JPS59217001A - Hydraulic passage for driving inertia mass - Google Patents

Abstract

PURPOSE:To prevent cavitation by constituting a change-over valve in such a manner that a third opening and closing part is closed in preference to a first opening and closing part, and a second opening and closing part is opened after the first opening and closing part is closed, when an actuator is reduced in speed. CONSTITUTION:In a first opening and closing part 29, a second opening and closing part 31 and a third opening and closing part 32 of a change-over valve 4, dimensions represented by x1 to x4 and y1 to y4 in the drawing are selected so as to satisfy the equations y2>x2, y4>x4 and y3>x3 when y1<x1 holds, the equations x2>y2 and x2-y2>y1-x1 when y1>=x1 holds, and the equations x4>y4, y3>x3 and ¦y4-x4¦+¦x3-y3¦> ¦x2-y2¦ when x2>=y2 holds. Accordingly, relief pressure of a hydrauric pump can be enclosed in passages connected to an actuator, when the speed of the actuator for driving inertia mass is reduced. Therefore, the supply of oil is unnecessary and the generation of cavitation can be surely prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inertial mass driving hydraulic path equipped with an actuator that drives a large inertial mass, such as a hydraulic motor that drives a revolving body of a hydraulic excavator.

1. In FIG. 1 showing an example of a conventional hydraulic circuit for driving an inertial mass, 1 is an actuator that drives a large inertial mass, for example, a hydraulic motor that drives a rotating body of a hydraulic excavator, and 2 is a hydraulic motor that drives a large inertial mass. Hydraulic pump that supplies pressure oil,
3 is a prime mover that drives this hydraulic pump 2. 4 is a closed center type normal position switching valve; 5 is a pipe connected to the discharge side of the hydraulic pump 2; the discharge side is connected to the neutral position 1'' of the switching valve 4; The pipe 7 is connected to the tank connecting pipe 6 through the pipe T.The pipe 7 is connected to the tank connecting pipe 6 through which the pipe 5 is also branched and communicated with one of the input ports (a) of the switching valve 4.The pipe 8 is connected to the tank connecting pipe 6 to prevent backflow. , 9 is a conduit that communicates the other input port b of the switching valve 4 with the tank communication conduit 6. 10 is an IJ IJ- which sets the maximum pressure of the conduit 5. This valve is interposed in the pipe line 11 that communicates the pipe line 5 and the tank communication pipe line 6. 12 is the first boat of the hydraulic motor 1, that is, one intake/discharge port and one output of the switching valve 4. A pipe line 13 communicates with the boat C, the second boat of the hydraulic motor 1, that is, the other intake and discharge port, and the switching valve 4.
This is a conduit that communicates with the other output boat d. 14
is a differential pressure type IJ-F valve that sets the maximum pressure of the pipe line 12, and is interposed in the pipe line 15 that connects the pipe line 12 and the pipe line 13. Reference numeral 16 denotes a differential pressure relief valve that sets the maximum pressure of the pipe line 13, and is interposed in the pipe line 17 that connects the pipe line 12 and the pipe line 13. Reference numerals 18 and 19 indicate check valves, which are interposed in a pipe line 21 and a pipe line 22 branched from a pipe line 20 communicating with the pipe line 6, respectively, and supply oil from a tank 23 to the pipe line 12 and the pipe line 13. .

FIG. 2 is a sectional view showing the structure of the above-mentioned normal position switching valve 4, and this figure shows the neutral state. The pipe line 24 shown in FIG. 2 is connected to the above-mentioned pipe line 5, and thus communicates with the hydraulic pump 2. The pipe line 25 is connected to the tank connecting pipe line 6 mentioned above.
and communicates with the tank 23. The pipe 26 communicates with one output port (c) of the switching valve 4, and communicates with one intake/discharge port of the hydraulic motor 1 via the pipe 12. The pipe line 21 communicates with the other output port () d of the switching valve 4, and communicates with the other intake/discharge port of the hydraulic motor 1 via the pipe line 13. 28 is a spool which, when moved in the X direction in FIG. 2, is switched to position B in FIG. 1. Note that 29 is a first opening/closing part formed between the main body of the switching valve 40 and the spool 28;
and the pipe line 26, that is, the hydraulic motor 1
The pipe connecting one of the suction and discharge ports with the hydraulic pump 2 is opened and closed. In addition, 30.31 is the switching valve 40 main body and the spool 28
The second opening/closing part formed between the conduit 24 and the conduit 2
5, that is, the pipe connecting the hydraulic pump 2 and the tank 23. 32 is a switching valve 4
A third opening/closing part formed between the 0 main body and the spool 28, which connects the pipe line 27 and the pipe line 25, that is,
The pipe connecting the other suction and discharge port of the hydraulic motor 1 and the tank 23 is opened and closed. In addition, 33 is a check valve provided in the middle of the pipe line which communicates the pipe line 24 and the pipe line 26.

