JPH0777205A - Booster device - Google Patents

Abstract

PURPOSE:To provide a booster device capable of automatically obtaining boosted oil pressure when necessary, without resetting the rated pressure of a hydraulic system. CONSTITUTION:An operating valve 12 connected to a hydraulic pump 13 directional-controls pump-discharged pressure oil to control an opening and closing cylinder 4 for opening and closing a jaw of a breaker. A pilot type check valve 8 is interposed between expansion side oil passages 271, 272 between the operating valve 12 and the opening and closing cylinder 4. The checking action of the check valve 8 is released by pilot pressure guided from a contraction side oil passage 28 on the opposite side through a pilot oil passage 9. A sequence valve 7 is provided on an oil passage 26 branched from the expansion side oil passage 271 on the operating valve 12 side from the check valve 8. An electromagnetic change-over valve 6 is provided on a supply oil passage 29 supplied with pressure oil through the sequence valve 7. A double acting boosting cylinder 5 is connected to output oil passages 241, 242 of the electromagnetic change-over valve 6. The boosting cylinder 5 outputs boosted pressure oil to the expansion side oil passage 272 on the opening and closing cylinder 4 side from the check valve 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure increasing device applied to a hydraulic circuit for driving a hydraulic actuator (hydraulic cylinder, hydraulic motor) in, for example, a crusher, a press, a molding machine or a testing device.

[0002]

2. Description of the Related Art As shown in FIG. 3, the hydraulic circuit of a conventional crusher does not have a pressure increasing circuit, and the output oil passage of the operating valve 12 is an expansion oil passage 40 and a compression oil passage of the opening / closing cylinder 4. High-pressure oil, which is directly connected to each of the hydraulic pumps 41, is discharged from the hydraulic pump 13 and whose pressure is set by the safety valve (relief valve) 10, is alternately supplied to the open / close cylinder 4 by switching the operation valve 12 to perform the open / close operation.

[0003]

The closing operation of the crusher requires a strong force for crushing and cutting concrete lumps, reinforcing bars and the like. However, since the crushing force is determined by the hydraulic pressure, only the crushing force based on the rated pressure of the mother machine (for example, a hydraulic excavator) equipped with the crusher can be exerted in the conventional hydraulic circuit. And since the rated pressure of the mother machine is set to the optimum pressure of the hydraulic system of the mother machine, the pressure will be insufficient when strong oil pressure such as a crusher is required, and the capacity of the crusher will be maximized. There is a problem that it cannot be used.

A possible solution is to reset the rated pressure to a high pressure when the crusher is used.
This seriously affects the entire hydraulic system of the mother machine, and problems such as damage to the mother machine and shortening the life of the mother machine are likely to occur.

The present invention has been made in view of the above points, and it is possible to set the rated pressure of a hydraulic system without resetting the rated pressure.
An object of the present invention is to provide a pressure increasing device that can automatically obtain an increased hydraulic pressure when necessary.

[0006]

The invention described in claim 1 is to provide a hydraulic power source, an operation valve connected to the hydraulic pressure source, and a hydraulic actuator operated by pressure oil whose direction is controlled by the operation valve. In a hydraulic circuit including a pilot type check valve which is interposed in an oil passage on the side where at least a high pressure is required between the operation valve and the hydraulic actuator, and which is released by the pilot pressure from the oil passage on the opposite side. And a sequence valve provided in an oil passage branched from the oil passage on the operation valve side of the pilot type check valve, and a pressure booster circuit switching provided in a supply oil passage to which pressure oil is supplied via this sequence valve. And a pressure increasing cylinder connected to the output oil passage of the pressure increasing circuit switching valve and outputting the increased pressure oil from the pilot type check valve to the oil passage on the hydraulic actuator side. It was a pressure booster.

