JP2834744B2 - Automatic control device for impact force and number of impacts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is applied to a tip of a hydraulic excavator or the like,
The present invention relates to an automatic control device for the impact force and the number of impacts of a hydraulically operated impact power tool used for demolition of concrete structures, crushing of rocks, rock excavation, and the like.

[Conventional technology]

Hydraulically operated impact tools can be broadly divided into accumulator systems and gas systems.

The accumulator method is a method of accumulating oil in an accumulator when the piston moves upward, discharging the oil during a striking stroke, and accelerating the piston.

The gas method is used when the piston rises by hydraulic pressure,
Energy is accumulated by compressing the gas in the gas chamber above the piston, and during the impact stroke, the piston is accelerated by using the expanding energy of the gas.
No. 32192 discloses this method.

By the way, when crushing soft rocks or rocks with many cracks, the impact frequency is not so required, so the impact frequency is increased, and when crushing hard rocks, the impact force needs to be increased, and the impact frequency may be less. It is well known.

Japanese Utility Model Publication No. 60-26938 discloses an impact tool in which reciprocation of a piston is performed only by hydraulic pressure. Thus, the striking cycle and the striking force are changed.

Japanese Unexamined Patent Publication No. Sho 62-9878 discloses a method in which a piston is similarly moved up and down by hydraulic pressure. The displacement of the piston is electrically detected by a differential transformer, and an electric / hydraulic servo is output by the output signal. The valve and the electromagnetic proportional relief valve are controlled to feedback-control the movement of the piston.

[Problems to be solved by the invention]

Among the above prior arts, the one described in Japanese Utility Model Publication No. 60-26938 has the advantage that the structure is simple, but only adjusts the return speed of the piston, and the adjustment of the hydraulic fluid pressure in the striking direction is not possible. The problem is that accurate control of the hitting cycle is not possible because of the inability to do so.

Further, in the device disclosed in Japanese Patent Application Laid-Open No. 62-9878, a differential transformer must be provided at the upper part of the cylinder in order to electrically detect the displacement of the piston, and a strong impact acting on the cylinder is applied to the differential transformer. So there is a problem with reliability. In addition, expensive parts such as an electric / hydraulic servo valve and an electromagnetic proportional relief valve are required, which increases the cost.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the conventional hitting device and to provide a control device for automatically changing the number of hits and the hitting force according to the hardness of the object to be crushed.

[Means for solving the problem]

In order to achieve the above object, the present invention connects a pressure adjusting chamber having a volume adjusting means to a gas chamber of an impact device, and a gas detector is provided in the gas chamber. This is to control the volume adjusting means.

Further, a displacement amount of the piston when the piston striking the chisel rebounds is calculated by an arithmetic circuit which receives an output of the pressure detector as an input, and the control switching valve of the volume adjusting means is controlled based on the calculated value. Some have been made.

[Action]

The present invention is configured as described above. When the pressure of the gas chamber causes the lowered piston to hit a chisel or the like and the repulsive force raises the piston, the gas pressure of the gas chamber increases instantaneously.

As described above, the pressure detector detects the instantaneous pressure rise in the gas chamber, inputs the output to an arithmetic circuit and calculates the amount of displacement of the piston, and determines the amount of displacement of the piston according to the value. The volume adjusting means is operated to adjust the gas pressure in the gas chamber to a gas pressure corresponding to the hardness of the object to be crushed, and to set the striking force and the impact cycle of the piston to optimal values for the hardness of the object to be crushed.

〔Example〕

In the first embodiment shown in FIG. 1, reference numeral 1 denotes a cylinder having a tool 2 such as a chisel attached to the lower end so as to be able to move forward and backward.

The cylinder 1 has a large-diameter portion 3 at an intermediate portion, and a piston 4 that hits the tool 2 when descending is fitted therein. Gas pressure is applied to the upper surface of the raised piston 4 above the cylinder 1. A gas chamber 5 containing gas is provided.

An intermediate chamber 6 and a lower chamber 7 are provided between the upper and lower small diameter portions of the large diameter portion 3 of the piston 4 and the inner circumference of the cylinder 1.

Reference numeral 8 denotes a valve chamber provided on a side portion of the cylinder 1 and a valve body 10 having a communication hole 9 in the center is fitted in the valve chamber.

The upper and lower portions of the valve chamber 8 communicate with the lower portions of the middle chamber 6 and the lower chamber 7 through oil passages 14 and 16, respectively. From the oil path that branches off.

A drain port 11 and a fuel filler port are provided near the upper and lower portions of the valve chamber 8.
The oil passage 12 communicates with the oil passage 12, and the oil passage communicating with the oil supply port 12 communicates with the rear part of the plunger 13 that pushes down the valve body 10.

Reference numeral 20 denotes a pressure adjustment chamber provided above the gas chamber 5 and communicates with the gas chamber 5 through a communication hole 41.

