JP6265418B2 - Hydraulic striking device - Google Patents

Description

  The present invention relates to a hydraulic striking device such as a rock drill or a breaker.

As this type of hydraulic striking device, for example, a technique described in Patent Document 1 is known.
The hydraulic striking device described in Patent Document 1 includes a piston having a large diameter portion at the center in the axial direction and small diameter portions formed before and after the large diameter portion. The piston is slidably fitted into the cylinder, so that a front chamber and a rear chamber are defined between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder.

The front chamber is always communicated with the high pressure circuit, while the rear chamber is alternately communicated with the high pressure circuit and the low pressure circuit by the switching valve mechanism. When the rear chamber communicates with the high-pressure circuit, the front and rear pressure receiving areas are made different so that the piston moves in the striking direction, so that the forward and backward movements of the piston are repeated in the cylinder (hereinafter referred to as the following). , Also called “rear chamber alternating switching method”).
By the way, the hydraulic striking device described in Patent Document 1 adopting the “rear chamber alternate switching method” moves the piston in the striking direction by the pressure receiving area difference at the time of striking as described above. Therefore, the hydraulic oil on the front chamber side acts to resist the movement of the piston in the striking direction. For this reason, there is room for consideration in further improving the hitting efficiency.

  On the other hand, for example, Patent Document 2 discloses a hydraulic striking device that switches a front chamber and a rear chamber alternately between a high-pressure circuit and a low-pressure circuit (hereinafter, also referred to as “front and rear chamber alternate switching method”). . With the hydraulic striking device of the “front / rear chamber alternate switching method”, the front chamber is switched to the low pressure circuit when the piston moves forward, so that the hydraulic oil on the front chamber side does not resist the movement of the piston in the striking direction. Therefore, it is suitable for improving the hitting efficiency.

Japanese Utility Model Publication No. 61-169588 Japanese Patent Laid-Open No. 46-1590 Japanese Utility Model Publication No. 5-39877

  However, in the hydraulic striking device of the “front / rear chamber alternating switching method”, the hydraulic fluid undergoes a rapid pressure fluctuation in the front chamber in a normal striking phase in which the piston reverses from the striking step in which the piston moves forward and shifts to the retreating step. The hydraulic fluid pressure fluctuation problem in the front chamber is not a serious problem in the hydraulic rear impact device of the “rear chamber alternate switching method” because the front chamber is always in communication with the high pressure circuit. On the other hand, the hydraulic striking device of the “front and rear chamber alternate switching method” has a problem that cavitation erosion easily occurs because a negative pressure state occurs.

For example, in a rock drill (drifter), a shank rod is disposed in front of a piston, and the piston moves forward and strikes the rear end of the shank rod. An example is shown in FIG.
In the example shown in the figure, a shank rod 160 is disposed in front of the piston 120. An annular front chamber port 104 is formed on the front side inside the cylinder 110, and an integrated front chamber liner 130 made of a copper alloy is fitted to the inner surface of the cylinder 110 in front of the front chamber port 104. ing. In this example, a liquid chamber space filled with hydraulic oil is defined at the rear of the front chamber liner 130, and this liquid chamber space is a cushion chamber 103 communicating with the front chamber 102.

The piston 120 hits the rear end of the shank rod 160 when the hitting efficiency is maximum. When the shank rod 160 is hit by the piston 120, a shock wave generated by the hit is propagated to the bit (not shown) at the tip through the rod on the tip of the shank rod 160 and used as drilling energy.
Here, in the hydraulic striking device of the “front / rear chamber alternate switching system”, in the striking phase, when the front chamber is communicated with the low pressure circuit, when the piston strikes the shank rod, the piston is suddenly braked. At this time, even if the piston is suddenly braked, the hydraulic oil continues to flow out due to inertia, so a negative pressure state occurs in the front chamber. For this reason, when the pressure of the hydraulic oil becomes lower than the saturated vapor pressure for a very short time, a large number of microbubbles, that is, cavitation easily occurs in the hydraulic oil. Then, when the piston moves to the retreating process after the impact, the front chamber is communicated with the high pressure circuit by the switching valve mechanism. Therefore, there is a problem that erosion (erosion) is likely to occur in the front chamber due to the impact pressure when the generated cavitation is compressed and disappears.

  By the way, the present inventor found that the problem of the cavitation erosion in the front chamber is that the front chamber becomes a low pressure when the piston moves forward because the front chamber is switched to a low pressure circuit when the piston moves forward. I thought. That is, in addition to the above-mentioned “front and rear chamber alternate switching method” in which the front chamber becomes low pressure when the piston moves forward, the “front chamber alternate switching method” in which the rear chamber is always connected to high pressure and the front chamber is alternately switched between high pressure and low pressure. (For example, refer to Patent Document 3) has the same problem.

  Therefore, the present invention has been made paying attention to such problems, and in the hydraulic striking device of the type that switches the front chamber to a low pressure circuit when the piston moves forward, the cavitation erosion in the front chamber is effectively prevented. It is an object of the present invention to provide a hydraulic striking device that can prevent or suppress, or minimize problems caused by cavitation erosion.

