JPS6234007Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a cylinder device equipped with a length measuring device for detecting the stroke of a piston.

For example, cylinder devices for driving the working mechanisms of construction machinery are equipped with a length measuring device that automatically detects the stroke of the piston in order to improve operability and enable automatic operation. is used.

A cylinder device equipped with the above-mentioned length measuring device, for example, as shown in FIG. 1, has been known in the past.

In the figure, 1 indicates a cylinder filled with hydraulic oil, and a head cover 1 is attached to the cylinder 1.
A and a rod cover 1B are provided, and each cover 1A, 1B has a supply/discharge port (not shown) formed therein, and both ends of the cylinder 1 are covered.
A piston 2 is slidably provided within the cylinder 1. One end of a piston rod 3 is fixedly attached to the piston 2, and the other end is made to protrude outside from the rod cover 1B.

Next, 4 is an ultrasonic transmitter, and 5 is an ultrasonic receiver. The ultrasonic transmitter 4 and the ultrasonic receiver 5 are arranged in parallel on the inner wall of the head cover 1A within the cylinder 1. Then, ultrasonic waves are transmitted from the ultrasonic transmitter 4 toward the end face of the piston 2 and reflected by the piston 2. This reflected wave is transmitted to the ultrasonic receiver 5.
The stroke of the piston 2 can be detected by measuring the time from the transmission to the reception.

In this type of cylinder device, the ultrasonic transmitter 4 and receiver 5 are designed so that they do not come into contact with or slide on the piston 2 or piston rod 3, so that failure of these devices and damage to the piston rod 3 etc. can be prevented, and they are adequately protected.

However, in the above-mentioned measurement method, the hydraulic oil in the cylinder 1 is used as a medium, so if bubbles are generated in the hydraulic oil due to cavitation or a gas phase is generated, errors may occur in the measured values. The drawback was that the attenuation of ultrasonic waves increased, making measurement impossible.

The present invention was devised in view of the above-mentioned problems of the prior art, and it operates by propagating ultrasonic waves using the piston rod as a medium and by using the liquid interposed between the ultrasonic transmitter and the piston rod as a contact medium. It is an object of the present invention to provide a cylinder device which eliminates the influence of air bubbles and the like existing in oil and enables accurate and reliable detection of a piston stroke in a non-contact state.

In order to solve the above problems, the present invention includes a cylinder, a piston slidably provided in the cylinder, one end fixed to the piston, and the other end protruding from the cylinder to the outside. A cylinder device comprising a piston rod, an ultrasonic transmitter provided on the rod cover side of the cylinder and arranged to face the circumferential wall of the piston rod in a non-contact state with a slight gap, and the ultrasonic transmitter. A liquid interposed as a contact medium in the gap between the piston rod and the piston rod, and a liquid provided on the piston rod at a protruding end side of the piston rod and propagated through the liquid as the contact medium and the piston rod as a medium. and an ultrasonic receiver that receives ultrasonic waves.

With this configuration, the signal from the ultrasonic transmitter is transmitted to the piston rod via the contact medium in a non-contact manner, generating a surface wave in the piston rod, and the surface wave propagates through the piston rod. , is received by an ultrasonic receiver and detected as a piston stroke.

Embodiments of the present invention will be described below with reference to FIGS. 2 to 5.

First, FIGS. 2 to 4 show a first embodiment of the present invention, and the same components as those in FIG. 1 are designated by the same reference numerals and their explanations will be omitted.
11 indicates an ultrasonic transmitter, and the ultrasonic transmitter 11
is attached to the inner wall of the cylinder 1 at a position close to the rod cover 1B. The ultrasonic transmitter 11 is disposed facing the piston rod 3 with a slight gap therebetween in a non-contact manner. Next, reference numeral 12 indicates an ultrasonic receiver attached to the piston rod 3, and the ultrasonic receiver 12 is installed on the piston rod 3 so as to be placed outside the cylinder 1 even when the piston rod 3 is fully inserted into the cylinder 1. It is provided at a position close to the mounting eye 3A.

Thus, a surface wave is generated in the piston rod 3 by the ultrasonic signal transmitted from the ultrasonic transmitter 11, this signal is received by the ultrasonic receiver 12, and the piston stroke is detected from the time from the transmission to the reception. It is configured as follows.
Since the ultrasonic transmitter 12 and the piston rod 3 are in a non-contact state, if there is an air layer between them, the ultrasonic waves will be attenuated and the piston rod 3 may not generate surface waves. Therefore, a contact medium is required between the ultrasonic transmitter 12 and the piston rod 3 to properly propagate the ultrasonic waves. In this embodiment, the hydraulic oil in the cylinder 1 is used as a contact medium by interposing the hydraulic oil between them. As a result, an ultrasonic propagation path is formed from the ultrasonic transmitter 11 to the ultrasonic receiver 12 via the hydraulic oil as a contact medium and the piston rod 3 as a medium.

Next, a specific example of a piston stroke detection device will be shown based on FIG.

Reference numeral 21 indicates a timer, and the timer 21 transmits an ultrasonic generation signal and a gate opening signal to the pulse transmitter 22 and the gate circuit 23 at regular intervals. When the pulse generator 22 receives the ultrasonic generation signal, the pulse generator 22 causes the ultrasonic generator 11 to emit ultrasonic waves at a constant period. On the other hand, the gate circuit 23 to which the gate open signal from the timer 21 is input opens the gate in response to the gate open signal, and when the received signal from the ultrasonic receiver 12 is input as the gate close signal via the amplifier 24. Close the gate. Reference numeral 25 denotes a clock pulse generator that always emits clock pulses, and the clock pulses from the clock pulse generator 25 are configured to be outputted to the counter circuit 26 via the gate circuit 23 while the gate is open.
The clock pulse generator 25 includes a piston rod 3.
A thermometer 27 is attached to detect the temperature of the
Therefore, the clock pulse generator 25 is connected to the temperature measuring device 27.
The clock pulse is transmitted every moment at a predetermined pulse period with the temperature corrected by . The reason why temperature correction is performed in this way is that the speed of sound changes depending on the temperature. Therefore, the counter circuit 26 counts the clock pulses from the clock pulse generator 25 in response to the gate open signal from the gate circuit 23, and stops counting the clock pulses when the gate close signal from the ultrasonic receiver 12 is input. The number of clock pulses thus counted is input to the display 28, and the display 28 converts the numerical value of the clock pulses thus input into a piston stroke amount and displays it.

