JPH08201008A - Piston position detector for cylinder - Google Patents

Abstract

PURPOSE: To provide a piston position detector of a cylinder which is suitable for the detection of a neutral position or the like of a mast of a forklift. CONSTITUTION: This apparatus comprises a mobile bar 12 to be mounted on a piston rod of a hydraulic cylinder, a fixed bar 11 to be mounted on a guide member 13 being combined with the mobile bar 12 free to extend, a first magnet 15 mounted on the mobile bar 12, a second magnet 16 mounted on the fixed bar 11 free to turn, a spring for always energizing the second magnet 16 to the side of the mobile bar 12 and a control cable 26 having an internal rope 32 to be pushed or pulled according to the turning of the second magnet 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston position detecting device for a cylinder. More specifically, the present invention relates to a device that can be easily attached to an existing hydraulic cylinder or the like and that detects the position of its piston to generate a mechanical signal.
In this specification, the term "piston" is a concept including a plunger.

[0002]

2. Description of the Related Art Conventionally, in an air cylinder or the like, a cylinder body is made of a non-magnetic material such as an aluminum pipe, a magnet is embedded in a piston, and a magnetic field of the magnet is axially adjustable on the outer circumference of the cylinder. There is known a sensor-equipped cylinder that is provided with a reed switch that operates in a known manner and that can electrically detect a stroke end or a position in the middle of a stroke of a piston. On the other hand, a piston rod of an air cylinder or hydraulic cylinder is connected to a guide rod that moves in the axial direction together with the piston rod, a dog is attached to the guide rod so that the position can be adjusted, and a bracket that slidably guides the guide rod, etc. It is also known that a limit switch that operates in contact with the dog is provided to electrically detect the stroke end of the piston. In that case, if an overtravel type limit switch is used, the piston position during the stroke can be detected.

[0003]

The device using the above-mentioned reed switch cannot be applied to a cylinder using a normal steel pipe for the cylinder body or an existing cylinder. On the other hand, the one using the limit switch is not preferable because the dog impacts the lever of the limit switch or the like. In addition, for example, when a pin is provided on the knob of the operating lever for manually operating the valve for controlling the cylinder so that it can be retracted and retracted, and when the operator is informed of the specific piston position by retracting the pin, a control cable, When outputting a mechanical signal via the conventional electric detector, it is necessary to convert the output electric signal into a mechanical operation.

An object of the present invention is to provide a piston position detecting device which can be easily applied to a cylinder using a general steel pipe as a cylinder body or an existing cylinder. Another object of the present invention is to provide a piston position detecting device for a cylinder that outputs a mechanical signal and has a simple mechanism.

[0005]

A piston position detecting device for a cylinder according to the present invention is a piston position detecting device for a cylinder comprising a magnet provided on the piston side of the cylinder and a magnet detecting element provided on the cylinder body side. The magnet detecting element is rotatably provided between a position facing the magnet when the magnet on the movable element side passes and a position distant from the magnet, and the magnetic member is always The constitutional feature is that it is provided with an urging means for urging in a side opposite to the direction of attraction or repulsion by the magnet.

In such a device, a telescopic bar composed of a movable bar and a fixed bar made of non-magnetic material is connected between the tip of the piston rod and the cylinder body so as to extend and contract so as to guide each other. It is preferable that the magnet is attached to the movable bar in a region overlapping with the fixed bar, and the magnetic body is rotatably provided on the fixed bar. Furthermore, it is preferable that the magnetic body is provided on a lever that is provided so as to be rotatable about an axis that is lateral to the expansion and contraction direction of the cylinder. Further, it is preferable that a magnet, a magnetic body, or a lever is provided so that its position can be adjusted in the expansion / contraction direction of the cylinder. Further, a second magnet having the same polarity as that of the magnet on the piston side is adopted as the magnetic body, and a spring for constantly urging the second magnet to the side facing the magnet on the piston side is adopted as the urging means. Preferably. In that case, it is more preferable to provide a plate for attracting the second magnet at a position where the second magnet faces the piston-side magnet.