In a conventional inertia lock drive hydraulic circuit having such a normal position switching valve 4, in order to drive the inertia lock,
When the switching valve 4 is switched to the 8th position 1h° using the operating lever, the discharge i11 of the hydraulic pump 2! The pipe line 5 of l is connected to the pipe line 12 via the pipe line 7 and the input port a and the input port C of the switching valve 4, and the communication between the hydraulic pump 2 and the tank communication pipe line 6 is blocked by the switching valve 4. be done. As a result, the pressure oil of the hydraulic pump 2 is guided to the hydraulic motor 1 and attempts to operate the inertial mass via the hydraulic motor 1. However, since the inertial force due to the inertial mass is acting on the hydraulic motor 1, the rotation speed of the hydraulic motor 1 does not suddenly increase, and the pipe line 1
2. High pressure is generated. When this high pressure exceeds the set value of the relief valve 14, it is relieved to the pipe line 13 via the relief valve 14 and the pipe line 15. When the acceleration state ends, the hydraulic motor 1 enters a steady speed state and operates at a constant speed.

From this state, when the operating lever returns the switching valve 4 to the neutral position N, which is the state shown in FIG.
is closed by the switching valve 4.

At this time, the hydraulic motor 1 remains in an operating state due to the inertial force of the inertial mass, and discharges the oil sucked in from the pipe line 12 to the pipe line 13. For this reason, the pipe line 13 becomes high pressure, and when this high pressure exceeds the set value of the relief valve 16, the relief valve 1
6 and conduit 17'? : Relieve pressure oil to the pipe line 12 through the pipe. Further, the hydraulic motor 1 is gradually decelerated due to the high pressure in the conduit 13.

Next, a description will be given based on the second and third factors and FIG. 1, which are cross-sectional views showing the structure of the above-mentioned normal position switching valve 4 in an operating state. Note that FIG. 2 shows the neutral state as described above, and FIG. 3 shows the state where the B position has been switched.

When the switching valve 4 is switched to the B position as shown in Fig. 3,
The pipe line 24 communicating with the pipe line 5 on the discharge side of the hydraulic pump 2 shown in FIG.
It communicates with the conduit 26 via the opening/closing part 29 . The conduit 26 is connected to the aforementioned conduit 12. Further, the pipe line 27 that communicates with the pipe line 13 mentioned in Ml is connected to the pipe line 25 via the third opening/closing part 32 which is in an open state and the pipe line 34.
Ru. Note that the three passages 25 communicate with the tank communication pipe 6.

- the pipes 24 and 25 communicating with the hydraulic pump 2,
It is blocked by the second opening/closing part 30.31 in the closed state.

Then, while the hydraulic motor 1 is operating, the switching valve 4 is moved to the neutral position [
When the switch is returned to N and the brake is applied, the switching valve 4 will be in the state shown in FIG. That is, the conduits 12 and 13 are closed when the first opening/closing section 29 and the opening/closing section 32 of @3 are closed, and the conduits 24 and 25 are closed when the opening/closing section 32 of
is opened, communication occurs, and the pressure oil discharged from the hydraulic pump 2 flows into the tank 23.

Note that such an operation is the same when decelerating when the switching valve 4 is switched to the human position shown in FIG. 1 and the hydraulic motor 1 is rotated in the opposite direction.

FIG. 4 shows the switching valve 4 in accordance with the operation of the switching valve 4 described above.
FIG. 3 is a diagram showing the relationship between the amount of movement of the spool 28 and the opening area of the first opening/closing section 29, the second opening/closing section 30, 31, and the third opening/closing section 32. Note that α on the horizontal axis in FIG. 4 indicates the amount of movement of the spool 28, and the amount of movement increases in the X direction in FIG. Further, β on the vertical axis indicates the opening area, and the opening area increases as the axis rotates in the X direction. Further, 35 indicates a characteristic line in the third opening/closing section 32, 36 indicates a characteristic line in the first opening/closing section 29, and 37 indicates a characteristic line in the second opening/closing section 30.31.

