shock. .

The first technical means to solve this technical problem is
A balance piston type first relief valve and a second relief valve are provided in parallel between the supply and discharge pipes connected to the actuator or between the supply and discharge pipe and the discharge pipe, and the set pressure of the first relief valve is set. The pressure is set higher than the set pressure of the second relief valve, and a throttle is provided on the inlet side of the second relief valve.

With this technical means, the supply and discharge of pressure oil to the actuator is cut off, and when the inertia force acting on the actuator is large, high flow rate and high pressure pressure oil acts on both the first and second relief valves. Since the flow rate passing through the second relief valve is restricted by the throttle, it reaches the set pressure of the first relief valve, and a brake force corresponding to the set pressure of the first relief valve acts on the actuator.

When the inertial force acting on the actuator is reduced by this brake force, the first relief valve limits the flow rate according to its override characteristic, but since the second relief valve is in the operating state, the flow rate passes through the second relief valve. The flow rate is limited by the throttle, so the actuator has
A braking force is applied due to the characteristics of this aperture.

In this way, the brake force acting on the actuator is
It is decreased in accordance with the decrease in inertial force, and when the oil pressure in the supply and discharge pipe reaches the set pressure of the second relief valve, the operation of the second relief valve is stopped and the actuator is stopped.

In this way, according to this technical means, after the supply and discharge of pressure oil to the actuator is cut off until the actuator stops, a brake force is applied in accordance with the decrease in inertia force, so that the actuator is stopped when the actuator stops. This prevents the occurrence of impact and shortens the time it takes for the actuator to stop.

The present invention having the above-mentioned precepts has the following unique effects.

In the conventional brake circuit Ia shown in FIG. 6, the relief valve R3 is a direct-acting type IJ valve, and the override pressure of the override characteristic is set to a large value.
It is possible to obtain a brake force corresponding to a reduction in inertial force acting on the actuator.

However, the direct-acting type IJ IJ-F valve has a structure in which the pressing force of hydraulic pressure and the pressing force of spring act against the main valve, and in order to increase the override pressure, it is necessary to It is necessary to increase the amount of movement of the main valve to reduce the change in the opening area formed by the main valve, but as the main valve moves, the pressing force of the spring changes, and as the opening area formed by the main valve increases. Since the pressing force of the spring increases, the pressing force of the hydraulic pressure acting on the main valve and the pressing force of the spring are balanced by increasing or decreasing the opening area, so the main valve is likely to vibrate. It becomes impossible to obtain stable braking force.

As another means, as shown in FIG. 6, a circuit 2b in which a throttle S and a spool-type switching valve 2a are connected in series is provided in parallel with the IJ IJ-F valve R3, and the spool-type switching valve A configuration is conceivable in which one end of the spool 2a is pressed by a spring and a pilot oil pressure is applied to the other end, and the operating pressure of the spool-type switching valve 2a is set to a value smaller than the set pressure of the IJ-F valve R3.

However, even with this technical means, the spring force and hydraulic pressure act oppositely on the spool-type switching valve 2a via the spool, so changes in the hydraulic pressure near the operating set pressure of the spool-type switching valve 2a The spool of the spool-type switching valve 2a vibrates, making it difficult to obtain stable braking force as described above.

The present invention uses two balance piston type relief valves, and sets one of the set pressures of the two IJ-IJ- valves to a higher pressure than the other, and sets the IJ-IJ- valve to a lower pressure.
Install a restriction on the upstream side of the valve, or install a low-pressure IJ.
The main valve of the IJ-F valve forms a throttle when the IJ-F valve is operated.

In the balance piston type relief valve, pressure oil flows through the throttle hole of the main valve when the pilot valve is operated, and the main valve is operated by the pressure difference created before and after the throttle hole due to the flow of pressure oil. Because of this, there is no change in the pressing force of the spring against the main valve, resulting in extremely stable operation.Furthermore, the low-pressure IJ-F valve is activated at the same time as the high-pressure IJ-IJ-F valve is activated, and the hydraulic pressure is increased. is a low pressure IJ
Until reaching the IJ-F valve, the brake force is applied based on the characteristics of the throttle, and since it is possible to eliminate elements that vibrate in response to pressure fluctuations, a stable brake force can be obtained.

Hereinafter, actual winding examples of the present invention will be described.

In FIGS. 1 and 2, ■ is a brake circuit, and ■ is a switching valve unit.

The switching valve unit ■ is mainly composed of a conventionally well-known switching valve 2, and is provided between the side of the hydraulic pump 1 and tank 3 and the side of the supply and discharge pipes 4 and 5 for the hydraulic motor 6. , the connection between them is switched and cut off.

11 is a check valve, 12 is an IJ-F valve, and 15 is a check valve for preventing cavitation.

The switching valve 2 can take three switching positions: a neutral position a in which the hydraulic motor is shut off, a normal rotation position b in the hydraulic motor, and a reverse rotation position C.

