JP2017127917A - Hydraulic striking device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic striking device which has comparatively high stability of action for controlling a stroke of a piston.SOLUTION: A hydraulic striking device includes: a cylinder 100 which has a short stroke port SP, a long stroke port LP, and a stroke switching port MP provided between those two ports; a piston 122 slidably fitted in the inside of the cylinder 100; a piston front chamber 101 and a piston rear chamber 102 defined between an outer peripheral surface of the piston 122 and an inner peripheral surface of the cylinder 100; a driving direction switch valve 300 which switches at least one of the piston front chamber 101 and the piston rear chamber 102 to at least one of a high-pressure circuit 113 and a low-pressure circuit 119 to drive the piston 122 by a selected stroke; and a stroke selection valve 200 which selects the stroke by the driving direction switch valve 300 according to fore-and-aft traveling position of the piston 122 to the three ports SP, MP, and LP.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydraulic striking device such as a rock drill or a breaker, and more particularly to a technique for automatically switching a piston stroke to a stroke selected from one of a short stroke and a long stroke.

In this type of hydraulic striking device, the stroking force is set appropriately by automatically switching the piston stroke from one of the short stroke and long stroke according to the hardness of the rock (penetration amount into the rock). Various techniques for reducing excessive load on the striking portion such as the rod and the rod pin by adjusting are proposed.
For example, in the technique described in Patent Document 1, a throttle is provided in an oil passage for operating a valve for stroke control when the stroke of the piston is controlled, and the switching timing is adjusted by this throttle.

US 201403264473 A1

However, the technique described in Patent Document 1 has a problem that the operation is likely to become unstable with respect to the temperature change of the hydraulic oil because the switching timing of the valve for stroke control is adjusted by the throttle.
Therefore, the present invention has been made paying attention to such problems, and an object of the present invention is to provide a hydraulic striking device with relatively high stability of operation for controlling the stroke of the piston.

  In order to solve the above-described problem, a hydraulic striking device according to one aspect of the present invention strikes a striking rod by moving a piston back and forth in a cylinder by a stroke selected from one of a short stroke and a long stroke. A hydraulic striking device, comprising: a cylinder having a short stroke port, a long stroke port, and a stroke switching port provided at a position between the two ports as three ports for stroke control; The piston slidably fitted to the piston, the piston front chamber and the piston rear chamber defined between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder and spaced apart in the axial direction, and the front of the piston Switch at least one of the chamber and the piston rear chamber to at least one of a high pressure circuit and a low pressure circuit A drive direction switching valve that drives the piston at the selected stroke, and a stroke selection valve that selects the stroke by the drive direction switching valve in accordance with the forward / backward movement position of the piston with respect to the three ports. It is characterized by that.

  Here, in the hydraulic striking device according to one aspect of the present invention, the stroke selection valve is configured to change the pressure of the hydraulic oil supplied to the stroke switching port according to the forward / backward movement position of the piston. A spool that moves between a short stroke position for switching the driving direction switching valve at the timing of the short stroke and a long stroke position for switching the driving direction switching valve at the timing of the long stroke; As the advance position, the position where the piston has advanced a predetermined amount beyond the striking point when moving forward is called a switching position, and when the position when the piston moves forward does not reach the switching position, the spool When the piston is in the stroke position and the forward position of the piston reaches the switching position, While moving to the short stroke position, it is preferable that the piston is configured to return to the long stroke position while not reaching the switching position A during forward by a short stroke.

  Further, in the hydraulic striking device according to one aspect of the present invention, the stroke selection valve has a pressure receiving surface at one end thereof always connected to a high pressure circuit and a pressure receiving surface at the other end thereof is supplied to the stroke switching port. Only the flow of pressure oil from the drive direction switching valve side is allowed to the oil passage in which the spool that is slid to receive the pressure of the hydraulic oil and the pressure receiving surface of the other end communicate with the stroke switching port. A reset oil passage for supplying pressure oil via a check valve, and the spool is a pressure oil in the reset oil passage while the piston is advanced by the short stroke and does not reach the switching position. Is preferably provided so as to return to the long stroke position.

  Further, in the hydraulic striking device according to one aspect of the present invention, the hydraulic striking device always sets the piston front chamber to a high pressure, and the piston rear chamber is switched to a high pressure circuit and a low pressure circuit by switching by the driving direction switching valve. The front chamber always high-pressure rear chamber alternating switching system for switching the piston forward and backward, and when the piston moves forward to the switching position, the stroke switching port communicates the stroke switching port with a low-pressure circuit. It is preferable that the spool of the stroke selection valve is provided to move to the short stroke position.

