JPH0249364Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a cylinder stroke position detection device.

Conventional stroke position detection devices include those shown in FIGS. 1a to 1d. In FIG. 1A, a rubber roller 3 is brought into contact with a piston rod 2 of a cylinder 1, and the linear motion of the piston rod 2 is converted into rotational motion, which is detected by a rotation detector 4. In FIG. 1B, a rotation detector 4 is fixed to the piston rod 2, and the linear motion of the piston rod 2 is converted into rotational motion by a rubber roller 3, which is detected by the rotation detector 4. Figure c shows the linear motion of the piston rod 2 being read as it is by an electromagnetic or optical linear scale 5. Figure d shows the ultrasonic transducer 6 facing inside the cylinder 1,
This allows the position of the piston 7 to be detected as well. The above-mentioned conventional devices all have problems such as mechanical contact, complicated detectors, or special machining of the cylinder.

This idea was made in view of the above points,
The object of the present invention is to provide a simple cylinder stroke position detection device that is non-contact and does not require any special processing on the cylinder. In order to achieve this object, the stroke position detection device according to the present invention is provided in a cylinder where the cylinder tube has a low magnetic permeability and the piston has a high magnetic permeability, and each winding is wound around the outer periphery of the cylinder tube at a position shifted in the axial direction. A plurality of rotated primary coils, a take-out means for taking out an output signal corresponding to the excitation by these primary coils, and a means for separately exciting the primary coils with alternating current signals whose phases are shifted from each other. , a first circuit that generates in the extraction means an output signal whose phase is shifted from the AC signal according to the linear position of the piston over the entire length of the range in which the plurality of primary coils are arranged; and the excitation AC signal. and a second circuit for digitally detecting a phase shift of the output signal of the output signal of the extraction means, and the digital information detected by the phase shift is detected in the range where the primary coil is arranged. This is information indicating continuous cylinder stroke positions.

Since the magnetic permeability of the piston is greater than that of the cylinder tube, the magnetic resistance in the magnetic path passing through each primary coil changes depending on the linear position of the piston with respect to the primary coil, and the output according to the magnetic resistance changes. guided to the extraction means. And the first
A plurality of primary coils are separately excited by alternating current signals that are out of phase with each other through the circuit, so that the output signal taken out by the take-out means is a phase-shifted version of the alternating current signal according to the linear position of the piston. becomes. This amount of phase shift is determined by the fact that the magnetic resistance in the magnetic path passing through each primary coil changes depending on the linear position of the piston over the entire length of the range where multiple primary coils are arranged. It changes continuously over the entire length of the range where the coil is placed. Therefore, if the second circuit digitally detects the phase shift of the output signal of this extraction means with respect to the excitation AC signal, then 1
Information indicating continuous stroke positions in the range where the next coil is arranged can be obtained as digital information.

Therefore, according to this invention, it is possible to detect continuous stroke positions in a wide stroke range using digital information, thereby providing a wide range of new applications in cylinder control. It is possible to expect excellent effects such as detecting an intermediate position and performing intermediate position stop control and opening up other new control fields.

To show the correspondence with the embodiments described below, the plurality of primary coils correspond to the coils 11 and 13 in FIGS. 1 and 4, and the extraction means corresponds to the secondary coil 12 in FIG. 2 or the coils 13 in FIG. The first circuit corresponds to the circuit portion consisting of the oscillator 15, the counter 16, the flip-flops 17, 18, 19, the low-pass filters 20, 21, and the amplifiers 22, 23 in FIG. The second circuit corresponds to the circuit portion consisting of the amplifier 24, polarity discrimination circuit 25, rise detection circuit 26, and buffer register 27 shown in FIG.

