JP2000271878A - Stroke adjustment device for hydraulic stroke device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust a stroke according to the change in a state of each stroke by providing a thruster pushing a rod frontward between a stroke device body and the rod and providing a stroke control mechanism changing the stroke of a piston according to the front/rear displacement of the thruster. SOLUTION: Where bedrock is soft, the speed of a rod entering into the bedrock is high, and a breaker body cannot follow the forwarding movement of the rod, a thruster 12 pushes the rod frontward to closely stick it to the bedrock. Then, with the forwarding of the thruster 12, the communication between an operation port 18 and a return port 19 are interfered so that pressure oil is leaked from a high-pressure thrust chamber 20 to the operation port 18. The pressure oil gradually actuates a stroke control valve 42 to an open side via an operation circuit 17. As a result, a short stroke port 27 and a valve control chamber 75 are communicated with each other via a stroke control circuit 13 so that the control valve chamber 75 becomes high pressure to retreat a valve element 74 of a control valve 70. This constitution can shorten the stroke of a piston 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stroke adjusting device for a hydraulic striker such as a hydraulic breaker and a hydraulic rock drill.

[0002]

2. Description of the Related Art When crushing an object to be crushed, such as rock, using a hydraulic breaker, when crushing soft rock, the stroke of a piston is shortened so as to apply a large number of weak impacts, and when crushing hard rock, a strong impact is applied. It is desirable to lengthen the stroke of the piston in order to add

Conventionally, in a hydraulic breaker, there is known a stroke adjusting device capable of adjusting a stroke of a reciprocating motion of a piston by manual operation of an operator according to the rock quality of a bedrock. Hydraulic breakers provided with such a stroke adjusting device include those shown in FIGS. 6 and 7, for example. In this hydraulic breaker 100, a front chamber 3 and a rear chamber 4 are formed by slidingly fitting a piston 1 having a large diameter portion 1B at the center and small diameter portions 1A and 1C before and after the large diameter portion 1B into a cylinder 2 of a breaker body 101. 2 is provided with a front chamber high pressure port 26 for communicating the front chamber 3 to the high pressure circuit 5 and a rear chamber port 29 for communicating the rear chamber 4 to the control valve 70. Also, piston 1
Valve control port 2 at a position where it communicates with front chamber 4 when
4, a drain port 25 communicating with the low-pressure circuit 8 behind the valve control port 24, and a short stroke port 27 ahead of the valve control port 24.

On the outer periphery of the large diameter portion 1B of the piston 1, there is provided a communication groove 30 for communicating the valve control port 24 and the drain port 25 just before the striking position when the piston 1 advances. The control valve 70 has a valve plug 72 fitted in a valve housing 71, and its outer periphery and the valve housing 7.
A valve chamber 73 is formed between the valve chamber 73 and the inner circumference. A cylindrical valve element 74 is slidably fitted in the valve chamber 73.
3 includes a valve control chamber 75 for switching the valve element 74 forward and backward.
And a valve regulating chamber 76 that communicates with the high-pressure circuit 5 and urges the valve body 74 forward. The front end and the rear end of the valve chamber 73 are always in communication with the low-pressure circuit 8. The valve body 74 has a liquid supply hole 7 for communicating the rear chamber 4 with the high-pressure circuit 5 when the vehicle is moving backward.
7 and a drainage hole 78 for communicating the rear chamber 4 with the low-pressure circuit 8 during forward movement.

The valve control port 24 is connected to a valve control chamber 75 by a valve control circuit 31. The short stroke port 27 is connected to the valve control circuit 31 and the high-pressure circuit 5 through a stroke switching valve 32 so as to be able to switch and communicate therewith. The stroke switching valve 32 is a pilot operation switching valve, and its pilot port 33 is connected to the high pressure circuit 5 and the low pressure circuit 8 via a manually operated valve 34.

The operator can select the length of the stroke according to the properties of the object to be crushed and the contents of the work by switching the manual operation valve 34. Breaker body 10
1, a rod 22 is inserted in front of the piston 1. When the rock 102 is crushed,
An appropriate thrust is applied to the breaker main body 101 so that the breaker comes into close contact with the bedrock 102. In this state, a forward thrust is applied to the rear end of the rod 22 via a thrust bush 103 fixed to the breaker main body 101, and a strike is applied by the piston 1.

