JPH04133107A - Position detecting device for linear driving shaft - Google Patents

Abstract

PURPOSE:To execute the origin reset operation by a minute amount and in a short time even if a table exists in any position in an operation range by providing a proximity sensor for detecting an absolute position on several parts in an operation range of a linear driving shaft. CONSTITUTION:When a moving command value is delivered to a driver 2 from a positioner 1, a motor 4 is driven to rotate by the driver 2, and a ball screw 7 connected to a motor shaft is also driven to rotate simultaneously as indicated with an arrow 15. In connection with the rotation of the ball screw 7, a table 5 into which a ball screw nut is integrated executes a linear motion in the plus direction and the minus direction as indicated with an arrow 11. Four pieces of proximity sensors 6a, 6c, 6d and 6e are attached at an equal interval so that only one piece of proximity sensor exists in a distance in which the motor 4 executes one rotation and the table 5 moves. The proximity sensors 6a,6f detect a limit of an operation range of the table 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a position detection device for a linear drive shaft in an industrial machine having a structure having a linear drive shaft as a component.

[Conventional technology]

A conventional technique for a position detection device for a linear drive shaft will be explained with reference to FIGS. 5 and 6.

FIG. 5 is a perspective view showing the configuration of a drive shaft that performs general linear motion.

When a movement command value is passed from the positioner 1 to the driver 2, the motor 4 is driven by the driver 2.

The angle of the motor 4 is detected by an encoder 6.

When the motor 4 is driven, the ball screw 7, which is a linear drive shaft connected to the motor shaft, is also simultaneously driven as shown by the arrow 15, and the table 5 in which the ball screw nut is incorporated is moved as shown by the arrow 11. It moves in a straight line in the positive and negative directions.

In this linear drive shaft position detection method, proximity sensors 6a, 6b, and 6C that react to metal, for example, are arranged at three locations on the plate 12 along the linear drive shaft. These proximity sensors 6a, 6b, 6
C reacts to the dog 5a attached to the table 5. Additionally, the proximity sensor 6a serves to detect the minus side operating range limit of the table 5, the proximity sensor 6b serves to start searching for the origin of the table 5, and the proximity sensor 6C serves to detect the plus side operating range limit of the table 5.
The encoder 3 detects its own origin position based on the detection signal of the proximity sensor 6b.

Detecting the origin of the linear drive shaft, that is, the origin position of the table 5 means detecting the origin of the encoder 6.

A method for detecting the origin of the encoder 3 will be explained using FIG. 6.

Figure 6 shows an incremental type encoder generally used in linear drive mechanisms.

A circular rotating plate 22 is fixed to the rotating shaft 21 of the motor. The rotary plate 22 has slits 25a equally divided on the circumference, and an origin signal slit 24a cut at one location inside the slits 25&. A fixed plate 23 is fixed apart from and parallel to the rotating plate 22. The fixed plate 26 has a slit 25b and an origin signal slit 24b, which are respectively carved at positions relative to the slit 251L and the origin signal slit 24a provided on the rotary plate 22.

In addition, the sleeves of the rotating plate 22 and the fixed plate 26) 25&, 25b
, and the origin signal slits 24a, 24b have a shape that allows light to pass therethrough, and the other portions block light.

The light emitting diodes 26a and 26b that emit light and the photodiodes 271L and 27b that receive and take light are each used in pairs, and the light emitting diodes 26a and photodiodes 27a are connected to the origin signal sleeves 1-24 & 24b.
Fix it facing the position on the straight line connecting. The light emitting diode 26b and the photodiode 27b are fixed facing each other at positions on the straight line connecting the origin signal slits 24a and 24b and the sleeves 251L and 25b. The light from the light emitting diode 26b passes through these slits when the fixed plate 23 and the slits 25 & 25b of the rotating plate 22 match, and the light emitted from the light emitting diode 26b passes through the slits 251L and 251L.
, 25b do not match. sleeve) 25a
, 25b is converted into an electrical signal by the 7-otodiode 27b.

