JPH086259Y2 - Linear position detector - Google Patents

Description

[Detailed Description of the Invention] [Industrial application] The present invention relates to a position detection device for detecting the position of a moving body such as a cylinder rod or a machine tool, and in particular to a periodical electromagnetic characteristic formed on a scale. The present invention relates to a linear position detection device that detects a change and detects the position of a moving body.

[Conventional technology]

When controlling a construction machine such as a dozer shovel, a groove is formed in the rod of the hydraulic cylinder, or a scale is formed by changing the electric and magnetic characteristics of the rod by performing partial hardening, and this scale is used as a magnetoresistive element. The position of the bucket and the like are detected by a magnetic sensor such as. For the origin for position detection, a limit switch is attached to the end of the rod to generate a reset signal, or a pattern indicating the origin is provided at one end of the scale, which is read by a magnetic sensor to reset the counter. I am trying.

[Problems to be solved by the device]

As described above, a position detection device such as a construction machine is provided with a pattern indicating the origin at the end portion of the rod, or is equipped with a limit switch. Therefore, when resetting the origin, it is necessary to operate the cylinder to the stroke end, and it is very difficult to reset the origin in the case where the stroke length of the cylinder reaches several meters such as large construction machines. It is troublesome. Therefore, the position detection device provided in the construction machine or the like is generally used as an increment type that detects only the movement amount.

Even if the sensor for detecting the scale graduation is at an arbitrary position with respect to the scale at the start of use, the present invention ensures the position without resetting if the relative movement between the sensor and the graduation exceeds a certain level. It is an object of the present invention to provide a linear position detecting device that can be known.

[Means for solving the problem]

In order to achieve the above object, the linear position detecting apparatus according to the present invention has a scale 12 formed by periodically changing the electromagnetic characteristics as shown in FIG.
And a plurality of reference sections 45a to 4 which are parallel positions different from the scale positions and which include different scale numbers and different lengths.
5c, a scale 10 having reference point electro-magnetic characteristic changing portions 44a to 44d provided at both ends of each reference section 45a to 45c, and the scale 10 is arranged so as to be movable relative to the scale 10.
Based on the output signal to the plurality of magnetic sensors 20, 22 for detecting 12 and the plurality of magnetic sensors 20, 22,
A direction discriminating circuit 32 that detects the direction of relative movement between the scale 10 and the magnetic sensors 20, 22 and outputs a count-up signal or a count-down signal, and a count-up signal or a count-up signal that receives the output of the direction discriminating circuit 32. An up / down counter 34 that counts a countdown signal, a position calculator 36 that receives the output from the up / down counter 34 and calculates the positions of the scale 12 and the magnetic sensors 20, 22, and the reference sections 45a to 45c. In a linear position detection device having a reference point detection sensor 46 which is arranged so as to be movable relative to the reference point and which detects the reference point electro-magnetic characteristic changing portions 44a to 44d, can be arranged in advance in each of the reference sections 45a to 45c. The number of graduations
While storing the absolute value of each reference point electro-magnetic characteristic changing unit 44a ~ 44d forming each reference section 45a ~ 45c,
Receiving the output signal of the up / down counter 34 and the detection signal from the reference point detection sensor 46, the reference point detection sensor 46 causes the two reference point electro-magnetic characteristic changing units 44a-4.
When 4d is detected before and after 4d, the reference section 45a to 45c in which the count value of the output signal of the up / down counter 34 and the number of the scales 12 of each of the reference sections 45a to 45c stored in advance are equal are specified. By specifying the reference point electro-magnetic characteristic change unit 44a ~ 44d detected later by, as a position confirmation signal the pre-stored absolute value corresponding to the specified reference point electro-magnetic characteristic change unit 44a ~ 44d. It is characterized by including a position confirmation signal output circuit 50 for outputting to the position calculator 36 and thereby making the output of the position calculator 36 a pseudo absolute value.

[Action]

 According to the above configuration, the following action occurs.

The position confirmation signal output circuit 50 preliminarily sets each reference section 45a-4
The number of scales 12 of 5c and the absolute values of the reference-point-use electromagnetic characteristic changing units 44a to 44d forming the reference sections 45a to 45c are stored.

On the other hand, the position confirmation signal output circuit 50 receives the output signal of the up / down counter 34 and the detection signal from the reference point detection sensor 46.

