JP2003156304A - Position detector in fluid pressure cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position detector in a fluid pressure cylinder, having a simple structure and being easily miniaturized, which can easily cope with a place requiring a hard temperature condition, and has little fluctuation of an output by external magnetism, and then is simply manufactured. SOLUTION: A capacitor 4 is charged or discharged, by periodically applying a pulse shaped voltage to a coil 1, which is arranged so that the position detection in the fluid pressure cylinder so that can capture changes in a polymerization part with a conductor 2, a magnetic substance, or non-magnetic conductor. The time interval until the voltage at the discharging exceeds the threshold of a comparator 5 is converted into a voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switch output when a voltage or current is output according to the movement of a cylinder rod, or when the movement of the cylinder rod is sensed to determine whether or not it is in a predetermined position. A position detector in a fluid pressure cylinder used for applications where it is generated.

[0002]

2. Description of the Related Art One example of a conventional position detector for a fluid pressure cylinder is, as shown in FIG. 11, a magnet (19) built in a piston (11) and a Hall element or the like for detecting the magnetic force. The magnetic sensor (20) that had been installed on the cylinder tube (18)
The position detection is performed at a fixed position of the magnetic sensor (20), which is arranged outside the.

In another example, a differential transformer or the like is used for axial position detection, but since the potentiometer is of a sliding type, the sliding portion is worn and there is a problem in long-term use. Usually uses three or more coils, so the shape is complicated and the external shape is large, and there are restrictions on where to attach.

[0004]

SUMMARY OF THE INVENTION In the first example above,
Magnetic sensor (20) on the outside of the cylinder tube (18)
For mounting a cylinder with a cylinder tube (18) having an inner diameter of 6 mm, the width is 10 mm and the height is 20 m.
It required a mounting space of about m and could not be used in a narrow space below that space. Further, for a cylinder having an inner diameter of 6 mm or less, it is difficult to incorporate a magnet, and a mounting space that is too large as compared with the cylinder is required, so that its use was limited.

Furthermore, since the magnetic force of the magnet (19) attached to the piston (11) is sensed from the outside of the cylinder tube (18), when the cylinders are installed close to each other, they are built in adjacent cylinders. Since it was affected by the magnet, it was necessary to install it at a certain distance. Moreover, it could not be used in an environment with a strong external magnetic field.

Further, in the case of other differential transformers, since the two detection coils are arranged coaxially in order to perform differential coupling also for temperature compensation, the total length should be at least twice the detection distance. It is necessary, and because it uses a total of three coils including the exciting coil, it is not suitable for downsizing, and there is a problem that it is subject to geometrical restrictions in small equipment and places with a small installation space. Therefore, since a magnetic material is used, there is a problem that it is easily affected by external magnetism.

In view of the problems of the conventional position detector for a fluid pressure cylinder, the present invention is compact, eliminates non-contact or sliding parts, and has little change in output due to temperature change or the influence of external magnetism. It is an object of the present invention to provide a position detector for a fluid pressure cylinder which is simple.

[0008]

In order to achieve the above object, a position detector for a fluid pressure cylinder of the present invention, as shown in FIG. 1 or 8, has a coil and a conductor (or a magnetic substance or a non-magnetic substance). A displacement detection unit made of a conductor, a resistor, a capacitor, a comparator or a fixed frequency pulse oscillator, a voltage trigger unit, an oscillation period voltage conversion unit (21), and the like.

The position detector for the fluid pressure cylinder has a shape in which a conductor (or a magnetic body) is installed on the outer (or inner) side of the coil as shown in FIGS. 1, 3, 4 and 5. Figure 2
Also, as shown in FIG. 6, there is a shape in which a non-magnetic conductor is placed outside the coil.

The relative positions of the coil and the conductor (or magnetic body) are such that the conductor (or magnetic body) passes outside the coil (FIGS. 1 and 5) and inside the coil the conductor (or magnetic body). ) Pass through (FIGS. 3 and 4).

Here, two types of circuits are shown as the circuits for detecting the change in the inductance of the coil, as shown in FIGS. The same idea is used in both methods to capture the change in coil inductance with time, but the oscillation circuit applied to the coil and the extraction time (duty)
The position is different.