In the hydraulic breaker 100, when the short stroke port 27 and the high-pressure circuit 5 are communicated as shown in FIG. 7, when the valve body 74 of the control valve 70 is at the rear, the rear chamber 4 supplies the liquid. Since it communicates with the high voltage circuit 5 through the hole 77, the rear chamber 4 and the front chamber 3 are both at high pressure. Since the pressure receiving area on the rear chamber 4 side of the piston 1 is larger than the pressure receiving area on the front chamber 3 side, the piston 1 moves forward.
In this state, the valve control port 24 is open to the front chamber 3 side, and the drain port 25 is closed by the large-diameter portion 1B of the piston 1, so that the valve control port 24 communicates with the front chamber 3 via the valve control circuit 31. The pressure in the valve control chamber 75 is high. Therefore, both the valve control chamber 76 and the valve control chamber 75 are at a high pressure, and the pressure receiving area on the valve control chamber 75 side is larger than the pressure receiving area on the valve control chamber 76 side. Is held in.

When the piston 1 moves forward, the valve control port 24 is closed at the large diameter portion 1B of the piston 1, and the valve control port 24 and the drain port 25 communicate with each other through the communication groove 30 shortly before the hitting position. Valve control circuit 31, valve control room 75
Becomes low pressure. At this time, since the valve regulating chamber 76 remains at a high pressure, the valve element 74 of the control valve 7 moves forward. Control valve 70
When the valve body 74 moves forward, the liquid supply hole 77 closes and the liquid discharge hole 78 opens, and the rear chamber 4 communicates with the low-pressure circuit 8.

Here, if the rod 22 is pressed against the bedrock 102 and is at a predetermined striking position as shown in FIG. 6, the piston 1 strikes the rod 22, stops moving forward, and starts moving backward. When the piston 1 moves backward and the front chamber 3 communicates with the valve control port 24, the pressure in the valve control chamber 75 becomes high, and the valve body 74 of the control valve 70 moves backward. Here, the rear chamber 4 communicates with the high-pressure circuit 5 to have a high pressure, and the piston 1 that intends to keep moving backward due to inertia is braked, and the kinetic energy of the backward movement is accumulated in an accumulator (not shown) in the form of high-pressure oil. . The piston 1 that has stopped moving backward enters the forward travel again, and the same cycle is repeated thereafter.

When the short stroke port 27 and the valve control circuit 31 are in communication, the valve element 74 of the control valve 70
Is in the rear, the rear chamber 4 is in communication with the high-pressure circuit 5 through the liquid supply hole 77, so that both the rear chamber 4 and the front chamber 3 are at high pressure. Since the pressure receiving area on the rear chamber 4 side of the piston 1 is larger than the pressure receiving area on the front chamber 3 side, the piston 1 moves forward.

When the piston 1 moves forward, the valve control port 24 and the short stroke port 27 are closed by the large diameter portion 1B of the piston 1, and the valve control port 24 and the drain port 25 are connected to each other shortly before the striking position. Since the communication is performed at 30, the valve control circuit 31 and the valve control chamber 75 have a low pressure. At this time, since the valve regulating chamber 76 remains at a high pressure, the control valve 7
Of the valve element 74 moves forward. When the valve element 74 of the control valve 70 moves forward, the liquid supply hole 77 closes and the liquid discharge hole 78 opens, and the rear chamber 4 communicates with the low pressure circuit 8.

Here, if the rod 22 is pressed against the bedrock 102 and is at a predetermined striking position as shown in FIG. 6, the piston 1 strikes the rod 22, stops moving forward, and starts moving backward. When the piston 1 moves backward and the front chamber 3 and the short stroke port 27 communicate with each other, the pressure in the valve control chamber 75 becomes high, and the valve body 74 of the control valve 70 moves backward. Here, the rear chamber 4 communicates with the high-pressure circuit 5 to have a high pressure,
The piston 1 stops reversing and enters the forward traveling again. In this way, the timing of entering the previous progress is earlier,
The stroke of the piston 1 is shortened.