Similarly, the light from the light emitting diode 26a that has passed through the origin signal slits 24a and 24b is received by the photodiode 27& and converted into an electric signal. In other words, the light received by the receiver becomes a pulse signal.

What has been described above is the configuration of an incremental encoder. Now, the method of detecting the origin of the encoder 6 is to detect the origin every one revolution of the rotation axis using the light emitting diode 26a and the photodiode 27& when the two origin signal slits 24 & 24b overlap. On the other hand, the light emitting diode 26b and the photodiode 27b detect the rotation angle from the reference position (origin signal sleeve) 24& by the number of pulses.

Output signals from the proximity sensor and encoder detected by the apparatus configured as described above are schematically shown in the time chart of FIG. 7. The signal 8a on the time chart 8 is the proximity sensor 6a, and the signal 8b is the proximity sensor 6.
b, the signal 8c is the detection signal of the proximity sensor 6C, the pulse signal on the time chart 9 is the detection signal of the photodiode 27b shown in FIG. 6, and the origin pulse signal on the time chart 10 is the detection signal of the photodiode 27a. Each signal corresponds to the other.

The return-to-origin operation by the apparatus shown in FIG. 5 will be explained using FIG. 7. In the following explanation, the installation distance from the proximity sensor 6a to the proximity sensor 6C, which is the stroke range of the table 5, is 9Qmm, and the lead pitch of the ball screw 7 is 2.
It is assumed that the motor 4 operates in the range of 0 to 4.5 rotations when the rotation angle is 0 mm.

The origin return operation is started in the direction of the arrow 16 from the position of the table 5 drawn by the broken line 12 (and the proximity sensor 6b for starting the origin search detects the dog 5a, and the encoder 3
searches for the origin position. and photodiode 27a
The return-to-origin operation is completed upon detection of the signal , and the table 5 stops at the position indicated by the solid line 14. At this time, the moving distance C of the table 5 from the start to the end of returning to the origin is approximately 70
It is mm.

[Problem to be solved by the invention]

As explained using FIG. 6, the function of the incremental encoder is to count pulse signals generated by passing and blocking light, so it can only measure relative positions. Therefore, as shown in FIG. 5, a proximity sensor 6a detecting the position of the table 5,
It is necessary to attach 6b and 6C and to detect the zero position of the origin, that is, to return to the origin.

Return to origin must be performed when the power is turned on or whenever a mechanical or electrical problem occurs, and the return to origin operation takes time and effort. If the distance between the table 5 and the proximity sensor 6b for starting the origin search is long, it will take even more time.

In addition to the incremental type described with reference to FIG. 6, there are other types of encoders, including an absolute type that can detect absolute positions without requiring return to origin, but these are more expensive than the incremental type. The reason for this is that dividing the slits in the rotary plate into tracks makes the slit pattern complicated, and the structure becomes complicated as the number of optical elements increases to receive light for each track, and mechanical and electrical adjustments are required. This is because the difficulty level increases. It is also possible to store data obtained by counting pulse signals in an incremental manner using a battery backup method, but this is not practical due to power consumption issues.

An object of the present invention is to solve the above problems and provide a position detection device for a linear drive shaft that can detect the position of the linear drive shaft in a short time.

[Means to solve the problem]

In order to achieve the above object, the linear drive shaft position detection device of the present invention is characterized by the following configuration.

(b) A linear drive shaft that rotates with the rotation of the motor, a chifur attached to this linear drive shaft that performs linear motion, a dog that is fixed to this table, and a device that detects this dog and moves in the axial direction of the linear drive shaft. and a plurality of proximity sensors provided.

(b) A linear drive shaft that rotates due to the rotation of the motor, a table attached to the linear drive shaft that performs linear motion, and a plurality of proximity sensors installed perpendicular to the table;
and a dog fixed along the axial direction of the linear drive shaft.

〔Example〕

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

[Embodiment 1] FIG. 1 is a perspective view showing a linear drive shaft position detection device in a first embodiment of the present invention.