Further, in the hydraulic striking device according to one aspect of the present invention, the switching position is such that, when the piston moves forward, the rear end of the front large-diameter portion formed in the axial front of the piston faces the stroke switching port. The stroke switching port is in a position to communicate with a low pressure circuit, and the stroke selection valve is configured such that the high pressure oil supplied to the pressure receiving surface at the other end is transferred from the stroke switching port to the tank port. It is preferable that the spool is provided so as to move to the short stroke position by being discharged.
Further, in the hydraulic striking device according to one aspect of the present invention, the spool is formed along the central axis direction of the spool and receives the pressure of the hydraulic oil supplied to the stroke switching port. It is preferable to have a central passage that opens to a surface, and a communication port that is formed at a position where the central passage communicates with the high-pressure circuit when it is in the long stroke position.

  According to the hydraulic striking device according to one aspect of the present invention, the cylinder has three stroke control ports, a short stroke port, a long stroke port, and a stroke switching port provided at a position between these two ports. The stroke selection valve selects the stroke by the drive direction switching valve according to the forward / backward movement position of the piston with respect to the three ports, so that the stroke selection valve has a simple structure without a throttle and penetrates into the bedrock. With respect to the amount, the stroke of the piston can be automatically switched by simple oil path switching based on the positions of the three ports set in accordance with the forward / reverse position of the piston. Therefore, since it is not influenced by the temperature change of hydraulic fluid, the operation | movement stability of a stroke selection valve is comparatively high. Hereinafter, a series of mechanisms capable of automatically switching the stroke of the piston is also referred to as an “auto stroke mechanism”.

  As described above, according to the present invention, the stability of the operation for controlling the stroke of the piston is relatively high.

It is explanatory drawing of one Embodiment of the hydraulic striking device which concerns on 1 aspect of this invention, and the figure has shown the state of each part when a piston is located in a front dead center. In addition, in the same figure, the cross section along the axis line of each part is shown about the principal part of a hydraulic striking device. In the drawing, the high-pressure oil passage is indicated by a thick solid line and a dark shaded area, and the low-pressure oil passage is indicated by a broken line and a light shaded area (the same applies to the other drawings hereinafter). It is a figure explaining operation | movement of the automatic stroke mechanism of the hydraulic striking device of FIG. 1 (hereinafter, the same applies to other drawings). In this figure, when the piston is retracted from the front dead center to the short stroke port during operation. The state of each part is shown. This figure shows the state of each part when the reset port operates while the piston is moving forward with a short stroke. This figure shows the state of each part when the piston moves forward and starts retreating at the striking point. This figure shows the state of each part when the piston moves back to the long stroke port when the piston moves backward at the striking point. This figure shows the state of each part when the piston moves forward to the position of the stroke switching port when the piston moves forward beyond the striking point. This figure shows the state of each part when the piston moves back to the short stroke port after the piston moves forward beyond the striking point. This figure shows the state of each part when the reset port operates while the piston is moving forward with a short stroke. It is a figure which shows the modification of the hydraulic striking device which concerns on 1 aspect of this invention, In the same figure, the part of the stroke selection valve is shown.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate. The drawings are schematic. For this reason, it should be noted that the relationship between the thickness and the planar dimension, the ratio, and the like are different from the actual ones, and the dimensional relationship and the ratio are different between the drawings. Further, the following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is the material, shape, structure, and arrangement of components. Etc. are not specified in the following embodiments.

As shown in FIG. 1, the hydraulic striking device includes a cylinder 100 and a piston 122. A back head 400 is attached to the rear portion of the cylinder 100. The back head 400 is filled with high-pressure gas. A front head 500 is attached to the front portion of the cylinder 100. A rod 510 is slidably fitted inside the front head 500.
The piston 122 is a solid cylindrical body, and has two large-diameter portions 123 and 124 at substantially the center thereof. An annular valve switching groove 127 is formed in the approximate center of the two large diameter portions 123 and 124. A medium-diameter portion 125 is provided in front of the front large-diameter portion 123 in the front in the axial direction, and a small-diameter portion 126 is provided in the rear of the rear large-diameter portion 124 in the rear in the axial direction.

The piston 122 is slid into the cylinder 100, so that a piston front chamber 101 and a piston rear chamber 102 are defined on the front and rear sides of the cylinder 100, respectively. In the present embodiment, the high pressure port P of the piston front chamber 101 is always connected to the high pressure circuit 113 via the piston front chamber passage 116.
On the other hand, a drive direction switching valve 300 is attached to the side surface of the cylinder 100, and the piston rear chamber 102 is respectively transferred to the high pressure circuit 113 and the low pressure circuit 119 by forward / reverse switching by the control valve 301 of the drive direction switching valve 300. Communication is possible alternately. The high voltage circuit 113 is provided with an accumulator (not shown).