[0013]

Such a manually operated stroke adjuster of a hydraulic breaker can cope with an average rock condition, but cannot cope with an instantaneous change of the rock mass. When the rod is hit, the stagnation time of the piston in contact with the rear end of the rod depends on the nature of the object to be crushed. Therefore, a stroke adjusting mechanism of a hydraulic breaker has been proposed in which the stagnation time is detected by an amount of oil flowing through a piston and a hydraulic passage provided around the piston, and the piston stroke is changed based on the detected data. I have.

Although this stroke adjusting mechanism is intended to cope with a change in rock quality every hit, it cannot cope with a change in a contact state between the rod and the rock at the next hit. For example, when striking hard rock that shows strong rebound, the piston stroke is automatically set to be long,
Make the next blow powerful. If an appropriate thrust is given, the rock, the rod and the breaker body are in contact with each other at the time of impact, and there is no problem because the rod does not play.
If a disturbance occurs such as a decrease in the thrust given to the breaker before the next impact is applied, the rod and the bedrock lose contact. In this state, if a strong impact is applied to the rod as it is, the rod is hit without hitting, the harmful tensile stress generated in the rod increases, and the durability of the rod and the breaker body decreases.

Further, when the rock is soft, the breaker body cannot follow the forward movement of the rod due to the impact,
The contact between the rock and the rod and the breaker body may not be ensured during the next hit. The present invention relates to a stroke adjusting device for a hydraulic striking device capable of always keeping a rod in close contact with an object to be crushed and adjusting a stroke in response to a change in conditions such as the properties of the object to be crushed and thrust for each impact. The purpose is to provide.

[0016]

SUMMARY OF THE INVENTION According to the present invention, there is provided a hydraulic striking device in which a rod is inserted into a striking device body having a striking mechanism for reciprocating a piston back and forth by hydraulic pressure. The above problem is solved by providing a thruster that pushes the rod forward between them and providing a stroke control mechanism that changes the stroke of the piston by displacement of the thruster in the front-rear direction.

In this hydraulic hitting apparatus, when the object to be crushed is hard and the thrust is appropriately given, the rod is in close contact with the object to be crushed and the thruster is located at the rear end position, so that the stroke is lengthened and strong. Make a blow. In the case where the thrust is insufficient or the object to be crushed is soft and the striking device main body cannot follow the forward movement of the rod, the thruster pushes the rod forward to make it close to the object to be crushed. Then, the stroke control mechanism detects the forward displacement of the thruster at this time and changes the stroke of the piston so as to shorten the stroke of the piston, thereby performing control to reduce the impact applied to the rod.

Therefore, the stroke adjusting device of the hydraulic striking device can adjust so as to realize a stroke according to the condition of the crushing object while always keeping the rod in close contact with the object to be crushed. A control valve for connecting the rear chamber of the piston to a high-pressure circuit and a low-pressure circuit, and a valve control circuit for connecting a valve control port that is opened and closed by forward and backward movement of the piston to a valve control chamber for switching the control valve. A stroke control circuit for connecting a short stroke port provided in front of the valve control port to the valve control chamber, wherein the stroke control mechanism opens and closes the stroke control circuit, and moves the stroke control valve to the open side. An operation port connected to the operation chamber to be operated by an operation circuit, a return port connected to the low-pressure circuit, and a communication passage provided on the circumference of the thruster so that the operation port communicates with the return port when the thruster is in the rear position. And a clearance around the thruster for causing a hydraulic fluid in the thruster's propulsion chamber to leak to the working port by forward displacement of the thruster. Stroke adjusting device apparatus, the control of the detection and the stroke of the displacement of the thruster can be performed automatically by a hydraulic.

A stroke control mechanism includes a stroke control valve for opening and closing the stroke control circuit, a displacement detection piston provided behind the thruster, and an operation circuit connected to an operation chamber for operating the stroke control valve to the open side. A return port connected to the low pressure circuit, a communication passage provided on the circumference of the displacement detection piston so as to connect the operation port and the return port when the thruster is at the rear position, and a high pressure generated by the forward displacement of the thruster. The stroke adjusting device of the hydraulic hitting device, which has a clearance around the displacement detection piston that leaks the hydraulic fluid of the circuit to the working port, makes it easy to adjust the clearance around the displacement detection piston, the thruster diameter is large, and the hydraulic fluid leaks. This is effective when controlling the volume is difficult.