According to the results of an experimental study by the present inventor, in the hydraulic striking device that switches the front chamber to the low pressure circuit when the piston moves forward, the cavitation erosion when the hydraulic oil pressure drops in the front chamber is The knowledge that it is unevenly distributed on the side farthest in the circumferential direction with respect to the opening of the anterior chamber passage for supplying and discharging the water was obtained.
That is, in order to solve the above-mentioned problem, a hydraulic striking device according to one aspect of the present invention is a hydraulic striking device that strikes a striking rod by moving a piston slidingly fitted in a cylinder back and forth. A front chamber and a rear chamber defined between an outer peripheral surface of the piston and an inner peripheral surface of the cylinder and spaced apart from each other; and switching the front chamber to a low-pressure circuit when the piston moves forward includes forward and a switching valve mechanism for supplying and discharging hydraulic fluid to retract is repeated in, the front chamber has a mated front chamber liner on the inner peripheral surface of the cylinder, of the cylinder The peripheral surface has a front chamber port formed in an annular shape facing the outer peripheral surface on the rear side of the liner for the front chamber, and the height of the hydraulic fluid in the front chamber is communicated with the front chamber port. A high / low pressure switching port for switching low pressure is connected to the front chamber. The liner is extended to a position facing the front chamber port, and a plurality of through holes spaced in the circumferential direction are formed through the surface facing the front chamber port in a radial direction. Features.

According to the hydraulic striking device according to one aspect of the present invention, the front chamber port formed in an annular shape is provided on the inner periphery of the cylinder , and the front chamber passage for switching the high and low pressures to communicate with the front chamber port is connected. and, pre-chamber liner, along with being extended to a position opposed to the front chamber port, the surface facing the front chamber port, a plurality of through holes spaced apart in the circumferential direction is formed through radially Therefore, the plurality of through holes of the front chamber liner serve as a dispersion region for the generated cavitation.

Thus, cavitation generated inside the front chamber liner is dispersed before entering the front chamber port by the plurality of through holes of the front chamber liner. Therefore, even if cavitation occurs, the uneven distribution of cavitation in the portion farthest in the circumferential direction with respect to the opening of the front chamber passage is alleviated. Therefore, it is possible to effectively prevent or suppress intensive erosion in this portion, or to minimize a problem caused by cavitation erosion. Furthermore, because of the extended to the rear of the front chamber port side after the front chamber liner, it can prevent the occurrence of erosion in the cylinder inner diameter sliding surface. Therefore, consumable parts due to erosion can be minimized.

Here, it is preferable that the plurality of through holes have a slot shape (long hole shape) in which the circumferential direction is longer than the axial direction, such as a rectangular shape or an elliptical shape. With such a configuration, the passage area of each through-hole is increased, which is suitable for reducing the occurrence of cavitation by suppressing the flow rate of the hydraulic oil.
The front chamber liner has a split structure that is divided into two axially front and rear at the positions of the rear side edge surfaces of the plurality of through holes, and through holes that are adjacent in the circumferential direction by the split structure. It is preferable that each column part formed between the two is a cantilever. With such a configuration, a surge pressure is generated with the reciprocation of the piston. However, if a plurality of column portions are cantilever beams, a tensile pressure due to the surge pressure does not act on the column portions. Therefore, it is suitable for preventing or suppressing the destruction of the column portion due to the surge pressure.

Here, in the hydraulic striking device, for example, in a rock drill (drifter), a cushion chamber is provided in the front chamber as a braking mechanism in order to prevent the large-diameter portion of the piston from colliding with the cylinder at the piston front stroke end. In the hydraulic striking device according to one aspect of the present invention, the front chamber liner is provided with a liquid chamber space that communicates with the front chamber and is filled with hydraulic oil as a cushion chamber. The plurality of through holes are provided in an inner surface-side annular groove formed on an inner peripheral surface of the front chamber liner, and the cushion chamber has an inner periphery on the inner surface-side annular groove. It is preferable to communicate over the range. With such a configuration, as will be described in detail in the embodiment of the present invention, the cushion effect by the cushion chamber is started at an intended position, and is suitable for preventing a reduction in impact efficiency.

  As described above, according to the present invention, in the hydraulic striking device that switches the front chamber to the low pressure circuit when the piston moves forward, the cavitation erosion in the front chamber is effectively prevented or suppressed, or the problem caused by cavitation erosion. Can be minimized.

It is sectional drawing explaining one Embodiment of the hydraulic striking device which concerns on 1 aspect of this invention, The figure has shown the cross section along an axis line. It is an enlarged view of the principal part (front chamber liner part) of FIG. FIG. 3 is a cross-sectional view of the main part of the liner for the anterior chamber of FIG. 2, in which (a) is a cross-sectional view taken along the line AA in FIG. It is CC sectional drawing. It is a perspective view of the back liner which constitutes the liner for front rooms of Drawing 2, The figure (a) shows the 1st example, (b) shows the 2nd example, and (c) shows the 3rd example. Yes. BRIEF DESCRIPTION OF THE DRAWINGS It is a longitudinal cross-sectional view explaining operation | movement of one Embodiment of the hydraulic striking device which concerns on 1 aspect of this invention, The figure has shown the shank rod part collectively in the example applied to a rock drill. (A) shows the normal striking position, (b) is when the piston is retracted in normal striking, and the upper side of the center line shows the time of deceleration in the backward direction, and the lower side of the center line shows the back of the piston. (C) is the state of forward movement of the shank rod, and the upper side of the center line in the figure shows when the piston enters the cushion chamber, and the lower side of the center line shows when the piston stops. Show. It is a schematic diagram explaining the effect of several through-hole parts formed in the back liner, The figure (a) is an example which does not provide an inner surface side annular groove in several through-hole parts, ) Is a view taken in the direction of arrow D in (a), and FIG. 5B is an example in which inner surface side annular grooves are provided in a plurality of through-hole portions, and FIG. E view is shown. It is a figure which shows the comparative example with respect to the hydraulic-type hammering apparatus which concerns on 1 aspect of this invention, and the figure is a longitudinal cross-sectional view which shows a shank rod part typically in the example of application of a rock drill.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate.
The hydraulic striking device 1 according to the present embodiment is a “front / rear chamber alternating switching” striking device, and as shown in FIG. 1, the piston 20 is a solid cylindrical shaft member having a central axial direction. Large diameter portions 21 and 22 and small diameter portions 23 and 24 formed before and after the large diameter portions 21 and 22. The piston 20 is slidably fitted into the cylinder 10 so that the front chamber 2 and the rear chamber 8 are defined between the outer peripheral surface 20g of the piston 20 and the inner peripheral surface 10n of the cylinder 10, respectively. Has been. The step portion where the large-diameter portion 21 and the small-diameter portion 23 on the front side in the axial direction are connected is a pressure-receiving surface on the front chamber 2 side for applying thrust in the traveling direction of the piston 20, The pressure receiving surface on the front chamber 2 side is a conical surface 26 that decreases in diameter from the large diameter portion 21 side toward the small diameter portion 23 side. On the other hand, the step portion where the large-diameter portion 22 and the small-diameter portion 24 on the rear side in the axial direction are connected is a pressure receiving surface on the rear chamber 8 side, and in this embodiment, the pressure receiving surface on the rear chamber 8 side is large. The end face on the diameter part 22 side is an orthogonal surface 27 orthogonal to the axial direction.