The outer diameter of the medium diameter portion 125 is set larger than the outer diameter of the small diameter portion 126. Accordingly, the pressure receiving area of the piston 122 in the piston front chamber 101 and the piston rear chamber 102, that is, the diameter difference between the front large diameter portion 123 and the medium diameter portion 125, and the diameter difference between the rear large diameter portion 124 and the small diameter portion 126 are as follows. The piston rear chamber 102 side is larger.
Thereby, when the piston rear chamber 102 is connected to the high pressure by the operation of the control valve 301, the piston 122 moves forward due to the pressure receiving area difference, and when the piston rear chamber 102 is connected to the low pressure by the operation of the control valve 301, the piston 122 moves backward. It is like that.

Here, the hydraulic striking device includes an auto stroke mechanism that strikes the rod 510 by moving the piston 122 back and forth in the cylinder 100 by a stroke automatically selected from one of a short stroke and a long stroke.
Specifically, the cylinder 100 includes, as three ports for stroke control, a short stroke port SP, a long stroke port LP, and a stroke switching port MP provided at a position between these two ports SP, LP in the axial direction. It is in a separated position. The high pressure port P of the piston front chamber 101 is provided in front of the short stroke port SP, and the tank port T of the cylinder 100 is provided in the rear of the long stroke port LP.

As shown in the figure, the drive direction switching valve 300 has a switching valve chamber 312 formed non-coaxially with the piston 122 inside, and the control valve 301 is slidably fitted into the switching valve chamber 312. . The control valve 301 has a medium diameter portion 302, a large diameter portion 303, and a small diameter portion 304 in order from the front to the rear.
Further, the switching valve chamber 312 has a medium-diameter valve front chamber 313, a large-diameter valve main chamber 314, and a small-diameter valve rear chamber 315 in order from the front to the rear. A high pressure oil passage 324 that is always in communication with the high pressure circuit 113 is connected to the valve front chamber 313.

  In the valve main chamber 314, a low pressure port 318, a reset port RP, a pilot port PP, a tank port T, and a rear chamber port 322 are provided in the upper part of the drive direction switching valve 300 in order from the front to the rear. Yes. The low pressure port 318 is always in communication with the low pressure circuit 325, and the tank port T is always in communication with the low pressure circuit 119. The rear chamber port 322 communicates with the piston rear chamber 102 via the rear chamber passage 330. In addition, the pilot port PP communicates with the long stroke port LP of the cylinder 100 through the long stroke passage 111 below the drive direction switching valve 300.

  The control valve 301 is a hollow cylindrical body, and a hollow passage 323 inside the cylinder is always in communication with the high-pressure circuit 113 via a high-pressure oil passage 324. In the control valve 301, an oil drain groove 305 for switching the piston rear chamber 102 to a low pressure is provided in an annular shape on the outer peripheral surface substantially at the center of the small diameter portion 304. The oil drain groove 305 is formed so that the tank port T and the valve rear chamber 315 can communicate with each other when the control valve 301 is in the retracted position in FIG. Further, a communication hole 310 is formed on the front side of the oil drain groove 305 of the control valve 301 so as to penetrate in the radial direction of the control valve 301. Furthermore, a slit groove 311 is formed in a slit shape along the axial direction on the outer peripheral surface on the front side of the control valve 301.

The control valve 301 of the present embodiment is always urged rearward due to the pressure receiving area difference between the medium diameter portion 302 and the small diameter portion 304, and when high pressure oil is supplied to the pilot port PP, The pressure receiving area of the side stepped surface 309 is added to move forward.
As shown in the figure, when the control valve 301 is in the rear end position, the rear chamber port 322 communicates with the low pressure port T through the oil drain groove 305, so that the piston rear chamber 102 is connected to the low pressure. On the other hand, when the control valve 301 is at the front end position (see FIG. 2), the rear chamber port 322 is provided between the rear end surface 307 of the control valve 301 and the rear end surface 317 of the switching valve chamber 312 and the hollow passage 323. Since the piston chamber 102 communicates with the valve chamber 312 connected via high pressure via the piston, the piston rear chamber 102 is connected with high pressure.