Here, when the reference point detection sensor 46 detects the two reference point electro-magnetic characteristic changing portions, for example, 44a and 44b, before and after (for example, in the order of 44a to 44b), the position confirmation signal output circuit 50 outputs 45
A scale number equal to the count value of the output signal of the up / down counter 34 in b is extracted from the memory. When this extraction is completed, the reference section 45b is inevitably specified.

Therefore, the position confirmation signal output circuit 50 identifies the subsequently detected reference point electro-magnetic characteristic changing unit 44b.

Next, the absolute value corresponding to the reference point electro-magnetic characteristic changing unit 44b is extracted from the storage, and this absolute value is output to the position calculator 36 as a position confirmation signal.

The position calculator 36 adds the up-down count value (that is, the increment value) from the up-down counter 34 to the absolute value from the position confirmation signal output circuit 50, and thereby the pseudo absolute value is sent to the stroke control device or the like. Will be output.

〔Example〕

A preferred embodiment of the linear position detecting device according to the present invention is
Detailed description will be given according to the attached drawings.

FIG. 1 is an explanatory view of a linear position detecting device according to a reference example of the present invention.

In FIG. 1, a scale 12 is formed on a scale 10. The scale 10 is made of, for example, a magnetic material such as a rod of a cylinder. The surface layer has an uneven surface formed by etching and is covered with chrome plating, and is movable in the axial direction as indicated by arrow A. There is.

The scale 12 is provided with grooves 14 in the circumferential direction on the surface of the scale 10 with a predetermined pitch p (for example, 2 mm), and a convex portion 16 and a concave portion (groove) 1
The scale 10 is formed by changing the electromagnetic characteristics of the scale 10. However, in the scale 10, the groove 14 is not formed over the entire circumference of the scale 10, and the scale 12 is formed on, for example, half of the circumference. The scale 10 is provided with an origin electro-magnetic characteristic changing portion 18 formed of a protrusion in a portion of the scale 10 where the scale 12 is provided, at a substantially central portion where the scale 12 is not formed.

The scale 12 and the electro-magnetic characteristic changing unit 18 for the origin partially change the electro-magnetic characteristics by partially quenching, partially tempering the scale 10, or irradiating a high energy beam such as a laser or an electron beam. It can also be formed.

At a position close to the scale 12 of the scale 10, a pair of magnetic sensors 20, 22 for detecting a change in electro-magnetic characteristics of the scale 10 formed by the concave portion 14 and the convex portion 16 are arranged. These magnetic sensors 20 and 22 are composed of, for example, a magnetoresistive element and a magnetizing body such as a magnet provided on the back side of the element, and are provided on the scale 12 so as to be movable relative to the scale 10. The distance between the magnetic sensors 20 and 22 is
It is arranged so as to be shifted by p / 4 with respect to the pitch p of the scale 12 so that a phase difference of an electrical angle of 90 degrees occurs between the detection signals of both. Further, at a position substantially corresponding to the position where the magnetic sensors 20 and 22 are arranged, an origin detection sensor 24 for detecting the electromagnetism characteristic changing portion 18 for origin, for example, a magnetoresistive element and a magnetizer, is a scale. It is arranged so that it can move relative to 10.

The detection signals of the magnetic sensors 20, 22 and the origin detection sensor 24 are input to the waveform shaping circuits 26, 28, 30. The output signals of the waveform shaping circuits 26 and 28 are input to the direction discriminating circuit 32 that determines the direction of relative movement between the scale 10 and the magnetic sensors 20 and 22 based on the phase difference between the two signals.

The up / down counter 34 connected to the output side of the direction discrimination circuit 32 counts up the output signals of the waveform shaping circuits 26, 28 which are the detection signals of the magnetic sensors 20, 22 based on the output signals of the direction discrimination circuit 32. It counts down and sends the count value to the position calculator 36. The position calculator 36 obtains the position of a control target (for example, a bucket of a dozer shovel) from the output of the up / down counter 34, and sends it to the stroke control device 38.

On the other hand, the waveform shaping circuit to which the origin detection sensor 24 is connected
A switching circuit 40 is connected to the output side of 30. Switching circuit
40 is switched by a signal indicating the direction of relative movement between the scale 10 and the magnetic sensors 20, 22 output from the direction discrimination circuit 32, and the output signal of the waveform shaping circuit 30 is reset terminal of the up / down counter 34 or a one-shot circuit. Enter in 42.