Embodiments of this invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 shows an example in which three coils 11, 12, and 13 are wound around the outer periphery of the cylinder tube 10, where the coils 11 and 13 are primary coils, and 12 is a secondary coil. The primary coils 11 and 13, which are arranged at positions shifted in the axial direction, are separately excited by alternating current signals Isinωt and Icosωt whose phases are shifted from each other. In this example, the secondary coil 12 is located between the two primary coils 11 and 13. here,
The winding widths a, b, c and coil pitches d, e of the primary and secondary coils 11, 12, 13 can be arbitrarily designed in consideration of the width f of the piston 14, the measurement range, etc. This idea is applied to a device where the magnetic permeability of the piston 14 is much greater than the magnetic permeability of the cylinder tube 10. Preferably, the cylinder tube 10 is made of a non-magnetic material and the piston 14 is made of a magnetic material. Then, piston 14
The coupling coefficients of the coils 11, 12, and 13 change according to the deviation of. Moreover, as is clear from the principle of a differential transformer, the illustrated piston 14
When the position is set as the zero position, the coupling coefficient between the primary coil 11 and the secondary coil 12 and the coupling coefficient between the primary coil 13 and the secondary coil 12 change differentially.

Here, since the primary coils 11 and 13 are excited by the phase-shifted AC signals Isinωt and Icosωt, respectively, the signal Ksin(ωt −φ)
is obtained from the secondary coil 12. This principle is described in detail in Japanese Utility Model Application Publication No. 135917/1983, and will be briefly explained below.

The coupling coefficient x between the primary coil and the secondary coil can be expressed as x=l/k (where l is the position of the piston 14 and k is a constant). When the output signal Y of the secondary coil 12 is expressed using this x, it becomes Y=I(1-x) sinωt-I(1+x)cosωt. This formula When rewritten using the function, Y=Ksin(ωt−φ). Therefore, the output signal of the secondary coil 12 is a signal whose phase is shifted by φ from the reference excitation AC signal Isinωt, and this phase shift φ is a function of x as shown in the above equation, where x is a function of the piston. 14 as a function of position l. Therefore, by measuring this phase shift φ, the position l of the piston 14 can be determined.

The excitation AC signals Isinωt and Icosωt are sent to the primary coil 1.
1, 13 and secondary coil 1
FIG. 3 shows an example of a circuit for detecting the phase shift φ between the output signal Ksin (ωt−φ) of No. 2 and the reference signal Isinωt.

The counter 16 is a modulo M-adic (M is an arbitrary integer) and sequentially counts the high-speed clock pulses CP given from the oscillator 15. The output of the M/quaternary frequency division stage of the counter 16 is input to the C terminal of the D flip-flop 17. The outputs of the D flip-flops 17, 18, and 19 are input to the D input terminal, and the frequency of the pulse signal input to the C terminal is divided into 1/2. The Q output of the D flip-flop 17 is input to the C terminal of the D flip-flop 18, and the output of the D flip-flop 17 is input to the C terminal of the D flip-flop 19. Flip-flop 17 outputs a square wave signal obtained by dividing the clock pulse CP by M/2, and flip-flops 18 and 19 output a 50% duty square wave signal obtained by dividing the clock pulse CP by M, maintaining a 90 degree phase shift. be done. This flip-flop 1
Each output signal of 8 and 19 is passed through a low pass filter 20,
21 and amplifiers 22 and 23,
A cosine wave signal Icosωt and a sine wave signal Isinωt are obtained. These signals Icosωt and Isinωt are 1 as mentioned above.
The voltage is applied to the secondary coils 13 and 11, respectively. The frequency of these signals Isinωt and Icosωt is the clock pulse
It corresponds to CP divided by M. Therefore, one count of the counter 16 corresponds to a phase angle of 2π/M.

The output signal Ksin (ωt−φ) of the secondary coil 12 is applied to a polarity switching circuit 25 via an amplifier 24.
This circuit 25 outputs a rectangular wave signal of "1" or "0" corresponding to the positive or negative polarity of the alternating current signal Ksin (ωt-φ). The rising edge detection circuit 6 detects when the output of the circuit 25 rises to "1", that is, the output AC signal Ksin
A short pulse is output when (ωt−φ) is zero phase. The output pulse of this circuit 26 is applied to a load control input of a buffer register 27. The count contents of the counter 16 are given to the data input of the register 27. Since the modulo number M of the counter 16 corresponds to one cycle of the alternating current signal Isinωt, it can be designed so that all bits of the counter 6 become "0" when the sine wave signal Isinωt has zero phase. Therefore, the count contents of the counter 16 are stored in the register 2 by the output pulse of the rising edge detection circuit 26.
7, digital data D〓 corresponding to the phase shift φ can be stored in the register 27.