[0020]

FIG. 1 is a longitudinal sectional view of a hydraulic breaker provided with a stroke adjusting device according to an embodiment of the present invention, FIG. 2 is a circuit diagram of the hydraulic breaker, and FIG. 3 is an explanatory diagram of a stroke control mechanism. It is. Here, the hydraulic breaker 10
The piston 1 is reciprocally slidably fitted in the cylinder 2 of the breaker body 11 in the front-rear direction. A control valve 70 and a stroke control valve 42 are provided above the cylinder 2. A rod 22 is inserted in front of the piston 1 of the breaker body 11, and a thruster 12 for pushing the rod 22 forward is provided between the breaker body 11 and the rod 22.

The thruster 12 has a stepped outer periphery, and a propulsion chamber 20 is formed between the thruster 12 and the breaker body 11. The propulsion chamber 20 communicates with the high-pressure circuit 5. The pressure receiving area of the propulsion chamber 20 is set so that the thrust given to the rod 22 by the thruster 12 is slightly smaller than the thrust always given to the breaker body 11 during the crushing operation. The piston 1 has a large diameter portion 1B in the center and a small diameter portion 1B in front of the large diameter portion 1B.
A, has a small diameter portion 1C at the rear, and the front chamber 3 and the rear chamber 4 are formed by the difference in diameter. The rear small-diameter portion 1C has a smaller diameter than the front small-diameter portion 1A, so that the piston 1 has a larger pressure receiving area on the rear chamber 4 side than on the front chamber 3 side. The cylinder 2 is provided with a front chamber high pressure port 26 for communicating the front chamber 3 with the high pressure circuit 5 and a rear chamber port 29 for communicating the rear chamber 4 with a control valve 70. Further, a valve control port 24 is provided at a position communicating with the front chamber 4 when the piston 1 moves backward, and a drain port 25 communicating with the low-pressure circuit 8 behind the valve control port 24 and a valve control port 24 in front of the valve control port 24. A short stroke port 27 is provided.

On the outer periphery of the large diameter portion 1B of the piston 1, there is provided a communication groove 30 for communicating the valve control port 24 and the drain port 25 just before the striking position when the piston 1 advances. The control valve 70 has a valve plug 72 fitted in a valve housing 71, and forms a valve chamber 73 between the outer periphery and the inner periphery of the valve housing 71. A cylindrical valve element 74 is slidably fitted in the valve chamber 73,
The valve chamber 73 is provided with a valve control chamber 75 for switching the valve element 74 forward and backward, and a valve regulating chamber 76 for communicating with the high-pressure circuit 5 and urging the valve element 74 forward. The part and the rear end are always in communication with the low voltage circuit 8. The valve body 74 has a liquid supply hole 7 for communicating the rear chamber 4 with the high-pressure circuit 5 when the vehicle is moving backward.
7 and a drainage hole 78 for communicating the rear chamber 4 with the low-pressure circuit 8 during forward movement.

The valve control port 24 is connected to a valve control chamber 75 by a valve control circuit 31. The short stroke port 27 is connected to the valve control chamber 75 by the stroke control circuit 13.
In the middle of the stroke control circuit 13, a stroke control valve 42 of the stroke control mechanism 14 is connected.
Is provided. The stroke control valve 42 is normally closed by a spring 46. This stroke control valve 42
An operating port 18 connected to an operating chamber 45 for operating the valve to the open side by an operating circuit 17 and a return port 19 connected to the low-pressure circuit 8 are disposed in front of the propulsion chamber 20 of the thruster 12.

On the periphery of the thruster 12, there is provided a communication passage 21 for communicating the operation port 18 and the return port 19 when the thruster 12 is at the rear position. Operating circuit 17
Is provided with a sensitivity adjustment valve 47 in the middle of the process. The working chamber 45 is connected to the low pressure circuit 8 via a sensitivity adjusting valve 48. The amount of pressure oil supplied to the working chamber 45 can be adjusted by adjusting the openings of the sensitivity adjusting valves 47 and 48. The clearance 1 around the thruster 12
5, the seal length S between the cylinder 2 and the clearance 15 is reduced by the forward displacement of the thruster 12, and the pressure oil in the propulsion chamber 20 leaks to the working port 18.

