JP5294378B2 - Absolute linear encoder and actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compactible, inexpensive and reliable absolute type linear encoder, and to provide an actuator using the absolute type linear encoder. <P>SOLUTION: The absolute type linear encoder includes: an incremental linear scale section mainly formed by one incremental linear scale, and two detectors disposed at a phase difference interval of 90&deg;; and a magnetic absolute linear scale section mainly formed by an absolute linear scale having two or more sign origins at one fundamental pitch, and one or more detectors. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

The present invention relates to, for example, an absolute linear encoder used in a precision positioning system and an actuator using the absolute linear encoder. In particular, the apparatus can be made compact and signal transmission can be simplified. It relates to something that was devised.

In the precision positioning apparatus, for example, a linear encoder is used as a sensor for positioning feedback. This is due to the high accuracy and low cost of the linear encoder. However, the linear encoder that is widely used at present is an incremental type that requires an origin return operation. In the case of this type of incremental type linear encoder, it is necessary to perform an origin return operation when the apparatus is started or when a trouble occurs. Therefore, there has been a problem that the operating rate of the apparatus is lowered.

Therefore, it has been proposed to use an absolute linear encoder instead of the incremental linear encoder. This is because this type of absolute linear encoder does not require an origin return operation.

For example, Patent Literature 1, Patent Literature 2, and Patent Literature 3 disclose the absolute type linear encoder.
JP-A-5-80849 Japanese Patent Laid-Open No. 2003-83766 JP 2007-33245 A

The conventional configuration has the following problems.
First, the absolute linear encoders disclosed in Patent Document 1 and Patent Document 2 both have a problem in that the configuration is complicated and the cost is high. Further, there is a problem that it is difficult to make the linear scale part and the detection head part compact. Furthermore, there is a problem that signal transmission is complicated.
For example, in the case of an absolute linear encoder disclosed in Patent Document 1, a high resolution and a wide length measurement range are realized with a small number of tracks by using both a capacitance type and a photoelectric type. However, two systems are required for both the detection means and the code pattern.
Further, in the case of the absolute linear encoder described in Patent Document 2, it is possible to reduce to two sets of linear scales by using linear scales having different phase differences. However, a slightly complicated signal processing is required to secure the accuracy, and it has been difficult to achieve a compact size.
In addition, the absolute linear encoder described in Patent Document 3 is a magnetic type and has a relatively simple configuration of one scale or two scales, but in order to ensure high resolution and a sufficient stroke. Has the problem of requiring a large number of detectors. In addition, there is a problem that it is difficult to detect the magnetization because the length of the magnetization is short or there is a magnetization having a different length.

  In addition to the absolute linear encoders described in Patent Document 1, Patent Document 2, and Patent Document 3, there is one shown in FIG. In this case, a large number of code-type origins 103 are given to the absolute linear scale 101, thereby reducing the amount of movement of the detector for returning to the origin. Further, in order to distinguish the plurality of code type origins, another code type origin 105 is provided between the code type origins 103 and 103 that define both ends of the basic pitch P, whereby a plurality of code type origins are provided. The mold origin 103 is distinguished.

  However, the absolute type linear encoder shown in FIG. 5 also has a limit in reducing the amount of movement of the detector, specifically, the amount of movement is about 80 to 160 mm.

  The present invention has been made on the basis of the above points, and an object of the present invention is to provide an absolute linear encoder that is easy to make compact and is low in cost and highly reliable, and an actuator using such an absolute linear encoder. Is to provide.