Here, since the pilot breaker PP must maintain high pressure or low pressure in the hydraulic breaker, the control valve 301 needs a holding mechanism for maintaining the stop state at the switching position of the front end and the rear end.
In the present embodiment, the holding mechanism when the control valve 301 is at the rear end position is the slit groove 311. When the control valve 301 is in the rear end position, the slit groove 311 allows the pilot port PP, the reset port RP, and the low pressure port 318 to communicate with each other, so that the rear stepped surface 309 is reliably connected to the low pressure and the control valve 301 is stopped. The state is to be maintained.

The holding mechanism when the control valve 301 is in the front end position is the communication hole 310. When the control valve 301 is at the front end position, the communication hole 310 prevents the holding pressure from being lowered by replenishing the pilot port PP (and the reset port RP) with pressure oil from the hollow passage 323. The stop state 301 is maintained.
Here, the automatic stroke mechanism of the hydraulic striking device of the present embodiment has a stroke selection valve 200 provided on the side surface of the cylinder 100 adjacent to the drive direction switching valve 300. In the figure, for convenience of explanation, the stroke selection valve 200 is illustrated at a separated position.

As shown in the figure, the stroke selection valve 200 has a substantially rectangular parallelepiped housing 210, and a valve chamber 250 is formed in the housing 210. In the example of the present embodiment, a plurality of sleeves 231 to 235 are sequentially stacked in the housing 210, and an internal space formed by the plurality of sleeves 231 to 235 is a valve chamber 250.
The positions of the plurality of sleeves 231 to 235 are fixed by tightening a plug 236 screwed into the upper opening of the housing 210. As the spool 220 is slidably fitted in the valve chamber 250, a control chamber 252 is defined on the lower side of the spool 220, and a high-pressure chamber 251 is defined on the upper side of the spool 220. .

The spool 220 of the present embodiment is a solid cylindrical member having a plurality of step portions formed on the outer peripheral surface, and has an annular control groove 224 at a substantially central portion, and two front and rear of the control groove 224. Two large diameter portions 225, 226 are provided. The upper portion of the large diameter portion 226 on the upper side of the drawing is a small diameter portion 227, and the lower portion of the large diameter portion 225 on the lower side of the drawing is a medium diameter portion 228. The outer diameter of the medium diameter part 228 is set larger than the outer diameter of the small diameter part 227.
A control port 241 that communicates with the control chamber 252 is provided at the lower end of the control chamber 252. The control port 241 is connected to the stroke switching port MP of the cylinder 100. Further, a reset oil passage 326 is connected to the control port 241 via the check valve 260 to the reset port RP of the drive direction switching valve 300. The check valve 260 is provided so as to allow the flow of pressure oil from the reset port RP side to the control port 241 side, but not flow the pressure oil in the opposite direction.

  Further, a first tank port 242, a short stroke communication port 243, a long stroke communication port 327, a second tank port 245, and a high pressure port 246 are provided on the side surface of the housing 210 in order from the lower side of the figure. The short stroke communication port 243 is connected to the short stroke port SP of the cylinder 100. The long stroke communication port 327 is connected to the pilot port PP of the drive direction switching valve 300.

The first tank port 242 and the second tank port 245 are connected to the low pressure circuit 119. A high pressure port 246 communicating with the high pressure circuit 113 is connected to the high pressure chamber 251 above the spool 220, and the high pressure chamber 251 is constantly at high pressure.
When high pressure oil is supplied to the control port 241, the diameter difference between the small diameter portion 227 and the medium diameter portion 228 is larger on the medium diameter portion 228 side, so the lower control chamber 252 and the upper high pressure chamber are Due to the pressure receiving area difference of the spool 220 at 251, the spool 220 moves upward. At low pressure when high pressure oil is not supplied to the control port 241, the spool 220 moves downward as shown in FIG. It has become.

In the stroke selection valve 200, when the spool 220 moves downward as shown in the figure, the short stroke communication port 243 and the long stroke communication port 327 are communicated with each other via the control groove 224, and the spool 220 is moved upward. When moved, mutual communication is cut off.
Hereinafter, the time when the spool 220 moves upward is also referred to as “long stroke position”, and the time when the spool 220 moves downward is also referred to as “short stroke position”. Further, as the forward / backward moving position of the piston 122, a position where the piston 122 has advanced a predetermined amount beyond the striking point during forward movement is also referred to as a “switching position”.

Next, the operation, action and effect of the automatic stroke mechanism of this hydraulic striking device will be described. In each figure, the high-pressure oil passage is indicated by a thick solid line, and the low-pressure oil passage is indicated by a broken line.
In the hydraulic striking device, as shown in FIG. 1, the piston 122 is pressed forward by the gas pressure F of the high-pressure gas sealed in the back head 400 before the operation. Therefore, the piston 122 is at the position of the front dead center.