The comparator used in the pulse output circuit is an inverted output comparator. When the input voltage rises from a low voltage, it outputs a high level until the threshold is exceeded, and when it exceeds the threshold, it outputs a low level. Output level. Also,
When the input voltage drops from the high voltage side, it outputs a low level until it exceeds the threshold value, and outputs a high level when it exceeds the threshold value. Moreover, by providing the threshold with hysteresis, continuous oscillation can be stably continued. Specifically, in addition to the comparator, an operational amplifier or a Schmitt inverter having a logic element can be used.

A circuit using a fixed frequency pulse oscillator, a flip-flop circuit, and a comparator used in the pulse output section controls the output timing of the pulse to adjust the temperature compensation characteristic and improve the linearity only by hardware. It can also be used for

The oscillation period voltage converter (21) is a part for converting the time obtained by determining the transient state of the discharge of the capacitor by the threshold value of the comparator into a voltage.

The output converter (22) outputs a voltage or current corresponding to the displacement of the object to be detected, or compares and judges which side the object to be detected is with respect to a predetermined position and switches. It is what produces the output.

[0016]

[Function] In the position detector for this fluid pressure cylinder,
When a pulsed voltage is applied to the coil by the comparator, the inductance of the coil changes according to the amount of overlap between the conductor (or magnetic or non-magnetic conductor) that is the object to be detected and the coil, and the comparator accordingly. The voltage at the input changes.

When the conductor is inserted into the coil, the change in the inductance causes an eddy current on the surface of the conductor due to the magnetic flux generated by the coil, which acts as a loss to reduce the inductance, and the magnetic substance is inserted. In this case, the magnetic substance acts to concentrate the magnetic flux generated from the coil and increases the inductance.

In the case of a conductive magnetic material, the characteristics are opposite to each other. Therefore, whether the inductance increases or decreases is determined by the characteristic having the stronger influence.

FIG. 7 shows blocks that continuously oscillate using a comparator having hysteresis, and FIG. 9 shows that when a pulsed voltage is applied to the coil from the comparator, the capacitor has a time constant determined by the inductance of the coil, the resistance, and the capacitor. Shows how the electric charges are charged.

Since the pole on the charged side of the capacitor is also connected to the input side of the comparator, when the voltage rises above the threshold of the comparator, as shown in FIG.
The output of the comparator is inverted to 0V (volt) or ground, and the capacitor starts discharging. At this time, the capacitor discharges electric charge with a time constant determined by the inductance of the coil, the resistance, and the capacitor.

When this discharge voltage drops below the threshold value of the comparator, the output of the comparator changes to the high level, so that the oscillation continues continuously until the high voltage is reached (cycle Td in FIG. 7). Is converted into a voltage or the like and used as an output.

Even if the threshold value of the comparator has no hysteresis, oscillation may be maintained due to overshoot due to the back electromotive force of the coil, but since it is unstable, hysteresis is provided in the threshold value of the comparator. , It is important to sufficiently secure the potential difference (difference between VH and VL) ΔV shown in FIG. 8 to stably oscillate.

Next, a method of observing a voltage change of charging / discharging a capacitor, converting it to a voltage and outputting it will be described.

A rectangular wave Tc having a constant time width is generated at the timing of inversion of the output voltage of the continuously oscillating comparator, and the effective value of the rectangular wave is taken to generate the voltage to be output. it can.

In such an output voltage generating method, when the output cycle of the comparator is T, the output voltage is Tc / T.
Since the period T changes when the effective value is obtained, the proportional relationship between the inductance of the coil and the output voltage is impaired.

Therefore, a fixed pulse oscillating circuit is added separately, and a pulse voltage is applied to the coil while the output of the comparator is inverted from the rise of the clock operating in the cycle T, and the threshold of the comparator is discharged when the capacitor is discharged. When a rectangular wave is generated based on a signal when passing a value and the time Td at this time is taken as an effective value, the output becomes Td / T, and the cycle T is constant, so an output proportional to the change in inductance is obtained. be able to.

This method has the same effect even if the pulse is output a plurality of times within the period T. Due to the restriction of the shape of the coil and the like, when the output that can be obtained with a small inductance is small, within one period of the clock. A stable output can be obtained by outputting the pulse voltage a plurality of times to save time.