  A control groove 25 is formed between the large diameter portions 21 and 22 by a concave stepped portion. The control groove 25 is connected to the switching valve mechanism 9 via a plurality of control ports. The front chamber 2 and the rear chamber 8 are connected to the switching valve mechanism 9 via the high / low pressure switching ports 5 and 85, respectively. The switching valve mechanism 9 allows hydraulic oil to be supplied and discharged at a desired timing, so that the front chamber 2 and the rear chamber 8 are alternately communicated with the high-pressure circuit 91 and the low-pressure circuit 92, respectively, and the pressure receiving surface is made of hydraulic oil. By being pushed in the axial direction by hydraulic pressure, the forward and backward movements of the piston 20 are repeated in the cylinder 10. A front head 6 and a back head 7 corresponding to a striking device such as a rock drill or a breaker are mounted on the front and rear of the cylinder 10, respectively.

  Here, the front chamber 2 has a front chamber liner 30 provided in front of the front chamber 2 and fitted to the cylinder inner peripheral surface 10n. An annular seal retainer 32 is fitted to the cylinder inner peripheral surface 10 n on the front side of the front chamber liner 30. In the seal retainer 32, packing or the like is fitted in a plurality of annular grooves 32a formed at appropriate positions on the inner and outer peripheral surfaces of the seal retainer 32, thereby preventing the hydraulic oil from leaking to the front of the front chamber 2. The rear chamber 8 has a cylindrical rear chamber liner 80 provided behind the rear chamber 8 and fitted to the cylinder inner peripheral surface 10n.

  The rear chamber liner 80 integrally includes a rear chamber defining portion 81, a bearing portion 82, and a seal retainer portion 83 in order from the front in the axial direction. The rear chamber 8 is defined by a cylindrical space on the front inner periphery of the rear chamber defining portion 81, a liquid chamber space between the inner peripheral surface of the cylinder 10 and the outer peripheral surface of the small diameter portion of the piston 20. A rear chamber passage 85 is connected to the inner peripheral surface of the cylinder 10 that defines the rear chamber 8. The bearing portion 82 is in sliding contact with the outer peripheral surface of the small-diameter portion on the rear side of the piston 20 and pivotally supports the rear portion of the piston 20. On the inner peripheral surface of the bearing portion 82, a plurality of annular oil grooves 82a are separated in the axial direction to form a labyrinth. In the seal retainer portion 83, packing or the like is fitted into a plurality of annular grooves 83a formed at appropriate positions on the inner and outer peripheral surfaces thereof to prevent the hydraulic oil from leaking to the rear of the rear chamber 8. A drain communication hole 84 is formed in the radial direction between the bearing portion 82 and the seal retainer 83, and the communication hole 84 is connected to a rear chamber low pressure port (not shown).

  The front chamber liner 30 is composed of a pair of front liner 40 and rear liner 50 in the axial direction. That is, in the present embodiment, the front chamber liner 30 is divided by the separate liners on the front side and the rear side in the axial direction. In the present embodiment, the front liner 40 is not provided with a liquid chamber, the liquid liner space is provided only in the rear liner 50, and the liquid chamber space formed in communication with the front chamber 2 at the rear portion of the rear liner 50. Is the cushion chamber 3. In order to prevent the large-diameter portion 21 of the piston 20 from colliding with the cylinder 10 at the stroke front end of the piston, the cushion chamber 3 has a liquid chamber as a closed space when the large-diameter portion 21 of the piston 20 intrudes. 20 movements are restricted.

  Specifically, the front liner 40 is made of a copper alloy, and has a flange portion 41 that protrudes in an annular shape toward the radially outer side at the front end portion, as shown in an enlarged view in FIG. The rear portion is also a cylindrical bearing portion 42. A drain port 45 having an annular shape is formed between the outer periphery of the flange portion 41 and the inner peripheral surface of the cylinder 10, and the drain port 45 is connected to a drain passage 49.