According to the second aspect of the invention, the hydraulic pump 13, the tank 36 and the safety valve 10 forming the hydraulic pressure source, the operation valve 12 connected to the hydraulic pressure source, and the direction control by the operation valve 12 are performed. In the hydraulic circuit provided with the opening / closing cylinder 4 operated by pressure oil, the pilot oil is supplied from the compression side oil passage 28 on the opposite side interposed between the expansion side oil passages 271 and 272 between the operation valve 12 and the opening / closing cylinder 4. The pilot type check valve 8 which is released by the pilot pressure through the passage 9 and the sequence valve 7 provided in the oil passage 26 branched from the expansion side oil passage 271 on the operation valve 12 side of the pilot type check valve 8. And an electromagnetic switching valve 6 provided in a supply oil passage 29 to which pressure oil is supplied via the sequence valve 7, and the pilot type check valve 8 connected to the output oil passages 241 and 242 of the electromagnetic switching valve 6.
And a double-acting pressure increasing cylinder 5 that outputs increased pressure oil to the expansion side oil passage 272 closer to the opening / closing cylinder 4 side, and the operation valve 12 has a structure of three positions and four ports, and is manually operated. Alternatively, the pressure oil from the hydraulic pump 13 is controlled by the pilot pressure and the expansion side oil chamber 20 of the opening / closing cylinder 4 is supplied via the expansion side oil passages 271 and 272.
To the compression-side oil chamber 21 of the opening / closing cylinder 4 and returning the return oil from the opening / closing cylinder 4 to the tank 36, and the pilot type check valve 8
Is inserted between the expansion-side oil passages 271 and 272 so that the free-flow direction of the expansion-side oil passage is toward the expansion-side oil chamber 20, and is non-returned by the oil pressure in the compression-side oil passage 28 via the pilot oil passage 9. Release control,
The sequence valve 7 has a branch oil passage 26 from the expansion side oil passage 271.
Is operated when the pressure in the branch oil passage 26 becomes equal to or higher than the set pressure, and the pressure oil from the operation valve 12 is output to the electromagnetic switching valve 6 via the supply oil passage 29. Is in position 4
The double-acting pressure increasing cylinder 5 has a port structure and pressure oil from the sequence valve 7 is output through the output oil passage 241 or 242.
The return oil from the double-acting pressure increasing cylinder 5 is guided to the compression-side oil passage 28 through the check valve 11, and the double-acting pressure increasing cylinder 5 has two large-diameter drive oil chambers 221, 222 and
It has two small-diameter pressure boosting oil chambers 231 and 232 and a pressure boosting piston 50 fitted to these, and one driving oil chamber 221 has one output oil passage 241 from the electromagnetic switching valve 6, The other output oil passage 242 from the electromagnetic switching valve 6 is guided to the other drive oil chamber 222, and one output oil passage 241 is used for inflow of oil to the one boosting oil chamber 231 for checking one inflow. The oil is introduced through the valve 161, and one of the check valves 151 and the boost oil passage 33 for outflow is used for the outflow of the oil from the boost oil chamber 231.
Oil to the expansion side oil passage 272 via the
The oil is introduced from the other output oil passage 242 through the other inflow check valve 162 for the inflow of oil into the other, and the other outflow check valve 152 for the outflow of the oil from the other booster oil chamber 232. Also, the oil is guided to the expansion side oil passage 272 via the pressure increasing oil passage 33, the movement of the pressure increasing piston 50 is detected near the stroke end of the pressure increasing piston 50, and the solenoid of the electromagnetic switching valve 6 is detected.
The pressure booster has a configuration in which proximity sensors 251a and 251b that send a switching excitation signal to the 253 are incorporated.

[0008]

According to the pressure booster of claim 1, when a high load is applied to the hydraulic actuator and the hydraulic pressure of the oil passage on the side requiring a high pressure rises, the sequence valve opens and the pressure booster circuit operates. The pressure booster cylinder reciprocates due to the pressure oil supplied via the switching valve, and the pressure oil boosted by the pressure booster cylinder is output from the pilot type check valve to the oil passage on the hydraulic actuator side, and the hydraulic actuator is driven from normal hydraulic pressure. Drive strongly.