In order to achieve the above object, an absolute type linear encoder according to claim 1 of the present invention is an incremental linear scale mainly composed of one incremental linear scale and two detectors arranged at a phase difference interval of approximately 90 degrees. An absolute linear scale having two or more sign-type origins in one basic pitch and one or more detectors as a main component, and the above incremental The two detectors of the linear scale unit output a substantially sine wave output signal. One of the codes of “1” or “0” of the absolute data is associated with one magnetization in one code. The same sign in the code corresponding to the magnetization of either “1” or “0” in the absolute data When continuous, the magnetization direction is reversed for each bit, and the magnetization direction is reversed even when the same code does not continue in the code corresponding to the magnetization of either “1” or “0” in the absolute data. And is magnetized .
The absolute linear encoder according to claim 2 is the absolute linear encoder according to claim 1, wherein the output signal of the incremental linear scale section is an A / B two-phase digital signal divided by a divider and having high resolution. It is characterized by this.
The absolute linear encoder according to claim 3 is characterized in that in the absolute linear encoder according to claim 1 , the output signal of the absolute linear scale unit is received in synchronization with the output signal of the incremental linear scale unit. Is.
An absolute linear encoder according to claim 4 is characterized in that, in the absolute linear encoder according to claim 3 , the output signal of the incremental linear scale portion used for the synchronization is a signal before division .
The absolute linear encoder according to claim 5 is the absolute linear encoder according to claim 3, wherein the output signal of the absolute linear scale portion is a single-phase digital signal .
An absolute linear encoder according to claim 6 is the absolute linear encoder according to claim 1, wherein the incremental linear scale has a detection head movable relative to the incremental linear scale, and the incremental linear scale. The detection head unit includes a divider that divides the output signal of the unit and a synchronization circuit that outputs the output signal of the absolute linear scale unit in synchronization with the output signal of the incremental linear scale unit. is there.
Further, absolute type linear encoder according to claim 7 is the absolute type linear encoder according to claim 1, wherein an output signal is two digital signals from the incremental linear scale Lumpur unit, the output signal from the absolute linear scale section Is one digital signal .
The absolute linear encoder according to claim 8 is the absolute linear encoder according to claim 1 , wherein all of the two or more code type origins in the basic pitch are closer to one side than the center including the center of the basic pitch. It is characterized by that.
An actuator according to claim 9 is characterized in that the absolute type linear encoder according to any one of claims 1 to 8 is used .