Further, an inner cable of a control cable extending in the extension / contraction direction of the cylinder may be attached to the magnetic body or lever. In that case, the other end of the inner cable can be connected to a pin provided on a knob of a manual operation lever that operates a valve for switching expansion and contraction of a cylinder so as to be retractable.

[0008]

In the apparatus of the present invention, when the piston expands and contracts, the magnet on the piston side also reciprocates in the expansion and contraction direction.
The magnetic body is normally biased by a biasing means to the side opposite to the direction in which it is attracted or repelled from the magnet. When the piston expands and contracts to reach a specific position where the magnet and the magnetic material approach each other, the magnetic material is attracted or repelled by the magnet and rotates to a position facing the magnet or a position away from the magnet. Therefore, it is possible to mechanically detect whether the piston is at a specific position or another position, depending on the rotational position of the magnetic body.

In the apparatus according to the second aspect, the telescopic bar expands and contracts according to the expansion and contraction of the piston. Then, whether or not the piston is at a specific position where the magnet of the movable bar approaches the magnetic body of the fixed bar can be detected from the rotational position of the magnetic body as described above. Further, in this device, since the magnet and the magnetic body are attached to the telescopic bar, the position detecting device can be handled as one unit. Claim 3
In the device, the magnetic body rotates together with the lever.
Therefore, regardless of the size of the magnetic body, a desired detection stroke for mechanical detection can be obtained at any position such as the extension of the lever.

In the apparatus of claim 4, the specific piston position to be detected can be adjusted arbitrarily. If a second magnet having the same pole as the piston side magnet is used as the magnet body as in the fifth aspect, a large force detection operation can be obtained. Second
When a plate for attracting the second magnet is provided at a position where the magnet of (1) faces the magnet on the piston side, the second magnet is brought into contact with the plate by its own attraction force in addition to the biasing force of the spring. Then, when the magnet on the piston side comes to the back side of the plate, it is repulsed sensitively. When the inner cable of the control cable is connected to the magnetic body or the lever as in the seventh aspect, the positional information of the piston can be mechanically and remotely output as the reciprocating movement of the cable. In the device according to the seventh aspect, the operator can recognize the piston position by the feel based on the movement or the pressing force of the pin attempting to protrude from the knob of the operation lever without looking at the display at hand. Moreover, since the operator constantly holds the knob of the valve control lever that operates the cylinder, the operator can reflexively stop the valve at a specific position, and the delay time can be reduced.

[0011]

Embodiments of the apparatus of the present invention will now be described with reference to the drawings. FIGS. 1, 2 and 3 are perspective views, side views and plan views, respectively, showing an embodiment of the apparatus of the present invention, FIG. 4 is a partial sectional plan view of the apparatus of FIG. 3, and FIG.
VV line sectional view, FIG. 6 is a VI-VI line sectional view of FIG. 4, FIG. 7 is a perspective view of main parts of the apparatus of FIGS. 5 and 6, and FIG. 8 is a schematic side view showing an example of a forklift to which the apparatus of the present invention is applied. FIG. 9, FIG. 9 is an enlarged perspective view of the operating lever of the forklift, FIG. 10 is a sectional view of the essential parts showing another embodiment of the device of the present invention, and FIG.
11 and 11b are graphs comparing the operation of the device of FIGS. 4 and 10.

The piston position detecting device 10 of FIG. 1 is mounted on the hydraulic cylinder 3 for controlling the inclination angle of the mast 2 of the forklift 1 of FIG. 8 to detect whether or not the mast 2 is at the neutral position. This is a fixed bar 1 to be attached to the cylinder body 4 of the hydraulic cylinder 3 shown in FIGS.
1 and a movable bar 12 attached to the piston rod 5. A first guide member 13 for slidably guiding the movable bar 12 is fixed to one end of the fixed bar 11, and a first guide member 13 for slidably guiding the fixed bar 11 is attached to one end of the movable bar 12. 2 The guide member 14 is fixed.
As a result, the fixed bar 11 and the movable bar 12 form a telescopic bar that can extend and contract so as to guide each other. Movable bar 12
The fixed bar 11 and the fixed bar 11 are both manufactured from a nonmagnetic plate such as austenitic stainless steel or aluminum alloy. The guide members 13 and 14 are made of synthetic resin or the like.