  The front liner 40 has an outer circumferential surface of the small-diameter portion 23 of the piston 20 having a facing gap narrower than a predetermined facing gap (clearance between the outer diameter of the piston 20 and the inner diameter of the liner) of the small-diameter portion 54 on the inner periphery of the front end side of the rear liner 50. It is in sliding contact with 23g. A plurality of annular oil grooves 40m are separated in the axial direction on the sliding contact surface 40n on the inner periphery of the front liner 40 to form a labyrinth. The front liner 40 is not provided with a liquid chamber space other than the oil groove 40m, and serves as a bearing for slidingly supporting the piston 20.

The rear end surface 42t of the front liner 40 is in contact with the front end surface 50t of the rear liner 50, and a plurality of first end surface grooves 46 are provided on the rear end surface 42t of the front liner 40 so as to be spaced apart from each other in the circumferential direction. A passage is formed along the radial direction. In this example, the plurality of first end face grooves 46 are spaced apart in the circumferential direction and equally distributed at four locations (see FIG. 3B).
Further, in the front liner 40, a plurality of slits 48 are formed as axial communication paths along the axial direction on the outer peripheral surface 42g of the cylindrical bearing portion 42 in accordance with the formation position of the first end surface groove 46. ing. In this example, the plurality of slits 48 are equally arranged at four locations in accordance with the position of the first end face groove 46 (see FIG. 3A). Further, a plurality of second end face grooves 47 are formed as radial communication paths along the radial direction on the surface of the front liner 40 facing the rear side of the collar portion 41 in accordance with the positions of the plurality of slits 48. .

  The plurality of second end surface grooves 47 communicate with the drain port 45 provided on the outer periphery of the flange portion 41 of the front liner 40. Accordingly, the hydraulic oil in the cushion chamber 3 of the rear liner 50 is passed through the predetermined gap of the small diameter portion 54 on the front end side of the rear liner 50, and further, “first end surface groove 46 to slit 48 to second end surface groove 47 to It is possible to escape to the drain passage 49 through the drain port 45 ". In other words, this circuit functions as a “drain circuit”. In addition, the drain circuit of pressure oil (hereinafter referred to as “first drain circuit”) passing through the liner bearing portion (opposite clearance in the inner and outer diameter direction between the small diameter portion 23 of the piston 20 and the sliding contact surface 40 n on the inner periphery of the front liner 40). This circuit can be referred to as a “second drain circuit”.

In the communication hole including “first end face groove 46 to slit 48 to second end face groove 47”, the passage areas of the first end face groove 46, the slit 48, and the second end face groove 47 are set to substantially equal areas. . And although the four communicating holes of this embodiment are formed, "the total passage area of the communicating holes" which totaled the passage areas of these plural communicating holes is with respect to "the clearance amount of the liner bearing part" It is set to an area within a predetermined range defined in the following (Equation 1), whereby the leak amount of the pressure oil from the “drain circuit” is limited to a predetermined amount. Here, “the clearance amount of the liner bearing portion” is an area of an annular clearance formed by a facing clearance in the inner and outer diameter direction between the small diameter portion 23 of the piston 20 and the sliding contact surface 40 n on the inner periphery of the front liner 40. is there.
0.1 Apf <A <2.5 Apf (Formula 1)
Apf: Liner bearing clearance
A: Total passage area of communication hole

  The rear liner 50 is made of an alloy having higher mechanical strength than the front liner 40 made of the copper alloy. In this embodiment, the mechanical strength of the alloy steel is improved by heat treatment of the alloy steel. For example, carburizing, quenching, and tempering can be performed on the case-hardened steel to form a hardened layer on the surface. The rear liner 50 has a cylindrical shape, and the outer diameter of the cylindrical shape is the same as the outer diameter of the bearing portion 42 of the front liner 40. The inner diameter of the rear liner 50 is such that the inner diameter of the inner peripheral portion 50n on the rear end side is a slidable contact surface with a slight gap from the large diameter portion 21 of the piston 20. On the other hand, the size of the small-diameter portion 54 on the inner periphery of the front end side of the rear liner 50 is larger than the inner diameter of the sliding contact surface 40n on the inner periphery of the front liner 40, and the liner bearing described above with respect to the outer peripheral surface of the piston 20 A predetermined facing gap larger than the clearance of the part is separated.

An annular front chamber port 4 is formed between the outer peripheral surface 50g on the rear side of the rear liner 50 and the inner peripheral surface of the cylinder 10, and the front chamber for switching the high and low pressures of the front chamber 2 to the front chamber port 4 is formed. A passage 5 is connected. In other words, the rear liner 50 of the present embodiment has the extending portion 55 that extends rearward from the front chamber port 4.
In the present embodiment, the rear liner 50 is formed with an outer surface-side annular groove 56 on the outer peripheral surface of the extending portion 55 at a position facing the front chamber port 4, and the inner periphery of the extending portion 55. An inner surface side annular groove 57 is formed on the surface. A plurality of circumferentially spaced through holes 58 are formed in the inner and outer annular grooves 56 and 57 in the radial direction. The plurality of through holes 58 are preferably equally distributed in the circumferential direction (in the example shown in FIG. 3C, the through holes 58 are equally distributed at 16 locations). The shape of the plurality of through-holes 58 is not particularly limited. For example, as shown in FIG. 4 (a) or a rectangle (the corner is R-shaped) or an ellipse, as shown in FIG. 4 (b). Can do. If the through hole 58 has a “slot shape” that is longer in the circumferential direction than the axial direction, such as a rectangle or an ellipse, the passage area of each through hole 58 is enlarged, so that the flow rate of hydraulic oil is suppressed. This is preferable for reducing the occurrence of cavitation.