A piston 21 is fitted in the adjustment chamber 20 as a volume adjusting means.

Reference numeral 22 denotes a plunger integrally provided on the piston 21, reference numeral 23 denotes a pressurizing chamber, and the plunger 22 slidably passes through the chambers 20, 23.

Reference numeral 24 denotes a switching valve provided in the middle of a hydraulic circuit between the pressurizing chamber 23 and the hydraulic unit 25. The hydraulic unit 25 includes a hydraulic pump 26, an oil tank 27, and the like.

The gas chamber 5 is provided with a pressure detector 30. The pressure detector 30 converts the gas pressure in the gas chamber 5 into an electric signal. To avoid being affected by the vibration of the cylinder 1 when mounting the cylinder 1.

In the impact power tool of the above embodiment, when the valve element 10 is at the lower limit as shown in FIG. 1, the oil pressure from the oil supply port 12 is applied to the lower chamber 7 through the oil passage 16 and the middle chamber 6 is connected to the oil discharge port 11. The piston 4 rises and compresses the gas in the gas chamber 5.

When the lower end of the large-diameter portion 3 becomes higher than the oil passage 15 due to the rise of the piston 4, the oil supply port 12 leads to an oil passage that pushes up the valve body 10,
The valve body 10 rises by the action of hydraulic pressure, and the lower chamber 7 communicates with the oil discharge port 11 through the communication hole 9 of the valve body 10, so that the piston 4 descends due to the gas pressure in the gas chamber 5, and the tool 2 is hit. I do.

I and II in FIG. 4 show changes in the pressure of the gas chamber during the above-mentioned operation, in which the vertical axis represents the pressure and the horizontal axis represents the passage of time from left to right.

In this figure, a is the starting point of the lowering of the piston, b is the striking point, and c is the upper limit of the rebound.

The above pressure change is amplified as an electric signal from the detector 30 by the amplifier 31 in FIG.
Input to the arithmetic circuit 33.

The above circuit integrates the pressure-time relationship between the time T from the point of impact b of the piston to the upper limit of repulsion c in FIG. 4 (I).

The higher the hardness of the object to be crushed, the higher the height of the piston 4 when it rebounds, and the gas pressure in the gas chamber 5 increases in proportion to this, so that the integral value in the circuit 33 also increases.

That is, since the value of the output of the circuit 33 is proportional to the hardness of the object to be crushed, whether the value is high or low is compared with a preset value in the comparison determination circuit 34, and if the value is higher than the set value, the driving circuit Send a pressure rise signal to 35.

The drive circuit 35 that has received the pressure increase signal switches the switching valve 24 to the pressure increase side (the position in FIG. 1), so that the hydraulic unit 25
Is supplied to the pressurizing chamber 23 and the plunger 22 is pushed down.

The lowering of the plunger 22 lowers the piston 21 integral therewith, and reduces the volume of the lower part of the pressure adjusting chamber 20 communicating with the gas chamber 5 to increase the pressure of the gas chamber 5.

When the pressure in the gas chamber 5 rises in this way, the striking force of the piston 4 due to the gas pressure increases.

Further, the pressure of the lower chamber 7 of the cylinder 1 is also determined by the gas pressure, and when the gas pressure increases, the hydraulic pressure of the working oil supplied to the oil supply port 12 also increases.

Generally, this type of device is mounted as an attachment to a hydraulic excavator and supplies hydraulic pressure from the hydraulic
Supply to 12.

Most of the hydraulic pressure of a general power shovel changes with the correlation between the hydraulic pressure and the flow rate as shown in FIG.

That is, in FIG. 5, if the vertical axis increases the flow rate from bottom to top and the horizontal axis increases the pressure from left to right,
A curve A is obtained.

Accordingly, although the piston 4 is operated at the pressure P ₀ and the flow rate Q ₀ at first, when the pressure is increased to P ₁ , the flow rate decreases to Q ₁ .

When the flow rate of the pressure oil flowing into the lower chamber 7 of the cylinder 1 decreases, the number of impacts of the piston 4 decreases. Therefore, when the object to be crushed is hard, the impact force of the piston 4 increases and simultaneously the number of impacts decreases. Performs powerful crushing action.

Conversely, if the object to be crushed becomes soft, the rebound height of the piston 4 at the time of impact decreases, and the comparison determination circuit
A signal for pressure reduction is output from the cylinder drive circuit 35 to the cylinder drive circuit 35.

When the above signal is output, the switching valve 24 is switched to the drain side. The pressure oil in the pressurizing chamber 23 is returned to the oil tank 27 via the switching valve 24.

The piston 21 is pressed by gas pressure with the discharge of the pressurized oil from the pressurizing chamber 23.
Rises, increasing the volume under the pressure regulating chamber 20 and decreasing the gas pressure in the gas chamber 5.