On the outer surface of the movable bar 12, the first magnet 1 is attached.
5 is mounted so that its position can be adjusted in the direction of expansion and contraction of the cylinder (direction of arrow AB). Further, as shown in FIG. 4, a second magnet 16 facing the first magnet 15 is provided on the outer surface of the fixed bar 11 so as to be rotatable around a shaft 17. In this embodiment, the shaft 17 is lateral to the direction of expansion and contraction of the cylinder. In FIG. 4, reference numeral 18 is a fixed bar 1.
It is a box-shaped case fixed to 1, and a lever 19 is housed inside the case 18 so as to be rotatable around a shaft 17. As shown in FIGS. 5 to 7, the lever 19 has a cylindrical support portion 21 into which a pin (or screw) 20 constituting the shaft 17 is fitted, and a width connected to the support portion via an arm 22. Is provided with a wide columnar magnet housing portion 23 and a narrow cable connecting portion 24 extending from the support portion 21 to the arm 22 at an obtuse angle, and is molded of synthetic resin as a whole. The second magnet 16 having a rectangular parallelepiped shape is housed in the magnet housing portion 23 together with a holder 25 having a U-shaped cross section for forming a magnetic path, and is fixed with an adhesive or the like.

As shown in FIGS. 4 and 5, the case 18 houses a wide front portion 18a forming a cavity in which the magnet housing portion 23 of the lever 19 can move, a cable connecting portion 24 and a cylindrical portion 21. And a narrow rear portion 18b that rotatably supports the cylindrical portion 21 by the pin 20. The conduit 27 of the push-pull control cable 26 is locked to the upper portion of the rear portion 18b of the case 18.
The upper end opening of the case 18 is covered with a cover 29 via a gasket 28. As shown in FIG. 6, the case 18 is provided with four projections 30 projecting from the side surface thereof, and the projections 30 are utilized to stop the case 18 from the outside of the fixed bar 11 with screws 31. The inner cable 32 of the push-pull control cable 26 is fixed to the end of the cable 32 by means of a locking metal fitting 32a.
Is locked at the upper end of. Further, a tension coil spring 33, which is a biasing means, is stretched between the upper end of the cable connecting portion 24 and the front end of the case 18.

The first magnet 15 is a rectangular parallelepiped having the same shape as the second magnet 16, and is housed in a prismatic storage case 34 together with a holder 25 having a U-shaped cross section for forming a magnetic path, and is fixed with an adhesive material. ing. That is, each magnet 15, 16
Is closed magnetic path by the holder 25, so that the magnetic flux does not leak to the outside. As shown in FIGS. 6 and 10, a hook-shaped cut-and-bend portion 25 a is formed on a part of the holder 25.
And the magnet storage 23 and the storage case 3
The inner surface of 4 may be made to bite so as not to come off. The shape of the magnet is not particularly limited, and may be cylindrical or the like. In this embodiment, the first magnet 15 and the second magnet 16 are arranged so that the same magnetic poles face each other, for example, the N poles face each other, that is, the repulsive force acts.
The storage case 34, as shown in FIGS. 6 and 7,
By using the four protrusions 35 protruding to the side surface, the movable bar 1
It is fixed with screws 31 from the outside of 2. The movable bar 12
An elongated hole is provided in the rising portion 12a of the cylinder so that the mounting position can be adjusted in the expansion and contraction direction of the cylinder. In this embodiment, the other end of the conduit 27 of the control cable 26 is connected to the guide pipe 36, and the other end of the inner cable 32 is connected to the pin 37 slidably accommodated in the guide pipe 36. ing. The case 18 is omitted in FIG. 7.

In the device 10 constructed as described above, the piston rod 5 of the hydraulic cylinder 3 is moved to move the first magnet 1
When 5 and the second magnet 16 face each other as shown in FIG. 4, the repulsive force between the magnets 15 and 16 causes the lever 19 to rotate around the shaft 17 in the arrow C direction (see the imaginary line). As a result, one end of the inner cable 32 of the control cable 26 is pushed to cause the pin 37 to project from the guide pipe 36. That is, the lever 19 changes the direction of movement of the second magnet 16 by 90 °.
It acts as a converting bell crank. When the piston rod 5 further moves and the first magnet 15 passes the position of the second magnet 16, the pulling force of the spring 33 causes the lever 19 to rotate in the direction opposite to the arrow C. Thereby, inner line 3
2 is drawn into the case 18, and the pin 37 is drawn into the guide pipe 36.

