JPH10141990A - Linear encoder of direct acting-axis integrated type - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear encoder of direct acting-axis integrated type wherein, even when a movable body mounted on a sensor rocks (yawing and/or pitching) to move against an encoder chart, reading of a encoder chart information with the sensor is performed stably. SOLUTION: A direct acting axis 1 forming an encoder chart 3, an axis guide unit 2 which reciprocally moves on the direct acting axis 1 along the axis 1, and a sensor 4 which, provided at the axis guide unit 2, reads the information for the encoder chart 3, are provided. The sensor 4 is provided at almost center of yawing action and/or that of pitching action to the encoder chart 3 of the unit 2 which occur when the axis guide unit 2 moves on the direct acting axis 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear encoder which can be used for detecting the position and speed of a moving body that moves linearly.

[0002]

2. Description of the Related Art In a field where it is necessary to convey or move equipment, articles, etc. linearly along a linear motion axis, position detection, speed control, etc. of a moving body are required. There are many. O for copiers, image scanners, printers, etc.
A equipment, XY table, FA equipment such as article transport device,
There is a demand in a wide field such as optical equipment such as a camera.

Conventionally, linear encoders have been widely used to meet such demands. Linear encoders are usually linearly arranged encoder charts,
A sensor that moves along the encoder chart and reads the encoder chart information.

The sensor is supported directly or indirectly via another member on a movable body moving on a linear motion axis. For an encoder chart, the sensor is mounted on the linear motion axis separately from the linear motion axis of the movable body. They may be arranged in parallel, or may be formed directly on the linear motion shaft of such a movable body.

[0005]

However, in any case, for example, as shown in FIGS.
When the movable body 8 is linearly supported by the movable body 8 that moves on the linear motion shaft 7, when the movable body 8 is under a biased load, the movable body 8 is slightly yawed with respect to the encoder chart 92. In many cases, the sensor 91 on the movable body 8 facing the encoder chart 92 swings (swings), and sometimes moves with pitching (swinging). The position of the encoder chart 92 relative to the encoder chart 92 becomes unstable, and the gap between the sensor 91 and the encoder chart 92 fluctuates.
Inconveniences such as the detection signal from the second becoming unstable and the difficulty of reading the encoder chart information occur.
As a result, the encoder may not be able to control the operation of the mobile object whose position and speed are controlled, or the mobile object may run away and be damaged. In addition, the forward direction (for example, the direction indicated by the arrow α in the figure) and the backward operation (for example, the direction indicated by the arrow β in the figure) of the sensor 91 are often reversed in the direction of the swing. If the positional relationship is set so as to be convenient for the operation described above, the inconvenience occurs that the encoder chart 92 cannot be read well during the other operation.

Accordingly, the present invention provides a linear motion shaft on which an encoder chart is formed, a movable body reciprocally movable on the linear motion axis along the axis, and provided on the movable body to read the encoder chart information. A linear encoder integrated linear encoder with a sensor. Even if the movable body moves (yawings and / or pitches) with respect to the encoder chart, the encoder can read the encoder chart information. It is an object to provide a linear encoder integrated linear encoder that can be performed stably.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides the following linear encoder integrated with a linear motion shaft. A linear motion shaft on which an encoder chart is formed, a shaft guide unit capable of reciprocating along the linear motion shaft along the axis, and a sensor provided on the shaft guide unit for reading the encoder chart information, The linear encoder integrated with a linear shaft, wherein the sensor is provided so as to correspond to substantially the center of the yawing operation with respect to the encoder chart of the unit which is generated when the shaft guide unit moves on the linear motion shaft. A linear motion shaft on which an encoder chart is formed, a shaft guide unit capable of reciprocating along the linear motion shaft along the axis, and a sensor provided on the shaft guide unit for reading the encoder chart information, A linear encoder integrated with a linear shaft, wherein the sensor is provided substantially corresponding to a center of a pitching operation of the unit with respect to the encoder chart, which is generated when the shaft guide unit moves on the linear motion shaft.

According to the linear encoder of the present invention, the sensor for detecting the encoder chart signal is located substantially at the center of yawing of the shaft guide unit (movable body).
Even when yawing occurs, the gap and the positional relationship between the sensor and the encoder chart are substantially constant and do not change, and even when the yawing amount is large, the sensor does not deviate from the encoder chart. Can be read stably. Further, it is possible to read the encoder chart information stably in both the reciprocating directions with respect to the linear motion shaft of the shaft guide unit.

The center of the yawing is generally a point at which the loads applied to both ends of the shaft guide unit are balanced (for example,
When a load of m1 is applied to the front end shaft guide member and a load of m2 is applied to the rear end shaft guide member, it is considered that the interval between both end shaft guide members is divided into m2: m1). Since the loads applied to the members are almost the same, it can be often assumed that the yawing center is located at the center between the shaft guide members.