At the start of operation, when the piston 122 is at the position of the front dead center, the spool 220 of the stroke selection valve 200 is always connected to the high pressure circuit 113 in the upper high pressure chamber 251 shown in FIG. The circuit 119 is connected. Therefore, the spool 220 is pressed toward the lower side of the figure and is positioned at the “short stroke position”.
At the start of operation, since the high-pressure oil of the high-pressure circuit 113 is supplied to the valve front chamber 313, the control valve 301 is positioned at the reverse position. When the control valve 301 of the drive direction switching valve 300 is in the retracted position, the drive direction switching valve 300 connects the piston rear chamber 102 to the low pressure circuit 119.

Now, when the hydraulic striking device is operated, the high pressure oil of the high pressure circuit 113 is supplied to the piston front chamber 101 so that the piston front chamber 101 is constantly at a high pressure, while the control valve 301 of the drive direction switching valve 300 is moved backward. At the position, the piston rear chamber 102 is at a low pressure, so that the piston 122 is urged rearward and starts moving backward.
As shown in FIG. 2, when the front end of the front large-diameter portion 123 of the piston 122 is retracted to the position of the short stroke port SP of the cylinder 100, the high pressure introduced into the short stroke port SP from the always-high piston front chamber 101. As shown in the figure, the oil is introduced into the pilot port PP of the drive direction switching valve 300 through the control groove 224 of the spool 220 in the “short stroke position” within the stroke selection valve 200.

  When high pressure oil is supplied to the pilot port PP, the driving direction switching valve 300 adds the pressure receiving area of the rear stepped surface 309 and moves the control valve 301 forward. As a result, the rear chamber port 322 communicates with the valve chamber 312 between the rear end surface 307 of the control valve 301 and the rear end surface 317 of the switching valve chamber 312 and the high pressure connection via the hollow passage 323. 102 is connected to a high voltage. Therefore, since the piston rear chamber 102 becomes a high pressure, the piston 122 starts moving forward with a short stroke due to its pressure receiving area difference.

Here, in the auto stroke mechanism of this embodiment, the check valve 260, the reset passage 326, and the reset port RP are provided as means for supplying pressure oil to the control port 241 of the stroke selection valve 200.
That is, when the control valve 301 of the drive direction switching valve 300 is switched to the forward position, the pilot port PP and the reset port RP communicate with each other through the rear stepped surface 309 as shown in FIG. Is supplied from the reset passage 326 to the control port 241 of the stroke selection valve 200 via the check valve 260.

  As a result, as shown in the figure, the stroke selection valve 200 is pushed upward in the figure due to the pressure receiving area difference between the small diameter part 227 above and below the spool 220 and the medium diameter part 228, so that the "long stroke position" is reached. Switch. At this time, the reset port RP is replenished with pressure oil from the communication hole 310 via the pilot port PP. Therefore, sufficient pressure oil is supplied to maintain the stop state of the control valve 301 and operate the spool 220 of the stroke selection valve 200 (in FIG. 3, the spool 220 moves upward and maintains the stopped state after the movement). Is done.

  Next, the piston 122 moves forward, and as shown in FIG. 4, the position of the piston 122 at the striking point, that is, the rear end of the front large diameter portion 123 of the piston 122 passes the position of the long stroke port LP of the cylinder 100. Then, the tank port T of the cylinder 100 and the long stroke port LP communicate with each other, and the pilot port PP of the drive direction switching valve 300 is connected to a low pressure. As a result, the control valve 301 of the drive direction switching valve 300 is pressed rearward to switch to the retracted position, and the piston rear chamber 102 becomes low pressure accordingly.

Here, when the piston rear chamber 102 is at a low pressure, the piston 122 moves backward with a slight penetration amount when the rock is hard. At this time, since the pressure oil communicating with the stroke switching port MP is held in the lower control port 241 of the stroke selection valve 200, the spool 220 of the stroke selection valve 200 maintains the “long stroke position”.
That is, until the piston 122 moves backward and the control valve 301 is switched, the long stroke port LP of the cylinder 100 continues to communicate with the tank port T, so that the pilot port PP of the drive direction switching valve 300 is connected to the tank port T. Keep communicating. As a result, the pressure oil at the stroke switching port MP of the cylinder 100 is held in the closed circuit, so that the “long stroke position” is held so that the control valve 301 is not switched.