The one-shot circuit 42 serves as a signal detection circuit,
For example, when the up / down counter 34 is incrementing, it is reset at the rising edge of the reset signal. When the counter is incrementing, when the output signal of the waveform shaping circuit 30 falls, a positive pulse is output. The output side is connected to the reset terminal of the up / down counter 34, and the output signal is sent to the up / down counter 34 as a reset signal.

The operation of the reference example configured as described above is as follows.

When the scale 10 moves in the axial direction as indicated by the arrow A, the concave portions 14 and the convex portions 16 of the graduation 12 alternately pass through the front surfaces of the magnetic sensors 20 and 22. Along with this, in the magnetic sensors 20 and 22, the lateral component (the component parallel to the element surface) of the magnetic flux generated by the magnet that passes through the magnetoresistive element changes, and the magnetic sensors 20 and 22
The sinusoidal detection signal is output to the waveform shaping circuits 26 and 28.

The waveform shaping circuits 26, 28 shape the signals from the magnetic sensors 20, 22 into rectangular waves and input them to the direction discrimination circuit 32. The direction discriminating circuit 32 is configured such that the distance between the magnetic sensor 20 and the magnetic sensor 22 is deviated by 1/4 of the pitch of the scale 12 and the phases of the output signals are deviated from each other by 90 degrees. The direction of relative movement between the scale 10 and the magnetic sensors 20, 22 is determined from the phase difference between the output signals of the shaping circuits 26, 28.

That is, the direction discrimination circuit 32 determines that the scale 10 is moving to the left in the figure, for example, when the output signal of the magnetic sensor 20 is 90 degrees in phase ahead of the output signal of the magnetic sensor 22. A count-up signal is output to the up-down counter 34, and the detection signals of the magnetic sensors 20 and 22 output by the waveform shaping circuits 26 and 28 are counted up. And
On the contrary, when the detection signal of the magnetic sensor 22 leads the detection signal of the magnetic sensor 20 by 90 degrees in phase, the direction discrimination circuit 32 outputs a countdown signal to the up / down counter 34 and the waveform shaping circuits 26, 28. It counts down in synchronization with the output signal of.

Further, the direction discriminating circuit 32 sets the switching circuit 40 to a when the count-up signal is output to the up-down counter 34.
When the countdown signal is output to the up-down counter 34, the switching circuit 40 sends the switching signal to the side b. For this reason, the up-down counter 34, when counting up the output signals of the magnetic sensors 20 and 22,
Origin detection sensor via the waveform shaping circuit 30 to the reset terminal
24 is connected and the one-shot circuit 42 is connected when counting down the output signals of the magnetic sensors 20 and 22.

On the other hand, in the origin detection sensor 24, when the scale 10 is moved and the origin electromagnetic characteristic changing portion 18 made of a protrusion passes forward, the magnetic flux on the surface of the scale 10 is changed. The section 18 is passed, that is, the origin electromagnetic characteristic changing section 18 is detected and a detection signal is output to the waveform shaping circuit 30.

The waveform shaping circuit 30 shapes the output signal of the origin detection sensor 24 into a rectangular waveform. When the up / down counter 34 is counting up, the signal output from the waveform shaping circuit 30 is input to the reset signal of the up / down counter 34 as reset because the switching circuit 40 is on the a side. At the time of rising, the count value of the up / down counter 34 is set to zero.

On the other hand, when the up / down counter 34 is counting down, the output signal of the waveform shaping circuit 30 is input to the one-shot circuit 42 because the switching circuit 40 is on the b side. The one-shot circuit 42 generates a positive pulse when the output signal of the waveform shaping circuit 30 falls, and supplies it to the up-down counter 34 as a reset signal.

Therefore, the up / down counter 34 is, for example, a scale.
When 10 moves to the left and counts up the signals of the magnetic sensors 20 and 22, the origin detection sensor 24 is reset when the output signal of the origin detection sensor 24 rises. It is reset when the left end of the figure is detected. Also, the up / down counter 34
Indicates that the scale 10 has moved to the right in the figure and the magnetic sensor 20,
When counting down the output signal of 22, the reset signal is received from the one-shot circuit 42, and when the one-shot circuit 42 falls of the origin detection sensor 24,
In other words, the origin detection sensor 24 is the origin electromagnetic characteristic changing section.
Resets when 18 left edge is detected.