FIG. 4 shows that only the primary coils 11 and 13 are wound around the outer circumference of the cylinder tube 10, and the secondary coil 12 is wound around the outer circumference of the cylinder tube 10.
Here is an example where is omitted. A sine wave signal and a cosine wave signal are separately applied to the primary coils 11 and 13 as described above. The impedance of the coils 11 and 13 changes differentially depending on the displacement of the piston 14, so if the coils 11 and 13 are excited with a constant current (or constant voltage), a voltage change (or current) will occur in accordance with this impedance change. change) is the coil 1
Occurs on 1 and 13. Therefore, by picking up the voltage changes (or current changes) of the coils 11 and 13, a signal corresponding to the displacement (linear position) of the piston 14 can be obtained. For example, coil 1
When coils 1 and 13 are excited by constant current signals Isinωt and Icosωt, respectively, a voltage change E with a phase shift of E=K ₁ cos(ωt−φ ₁ ) occurs in the coil 11 or 13. Here, it has already been confirmed that the phase shift φ ₁ is a function of the linear position of the piston 14. This detailed analysis is
Since it is disclosed in Japanese Patent No. 45129, it will be omitted in this specification.

Further, when the coils 11 and 13 are excited with a constant voltage, by adding and combining the current changes occurring in both coils, an alternating current signal with a phase shift similar to that described above is obtained. The analysis of this point is also shown in the above-mentioned specification of the prior application, so it will not be discussed in detail here.

By processing the output AC signal containing the above-mentioned phase shift φ ₁ obtained as a result of exciting the coils 11 and 13 in FIG. 4 with a constant current or constant voltage in the circuit shown in FIG. 3, the phase shift φ ₁ That is, digital data corresponding to the linear position of the piston 14 can be obtained.

In the example of FIGS. 2 and 4, the measurement range is limited by the dimensions of the coils 11, 12, 13. Therefore, in order to extend the measurement range, multiple coil groups CG1, CG.2,
CG3... may be arranged sequentially in the axial direction. The individual coil groups CG1, CG2, CG3... each include two primary coils 11, 13 and one secondary coil 12 sandwiched between them, as shown in FIG. The secondary coils 11 and 13 are excited by a sine wave signal Isinωt and a cosine wave signal Icosωt, respectively. Therefore, each group CG1, CG2, CG3
The position of the piston 14 from the secondary coil 12 of...
l Signals with phase shifts φ ₁ , φ ₂ , φ ₃ ... according to _X
Y ₁ = K ₁ sin (ωt-φ ₁ ), Y ₂ = K ₂ sin (ωt-φ ₂ ), Y ₃
=K ₃ sin(ωt−φ ₃ ) are obtained, respectively. The interval g between each coil group CG1, CG2, CG3... is as shown in Figure 6.
2. The interval shall be such that the measurement ranges L ₁ , L ₂ , L ₃ ... of CG3... can be connected without interruption. Piston 14 position l _X is coil group CG
1, the output signal Y ₁ of the secondary coil 12 of this coil group _CG1 is selected and its phase shift φ ₁ is measured. l When _X is in the coil group CG2, select the secondary coil output signal _Y2 of the group CG2 and measure its phase shift _φ2 . l When _X is in coil group CG3, select secondary coil output signal _Y3 of group CG3 and measure its phase shift _φ3 . In this way, as shown in FIG. 6, the phase _shifts φ ₁ , φ ₂ ,
Data for _φ3 is obtained. Output signals of each coil group CG1 to CG3 according to the position _lX of the piston 14
An example of the circuit for selecting Y ₁ to _{Y 3} is shown in Figures 7 and 8.
As shown in the figure. In this figure, the same symbols as in FIG. 3 indicate the same circuits. Additionally, zero cross detection circuits 28, 2
9, 30, and 31 correspond to the polarity discrimination circuit 25 and the rising edge detection circuit 26 in FIG.