As described above, the absolute linear encoder according to the first aspect of the present invention is an incremental linear scale section mainly composed of one incremental linear scale and two detectors arranged at a phase difference interval of approximately 90 degrees. And an absolute linear scale having two or more code-type origins in one basic pitch and an absolute linear scale portion mainly composed of one or a plurality of detectors. Therefore, the combination of the positions of the code type origins in the basic pitch can be greatly increased, and a long stroke can be obtained even if the basic pitch is narrowed.
The absolute linear encoder according to claim 2 is the absolute linear encoder according to claim 1, wherein the two detectors of the incremental linear scale section output substantially sinusoidal output signals. The resolution can be increased by electric signal processing (phase division or the like) without reducing the scale pitch.
The absolute linear encoder according to claim 3 is the absolute linear encoder according to claim 2, wherein the output signal of the incremental linear scale unit is divided by a divider and is a high-resolution A and B phase digital signal. Therefore, high resolution can be realized.
The absolute linear encoder according to claim 4 is the absolute linear encoder according to claim 1, wherein the output signal of the absolute linear scale unit is received in synchronization with the output signal of the incremental linear scale unit. The desired processing can be executed with a simple configuration.
The absolute linear encoder according to claim 5 is the absolute linear encoder according to claim 4, wherein the output signal of the incremental linear scale portion used for the synchronization is a signal before division, so that stable signal detection is possible. Become.
The absolute linear encoder according to claim 6 is an absolute linear encoder according to claim 4, wherein the output signal of the absolute linear scale portion is a single-phase digital signal, so that signal transmission is facilitated.
An absolute linear encoder according to claim 7 is the absolute linear encoder according to claim 1, wherein the incremental linear scale includes a detection head movable relative to the incremental linear scale and the absolute linear scale. Since the detection head unit incorporates a divider that divides the output signal of the unit and a synchronization circuit that outputs the output signal of the absolute linear scale unit in synchronization with the output signal of the incremental linear scale unit, transmission delay between signals Therefore, signal transmission is facilitated and reliability is improved.
An absolute linear encoder according to claim 8 is the absolute linear encoder according to claim 1, wherein the output signal from the incremental linear scale section is two digital signals, and the output signal from the absolute linear scale section is Since it is one digital signal, signal transmission is facilitated and reliability is improved.
The absolute linear encoder according to claim 9 is the absolute linear encoder according to claim 1, wherein one magnetization corresponds to one bit in the sign of either “1” or “0” of the absolute data. Since it is configured, stable detection is possible.
An absolute type linear encoder according to claim 10 is the absolute type linear encoder according to claim 9, wherein the code corresponding to the magnetization of either “1” or “0” of the absolute data is 1 when the same code continues. Since the configuration is such that the magnetization direction is reversed for each bit, it is possible to prevent the situation that the sensor output becomes insufficient and the detection becomes unstable.
The absolute linear encoder according to claim 11 is the absolute linear encoder according to claim 10, wherein the same code does not continue in the code corresponding to the magnetization of either “1” or “0” of the absolute data. Since the magnetization direction is reversed, the sensor detection tolerance can be increased and more stable detection can be achieved.
An absolute linear encoder according to claim 12 is the absolute linear encoder according to claim 1, wherein all of the two or more code type origins in the basic pitch are closer to one side than the center including the center of the basic pitch. Therefore, the code origin corresponding to the basic pitch can be reliably identified.
The actuator according to claim 13 uses the absolute linear encoder according to any one of claims 1 to 12, so that the actuator can be made compact and low in cost and highly reliable. Can do.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. This embodiment shows an example in which the present invention is applied to a uniaxial actuator. FIG. 1 is a plan view showing the overall configuration of the actuator according to the present embodiment.
First, there is a housing 1, and a slider 3 is attached to the housing 1 so as to be movable in the left-right direction (arrow a direction) in FIG. A ball screw 5 is housed in the housing 1 and a drive motor 7 is installed. The ball screw 5 is connected to the output shaft of the drive motor 7 and is configured to be rotationally driven by the drive motor 7.
In some cases, the ball screw 5 and the output shaft of the drive motor 7 are integrated.

  A ball nut (not shown) is screwed and arranged on the ball screw 5 in a state where its rotation is restricted. The slider 3 already described is fixed to this ball nut. Guides 9 and 11 are installed in the housing 1, and the guides 9 and 11 guide the movement of the slider 3 in the left-right direction in FIG. Then, by rotating the drive motor 7 in an appropriate direction, the ball screw 5 rotates in the same direction, whereby the slider 3 is guided by the guides 9 and 11 through the ball nuts in an appropriate direction (FIG. 1). Move in the middle / left / right direction).

  A linear scale portion 21 is installed on the guide 11 side, while a detection head portion 23 is attached to the slider 3. A controller unit 25 is installed at a location separated from the actuator.

Next, the configuration of the linear scale unit 21, the detection head unit 23, and the controller unit 25 will be described in detail. FIG. 2 shows the linear scale unit 21, the detection head unit 23, and the controller unit 25 extracted from FIG.
First, the linear scale unit 21 includes an incremental linear scale 31 and an absolute linear scale 33. The incremental linear scale 31 is configured as a magnetic type having a pitch of 800 μm, for example. That is, the incremental linear scale 31 has a configuration in which a plurality of magnetized portions 31a are connected at a pitch of 800 μm. Further, the magnetized portions 31a and 31a adjacent to each other are reversed in magnetization. In the figure, the arrow indicates the direction of magnetization, the base of the arrow is the S pole, and the tip of the arrow is the N pole. It is.

On the other hand, the absolute linear scale 33 is configured so that one bit is 800 μm, the code type origins 33a ₁ and 33a ₄ for defining both ends of the basic pitch P, and two code types provided in the basic pitch P. The configuration includes the origins 33a ₂ and 33a ₃ . These code-type origins 33a ₁ , 33a _4, 33a ₂ , 33a ₃ are configured as magnetized portions similar to the magnetized portion 31a of the incremental linear scale 31 already described.