In this way, this reference example uses the scale 10 and the magnetic sensor 2
0 and 22 move relative to each other, and each time the origin electro-magnetic characteristic changing portion 18 provided on the scale 10 is reset in front of the origin detection sensor 24, the magnetic sensors 20 and 22 are moved to the scale 10.
The origin can be easily confirmed without moving to the end (stroke end of the cylinder), and the measurement deviation due to noise or the like can be automatically corrected. Moreover, since the origin electromagnetic characteristic changing unit 18 is located at the center of the range where the most frequently used scale 12 of the scale 10 is provided or at the cylinder portion that is often used, it is easy to reset the origin of the up-down counter 34. Not only that, even if the magnetic sensors 20 and 22 are at arbitrary positions, the origin reset processing of the position detection device is automatically performed with use, and it is used as an absolute position detection device. be able to.

Further, in the reference example, when the up / down counter 34 is counting up, the output signal of the waveform shaping circuit 30 is directly used as a reset signal for the up / down counter.
When it is input to 34 and the up / down counter 34 is counting down, the output of the waveform shaping circuit 30 is input to the one-shot circuit 42, and the one-shot circuit 42 outputs a positive pulse due to the fall of the output signal of the waveform shaping circuit 30. Since the up / down counter 34 is input as a reset signal, it is possible to eliminate the deviation when the up / down counter 34 is reset due to the difference in the moving direction of the scale 10.

The count value of the up / down counter 34 is converted into a position signal of a control target (not shown) by the position calculator 36 and sent to the stroke control device 38.

In the reference example, the case where each sensor is formed of a magnetoresistive element has been described, but a coil or the like may be used to detect a change in the electromagnetic characteristics.
Further, the origin-use electromagnetic characteristic changing portion 18 may utilize the magnetoelectric changing characteristic due to the partial heat treatment or the like similarly to the scale 12. Further, although the magnetic detection type position detection device has been described in the reference example, the present invention can be applied to an optical type device. In the reference example, the switching circuit 40
However, the switching circuit 40 may be provided on the output side of the one-shot circuit 42.

The origin electromagnetic characteristic changing portion 18 may be formed by magnetizing a part of the scale 10 or forming a concave portion, but by forming a convex portion, the influence of a flaw on the surface of the scale 10 is affected. The size can be reduced, and the detection sensitivity can be improved because the convex portion is detected.

FIG. 2 is an explanatory diagram of an embodiment of the present invention, in which parts corresponding to those in the reference example are designated by the same reference numerals so as to be used as counter clocks. In FIG. 2, a plurality of reference point electro-magnetic characteristic changing portions 44a, 4a along the graduation 12 are formed on the portion of the scale 10 where the graduation 12 is not formed.
4b, 44c, ... are provided by protrusions.

The reference point electro-magnetic characteristic changing portion 44a is formed at a position corresponding to the origin 0 of the scale 12 provided on the scale 10. Further, the electro-magnetic characteristic changing portions 44a, 44b, 44c for each reference point, ...
, The intervals formed by, that is, the reference sections 45a, 45b, 45c divided by the reference-point electromagnetic characteristic changing portions,
The lengths of …… are different from each other, such as L ₁ , L ₂ , L ₃ . The scale 12 formed so as to be used like a counter with unevenness included in each of the reference sections 45a, 45b, 45c, ... serves as an identification mark for each reference section.

On the other hand, a reference point detection sensor 46 is arranged near the scale 10 so as to be movable relative to the scale 10, and each of the reference point electro-magnetic characteristic changing units 44a, 44b, 44c, ...
It can be detected as a change in the electro-magnetic characteristics.
The detection signal of the reference point detection sensor 46 is input to the position confirmation signal output circuit 50 via the waveform shaping circuit 48. Further, the position confirmation signal output circuit 50 is adapted to receive the count value of the up / down counter 34,
A position confirmation signal is output to the position calculator 36 based on the signals from the waveform shaping circuit 48 and the up / down counter 34.

In the present embodiment configured as described above, the scale 10
When is moved in the direction of arrow A, the reference point electro-magnetic characteristic changing portions 44a, 44b, 44c, ... Pass in front of the reference point detection sensor 46. Then, the reference point detection sensor 46 includes one of the reference point electro-magnetic characteristic changing units 44a, 44b, 44c, ...
When the vehicle passes the front, it outputs a detection signal. This output signal is shaped into a rectangular wave by the waveform shaping circuit 48 and input to the position confirmation signal output circuit 50.