When a movement command value is transmitted from the positioner 1 to the driver 2, the motor 4 is rotationally driven by the driver 2, and the pole screw =--7 connected to the motor shaft is simultaneously rotationally driven as shown by the arrow 15. Incidentally, the angle of the motor 4 is detected by an encoder 3, and an incremental type shown in FIG. 6 is adopted.

As the ball screw 7 rotates, the table 5 in which the ball screw nut is installed performs linear motion in the plus and minus directions as indicated by arrows 11. This table 5 is provided with a dog 5a made of metal. Proximity sensors 6&, 6b for detecting the dog 5a,
6c, 6d, 6e, 6f are plates 1 along the linear drive axis.
It is fixed at 6. Proximity sensors 6b, 6C, 6d, 6
The four sensors e are mounted at equal intervals so that only one proximity sensor is within the distance that the table 5 moves when the motor 4 makes one revolution. In other words, the proximity sensor 6b,
Place 6C, 6d, and 6e. The roles of the proximity sensors are that the proximity sensors 6a and 6f detect the limits of the operating range of the table 5, the proximity sensor 6a detects the minus limit, the proximity sensor 6f detects the plus limit, and the proximity sensor 6b detects the limit on the plus side. , 6c, 6d, and 6e start the origin search.

The time chart of FIG. 2 schematically shows the output signals from the proximity sensor and encoder detected by the apparatus having the configuration shown in FIG. 1 as described above.

This will be explained below using FIG. 1 and FIG. 2.

The signal 8a on the time chart 8 is the proximity sensor 6a,
Signal 8b is proximity sensor 6b, signal 8C is proximity sensor 6C
1 signal 8d is the proximity sensor 6d, signal 8e is the proximity sensor 6
e, the signal 8f is the detection signal of the proximity sensor 6f, the nox signal on the time chart 9 is the detection signal of the photodiode 27b shown in FIG. 6, and the origin pulse signal on the time chart 10 is the detection signal of the photodiode 27a. This corresponds to each detection signal.

In the following explanation, the installation distance from the proximity sensor 6a to the proximity sensor 6f, which is the stroke range of the table 5, is 9.
Qmm, lead pitch of ball screw 7 to 20mm
It is assumed that the motor 4 operates in the range of 0 to 4.5 rotations.

The position at which the encoder 6 returns to its origin when the proximity sensor 6e detects the dog 5a is a point where the motor has rotated three times from the zero origin position. Therefore, it is necessary to register the distance traveled by the table 5 in the positioner 1 as an offset amount when the motor rotates three times at the position returned to the origin based on the detection signal of the proximity sensor 6e. Similarly, when the detection signal from the proximity sensor 6d causes the motor to return to its origin, the motor makes two rotations to determine the distance that the table 5 travels, and when it returns to its origin based on the detection signal from the proximity sensor 6C, the motor makes one rotation to increase the distance that the table 5 travels. Each distance traveled is registered in positioner 1.

The origin return operation explained with reference to FIG. 7 will be described with reference to FIG. 2, in which the apparatus of the present invention is performed under the same conditions, that is, the position of the table 5 at the start of origin return is adjusted. Broken line 1
When the origin return operation is started in the direction of the arrow 16 from the position of the chifur 5 depicted in 2, the proximity sensor 6e for starting the origin search detects the dog 5a, and the encoder 6 starts the origin search. Upon detection of the signal from the photodiode 27a, the return-to-origin operation is completed, and the table 5 stops at the position drawn by the solid line 14. The moving distance of the table 5 at this time from the start to the end of returning to the origin is approximately 10 mm. Here, proximity sensors 6b, 6C, 6d for starting the origin search,
The reason for using four sensors 6e is that it is sufficient to have one proximity sensor within the range in which the table 5 moves once the motor 4 makes one revolution, and the distance G shown in FIG.
It is desirable that the distance between the origin signal sleeve 24a and the origin signal sleeve 24a be short.

