Linear encoders and machine tools

Abstract

To suppress the occurrence of such a problem that substance causing contamination gets into a housing of a linear encoder.SOLUTION: A linear encoder 12 is provided, including a scale, a sensor unit 102b scanning the scale by a detection head thereby acquiring position information, a housing 301 housing the scale and the detection head, electropneumatic regulators 104a, 104b, and a control device 11. The housing 301 has air injection ports 118 provided at both end portions 114 in a scale length direction. The electropneumatic regulators 104a, 104b eject air to the air injection ports 118 of the housing. Regarding front pressure which is the pressure of the air to be ejected to the air injection port 118 of the housing located on a front side in a movement direction of the sensor unit 102b, and rear pressure which is the pressure of the air to be ejected into the air injection port 118 of the housing located behind the front side, the control device 11 controls the electro pneumatic regulators 104a, 104b in such a manner that the rear pressure becomes higher than the front pressure.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a linear encoder and a machine tool, and particularly to a configuration for suppressing the entry of substances that cause contamination into the housing of the linear encoder.

Background Art

[0002] A linear encoder mounted on a conventional machine tool will be described with reference to FIGS. 2 and 3. FIG. 2 is a schematic configuration diagram showing an example of a machine tool 100 on which a conventional linear encoder 102 is mounted. FIG. 3 is a cross-sectional view showing a cross-section of the linear encoder 102 perpendicular to the longitudinal direction of the scale 302 of the linear encoder 102. As shown in FIG. 2, the linear encoder 102 includes a scale unit 102a and a sensor unit 102b. The scale unit 102a is fixed to a bed (not shown). The sensor unit 102b is fixed to a table 110 as a control object, detects the position of the table 110 from a scale 302 (see FIG. 3) in the scale unit 102a, and outputs position information to a numerical control device 101.

[0003] The table 110 is fixed to a ball screw nut 109 and is in a non-rotating state. As the ball screw 108 (screw shaft) rotates, the ball screw nut 109 is movable in the axial direction of the ball screw 108. The ball screw 108 is pivotally supported at both ends by tack bearings (not shown) and is connected to the output shaft of a motor 106 via a coupling 107.

[0004] A rotary encoder 105 is provided on the other side of the output shaft of the motor 106. The rotary encoder 105 detects the rotational position of the motor 106 and outputs the position information to the numerical control device 101. The numerical control device 101 supplies a control current to the motor 106 and rotates the motor 106 to move the control object (table 110) to a desired position based on the position information from the rotary encoder 105 and the position information from the linear encoder 102.

[0005] Here, we will describe the installation environment of the linear encoder 102. In the case of machine tools, there are substances around the linear encoder 102 that can contaminate it, such as chips generated when cutting workpieces and cutting fluid used to improve cutting efficiency. Also, as can be seen from Figure 2, the linear encoder 102 is often placed relatively close to the ball screw 108, and lubricating oil used to smooth the rotation of the ball screw 108 may be splashed onto the linear encoder 102 as the ball screw 108 rotates. To prevent such substances from entering the housing 301 of the scale unit 102a (see Figure 3), it has been conventional practice to introduce compressed air from the end of the housing 301 in the longitudinal direction of the scale (the longitudinal direction of the scale 302, the direction that penetrates the plane of the paper in Figure 3). In the example in Figure 2, air is introduced from both ends 114 of the housing 301, but in some cases, it is introduced from only one end of the housing 301. The compressed air to be introduced is supplied from a compressor or the like in the factory where the machine tools are installed.

[0006] The compressed air supplied from the compressor is purified by the air filter unit 103. The air filter unit 103 typically consists of not only a regular air filter, but also a drain catch, mist separator, micro-mist separator, super-mist separator, etc., and is designed to purify the air in multiple stages to generate clean air. The compressed clean air thus purified is set to a predetermined air pressure by the pressure gauge-equipped regulator 204 and supplied to the housing 301 of the scale unit 102a.

[0007] The higher the air pressure of the supplied compressed clean air, the better it protects the scale unit 102a from contaminating substances. However, this also increases the air consumption of the factory compressor, leading to increased power consumption and thus inefficiency. In addition, the increased airflow rate causes the air filter unit 103 to become dirty more quickly, shortening the interval between maintenance such as filter replacement. For these reasons, the air pressure setting is selected while considering the balance between the ability to protect against contaminating substances and the airflow rate. Nevertheless, contamination inside the housing 301 of the scale unit 102a was a problem for the linear encoder 102.

[0008] As shown in Figure 3, the scale unit 102a comprises a housing 301 and a scale 302 located inside the housing 301. The sensor unit 102b comprises a detection head 312 located inside the housing 301, a scanning head 305 located outside the housing 301, and a connecting part 308 that connects the scanning head 305 and the detection head 312.