In the pressure increasing device of the second aspect, the sequence valve 7 is not opened in the normal opening / closing operation because the operating pressure is low. In the extension operation, the pressure oil is the pilot type check valve 8 in the extension side oil passage.
Is opened and flows into the expansion side oil chamber 20 of the opening / closing cylinder 4, and the oil in the compression side oil chamber 21 returns to the tank 36 via the compression side oil passage 28. Further, in the compression operation, the pressure oil flows from the compression side oil passage 28 into the compression side oil chamber 21 and the pilot type check valve 8 is opened via the pilot oil passage 9, so that the oil in the expansion side oil chamber 20 is expanded. Return to the tank 36 via the pilot type check valve 8 on the road.

On the other hand, for example, when the crusher 3 sandwiches a lump of concrete or the like, the pressure in the expansion oil passage 271 becomes high, so that the sequence valve 7 opens and the high pressure oil flows into the supply oil passage 29. The inflowing high-pressure oil flows through the electromagnetic switching valve 6 into one drive oil chamber (pressure-receiving area A) of the double-acting pressure-increasing cylinder 5, and further through the check valve 161, the pressure-increasing oil chamber 231 (pressure-receiving area a). ) Flow into.

Then, the pressure-increasing piston 50 is driven to compress the oil in the pressure-increasing oil chamber 232 (pressure-receiving area b) on the opposite side, and the pressure is increased to a pressure-increasing area ratio (A + a) / b times. The booster oil chamber 232
The high pressure oil flows into the extension side oil chamber 20 of the opening / closing cylinder 4 via the check valve 152, and the thrust of the opening / closing cylinder 4 is increased to increase the crushing force. This high-pressure oil will not flow back due to the pilot-type check valve 8 in the expansion oil passage and the oil outflow check valve 151 from the pressure boosting cylinder 5.

When the booster piston 50 strokes near the stroke end, the proximity sensor 251a causes the booster piston 50 to move.
Is detected and a signal is output to the solenoid 253 of the electromagnetic switching valve 6 to perform switching, and the high pressure oil from the sequence valve 7 is transferred to the drive oil chamber 222 (pressure receiving area B ) And the pressure-increasing oil chamber 232 (pressure-receiving area b), the pressure-increasing piston 50 strokes in the opposite direction, increasing the pressure of the pressure-increasing oil chamber 231 in the stroke direction by a pressure-receiving area ratio (B + b) / a times. From the check valve 151 to the expansion side oil chamber 20 of the open / close cylinder 4.
Send to. Then, when the stroke end is approached, the electromagnetic switching valve 6 is switched, and the same movement as above is repeated.

Due to the above movement, the operating pressure on the expansion side of the opening / closing cylinder 4 is the ratio of the pressure receiving area of the pressure increasing cylinder 5 (A + a) /
The pressure becomes higher by b or (B + b) / a times, and the thrust (crushing force) of the opening / closing cylinder 4 also increases.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The pressure booster of FIG. 1 applied to the crusher of the hydraulic excavator shown in FIG. 2 will be described in detail below as an embodiment of the present invention.

In the figure, 1 is a hydraulic excavator as a mother machine, and 2 is its front working machine system. A crusher 3 is attached to the tip of the front working machine system 2 as an attachment. Reference numeral 4 denotes an opening / closing cylinder that opens and closes the claws of the crusher 3. Since the claws close to crush the object when the cylinder 4 is extended, a strong thrust force is required during the extension operation.

Reference numeral 13 denotes a hydraulic pump, and this hydraulic pump 13
The high pressure oil discharged from the open / close cylinder 4 passes through the extension side oil passages 271 and 272 by switching the operation valve 12 to the right side.
To the expansion side oil chamber 20 and to the compression side oil chamber 21 of the opening / closing cylinder 4 via the compression side oil passage 28 by switching to the left side.

