JPH08170932A - Impact force measurement method for impact power tool - Google Patents

Abstract

PURPOSE: To provide a measurement method which accurately measures impact force of an impact power tool. CONSTITUTION: The lower part of a piston 12 is inserted into a cylinder 11 while free sliding is allowed, and a fluid is fed and sealed up in a pressure chamber 16 formed between the lower end of the piston 12 and the lower part stop end. The pressure change in the fluid when the piston 12 is hit with an impact power tool 1 is converted into electricity quantity by a pressure change device 17 connected to the pressure chamber 16, so that impact force of the impact power tool 1 is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring method for measuring the impact force of an impact moving tool such as a hydraulic breaker.

[0002]

2. Description of the Related Art A chisel slidably attached to the lower part of a cylinder is pressed against an object to be crushed such as a roadbed, and a piston incorporated slidably inside the cylinder strikes the upper end of the chisel to crush the object. Hydraulic breakers for crushing are known from the past.

Since there are various hydraulic breakers having different impact forces, it is necessary to select a hydraulic breaker having an optimum ability in accordance with the hardness of the crushed object in use.

As a method of evaluating the performance of this hydraulic breaker, a method of comparing impact forces is generally used.

As a method for measuring the impact force of a hydraulic breaker, a strain gauge is attached to the outer circumference of a metal rod, the rod is hit with a hydraulic breaker, and the electrical resistance change of the strain gauge is measured with a measuring instrument. Is conventionally known.

[0006]

By the way, in the above measuring method, since the rod is made of metal and the propagation speed of the stress wave generated by the impact of the rod is extremely fast, a measuring instrument with high responsiveness is provided. It is necessary and is difficult to measure in the field.

Further, since the propagation speed of the stress wave is high, when the length of the bar is short, the stress wave generated when the bar is hit and the stress wave reflected from the lower end surface of the bar interfere with each other. Then, the impact force cannot be accurately measured. For this reason, it is necessary to use an extremely long bar, which causes a problem of difficulty in handling.

Further, since the impact force of the hydraulic breaker is extremely large, it is difficult to secure the durability of the strain gauge.

An object of the present invention is to provide a measuring method capable of accurately and easily measuring the impact force of an impact moving tool such as a hydraulic breaker in the field.

[0010]

In order to solve the above-mentioned problems, according to the present invention, the lower end of a piston is slidably inserted into a cylinder and is formed between the lower surface of the piston and the lower closed end of the cylinder. The fluid is enclosed in the pressure chamber, and the pressure of the fluid when the impact tool strikes the piston is converted into an electric quantity by the pressure converter connected to the pressure chamber to measure the impact force of the impact tool. It is configured.

[0011]

As described above, by striking the piston with the impact tool, the impact force propagates through the piston and is transmitted to the fluid enclosed in the pressure chamber, so that a stress wave is generated in the fluid. Since the propagation speed of stress waves in a fluid is slower than the propagation speed of stress waves in metal, the pressure of the fluid can be reliably detected by the pressure transducer, and the impact motion tool can be detected from the electrical signal output from the pressure transducer. The impact force of can be measured.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows a state in which an impact force of a hydraulic breaker 1 as an impact tool is being measured by a measuring device 10.

In the hydraulic breaker 1, a piston 3 is slidably incorporated in a cylinder 2, the piston 3 is rapidly lowered, and an upper end of a chisel 4 provided below the piston 3 is hit.

The measuring device 10 has a cylinder 11, and a piston 12 is slidably inserted into the cylinder 11.

A piston cover 13 is fitted on the upper end of the piston 12. Further, a seal groove 14 is provided on the outer circumference of the piston 12, and a seal ring 15 attached to the seal groove 14 is pressed against the inner circumference of the cylinder 11 to seal between the sliding surfaces of the cylinder 11 and the piston 12. .

A pressure chamber 16 is formed between the lower end surface of the piston 12 and the lower closed end of the cylinder 11, and the pressure chamber 16 is filled with a fluid. A pressure converter 17 is connected to the lower part of the peripheral wall of the pressure chamber 16.

When the piston cover 13 is hit by the hydraulic breaker 1, the impact force is transmitted to the piston 12 and is transmitted to the fluid in the pressure chamber 16 as spike pressure.

FIG. 2 shows an example of spike pressure generated in the fluid in the pressure chamber 16. The hydraulic breaker 1 strikes the piston cover 13 once to generate a plurality of spike pressures. This is because the pressure wave reciprocates in the fluid.

The spike pressure generated by the impact of the hydraulic breaker 1 is converted into an electric quantity by the pressure converter 17. The signal detected by the pressure converter 17 is sent to the data processing unit 20.

In the data processing unit 20, the electric signal sent from the pressure converter 17 is amplified by the amplifier 21, and the amplified signal is sent to the microprocessor 22 via the A / D converter and sample hold not shown. ing.

The microprocessor 22 extracts and stores the maximum value for each hit of the hydraulic breaker 1, and when the preset number of hits is reached, calculates the average value of the maximum pressures.
The average value is displayed on the display unit 23.

The average maximum value displayed on the display unit 23 is proportional to the impact force of the hydraulic breaker 1. Therefore,
By comparing the average maximum values, it is possible to compare the capabilities of different hydraulic breakers.

In the measurement of the impact force as described above, it is possible to use gas as the fluid, but the sealing mechanism becomes difficult. In addition, since gas is highly compressible, it is difficult to evaluate it after pressure measurement.

Therefore, it is preferable to use a fluid having a low compressibility and a high viscosity that facilitates sealing. But,
If the viscosity is too high, the measurement becomes rather difficult.

Therefore, it is preferable that the fluid has a viscosity of about 60 Saybolt universal seconds at 38.degree.

When a petroleum-based industrial hydraulic oil is used as the fluid, the contact portion between the piston 12 and the cylinder 11 can be lubricated, so that the frictional resistance when the piston 12 moves can be reduced and the impact of the hydraulic breaker 1 can be reduced. The force can be transmitted to the fluid in the pressure chamber 16 without loss, and the measurement accuracy can be improved.

[0028]

As described above, according to the impact force measuring method of the present invention, the impact force when the impact tool strikes the piston is propagated to the fluid enclosed in the pressure chamber, and the pressure of the fluid is reduced. Is detected by the pressure converter and converted into the amount of electricity, the impact force of the impact tool can be measured accurately and reliably.

As a measuring device, a lower part of a piston is slidably inserted into a cylinder, a pressure chamber formed between a lower end of the piston and a closed end of the cylinder is filled with a fluid, and a pressure is applied to the pressure chamber. Since it is possible to use a small-sized one having a simple structure in which a converter is connected, it is possible to measure the impact force of the impact tool in the field.

In FIG. 1, the measuring device 10 is shown to be larger than the hydraulic breaker 1, but the actual size is much smaller than the hydraulic breaker and is about a fraction of the hydraulic breaker. Is.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a measuring device used in a method according to the present invention.

FIG. 2 is a diagram showing the measurement results of the impact force of the impact tool.

[Explanation of symbols]

 1 Hydraulic Breaker 11 Cylinder 12 Piston 16 Pressure Chamber 17 Pressure Transducer

Claims (1)

[Claims] 1. A lower end portion of a piston is slidably inserted into a cylinder, a fluid is enclosed in a pressure chamber formed between a lower surface of the piston and a lower closed end of the cylinder, and an impact working tool inserts the piston into the cylinder. A method for measuring an impact force of an impact dynamic tool, which comprises measuring the impact force of an impact dynamic tool by converting the pressure of a fluid when it is impacted into an electric quantity by a pressure converter connected to the pressure chamber.