According to the linear encoder of the present invention, the sensor for detecting the encoder chart signal is located substantially at the center of the pitch of the shaft guide unit (movable body). The gap and the positional relationship are substantially constant and do not change. As a result, the encoder chart information can be read stably.

[0011] The pitching center is also considered to be generally located at a portion where the loads applied to both ends of the shaft guide unit are balanced, for example, when the loads applied to the shaft guide members at both ends are substantially the same, the center between the shaft guide members. The shaft guide unit in the linear encoder and the linear encoder may be externally driven by a drive wire or the like, but the linear motion shaft includes a field magnet and also serves as a stator of the linear motor, and the shaft guide unit is used. May include an armature coil facing the field magnet, and may also serve as a mover of the linear motor. Accordingly, the linear guide direction of the shaft guide unit and the driving force generation direction coincide with each other, so that the shaft guide unit can move more stably on the linear drive shaft, and the device is small and simple.

The encoder of the present invention may be either an optical encoder or a magnetic encoder. In the case of an optical encoder, it is conceivable to employ a reflection type encoder, although not limited thereto. At this time, the encoder chart may have a low light reflectance portion and a high light reflectance portion alternately arranged at predetermined intervals. Further, the sensor can be exemplified by a sensor including a light emitting element and a light receiving element.

In the case of a magnetic encoder, the encoder chart may be formed by alternately arranging N poles and S poles at predetermined intervals. In this case, the sensor may be a magnetic sensor capable of detecting magnetism.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a schematic plan view of an example of a linear encoder integrated with a linear motion shaft according to the present invention, and FIG. 1B is a cross-sectional view of the linear encoder of FIG. . This linear encoder integrated linear encoder
A linear motion shaft 1 having a circular cross section, an encoder chart 3 provided on the surface of the linear motion shaft 1, a cylindrical shaft guide unit 2 fitted externally to the linear motion shaft 1, and an encoder chart 3 on the inner surface of the shaft guide unit 2; And the shaft guide unit 2
And a sensor 4 provided substantially at the center C1 of the yawing operation with respect to the encoder chart 3 of FIG.

The chart 3 is an optical reflection type in which low light reflectance portions 31 and high light reflectance portions 32 are alternately arranged at predetermined intervals. On the other hand, the sensor 4 has a light emitting element and a light receiving element so as to face the chart 3 and receives light emitted from the light emitting element and reflected by the low light reflectance portion 31 or the high light reflectance portion 32 of the chart 3. It is detected by the element.

The shaft guide unit 2 has shaft guide members 2 at front and rear ends.
1 and 22, which are fitted to the linear motion shaft 1 so that the whole unit 2 can reciprocate along the linear motion shaft 1. Further, this linear encoder has a carriage 5 connected to one side surface of the shaft guide unit 2, and a roller 61 attached to the other end of the carriage 5 not connected to the shaft guide unit 2 so as to be able to move on a rail 62.
Is provided. Further, a driving force transmission wire 50 is connected to a side surface of the shaft guide unit 2 on a side not connected to the carriage 5, so that a driving force can be supplied to the unit 2. When this linear encoder is used, for example, for driving a document image scanning optical system of an image reading apparatus, a mirror, a lamp, and the like are mounted on the carriage 5.

In the present embodiment, the encoder is of an optical type and of a reflection type, but may be of a magnetic type. In this case, the chart 3 may be formed by alternately arranging N poles and S poles at predetermined intervals, and the sensor 4 may be a magnetic sensor, for example, a sensor using an MR element or a Hall element. According to the linear encoder integrated linear encoder, the sensor 4 for detecting the signal of the encoder chart 3
Is substantially at the yawing center C1 of the shaft guide unit 2, the gap and the positional relationship between the sensor 4 and the encoder chart 3 remain constant even when yawing occurs.
In addition, even when the yawing amount is large, the sensor 4 does not deviate from the position corresponding to the encoder chart 3, so that the encoder chart information can be read stably, and the operation of the bearing unit 2 and, consequently, the carriage 5 can be stabilized. Control. Further, the shaft guide unit 2
The encoder chart information can be read stably in both the reciprocating directions with respect to the linear motion shaft 1.

Although not shown, in the linear encoder shown in FIG. 1, a sensor provided at a position where the sensor 4 can be regarded as the pitching center of the shaft guide unit 2 may be considered. According to the encoder, the sensor 4 that detects the signal of the encoder chart 3
Is substantially at the pitching center of the shaft guide unit 2, the gap and the positional relationship between the sensor 4 and the encoder chart 3 remain constant and do not change even when pitching occurs. As a result, the encoder chart information can be read stably. Can be. Further, it is possible to read the encoder chart information stably in both the reciprocating directions of the shaft guide unit 2 with respect to the translation shaft 1.

