JPH055603A - Stroke detector of piston - Google Patents

Abstract

PURPOSE:To obtain a stroke detector for a piston which allows accurate detection of the behavior of the piston in an engine in which the piston reciprocates within a cylinder under severe application conditions, for example, rock drill. CONSTITUTION:As a piston 28 reciprocates, magnetism from a disc-shaped magnet 32 provided on the base end face thereof is detected with a plurality of magnetic sensors 34 arranged on the inner circumference 24a of a cylinder at an equal interval in the direction of the axis line thereof. Based on a detection signal, the position of the piston 28 in the direction of stroke and the speed thereof are calculated with a stroke computing circuit 36. The use of the magnet 32 allows the formation of an intense magnetic field not available with a mere magnetic recording layer or the like thereby enables magnetic detection at a level high sufficiently even though the interval may be widened to a certain extent between the magnetic sensor 34 and the piston 28.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston stroke detection device for detecting the position of the piston in the stroke direction in an engine in which the piston reciprocates in a cylinder.

[0002]

2. Description of the Related Art A rock drill is one of the engines in which a piston reciprocates in a cylinder.
Drilling conditions differ depending on the rock quality of the target rock, and there is a problem that the hydraulic pressure for rock drilling must be adjusted to an appropriate hydraulic pressure for each rock to respond to different rock quality. .. In addition, a rock drilling machine is required to timely detect abnormalities of the rock drilling machine centering on the hydraulic system such as breakage of the accumulator during drilling, but conventionally, it is possible to detect minute abnormalities. There is a problem that it is difficult and as a result causes a large failure. In order to solve these problems, the behavior of the piston that strikes the shank rod or the valve of the hydraulic system (position information, preferably speed information) is directly detected, and the hydraulic pressure is controlled or abnormality is detected based on it. It is desirable to

[0003]

However, it has been extremely difficult to directly detect these behaviors because the rock drilling machine is sometimes used under severe conditions. For example, as a means for detecting such behavior, a distance measurement using a laser is applied, that is, as shown in FIG. 6, a photosensor using a laser diode 2 as a light source and a photodiode 4 as a light receiving portion. 6 is provided in the cylinder 10 so as to face the end surface of the piston 8, the distance between the photo sensor 6 and the end surface of the piston 8 is detected at high speed, and position information and speed information are calculated from the amount of change in distance. However, with such an optical detection means,
There is a problem that it is difficult to detect accurately because it is easily affected by vibration of a rock drill and dust.

Such a problem is not limited to the rock drilling machine, but may occur in other machine tools and the like.

In the case of a rotary displacement like a drum, rather than a stroke displacement like a piston, a drum outer circumference is conventionally disclosed, for example, in Japanese Patent Laid-Open No. 63-253219. It is known that magnetic recording is performed on the surface in the circumferential direction, a magnetic resistance element is provided so as to be close to the outer peripheral surface of the drum, and the rotational displacement of the drum is detected by the magnetic resistance element.

It is also conceivable to apply such detection means to the stroke detection of the piston. That is, magnetic recording is performed on the outer peripheral surface of the piston in the axial direction thereof, and a magnetic resistance element is provided on the inner peripheral portion of the cylinder so as to be close to the outer peripheral surface of the piston, and the stroke displacement of the piston can be detected by this magnetic resistance element. Conceivable.

However, when position detection is performed using such a so-called magnetic scale, the magnetic field strength formed by the magnetic recording portion on the outer peripheral surface of the piston is weak, so that the gap between the magnetoresistive element and the piston is small. Is required to be extremely small, and it is difficult to apply it to a rock drilling machine, which is greatly affected by vibration and dust.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a piston stroke detection device capable of accurately detecting the behavior of a piston even under severe operating conditions. It is intended.

[0009]

A piston stroke detecting apparatus according to the present invention achieves the above object by providing a magnet in the piston and a plurality of magnetic sensors in a predetermined arrangement on the inner peripheral portion of the cylinder. It was done like this.