When trying to return the spool 28 to neutral in order to apply a brake to the hydraulic motor 1 in operation (when trying to move it in the opposite direction to the X direction), as shown by characteristic lines 35 and 36 in Fig. 4, , the opening area of the third opening/closing part 32 and the opening area of the first opening/closing part 29 decrease, and then, as shown by a characteristic line 37, the opening area of the second opening/closing part 30, 31 starts to increase. Note that, before the third opening/closing part 32 and the first opening/closing part 29 complete closing, the second opening/closing part 30.31 opens to a sufficiently large opening area. Moreover, the third opening/closing part 32 and the first opening/closing part 29 are configured to complete closing at the same time.

By the way, the conventional inertia r1f configured in this way,
In the f1Ji7 movable moon 1 hydraulic IJ path, as shown by characteristic lines 35 and 36 in FIG.
The conduit 12 and the conduit 13 are closed at the γ point where the opening area of 2 and the opening area of the first opening/closing part 29 become zero.
At that time, as shown by the characteristic line 37 in FIG. The pressure is the tank pressure. Therefore, when the pipe line 12 and the pipe line 13 are closed and the brake is applied to the hydraulic motor 1, the pressure in the pipe line 12 becomes the tank pressure.
Further, the pressure in the pipe line 13 at this time is the sum of the tank pressure and the set pressure of the relief valve 16. Note that when the circuit constituted by the hydraulic motor 1 and the pipes 12 and 13 is closed, the hydraulic motor 1♀;, cy) is generally functionally susceptible to oil leakage to the outside of the circuit. will inevitably occur. Therefore, the amount of oil in the circuit is insufficient, the amount of suction by the hydraulic motor 1 is insufficient, and if this state continues, cavitation will occur.

In the conventional hydraulic circuit described above, in order to prevent such cavitation, pipe lines 20, 2L22 and check valves 18, 19 are provided as shown in FIG.
Oil from tank 23 is passed through line 21.22 to check valve 18.
．． It is now possible to replenish through 19. In other words,
As mentioned above, when the oil in the pipe line 12 becomes insufficient and the pressure in the pipe line 12 becomes equal to or lower than the tank pressure, the insufficient oil amount is replaced by the check valve 18.
It is supplied to the conduit 12 via. However, in general, tank pressure can only be raised slightly above atmospheric pressure (
The pressure difference between the pipe line 12 and the tank pressure is large (not possible. For this reason, in the past, insufficient oil volume could not be replenished due to pressure loss of the check valve 18, etc.) However, there is a problem that it is not always possible to sufficiently prevent cavitation.

The present invention has been made in view of the actual situation in the prior art, and its purpose is to apply relief pressure of a hydraulic pump in a pipe connected to the actuator when decelerating the actuator that drives the inertial mass. It is an object of the present invention to provide a hydraulic circuit for driving an inertial mass that can be enclosed and does not require replenishment of oil.

In order to achieve this object, the present invention has a hydraulic pump driven by a prime mover, and a hydraulic excavator equipped with a hydraulic excavator that is operated by pressure oil supplied from the hydraulic pump and drives a large inertial mass. an actuator such as a motor, a tank connected to a hydraulic pump, and a first pipe interposed between the tank and the hydraulic pump that opens and closes the pipe connecting the hydraulic pump and the first port of the actuator.
a second opening/closing part for opening and closing a pipe connecting the hydraulic pump and the tank, and a second opening/closing part for the actuator.
a switching valve having a third opening/closing part for opening and closing a pipe connecting the boat and the tank; a means for setting a maximum pressure in the pipe between the switching valve and the actuator; a hydraulic pump and the switching valve; and a means for setting a maximum pressure in the pipeline between the two, wherein the switching valve described above closes the third opening/closing part with priority over the first opening/closing part when decelerating the actuator, or The third opening/closing part is given priority over the first opening/closing part to bring it into a nearly closed state where the opening area is sufficiently small, and after the closing operation of the third opening/closing part and the first opening/closing part is completed, or After the third opening/closing part and the first opening/closing part approximate closing operation, the second u1j closing part in the closed state or the nearly closed state is opened so as to expand the opening area. .