In this way, when the rock is hard, the control valve 301 is held at the “long stroke position” when the piston 122 moves backward, so that the front end of the front large-diameter portion 123 of the piston 122 is short-circuited with the cylinder 100. The high pressure oil introduced into the short stroke port SP is blocked by the stroke selection valve 200 even when the stroke port SP is retracted to the position. Therefore, the piston 122 can continue to retreat.
Further, even if the front end of the front large-diameter portion 123 of the piston 122 is retracted to the position of the stroke switching port MP of the cylinder 100, the high pressure oil introduced into the stroke switching port MP is blocked by the stroke selection valve 200. The piston 122 can be retracted. That is, according to this hydraulic striking device, when the rock is hard, the piston 122 can automatically perform striking with a long stroke.

Next, as shown in FIG. 5, when the front end of the front large diameter portion 123 of the piston 122 is retracted to the position of the long stroke port LP of the cylinder 100, the long stroke port LP communicates with the high pressure oil in the piston front chamber 101. Therefore, high pressure oil is introduced into the pilot port PP of the drive direction switching valve 300 via the long stroke port LP.
As a result, the control valve 301 moves to the forward position due to the pressure receiving area difference between the front and rear of the control valve 301 of the drive direction switching valve 300, and the rear chamber port 322 has the rear end surface 307 of the control valve 301 and the rear end surface of the switching valve chamber 312. Since it communicates with the valve chamber 312 connected to the high pressure via the hollow passage 323, the piston rear chamber 102 is connected to the high pressure and the piston rear chamber 102 becomes high pressure. Therefore, the piston 122 starts moving forward due to the pressure receiving area difference between the front and rear of the piston 122.

At this time, the operating pressure oil of the drive direction switching valve 300 is introduced into the stroke selection valve 200 from the reset port RP to the control port 241 below the stroke selection valve 200 via the check valve 260 of the reset oil passage 326. Therefore, the spool 220 maintains the “long stroke position” in the upper part of the drawing due to the pressure receiving area difference between the small diameter portion 227 above and below the spool 220 and the medium diameter portion 228.
Here, when the bedrock is soft, even after the piston 122 hits the bedrock, the piston 122 further advances beyond the position of the hitting point shown in FIG. At this time, in the hydraulic striking device of the present embodiment, as shown in FIG. 6, when the piston 122 further advances beyond the striking point, the rear end of the front large diameter portion 123 of the piston 122 is the cylinder 100. When the stroke change port MP is reached, the stroke change port MP is connected to the tank port T and is connected to a low pressure. Therefore, the high pressure oil in the control port 241 on the lower side of the stroke selection valve 200 is released, whereby the spool 220 of the stroke selection valve 200 is pressed downward to switch to the “short stroke position”.

  Next, when the piston 122 is retracted and the front end of the front large-diameter portion 123 of the piston 122 is retracted to the position of the short stroke port SP of the cylinder 100 as shown in FIG. Since 220 is in the “short stroke position”, the high pressure oil in the piston front chamber 101 is introduced from the short stroke port SP to the pilot port PP of the drive direction switching valve 300 through the control groove 224 of the stroke selection valve 200.

  Therefore, the control valve 301 of the drive direction switching valve 300 is switched to the forward position, and the piston rear chamber 102 becomes high pressure accordingly. Therefore, the piston 122 starts to advance in a short stroke due to the difference in pressure receiving area before and after itself. That is, according to this hydraulic striking device, when the rock is soft, the stroke selection valve 200 is switched to the “short stroke position” at the “switching position”, and the piston 122 automatically strikes with the short stroke. be able to.

  When the control valve 301 switches to the forward position, the operating pressure oil of the control valve 301 introduced into the pilot port PP is transferred from the reset port RP of the drive direction switching valve 300 to the reset oil path 326 as shown in FIG. The check valve 260 is introduced into the control port 241 below the stroke selection valve 200. As a result, the stroke selection valve 200 is moved upward due to a pressure receiving area difference between the upper and lower small diameter portions 227 and the middle diameter portion 228 while the piston 122 is moving forward by a short stroke and does not reach the “switching position”. Pressed to switch to “long stroke position”. In other words, the stroke selection valve 200 is reset from the short stroke state to the long stroke state.

  This long stroke state is the same as the state shown in FIG. Therefore, hereinafter, in this hydraulic striking device, as described above, the piston 122 repeatedly moves forward and backward by the cooperation of the piston 122, the drive direction switching valve 300, and the stroke selection valve 200 according to the hardness of the rock. When the rock 510 is hit but the rock is hard (that is, when the forward movement position of the piston 122 does not reach the “switching position”), as described with reference to FIGS. When the rock is soft and rocks back and forth with a long stroke (that is, when the forward movement position of the piston 122 reaches the “switching position”), as described with reference to FIGS. Move back and forth with a short stroke.