  As shown in FIG. 4C, the rear liner 50 can be further divided. In the example shown in the figure, a split structure is formed at the position of the rear side edge surface of the through hole 58 having the “slot shape (long hole shape)” shown in FIG. 63 and the rear liner (rear) 64 constitute a rear liner 50. By dividing the rear liner 50 into two parts at this position, the column part 62 formed between the through holes 58 adjacent in the circumferential direction extends from the rear end of the rear liner (front) 63 toward the rear. It is a beam.

  Further, as shown in FIG. 2, the cushion chamber 3 is formed on the inner peripheral surface on the rear side of the rear liner 50. In the present embodiment, the cushion chamber 3 includes a first annular part 51 on the rear side in the axial direction and a second annular part 52 formed in front of the first annular part 51. A portion where the first annular portion 51 and the second annular portion 52 are connected is a conical surface 59 whose diameter increases from the first annular portion 51 side toward the second annular portion 52 side.

  The first annular portion 51 communicates with the inner surface side annular groove 57 over the entire circumference at the rear in the axial direction. The first annular portion 51 has a diameter (small diameter) shallower than the depth (inner diameter) of the inner surface side annular groove 57, and the rear side thereof is formed adjacent to the front side of the inner surface side annular groove 57. . The second annular portion 52 has a larger diameter than the first annular portion 51, and the rear of the second annular portion 52 is formed adjacent to the front of the first annular portion 51. An end surface on the front side that forms the second annular portion 52 is an orthogonal surface 53 that is orthogonal to the axial direction.

  Next, the operation, action and effect of the hydraulic striking device 1 will be described. Here, as an example in which the hydraulic striking device 1 of the present embodiment is applied to a rock drill, it will be described with reference to FIG. 5 as appropriate. As shown in FIG. 5A, the rock drill has a shank rod 60 in front of the piston 20 of the hydraulic striking device 1. The shank rod 60 has a spline 61 formed at the rear, and is supported by the front cover 70 so as to be slidable in the axial direction within a predetermined range. The shank rod 60 is restricted in its rearward movement limit by a damper mechanism (not shown). Further, the rock drill includes a feed mechanism and a rotation mechanism (not shown), and the shank rod 60 can be rotated by a rotation mechanism meshing with the spline 61, and the cylinder 10 side of the hydraulic striking device 1 is a feed mechanism. Is fed according to the amount of crushing.

  The normal striking is performed when the striking efficiency of the piston 20 is maximum in the rearward movement limit of the shank rod 60 shown in FIG. When the shank rod 60 is hit by the piston 20, a shock wave generated by the hit is propagated from the shank rod 60 to the bit at the tip (not shown) through the rod, and the bit is used as energy for crushing the rock mass. The cylinder 10 side is fed according to the amount of crushing by a feed mechanism (not shown). When hydraulic oil is supplied and discharged at the expected timing by the switching valve mechanism 9 of the hydraulic striking device 1, the piston 20 is retracted in the cylinder 10 as shown in FIG. Is then decelerated at a predetermined position in the backward direction shown on the upper side of the center line, and then, as shown on the lower side of the center line, the piston 20 starts moving again in the forward direction at the rear dead center.

  Here, in the hydraulic striking device 1, when hydraulic oil is supplied and discharged at a predetermined timing by the switching valve mechanism 9, the front chamber 2 and the rear chamber 8 are connected to the high and low pressure switching ports 5 and 85, respectively. Thus, the high pressure circuit 91 and the low pressure circuit 92 are alternately communicated, whereby the piston 20 is repeatedly advanced and retracted in the cylinder 10. That is, in the hydraulic striking device 1, the hydraulic oil on the front chamber 2 side does not resist the movement of the piston in the striking direction due to the “front / rear chamber alternating switching system” striking. Therefore, it is suitable for improving the hitting efficiency.

  However, in this type of “front and rear chamber alternate switching type” hydraulic striking device, cavitation tends to occur if a negative pressure state occurs in the hydraulic fluid due to a rapid pressure fluctuation in the front chamber. In particular, according to the results of experimental research by the present inventor, in the hydraulic striking device of the “front and rear chamber alternate switching system”, cavitation erosion in the front chamber is caused by a high and low pressure switching port that supplies and discharges hydraulic oil from the front chamber. It was confirmed that the occurrence was unevenly distributed on the farthest side in the circumferential direction with respect to the opening.

  On the other hand, according to the hydraulic striking device 1 of the present embodiment, the front chamber port 4 formed in an annular shape is provided on the inner surface of the cylinder 10, and before the high and low pressures are switched so as to communicate with the front chamber port 4. The rear liner 50 connected to the chamber passage 5 and constituting the front chamber liner 30 extends to a position facing the front chamber port 4 and is spaced circumferentially on a surface facing the front chamber port 4. Since the plurality of through holes 58 are penetrated in the radial direction, the plurality of through holes 58 serve as a dispersion region of the generated cavitation.

  Thus, cavitation generated inside the rear liner 50 constituting the front chamber liner 30 is dispersed before entering the front chamber port 4 by the plurality of through holes 58. For this reason, even if cavitation occurs, uneven distribution of cavitation in a portion farthest in the circumferential direction with respect to the opening of the front chamber passage 5 is alleviated. Therefore, it is possible to effectively prevent or suppress intensive erosion in this portion, or to minimize a problem caused by cavitation erosion. Furthermore, since the rear side of the rear liner 50 extends to the rear of the front chamber port 4, it is possible to prevent the occurrence of erosion on the cylinder inner diameter sliding surface. Therefore, consumable parts due to erosion can be minimized.