Note that the hydraulic motor 6 is assumed to rotate the boom.

One set of brake circuits is provided for each of the forward and reverse rotations of the hydraulic motor 6, and it is connected to the first relief valve R.
1 and a second relief valve R2, and a first relief valve R'1 and a second relief valve R'2.

The first relief valves R1 and R' have the same structure and have the same override characteristics.

The first relief valves R, , R'1 have a set pressure of 140, and the second relief valves R2 and R'2 have a set pressure of 70 to 70. 'have.

, the specific structure of the first and second relief valves R1 and R2. An example of this structure is shown in Figure 2.

As seen in the figure, the first relief valve R is a balanced piston type equipped with a main valve 9 and a boppet valve 10. The valve 10 is opened, the main valve 9 is opened, and the outlet pipe line 2 is opened.
Hydraulic pressure is released to the 0 side.

Further, the second relief valve R2 is provided with a throttle 7 in front of the main valve 9.

The existence of the throttle 7 is such that when the main valve 9 opens, the opening area of the second relief valve R2 is such that the amount of flow to the outlet side is gradually increased while the oil pressure rises beyond the set pressure of 70°C. I have to.

In other words, the second relief valve R2 starts to flow out to the outlet side when the rising oil pressure reaches nearly 70 degrees, and the throttle 7 gradually increases the amount of outflow as the oil pressure increases, and when the oil pressure reaches about 1405, the amount of outflow reaches its maximum. (201/Irult').

The characteristics when the first and second relief valves R1 and R2 are installed in parallel are shown in FIG. 3.

In addition, 8 and 8' in FIG. 1 are check valves, 20 is the first,
This discharge pipe is common to the second relief valves R1, R2, R'1, and R'2.

In the hydraulic circuit configured in this way, when the switching valve 2 is in the switching position of the neutral position a, the supply/discharge pipes 4 and 5 are cut off, and the oil discharged from the hydraulic pump 1 is transferred to the tank 3 via the switching valve 2. and the hydraulic motor 6 is stopped.

Next, when the switching valve 2 is set to the normal rotation position b or the reverse rotation position C, the oil discharged from the hydraulic pump 1 passes through the switching valve 2 and through either of the supply/discharge pipes 4 and 5. It is supplied to the hydraulic motor 6, rotates the hydraulic motor 6, passes through the other supply and discharge pipe, passes through the switching valve 2 again, and is discharged into the tank 3.

The boom rotates due to the rotation of the hydraulic motor 6.

When the switching valve 2 is returned to the neutral position a to stop the boom at a predetermined position, the supply and discharge pipes 4 and 5 are shut off as described above.

As a result, the hydraulic motor 6 tries to stop rotating because pressure oil is not supplied, but the boom tries to rotate further due to inertia, so for example, until now, hydraulic pressure has not been supplied to the hydraulic motor 6 from the supply/discharge pipe 4. If motor 6
Since both receive rotational force from the boom in the same direction, the oil pressure in the supply/discharge pipe 5 will rise rapidly.

This pressure acts as a brake force, overcoming the boom's inertia and stopping the boom.

In that case, the first and second relief valves R1 and R2 act as follows.

That is, as shown in FIG. 4, the neutral position a of the switching valve 2
By switching to , supply and discharge pipes 4 and 5 are cut off, but
Since the motor 6 continues to rotate due to the inertia of the boom,
The oil pressure in the supply/discharge pipe 5 begins to rise.

When this oil pressure reaches the cracking pressure of the pilot valve 10 of the second relief valve R2 (value 50 in Fig. 3 b1), the pilot valve 10 leaves the valve seat, but increases further and the second relief valve R2 Set pressure (value 70 in Figure 3 b2)
At 5), the main valve 9 is completely removed from the valve seat, and the pressure oil in the hydraulic supply/discharge pipe 5 begins to flow out to the pipe 20 via the throttle 7 and the second relief valve R2.

However, since the inertia of the boom has not been sufficiently reduced, the oil pressure in the supply and discharge pipe 5 continues to rise, and the pressure increases to the cracking pressure of the first relief valve R1 (the value of approximately 1 in b3 in Figure 3).
20), the pilot valve 10 is removed from the valve seat and the oil pressure continues to rise, causing the main valve 9 of the first relief valve R1 to rise.
begins to move away from the valve seat.

Therefore, the pressure oil in the hydraulic supply and discharge pipe 5 is removed from the first relief valve R1.
The relief flow starts to flow out to the pipe line 20 via the throttle 7 and the second relief valve R2, but the relief flow flowing out via the throttle 7 and the second relief valve R2 is reduced by the throttle 7 to reduce the hydraulic pressure in the supply/discharge pipe 5. When the IJ flow rate reaches the value b (2 0 17 mm), the first relief is controlled by the relief flow rate flowing out through the throttle 7 and the second relief valve R2 against the subsequent pressure increase. Since the relief flow rate flowing out through the valve R1 increases, the subsequent increase in oil pressure increases according to the override characteristic of the first relief valve R1.