A safety valve 10 is installed between the output side of the hydraulic pump 13 and the return oil passage to the tank 36 for setting the circuit pressure. Also, to prevent overloading of the open / close cylinder 4, a safety valve 14
Between the contraction side oil chamber 21 and the expansion side oil chamber 20.

Numeral 8 is a pilot type check valve which is inserted between the expansion side oil passage 271 and the expansion side oil passage 272 so that the free flow direction is toward the expansion side oil chamber 20. The check release pilot oil passage 9 is guided to the compression side oil passage 28.

A sequence valve 7 is connected to the branch oil passage 26 from the expansion oil passage 271 and guides the pressure oil to the electromagnetic switching valve 6 through the supply oil passage 29 as the output oil passage.

Reference numeral 6 is an electromagnetic switching valve, which switches the supply oil passage 29 from the sequence valve 7 to the output oil passage 241 or the output oil passage 242.

Reference numeral 5 denotes a double-acting pressure increasing cylinder, which has two large diameter drive oil chambers 221 and 222 and two small diameter pressure increasing oil chambers 231.
, 232 and booster piston 5 slidably fitted to these
It consists of 0 and. The booster piston 50 includes drive oil chambers 221 and 222.
On both sides of the large-diameter piston slidably fitted to
231 and 232 are slidably fitted together to form a small piston with a small pressure receiving area.

An output oil passage 241 from the electromagnetic switching valve 6 is led to the driving oil chamber 221, and an output oil passage 242 from the electromagnetic switching valve 6 is led to the driving oil chamber 222. The oil is guided from the output oil passage 241 through the inflow check valve 161 to the pressure-increasing oil chamber 231 through the inflow check valve 161, and the outflow check valve 151 and the pressure-increasing pressure are supplied to the oil from the pressure-increasing oil chamber 231. Oil is guided to the extension side oil passage 272 via the oil passage 33.

Similarly, oil is introduced into the booster oil chamber 232 from the output oil passage 242 through the check valve 162 for inflow for inflow of oil, and is checked for outflow for outflow of oil from the booster oil chamber 232. Oil is guided to the extension side oil passage 272 via the valve 152 and the pressure boosting oil passage 33. Reference numeral 31 denotes a tank oil passage, which guides the return oil of the electromagnetic switching valve 6 to the compression side oil passage 28 via the check valve 11.

Proximity sensors 251a and 251b are pressure increasing pistons.
It detects when 50 reaches near the stroke end on the right side or the left side. It is a pressure increasing oil chamber 23 of the double acting pressure increasing cylinder 5.
Install at the ends of 1 and 232. Drive oil chambers 221 and 22
It may be the end of 2. The outputs of these two sensors are the outputs of the proximity sensor 251a to excite and latch the solenoid 253 of the electromagnetic switching valve 6. The output of the proximity sensor 251b is used as a signal for releasing the excitation of the solenoid 253 of the electromagnetic switching valve 6, and when the excitation is turned off, the electromagnetic switching valve 6 is switched by a spring as shown in FIG.

Next, the operation of the crusher pressure increasing device configured as described above will be described below.

In a normal opening / closing operation, since the operating pressure is low, the sequence valve does not open. That is, extension operation (operation valve 12
At the right position of the), the hydraulic fluid discharged from the hydraulic pump 13 opens the pilot type check valve 8 to the expansion side oil passage 272, flows into the expansion side oil chamber 20 of the opening / closing cylinder 4, extends the opening / closing cylinder 4, and crushes the crusher. Close the 3rd nail. At that time, the compression side oil chamber 21
Oil returns to the tank 36 through the compression side oil passage 28 and the operation valve 12.