As another voltage conversion method, it is possible to easily consider a method of measuring the time taken for the capacitor to pass the threshold value when discharging the capacitor and outputting a voltage proportional to the time.

Further, in the position detector of the present fluid pressure cylinder, the coil is an air-core coil, and the object to be detected is a non-magnetic conductor ((17) in FIGS. 2 and 6), so that it reacts with DC magnetism. Since it is also possible to use a material that does not have a direct current, it is possible to use a material that is not affected by external direct current magnetism, and it is possible to reduce the effect on alternating current magnetism by using a coil with a small diameter.

[0030]

EXAMPLE In FIG. 1, the cylinder rod (12) is made of a conductor (2) or a magnetic substance, and is arranged so that the overlapping distance (10) with the coil (1) changes with the change of the position. A detector is configured, a resistor (6), a buffer (7), a flip-flop circuit (8), and a fixed frequency pulse oscillator (9) are connected to one end of the coil (1), and a hysteresis is provided to the other end of the coil (1). An inverted output comparator (5) with a threshold value having a threshold value is connected to the reset section of the flip-flop circuit (8), and a capacitor (5) is connected between the coil (1) and the comparator (5). 4) connected to the end of 0V or ground (3)
Ground to.

Further, a fixed frequency pulse is generated from the fixed frequency pulse oscillator (9), and the output voltage of the inverting output comparator (5) having a threshold value having hysteresis according to the change in the inductance of the coil (1) is When the specified upper limit voltage VH is reached, the reset circuit of the flip-flop circuit operates to discharge the voltage of the coil (1) and the comparator (5), and this voltage is specified lower limit voltage VL.
When a fixed frequency pulse is oscillated, the time Td from reaching the specified lower limit voltage VL to the specified lower limit voltage VL is measured.

5 and 6 are modifications of FIG. 4, but in FIG. 5 and FIG. 6 the shafts on both sides of the piston (11) have the same diameter. It is a structure that can obtain the same movement amount, and is a shape often adopted in the case of a fluid pressure servo cylinder. Further, in the case of a fluid pressure servo cylinder, it is essential to accurately measure the cylinder position in order to confirm the amount of forward and backward movement or to feed back the amount of movement.

1 to 4, the coil is taken out from the side of the head cover (13), and the coil is fixed to the head cover (13) as shown in FIG. Can be taken out from the piston rod output end side of the fluid pressure cylinder, and the place of connection need not be limited to the head cover (13), but can be separately connected to the fixed base (23). Further, in this method, the position detector of the present invention can be mounted by only partially modifying the existing (or commercially available) fluid pressure cylinder.

[0034]

The present invention has the following effects because the position detector of the fluid pressure cylinder can be detected with a small size and a simple structure as described above.

Since the position detecting portion of the fluid pressure cylinder is composed of only one coil and one electric conductor (or magnetic substance or non-magnetic electric conductor), there is a possibility that a plurality of coils are separated from each other like a differential transformer or a resolver. Since the outer shape, the total length, etc. can be reduced as compared with the mechanism in which the relative position of is strictly determined, it can be used in various places where it was difficult in terms of shape or dimension conventionally.

Since the detecting portion can be composed only of the coil and the conductor (or the magnetic substance or the non-magnetic conductor), it is easy to take measures against the high (low) temperature of the coil and the conductor (or the magnetic substance or the non-magnetic conductor). It can also be installed in places with severe operating temperature conditions.

By inserting the non-magnetic conductor (17),
The sensitivity is increased, the movement of the piston rod (12) becomes sensitive, and fine movement can be detected. Further, even if the material of the piston rod (12) is a non-metallic material such as plastic or ceramic. The position detector of the present invention can be applied as it is.

[Brief description of drawings]

FIG. 1 is an overall block diagram of a position detector of a fluid pressure cylinder in which a coil (1) is arranged in a hole formed in a central axial direction of a cylinder rod (12) made of a conductor (2) or a magnetic substance. .

FIG. 2 is a hollow cylindrical non-magnetic conductor (1) that is closely fixed to a hole formed in the axial direction of the central portion of a cylinder rod (12).
A position detector of a fluid pressure cylinder in which the coil (1) is arranged on the inner peripheral portion of 7).