In this way, the oil pressure in the supply/discharge pipe 5 is
When the set pressure of the J-F valve R1 (value 140% in Figure 3 b3) is reached, the main valve 9 is completely separated from the valve seat and the hydraulic pressure in the supply and discharge pipe 5 is maintained at 140%. do.

When the oil pressure in the supply/discharge pipe 5 rises to 140 or higher, a brake force corresponding to this oil pressure acts on the hydraulic motor 6, so that the inertia of the boom begins to decrease.

When the rotational force and rotational speed of the hydraulic motor 6 begin to decrease due to the decrease in inertia of the boom, the hydraulic pressure in the supply/discharge pipe 5 becomes
The first relief valve R1 decreases according to the override characteristic (curve C/ in FIG. 3) and the characteristic of the throttle 7 (FIG. 3e).

Therefore, the swinging speed of the boom also decreases as shown by curves B and D in FIG.

When the hydraulic pressure in the supply/discharge pipe 5 reaches the cracking pressure of the second relief valve R2, the pilot valve 10 is seated, so the hydraulic supply/discharge pipe 5 is completely shut off and the motor 6 is also stopped. .

In addition, when the boom turns in the opposite direction to the above and stops, the state is switched so that the hydraulic pressure is supplied from the supply and discharge pipe 5 to the hydraulic motor 6 and is discharged from the supply and discharge pipe 4 to the pump 3. Since it is shut off by the valve 2, the pressure inside the supply/discharge pipe 4 increases.

This state occurs when the first and second relief valves R/1R'
2 operates, so its explanation will be omitted.

Next, we will discuss other actual cases.

In another practical example, a second relief valve R"2 is used instead of the throttle 7 and the second relief valve R2 of the practical example shown in FIG. 2, and the IJ IJ-F valve shown in FIG. It is used.

This second relief valve R! 2, as shown in Figure 7a,
A notch 11 is provided in the main valve 9, and this notch 11 is
When the main valve 9 is in the non-operating position, as shown in FIG. 7a, it is closed by the inner hole of the main body, and when the main valve 9 is in the operating position, as shown in FIG. 7b, it forms a throttle. It is.

In a brake circuit in which the second relief valve R''2 is provided in place of the second relief valve R2 and the throttle 7, when hydraulic pressure due to inertia of the boom acting on the hydraulic motor 6 acts, the first relief valve R''2 and the second relief valve Both valves R"2 operate simultaneously, and as the inertia of the hydraulic motor 6 decreases, the supply/discharge pipe 5
The oil pressure decreases according to the override characteristic (Fig. 3 c/ ) of the first relief valve R1, and when the inertia force further decreases, the notch 1 provided in the main valve 9 of the second relief valve R"2 decreases.
1 (FIG. 3C), the same effect as in the case of the first actual winding example is performed.

In the above actual hoisting example, two sets of brake circuits were provided because the actuator was used for boom rotation, but in cases where inertia force acts only in one direction, such as in a hoisting winch, it is necessary to One set is sufficient, and the discharge side pipe line 20 in the above-mentioned practical example is connected to the tank.

[Brief explanation of the drawing]

Fig. 1 is a hydraulic circuit diagram showing one actual example of the present invention, Fig. 2 is a longitudinal cross-sectional view showing one example of the specific structure of the IJ valve of the same example, and Fig. 3 is the same example. Figure 4 is a diagram showing the characteristics of the brake circuit in the case; Figure 4 is a diagram showing the temporal changes in the internal pressure of the pipe during braking in the same vertebra; Figure 5 is the diagram showing the temporal changes in pressure and boom rotation speed. Diagrams showing changes, FIG. 6 is a conventional brake circuit diagram, and FIG. 7a is I of another practical example of the present invention.
FIG. 7b is a cross-sectional view of the main part of the JIJ-F valve, and FIG. 7b is a cross-sectional view of the operating state shown in FIG. 7a. 1...Hydraulic pump, 2...Switching valve, 3
...Oil tank, ■...Switching valve unit, 4, 5...Hydraulic supply and discharge pipe, 6...Actuator (hydraulic motor), 7, 7'... Throttle, 8, 8'... Check valve, 9... Main valve, 11... Notch, 20...・Pipeline,
■・・・Brake circuit, R1, R'・・・・・・
First relief valve, R2, R'2... Second relief valve, R"2... Second relief valve.

Claims (1)

[Claims] 1. In an actuator drive circuit equipped with an actuator connected to a hydraulic pump via a switching valve and a supply/discharge pipe, a balance piston type actuator is installed between the supply/discharge pipe or between the supply/discharge pipe and the discharge pipe. The first relief valve and the second relief valve are provided in parallel, and the set pressure of the second relief valve is set higher than the set pressure of the second relief valve, and a throttle is provided on the inlet side of the second relief valve. Actuator brake circuit.