That is, in an engine in which a piston reciprocates in a cylinder, a device for detecting the position of the piston in the stroke direction, wherein a magnet provided on the piston and an inner peripheral portion of the cylinder are provided. A plurality of magnetic sensors arranged at predetermined intervals in the axial direction of the cylinder at a portion facing the magnet when the piston reciprocates; And a stroke calculation means for calculating the position in the stroke direction in the cylinder.

The above-mentioned "piston" is not particularly limited as long as it is used in "an engine in which a piston reciprocates in a cylinder". For example, a piston for hitting a shank rod in a rock drilling machine is used. Power pistons, hydraulic spool valves for operating the power pistons, and the like.

[0012]

As described above, when the piston reciprocates, the magnetism provided by the piston causes a plurality of magnets arranged in the cylinder inner peripheral portion at predetermined intervals in the axial direction thereof. Is detected by the magnetic sensor, and the position of the piston in the stroke direction is calculated by the stroke calculation means based on the detection signal.

As described above, according to the present invention, since the position is detected by the magnetic means, the piston position is detected under the harsh conditions of use as compared with the case where the position is detected by the optical means. Is possible. Moreover, in that case, since a magnet is used, a strong magnetic field that cannot be obtained by a simple magnetic recording layer or the like can be formed. Therefore, even if the distance between the magnetic sensor and the piston is widened to a certain extent, it is sufficiently high. Since it is possible to detect magnetism at the level, vibration,
The piston position can be detected without being affected by dust or the like.

Therefore, according to the present invention, the behavior of the piston can be accurately detected even under severe usage conditions.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram showing an embodiment of a stroke detecting device for a piston according to the present invention.

This piston stroke detecting device 20
Is provided in the rock drill 22, so the rock drill 22 will be described first. The rock drill 22 has a main body 24
A piston 28 is inserted through a hydraulic cylinder chamber 26 formed in the (cylinder), and the piston 28 is reciprocated by supplying / discharging hydraulic pressure to / from the hydraulic cylinder chamber 26. The shank rod (not shown) arranged in (1) is hit to perform rock drilling.

A detection cylinder chamber 30 is formed in the main body 24 in series with the hydraulic cylinder chamber 26, and the base end of the piston 28 is located in the detection cylinder chamber 30. .. A disc-shaped magnet 32 having substantially the same diameter as that of the piston 28 is attached to the base end surface of the piston 28. The magnet 32 is composed of a flat permanent magnet such as a magnet sheet.

A plurality of magnetic sensors 34 are provided on the inner peripheral portion 24a forming the peripheral wall of the detection cylinder chamber 30 of the main body 24.
(AK) are provided. These magnetic sensors 34
Is an induction type magnetic head or a magnetoresistive element, and is located in a portion of the inner peripheral portion 24a facing the magnet 32 when the piston 28 reciprocates.
They are arranged in an array at equal intervals in the axial direction of 0. The piston 28 will not only reciprocate but also rotate. However, since the magnet 32 is formed in a disk shape, the magnet 32 faces the magnetic sensor 34 even if the piston 28 rotates. It will be.

The magnetic sensors 34 are the same as the magnetic sensors 3
When the piston 28 passes in the vicinity of 4, the pulse is output as a detection signal. For example, when the piston 28 moves to the left in FIG. 1, detection signals as shown in FIG. 2 are sequentially output from each magnetic sensor 34.

The detection signal output from each of these magnetic sensors 34 is input to the stroke calculation circuit 36 (stroke calculation means) shown in FIG. In this stroke calculation circuit 36, the position of the magnet 32, that is, the position of the piston 28 in the stroke direction is calculated by determining which magnetic sensor 34 receives the signal, and the distance between the magnetic sensors 34 is calculated. Is known, the speed of the magnet 32, that is, the speed of the piston 28 is calculated from the input time difference Δt of the detection signals from the two adjacent magnetic sensors 34, and these are output as a stroke signal and a speed signal. ing.

FIG. 3 is a block circuit diagram showing the stroke calculation circuit 36, and FIGS. 4 and 5 are waveform diagrams showing its operation.

As shown in FIG. 3, the stroke calculation circuit 3
6 is a signal conditioner 38 and a signal amplifier 40.
An adder 42, a peak hold circuit 44, an adder 46, and an F / V converter 48.