Therefore, for example, by matching the position where the first magnet 15 and the second magnet 16 coincide with each other with the mast 2 of the forklift 1 shown in FIG. 8 at an intermediate position, that is, the fork 6 is horizontally oriented. It is possible to configure a mast neutral position detecting device in which the pin 37 projects when the position reaches the intermediate position. When the pin 37 is embedded in the knob 8 of the valve switching operation lever 7 for controlling the hydraulic cylinder 3 shown in FIGS. 8 and 9, for example,
The operator can sense the protrusion of the pin 37 by feeling the skin of the hand holding the operation lever 7. Therefore mast 2
Even if you are not able to see the fork 6 enough due to obstacles such as, or keep an eye on the cargo on the fork,
It can be recognized that the tip of the fork 6 is oriented horizontally. This eliminates the accident of hooking the fork tip on the pallet.

It is usually about 0.2 to 0.4 sec until the operator senses the protrusion of the pin 37 and then operates the operation lever 7 to the neutral position (in the case of the center close valve) to stop the operation of the hydraulic cylinder 3. There is a delay.
However, when the operator finely adjusts the expansion and contraction of the hydraulic cylinder in order to erect the mast 2, the piston speed is about 30 mm / sec, so a hysteresis stroke of about 6 to 12 mm is sufficient. Further, when the appearance of the pin is detected by the feel of the operator's hand, it is preferable to give spring action to the operation of the pin 37 and lengthen the stroke because the pain sensation of the palm is dull and the skin is weak. The detection device using the magnet is suitable because it has a spring property due to the repulsive force (or attraction force) of the magnet and can increase the operation stroke. It should be noted that, for example, when the operator strongly grips the knob 8, the pin does not come out, but a signal can be transmitted to the operator by a point-like pressing force.

In the above-mentioned embodiment, the repulsive force of the same pole of the pair of magnets is used to detect the specific operating position of the cylinder (the intermediate position of the mast), but it is also possible to use the attracting action. . In that case, the second magnet may be always rotated upward by a spring so that when the first magnet faces the second magnet, the second magnet descends to push out the inner cable. Even in that case, the effect of the spring property and the long stroke is exhibited. When utilizing the attractive force, a magnetic material such as iron can be used in place of either the second magnet or the first magnet. In addition, in order to reduce the above-mentioned hysteresis stroke, it is preferable that the rising characteristic of sensing is an acute angle. However, since the falling side is the release direction, an obtuse angle may be used. From this point of view, it is preferable to use the repulsive force of the magnet as the actuating force and use the spring at the time of returning as in the embodiment.

In the above-mentioned embodiment, the case where the signal is transmitted to the feel of the palm of the operator by the protruding and retracting of the pin has been described.
A sensor such as a limit switch or a proximity switch may be turned on and off by a pin that appears and disappears depending on a cable. Further, it is also possible to directly input to those sensors by a rotating lever (19 in FIG. 4).
In those cases, an electric signal can be output. In some cases, the direction switching valve for controlling the cylinder may be automatically operated to automatically control the piston position based on a mechanical signal or an electrical signal from the inner cable of the control cable. In that case, it is preferable to employ a servo valve that operates according to the angle of the lever 19 in the hydraulic circuit. Further, in the above embodiment, the tension coil spring is used as the means for urging the lever, but a compression spring may be used.