The position confirmation signal output circuit 50 includes an up / down counter 34
While reading the count value of and monitoring the increase or decrease of the count value, when the detection signal of the reference point detection sensor 46 is input,
It checks how many count values of the up / down counter 34 have increased or decreased, and outputs a position confirmation signal to the position calculator 36.

That is, the position confirmation signal output circuit 50 is a waveform shaping circuit.
When a signal indicating that the reference point electromagnetism characteristic changing portion is detected is input from the reference point detection sensor 46 via 48,
From the time when the signal is received from the waveform shaping circuit 48 last time to the time when the signal is received from the waveform shaping circuit 48 this time, how much the count value of the up-down counter 34 has increased or decreased is checked. Then, the continuous 2 output from the waveform shaping circuit 48 is output.
The increase / decrease value of the up / down counter 34 between the two signals is regarded as an identification mark for identifying the reference sections 45a, 45b, 45c, ... By the two reference point electromagnetic characteristic changing portions detected by the reference point detection sensor 46. Separated reference sections 45a, 45b,
Specify 45c, ...

That is, the count value of the up / down counter 34 is, for example, 4 between the two detection signals output by the reference point detection sensor 46.
Assuming that the scale 10 increases, the position confirmation signal output circuit 50 moves the scale 10 by moving the scale 10 to the left in the figure.
The reference point detection sensor 46 that has moved relative to 10 moves the reference section 45b
It is detected that the right end of the reference section 45b is reached after passing through and the reference point electro-magnetic characteristic changing portion 44c is detected. Further, the position confirmation signal output circuit 50, when receiving the signal from the waveform shaping circuit 48, at this time, the control target not shown is the position represented by the position of the scale 12 corresponding to the reference point electro-magnetic characteristic changing unit 44c, For example, a position confirmation signal indicating that the position is 50 mm from the starting point (origin) is output to the position calculator 36.
The position calculator 36 confirms the position obtained based on the count value of the up / down counter 34 by a signal received from the position confirmation signal output circuit 50, and sends it to the stroke control device 38.

It should be noted that the position confirmation signal output circuit 50 has an up / down counter between two consecutive output signals of the waveform shaping circuit 48.
When the count value of 34 is decreased by four, it is detected that the scale 10 is moving to the right in the figure, and the signal input from the waveform shaping circuit 48 this time is detected by the reference point detection sensor 46.
Is the reference point electro-magnetic characteristic changing portion 44b at the left end of the reference section 45b.
It is output to the position calculator 36 that the detected signal is.

Thus, in this embodiment, the magnetic sensors 20, 22 are
Even if is driven from any position on the scale 10, the position confirmation signal output circuit is output every time the reference point detection sensor 46 detects the reference point electro-magnetic characteristic changing portions 44a, 44b, 44c, .... Since 50 outputs the position confirmation signal to the position calculator 36, the position of the controlled object can be confirmed without performing the reset process, unlike the reference example (that is, the prior art). That is, regardless of the relative positions of the scale 10 and the magnetic sensors 20 and 22 at the start of use, when the scale 10 and the magnetic sensors 20 and 22 move relative to each other to some extent, the positions of the magnetic sensors 20 and 22 (positions to be controlled) You can know
A pseudo absolute (absolute) position detecting device can be provided.

By the way, the advantage of the absolute position detector is
It is always possible to know the absolute position. But,
Usually, when the control target moves a certain distance, it is often sufficient that the position of the control target can be specified by the information obtained during the movement. For example, when controlling a bucket of a construction machine, it is sufficient to know the bucket position while moving the bucket for several centimeters or tens of centimeters. Therefore, if the pseudo-absolute position detecting device of this embodiment is applied to a cylinder or the like of a construction machine, accurate position control can be performed without using an expensive absolute type position detecting device.
Further, in this embodiment, the scale 12 provided on the scale 10
Is used as the identification mark as it is, so that the step of attaching the identification mark can be omitted.

 FIG. 3 is an explanatory diagram of another reference example.

In FIG. 3, a plurality of reference point electro-magnetic characteristic changing portions 44a, 44b, 44c, ... Are provided along the scale 12 in the portion of the scale 10 where the scale 12 is not formed. The reference point electro-magnetic characteristic changing portions 44a, 44b, 44c, ... Are provided at equal intervals, and the reference sections 45a, 45b, 45c, .. The length of each is L. The reference marks 45a, 45b, 45c, ... Show identification marks 52a, 52b, 52c, between the reference point electro-magnetic characteristic changing portions 44a, 44b, 44c ,.
... is formed. These identification marks 52a, 52b, 52
c, ... are set so that the reference point detection sensor 46 can detect them.
It is formed by providing a different number of convex portions for each section and changing the electromagnetic characteristics of the scale 10.