The cylinder device according to the present invention has the above-mentioned configuration.Next, measurement of piston stroke will be explained with reference to FIG.

First, when a signal is sent by the timer 21,
This signal is transmitted from the ultrasonic transmitter 11 to the piston rod 3 via the pulse generator 22. At the same time, the signal from the timer 21 is also input to the gate circuit 23 to open the gate. As a result, the clock pulses from the clock pulse generator 25 are momentarily input to the counter circuit 26 via the gate circuit 23, and the number of the clock pulses is counted. In this case, the clock pulse generator 25
Since the clock pulses from the piston rod 3 are corrected by detecting the temperature of the piston rod 3 by the thermometer 27, even if there is a temperature change in the piston rod 3, no measurement error will occur.

On the other hand, the signal from the ultrasonic transmitter 11 is transmitted to the piston rod 3 via hydraulic oil as a contact medium. Then, a surface wave is generated in the piston rod 3, and the surface wave is transmitted to the piston rod 3.
propagate inside. The signal propagated in this manner is received by the ultrasonic receiver 12, amplified by the amplifier 24, and input to the gate circuit 23. This signal causes the gate circuit 23 to close, and the input of clock pulses to the counter circuit 26 is stopped. In this way, the period 1 in which the gate circuit 23 is maintained in an open state,
That is, the counter circuit 26 counts the number of clock pulses input to the counter circuit 26 during the period from when the ultrasonic wave is transmitted by the ultrasonic transmitter 11 until it is received by the ultrasonic receiver 12. This count value is then input to the display 28, where it is converted into a piston stroke and the amount is displayed.

As the piston 2 slides within the cylinder 1, its stroke changes, and along with this, the ultrasonic receiver 12 approaches and moves away from the ultrasonic transmitter 11. Since the signal from the timer 21 is generated at regular intervals, the piston stroke is measured each time, and the measured amount is displayed on the display 28.

Next, FIG. 5 shows a second embodiment of the present invention, in which the ultrasonic transmitter 11 is not provided within the cylinder 1. However, a casing 31 is fixed to the rod cover 1B of the cylinder 1 by means such as welding, and a sealed chamber 32 is formed within the casing 31. The piston rod 3 penetrates the sealed chamber 32 of the casing 31 and projects to the outside. Further, a liquid with high acoustic impedance such as an aqueous grease solution is sealed in the sealed chamber 32, and an ultrasonic transmitter 11 is attached to the inner wall of the casing 1 and faces the piston rod 3 with a slight gap. It is placed in a condition.

With the above configuration, the liquid with high acoustic impedance sealed in the sealed chamber 32 becomes a contact medium, and the amount of attenuation when the ultrasonic waves emitted from the ultrasonic transmitter 11 are transmitted to the piston rod 3 is small. As a result, ultrasonic propagation performance is significantly improved.

The cylinder device according to the present invention has been described in detail above, and has the following effects.

Since the piston rod is used as a medium for propagating ultrasonic waves, the attenuation of ultrasonic waves can be reduced, and the piston stroke can be measured satisfactorily and accurately.

Since a liquid serving as a contact medium is interposed between the ultrasonic transmitter and the piston rod, it is possible to measure the piston stroke without contacting or sliding the ultrasonic transmitter. You can prevent loss.

Ultrasonic attenuation can be further reduced by using a liquid with high acoustic impedance as a coupling medium.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a cylinder device showing the prior art, FIGS. 2 to 4 show a first embodiment of the present invention, FIG. 2 is a longitudinal sectional view of the cylinder device, and FIG. 3 is a longitudinal sectional view of the cylinder device. 4 is a circuit diagram showing a piston stroke detection device, FIG. 4 is an explanatory diagram regarding signals of the piston stroke detection device, and FIG. 5 is a longitudinal sectional view of a cylinder device showing a second embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Cylinder, 2... Piston, 3... Piston rod, 11... Ultrasonic transmitter, 12... Ultrasonic receiver, 31... Casing, 32... Sealed chamber.

Claims (1)

[Claims for Utility Model Registration] (1) A cylinder, a piston slidably provided within the cylinder, and a piston rod having one end fixed to the piston and the other end protruding from the cylinder to the outside. an ultrasonic transmitter provided on the rod cover side of the cylinder and arranged to face the circumferential wall of the piston rod in a non-contact state with a slight gap; the ultrasonic transmitter and the A liquid interposed as a contact medium in the gap between the piston rod and the piston rod, and an ultraviolet disposed on the piston rod located on the protruding end side of the piston rod and propagated through the liquid as the contact medium and the piston rod as a medium. A cylinder device comprising: an ultrasonic receiver that receives sound waves. (2) The cylinder device according to claim (1), wherein the liquid as the contact medium is hydraulic oil in the cylinder. (3) A sealed chamber through which the piston rod penetrates is provided on the rod cover side of the cylinder, and the ultrasonic transmitter is disposed in the sealed chamber, and a liquid with high acoustic impedance is sealed as the contact medium. A cylinder device according to claim (1) of the utility model registration claim.