Hereinafter, a hydraulic circuit for driving an inertial mass according to the present invention will be explained based on the drawings.

FIG. 5 is a partial sectional view of a three-position 1h switching valve constituting a main part of an embodiment of the present invention, showing a neutral state. Note that the same parts as those shown in this figure and Figures 7(a) and 7(b), which will be described later, and Figure 8A2.3, which will be described later, are designated by the same reference numerals. The basic structure of the hydraulic circuit in which the switching valve shown in FIG. 5 is arranged is substantially the same as that of the hydraulic circuit shown in FIG. 1 described above. However, the same
The 1-pipes 20, 21 and 22 and check valves 1B and 19 shown in the figure are not necessary for the technology that is the object of the present invention, and are therefore excluded from illustration.

In FIG. 5, 40 is the main body of the switching valve 40, 41 is the spool, and 42 is the first opening/closing part 2 when switching the spool 41.
9. This is a reference line temporarily set to explain the opening/closing timing of the second opening/closing parts 30, 31 and the third opening/closing part 32. This reference line 42 is the reference line 42 when the spool 41 and It passes through the center of the main body 40.

In this embodiment, the main body 40 and spool 41 of the switching valve 4 are provided as described below.

For example, if the end surface 4 of the main body 4° constituting the third opening/closing part 32
3 and the reference line 42, and y□ is the distance between the end surface 44 of the spool 41 constituting the third opening/closing portion 32 and the reference line 42. In addition, the distance N# between the end surface 45 of the main body 4o constituting the first opening/closing part 29 and the reference line 42 is set to X2,
Let y2 be the distance between the end surface 46 of the spool 41 constituting the opening/closing part 29 and the reference line 42. Also, the second opening/closing section 30.
31-5, the distance between the end surface 47 of the main body 4o constituting the second opening/closing section 31 and the base 3ip line 42 is X3, and the distance between the end surface 48 of the spool 41 constituting the second opening/closing section 31 and the reference line 42
y3, the distance between the end surface 49 of the main body 40 constituting the second opening/closing section 3o and the reference line 42, X4, the distance between the end surface 50 of the spool 41 constituting the second opening/closing section 3o and the reference line 42 The distance ′f! Let it be 0'y4. End surfaces 44, 46, 5 of the spool 41 constituting each of the third opening/closing part 32, the first opening/closing part 29, and the second opening/closing part 30.31.
If the length of the outer circumference of 0.48 is all πd, the opening areas of the third opening/closing part 32, first opening/closing part 29, and second opening/closing part 30.31 are each 0'1 xl) π
d+ (x2-)'2)πdl O'4-X4)πd,
It is represented by (x3 ya)πd. Once these opening areas are linearly proportional to the distance traveled by the spool 41. For this reason, in this embodiment, the above x1 to X4 + Yl to y4 satisfy y2>X2 + Ya>Xa t Ys<Xa when Yt<Xt, and y1≧x1 When X2>yz and X2- Y
2>Yl−Xl and when x2≧y2, x4
>Y4 # ya>Xasuo, 1bi lX4-X<DIX
It is set so that s-yal>lX2-11 is satisfied.

These relationships are expressed as shown in FIG. Become. Note that α on the horizontal axis of FIG. 6 indicates the amount of movement of the spool 41, and β on the vertical axis indicates the opening area. Also, 51 is the third
Characteristic line 52 in the opening/closing part 32 of the first opening/closing part 29
A characteristic line 53 indicates a characteristic line at the second opening/closing portion 30.31.

As is clear from FIG. 6, in this embodiment, the main body 40 and spool 41 of the switching valve 4 constitute means for realizing the operations described below. That is,
During deceleration, the opening area of the third opening/closing part 32 becomes the first cr) opening/closing part 2, as shown by the characteristic %I51.52.
9, that is, the third opening/closing part 32 is closed with priority over the first opening/closing part 29, and the opening area of the third opening/closing part 32 and the first opening/closing part 29 is After the area becomes zero, that is, after the closing operation of the third opening/closing part 32 and the first opening/closing part 29 is completed, the second opening/closing is in the closed state where the opening area is zero as shown by the characteristic line 53. The sections 30 and 31 are opened to enlarge their opening areas.