In the hydraulic breaker 10, when the valve body 74 of the control valve 70 is at the rear, the rear chamber 4 is in communication with the high-pressure circuit 5 through the liquid supply hole 77, so that the rear chamber 4 and the front chamber 3 Are both high pressure. Since the pressure receiving area on the rear chamber 4 side of the piston 1 is larger than the pressure receiving area on the front chamber 3 side, the piston 1 moves forward. In this state, the valve control port 24
Is opened to the front chamber 3 side, and the drain port 25 is closed by the large diameter portion 1B of the piston 1, so that the valve control circuit 31
The pressure in the valve control chamber 75, which is in communication with the front chamber 3 via the air, is high. Therefore, both the valve control chamber 76 and the valve control chamber 75 are at high pressure, and the pressure receiving area on the valve control chamber 75 side is
6 is larger than the pressure receiving area of the switching valve 70,
4 is held rearward.

When the piston 1 moves forward, the valve control port 24 is closed at the large diameter portion 1B of the piston 1, and the valve control port 24 and the drainage port 25 communicate with each other through the communication groove 30 shortly before the hitting position. Valve control circuit 31, valve control room 75
Becomes low pressure. At this time, the valve regulating chamber 76 remains at a high pressure, so that the valve element 74 of the control valve 70 moves forward. Control valve 7
When the zero valve element 74 advances, the liquid supply hole 77 closes and the liquid discharge hole 78
Is opened, and the rear chamber 4 communicates with the low-pressure circuit 8.

If an appropriate thrust is applied to the breaker main body 11 and the rod 22 is in close contact with the hard rock 102, the thruster 12 is at the rear end where the rear end is in close contact with the breaker main body 11, and the rod 22 is Since the piston 1 is at the predetermined hitting position, the piston 1 hits the rod 22 to stop moving forward and start moving backward. When the piston 1 moves backward and the front chamber 3 communicates with the valve control port 24, the pressure in the valve control chamber 75 becomes high, and the valve body 74 of the control valve 70 moves backward. Here, the rear chamber 4 communicates with the high-pressure circuit 5 to have a high pressure, and the piston 1 that intends to keep moving backward due to inertia is braked, and the kinetic energy of the backward movement is accumulated in an accumulator (not shown) in the form of high-pressure oil. . The piston 1 that has stopped moving backward enters the forward travel again, and the same cycle is repeated thereafter. At this time, the stroke of the piston 1 is long, and a strong impact is applied to the rod 22.

When the rock 102 is soft and the rod 22 bites into the rock 102 at a high speed, and the breaker main body 11 cannot follow the forward movement of the rod 22, the thruster 12 pushes the rod 22 forward. Bedrock 1
02. At this time, the thruster 12 moves forward (to the left in the drawing) with respect to the breaker body 11. When the thruster 12 is displaced in this manner, communication between the operation port 18 and the return port 19 is cut off, and pressure oil leaks from the high-pressure propulsion chamber 20 to the operation port 18 through the clearance 15. This pressure fluid enters the working chamber 45 of the stroke control valve 42 via the operating circuit 17, so that the pressure in the working chamber 45 gradually increases, and the stroke control valve 42 is gradually opened. When the thruster 12 moves further forward, the propulsion chamber 20 and the operation port 18 communicate with each other, and hydraulic oil is released from the operation chamber 4.
5, the stroke control valve 42 is completely opened, and the short stroke port 27 and the valve control chamber 75 are completely communicated via the stroke control circuit 13.

When the short stroke port 27 and the valve control chamber 75 are communicated with each other, the valve control chamber 75 becomes high pressure when the piston 1 moves backward and the front chamber 3 communicates with the short stroke port 27, and the control is performed. The valve element 74 of the valve 70 moves backward. At this point, the rear chamber 4 communicates with the high-pressure circuit 5 to have a high pressure, and the piston 1 stops moving backward and returns to the forward traveling state. As described above, since the timing of entering the forward travel is earlier, the stroke of the piston 1 is shorter.

The forward displacement of the rod 22 is
Is softer, the displacement of the thruster 12 is also larger, but the amount of pressure oil leaking from the clearance 15 increases as the thruster 12 advances, until the propulsion chamber 20 and the working port 18 are completely connected. The opening of the stroke control valve 42 increases in accordance with the amount of pressure oil, and the amount of pressure oil flowing through the stroke control circuit 13 increases accordingly. During this time, the stroke of the piston 1 continuously changes from the maximum to the minimum. And the impact applied to the rod 22 is correspondingly weakened.

As shown in FIG. 4, the clearance 15 is tapered around the thruster 12 so as to have a slightly smaller diameter at the rear, so that the amount of pressure oil leakage accompanying an increase in displacement is increased. Can also. Regardless of the rock quality, even when the rod 22 does not adhere to the bedrock 102 and play occurs due to lack of thrust to the breaker body 11, the thruster 12 presses the rod 22 against the bedrock 102 and the thruster corresponding to the play. The forward movement of 12 controls the stroke of piston 1.

The reaction sensitivity of this stroke control can be arbitrarily adjusted by adjusting the amount of pressure oil flowing into the working chamber 45 by the sensitivity adjusting valve 47 and the amount of pressure oil leaking from the working chamber 4 by the sensitivity adjusting valve 48. Can be changed. By the above operation, the stroke adjusting device of the hydraulic breaker 10 always keeps the rod 22 and the rock 102 in close contact with each other,
For soft rocks, short strokes, high hits produce weak hits, and for hard rocks, long strokes give strong hits,
Good work efficiency can be demonstrated. In addition, even when the thrust is inappropriate or when the rod 22 has play due to sudden destruction of the object to be crushed, it is possible to prevent an idle shot,
The durability of the rod 22 and the breaker body 11 is improved.

In the hydraulic breaker 10, the thruster 12 is in contact with the rod 22, has a large diameter, controls the amount of leak pressure oil at the time of displacement, and operates the operation port 18 and the low-pressure port 1.
9 may be difficult to process. In this case, as shown in FIG.
0 should be provided. The interlocking chamber 51 of the displacement detection piston 50 communicates with the high voltage circuit 5, and when the thruster 12 is displaced, the displacement detection piston 50 is displaced in conjunction therewith. In front of the interlocking chamber 51 of the displacement detection piston 50,
An operation port 58 and a return port 59 are provided, and a communication passage 52 is provided on the circumference of the displacement detection piston 50 so as to communicate the operation port 58 and the return port 59 when the thruster 12 is at the rear position. The operation port 58 is in communication with the operation circuit, and the return port 59 is in communication with the low voltage circuit 8. The displacement detection piston 50 has a clearance 52 around the periphery thereof for allowing the pressure oil in the interlocking chamber 51 to leak to the operation port 18 by the forward displacement of the displacement detection piston 50 accompanying the forward displacement of the thruster 12.

As a result, the piston 1 is moved in the same manner as in FIG.
However, since the displacement detection piston 50 has a smaller diameter than the thruster 12, the clearance 52 around the displacement detection piston 50 can be easily adjusted.
Even if the thruster diameter is large, the amount of pressure fluid leak can be controlled with high accuracy.

[0035]

As described above, the stroke adjusting device of the hydraulic striking device of the present invention always maintains the close contact between the rod and the object to be crushed and realizes a stroke according to the condition of the object to be crushed. Can be adjusted. A control valve for connecting the rear chamber of the piston to a high-pressure circuit and a low-pressure circuit, and a valve control circuit for connecting a valve control port that is opened and closed by forward and backward movement of the piston to a valve control chamber for switching the control valve. ,
A stroke control circuit for connecting a short stroke port provided in front of the valve control port to the valve control chamber, wherein the stroke control mechanism operates the stroke control valve for opening and closing the stroke control circuit and opening the stroke control valve to the open side An operation port connected to the operation chamber to be operated by an operation circuit, a return port connected to the low-pressure circuit, and a communication passage provided on the thruster periphery so as to communicate the operation port and the return port when the thruster is at the rear position. The stroke adjusting device of the hydraulic striking device, which has a clearance around the thruster for allowing the hydraulic fluid in the thruster propulsion chamber to leak to the working port by the forward displacement of the thruster, detects the displacement of the thruster and controls the stroke. Can be done automatically.