FIG. 3 is a position of a fluid pressure cylinder in which a conductor (2) or a magnetic body is inserted and fixed in the center of a cylinder rod (12), and a coil (1) is arranged on the outer periphery of the conductor (2) or the magnetic body. Detector.

FIG. 4 shows a conductor (2) or a magnetic body inserted and fixed in the center of a cylinder rod (12), the other end of the conductor (2) or the magnetic body is projected to the outside of the cylinder, and a coil ( Position detector of the fluid pressure cylinder where 1) is arranged.

FIG. 5 is a conductor (2) having the same diameter as the cylinder rod (12).
Alternatively, a position detector for a fluid pressure cylinder in which a magnetic body is projected to the side opposite to the protruding side of the cylinder rod, and the coil (1) is arranged inside the projected electric conductor (2) or a hole formed in the center of the magnetic body.

FIG. 6 shows a hollow cylindrical non-magnetic conductor (17) in which a shaft having the same diameter as the cylinder rod (12) is projected to the side opposite to the projection side of the cylinder rod and closely fixed to a hole formed in the center of the projected shaft. A position detector for a fluid pressure cylinder in which a coil (1) is arranged around the circumference.

FIG. 7 is a timing chart of the block diagram of FIG.

FIG. 8 is an overall block diagram of a position detector of a fluid pressure cylinder in which an oscillation method is different from that of FIG.

9 is a timing chart of the block diagram of FIG.

10 is an example diagram in the case of inserting the coil (1) from the output end side of the cylinder rod (12) in the same manner as in FIG.

FIG. 11 is an example view of a fluid pressure cylinder equipped with a conventional magnetic sensor.

[Explanation of symbols]

1 Coil 2 Conductor (or Magnetic Material) 3 Grounding Part 4 Capacitor 5 Inverted Output Comparator with Hysteresis Threshold 6 Resistor 7 Buffer 8 Flip-Flop Element 9 Fixed Frequency Pulse Oscillator 10 Stacking Distance 11 Piston 12 Piston Rod 13 Head Cover 14 Rod Cover 15 Seal 16 Seal 17 Non-Magnetic Conductor 18 Cylinder Tube 19 Magnet 20 Magnetic Sensor 21 Oscillation Period Voltage Converter 22 Output Converter 23 Fixed Stand

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masayuki Miki             102 Shichijo Goshonouchi Minami-cho, Shimogyo-ku, Kyoto-shi, Kyoto Prefecture             Address inside Ribex Co., Ltd. F term (reference) 2F063 AA02 BA05 CA30 CA34 GA04                       GA08 LA08 NA06                 3H081 AA02 AA03 BB02 BB03 CC23                       DD19 GG06 GG12 GG14

Claims (8)