  Looking at the configuration on the detection head unit 23 side, first, two detectors corresponding to the incremental linear scale 31, that is, an A-phase detector 35 and a B-phase detector 37 are installed. These two A-phase detectors 35 and B-phase detectors 37 are arranged with a phase difference interval of 90 ° when the pitch interval of the incremental linear scale 31 is 360 °. The incremental linear scale 31, the two phase A detectors 35, and the phase B detector 37 constitute an incremental linear scale unit.

  The A-phase detector 35 and the B-phase detector 37 are magnetic. Specifically, it uses an MR sensor in which two MR elements (arranged in a state separated by ½ of the length of the magnetized portion 31a) are combined in a bridge, thereby improving temperature characteristics and The output is increased. Further, the A-phase detector 35 and the B-phase detector 37 are arranged with a phase difference interval of 90 ° as described above. By using this MR sensor, the output signals from the A phase detector 35 and the B phase detector 37 become substantially sine waves. That is, the A-phase detector 35 outputs a sine wave signal, and the B-phase detector 37 outputs a cosine wave signal.

The detection head unit 23 is provided with one Z-phase detector 39 corresponding to the absolute linear scale 33. The Z-phase detector 39 is also a magnetic type like the A-phase detector 35 and the B-phase detector 37 already described. That is, like the A-phase detector 35 and the B-phase detector 37, an MR sensor in which two MR elements (arranged in a state separated by ½ of the length of the magnetized portion 33a) are assembled in a bridge. As a result, temperature characteristics are improved and output is increased. The absolute linear scale 33 and one Z-phase detector 39 constitute an absolute linear scale section.
In the present embodiment, one Z-phase detector 39 is used, but a configuration using two or more Z-phase detectors is also conceivable.

The detection head unit 23 is provided with a divider 41 and a synchronization circuit 43. Detection signals from the A-phase detector 35 and the B-phase detector 37 are input to the divider 41 and the synchronizing circuit 43, respectively. A detection signal from the Z-phase detector 39 is also input to the synchronization circuit 43. The signals from the divider 41 and the synchronizing circuit 43, that is, the A-phase signal and the B-phase signal from the divider 41 and the Z-phase signal from the synchronizing circuit 43 are sent to the line driver 45 and the line receiver 47 of the controller unit 25. Via the controller 49.
The above is the schematic configuration of the actuator according to the present embodiment and the absolute linear encoder used therein. In the following, the configuration of each part will be described in more detail with the action and effect.

First, the code-type origins 33a ₁ , 33a _4, 33a ₂ and 33a ₃ of the absolute linear scale 33 will be described in detail. As shown in FIG. 5 used in the description of the conventional example, conventionally, one code type origin 105 is arranged between the code type origins 103 and 103 that define both ends of the basic pitch P. Thus, when there is one code origin in the basic pitch P, there is a limit to the number of differences in position.
Therefore, in the case of the present embodiment, the configuration is such that the two code origins 33a ₂ and 33a ₃ are provided in the basic pitch P, whereby the code origins 33a ₂ and 33a ₃ in the basic pitch P are provided. The combination of positions is greatly increased. As a result, an absolute linear scale having a long stroke can be configured even if the basic pitch P is narrowed.

At that time, the code type origins 33a ₁ and 33a ₄ that define both ends of the basic pitch P and the code type origins 33a ₂ and 33a ₃ provided in the basic pitch P are both the same origin, and as such, The two cannot be distinguished. Therefore, in the case of the present embodiment, the code type origins 33a ₂ and 33a ₃ arranged in the basic pitch P are arranged closer to one side than the center including the center of the basic pitch P (this embodiment). 2, the code type origin for determining the basic pitch P is defined as 33a ₁ , 33a ₄ and the code in the basic pitch P. The mold origin is distinguished from 33a ₂ and 33a ₃ .