Further, in the case of the contraction operation (the position on the left side of the operation valve 12), the pressure oil discharged from the hydraulic pump 13 flows into the contraction side oil chamber 21 of the opening / closing cylinder 4 through the contraction side oil passage 28, and the opening / closing cylinder 4 is opened. Shrink 4 and open the claw of crusher 3. At that time, the oil in the expansion side oil chamber 20 is formed by the expansion side oil passage 272, the pilot type check valve 8 opened by the pilot oil passage 9, the expansion side oil passage 271 and the operation valve 12.
Return to tank 36 via.

On the other hand, for example, when the claws of the crusher 3 grasp and crush a crushed material such as a concrete lump, the expansion side oil chamber 20 and the expansion side oil passages 271 and 272 are at high pressure. When the oil pressure in the expansion oil passage 271 becomes higher than the set pressure of the sequence valve 7, the sequence valve 7 opens and high-pressure oil flows from the branch oil passage 26 into the supply oil passage 29, so that the pressure increasing circuit operates.

First, the solenoid 253 of the electromagnetic switching valve 6 is turned on (the switching valve is on the right side position).

When the pressure boosting piston 50 of the double-acting pressure boosting cylinder 5 moves to the left and approaches the left end, the proximity sensor 251b is turned on and the solenoid 253 of the electromagnetic switching valve 6 is turned off, which is not shown. In the state in which the latch such as the latch relay is released, the electromagnetic switching valve 6 is pressed to the right by the spring as shown in FIG.

Therefore, the electromagnetic switching valve 6 is switched to the left position and held at that position. Therefore, the oil supply passage 29
The high-pressure oil that has flown into flows into the drive oil chamber 221 (defined as the pressure receiving area A) of the double-acting pressure increasing cylinder 5 via the electromagnetic switching valve 6 and the output oil passage 241, and further opens the check valve 161 to open it. It flows into the booster oil chamber 231 (referred to as the pressure receiving area a).

Then, the pressure boosting piston 50 moves to the right in FIG. 1, and the oil in the drive oil chamber 222 (referred to as the pressure receiving area B) is passed through the output oil passage 242, the electromagnetic switching valve 6, and the check valve 11 to reduce the oil on the compression side. Road 28
The pressure boosting oil chamber 232 (pressure receiving area b)
Oil is compressed to increase the pressure-receiving area ratio, that is, (A + a) / b times, the check valve 152 is opened, and the pressure-increasing oil passage 33 is pushed out to the expansion-side oil passage 272, and the expansion-side oil chamber of the opening / closing cylinder 4 The pressure of 20 is increased to increase the thrust of the open / close cylinder 4 (crushing force of the claw).

Although the pressure in the expansion side oil passage 272 is higher than the pressure in the expansion side oil passage 271, it does not flow backward due to the action of the pilot type check valve 8. Also, due to the function of the check valve 151, there is no wraparound to the pressure-increasing oil chamber 231 on the opposite side.

When the booster piston 50 works to the right and approaches the stroke end, the proximity sensor 251a causes the booster piston 50 to move.
Is detected, the latch relay is turned on, and the solenoid 253 of the electromagnetic switching valve 6 is excited. Then, the solenoid operated directional control valve 6 is switched to the state of the right side position and held in that state.

At that time, the oil supply passage through the sequence valve 7
The high pressure oil 29 flows into the drive oil chamber 222 (pressure receiving area B) and the pressure increasing oil chamber 232 (pressure receiving area b) on the opposite side of the double-acting pressure increasing cylinder 5, and moves the pressure increasing piston 50 leftward. . The booster piston 50 discharges the oil in the drive oil chamber 221 to the tank oil passage 31 via the output oil passage 241 and the electromagnetic switching valve 6, and further the booster oil chamber
231 oil is compressed and the pressure receiving area ratio, that is, (B + b) / a
Double the pressure, open the check valve 151, push out to the expansion side oil passage 272 via the pressure increase oil passage 33, increase the pressure in the expansion side oil chamber 20 of the open / close cylinder 4, and increase the cylinder thrust, that is, the claw crushing force. Let

When the pressure boosting piston 50 approaches the left stroke end, the proximity sensor 251b detects the pressure boosting piston 50 and turns off the latched relay. At that time, the position of the electromagnetic switching valve 6 also returns to the state shown in FIG. 1 by the spring.