In Figure 7, each coil group CG1 to CG
3 secondary coil output signals Y ₁ , Y ₂ , Y ₃ are output from amplifier 3.
2, 33, 34 to the maximum value detection circuit 35, and analog gates 36, 37, 38.
are input respectively. The maximum value detection circuit 35 detects each signal.
The one with the highest level among Y ₁ , Y ₂ , and Y ₃ is detected, and the group selection signal (one of D1, D2, and D3) corresponding to the detected signal is set to "1".
Since the secondary output level of the coil group in which the piston 14 is located within the measurement range is the highest, the group selection signal D1, which is output from this circuit 35,
D2 and D3 are currently in which group is the piston 14?
It shows whether it is located in CG1 to CG3. The analog gates 36 to 38 are controlled by the group selection signals D1 to D3, and the output signal (one of _Y1 to _Y3 ) of the group in which the piston 14 is currently located is selected, and the output signal is sent to the zero cross detection circuit 28. and loads the output of the counter 16 into the register 27 in response to the zero phase of this signal (Y ₁ to _{Y 3} ). Data D〓 indicating the phase shift φ ₁ or φ ₂ or φ ₃ stored in the register 27 indicates the relative position of the piston 14 within each group,
Group selection signals D1 to D3 indicate the group number in which the piston 14 is located. Therefore, the absolute position _lX of the piston 14 is indicated by the combination of the data D and the signals D1 to D3.

FIG. 8 shows that the piston 14 is connected to each coil group.
When CG1 to CG3 are located in the measurement range _L1 to _L3 , the phase shift of each output signal _Y1 to _Y3 is _φ1 to
Considering that φ ₃ occurs only in the range of 0° to 90°, only the signal (one of Y ₁ to Y ₃ ) whose phase shift φ ₁ to φ ₃ is within the range of 0° to 90° is selected. This is something you can choose from. 16A is an M/4-base counter, and 16B is a binary 4-base counter. The binary 2-bit output of the quaternary counter 16B is sent to the sine wave and cosine wave forming circuits 39, 40, and 41, respectively, to generate two sets of signals sinωt and sin(ωt+90°) whose phases are sequentially shifted by 90 degrees, respectively.
sin(ωt+90°), sin(ωt+180°), sin(ωt+180°)
゜)
and sin(ωt+270°) are output from each circuit 39, 40, 41. These signals are applied to the primary coils of each coil group CG1, CG2, CG3 via the amplifier group 42, respectively. Therefore, the primary coils of each coil group CG1 to CG3 are sequentially excited by alternating current signals whose phases are shifted by 90 degrees. As a result, the timing of ωt=0 in the output signals Y ₁ , Y ₂ , Y ₃ of each coil group CG1 to CG3 is 90
It will be shifted sequentially by degrees.

The output of the quaternary counter 16B is sent to the decoding circuit 42.
decoded with This decode output M0, M
1, M2, M3 are each 90 in phase angle timing.
It is something that occurs at intervals of degrees. For example, the signal M0 is the phase shift φ ₁ of the output signal Y ₁ of the coil group CG1.
is in the range of 0° to 90°, the signal M1 becomes “1” when the phase shift φ ₂ of the output signal Y ₂ of CG2 is in the range of 0° to 90°, and the signal M2 becomes “1”.
becomes "1" when the phase shift φ ₃ of the output signal Y ₃ of the CG 3 is in the range of 0° to 90°. The reason for this is as mentioned above, the timing of ωt=0 for each signal Y ₁ to _{Y 3} is 90
This is because they are sequentially shifted by degrees. This signal M
0, M1, M2 are signals for masking each output signal Y ₁ , Y ₂ , Y ₃ and are connected to AND circuits 43 and 4.
4 and 45 are input separately. AND circuit 43,
The other inputs of 44 and 45 have respective output signals Y ₁ , Y ₂ ,
Zero cross detection circuit 29, 30, corresponding to Y ₃
31 outputs are added.