More specifically, in the case of the present embodiment, the code origins 33a ₂ and 33a ₃ in the basic pitch P are all arranged on the right side in the basic pitch P in FIGS. At that time, when the Z-phase detector 39 is moved from the left side to the right side in FIGS. 2 and 3, the distance (incremental scale 31) between the code type origin 33 a ₁ at the leftmost end of the basic pitch P and the next code type origin 33 a _2. Is counted as 1/2 or more of the basic pitch P. The code type origin having such a distance is not other than the code type origin 33a ₁ and the code type origin 33a ₂ , thereby identifying the code type origin 33a ₁ . If the leftmost code type origin 33a ₁ can be identified, the Z-phase detector 39 is moved to the right in FIGS. 2 and 3 for the other code type origins 33a ₂ , 33a ₃ and 33a ₄ . It can be detected sequentially.

For example, the basic pitch P is set to 24 mm, and the magnetization lengths of the code origins 33a ₁ , 33a _4, 33a ₂ and 33a ₃ are set to 0.8 mm. Further, the code type origins in the basic pitch P are set to _two code type origins 33a ₂ and 33a ₃ as in the present embodiment. At that time, there are 81 combinations of the positions of the code type origins 33a ₂ and 33a ₃ as shown in the following formula (I).
That is, ₁₄ C ₂ = 81-(I)
As a result, as shown in the following formula (II), it is possible to cope with a stroke of about 1.9 m.
24mm × 81 = 1944mm --- (II)
Incidentally, if there are three code type origins in the basic pitch P, there are 364 combinations of the positions of the three code type origins as shown in the following equation (III).
₁₄ C ₃ = 364 --- (III)
As a result, as shown in the following formula (IV), it is possible to cope with a stroke of about 8.7 m.
24mm × 364 = 8736mm --- (IV)

Therefore, in the conventional example, the moving distance of the detector is as long as 80 to 160 mm, but in the case of the present embodiment, the number of code type origins in the basic pitch P is increased by 1 to 2, for example. By using two or three, the moving distance of the Z-phase detector 39 can be greatly reduced to 24 to 48 mm.

In addition, as described above, the incremental linear scale 31 is configured with a pitch of 800 μm and has a relatively coarse configuration. The divider 41 is provided in order to improve the resolution of the incremental linear scale 31 having such a rough configuration.
Incidentally, in this embodiment, the resolution is improved to 1 μm by dividing into 800 parts.

That is, two substantially sinusoidal output signals having a phase difference of approximately 90 degrees are output from the A-phase detector 35 and the B-phase detector 37, and they are phase-divided by the divider 41. The divided 90-degree phase difference A-phase signal and B-phase signal are output as a 90-degree phase difference signal with a pitch of 4 μm, 1/200 times the original signal, and include information on the direction of travel. It is designed not to raise the frequency. The A-phase signal and the B-phase signal having a pitch of 4 μm are further divided by a factor of 1/4 after being received by the controller 49, and as a result, a high resolution of 1 μm is achieved.

Next, synchronization by the synchronization circuit 43 will be described. When the magnetization of the absolute linear scale 33 is to be detected by the Z-phase detector 39 using an MR sensor, uniform output cannot be obtained over the entire area of 1 bit in the 1-bit magnetization. Therefore, in the present embodiment, the incremental linear scale 31 and the absolute linear scale 33 are synchronized, and the A phase detector 35, the B phase detector 37, and the Z phase detector 39 are also synchronized and disposed. As a result, the absolute linear scale signal is separated one bit at a time in synchronism with the incremental linear scale signal.