As a result, the impact force of the piston 4 decreases, and the number of impacts increases.

During the operation of the switching valve 24, when the pressure reaches a predetermined pressure and the output signal from the comparison determination circuit 34 becomes zero in both cases of pressure increase and pressure decrease, the switching valve 24 becomes the neutral position and the pressurizing chamber Close 23.

In the above arithmetic circuit 33, when a differentiating circuit is used (see (II) in FIG. 4), the gas pressure in the gas chamber 5 after a lapse of a predetermined time t from the strike point b of the piston 4 is detected. If the pressure is high, the object to be crushed is determined to be hard, and if the gas pressure is low, it is determined to be soft, and the operation of the switching valve 24 and the like is the same as in the case of integration.

FIG. 2 shows a second embodiment, in which a pressure regulating chamber 20 is provided in a container 38 provided separately from the cylinder 1, and one of the chambers 20 is communicated with the gas chamber 5 through a communication passage 39. The other is a communicating passage
40 communicates with the oil unit 25 via the switching valve 24.

In this embodiment, the plunger 22 serves as a guide for the piston 21.

In the case of the second embodiment, the pressure chamber 23 shown in FIG. 1 is not provided, and instead, the plunger 22 side of the adjustment chamber 20 is connected to the pressure section 28.
And

In this example, the hydraulic pressure applied to the pressurizing unit 28 is controlled to
Is changed to adjust the pressure of the gas chamber 5, and other configurations and operations are the same as those of the first embodiment.

〔The invention's effect〕

According to the present invention, the gas chamber communicates with the pressure adjusting chamber having the volume adjusting means as described above, and the gas chamber is provided with a pressure detector, and the signal from the pressure detector controls the volume adjusting means. Further, the amount of displacement of the piston when the piston hitting the chisel rebounds is calculated by an arithmetic circuit which receives the output of the pressure detector as an input, and based on the value, the control switching valve of the volume adjusting means is controlled. Because it is controlled, the instantaneous pressure rise of the gas chamber due to the repulsive force when the piston hits the chisel etc. is detected and the gas pressure rise is determined, and the pressure adjustment chamber is determined according to the value. Activate the volume adjusting means to adjust the gas pressure in the gas chamber to a gas pressure corresponding to the hardness of the object to be crushed, and to set the impact force of the piston and the impact cycle to optimal values for the hardness of the object to be crushed. It is.

Therefore, in the crushing operation of rocks and the like, the striking force of the piston and the cycle of striking are automatically adjusted according to the change in hardness of the rocks and the like, and efficient crushing work can always be performed with the optimal striking force and the striking cycle. .

Also, since it detects the repulsion state of the piston based on the pressure change of the gas chamber, unlike a failure-prone one such as a differential transformer, a simple pressure detector is provided on the cylinder,
Alternatively, a configuration in which a pipe is connected to a gas chamber and a pressure detector is provided in a portion where the impact is small, for example, is effective in minimizing electrical failure.

[Brief description of the drawings]

1 and 2 are longitudinal side views showing each embodiment of the present invention, FIG. 3 is a block diagram of a control system, FIGS. 4 and 5 are graphs showing pressure changes in gas chambers, and FIG. 5 is a graph showing a relationship between a flow rate and a hydraulic pressure. 1 ... Cylinder, 3 ... Large diameter part, 4 ... Piston, 5 ... Gas chamber, 6 ... Middle chamber, 7 ... Low chamber, 11 ... Drainage port, 12 ... Filling port, 20 ... ... Pressure adjustment chamber, 21 ... Piston as volume adjustment means, 23 ... Pressure chamber, 24 ... Switching valve, 25 ... Hydraulic unit, 28 ... Pressure unit, 30 ... Pressure detector, 38 ... …container.

Claims (2)

(57) [Claims] A piston having a large-diameter portion at an intermediate portion thereof is fitted in a cylinder, a lower chamber is provided at an inner periphery of the cylinder below the large-diameter portion of the piston, and the lower chamber rises in an upper portion of the cylinder. A gas chamber filled with gas compressed by the piston is provided, and the piston body is raised and lowered by hydraulic pressure, the piston is lowered by gas pressure, and the valve body for piston control is raised and lowered by switching the hydraulic pressure accompanying the raising and lowering of the piston. In the apparatus, a pressure adjusting chamber having a volume adjusting means is communicated with the gas chamber, a pressure detector is provided in the gas chamber, and a striking force and a striking force which control the volume adjusting means by a signal from the pressure detector are provided. Automatic control of the number of hits. 2. An amount of displacement of the piston when the piston strikes and repels a chisel provided below the piston is calculated by an arithmetic circuit which receives the output of the pressure detection chamber as an input, and the displacement is calculated based on the calculated value. 2. The automatic control device for the impact force and the number of impacts according to claim 1, wherein the control switching valve of the adjusting means is controlled.