FIG. 2A is a schematic plan view of another example of the linear encoder integrated linear encoder according to the present invention, and FIG. 2B is a plan view of the linear encoder Y of FIG. 2A. It is sectional drawing which follows the -Y line. This linear encoder employs a linear motion shaft 1 ′ also serving as a linear motor stator having a field magnet 11 instead of the linear motion shaft 1 in the linear encoder shown in FIG. Moving shaft 1
'And the armature coil 2 facing the field magnet 11
0 is provided. An encoder chart 3 is provided on the linear motion shaft 1 '. When the armature coil 20 is energized, a thrust is generated in the bearing unit 2 due to the interaction with the field magnet 11, whereby the shaft guide unit 2 and thus the sensor 4 mounted thereon reciprocate along the encoder chart 3. it can. In this encoder, the sensor 4 is also provided substantially at the yawing center C2 of the shaft guide unit (movable element) 2 including the coil 20.

According to the linear encoder integrated linear encoder, since the moving direction of the shaft guide unit 2 in the linear shaft 1 'and the driving force generation direction coincide with each other, a stable driving force can be obtained and the driving force can be obtained. Since the transmission mechanism can be omitted,
The device is small and simple. Further, since the sensor 4 for detecting the signal of the encoder chart 3 is substantially at the yawing center C2 of the shaft guide unit 2, even when yawing occurs, the gap and the positional relationship between the sensor 4 and the encoder chart 3 are fixed and do not change. Also, even when the yawing amount is large, the sensor 4 does not deviate from the position corresponding to the encoder chart 3, so that the encoder chart information can be read stably and the operation of the carriage 5 can be controlled stably. .

In the linear encoder shown in FIG.
A sensor provided at a position where the sensor 4 can be regarded as the pitching center of the shaft guide unit 2 is also conceivable. In this case, substantially the same effect as described above can be obtained.

[0022]

According to the present invention, a linear motion shaft on which an encoder chart is formed, a movable body reciprocally movable on the linear motion axis along the axis, and the encoder chart information provided on the movable body. The linear encoder is a linear encoder having a sensor for reading the encoder chart, and the encoder detects the chart information of the encoder even if the movable body swings (yaws and / or pitches) with respect to the encoder chart. It is possible to provide a linear encoder integrated linear encoder that can perform reading stably.

[Brief description of the drawings]

FIG. 1 (A) is a schematic plan view of an example of a linear encoder integrated with a linear motion shaft according to the present invention, and FIG. 1 (B) is along the line XX of the linear encoder of FIG. 1 (A). It is sectional drawing.

2A is a schematic plan view of another example of the linear encoder integrated linear encoder according to the present invention, and FIG. 2B is a sectional view taken along line Y-Y of the linear encoder of FIG. It is sectional drawing which follows.

FIG. 3 is a diagram illustrating a yaw state of a mover and a sensor mounted on the mover in a conventional linear encoder.

FIG. 4 is a diagram showing another example of a yaw state of a mover and a sensor in a conventional linear encoder.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 linear motion shaft 1 ′ linear motion shaft also serving as linear motor stator 2 axis guide unit 21, 22 axis guide member 11 field magnet 20 armature coil 3 encoder chart 31 low light reflectance portion 32 high light reflectance portion 4 sensor 5 Carriage 50 Driving force transmission wire 61 Roller 62 Rail C1, C2 Center of yawing

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G01P 3/50 G01P 3/50 B 3/54 3/54 G02B 7/08 G02B 7/08 C

Claims (4)

[Claims] A linear axis forming an encoder chart;
An axis guide unit that can reciprocate along the linear motion axis along the axis; and a sensor that is provided on the axis guide unit and that reads the encoder chart information. A linear encoder integrated with a linear motion shaft, which is provided so as to correspond substantially to the center of the yawing operation of the unit with respect to the encoder chart which occurs when the unit moves on a shaft. 2. The linear motor according to claim 1, wherein said linear drive shaft comprises a field magnet and also serves as a stator of a linear motor, and said shaft guide unit comprises an armature coil facing said field magnet, The linear encoder integrated linear encoder according to claim 1, which also serves as a linear encoder. 3. A linear motion shaft forming an encoder chart;
An axis guide unit that can reciprocate along the linear motion axis along the axis; and a sensor that is provided on the axis guide unit and that reads the encoder chart information. A linear encoder integrated with a linear motion shaft, which is provided substantially corresponding to a center of a pitching operation of the unit with respect to the encoder chart which occurs when the unit moves on a shaft. 4. The linear motor has a field magnet and also serves as a stator of a linear motor, and the shaft guide unit has an armature coil facing the field magnet, and a linear motor mover. The linear encoder integrated with a linear motion shaft according to claim 3, which also serves as a linear encoder.