Looking at the distance traveled by the table 5 from the start to the end of the return-to-origin operation in FIG. 2 of the present invention and FIG. 7 of the prior art, it can be seen that the conventional device moves about 7 Qmm, and the device of the present invention moves about 13 mm. I know it has moved. As mentioned above, in this case, the offset amount from the zero position to the home position of the encoder B after receiving the detection signal from the proximity sensor 6e, that is, the moving distance E for three rotations of the motor, is registered in the positioner 1. . In this way, table 5 after returning to the origin
Even if the position is as indicated by the solid line 14 in FIG. 2, if the position control is performed by taking the difference in offset amount from the command value of the positioner 10, the position can be accurately controlled based on the zero position of the origin.

[Embodiment 2] FIG. 3 shows a linear drive shaft position detection device according to a second embodiment of the present invention.

The configuration of the drive system is the same as that described in the first embodiment described using FIG. 1, but the different parts of the device will be described below with reference to FIG. 3.

The dog 5a shown in FIG. 1 is removed from the table 5, and the sensor fixing plate 17 is fixed to the right end 5b of the table 5.
This sensor fixing plate 17 includes proximity sensors 6a, 6b, 6.
c are fixed in a vertical line and perpendicularly to the top surface 5C of the chiffle 5.

A plate 18 is provided at a position facing the proximity sensors 6a, 6b, 6C and along the ball screw 7, which is a linear drive shaft, and this plate 18 has a metal plate shown in FIG. 4 that makes the proximity sensors 6a, 6b, 6C respond. A dog 19 made of 100% is fixed within the dashed line frame A. Three proximity sensors 6a, 6b, 6C
In order to obtain 3-bit data from one detection signal, it is necessary to combine and arrange the dogs 19. FIG. 4 shows the arrangement of the dogs 19. (2) One dog 19 is fixed in the W and X columns, two dogs in the U and Z columns, and three dogs in the Y column.

The role of the three pit data obtained from the dogs 19 in the U%V%w, x, y, and z columns will be explained below. The U and Z columns limit the operating range of the table 5, with the U column detecting the plus side limit and the Z column detecting the minus side limit. ■, W, X, and Y columns are for starting the origin search for encoder B, and are arranged at equal intervals between U and Z columns, and the dog is located within the distance that the table 5 advances by one rotation of the motor 4. There is one column with 19 numbers.

When the output signals from the proximity sensors 6a, 6b, 6c and the encoder 6 detected by the apparatus configured as described above and the encoder 6 are expressed on a time chart, the same is shown in FIG. The signal 8a on the time chart 8 is the signal when the proximity sensors 6a, 6b, 6c detect the dog 19 in the Z row, the signal 8b is the signal when the dog 19 in the Y row is detected, and the signal 8C is the same. The signal 8d is the signal when the dog 19 in the X row is detected, the signal 8d is the signal when the dog 19 in the W row is detected, the signal 8e is the signal when the dog 19 in the 7th row is detected, and the signal 8f is the signal when the dog 19 in the 7th row is detected. Similarly, the pulse signal on the time chart 9 is the detection signal of the photodiode 27b shown in FIG.
The origin pulse signals above 0 correspond to the detection signals of the photodiode 278, respectively.

In the following explanation, Z which is the stroke range of table 5
The installation distance from dog 19 in row to dog 19 in row U is 9
Qmm, lead pitch of ball screw 7 to 20m
It is assumed that the motor 4 operates in the range of 0 to 4.5 rotations, where m is the rotation speed.

Note that the position when the encoder 6 returns to the origin after the proximity sensors 6a, 6b, and 6C detect the seven rows of dogs 19 is the position where the motor has rotated three times from the zero origin position. Therefore,
It is necessary to register the distance traveled by the table 5 in the positioner 1 as an offset amount when the motor rotates three times at the position returned to the origin based on the signal detected by the seven rows of dogs 19.

Similarly, when the proximity sensor 6a, 6b, 6C detects the dog 19 in the W row, the motor rotates twice to the position where the proximity sensor 6a, 6b, 6C detects the dog 19 in the W row. 6cf) - It is necessary to register the distance traveled by the table 5 in the positioner 1 as an offset amount when the motor rotates once at the position returned to the origin based on the signal detected by the dog 19 in the X column.

