Hydraulic impact device

Abstract

To provide a hydraulic impact device that can simultaneously implement both a dry-fire prevention mode and a stroke adjustment mode at a low cost. [Solution] The piston 120 is a solid cylindrical body and has a front large-diameter portion 122 and a rear large-diameter portion 124. A medium-diameter portion 121 is provided in front of the front large-diameter portion 122, and a small-diameter portion 125 is provided behind the rear large-diameter portion 124. In addition, an annular groove 126 is provided between the front large-diameter portion 122 and the front edge portion 123 of the rear large-diameter portion, and a flow rate adjustment groove 127 is provided in the rear large-diameter portion 124. In other words, the rear large-diameter portion 124 is divided into the front edge portion 123 and the other portion by the flow rate adjustment groove 127. In the cylinder 100, a second control valve communication port 105, a first control valve communication port 107, a first low-pressure port 108, and a second low-pressure port 109 are provided between the front chamber port 103 and the rear chamber port 104, at positions spaced apart from each other in the axial direction, from the front.

Description

Technical Field

[0004] , ,

[0001] The present invention relates to a hydraulic impact device such as a rock drill or a breaker, and more particularly to a hydraulic impact device provided with an anti-dry-fire mechanism that stops its operation when a piston advances beyond a predetermined impact position.

Background Art

[0002] In this type of hydraulic impact device, a piston strikes a rod and transmits the impact energy to a crushing target to crush it. In a hydraulic impact device, generally, in a ground excavation operation, crushing by impact is continuously performed, whereas in a small-scale crushing operation, when a crushing target is crushed by impact, "dry fire" occurs where the piston strikes the rod instantaneously in a state where the contact between the rod and the crushing target is insufficient.

[0003] Since dry fire imposes a large load on the rod and the hydraulic impact device body, various so-called "anti-dry-fire mechanisms" (also referred to as "auto-stop mechanisms") have been proposed for the purpose of protecting the hydraulic impact device from the impact during dry fire. In the anti-dry-fire mechanism, in a dry-fire state, the rod advances beyond the normal impact position, so when the piston advances a predetermined distance beyond the normal impact position, the operation of the hydraulic impact device is forcibly stopped.

[0004] The applicant of the present application has already proposed the technology shown in FIGS. 8 to 10 as a hydraulic impact device provided with an anti-dry-fire mechanism. That is, a cylinder 500, and a piston 520 that is slidably fitted to the cylinder 500 so as to be able to move back and forth, and has a front large-diameter portion 521 and a rear large-diameter portion 522 provided with an annular groove 525, a middle-diameter portion 523 in front of the front large-diameter portion 521, and a small-diameter portion 524 behind the rear large-diameter portion 522. The cylinder 500 defines a piston front chamber 501 between the middle-diameter portion 523 and the front of the front large-diameter portion 521, and a piston rear chamber 502 between the small-diameter portion 524 and the rear of the rear large-diameter portion 522. Between the piston front chamber 501 and the piston rear chamber 502, a second control valve communication port 505, a first control valve communication port 506, and a low-pressure port are provided in this order from the front to the rear.

[0005] The hydraulic impact device includes a first control valve 600 that controls the forward and backward movement of the piston 520, a stroke adjustment mechanism that adjusts the stroke of the piston 520 between long stroke and short stroke, and a high-pressure circuit that activates the rear chamber 502 of the piston when the piston 520 moves forward a predetermined distance beyond the impact position. 5 The system includes a dry-fire prevention mechanism connected to 10 that advances the piston 520 to its front dead center and stops operation, and a second control valve 700 that selects either a stroke adjustment mechanism or a dry-fire prevention mechanism mode.

[0006] The second control valve communication port 505 communicates with the second control valve 700 via the communication passage 515, communicates with the piston front chamber 501 when the piston 520 retracts, and communicates with the first control valve communication port 506 via the annular groove 525 when the piston 520 advances. The low-pressure port 507 is formed in two locations, specifically, a first low-pressure port 508 that opens at a position where the annular groove 525 connects the first control valve communication port 506 and the low-pressure circuit 111 when the piston 520 is switched from the forward stroke to the reverse stroke, and a second low-pressure port 509 that opens at a position axially rearward of the first low-pressure port 508 and is separated from the piston rear chamber 502 by the rear large-diameter portion 522 when the piston 520 has advanced to its forward dead center.

[0007] A first throttle 530 is provided at the first low-pressure port 508, and a second throttle 531 is provided at the second low-pressure port 509, and the flow rate through the second low-pressure port 509 is adjusted to be smaller than the flow rate through the first low-pressure port 508. Furthermore, when the piston 520 stops at the front dead center, a drain groove 540 is provided in the rear large-diameter portion 522 that connects the first control valve communication port 506 and the first low-pressure port 508 with drain flow rate, and a drain slit 541 is provided in the cylinder 500 that connects the piston rear chamber 502 and the second low-pressure port 509 with drain flow rate (Patent Document 1).

[0008] The basic configuration shown in Figure 8 is a hydraulic impact device with a constantly high-pressure connection in the front chamber and a high / low-pressure switching mechanism in the rear chamber. The explanation of its operating mechanism is omitted. The second control valve 700 is equipped with a high-pressure port, a cylinder communication port, and a stroke adjustment port. By selectively opening / closing these ports with the spool, the operating state of the hydraulic impact device changes as shown in Table 1.

[0009] [Table 1] In other words, the second control valve 700 functions as a switching means that constitutes the dry-fire prevention mechanism and the stroke adjustment mechanism.

[0010] (Anti-dry firing mode) As shown in Table 1, when the high-pressure port 706 of the second control valve 700 and the cylinder communication port 704 are connected via a spool, the hydraulic impact device operates in dry-fire prevention mode. That is, when the piston 520 moves forward a predetermined distance beyond the impact position, the second control valve communication port 505 and the first control valve communication port 506 are connected by the annular groove 525, Valve control port 620 Valve 601, which was connected to high voltage and switched to the reverse position, is switched to the forward position.

[0011] When the hollow passage 624 and the rear chamber port 616 are connected, the piston rear chamber 502 is connected to high pressure, and the piston 520 is subjected to the sum of the forward thrust due to the difference in pressure-receiving area between the piston front chamber 501 and the piston rear chamber 502 and the forward thrust due to the backhead gas pressure, causing the piston 520 to stop at the front dead center and preventing dry firing.

[0012] (Stroke adjustment mode) As shown in Table 1, when the cylinder communication port 704 and stroke adjustment port 705 of the second control valve 700 are connected via a spool, the piston stroke becomes short, and when these ports are blocked, the piston stroke becomes long, and the hydraulic impact device operates in stroke adjustment mode. The mechanism for switching between short and long piston strokes is well known technology, so its explanation is omitted here.

[0013] Figure 8 shows a hydraulic impact device set to short stroke in stroke adjustment mode, where the piston 520 has advanced a predetermined distance beyond the impact position. Valve control port 620 The valve is turned to retraction when the low-pressure connection is made, and the piston rear chamber 502 is turned to low-pressure connection, but the piston 520 continues to move forward due to inertia and reaches the front dead center.

[0014] At the front dead center, the piston 520 is subjected to both a retraction thrust generated in the piston front chamber 501 and a forward thrust due to the backhead gas pressure. Since the retraction thrust exceeds the forward thrust, the piston 520 turns to retract. In other words, the hydraulic striking device allows dry striking in stroke adjustment mode. When applying this hydraulic impact device to a hydraulic breaker, the applicant has taken various measures to achieve a high level of stability in both the dry-firing prevention mechanism and the stroke adjustment mechanism.

[0015] Specifically, the hydraulic impact device is configured with a first low-pressure port 508 and a second low-pressure port 509 as low-pressure ports 507, and is provided with a first throttle 530 and a second throttle 531 to optimally control the flow rate through each port. The piston 520 is equipped with a drain groove 540 that connects the first control valve communication port 506 and the first low-pressure port 508 via drain flow rate, and a drain slit 541 that connects the piston rear chamber 502 and the second low-pressure port 509 via drain flow rate.

[0016] The functions and required flow rates of these configurations are shown in Table 2. [Table 2] The "residual pressure release mechanism" and "recirculation prevention mechanism" in Table 2 are explained in detail in Patent Document 1, so their explanation here will be omitted. [Prior art documents] [Patent Documents]

[0017]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0018] As described above, when the applicant applies this hydraulic impact device to a hydraulic breaker, various configurations are provided aiming to achieve high-level compatibility between the non-striking prevention mechanism and the stability of the stroke adjustment mechanism. However, depending on the configuration, there is a conflict between the non-striking prevention mechanism and the stroke adjustment mechanism, and depending on the configuration, even the same mechanism may be in a conflicting relationship during different operations.

[0019] For example, the drain slit 541 shown in Fig. 9(a) is a groove formed in several places at the appropriate position of the cylinder as shown in the figure. Therefore, there is a limit to the flow rate that can pass through the drain slit 541. As a solution, it is conceivable to expand the drain slit 541 to increase the flow rate that can pass through. However, in the hydraulic impact device disclosed in Patent Document 1, as shown in Fig. (b) of the same figure, when the non-striking prevention mechanism operates, high pressure is supplied into the piston rear chamber 502 to stop the operation of the piston. Therefore, expanding the drain slit 541 causes a pressure drop in the piston rear chamber 502, which causes a malfunction of the non-striking prevention mechanism.

[0020] Also, as shown in Fig. 10(a), while the stroke adjustment mode is set, a closed circuit CC1 is formed among the valve control port 620, the first control valve communication port 506, the second control valve communication port 505, and the second control valve 700. Therefore, when the valve 601 tries to switch from the piston forward position to the piston backward position at the start of work, the drain groove 540 operates as a residual pressure release mechanism, and the hydraulic oil in the valve control port 620 is the first control valve communication port 50 6 flows out from the first low-pressure port 508 through the drain groove 540.

[0021] In order to facilitate the outflow of hydraulic fluid when valve 601 is switched, the drain groove 540 is required to allow a large flow rate to pass through it. However, the hydraulic impact device disclosed in Patent Document 1, as shown in Figure (b), is configured such that while high pressure is acting on the valve control port 620, the valve 601 switches to the piston forward position. That is, the first control valve communication port 50 is the supply path for high pressure to the valve control port 620. 6 When a large flow of hydraulic fluid is discharged from the valve control port, 6 The effective pressure inside 20 decreases, preventing valve 601 from switching to the piston forward position and causing a malfunction of the dry-firing prevention mechanism.

[0022] In other words, the configuration adopted as a countermeasure requires very critical adjustments, and if the same structure is to be installed on a hydraulic impact device with different specifications, a new optimal flow rate setting must be made, which tends to increase design costs. In addition, the drain groove 540 and drain slit 541 in particular require precision machining to achieve the optimal flow rate, which can lead to a decrease in yield and an increase in manufacturing costs.

[0023] This invention has been made in view of these problems, and aims to provide a hydraulic impact device that allows for the stable operation of both mechanisms in a hydraulic impact device in which a dry-fire prevention mechanism can be selected. [Means for solving the problem]

[0024] The present invention relates to a hydraulic striking device comprising a cylinder and a piston slidably fitted into the cylinder so as to be able to move back and forth, having a large diameter portion with an annular groove, a medium diameter portion in front of the large diameter portion, and a small diameter portion behind the large diameter portion, wherein a piston front chamber is defined between the medium diameter portion and the front of the large diameter portion, and a piston rear chamber is defined between the small diameter portion and the rear of the large diameter portion, and a second control valve communication port, a first control valve communication port, and a low-pressure port are provided in this order from front to rear between the piston front chamber and the piston rear chamber, wherein the device comprises a first control valve that controls the forward and backward movement of the piston, a stroke adjustment mechanism that adjusts the stroke of the piston to at least a normal stroke and a short stroke, a dry-fire prevention mechanism that moves the piston forward to the front dead center and stops operation when the piston moves forward a predetermined distance beyond the striking position, and a second control valve that selects a mode for either the stroke adjustment mechanism or the dry-fire prevention mechanism, and the second control valve communication The port communicates with the second control valve via a passage, communicates with the piston front chamber when the piston retracts, communicates with the first control valve communication port by the annular groove when the piston moves past the point of impact to the front dead center, and the low-pressure port is composed of a first low-pressure port that opens at a position to connect the first control valve communication port and the low-pressure circuit by the annular groove provided in the axial center of the large-diameter portion of the piston when the piston is switched from the forward stroke to the retraction stroke, and a second low-pressure port that opens to the piston rear chamber axially rearward from the first low-pressure port when the piston has advanced to the front dead center, and a throttle is provided to adjust the flow rate through the second low-pressure port to be less than the flow rate through the first low-pressure port, and as a dry-fire prevention mechanism, a flow rate adjustment groove is provided in the large-diameter portion that communicates the first control valve communication port and the first low-pressure port and reduces the pressure of the high-pressure circuit to below the operating pressure when the piston has advanced to the front dead center. [Effects of the Invention]

[0025] According to the present invention, it is possible to provide a hydraulic impact device that allows for the selection of a dry-firing prevention mechanism and enables stable operation of both mechanisms simultaneously. [Brief explanation of the drawing]

[0026] [Figure 1] This is a schematic diagram showing the structure of a hydraulic impact device according to one embodiment of the present invention. [Figure 2] Figure 1 is an enlarged view showing the large-diameter portion of the piston and the surrounding structure. [Figure 3] This figure shows the operation of a hydraulic impact device according to one embodiment of the present invention in short-stroke mode. [Figure 4] This figure shows the operation of a hydraulic impact device according to one embodiment of the present invention in the normal stroke mode. [Figure 5] This figure shows the operation at the start of work when a hydraulic impact device according to one embodiment of the present invention is set to the normal stroke mode. [Figure 6] This figure shows the operation of a hydraulic impact device according to one embodiment of the present invention in the dry-fire prevention mode. [Figure 7] This figure shows the operation of a hydraulic impact device according to one embodiment of the present invention in the dry-fire prevention mode. [Figure 8] To clarify the comparison between the present application and the prior art, this figure shows the structure of a hydraulic impact device disclosed in Patent Document 1. [Figure 9] To clarify the comparison between the present application and the prior art, this figure shows the structure of a hydraulic impact device disclosed in Patent Document 1. [Figure 10] To clarify the comparison between the present application and the prior art, this figure shows the structure of a hydraulic impact device disclosed in Patent Document 1. [Modes for carrying out the invention]

[0027] The present invention will be described below with appropriate reference to the drawings. Note that the drawings are schematic. Therefore, it should be noted that the relationship and ratio of thickness and planar dimensions may differ from those in reality, and there may be differences in the dimensional relationships and ratios between drawings. Furthermore, the embodiments shown below are illustrative examples of devices and methods for realizing the technical concept of the present invention, and the technical concept of the present invention is not limited to the following embodiments in terms of the material, shape, structure, arrangement, etc., of the components.

[0028] <Structure> [Overall structure of a hydraulic impact device] Referring to Figure 1, the overall structure of a hydraulic impact device 1 according to one aspect of the present invention will be described. The hydraulic impact device 1 comprises a cylinder 100, a back head 400, a piston 120, and a rod 150, as well as a first control valve 200 and a second control valve 300.

[0029] In the same figure, the piston 120 is shown with the upper half of its centerline at the "front dead center" and the lower half of its centerline at the "rear dead center" when set to the normal stroke mode described later. Furthermore, in this embodiment, "forward" means that the piston 120 moves toward the front dead center, and "reverse" means that the piston 120 moves toward the rear dead center. In addition, the definitions of "forward" and "rear" hereafter are based on the front dead center and rear dead center sides as seen from the piston 120.

[0030] Specifically, a back head 400 is attached to the rear of the cylinder 100. The back head 400 is filled with high-pressure back head gas G. The piston 120 and rod 150 are fitted coaxially and reciprocally along their own axial direction inside the cylinder 100. The first control valve 200 is fixed to one side of the cylinder 100, and a valve 201 is slidably fitted inside it.

[0031] The hydraulic impact device 1 allows the user to select and switch between three operating modes—"dry-firing prevention mode," "normal stroke mode," and "short stroke mode"—by operating the second control valve 300. The normal stroke mode and short stroke mode are "stroke adjustment modes."

[0032] The "dry-firing prevention mode" is an operating mode that, when dry-firing occurs, changes the hydraulic fluid pressure inside the piston front chamber 101 and piston rear chamber 102 to hold the piston 120 in a stopped state. The "Normal Stroke Mode" is a mode that operates in normal stroke mode regardless of the hardness of the rock or whether or not there are dry strokes. Similarly, "Short Stroke Mode" is a mode that operates in short stroke mode regardless of the hardness of the rock or whether or not there are dry strokes.

[0033] [Piston and cylinder structure] The detailed structure of cylinder 100 will be described with reference to Figures 1 and 2. The piston 120 is a solid cylindrical body and has a large diameter section approximately in the center, consisting of a front large diameter section 122 and a rear large diameter section 124. A medium diameter section 121 is provided in front of the front large diameter section 122, and a small diameter section 125 is provided behind the rear large diameter section 124. Furthermore, an annular groove 126 is provided between the front large diameter section 122 and the front edge 123 of the rear large diameter section, and a flow rate adjustment groove 127 is provided in the rear large diameter section 124. In other words, the rear large diameter section 124 is divided into the front edge 123 and the other part by the flow rate adjustment groove 127.

[0034] When this piston 120 is slidably fitted inside the cylinder 100, a piston front chamber 101 and a piston rear chamber 102 are defined at the front and rear of the cylinder 100, respectively. The piston pre-chamber 101 is provided with a pre-chamber port 103, which is constantly connected to the high-voltage circuit 110 via the pre-chamber flow path 112 through the pre-chamber port 103.

[0035] The piston rear chamber 102 is provided with a rear chamber port 104. The rear chamber port 104 and the first control valve 200 are connected by a rear chamber passage 113. The piston rear chamber 102 can alternately communicate with the high-voltage circuit 110 and the low-voltage circuit 111 by switching the forward and reverse direction using the valve 201 of the first control valve 200. An accumulator (not shown) is provided in the high-voltage circuit 110 as needed.

[0036] The outer diameter of the medium-diameter section 121 is set to be larger than the outer diameter of the small-diameter section 125. As a result, the pressure-receiving area of ​​the piston 120 in the piston front chamber 101 and piston rear chamber 102, that is, the diameter difference between the front large-diameter section 122 and the medium-diameter section 121, and the diameter difference between the rear large-diameter section 124 and the small-diameter section 125, is larger on the piston rear chamber 102 side.

[0037] The hydraulic impact device 1 shown in this embodiment is a "front chamber always high pressure type (rear chamber switching type)" in which the piston front chamber 101 is always connected to the high-pressure circuit 110, and the connection destination of the piston rear chamber 102 is switched. Therefore, with the structure described above, when the piston rear chamber 102 is connected to a high pressure due to the operation of the valve 201, the piston 120 moves forward due to the difference in pressure-receiving area, and when the piston rear chamber 102 is connected to a low pressure due to the operation of the valve 201, the piston 120 moves backward.

[0038] Furthermore, the cylinder 100 has a second control valve communication port 105, a first control valve communication port 107, a first low-pressure port 108, and a second low-pressure port 109 located axially separated from each other between the front chamber port 103 and the rear chamber port 104. The second low-pressure port 109 is equipped with a throttle 119 as a flow rate adjustment means to reduce the flow rate compared to the first low-pressure port 108. Furthermore, the second low-pressure port 109 is formed in a position that communicates with the piston rear chamber 102 when the piston 120 is at its front dead center.

[0039] [Structure of the first control valve] The structure of the first control valve 200 will be explained again by referring to Figure 1. In the following explanation, the position of valve 201 will be referred to as the "advance position" when it is located at the front end (left side of the diagram) shown in the lower half of the centerline, which moves the piston 120 forward, and the position of valve 201 when it is located at the rear end (right side of the diagram) shown in the upper half of the centerline, which moves the piston 120 backward, which moves it backward.

[0040] The first control valve 200 has a valve chamber formed inside that is not coaxial with the piston 120, and a valve 201 is slidably fitted into this valve chamber. The valve chamber has, in order from front to rear, a connecting chamber 212, a medium-diameter valve front chamber 213, a large-diameter valve main chamber 214, and a small-diameter valve rear chamber 215.

[0041] A pre-chamber flow path 223, which is in constant communication with the high-voltage circuit 110, is connected to the connection chamber 212. A valve front chamber 213 is formed at the rear. The valve main chamber 214 and the valve rear chamber 215 are provided with, in order from front to rear, a front low-pressure port 218, a valve control port 220, a rear low-pressure port 221, and a valve rear chamber port 222.

[0042] The front low-voltage port 218 and the rear low-voltage port 221 are constantly in communication with the low-voltage circuit 111. As mentioned above, the valve rear chamber port 222 is in communication with the rear chamber port 104 of the cylinder 100 via the rear chamber passage 113. The valve control port 220 is connected to the valve control passage 226. The valve control passage 226 is also in communication with the short stroke port 305 of the second control valve 300.

[0043] The valve 201 is a hollow cylindrical body having a medium-diameter section 202, a large-diameter section 203, and a small-diameter section 204, in order from front to rear. The inside of the cylinder is a hollow channel 228, which is in direct communication with the connection chamber 212. Therefore, the hollow channel 228 is also in constant communication with the high-voltage circuit 110. The valve 201 has an annular oil drain groove 205 on the outer circumferential surface of the larger diameter portion 203 side in the central part of the smaller diameter portion 204.

[0044] In this embodiment, the valve 201 has a connection chamber 212 connected to the high-voltage circuit 110, and is constantly biased backward due to the difference in pressure-receiving area at both ends of the valve 201 caused by the difference in diameter with the medium-diameter portion 202. While valve 201 is in the retracted position, the valve rear chamber port 222 communicates with the rear low-pressure port 221 via the oil drain groove 205. Therefore, the piston rear chamber 102 is in the rear low-pressure port twenty two 1 It is connected to the low-voltage circuit 111 via and retracts.

[0045] When high-pressure oil is supplied to the valve control port 220, the pressure-receiving area of ​​the rear stepped surface 209 of the large-diameter section 203 is increased, causing it to move forward and switch to the forward position. The front stepped surface 208, which is opposite to the rear stepped surface 209, is connected to the front low-pressure port 218, which is normally connected to the low-pressure circuit 111, and therefore does not actively participate in the switching of the valve 201. While valve 201 is in the forward position, the valve rear chamber port 222 is blocked from communication with the rear low-pressure port 221 via the oil drain groove 205. Meanwhile, the space between the rear end face 207 and the valve chamber rear end face 217 is opened, and communication with the high-pressure circuit 110 is established via the hollow passage 228 and the connecting chamber 212. As a result, the piston rear chamber 102 is connected to the high-pressure circuit 110 and moves forward.

[0046] [Structure of the second control valve] The structure of the second control valve 300 will now be explained with reference to Figure 1. The second control valve 300 is configured to be switchable between a short stroke mode position 301 (hereinafter referred to as the "SS position"), a normal stroke mode position 302 (hereinafter referred to as the "LS position"), and a dry-fire prevention mode position 303 (hereinafter referred to as the "dry-fire prevention position").

[0047] Each switching position is provided with a common port 304, a short-stroke port 305, and a dry-fire prevention port 306. When the SS position is 301, the common port 304 and the short stroke port 305 are in communication, and the dry-fire prevention port 306 is closed. When LS position is 302, all ports are blocked. When the dry-fire prevention position 303 is in place, the common port 304 and the dry-fire prevention port 306 are connected, and the short-stroke port 305 is closed.

[0048] The common port 304 is in communication with the second control valve communication port 105 of the cylinder 100 via the control flow path 114. As mentioned above, the short-stroke port 305 communicates with the first control valve communication port 107 of the cylinder 100, and also communicates with the valve control port 220 of the first control valve 200 via the valve control passage 226. The dry-fire prevention port 306 is in communication with the high-voltage circuit 110.

[0049] <Operation> Next, the operation of the hydraulic impact device 1 in each operating mode will be described with reference to Figures 3 to 8.

[0050] [Short Stroke Mode (SS Mode)] As shown in Figure 3, when operating in SS mode, the second control valve 300 is set to the SS position 301. This figure schematically shows the hydraulic impact device 1 in the process of the piston 120 striking the rod 150 and retracting, and the arrows in the figure represent the operation of the components.

[0051] When the hydraulic impact device 1 is set to SS mode, the piston 120 retracts and the front end of the large-diameter front section 122 reaches the second control valve communication port 105. At this point, the pressurized oil in the piston front chamber 101 is guided through the second control valve communication port 105 and the second control valve 300 to the valve control port 220 of the first control valve 200. As a result, the valve 201 switches to the forward position. In other words, when the hydraulic impact device 1 operates in SS mode, the piston 120 operates with a short stroke regardless of the hardness of the material to be crushed or whether dry striking occurs.

[0052] [Normal stroke mode (LS mode)] As shown in Figure 4, when operating in LS mode, the second control valve 300 is set to the LS position 302. This figure also schematically shows the hydraulic impact device 1 in the process of the piston 120 striking the rod 150 and retracting.

[0053] When the hydraulic impact device 1 is set to LS mode, the piston retracts and the front end of the large-diameter front section 122 reaches the first control valve communication port 107. At this point, the pressurized oil in the piston front chamber 101 flows directly from the first control valve communication port 107 into the valve control passage 226 and is guided to the valve control port 220 of the first control valve 200. As a result, the valve 201 of the first control valve 200 switches to the forward position. In other words, when the hydraulic impact device 1 operates in LS mode, the piston 120 operates at its normal stroke regardless of the hardness of the material to be crushed or whether dry striking occurs.

[0054] [Operation at the start of work when SS mode or LS mode is set] Next, referring to Figure 5, we will explain the operation at the start of work when set to SS mode or LS mode. Note that this operation relates to the operation when the piston 120 is located near the front dead center and is independent of whether it is set to SS mode or LS mode, so we will explain only the case when it is set to LS mode as an example.

[0055] Figure 5 schematically shows the state of the hydraulic impact device 1 immediately after the start of operation. At this time, no holding pressure from valve 201 is acting inside the first control valve 200, and valve 201 is in the forward position due to its own weight. Also, piston 120 is in the forward dead center position due to its own weight and the forward force from the backhead gas G inside backhead 400.

[0056] At the end of the operation, the valve control port 220 is connected to low pressure and the valve 201 is stopped in the retracted position. However, the typical working position of a hydraulic breaker is downward, and in this position, gravity acts on the valve 201 in the axial direction to the left in the diagram. Therefore, when the hydraulic breaker is changed to the working position at the start of the operation, the valve 201 may move from its normal stopping position (retracted position) to the forward position.

[0057] In this state, if pressurized oil is supplied to the high-pressure circuit 110 from the pump P, the piston rear chamber 102 may be connected to high pressure before the valve 201 has completed its movement to the rear end position. When pressurized oil is supplied to the piston rear chamber 102, there is a risk that it may leak out through the gap between the rear large-diameter portion 124 and the cylinder 100, causing a forward flow. However, in this embodiment, the second low-pressure port 109 opens at a position facing the piston rear chamber 102. Therefore, the pressurized oil in the piston rear chamber 102 flows out to the low-pressure circuit 111 through the second low-pressure port. In this way, the second low-pressure port 109 acts as a "recirculation prevention mechanism".

[0058] Therefore, leaked oil does not flow beyond the first low-pressure port 108 into the first control valve communication port 107 and return to the valve control port 220. If pressurized oil is not supplied to the valve control port 220, the valve 201 returns to the retracted position as pressurized oil is supplied to the high-pressure circuit 110, the piston rear chamber 102 is connected to the low-pressure circuit, and the piston 120 begins to retract.

[0059] Furthermore, when the hydraulic impact device 1 is set to stroke adjustment mode and the piston 120 is at its front dead center, the hydraulic fluid in the valve control port 220 needs to be discharged when the valve 201 switches to the retracted position. In the hydraulic impact device disclosed in Patent Document 1, the area between the second control valve 300, the second control valve communication port 105, the first control valve communication port 107, and the valve control port 220 constituted a closed circuit CC1. In this embodiment, the relevant portion is referred to as circuit CC2.

[0060] In this embodiment, when pressurized oil is supplied to the high-pressure circuit 110, the hydraulic fluid in the valve control port 220 flows out to the low-pressure circuit 111 via the flow rate adjustment groove 127 and the first low-pressure port 108 as the valve 201 operates. Thus, in the hydraulic impact device 1 according to the present invention, the first low-pressure port 108 and the flow rate adjustment groove 127 act as residual pressure release mechanisms.

[0061] [Anti-dry-shot mode] As shown in Figures 6 and 7, when operating in dry-fire prevention mode, the second control valve 300 is set to the dry-fire prevention position 303. In the dry-fire prevention mode, if a dry-fire occurs during striking, the operation of the piston 120 is stopped.

[0062] Figure 6 schematically shows the hydraulic impact device 1 after a "normal impact," in which the piston 120 that struck the rod 150 begins to retract immediately after impact, such as when the material to be crushed is sufficiently hard. In this case, focusing on the first control valve 200, since the valve control port 220 is not in communication with the high-voltage circuit, the valve 201 moves to the retracted position.

[0063] As mentioned above, when the second control valve 300 is set to the dry-fire prevention position 303, the common port 304 and the dry-fire prevention port 306 are in communication, so the high-voltage circuit 110 is connected to the second control valve communication port 105 via the second control valve.

[0064] Therefore, as shown in Figure 6, even when the piston 120 retracts and its front large-diameter portion 122 reaches the second control valve communication port 105, the second control valve communication port 105 only functions as part of the piston pre-chamber 101. As a result, the valve control port 220 remains isolated from the high-voltage circuit 110, and the piston 120 continues to retract. In other words, during normal striking, the piston 120 operates with a normal stroke, similar to when the LS mode is set.

[0065] If a dry strike occurs, as shown in Figure 7, the piston 120 advances beyond the point of impact and the annular groove 126 reaches the second control valve communication port 105. As a result, the high-voltage circuit 110 becomes directly connected to the low-voltage circuit 111 via the second control valve communication port 105, the annular groove 126, the first control valve communication port 107, the flow rate adjustment groove 127, and the first low-voltage port 108.

[0066] Stating only the resulting operation first, the hydraulic pressure of the high-pressure circuit 110 decreases, and the hydraulic pressure supplied to the piston front chamber 101 and the valve control port 220 of the first control valve 200 decreases. As a result, the first control valve 200 maintains the retracted position, and the hydraulic pressure in the piston front chamber 101 becomes less than the forward force generated by the gas pressure in the backhead 400, so the piston 120 stops at the top dead center.

[0067] <Details of the dry-fire prevention mechanism> More specifically, the decompression amount in the high-pressure circuit 110 and the structure for realizing decompression for realizing the operation when the dry-fire prevention mechanism operates will be described. Regarding the decompression amount necessary for operating as the dry-fire prevention mechanism, first, an explanation will be given by focusing on the relationship between the pressures supplied to the valve front chamber 213 and the valve control port 220 of the first control valve 200.

[0068] Let the effective pressure of the hydraulic oil supplied to the valve front chamber 213 of the first control valve 200 be p1, and the effective pressure of the hydraulic oil supplied to the valve control port 220 be p2. Also, let the area of the front end face 206 of the valve 201 be d1, and the area of the rear end face 207 be d2. And let the area of the stepped surface 209 on the rear side of the valve 201 be d3.

[0069] Here, as described in the structure of the first control valve 200, the following relationships hold for the areas d1 to d3. d1 > d2... Equation 1 d1 < d2 + d3... Equation 2 From Equation 1 and Equation 2, (d1 - d2) < d3... Equation 3 That is. Therefore, the thrust for setting the valve 201 to the retracted position becomes Equation [4]. p1 × (d1 - d2) > p2 × d3... Equation 4

[0070] When "p2 ≠ 0", in order to set the valve 201 to the retracted position, it is necessary that "p1 and p2 are values that satisfy Equation 4", and it is obvious that "p 1 > p 2 ". It is necessary, and it is obvious that "p1 > p2". Therefore, from pump P, which is the supply route for p1 Valve anteroom 213 The route to and the supply route of p2 We focus on the path from a certain pump P to a valve control port 220.

[0071] Here, the gap between the annular groove 126 and the second control valve communication port 105 functions as a throttle valve that reduces the operating hydraulic force supplied to the valve control port 220. Furthermore, the supply route for p2 is longer than the supply route for p1. Therefore, at least "p1 > p2" holds true.

[0072] Furthermore, the gap between the flow rate adjustment groove 127 and the first control valve communication port 107 functions as a throttle provided between the high-pressure circuit 110 and the low-pressure circuit 111. Therefore, by adjusting the size of the annular groove 126 and the flow rate adjustment groove 127, the pressures of p1 and p2 after depressurization can be set.

[0073] Furthermore, if the operating hydraulic force in the high-pressure circuit 110 is high enough to compensate for the difference in path losses, the relationship in Equation 4 does not hold, and the valve 201 is maintained in the forward position. Even in such a case, since forward force continues to be applied to the piston 120 after dry firing, the function as a dry firing prevention mechanism is not lost.

[0074] In other words, the components for achieving pressure reduction are the annular groove 126, the flow rate adjustment groove 127, and the first low-pressure port 108. Furthermore, the amount of pressure reduction when focusing on the first control valve 200 is the value for which Equation 4 holds true.

[0075] Furthermore, if the pressure in the high-pressure circuit is reduced to a completely low pressure, in other words, if the space between the flow control groove 127 and the normal stroke port functions as an unload valve, the pressure required to hold the valve 201 in the retracted position will cease to act. Therefore, the lower limit of the effective pressure p1 after pressure reduction will be the pressure at which the valve 201 can be held in the retracted position.

[0076] Specifically, the pressure is such that it can exert a holding force sufficient to resist the thrust generated by the weight of the valve 201. As mentioned above, when the hydraulic impact device 1 is used for small-scale crushing work, the rod 150 is often positioned along the vertical axis with its tip pointing downwards, and in this case, a thrust is generated in the direction that switches the valve 201 to the forward position due to its own weight.

[0077] Next, we will explain the amount of pressure reduction by focusing on the relationship between the forward and reverse forces of the piston 120. The piston 120 is biased in the forward direction by the backhead gas G in the backhead 400. Here, let D1 be the area of ​​the stepped surface between the middle diameter portion 121 and the front large diameter portion 122 of the piston 120, let P1 be the effective pressure supplied to the piston front chamber 101, and let F be the thrust acting on the piston 120 by the backhead gas G in the backhead 400. In this case, the forward force acting on the piston 120 is given by Equation 5. F-(P1×D1)...Formula 5

[0078] As mentioned above, the hydraulic fluid pressure in the high-pressure circuit 110 is reduced. Therefore, if P1 is reduced to a value that satisfies equation 6, the piston 120 moves forward due to the gas pressure and is held at the front dead center. F>P1×D1…Formula 6 If P1 does not satisfy Equation 6, the piston 120 stops at a position where the gas pressure that has risen due to its retraction balances with the retraction force P1 × D1.

[0079] When the piston 120 is held at its front dead center in this manner, in order to restart the piston 120, it is necessary to operate the hydraulic striking device 1 to retract the rod 150 so that it abuts against the piston 120 and push the piston 120 in. Specifically, the piston 120 is retracted to a position where the leading edge 123 of the rear large-diameter portion blocks the first control valve communication port 107 and the first low-pressure port 108.

[0080] This section explains the restarting force required during the restart operation. Furthermore, R is the thrust force that causes the rod to strike and retract the piston 120, which is the restarting force. At this time, as part of the restarting force, a retraction force P1 × D1 acting on the piston 120 is exerted against the gas pressure. That is, the lower limit of R is defined as shown in Equation 7. R>F-(P1×D1)…Formula 7 From Equation 7, it is clear that the higher the hydraulic fluid pressure in the high-voltage circuit 110, the lower the external force required for restarting.

[0081] In other words, focusing on the relationship between the forward and backward forces of the piston 120, the ideal amount of pressure reduction in the hydraulic fluid pressure within the high-pressure circuit 110 is the maximum value within the pressure range that satisfies Equation 6.

[0082] Considering the above requirements for the first control valve 200 and restarting force, if the hydraulic impact device 1 has a throttle formed between the first control valve communication port 107 and the flow rate adjustment groove 127 that reduces the operating hydraulic force in the high-pressure circuit 110 to the maximum value of the values ​​satisfying equations 4 and 6 when the piston 120 is at its front dead center, it is possible to realize a dry-firing prevention mechanism that requires a low external force for restarting.

[0083] <Effects> Furthermore, in order to compare the design and manufacturing costs of these hydraulic impact devices, we will focus on the flow rate required for the main components and the trade-off relationship that exists between the magnitude of the flow rate and the flow rate. These characteristics can be summarized as shown in Table 2 for the hydraulic impact device disclosed in Patent Document 1, and as shown in Table 3 for the hydraulic impact device 1 according to the present invention. [Table 3]

[0084] As shown in Table 2 above, the hydraulic impact device disclosed in Patent Document 1 has a trade-off relationship between the second low-pressure port, the first throttle, the second throttle, the drain groove, and the drain slit in relation to the required flow rate. In other words, in order to achieve both a dry-firing prevention mode and a stroke adjustment mode, and to achieve a high level of balance between the operability of the dry-firing prevention mechanism and the ability to restart from a state where the dry-firing prevention function has been activated, the flow area of ​​each part must be precisely designed. Furthermore, in order to manufacture a hydraulic impact device that can achieve such precision, precision machining is required, which can lead to a decrease in product yield. Overall, the configuration disclosed in Patent Document 1 tends to have high design and manufacturing costs.

[0085] In contrast, the hydraulic impact device according to the present invention does not have the trade-off relationship required for the flow rate that occurred in the hydraulic impact device disclosed in Patent Document 1. In particular, because the piston rear chamber 102 is connected to the low-pressure circuit 111 when the dry-firing prevention mechanism is activated, and the drain groove is abolished and the drain slit is switched to a flow rate adjustment groove, the strictness required for the flow path area is reduced compared to the hydraulic impact device disclosed in Patent Document 1. As shown in Table 3, in the dry-firing prevention mode, when transitioning to dry-firing prevention, the pressure reduction mechanism and flow rate need to be kept within the range that achieves medium pressure, but since the adjustment range of the flow rate adjustment groove 127 is wide, there is no particular difficulty in achieving medium pressure itself.

[0086] In particular, if the flow control groove 127 reduces the operating hydraulic force in the high-pressure circuit to a pressure range that satisfies equations 4 and 6, the dry-firing prevention mechanism will operate stably, thus reducing the precision required for design and manufacturing. In general, the hydraulic impact device according to the present invention can reduce the costs required for design and manufacturing without impairing the functions of the hydraulic impact device disclosed in Patent Document 1.

[0087] Furthermore, when comparing this configuration with the hydraulic impact device disclosed in Patent Document 1, the piston 520 disclosed in Patent Document 1 also has a drain groove and a drain slit formed as a residual pressure release mechanism. Here, the drain groove is a configuration unique to the hydraulic impact device disclosed in Patent Document 1, and the drain slit is a configuration corresponding to the flow rate adjustment groove 127 provided in the hydraulic impact device 1 according to the present invention. However, since the flow control groove is designed to handle larger flow rates than the drain slit, its flow path area is larger. Due to these differences in configuration, the flow rate of hydraulic fluid flowing from the closed circuit section to the low-pressure circuit 111 is also higher with the flow rate adjustment groove 127 according to the present invention, making it advantageous as a residual pressure release mechanism.

[0088] Furthermore, while Patent Document 1 describes that when the drain groove 540 is formed over a wide area, the recirculation of leaked oil from the piston rear chamber 502 increases, the present invention prevents an increase in leaked oil by providing a second low-pressure port that is directly connected to the piston rear chamber 102 while the piston 120 is at its front dead center. As a result, the stability of the operation of the piston 120 at the start of operation is improved compared to the hydraulic impact device disclosed in Patent Document 1. [Explanation of Symbols]

[0089] 1...Hydraulic impact device, 100...Cylinder, 101...Piston front chamber, 102...Piston rear chamber, 103...Front chamber port, 104...Rear chamber port, 105...Second control valve communication port, 107...First control valve communication port, 108...First low-pressure port, 109...Second low-pressure port, 110...High-pressure circuit, 111...Low-pressure circuit, 112...Front chamber flow path, 113...Rear chamber flow path, 114...Control flow path, 119...Throat, 120...Piston, 121...Medium diameter section, 122...Front large diameter section, 123...Rear large diameter section leading edge, 124...Rear large diameter section, 125...Small diameter section, 126...Annular groove, 127...Flow rate adjustment groove, 150...Rod, 200...First control valve, 201...Valve, 202...Medium diameter section, 203...Large diameter section, 204...Small diameter section 205…Oil drain groove, 206…Front end face, 207…Rear end face, 208…Front stepped surface, 209…Rear stepped surface, 212…Connection chamber, 213…Valve front chamber, 214…Valve main chamber, 215…Valve rear chamber, 217…Valve chamber rear end face, 218…Front low-pressure port, 220…Valve control port, 221…Rear low-pressure port, 222…Valve rear chamber port, 223…Front chamber flow path, 226…Valve control flow path, 228…Hollow flow path, 300…Second control valve, 301…SS position, 302…LS position, 303…Dry-firing prevention position, 304…Common port, 305…Short stroke port, 306…Dry-firing prevention port, 400…Backhead, CC1…Closed circuit, CC2…Circuit, G…Backhead gas, P…Pump

Claims

[Claim 1] A hydraulic striking device comprising a cylinder and a piston slidably fitted into the cylinder so as to be able to move back and forth, having a large diameter portion with an annular groove, a medium diameter portion in front of the large diameter portion, and a small diameter portion behind the large diameter portion, wherein a piston front chamber is defined between the medium diameter portion and the front of the large diameter portion, a piston rear chamber is defined between the small diameter portion and the rear of the large diameter portion, and a second control valve communication port, a first control valve communication port, and a low-pressure port are provided between the piston front chamber and the piston rear chamber in this order from front to rear, A first control valve that controls the forward and backward movement of the piston, A stroke adjustment mechanism for adjusting the stroke of the piston between at least a normal stroke and a short stroke, A dry-fire prevention mechanism is provided that, when the piston moves forward a predetermined distance beyond the striking position, moves the piston forward to its front dead center to stop operation. A second control valve is provided to select either the mode of the stroke adjustment mechanism or the dry-firing prevention mechanism, The second control valve communication port communicates with the second control valve via a passage, communicates with the piston front chamber when the piston retracts, and communicates with the first control valve communication port via the annular groove when the piston moves beyond the point of impact to the front dead center. The low-pressure port comprises a first low-pressure port that opens at a position where the annular groove provided on the large-diameter portion of the piston connects the first control valve communication port and the low-pressure circuit when the piston is switched from the forward stroke to the reverse stroke, and a second low-pressure port that opens into the piston rear chamber at an axial rearward position of the first low-pressure port when the piston has advanced to its forward dead center. A throttle is provided to adjust the flow rate through the second low-pressure port to be less than the flow rate through the first low-pressure port. A hydraulic impact device characterized in that, as a dry-fire prevention mechanism, the large-diameter portion is provided with a flow rate adjustment groove that connects the first control valve communication port and the first low-pressure port when the piston is advanced to its front dead center, thereby reducing the pressure of the high-pressure circuit to below the operating pressure.

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