Further, since the plurality of through holes 58 have a slot shape such as a rectangle or an ellipse that is longer in the circumferential direction than the axial direction, the flow area of the hydraulic oil is increased by increasing the passage area of each through hole 58. The occurrence of cavitation can be reduced by suppressing the occurrence of cavitation.
Here, it is preferable that the plurality of column portions 62 formed between the through holes 58 adjacent in the circumferential direction are cantilever beams. In this case, as in the third embodiment shown in FIG. 4C, the rear liner 50 is divided by dividing the rear liner 50 at the position of the rear side edge surface of the through hole 58 having a “slot shape”. It is preferable that the rear liner 50 is composed of 63 and the rear liner (rear) 64.

  That is, when a surge pressure is generated as the piston 20 reciprocates, the surge pressure generated in the case of a double-supported column as shown in FIG. 4B is a tensile pressure in the front-rear direction with respect to the column. Works. Therefore, when erosion progresses in the column portion, the column portion may not withstand the tensile pressure and may be broken. On the other hand, as shown in FIG. 4C, if the plurality of column parts 62 are cantilever beams, tensile pressure due to surge pressure does not act on the column parts 62. Therefore, destruction of the column part 62 due to surge pressure can be prevented or suppressed.

Here, as shown in FIG. 5 (c), if the bit does not normally land in the drill hole due to entering the hollow band, the shank rod 60 moves forward from the normal striking position. A "shank rod advance state" occurs. At this time, in order to prevent the large-diameter portion 21 of the piston 20 from colliding with the cylinder 10 at the piston front stroke end, the cushion chamber 3 communicating with the front chamber 2 is provided. As shown in the upper side of the center line in FIG. 3C, the cushion chamber 3 restricts the movement of the piston by closing the liquid chamber when the large diameter portion 21 of the piston 20 enters the cushion chamber 3. As a result, as shown on the lower side of the center line in FIG. 5C, the end of the large diameter portion 21 of the piston 20 (the position of the conical surface 26) stays in the cushion chamber 3, so The large diameter portion 21 of the piston 20 can be prevented from colliding with the cylinder 10.

The plurality of through-holes 58 are provided in an inner surface side annular groove 57 formed on the inner peripheral surface of the rear liner 50, and the cushion chamber 3 has an axially rear side in the inner surface side annular groove 57. Since it communicates over the entire circumference, the cushioning effect by the cushion chamber 3 can be started at a desired position, and a reduction in impact efficiency can be prevented.
That is, as shown in FIG. 6A, if the inner surface side annular groove 57 is not provided in the plurality of through-holes 58, the large-diameter portion 21 of the piston 20 is directly connected to the through-hole 58. It will pass in sliding contact. Therefore, when the large-diameter portion 21 of the piston 20 passes through the portion of the through hole 58, the change in the pressure oil outflow passage area toward the low pressure side (the front chamber port 4 side) as shown in FIG. (The two-dot chain line in the figure shows an image of the process in which the large-diameter end ridge line passes). Therefore, the cushioning action is generated from the stage before entering the cushion chamber 3, and the impact efficiency is lowered.

  On the other hand, as shown in FIG. 5B, when the inner surface side annular groove 57 is provided as in the present embodiment, when the large diameter portion 21 of the piston 20 passes through the portion of the through hole 58, By passing through the inner surface side annular groove 57, the rate of change of the pressure oil outflow passage area to the low pressure side can be made constant as shown in FIG. . Therefore, the occurrence of the cushioning action at the stage before entering the cushion chamber 3 is prevented, and from the intended position, that is, from the rear end position of the first annular portion 51 following the front end portion of the inner surface side annular groove 57. The desired cushion effect can be started.

  Further, according to the hydraulic striking device 1 of the present embodiment, the cushion chamber 3 is formed adjacent to the first annular portion 51 on the rear end side and the front of the first annular portion 51. Since it has the 2nd annular part 52 larger in diameter than the 1 annular part 51, the pressure reduction of hydraulic fluid can be relieved by the volume expansion by the 2nd annular part 52 provided in the front side of the 1st annular part 51. Therefore, the occurrence of cavitation in the front chamber 2 can be suppressed. Moreover, even if cavitation occurs, it is possible to suppress rupture and erosion.

  Further, since the front end surface forming the second annular portion 52 of the cushion chamber 3 is an orthogonal surface 53 orthogonal to the axial direction, cavitation is temporarily generated in the cushion chamber 3 and reaches erosion. However, the cavitation toward the front liner 40 side having a bearing function may be fastened to the second annular portion 52 of the cushion chamber 3 by the orthogonal surface 53, and erosion may be generated at a location that does not affect the sliding with the piston. it can. For this reason, it is possible to minimize a problem caused by cavitation erosion and to prevent an impossibility of hitting immediately.

  Here, by providing the cushion chamber 3, the collision between the large diameter portion 21 of the piston 20 and the cylinder 10 at the front stroke end of the piston in the “shank rod advance state” is prevented, while the pressure in the cushion chamber 3 is reduced. Since the oil is rapidly compressed and becomes an ultra-high pressure state, the oil temperature of the hydraulic oil rises in the front chamber 2 and the cushion chamber 3. Furthermore, when the inside of the cushion chamber 3 becomes an ultra-high pressure, the flow rate of the pressure oil to the front chamber 2 side becomes excessive. For this reason, due to the fast flow of hydraulic fluid flowing from the cushion chamber 3 into the front chamber 2, local cavitation is generated and the hydraulic oil further rises in temperature due to compression. Therefore, there is a concern that the copper alloy portion of the front chamber liner 30 expands and the piston 20 “gaps”. Furthermore, since the gap between the piston 20 and the front chamber liner 30 is reduced, the drain function is lowered and discharge of high-temperature pressure oil is suppressed, so that the temperature rise is accelerated.