If the origin return operation is performed in the same manner in the apparatus of the second embodiment from the position of the table 5 drawn by the broken line 12 shown in FIG. It goes without saying that similar results can be obtained if the amount of movement is lQmm.

In the above explanation, one row of dogs 19 is arranged within the movement range of the chifur 5 within the distance that the table 5 moves when the motor 4 makes one rotation. It does not matter how many proximity sensors are placed.

The dog 19 shown in FIG. 4 is used as is, and the table 5 is moved to the origin position zero by an origin return operation. From this origin position zero, the table 5 is moved in the positive direction of the arrow 11 shown in FIG. 3 by the proximity sensors 6a, 6b, 6C7! The dog 19 in the l'-X row is moved until it is detected. While detecting the dogs 19 in the X row, the encoder 3 uses the photodiode 2.
Pulse signals from 7b are counted and the distance that the table 5 has moved from the zero position is registered in the positioner 1 as an offset amount.

Similarly, the proximity sensors 6a, 6b, and 6C are
The moving distance of the table 5 until the dog 19 in the row is detected is determined by the pulse signal of the encoder 3. This is registered in the positioner 1 as an offset amount by means of counting. When the origin return operation is performed using the method described above, the encoder origin is searched only when the proximity sensors 6a, 6b, and 6c detect the dog 19 in the Y column, and when the proximity sensor 6a, 6b, and 6c detect the dog 19 in the X and WSV columns. The encoder ends its operation on the spot without searching for its origin. If position control is performed by calculating the difference between the next movement command value and the offset amount, there is no need to search for the origin of the encoder. In this method, as the number of rows of dogs 19 increases, the amount of movement and time of movement of the table 5 in the return-to-origin operation can be further reduced. Although this method was carried out using the apparatus shown in FIG. 3, it is also possible to use the apparatus shown in FIG. However, since the device shown in FIG. 1 requires only one bit of the signal from the proximity sensor, a large number of proximity sensors are required, so it is economically advantageous to use the device shown in FIG.

〔Effect of the invention〕

As explained above, by providing proximity sensors for absolute position detection at several locations within the motion range of the linear drive shaft, the return-to-origin operation is more precise than with conventional devices no matter where the table is within the motion range. It can be carried out in small quantities and in a short time, and position control can be performed from several origin return end positions.

The proximity sensor used in the absolute position detection device is a low-cost presence detection sensor that performs adequately, so it is cheaper and more efficient than detecting the motor angle using a battery backup method for absolute encoder or incremental encoder data. It is relatively easy to incorporate into the device shown in Figure 5.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of a linear drive shaft position detection device in the first embodiment of the present invention, FIG. 2 is a time chart showing the origin return operation in the first embodiment, and FIG. A perspective view showing the configuration of a linear drive shaft position detection device in a second embodiment of the present invention, FIG. 4 is a perspective view showing a combination of dogs in the second embodiment of the present invention, and FIG. FIG. 6 is a perspective view showing the configuration of a linear drive shaft position detection device, FIG. 6 is a perspective view showing an incremental encoder, and FIG. 7 is a time chart showing a conventional origin return operation. 3...Encoder, 5...Table, 5a, 19...Dog, 61L, 6b, 6C16d, 6e, 6f...
Proximity sensor, 7...Ball screw 5α dog

Claims (1)

[Claims] (1) A linear drive shaft that rotates due to the rotation of a motor, a table that is attached to the linear drive shaft to perform linear motion, a dog that is fixed to the table, and a device that detects the dog and moves in the axial direction of the linear drive shaft. A position detection device for a linear drive shaft, comprising a plurality of proximity sensors provided. (2) It has a linear drive shaft that rotates due to the rotation of a motor, a table that is attached to the linear drive shaft and performs linear motion, a plurality of proximity sensors that are installed perpendicular to the table, and a dog that detects the proximity sensors. A linear drive shaft position detection device characterized by: