JPS61279473A - Hydraulic striking tool - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to hydraulic impact tools such as rock drills and breakers.

[Prior Art] Conventionally, this type of hydraulic impact tool has been provided with an impact cylinder that repeatedly impacts the chisel.
Hydraulic pressure is constantly supplied to the front chamber of this percussion cylinder, while hydraulic pressure is intermittently supplied to the rear chamber via a hydraulic pressure switching means, and the percussion piston is controlled according to the difference in pressure receiving area when the i+h pressure is supplied. It has a structure that moves it forward.

By the way, in this type of hydraulic impact tool, an accumulator is connected to an oil supply passage that supplies hydraulic pressure to the front chamber, and when the amount of oil supplied to the front chamber is insufficient, the accumulated oil is supplied to this accumulator. ing. This accumulator is equipped with a hard rubber diaphragm called a bladder, and one chamber is filled with nitrogen gas at a constant pressure, and the displacement of the bladder accumulates pressure in the ura or discharges the accumulated oil. It is used.

However, the oil pressure supplied to the front chamber tends to become unstable, especially when oil accumulates in the accumulator when starting the hydraulic impact tool and the oil pressure supplied to the front chamber increases, and when stopping the hydraulic impact tool, In addition, even if the valve is operated or the pressure oil is cut off, until the oil accumulated in the accumulator is consumed, the accumulator becomes the oil pressure source and the impact is performed.In this way, the oil pressure is insufficient. In a stable state, the bladder of the upper accumulator flaps, and if the bladder is sucked into the small hole formed as the discharge port of this accumulator, a so-called tear may occur and the bladder may be damaged. For this reason, the lifespan of the bladder is surprisingly short, and the frequency of replacement of the bladder has increased, creating a major problem in terms of maintenance and management.

In this regard, in the past, attempts have been made to improve the durability of the bladder itself, but the current situation is that it is not possible to extend the life span to a sufficiently satisfactory extent.

In addition, a type of breaker has been proposed in which the hydraulic pressure switching valve for impact is opened and hydraulic pressure is applied only when the breaker is pressed against the ground with the boom, but it is not possible to press the breaker with the boom. In addition to being applicable only to hydraulic impact tools, it is still not possible to effectively prevent hydraulic instability in the early stages of operation, and it is not possible to extend the life of the bladder.

[Object of the Invention] An object of the present invention is to provide a hydraulic impact tool that can prevent the bladder of an accumulator from flapping as much as possible, thereby extending the life of the bladder.

[Structure of the Invention] Therefore, the present invention provides a hydraulic impact tool in which an accumulator is communicated with an oil supply passage leading to a front chamber of a percussion cylinder, in which the oil pressure of the oil supply passage is connected to the communication passage connecting the accumulator and the oil supply passage. A hydraulic response valve is provided that opens the two-leg communication passage only when the hydraulic pressure rises above the set pressure, and conversely, when the hydraulic pressure becomes lower than the set pressure. It is characterized by a structure in which the communication passage is closed and high pressure is confined in the accumulator.

[Effects of the Invention] According to the present invention, since the accumulator is shut off from the oil supply passage at the initial stage of startup and at the time of stopping, it is possible to reliably prevent the bladder from fluttering due to oil pressure fluctuations, and to prevent early deterioration of the bladder. can be effectively prevented.

In addition, it is possible to prevent idle firing when stopping due to this.

[Example] Examples of the present invention will be specifically described below.

As shown in FIG. 1, a striking cylinder 2 incorporating a striking piston 1 has a front chamber 3 and a rear chamber 4 separated by a large diameter portion la of the striking piston I, and a first chamber 4 is formed in the front chamber 3. Hydraulic pressure is constantly supplied from the ura supply passage 5. Further, hydraulic pressure is intermittently supplied to the rear chamber 4 of the striking cylinder 2 by a second oil supply passage 6, and this intermittent supply of hydraulic pressure is performed by a hydraulic pressure switching valve 7. 7 is switched by hydraulic pressure from a hydraulic pressure switching passage 8 communicating with the front chamber 3. Note that 9 in FIG. 1 is a passage for removing the hydraulic pressure from the hydraulic pressure switching passage 8 at the end of the retraction of the striking piston l of the rear chamber 4.

As shown in FIG. 1, an accumulator IO is located in the middle of the first oil supply passage 5 that supplies hydraulic pressure from a hydraulic pressure source to the front chamber 3.
are connected via a communication path 11.

A hydraulically responsive valve 12 that opens and closes this passage is interposed in the middle of this communication path 11, and only when this hydraulically responsive valve 12 opens to communicate with the communicating path 11, the accumulator 10
The oil in the oil storage chamber 13 is accumulated through the small holes 14, 14, . . . , or the accumulated oil is discharged.

As mentioned above, this accumulator IO has a well-known structure in which an inert gas, such as nitrogen gas, at a predetermined pressure is sealed in a gas chamber 16 that is separated from the oil storage chamber 13 by a hard rubber bladder I5. .

The hydraulic pressure responsive valve 12 has a valve body 1 having two stages of wide and narrow pressure receiving portions 17a and 17b that receive hydraulic pressure from the first oil supply passage 5.
7, and this valve body 17 is biased in the valve closing direction by a coil spring 18, and the opening pressure of the hydraulically responsive valve 12 is set by the spring force of this coil spring 18. In other words, until the hydraulic pressure acting on the first oil supply passage 5 rises above the valve opening pressure set by the coil spring 18, the communication passage 11 is closed to the hydraulic response valve 1.
2, thus blocking the accumulator lO and the first oil supply passage 5, and preventing oil from flowing in and out of the accumulator 10. On the other hand, when the oil pressure rises above the set value, the above-mentioned pressure receiving area difference By valve body 17
is pushed down against the spring force of the coil spring 18, and as a result, the communication path 11 is opened and the accumulator 1
0 and the first oil supply passage 5 are communicated with each other, and in this state, oil can enter and exit the accumulator 10 for the first time.

The state shown in FIG. 1 shows a state in which the impact piston 1 is located at the forward position, and in this state, the itb pressure switching passage 8
When a high hydraulic pressure acts on the back side of the hydraulic switching valve 7, the hydraulic switching valve 7 is operated in the right direction A in FIG.
The hydraulic pressure in the rear chamber 4 decreases, and the striking piston l
is pushed backward by the hydraulic pressure acting on the front chamber 3, and when the striking piston l is further retreated, the hydraulic pressure switching passage 8 is cut by another large diameter portion 1b formed in the striking piston l, so that the hydraulic pressure switching The valve 7 is moved back to the left in FIG. As a result, the second oil supply passage 6 is again connected to 411
It is connected to a pressure source, and the striking piston 1 is driven by the pressure. Thereafter, by repeating this action, the so-called striking action is continuously repeated.

Furthermore, when the hydraulic pressure from the hydraulic source is cut when the impact is stopped, the hydraulic pressure in the first oil supply passage 5 decreases, and in response to this decrease, the hydraulic response valve 12 is immediately activated by the spring force of the coil spring 18 to connect the accumulator 10 and the first oil Communication with the supply passage 5 is cut off, and the oil in the accumulator IO is confined at high pressure.

FIG. 2 shows another example of a hydraulically responsive valve.

This hydraulically responsive valve 12' has a stopper portion 20. A valve body 23 is provided in which a large-diameter valve body 21 and a shaft 22 around which a coil spring 24 is wound are integrally formed in the axial direction, and a first oil supply that acts on the end face of the large-diameter valve body 2 is provided. Basically, when the oil pressure in the passage 5 rises to exceed the valve opening pressure set by the coil spring 24, the communication passage 11 is communicated with the first oil supply passage 5, and the flow of oil into and out of the accumulator IO is controlled. It is designed to make it possible.

As described above, a hydraulic response valve is provided in the oil supply passage that supplies hydraulic pressure to the iη chamber of the impact cylinder and the communication passage with the accumulator, and the hydraulic pressure in the oil supply passage rises beyond the set pressure, causing the hydraulic pressure to be supplied. Since the hydraulic response valve is opened only when the oil pressure has stabilized, and the accumulator is communicated with the oil supply passage, it is possible to reliably prevent the accumulator bladder from fluttering due to unstable oil pressure fluctuations. Not only can the lifespan be greatly improved, but also the advantage of easy implementation is obtained because it is only necessary to arrange a hydraulically responsive valve in the communication path.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view of the main parts of a hydraulic impact tool according to an embodiment of the present invention, and FIG. 2 is an explanatory cross-sectional view of the main parts showing a modification of the hydraulically responsive valve. 1...Blow piston, 2...Blow cylinder, 3...
- Front chamber, 4... Rear chamber, 5... First oil supply passage, 6...
-Second oil supply passage, 7...hydraulic switching valve, IO...accumulator, ll...communication passage, 12゜12''...
Hydraulic response valve. Patent applicant Mazda Motor Corporation representative Patent attorney Blue and white Two idiots Figure 1 So 10:t
ID Figure 2 O

Claims (1)

[Claims] (1) In a hydraulic impact tool in which an accumulator is connected to an oil supply passage leading to the front chamber of the impact cylinder, when the oil pressure in the oil supply passage increases to a set pressure or higher in the communication passage connecting the accumulator and the oil supply passage, A hydraulic impact tool, characterized in that it is provided with a hydraulic response valve that opens the communication passage.