In the case of the contraction operation, the pressure does not flow backward due to the function of the check valve 11, and the pressure oil in the compression side oil passage 28 is changed by the electromagnetic switching valve 6.
Is not supplied to the booster circuit, so the booster circuit does not work.

With such an operation, when the expansion side oil passage 272 becomes higher than the set pressure of the sequence valve 7, the pressure increasing circuit operates, and the operation pressure on the expansion side of the opening / closing cylinder 4 is increased.
The pressure-increasing area ratio (A + a) / b or (B + b) / a is increased to a high pressure, and the pressure increasing operation is continuously repeated to increase the thrust of the opening / closing cylinder 4, and thus the crushing force.

In the embodiment, the case of the crusher in the hydraulic excavator has been described, but such a pressure booster drives a hydraulic cylinder, a hydraulic motor, etc. used in a press, an injection molding machine, a test apparatus or the like. It can be used even when high pressure is partially required in the hydraulic circuit.

[0040]

According to the invention as set forth in claim 1, a pressure increasing circuit constituted by a pressure increasing circuit switching valve and a pressure increasing cylinder is provided in front of the sequence valve branched from the operation valve side from the pilot type check valve. Since the boosted output is returned to the hydraulic actuator side from the pilot check valve, the hydraulic pressure automatically boosted at high load is obtained without resetting the rated pressure of the hydraulic system. be able to.

According to the invention described in claim 2, it is possible to provide a pressure increasing device suitable for the opening and closing cylinder for opening and closing the blade of the crusher, and when the crushing force is required, a pressure higher than the rated pressure of the mother machine is provided. Since it can be continuously discharged, the crushing power can be greatly increased, and the crusher's capacity can be utilized to the maximum. Also, since the pressure is increased only in the piping on the opening / closing cylinder side of the pilot type check valve and the output piping of the pressure boosting cylinder, it does not affect the other hydraulic system of the mother machine and can be modified to high pressure. The effect that it can be easily and cheaply produced.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a pressure booster of the present invention.

FIG. 2 is a diagram in which a crusher is attached to a hydraulic excavator.

FIG. 3 is a hydraulic circuit diagram showing a conventional hydraulic circuit for a crusher.

[Explanation of symbols]

 1 Hydraulic excavator 2 Front working machine system 3 Crusher 4 Opening / closing cylinder 5 Double-acting pressure increasing cylinder 6 Electromagnetic switching valve 7 Sequence valve 8 Pilot type check valve 9 Pilot oil passage 10 Safety valve 11 Check valve 12 Operation valve 13 Hydraulic pump 14 Safety valve 20 Expansion side oil chamber 21 Compression side oil chamber 26 Branching oil passage 28 Compression side oil passage 29 Supply oil passage 31 Tank oil passage 33 Pressure boosting oil passage 36 Tank 50 Pressure boosting piston 151, 152 Check valve 161, 162 Check valve 221, 222 Drive oil chamber 231,232 Pressure boosting oil chamber 241,242 Output oil passage 251a, 251b Proximity sensor 253 Solenoid 271, 272 Extension side oil passage

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Manabu Tamura 2-5-1, Marunouchi, Chiyoda-ku, Tokyo Sanryo Heavy Industries Co., Ltd.