[Claims] 1. A fluid pressure cylinder comprising a conductor (2).
Alternatively, the coil (1) is arranged inside the cylinder rod (12) made of a magnetic material with a gap inside the hole formed in the axial direction, and the coil (1) is referred to as a fluid pressure cylinder (hereinafter referred to as a cylinder). When the cylinder rod (12) moves around the outer circumference of the coil (1) by the surface pressure of the piston (11) due to the fluid supplied to the cylinder, the coil (1) and the conductor (2) Alternatively, if the overlapping distance (10) or area between the magnetic materials is changed and a short waveform is periodically applied to this coil (1), the overlapping distance (10) is changed according to the movement of the cylinder rod (12). Or, since the area changes, the eddy current loss and the inductance between the coil (1) and the conductor (2) or the magnetic body change, and the short-waveform attenuation state changes. Therefore, observe this short-waveform attenuation state. Cylinder Position detector in the configuration fluid pressure cylinder so as to detect the moving distance of de (12). 2. In a fluid pressure cylinder, a hollow cylindrical portion (17) made of a non-magnetic conductor is closely inserted and fixed inside a cylinder rod (12) inside an axially opened hole, Further, the coil (1) is arranged with a gap inside, the coil (1) is connected to the fixed side of the cylinder, and the surface pressure of the piston (11) by the fluid supplied to the cylinder causes the cylinder rod (12), that is, non-contact. When the hollow cylinder part (17) made of a magnetic conductor moves around the outer circumference of the coil (1), the superposition distance (10) between the coil (1) and the hollow cylinder part (17) made of a non-magnetic conductor is increased. ) Or the area is changed and a short waveform is periodically applied to the coil (1), the overlapping distance (10) or the area is changed according to the movement of the cylinder rod (12). 1) and non-magnetic conduction Hollow cylinder part (1
Since the eddy current loss and the inductance between 7) change and the damping state of the short waveform changes, the fluid configured so that the movement state of the cylinder rod (12) can be detected by observing the damping state of the short waveform. Position detector in pressure cylinder. 3. In a fluid pressure cylinder, a hole is bored in the cylinder rod (12) in the axial direction, and a conductor (2) or a magnetic body is inserted and coupled to the center of the hole to form the conductor (2) or the magnetic body. The coil (1) is arranged with a slight gap on the outer circumference of the body, the coil (1) is connected to the fixed side of the cylinder (for example, the head cover (13)), and the piston (11) is supplied by the fluid supplied to the cylinder. When the cylinder rod (12), that is, the conductor (2) or the magnetic body moves on the inner circumference of the coil (1) due to the surface pressure, the overlapping distance (10) between the coil (1) and the conductor (2) or the magnetic body. Alternatively, when the area is changed and a short waveform is periodically applied to the coil (1), the overlap distance (1) is generated according to the movement of the cylinder rod (12), that is, the conductor (2) or the magnetic body.
0) or the area changes, the eddy current loss between the coil (1) and the conductor (2) or the magnetic material and the inductance change, and the short-wave attenuation state changes. A position detector in a fluid pressure cylinder configured to detect the movement distance of the cylinder rod (12), that is, the cylinder rod position by observing 4. In a fluid pressure cylinder, a conductor (2) or a magnetic body is inserted and coupled inside a cylinder rod (12), and the other end of the conductor (2) or the magnetic body is projected to the outside of the cylinder. Furthermore, the coil (1) is arranged with a gap around the outer periphery of the conductor (2) or the magnetic body, the coil (1) is connected to the fixed side of the cylinder, and the piston (11) is connected by the fluid supplied to the cylinder. When the cylinder rod (12), that is, the conductor (2) or the magnetic body moves on the inner circumference of the coil (1) due to the surface pressure, the overlapping distance (10) between the coil (1) and the conductor (2) or the magnetic body. Alternatively, when the area is changed and a short waveform is periodically applied to the coil (1), the overlapping distance (10) or the overlapping distance (10) depending on the movement of the cylinder rod (12), that is, the conductor (2) or the magnetic body, Because the area changes, carp The eddy current loss and the inductance between the conductor (1) and the conductor (2) or the magnetic substance change,
A position detector in a fluid pressure cylinder configured to detect the movement state of the cylinder rod (12) by observing the short-waveform decay state because the short-waveform decay state changes. 5. In a fluid pressure cylinder, a conductor (2) or a magnetic body having the same diameter as the diameter of the cylinder rod (12) on the protruding side is connected to the side of the piston (11) opposite to the cylinder rod (12). The other end is projected to the outside of the cylinder, and the coil (1) is provided inside the conductor (2) or the magnetic body with a slight gap inside the hole formed in the axial direction.