A section identification circuit 54 is connected to the output side of a waveform shaping circuit 48 that shapes the output signal of the reference point detection sensor 46. A signal indicating the moving direction of the scale 10 is input from the direction discriminating circuit 32 to the section identifying circuit 54, and the reference point electromagnetic characteristic changing units 44a and 44b detected by the reference point detecting sensor 46 are input. , 44c, ... Corresponding to the reference sections 45a, 45b, 45c, ..., The positions are input to the position confirmation signal output circuit 50. Then, the position confirmation signal output circuit 50 takes in the count value of the up / down counter 34, outputs the position confirmation signal to the position calculator 36, and outputs the count adjustment signal to the up / down counter 34.

In the present embodiment configured as described above, when the scale 10 moves, the reference point detection sensor 46 causes the reference point electro-magnetic characteristic changing portions 44a, 44b, 44c, ... And the identification marks 52a, 52b, 52c ,.
... and are detected, and the detection signal is output to the waveform shaping circuit 48.
The waveform shaping circuit 48 shapes the output signal of the reference point detection sensor 46 into a rectangular wave and sends it to the section identification circuit 54.

The section identifying circuit 54 detects in which direction the scale 10 is moving based on the signal from the direction discriminating circuit 32, and detects the reference point based on the signal sent from the waveform shaping circuit 48. From the two signals that the sensor 46 detects the reference point electro-magnetic characteristic changing portion and the detection signal of the identification mark that is input during this period, the reference section that passes in front of the reference point detection sensor 46 is detected, and the reference inspection is performed. Output sensor
The position of the reference point electro-magnetic characteristic changing section 46 detected this time is sent to the position confirmation signal output circuit 50 as to which side of the reference section the control section is currently detecting which is the reference point electro-magnetic characteristic changing section.

The position confirmation signal output circuit 50 includes an up / down counter 34
If the count value of the up / down counter 34 when the reference point detection sensor 46 detects the reference point electro-magnetic characteristic changing portion is a predetermined value from the count value and the output signal of the section identification circuit 54, The confirmation signal is output to the position calculator 36. However, when the reference point detection sensor 46 detects the reference point electromagnetic characteristic changing portion, the position confirmation signal output circuit 50 detects that the count value of the up / down counter 34 deviates from a predetermined value due to the influence of noise or the like. , A position confirmation signal is output to the position calculator 36, and a signal for correcting the count value is output to the up / down counter 34.

Thus, in the present embodiment, the position confirmation signal output circuit 50 outputs not only the signal for confirming the position but also the signal for correcting the count value of the up / down counter 34,
More accurate position control becomes possible.

As shown in FIG. 4, the identification marks 52a, 52b, 52c, ... Representing the reference sections 45a, 45b, 45c, ... Are convex portions that make the output pulse width of the reference point detection sensor 46 different. Alternatively, another identification mark may be used.

By the way, the accuracy to obtain the position of the controlled object is
It depends on the processing accuracy of the unevenness (bit pattern) forming the scale 12 of 10 and the detection accuracy of the magnetic sensors 20 and 22.
In other words, the positional accuracy between the reference signal (incremental signal output by the magnetic sensors 20 and 22) called the normal clock and the signal indicating the position becomes a problem. That is, the position calculator 36 is adapted to output a position signal for each predetermined number of detection signals of the magnetic sensors 20 and 22, and the count value of the up / down counter 34 and the position signal output by the position calculator 36. Need to be synchronized.

However, there may be a case where the predetermined count value of the up / down counter 34 and the output of the position signal of the position calculator 36 are not synchronized due to variations in the mounting accuracy of the magnetic sensors 20 and 22. That is, for example, the position signal should be output to the tenth detection signal (incremental signal) output from the magnetic sensors 20 and 22, but the position signal should be output when the incremental signal is the ninth or eleventh signal. May be output.

Therefore, as in the above-described embodiment, the reference-point electromagnetic characteristic changing units 44a, 44b, 44c, ... Are provided, and the number of incremental signals is within a predetermined range from a predetermined value (for example, every 10 incremental signals). When outputting the position signal, when the number of incremental signals is in the range of 8 to 12), the position signal is output when the signal that detects the reference point electro-magnetic characteristic change portion is input, and the assembly accuracy and The signal processing can be made flexible. In this case, the above signal processing is first performed, and then the position signal is output at the count value corresponding to the above.