More specifically, in this embodiment, the arrangement is such that the pitch of the incremental linear scale 31 corresponds to 1 bit of the absolute linear scale 33, and the A phase detector 35 of the incremental linear scale portion is arranged in the absolute linear scale portion. It arrange | positions so that it may become the same phase as the Z phase detector 39. FIG. Accordingly, as shown in FIG. 4, when the “rise” or “fall” change of the B phase detector 37 and when the A phase detector 35 is “High (1)”, the absolute linear scale is used. If 33 signals are read, they can be detected separately bit by bit.

Further, the resolution of the output signals of the A-phase detector 35 and the B-phase detector 37 in the incremental linear scale section is improved by the divider 41 as described above. If an attempt is made to synchronize the signal of the absolute linear scale portion with the divided high resolution signal, there is a concern that the signal is not stable and a reading error occurs. That is, the phase of the incremental signal cannot be specified with a high-resolution signal, and therefore, the signal may be detected near the signal inversion boundary or near the end of magnetization of the absolute linear scale 33. Therefore, a case where the signal is not stable occurs and a reading error occurs.

Therefore, in the present embodiment, as shown in FIG. 2, the incremental signal from the phase A detector 35 and the phase B detector 37 before being divided by the divider 41 is configured to be taken into the synchronization circuit 43. Thus, when the A-phase detector 35 is directly above the center of the 400 μm wide “High (1)” signal, the signal of the Z-phase detector 39 immediately above the center of the absolute bit can be read.

The synchronization circuit 43 that outputs the output signal of the absolute linear scale unit in synchronization with the output signal of the incremental linear scale unit is, as described above, at the time of “rise” or “fall” change of the B phase detector 37, and , When the A-phase detector 35 is “High (1)”, the signal of the Z-phase detector 39 of the absolute linear scale unit is fetched and latched. Therefore, the output signal of the Z-phase detector 39 is converted into a single-phase digital signal by the synchronization circuit 43, and becomes a single-phase digital signal similar to the origin signal of a normal incremental linear encoder. That is, the output is the same as the output signal of the normal incremental linear encoder together with the incremental output signals from the A phase detector 35 and the B phase detector 37. As a result, complicated signal transmission for each company is not required as in a general absolute encoder, and signal transmission is facilitated.

Further, by incorporating the divider 41 and the synchronizing circuit 43 in the detection head unit 23, the signals output from the detection head unit 23 are only the A phase digital signal, the B phase digital signal, and the Z phase digital signal (line driver 45). When used, + A, -A, + B, -B, + Z, -Z). As a result, the transmission delay between signals is small and reliability can be ensured, and the input in the controller 49 becomes easy and the cost can be reduced. it can.

Next, the configuration of magnetization on the scale in the present embodiment will be described in detail with reference to FIG. In the case of the incremental linear scale 31 shown in the upper side of FIG. 4, all the magnetized portions 31a have the same length, and the magnetization directions of the adjacent magnetized portions 31a and 31a are reversed from each other. ing. In the present embodiment, the length of one magnetized portion 31a is set to 800 μm.

In the case of this embodiment, one magnetized portion 33 a is associated with one bit of the absolute linear scale 33. The length of the magnetized portion 33 a is set to be the same as that of the magnetized portion 31 a of the incremental linear scale 31.

Incidentally, in the invention disclosed in Patent Document 4, the length of the magnetized portion of the absolute linear scale is set to ½ of the length of the magnetized portion of the incremental. In the case of the invention described in Patent Document 5, the length of the magnetized portion of the absolute linear scale is set to be less than 1 or several times the length of the magnetized portion of the incremental.
Japanese Patent No. 3454002 JP 2007-33245 A

However, in the detection of the magnetization, the magnitude of the magnetic flux returning from the N pole to the S pole of the magnetization is detected by a magnetic sensor such as an MR element, the magnetization length varies, and the scale If the gap between the sensors is kept constant, the sensor output will fluctuate significantly. For example, when the magnetization length is halved, the sensor output becomes half or less. Conversely, even if the length of the magnetization is doubled, a significant decrease in sensor output is inevitable. Therefore, it is preferable to make the length of magnetization constant, and in the case of the present embodiment, the length of the magnetized portions 31a and 33a is set constant from such a viewpoint.