  On the other hand, according to the hydraulic striking device 1 of the present embodiment, the front chamber liner 30 has a first end surface groove at a portion in front of the cushion chamber 3 in the rear liner 50 constituting the front chamber liner 30. 46, and the passage composed of “first end face groove 46 to slit 48 to second end face groove 47” is always in communication with a drain passage 49 that is a low-pressure circuit. Function as. That is, when the hydraulic oil temperature rises in the front chamber 2 as in the “shank rod advance state”, the hydraulic oil in the cushion chamber 3 can be released from the “second drain circuit”.

  Thereby, compared with the case where the “second drain circuit” is not provided, the compression in the cushion chamber 3 and the front chamber 2 is relieved, so that the oil temperature rise of the hydraulic oil is also suppressed. Furthermore, since the flow rate of the hydraulic oil flowing into the front chamber 2 is reduced, the occurrence of local cavitation is suppressed. Next, although the front chamber 2 is switched to a high pressure by the switching valve mechanism 9, since the local cavitation is suppressed, the heat generation due to the compression of the cavitation is mitigated, so that the rise in the hydraulic oil temperature can be drastically reduced. it can. Therefore, the expansion of the copper alloy portion of the front chamber liner 30 (in this embodiment, the front liner 40 constituting the front chamber liner 30) associated therewith is also relieved, so that the sliding contact location with the front chamber liner 30 is reduced. This also prevents or suppresses the problem of the occurrence of “galling” of the piston 20. The passage area due to the “first drain circuit” rapidly decreases due to the expansion due to the temperature rise, whereas the passage area due to the “second drain circuit” is hardly affected by the temperature rise.

  Further, paying attention to the piston operation when the piston 20 moves forward to the front end of the stroke in the cushion chamber 3 and stops, the pressure oil supplied to the front chamber 2 by valve switching is larger than the inner diameter of the rear liner 50 and the piston 20. The piston 20 is supplied into the cushion chamber 3 from the gap of the diameter portion 21 and turns backward. At this time, a part of the pressure oil is discharged from the “second drain circuit”. The pressure rise is moderate. Accordingly, the retreat speed of the piston 20 is slowed, and the number of hits per hour in the “shank rod advance state” is reduced, so that the oil temperature rise in the front chamber 2 is alleviated.

  Furthermore, according to the hydraulic striking device 1 of the present embodiment, the front chamber liner 30 is constituted by a front liner 40 and a rear liner 50 that are divided into two in the axial direction, and the front liner 40 is made of a copper alloy. Thus, a liquid chamber space other than the oil groove 40m is not provided to provide a bearing member that supports the sliding of the piston 20, and the rear liner 50 is made of an alloy steel having a hardened layer formed on the surface thereof. Since the fluid chamber space that is communicated and filled with hydraulic oil is provided as the cushion chamber 3, the cavitation erosion is supported by the rear liner 50 made of a high hardness alloy steel, and the bearing that slides and supports the piston 20. With respect to the function, the front liner 40 made of copper alloy without providing the liquid chamber space can be used. Therefore, while maintaining the piston sliding support function as a necessary bearing on the front chamber 2 side with the front liner 40, the rear liner 50 is caused by cavitation erosion against the impact pressure due to the disappearance of cavitation in the front chamber 2. The trouble can be minimized.

  As described above, according to this hydraulic striking device, it is possible to effectively prevent or suppress cavitation erosion in the front chamber, or to minimize problems caused by cavitation erosion. 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, the hydraulic striking device 1 of the above embodiment has been described by taking the “front / rear chamber alternate switching system” striking device as an example. However, the present invention is not limited to this, and the present invention switches the front chamber to the low pressure circuit when the piston moves forward. It can be applied to the hydraulic striking device.
For example, the present invention can also be applied to a “front chamber alternate switching type” striking device as disclosed in Patent Document 3. In other words, in the “front chamber alternate switching type” striking device, the rear chamber is always communicated with the high pressure circuit, while the front chamber is alternately communicated with the high pressure circuit and the low pressure circuit by the switching valve mechanism. When the front chamber communicates with the high-pressure circuit, the front and rear pressure receiving areas are made different so that the piston moves in the backward direction, whereby the forward and backward movement of the piston is repeated in the cylinder. Therefore, since the front chamber is switched to the low pressure circuit when the piston moves forward, problems such as cavitation erosion in the front chamber are caused by the same mechanism of action, and therefore the present invention can be applied.

Further, for example, in the above embodiment, the front chamber liner 30 has been described in example constructed from a rear liner 50. liner 40 prior to halving the longitudinal axial direction, is not limited to this, the comparative example of FIG. 7 The front chamber liner 30 may be constituted by a monolithic liner, as shown by the reference numeral 130 shown.
However, while maintaining the piston sliding support function as a necessary bearing on the front chamber 2 side with the front liner 40, the rear liner 50 effectively counters the impact pressure due to the disappearance of cavitation in the front chamber 2 and effectively prevents erosion. In order to minimize the problems caused by prevention or suppression or cavitation erosion, the front chamber liner 30 is composed of a front liner 40 and a rear liner 50 which are divided into two in the axial direction as in the above embodiment. It is preferable. In the case where the front liner 40 and the rear liner 50 are divided into two parts, if the rear liner 50 is made of an alloy having higher mechanical strength than the front liner 40, various materials and surface hardening treatments can be adopted. It is.