Next, a hydraulic motor 1 of an embodiment configured as described above will be explained.
The action during deceleration will be explained based on FIGS. 7(a) and 7(b) and FIG. 1. In addition, Fig. 7(a)
, (b) is a partial cross-sectional view illustrating the operation of the switching valve 4.

1 attempts to switch the switching valve 4 from position B shown in FIG. 1 to the neutral position in order to apply a brake to the hydraulic motor 1 in operation.
- Then, first, as shown in FIG. 7(a), the third opening/closing section 32 becomes closed, and the pipe 2T communicating with the pipe j shown in FIG. When the pipe line 54 communicating with the tank communication pipe line 6 via the pipe line 25 is disconnected, the first opening/closing part 29 is in an open state, and therefore, the first opening/closing part 29 is in an open state, so that it is in communication with the pipe line 12 shown in FIG. The pipe line 26 connected to the pipe line 5 that communicates with the hydraulic pump 2 communicates with the pipe line 24 that is connected to the pipe line 5 that communicates with the hydraulic pump 2.The second opening/closing part 30.31 is in a closed state, so that the pipe line 24 and the pipe line 24 that is A conduit 55 communicating with the conduit 25
That is the purpose. As a result, the pressure of the hydraulic pump 2 is transmitted from the pipe 5 to the pipe 13 via the pipe 12 and the hydraulic motor 1, but since the third opening/closing part 32 is in the closed state, the pressure of the hydraulic pump 2 is The pressure increases to the relief pressure of the relief valve 10.

Then, when the spool 41 is moved 1, the first opening/closing part 29 is closed together with the second opening/closing part 30, 31 and the third opening/closing part 32, as shown in FIG. 7 (bJ). Therefore, the relief pressure of the hydraulic pump 2 is confined in the pipes 12 and 13 of both boats of the hydraulic motor 1.The brake pressure of the hydraulic motor 1 is determined by the pressure difference between the pipes 12 and 13, so the brake Pressure is ensured.

Furthermore, when the neutral state is reached, as shown in FIG. Thus, the pipe line 24 communicating with the pipe line 5 and the pipe line 55 communicating with the pipe line 25, that is, the tank communication pipe line 6, communicate with each other.

As described above, it is assumed that it will take a long time for the relief pressure of the hydraulic pump 2 trapped in both boats of the hydraulic motor 1 to decrease to the tank pressure due to rippling. If there is, there will be no shortage of oil, and there will be no need to replenish the oil.

The above-described operation is the same when the switching valve 4 is switched to the jA position shown in FIG. 1 and the platform is decelerated while the hydraulic motor 1 is rotated in the opposite direction.

FIGS. 8(a), (b), and (C) show the moving needle of the spool 41 of the switching valve 4, the first opening/closing part 29, and the second opening/closing part 30 for explaining another embodiment of the present invention. ,31,3rd
3 is a diagram showing the relationship between the opening area of the opening and closing portion 32 and the opening area of the opening/closing portion 32.

What is shown in FIG. 8(a) shows the characteristics (characteristic line 52° 53
) are set to be the same as the characteristics shown in FIG.
4, an opening area '1 small enough to confine the relief pressure of the hydraulic pump 2 in the line 12.13 shown in FIG.
A close approximation state is formed from -1. 56 shown in Figure (a) indicates a characteristic line in the third opening/closing section 32,
Further, 57 indicates a range in which the opening area changes due to the notch provided on the end surface 44 of the spool 41.

Moreover, what is shown in FIG. 8(b) shows the characteristics (characteristic line 52° 51
) is set to be the same as the characteristics shown in FIG.
The end faces 48, 50 of the holder are provided with notches similar to those described above,
Only the characteristics of this second opening/closing part 30,31 differ from the previous embodiment. In addition, 58 shown in FIG. 8(b) indicates the characteristic line in the second opening/closing part 30.31, and 59 indicates the opening area by the notch provided on the brocade 1 surface 48.50 of the spool 41. shows the range of change.

In addition, in the case shown in FIG. 8(C), the characteristics (fi' characteristic line 52) in the first opening/closing part 29 are set to be the same as the characteristics shown in FIG. Part 30.31
The characteristics in the third opening/closing portion 32 are set to be approximately the same as those shown in FIG.