In the present embodiment, as shown in FIG. 4, the absolute linear scale 33 is magnetized by one corresponding to the data code “1” (1 bit), and the data code “0” Not magnetized.
The opposite case may be employed in which the data code “0” is magnetized and the data code “1” is not magnetized.
The MR sensor output is shown above and below the scale in FIG. In this sensor output, one magnetized portion 31a corresponds to one cycle and a phase of 360 degrees.

In the case of the absolute linear scale 33 in the present embodiment, although not shown, the magnetization direction is reversed bit by bit at consecutive identically-signed portions, specifically, “111” portions. Yes. If this is not reversed, the magnetization becomes long, and the sensor output becomes insufficient, so that stable detection cannot be performed. Also, the code type origins can be adjacent (for example, “11”, “111”, “1111”), thereby increasing the number of combinations of the positions of the code type origins within the basic pitch P. .
In addition, it is desirable to reverse every magnetization except for the continuous identical sign portion. For example, as shown in FIG. 4, when there is only 1 bit between the magnetized parts as in “101”, the leakage flux from the left and right magnetized parts is in the “0” sign part in the same magnetization direction. Since they are added together, the sensor detection margin can be improved by reversing the magnetization direction. Therefore, in this embodiment, the magnetization direction is reversed in such a case.

FIG. 4 is a diagram showing the relationship between the incremental linear scale 31 and the absolute linear scale 33 and each signal. Above the incremental linear scale 31, an A phase detector 35 and a B phase detector having a phase difference of 90 degrees. 37, and the digital conversion output thereof, and the output of the Z-phase detector 39 and the digital conversion output thereof are shown below the absolute linear scale 33. When the B digital output is “rising” or “falling” and the A digital output is “High (1)”, the Z-phase detector 39 detects the magnetic flux at the center of magnetization (bit center). . The area where the absolute data code is “1” corresponds to the middle of the Z digital output, and the Z signal is detected with a sufficient margin.

Here, when the operation as the absolute linear encoder shown in FIG. 2 is arranged, the A-phase signal, the B-phase signal and the Z-phase signal having the phase difference of 90 degrees generated by the detection head unit 23 are converted into the line driver 45, the line The data is input to the controller 49 via the receiver 47. In the absolute position detection immediately after the power is turned on, the detection head unit 23 is moved relative to the linear scale unit 21 by driving the slider 3 in one direction. At that time, the Z phase signal is taken into the controller 49 every 800 μm count of the A phase signal and B phase signal which are incremental signals (every 800 counts of 1 μm resolution pulse). The absolute position (absolute data) corresponding to the fetched data is obtained from a correspondence table or calculation formula created in advance.

The absolute position thus obtained is set as the offset value of the up / down counter, thereby completing the position detection immediately after the power is turned on. All of these processes are performed by the software sequence of the controller 49, thereby making it possible to reduce the size and cost.

Note that once the absolute position is set in the up / down counter, the position information can be obtained by counting in the up / down counter using only the A-phase signal and B-phase signal which are incremental signals.

Further, when the operation of the actuator shown in FIG. 1 is seen, as described above, the absolute position is detected by software processing in the controller 49, set as an initial value in the up / down counter inside the controller 49, and the up / down counter is set. The position information is obtained by operating. The controller 49 controls the drive motor 7 based on the position information to position the slider 3 at the command position.

The present invention is not limited to the one embodiment.
For example, in the case of the one embodiment, one Z-phase detector is used, but the present invention is not limited to this. For example, it is conceivable to use two, in which case there are two Z-phase signals, but by installing two Z-phase detectors separated by a basic pitch interval, for example, the longest longest case Can be greatly reduced (minimum 25%).
In the above embodiment, the basic pitch P is constant. However, the present invention can be applied even when the basic pitch P is gradually increased or decreased.
Further, in the case of the above-described embodiment, the case where the number of code type origins in the basic pitch P is two is described as an example, and the case of three at the same time is also mentioned. Is also possible.
In the case of the above-described embodiment, the magnetic scale is taken as an example, but the present invention can be similarly applied to an optical scale (“0” and “1” signs correspond to black and white).
In addition, the illustrated configuration is merely an example, and various modifications are possible.