Further, as shown in FIG. 10, a magnetic body, such as a steel plate 38, which produces an attractive force between the bottom surface of the case 18 and the second magnet may be interposed to serve as the urging means. In this embodiment, when the first magnet 15 is not in the position facing the second magnet 16, the second magnet 16 is attracted to the plate 38 in addition to the urging force of the spring 33, so that the bottom side of the case 18 is Is urged by. Then, when the first magnet 15 comes to a position where it opposes, the first magnet 15 rotates like an imaginary line by the repulsive force. It should be noted that, once separated from the bottom of the case 18, the suction effect of the plate 38 sharply decreases. Also, when the first magnet 15 passes by, it returns with a strong force. Therefore, as shown in FIG. 11b, the rising and falling characteristics of sensing are steeper as compared with the case where there is no plate (FIG. 11a).

Furthermore, the device of the present invention can be used not only for detecting the piston position during the stroke but also for detecting one or both stroke ends. In that case, one or two first magnets may be attached to the corresponding positions of the movable plate. In addition to forklifts, it can be applied to various work machines, industrial robots, and other piston (including plunger) position detection devices such as hydraulic or air cylinders.

[0023]

The structure is simple because it can be easily attached to various existing cylinders. Since the repulsion or adsorption force of the magnet is used in the detection part, it has a spring property and a large detection stroke.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the device of the present invention.

FIG. 2 is a side view of the device.

FIG. 3 is a plan view of the device.

FIG. 4 is a partial cross-sectional plan view of FIG.

5 is a sectional view taken along line VV of FIG.

6 is a sectional view taken along line VI-VI of FIG.

7 is a partial cutaway perspective view of the device of FIGS. 5-6. FIG.

FIG. 8 is a schematic side view showing an example of a forklift to which the device of the present invention is applied.

FIG. 9 is a partially enlarged perspective view of an operation lever of the forklift truck.

FIG. 10 is a cross-sectional view of essential parts showing another embodiment of the device of the present invention.

11a and 11b are graphs conceptually showing a comparison of operating states of a device without a plate and a device with a plate, respectively.

[Explanation of symbols]

 3 Hydraulic Cylinder 4 Cylinder Body 5 Piston Rod 7 Operating Lever 8 Knob 10 Position Detecting Device 11 Fixed Bar 12 Movable Bar 15 First Magnet 16 Second Magnet 17 Axis 19 Lever 26 Control Cable 27 Conduit 32 Inner Cable 33 Spring 37 Pin 38 Plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Fumio Ikesugi 110 Yokokura Nitta 110, Oyama City, Tochigi Prefecture Komatsu Forklift Co., Ltd. Tochigi Plant

Claims (8)

[Claims] 1. A magnet provided on the piston side of a cylinder,
A piston position detection device for a cylinder comprising a magnet detection element provided on the cylinder body side, wherein the magnet detection element faces a magnet when the magnet on the piston side passes, and a position separated therefrom. A piston position detecting device for a cylinder, comprising: a magnetic body rotatably provided between the two and a biasing means for constantly biasing the magnetic body in a direction opposite to the direction of attraction or repulsion by a magnet. 2. A telescopic bar made up of a non-magnetic movable bar and a fixed bar, which are connected to each other so as to extend and contract so as to guide each other, is stretched between the tip of the piston rod and the cylinder body. The apparatus according to claim 1, wherein the magnet is attached to a region of the movable bar that overlaps with the fixed bar, and the magnetic body is rotatably provided on the fixed bar. 3. The device according to claim 1, wherein the magnetic body is provided on a lever that is provided so as to be rotatable about an axis that is lateral to the expansion / contraction direction of the cylinder. 4. The apparatus according to claim 1, 2 or 3, wherein the magnet, the magnetic body or the lever is provided so that the position of the magnet or the lever can be adjusted in the extension and contraction direction of the cylinder. 5. The magnetic body is a second magnet having the same polarity as the magnet on the piston side, and the biasing means constantly biases the second magnet to the side facing the magnet on the piston side. 5. The device of claim 1, 2, 3 or 4 which is a spring. 6. The apparatus according to claim 5, wherein a plate for attracting the second magnet is provided at a position where the second magnet faces the magnet on the piston side. 7. The device according to claim 1, wherein an inner cable of a control cable extending in the expansion / contraction direction of the cylinder is attached to the magnetic body or lever. 8. The other end of the inner cable is connected to a pin provided so as to be retractable with respect to a knob of a manual operation lever that operates a valve for switching expansion and contraction of a cylinder.
The described device.