In each of the above-described embodiments, the construction machine has been described as an example, but the invention can also be applied to other equipment. [Advantages of the Invention] The pseudo absolute method of the prior art includes a reset mechanism. This divides a large scale at the reset position and performs incremental detection between the divisions. That is, it is only a division of the incremental detection. On the other hand, the present invention does not include a reset mechanism, but instead, for example, the absolute value from the origin is assigned to each reference point electromagnetic characteristic changing portion corresponding to the reset position of the prior art. Which one of the reference point electro-magnetic characteristic changing portions is equivalent can be determined by the number of scales in each reference section constituted by each reference point electro-magnetic characteristic changing portion. Therefore, in the present invention, when the position of each reference point electro-magnetic characteristic changing portion is detected, the absolute value of the position is obtained. Then, the position up to the next electromagnetism characteristic changing portion for each reference point, by the position calculator,
It is obtained by adding or subtracting an incremental value to or from the absolute value (note that addition or subtraction is distinguished by the direction of relative movement). That is, the present invention is no different from the absolute method. The present invention differs from the true absolute method in that the absolute value can be obtained even when the true absolute method is stationary, whereas in the present invention, the reference point detection sensor once uses two adjacent reference point electrical sensors. The only difference is that the absolute value can be obtained only after detecting the magnetic characteristic change portion, and once detected, the detection accuracy is no different from that of the true absolute type.

That is, according to the present invention, when the relative movement between the sensor and the scale occurs to some extent or more, the position can be surely known without resetting. Further, it is possible to obtain a highly accurate absolute value as in the case of an expensive absolute, although it has a simple and inexpensive incremental metal structure.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a linear position detecting device according to a reference example of the present invention, FIG. 2 is an explanatory diagram of an embodiment of the present invention, FIG. 3 is an explanatory diagram of yet another reference example, and FIG. It is explanatory drawing of the other reference example of the identification mark formed in the reference area | region divided by the electromagnetic characteristic change part for points. 10 …… Scale, 12 …… Scale, 18 …… Origin electromagnetism characteristic change part, 20,22 …… Magnetic sensor, 24 …… Origin detection sensor, 32 …… Direction discrimination circuit, 34 …… Up / down counter, 40 …… Switching circuit, 42 …… Signal detection circuit (one-shot circuit), 44a, 44b, 44c, 44d …… Reference point electro-magnetic characteristic change part, 45a, 45b, 45c …… Reference section, 46 …… Reference Point detection sensor, 50 ... position confirmation signal output circuit, 54 ... section identification circuit.

Claims (1)

[Scope of utility model registration request] 1. A graduation formed by periodically changing electro-magnetic characteristics, and a plurality of reference sections which are parallel positions different from the graduation position and include different graduation numbers and different lengths. A scale having reference point electro-magnetic characteristic changing portions provided at both ends of each reference section, a plurality of magnetic sensors arranged to be movable relative to the scale, and detecting the scale; A direction discriminating circuit that detects a direction of relative movement between the scale and the magnetic sensor based on an output signal of the sensor and outputs a count-up signal or a count-down signal, and counts by receiving an output of the direction discriminating circuit. An up / down counter that counts an up signal or a countdown signal, and a scale and a magnetic sensor that receive an output from the up / down counter A position calculator for calculating a position; and a reference point detection sensor that is arranged so as to be movable relative to each of the reference sections and that detects the reference point electro-magnetic characteristic change portion, While storing the number of graduations that can be arranged in each of the reference sections and the absolute value of each reference point electro-magnetic characteristic changing portion that forms each of the reference sections, the output signal of the up-down counter, and the reference point detection sensor, When the reference point detection sensor detects two reference point electro-magnetic characteristic changing portions before and after receiving the detection signal from the above, the count value of the output signal of the up / down counter and the previously stored values By specifying the reference section where the number of scales of the reference section is equal, the electromagnetism characteristic change portion for the reference point detected later is specified, and then the specified reference point is specified. A position confirmation signal output circuit that outputs the prestored absolute value corresponding to the electromagnetic characteristic changing unit for use as a position confirmation signal to the position calculator, and thereby outputs the position calculator as a pseudo absolute value. A linear position detecting device.