In a hydraulic circuit equipped with a switching valve 4 having a spool and a main body having the characteristics shown in FIGS. 8(a), (b), and CC), when the hydraulic motor 1 is decelerated, the third The opening/closing part 32 or the second opening/closing part 30.31 can be brought into a nearly closed state sufficient to confine the relief pressure of the hydraulic pump 2 in the line 12.13. Similarly, there is no shortage of oil 77 during the braking operation of the hydraulic motor 1 (and no oil replenishment is required).

In addition, in the hydraulic circuit equipped with the switching valve 4 illustrated in FIGS. 8(a), (b), and (C), the third J
4→Since a notch is provided on the end face 44 of the spool 41 forming the closing part 32, or on the end face 48, 50 of the spool 41 forming the second opening/closing part 30. A smooth switching operation can be realized, and the impact during switching can be reduced.

Since the inertial ηht drive hydraulic circuit of the present invention is configured as described above, when decelerating the actuator that drives the inertial mass, the relief pressure of the hydraulic pump is applied to the pipe line connected to the actuator. Therefore, oil replenishment is not required, and therefore, the occurrence of gearvitation can be effectively prevented.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an example of a conventional inertial mass drive hydraulic circuit, and the second and third factors are explanatory diagrams showing the structure of a three-way switching valve provided in the hydraulic circuit shown in Fig. 1. Figure 2 is a cross-sectional view showing the neutral state, the third cause is a cross-sectional view showing the state switched to the B position, and Figure 4 is the three-position direct switching caused by the operation of the three-position neck switching valve shown in Figures 2 and 3. A diagram showing the relationship between the amount of movement of the valve spool and the opening area of the first opening/closing part, the second opening/closing part, and the third opening/closing part, and FIG. 5 is one of the inertial mass drive hydraulic circuits of the present invention. A partial cross-sectional view of a three-way switching valve that constitutes the main part of the embodiment,
FIG. 6 shows the amount of movement of the spool of the three-way direct switching valve shown in FIG.
A diagram showing the relationship between the opening/closing part and the opening area of the third opening/closing part,
Fig. 7(a), (b) Partial cross-sectional view illustrating the operation of the three-way switching valve shown in Fig. 5(b), Fig. 8(a), (b)
b) and (C) are the amount of movement of the spool of the three-way switching valve and the first opening/closing part, for explaining another embodiment of the present invention;
It is a figure which shows the opening area of a 2nd opening-and-closing part and a 3rd opening-and-closing part. 1...Hydraulic motor (actuator)・2°°
Group. Hydraulic pump, 3... Prime mover, 4... Three-position switching valve, 5.7, 9, 11, 12, 13, 15, 1
7, 24, 25, 26, 27° 31.54.55...
... Pipe line, 6... Tank connecting pipe line, 8,33
...Check valve, 10...Relief valve, 1
4.16...Differential pressure type relief valve, 23...
...Tank, 28...Sugur, 29...
...first opening/closing part, 30.31...second opening/closing part, 32...third opening/closing part, 40...main body,
41... Suguru, 43, 44, 45, 46,
47°48.49.50...End face. Figure 1 Figure 2 2.5 4 Figure 3 Figure 7 (a) (b) Figure 8

Claims (1)

[Claims] 1. A hydraulic pump driven by a prime mover, an actuator that is actuated by pressure oil supplied from this hydraulic pump and drives a large amount of inertia S, a tank connected to the hydraulic pump, and this tank and the above a first opening/closing part interposed between the hydraulic pump and the pipe connecting the hydraulic pump and the first boat of the actuator; and a pipe connecting the hydraulic pump and the tank. A switching valve having a second opening/closing part that opens and closes a passage, and a third opening/closing part that opens and closes a pipeline connecting a second port of the actuator and the tank, and a switching valve that connects the switching valve and the actuator. In an inertial mass drive hydraulic circuit comprising means for setting a maximum pressure in a pipe line between the hydraulic pump and the switching valve, and a means for setting a maximum pressure in a pipe line between the hydraulic pump and the switching valve, the switching valve When decelerating the actuator, the third opening/closing part is closed p14 L with priority over the first opening/closing part, or the opening area of the third opening/closing part is closed with priority over the first opening/closing part. After the third opening/closing section and the first opening/closing section have completed the closing operation, or after the third opening/closing section and the first opening/closing section have completed the closing operation, the closing operation is performed. A hydraulic circuit for driving an inertial mass, comprising means for opening the second opening/closing section which is in a state or an approximately closed state so as to enlarge the opening area.