Claims (2)

[Claims] 1. A hydraulic circuit comprising a hydraulic pressure source, an operation valve connected to the hydraulic pressure source, and a hydraulic actuator operated by pressure oil whose direction is controlled by the operation valve, wherein the operation valve and the hydraulic actuator are provided. And a pilot-type check valve that is interposed in an oil passage on the side requiring at least a high pressure and is released by the pilot pressure from the oil passage on the opposite side, and an oil passage on the operating valve side of this pilot-type check valve. To the sequence valve provided in the oil passage branched from the, the pressure increasing circuit switching valve provided in the supply oil passage to which the pressure oil is supplied via this sequence valve, and the output oil passage of this pressure increasing circuit switching valve. And a pressure boosting cylinder that outputs pressure oil that has been boosted to an oil passage on the hydraulic actuator side from the pilot check valve. 2. A hydraulic pump 13 and a tank forming a hydraulic source.
36 and the safety valve 10 and the operating valve 12 connected to this hydraulic source
And an opening / closing cylinder 4 operated by pressure oil whose direction is controlled by the operation valve 12, an extension side oil passage 271 between the operation valve 12 and the opening / closing cylinder 4,
Pilot type check valve 8 which is interposed by 272 and which is released from the opposite side compression side oil passage 28 through pilot oil passage 9 by the pilot pressure and the expansion side oil passage on the operation valve 12 side from this pilot type check valve 8. A sequence valve 7 provided in an oil passage 26 branched from 271 and an electromagnetic switching valve 6 provided in a supply oil passage 29 to which pressure oil is supplied via the sequence valve 7.
And a double-acting pressure increasing cylinder which is connected to the output oil passages 241 and 242 of the electromagnetic switching valve 6 and outputs the increased pressure oil from the pilot type check valve 8 to the expansion side oil passage 272 on the opening / closing cylinder 4 side. 5, the operation valve 12 has a three-position, four-port structure, is controlled by manual or pilot pressure, and opens and closes the pressure oil from the hydraulic pump 13 through the expansion side oil passages 271 and 272. 4 to the expansion side oil chamber 20 or via the contraction side oil passage 28
The return oil from the opening / closing cylinder 4 is returned to the tank 36, and the pilot type check valve 8 is configured so that the free flow direction of the expansion side oil passage is the expansion side oil chamber 20 direction. On the extension side oil passages 271, 272
The check valve is controlled by the hydraulic pressure of the compression-side oil passage 28 via the pilot oil passage 9, and the sequence valve 7 is provided with a branch oil passage 26 from the extension-side oil passage 271.
Is operated when the pressure in the branch oil passage 26 becomes equal to or higher than a set pressure, and the pressure oil from the operation valve 12 is output to the electromagnetic switching valve 6 via the supply oil passage 29. Has a two-position four-port structure and outputs the pressure oil from the sequence valve 7 to the output oil passage 241 or 242.
Is output to the double-acting pressure increasing cylinder 5 via the check valve 11, and the return oil from the double-acting pressure increasing cylinder 5 is guided to the compression side oil passage 28 via the check valve 11. Two large drive oil chambers 22
1, 222, two small-diameter pressure-increasing oil chambers 231, 232, and a pressure-increasing piston 50 fitted to these, and one driving oil chamber 221 has one output from the electromagnetic switching valve 6. Oil passage 241
The other output oil passage 242 from the electromagnetic switching valve 6 is introduced to the other drive oil chamber 222, and one output oil passage 241 is used as an oil inflow to the one pressure-increasing oil chamber 231. valve
161 to guide the oil, and to guide the oil from one of the booster oil chambers 231 to the outflow side oil passage 272 via the one outflow check valve 151 and the booster oil passage 33, and the other. Of the other output oil passage 242 for the inflow of oil into the booster oil chamber 232 of
Oil is introduced from the other side through the other inflow check valve 162, and for the outflow of oil from the other pressure boosting oil chamber 232, the other outflow check valve 152 and the pressure increase oil passage 33 are used to extend the expansion side oil passage. Guide the oil to 272, detect the movement of booster piston 50 near the stroke end of booster piston 50, and detect electromagnetic switching valve 6
Proximity sensor 251 that sends a switching excitation signal to the solenoid 253 of
A pressure booster characterized by incorporating a and 251b.