, The coil (1) is connected to the fixed side of the cylinder (for example, the head cover (13)), and the surface pressure of the piston (11) by the fluid supplied to the cylinder causes the cylinder rod (12), that is, the conductor (2). Alternatively, when the magnetic substance moves around the outer periphery of the coil (1), the overlapping distance (10) or the area between the coil (1) and the conductor (2) or the magnetic substance is changed, and the coil (1) is changed. When a short waveform is periodically applied to the coil (1) and the conductor (2), the overlapping distance (10) or the area changes according to the movement of the cylinder rod (12), that is, the conductor (2) or the magnetic body. ) Or the eddy current loss between magnetic materials and the inductance change,
A position detector in a fluid pressure cylinder configured to detect the movement state of the cylinder rod (12), that is, the cylinder rod position by observing the short-waveform damping state because the short-waveform damping state changes. 6. In a fluid pressure cylinder, a shaft having the same diameter as the diameter of the protruding cylinder rod (12) is connected to the side of the piston (11) opposite to the cylinder rod (12), and the other end is outside the cylinder. Further, the hollow cylindrical portion (17) made of a non-magnetic conductor is tightly inserted and fixed inside the projected shaft, inside the projected shaft.
The coil (1) is arranged with a slight gap inside the hollow cylindrical portion (17) made of a non-magnetic material.
Is connected to the fixed side of the cylinder (for example, the head cover (13)), and the piston (1
When the cylinder rod (12), that is, the hollow cylindrical portion (17) made of a non-magnetic conductor moves on the outer circumference of the coil (1) due to the surface pressure of 1), it is made of the coil (1) and the non-magnetic conductor. The overlapping distance between the hollow cylindrical parts (17) (1
0) or the area of which is changed and a short waveform is periodically applied to the coil (1), the cylinder rod (12), that is, the hollow cylindrical portion (17) made of a non-magnetic conductor is moved. Since the overlapping distance (10) or the area changes accordingly, the eddy current loss and the inductance between the coil (1) and the hollow cylindrical portion (17) made of a non-magnetic conductor change, and the short-waveform attenuation state The position detector in the fluid pressure cylinder configured so that the movement distance of the cylinder rod (12) can be detected by observing the damping state of this short waveform. 7. A position detector in a fluid pressure cylinder according to claim 1, wherein a resistor (6), a buffer (7), a flip-flop element (8) and a fixed frequency pulse oscillator (9) are provided at one end of the coil (1). ) Is connected, and the other end of the coil (1) is connected to a comparator (5) having a threshold value having a hysteresis, and the other end is connected to the reset part of the flip-flop circuit (8).
Connect the capacitor (4) between the comparator and the comparator (5),
The other end is grounded to the ground (3), and is made of a conductor (2) or a magnetic substance or a non-magnetic conductor that moves the inner peripheral portion (or outer peripheral portion) of the coil (1) according to the movement of the cylinder rod. A hollow cylindrical portion (17) is provided, and the distance between the coil (1) and the hollow cylindrical portion (17) made of a conductor (2) or a magnetic material or a non-magnetic conductor, or a superposition distance (10), Or coil (1) according to the overlap area
Of the fixed frequency pulse oscillator (9) to generate a fixed frequency pulse,
When the input voltage of the comparator (5) having a threshold value having hysteresis according to the change of the inductance of the coil (1) reaches the specified upper limit voltage VH, the reset circuit to the flip-flop element operates and the buffer (7) Since the output becomes the ground level, the voltage between the coil (1) and the comparator (5) is discharged, and when this voltage reaches the specified lower limit voltage VL, the trigger is activated to fix the time, and from this fixed frequency pulse rise time, A position detector in a fluid pressure cylinder that measures the time Td until reaching the specified lower limit voltage VL and detects this time as the cylinder rod position. 8. The position detector for a fluid pressure cylinder according to claim 1, wherein the resistor (6) and the capacitor (4) are connected to one end of the coil (1) and the oscillation cycle is connected to the other end of the coil (1). Connect the voltage converter (21) and connect the resistor (6)
Between the capacitor and the capacitor (4) and the oscillation period voltage converter (21)
An inverted output comparator (5) having a threshold value having hysteresis is connected between the two to oscillate the output of the comparator (5) having a threshold value having hysteresis, and in response to the movement of the cylinder rod. A hollow cylindrical part (17) made of a conductor (2) or a magnetic substance or a non-magnetic conductor that moves on the inner peripheral part (or outer peripheral part) of the coil (1).
And the coil (1) and the conductor (2) or the superposition distance (10) of the hollow cylindrical portion (17) made of a magnetic material or a non-magnetic conductor, or the coil (1) and the conductor (2) or When the inductance of the coil (1) is changed according to the distance between the magnetic bodies or the hollow cylindrical portion (17) made of a non-magnetic conductor, the coil (1) and the resistance (6) are combined. Since the impedance changes, the charging / discharging time of the capacitor (4) changes, which changes the oscillation cycle of the output of the comparator (5).
A position detector in a fluid pressure cylinder that observes the cycle and detects changes in this cycle as the cylinder rod position.