Further, for example, in the above embodiment, the cushion chamber 3 is configured from the first annular portion 51 and the second annular portion 52 having a larger diameter than the first annular portion 51 with respect to the liquid chamber shape and volume of the cushion chamber 3, Although the example in which the front end surface forming the second annular portion 52 is the orthogonal surface 53 orthogonal to the axial direction has been described, the present invention is not limited to this, and the liquid chamber shape of the cushion chamber 3 is, for example, illustrated in FIG. As shown in the reference numeral 103 shown in the comparative example of FIG.

  However, in order to effectively prevent or suppress cavitation in the front chamber 2 or minimize problems caused by cavitation erosion, the cushion chamber 3 includes the first annular portion 51 and the first annular portion. It is preferable that the second annular portion 52 having a large volume provided on the front side of 51 is provided. Further, in order to more suitably suppress cavitation toward the front liner 40 having a bearing function, the front end surface forming the second annular portion 52 is preferably an orthogonal surface 53 orthogonal to the axial direction. .

  Further, in the above-described embodiment, for example, as the “second drain circuit”, the front liner is formed as a plurality of communication holes that are formed in the front side of the cushion chamber 3 so as to penetrate in the radial direction and are spaced apart in the circumferential direction. A first end surface groove 46 is formed at the boundary between the rear liner 50 and the rear liner 50, and a plurality of communication holes including "first end surface groove 46 to slit 48 to second end surface groove 47" are always communicated with the low-pressure circuit. However, the present invention is not limited to this, and a configuration in which such a plurality of communication holes are not provided may be employed.

  However, in order to suppress an increase in oil temperature during the “shank rod advance state”, the liner bearing portion (a gap between the small diameter portion 23 of the piston 20 and the sliding contact surface 40n on the inner periphery of the front liner 40 in the inner and outer diameter directions). It is preferable to have a “second drain circuit” that is formed separately from the “first drain circuit” of the pressure oil passing through and communicates with the cushion chamber 3. Further, when the “second drain circuit” is formed, a plurality of radial communication passages that are formed in the radial direction and spaced apart in the circumferential direction are provided in front of the cushion chamber 3. It is preferable to configure the “second drain circuit” so that the radial communication path is always in communication with the low-pressure circuit. In the case where the front chamber liner 30 is composed of a front liner 40 and a rear liner 50 that are divided into two parts, the boundary between the front liner 40 and the rear liner 50 is formed like the plurality of first end face grooves 46. It is preferable to form a plurality of radial communication paths.

DESCRIPTION OF SYMBOLS 1 Hydraulic type impact device 2 Front chamber 3 Cushion chamber 4 Front chamber port 5 Front chamber passage 6 Front head 7 Back head 8 Rear chamber 9 Switching valve mechanism 10 Cylinder 20 Piston 21, 22 Large diameter portion 23, 24 Small diameter portion 25 For control Groove portion 26 Conical surface 27 Orthogonal surface 30 Front chamber liner 32 Seal retainer 40 Front liner 41 Brim portion 42 Bearing portion 45 Drain port 46 First end surface groove (first radial communication path)
47 Second end face groove (second radial communication path)
48 Slit (Axial communication path)
49 Drain passage 50 Rear liner 51 First annular portion 52 Second annular portion 53 Orthogonal surface 54 Small-diameter portion 55 Extension portion 56 Outer surface side annular groove 57 Inner surface side annular groove 58 Through hole 59 Conical surface 62 Column portion 63 Rear liner (front)
64 Rear liner (rear)
80 Rear chamber liner 81 Rear chamber defining portion 82 Bearing portion 83 Seal retainer portion 84 Drain communication hole 85 Rear chamber passage 91 High pressure circuit 92 Low pressure circuit

Claims (4)

A hydraulic striking device for striking a striking rod by advancing the piston fitted in the cylinder back and forth,
A front chamber and a rear chamber defined between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder and spaced apart from each other; and when the piston moves forward, the front chamber is switched to a low pressure circuit. A switching valve mechanism for supplying and discharging hydraulic oil so that the forward and backward movements are repeated,
The front chamber has a front chamber liner fitted to the inner peripheral surface of the cylinder,
An inner peripheral surface of the cylinder has a front chamber port formed in an annular shape so as to face an outer peripheral surface on the rear side of the liner for the front chamber, and the front chamber port is communicated with the front chamber port. A high / low pressure switching port for switching the high / low pressure of hydraulic oil is connected,
The front chamber liner is extended to a position facing the front chamber port, and a plurality of through holes spaced in the circumferential direction are formed through the surface facing the front chamber port in a radial direction. A hydraulic striking device characterized by that.   2. The hydraulic striking device according to claim 1, wherein the plurality of through holes have a slot shape in which a circumferential direction is longer than an axial direction. The liner for the front chamber has a divided structure that is divided into two axially front and rear at the position of the rear side edge surface of the plurality of through holes, and between the through holes adjacent in the circumferential direction by the divided structure. The hydraulic striking device according to claim 1, wherein each of the pillar portions formed in is formed as a cantilever beam. The front chamber liner is provided with a liquid chamber space that is communicated with the front chamber and filled with hydraulic oil as a cushion chamber,
The plurality of through holes are provided in an inner surface-side annular groove formed on the inner peripheral surface of the front chamber liner, and the cushion chamber has an axially rearward inner surface-side annular groove extending over the entire circumference. The hydraulic striking device according to any one of claims 1 to 3, wherein the hydraulic striking device is in communication.

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