If the output pulses of the zero cross detection circuits 29, 30, 31 occur in the range of 0° to 90° (that is, the phase shifts φ ₁ , φ ₂ , φ ₃ are in the range of 0° to 90°), the piston 14 There are only those that correspond to a single group (one of CG1 to CG3) corresponding to the current position of . Therefore, only the output pulse of the zero cross detection circuit (one of 29 to 31) corresponding to that single group is exclusively sent to the AND circuit (4).
3 to 45), passes through the OR circuit 46, and is applied to the load control input of the register 27. In this way, data D〓 indicating the relative position detected by the coil group corresponding to the current position of the piston 14 is latched in the register 27.
On the other hand, the output M of each AND circuit 43, 44, 45
0', M1', and M2' are applied to a hold circuit 47 and held. These signals M0', M1',
The one that holds M2' is the group selection signal D.
1, D2, D3.

Of course, a plurality of coil groups each consisting of two coils may be provided as shown in FIG. 4.

As explained above, according to this invention, it is sufficient to simply wind the coil around the outer circumference of the shilling tube, so there is no need for special processing, and since it is non-contact, there is no risk of failure. play. Furthermore, since the phase shift is counted digitally, there is also the effect that the detection resolution can be high.

[Brief explanation of the drawing]

Figures 1a to d are views showing a conventional cylinder stroke detection device, Figure 2 is a side sectional view showing an embodiment of this invention, and Figure 3 is a block diagram showing an example of the electrical circuit portion of the same embodiment. 4 is a side sectional view showing another embodiment of this invention, FIG. 5 is a side sectional view showing still another embodiment of this invention, and FIG. 6 is a graph showing the detection operation of the same embodiment. , FIG. 7 is a block diagram showing one example of the electric circuit portion in the same embodiment, and FIG. 8 is a block diagram showing another example of the same electric circuit portion. 10...Cylinder tube, 14...Piston, 11, 13...Primary coil, 12...Secondary coil, 15, 16, 17, 18, 19, 20, 2
1, 22, 23...Circuit group for generating an excitation AC signal, 15, 16, 24, 25, 26, 2
7...Circuit group for digitally detecting phase shift.

Claims (1)

[Claims for Utility Model Registration] 1. In a cylinder whose cylinder tube has a low magnetic permeability and whose piston has a high magnetic permeability, a plurality of primary coils each wound around the outer periphery of the cylinder tube at axially shifted positions. , an extraction means for extracting an output signal corresponding to excitation by these primary coils; and a plurality of primary coils arranged by separately exciting the primary coils with alternating current signals that are out of phase with each other. a first circuit that generates in the extraction means an output signal that is a phase shift of the alternating current signal according to the linear position of the piston over the entire length of the excitation range; and a second circuit for digitally detecting a shift, the phase shift detection digital information being information indicating continuous cylinder stroke positions in a range in which the primary coil is arranged. 2. The cylinder stroke position detecting device according to claim 1, wherein the take-out means comprises a secondary coil wound around the outer periphery of the cylinder tube in correspondence with the primary coil. 3. The extraction means extracts a voltage (or current) signal from the primary coil according to the impedance of the primary coil, and the first circuit connects the primary coil to an alternating current signal that is out of phase with each other. A voltage (or current) signal corresponding to the impedance of the primary coil according to the linear position of the piston is generated in the primary coil by exciting it with a constant current (or constant voltage) according to the signal. A cylinder stroke position detection device according to claim 1 of a certain utility model registration. 4. The first circuit includes a circuit that generates two alternating current signals that are 90 degrees out of phase with each other, and the plurality of primary coils include two adjacent coils that are separately excited by the two alternating current signals. The cylinder tube includes a plurality of sets of matched primary coils, and the take-out means includes a plurality of secondary coils respectively wound around the outer periphery of the cylinder tube in correspondence with each set of the primary coils. A cylinder stroke position detection device according to claim 1 of the registered utility model claim.