  Therefore, according to this hydraulic striking device, the stroke of the piston 122 is automatically switched to a stroke selected from one of the short stroke and the long stroke according to the hardness of the rock (the amount of penetration into the rock). By appropriately adjusting the force, it is possible to reduce an excessive load on the striking portions such as the rod 510 and the rod pin.

  In particular, according to this hydraulic striking device, the cylinder 100 is provided with a short stroke port SP, a long stroke port LP, and a stroke switching port MP provided at a position between these two ports SP and LP to select a stroke. When the valve 200 reaches a position communicating with a stroke switching port MP that forcibly switches the stroke when the piston 122 moves forward with respect to the control chamber 252 at the other end while the high-pressure chamber 251 at one end is constantly at a high pressure, By connecting the control chamber 252 of the stroke selection valve 200 to the low pressure circuit 119, the stroke selection valve 200 is switched to the “short stroke position”, and when the piston 122 is retracted, the control chamber 252 is communicated to the high pressure circuit 113. Reset stroke to long stroke Since it is switched to the “long stroke position”, a stroke switching port MP is added to the cylinder 100, so that the stroke selection valve 200 is not provided with a throttle, and the amount of penetration into the rock is simply set according to the position of the piston 122. The stroke of the piston 122 can be forcibly switched by switching the oil path. Therefore, for example, compared to a structure in which the stroke selection valve 200 is provided with a throttle, the operation of the stroke selection valve 200 can be said to be highly stable because it is not affected by the temperature change of the hydraulic oil.

It should be noted that the hydraulic striking device according to the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit of the present invention.
For example, in the hydraulic striking device of the above embodiment, the piston front chamber 101 is always set to high pressure, the piston rear chamber 102 is switched between high pressure and low pressure, and the piston 122 is moved back and forth (the front chamber always high pressure rear chamber alternating switching method). However, the present invention is not limited to this. For example, the piston rear chamber 102 is always set to high pressure, and the piston front chamber 101 is switched between high pressure and low pressure to move the piston 122 back and forth (the rear chamber always high pressure front chamber). (Alternating switching system) or a hydraulic striking device of a system in which the piston 122 is moved back and forth by alternately switching the piston front chamber 101 and the piston rear chamber 102 between high pressure and low pressure (front / rear chamber alternating switching system). it can.

  Here, in the hydraulic striking device according to the above-described embodiment, since the pressure oil of the stroke switching port MP of the cylinder 100 is held in the closed circuit at the long stroke position, the long stroke position is held. Explained. However, in the above-described embodiment, the stroke switching port MP in the closed circuit and the long stroke port LP communicating with the tank port T are adjacent to each other, and it is generally arranged to set a large clearance. It is a sliding part of a typical piston large diameter part. Therefore, if the oil retained in the stroke switching port MP leaks to the long stroke port LP, the holding force of the control port 241 of the stroke selection valve 200 may be insufficient, and the spool 220 may move downward in the figure.

Therefore, in order to prevent insufficient holding force due to this leak, as shown in a modification in FIG. 9, a central passage 271 formed along the central axis direction of the spool 220 and communicating with the control chamber 252 and the spool 220 are provided. It is preferable to provide a communication port 272 formed at a position where the central passage 271 and the high-pressure chamber 251 communicate with each other when in the long stroke position.
That is, in the spool 220, the central passage 271 is open to a pressure receiving surface that receives the pressure of the hydraulic oil supplied to the stroke switching port MP, and the communication port 272 is formed when the spool 220 is in the long stroke position. The central passage 271 is connected to the high pressure circuit with respect to the high pressure chamber 251.

According to the modification shown in FIG. 9, by providing the spool 220 with the central passage 271 and the communication port 272, when the holding pressure of the stroke switching port MP to the control port 241 decreases due to pressure oil leakage, the high pressure chamber 251 side , Pressure oil is replenished to the control port 241 through the communication port 272 and the central passage 271. Therefore, even if a leak occurs, the long stroke position of the spool 220 can be held more reliably.
In particular, according to this modification, since the communication port 272 is set to have a small diameter (orifice), there is almost no leak of pressure oil when the spool 220 normally operates, but when the spool 220 stops at the long stroke position. And when a pressure difference arises between the high pressure chamber 251 and the control port 241, pressure oil leaks, a pressure difference is eliminated, and the holding pressure by the side of the control port 241 can be maintained stably.

100 cylinder 101 piston front chamber 102 piston rear chamber 111 long stroke passage 113 high pressure circuit 116 piston front chamber passage 119 low pressure circuit 122 piston 123 front large diameter portion 124 rear large diameter portion 125 medium diameter portion 126 small diameter portion 127 valve switching groove 200 Stroke selection valve 210 Housing 220 Spool 224 Control groove 225 Large diameter portion 226 Large diameter portion 227 Small diameter portion 228 Medium diameter portion 231 to 235 Sleeve 236 Plug 240 Reset oil passage 241 Control port 242 First tank port 243 Short stroke communication port 244 Long Stroke communication port 245 Second tank port 246 High pressure port 250 Valve chamber 251 High pressure chamber 252 Control chamber 260 Check valve 300 Drive direction switching valve 301 Control valve 302 Medium diameter portion 303 Large diameter portion 304 Small diameter portion 305 Oil drain groove 306 Front end surface 307 Rear end surface 308 Front side stepped surface 309 Rear side stepped surface 310 Communication hole 311 Slit groove 312 Switching valve chamber 313 Valve front chamber 314 Valve main chamber 315 Valve rear chamber 316 Valve chamber front end surface 317 Valve chamber rear end surface 318 Low pressure port 322 Rear chamber port 323 Hollow passage 324 High pressure oil passage 325 Low pressure circuit 326 Reset passage 327 Long stroke communication port 330 Rear chamber passage 400 Back head 500 Front head 510 Rod LP Long stroke Port MP Stroke switching port PP Pilot port RP Reset port SP Short stroke port T Tank port

Claims (6)

A hydraulic striking device for striking a striking rod by moving a piston back and forth in a cylinder by a stroke selected from one of a short stroke and a long stroke,
As the three ports for stroke control, the cylinder having a short stroke port, a long stroke port, and a stroke switching port provided at a position between these two ports, and the piston slidably fitted in the cylinder, A piston front chamber and a piston rear chamber defined between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder and spaced apart in the axial direction, and at least of the piston front chamber and the piston rear chamber A driving direction switching valve that switches one side to at least one of a high-pressure circuit and a low-pressure circuit to drive the piston with the selected stroke, and the stroke by the driving direction switching valve moves the piston forward and backward with respect to the three ports. A hydraulic striking valve comprising a stroke selection valve that is selected according to the position. Apparatus. The stroke selection valve is a short stroke that switches the drive direction switching valve at the timing of the short stroke in accordance with the pressure of the hydraulic oil supplied to the stroke switching port according to the forward / backward movement position of the piston. A spool that moves to a position and a long stroke position that switches the drive direction switching valve at the timing of the long stroke;
When the piston is moved forward and backward, the position where the piston has advanced a predetermined amount beyond the striking point when moving forward is called a switching position.
The spool moves to the long stroke position when the forward position of the piston does not reach the switching position, and moves to the short stroke position when the forward position of the piston reaches the switching position. The hydraulic striking device according to claim 1, wherein the piston is returned to the long stroke position while the piston is moving forward by a short stroke and does not reach the switching position. The stroke selection valve has the spool that is slidably fitted so that the pressure receiving surface at one end thereof is always connected to the high-pressure circuit and the pressure receiving surface at the other end thereof receives the pressure of the hydraulic oil supplied to the stroke switching port. ,
A reset oil passage that supplies pressure oil via a check valve that allows only the flow of pressure oil from the drive direction switching valve side is provided in an oil passage in which the pressure receiving surface at the other end communicates with the stroke switching port. And
The spool is provided so as to return to the long stroke position by pressure oil in the reset oil passage while the piston moves forward by the short stroke and does not reach the switching position. The hydraulic striking device as described. In the hydraulic striking device, the piston front chamber is always at a high pressure, and the piston rear chamber is switched between a high pressure circuit and a low pressure circuit by switching by the drive direction switching valve, and the piston is moved forward and backward. It is an alternating switching method,
The stroke switching port is provided to move the spool of the stroke selection valve to the short stroke position by communicating the stroke switching port with a low pressure circuit when the piston moves forward to the switching position. Item 4. The hydraulic striking device according to Item 2 or 3. The switching position is a position where, when the piston moves forward, the rear end of the front large-diameter portion formed forward in the axial direction of the piston faces the stroke switching port, and the stroke switching port communicates with the low pressure circuit. And
The stroke selection valve is provided such that the high-pressure oil supplied to the pressure receiving surface at the other end is discharged from the stroke switching port to the tank port, so that the spool moves to the short stroke position. The hydraulic striking device according to claim 4.   The spool is formed along the direction of the central axis of the spool and has a central passage that opens to the pressure receiving surface of the other end that receives the pressure of the hydraulic oil supplied to the stroke switching port, and the spool is in the long stroke position. The hydraulic striking device according to any one of claims 3 to 5, further comprising a communication port formed at a position where the central passage communicates with the high-pressure circuit.

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