The signal conditioners 38 are provided in the same number as the magnetic sensors 34, perform waveform shaping on the detection signals (FIG. 4A) from each magnetic sensor 34, and equalize the voltage when the magnets 32 pass. Pulse signal (FIG. 4B) is output. These pulse signals are input to the signal amplifiers 40, respectively, and the gain E (FIG. 4C) in these signal amplifiers 40 has the same output voltage between the signal amplifiers 40 as shown in FIG. 5A. It is set to increase (or decrease) at intervals. That is, at the timing when the magnet 32 passes through each magnetic sensor 34, the pulse signal of the voltage corresponding to the position is output. Then, each of these pulse signals is input to each peak hold circuit 44.

Further, each of the above signal conditioners 38
The pulse signal output from is input to the adder 42, and a continuous pulse signal is output from the adder 42 (FIG. 5B). This continuous signal is input to each peak hold circuit 44 and acts as a reset signal for these peak hold circuits 44.

Each of the signal amplifiers 40 is provided with a delay circuit (not shown) so as to generate a slight delay δ as shown in FIG. 4 (c). As a result, each peak hold circuit 44 holds the voltage set by each signal amplifier 40 until the next reset signal is input. The signal from each peak hold circuit 44 is input to the adder 46, and a stepwise voltage is output with respect to the position of the magnet (FIG. 5 (c)). This output becomes the stroke signal.

On the other hand, by inputting the output of the adder 42 (FIG. 5B) to the F / V converter 48, a voltage corresponding to the pulse interval is output. This output becomes the speed signal.

As described above in detail, according to this embodiment,
When the piston 28 reciprocates, magnetism from a magnet 32 provided on the base end surface of the piston 28 causes a plurality of magnetic sensors 3 to be arranged on the cylinder inner peripheral portion 24a at equal intervals in the axial direction.
4 and the stroke calculation output circuit 36 calculates the position and speed of the piston 28 in the stroke direction based on the detection signal.

As described above, in the present embodiment, since the position and speed are detected by the magnetic means, the position and speed are detected under the harsh conditions of use as compared with the case where the position and speed are detected by the optical means. The piston position and speed can be detected. Moreover, at this time, since the magnet 32 is used, a strong magnetic field that cannot be obtained by a simple magnetic recording layer or the like can be formed. Therefore, even if the distance between the magnetic sensor 34 and the magnet 32 is widened to some extent. Since the magnetism can be detected at a sufficiently high level, the piston position and the piston speed can be detected without being affected by vibration, dust and the like.

Therefore, according to this embodiment, the behavior of the piston 28 can be detected extremely accurately even under severe usage conditions.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a piston stroke detection device according to the present invention.

FIG. 2 is a waveform diagram showing detection signals from each magnetic sensor of the above embodiment.

FIG. 3 is a block circuit diagram showing a stroke calculation circuit of the above embodiment.

FIG. 4 is a waveform chart showing the operation of the above embodiment.

FIG. 5 is a waveform diagram showing the operation of the above embodiment.

FIG. 6 is a view similar to FIG. 1, showing a conventional example.

[Explanation of symbols]

 20 Stroke Detection Device 22 Rock Drilling Machine 24 Main Body (Cylinder) 24a Inner Circumference 28 Piston 30 Cylinder Chamber for Detection 32 Magnet 34 Magnetic Sensor 36 Stroke Calculation Circuit (Stroke Calculation Means)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenichiro Egusa 3-1, Shinchi Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (72) Inventor Takashi Higaki 2-1-2, Niho, Minami-ku, Hiroshima-shi, Hiroshima Within Tsuda Astec Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. In an engine in which a piston reciprocates in a cylinder, a device for detecting the position of the piston in the stroke direction, the magnet being provided in the piston,
A plurality of magnetic sensors arranged at predetermined intervals in the axial direction of the cylinder in a portion of the inner peripheral portion of the cylinder facing the magnet when the piston reciprocates, and detection from these magnetic sensors A stroke detection device for a piston, comprising: stroke calculation means for calculating the position of the piston in the stroke direction in the cylinder based on a signal.