The present invention relates to an absolute type linear encoder and an actuator using the absolute type linear encoder, and more particularly to a device devised so as to make the device compact and simplify signal transmission. It is suitable for an absolute type linear encoder used in a precision positioning system and an actuator using the absolute type linear encoder.

It is a figure which shows one embodiment of this invention, and is a top view which shows the structure of an actuator. It is a figure which shows one embodiment of this invention, and is a block diagram which shows the structure of the absolute linear encoder used for the actuator. It is a figure which shows one embodiment of this invention, and is a figure which shows the structure of the magnetization of an incremental linear scale part and an absolute linear scale part. It is a figure which shows one embodiment of this invention, and is a figure for demonstrating the synchronization of the signal of an incremental linear scale part, and the signal of an absolute linear scale part. It is a figure which shows a prior art example, and is a figure which shows the structure of an absolute linear scale.

Explanation of symbols

1 housing 3 slider 5 Ball screw 7 driven motor 9 guides 11 guide 21 linear scale 23 detecting the head unit 25 the controller unit 31 increments the linear scale 31a magnetized portion 33 absolute linear scale _{33a 1, 33a 4, 33a 2} , 33a 3 code type origin 35 Phase A detector 37 Phase B detector 39 Phase Z detector 41 Divider 43 Synchronization circuit 45 Line driver 47 Line receiver 49 Controller

Claims (9)

An incremental linear scale unit mainly composed of one incremental linear scale and two detectors arranged at a phase difference interval of approximately 90 degrees;
An absolute linear scale having two or more code-type origins in one basic pitch and one or more detectors in one basic pitch,
Equipped with,
The two detectors of the incremental linear scale unit output a substantially sine wave output signal,
In the code of either “1” or “0” in the absolute data, one magnetization corresponds to one code bit,
In the code corresponding to the magnetization of either “1” or “0” in the absolute data, when the same code continues, the magnetization direction is reversed for each bit and magnetized.
An absolute linear encoder characterized in that magnetization is performed by reversing the direction of magnetization even when the same code does not continue in a code corresponding to magnetization of either “1” or “0” of absolute data . The absolute linear encoder according to claim 1,
An absolute linear encoder characterized in that the output signal of the incremental linear scale section is an A / B two-phase digital signal divided by a divider and having high resolution . The absolute linear encoder according to claim 1 ,
An absolute linear encoder, wherein the output signal of the absolute linear scale unit is captured in synchronization with the output signal of the incremental linear scale unit . The absolute linear encoder according to claim 3 ,
An absolute linear encoder, wherein an output signal of the incremental linear scale unit used for the synchronization is a signal before division . The absolute linear encoder according to claim 3 ,
An absolute linear encoder, wherein the output signal of the absolute linear scale section is a single-phase digital signal . The absolute linear encoder according to claim 1 ,
There is a detection head that can move relative to the incremental linear scale and the absolute linear scale,
A divider that divides the output signal of the incremental linear scale unit and a synchronization circuit that outputs the output signal of the absolute linear scale unit in synchronization with the output signal of the incremental linear scale unit are incorporated in the detection head unit. Absolute type linear encoder. The absolute linear encoder according to claim 1,
It said incremental linear skating output signal from the pole tip is two digital signals, absolute type linear encoder, wherein the output signal from the absolute linear scale unit is one of the digital signal. The absolute linear encoder according to claim 1,
Absolute type linear encoder all two or more code type origin within the fundamental pitch is characterized that you have displaced in one of the center, including the center of the base pitches. An actuator using the absolute linear encoder according to any one of claims 1 to 8 .

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