A stroke control mechanism includes a stroke control valve for opening and closing a stroke control circuit, a displacement detection piston provided behind the thruster, and an operation circuit connected to an operation chamber for operating the stroke control valve to an open side. A return port connected to the low pressure circuit, a communication passage provided on the circumference of the displacement detection piston so as to connect the operation port and the return port when the thruster is at the rear position, and a high pressure generated by the forward displacement of the thruster. The stroke adjusting device of the hydraulic hitting device, which has a clearance around the displacement detection piston that leaks the hydraulic fluid of the circuit to the working port, makes it easy to adjust the clearance around the displacement detection piston, the thruster diameter is large, and the hydraulic fluid leaks. This is effective when controlling the volume is difficult.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a hydraulic breaker provided with a stroke adjusting device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a hydraulic breaker.

FIG. 3 is an explanatory diagram of a stroke control mechanism.

FIG. 4 is an explanatory view of a thruster having a taper and a clearance gradually increased.

FIG. 5 is an explanatory diagram of a displacement detection piston.

FIG. 6 is a vertical sectional view of a hydraulic breaker provided with a conventional stroke adjusting device.

FIG. 7 is a circuit diagram of a conventional hydraulic breaker.

[Explanation of symbols]

 Reference Signs List 1 piston 1A, 1C small diameter section 1B large diameter section 2 cylinder 3 front chamber 4 rear chamber 5 high pressure circuit 8 low pressure circuit 10 hydraulic breaker 11 breaker body 12 thruster 13 stroke control circuit 14 stroke control mechanism 15 clearance 17 operation circuit 18 operation port 19 Return port 20 Propulsion chamber 21 Communication path 22 Rod 24 Valve control port 25 Drainage port 26 Front chamber high pressure port 27 Short stroke port 29 Rear chamber port 30 Communication groove 31 Valve control circuit 42 Stroke control valve 45 Working chamber 46 Spring 50 Displacement detection Piston 51 Interlocking chamber 52 Communication path 52 Clearance 58 Working port 59 Return port 70 Control valve 75 Valve control chamber

Claims (3)

[Claims] 1. A hydraulic striking device in which a rod is inserted into a striking device body provided with a striking mechanism for reciprocating a piston back and forth by hydraulic pressure, wherein a thruster for pushing the rod forward between the striking device body and the rod. And a stroke control mechanism for changing the stroke of the piston in accordance with the displacement of the thruster in the front-rear direction. 2. A striking mechanism connects a control valve for switching the rear chamber of the piston between a high-pressure circuit and a low-pressure circuit and a valve control port for opening and closing the piston by moving the piston back and forth to a valve control chamber for switching the control valve. A stroke control circuit for connecting a short stroke port provided in front of the valve control port to the valve control chamber, wherein the stroke control mechanism opens and closes the stroke control circuit; An operation port connected by an operation circuit to an operation chamber for operating the valve to the open side, a return port connected to the low-pressure circuit, and a thruster around the thruster so that the operation port communicates with the return port when the thruster is in the rear position. The communication path provided and the clearance around the thruster that causes the hydraulic fluid in the thruster's propulsion chamber to leak to the working port due to the forward displacement of the thruster Stroke adjusting device hydraulic striking device according to claim 1, characterized in that. 3. A striking mechanism connects a control valve for switching the rear chamber of the piston between a high-pressure circuit and a low-pressure circuit, and a valve control port for opening and closing the piston by moving the piston back and forth to a valve control chamber for switching the control valve. A stroke control circuit for connecting a short stroke port provided in front of the valve control port to the valve control chamber, wherein a stroke control mechanism opens and closes the stroke control circuit; A displacement detection piston provided at the rear, an operation port connected by an operation circuit to an operation chamber for operating a stroke control valve to an open side, a return port connected to a low pressure circuit, and an operation when the thruster is at a rear position. A communication passage provided on the circumference of the displacement detection piston so that the port and the return port communicate with each other, and the hydraulic fluid of the high-pressure circuit is operated by the forward displacement of the thruster. Stroke adjusting device hydraulic striking device according to claim 1, characterized by having a displacement detecting piston periphery to leakage clearance to.