[0009] The scale 302 is made of a glass plate with a grid-like chrome light-shielding film laid on it, and is fixed to the housing 301 (scale cover) with a rubber band 303 and an adhesive (not shown). The housing 301 has an opening 310 along the longitudinal direction of the scale, which is configured to allow the connecting portion 308 of the sensor unit 102b to move in the longitudinal direction of the scale. The opening 310 of the housing 301 is sealed by two dustproof seals 304a and 304b, thereby preventing substances from entering the housing 301 from the outside.

[0010] The detection head 312 of the sensor unit 102b includes a light-emitting unit 306 consisting of an LED or the like, a light-receiving unit 307 consisting of a photodiode or the like, and a holding part 309 that holds the light-emitting unit 306 and the light-receiving unit 307. The scanning head 305 has a processing circuit board (not shown) inside. The processing circuit board of the scanning head 305 and the light-emitting unit 306 and the light-receiving unit 307 of the detection head 312 are connected by a cable through a tunnel-shaped hole (not shown) provided in the connecting part 308 of the sensor unit 102b, and power is supplied to the LED and electrical signals converted by the photodiode are transmitted and received.

[0011] When the sensor unit 102b moves in the longitudinal direction of the scale relative to the scale unit 102a, the connecting portion 308 of the sensor unit 102b moves while contacting and pushing aside the dust seals 304a and 304b.

[0012] Dust seals 304a and 304b are generally made of rubber, ranging from nitrile rubber and urethane to fluorinated rubber, which is selected for its oil resistance. However, there are many types of cutting fluids used in machine tools, and various additives are used, making it difficult to find a rubber material that is completely unaffected. In addition, the oil adhering to the dust seals 304a and 304b can deteriorate over time, increasing in viscosity or containing other foreign matter such as iron filings from chips, which can cause dragging at the contact point with the connecting part 308 of the sensor unit 102b, damaging the contact surface. In this way, problems such as deterioration, deformation, and alteration can occur in the dust seals 304a and 304b, sometimes creating a gap between the dust seals 304a and 304b and the connecting part 308. In conventional technology, as mentioned above, compressed air is introduced into the housing 301, so it is believed that even if there is a small gap, the air pressure can prevent substances from entering the housing 301 from the outside.

[0013] Referring again to Figure 3, in the internal cross-section of the housing 301, the detection head 312 of the sensor unit 102b occupies almost the entire area, leaving only a small gap. In this state, when the scale unit 102a and the sensor unit 102b move relative to each other, a situation occurs as if a piston were operating inside a cylinder. In this case, the sensor unit 102b corresponds to the piston, and the air pressure inside the housing 301 on the side it is moving toward becomes higher, while conversely, the air pressure inside the housing 301 on the side it is moving away from becomes lower. The air pressure inside the housing 301 on the side with higher pressure is fine, but the air pressure inside the housing 301 on the side with lower pressure becomes lower. If the lower air pressure cancels out with the supplied air pressure, resulting in a negative pressure state, it can draw substances into the housing 301 from the outside. If there is a gap between each of the two dustproof seals 304a and 304b and the connecting part 308, the supplied air pressure will decrease, making it easier for negative pressure to be generated.

[0014] Furthermore, in recent machine tools and the like, the adoption of linear motor drives has increased the relative movement speed between the scale unit 102a and the sensor unit 102b, the so-called feed rate, which is also contributing to the generation of negative pressure. It has been suggested that increasing the gap between the two components in the internal cross-section of the housing 301 where the detection head 312 is located would reduce the generation of negative pressure, but this would require making the housing 301 larger (thicker), thus presenting a difficult choice.

[0015] Patent Document 1 discloses a length measuring device that measures the distance traveled by the relative movement of a main scale and a detection head installed inside a housing, and includes a configuration in which a ventilation pipe is provided to allow air to flow from the front part to the rear part in the direction of movement of the detection head, thereby suppressing a negative pressure state in the rear part in the direction of movement. [Prior art documents] [Patent Documents]

[0016] [Patent Document 1] Japanese Utility Model Publication No. 4-11405 [Overview of the project] [Problems that the invention aims to solve]

[0017] In linear encoders, even when the opening is sealed with a dustproof seal and compressed clean air is introduced into the housing, contaminants can enter the housing, contaminate the scale surface, and cause detection failures. The cause is as follows:

[0018] Cutting fluids and lubricants adhere to the dust seal, and as they absorb other foreign matter such as metal shavings, the viscosity of the oil increases. When the sensor unit is scanned in this increased viscosity state, friction at the contact surface between the dust seal and the sensor unit increases, gradually damaging the lip of the dust seal and reducing its sealing performance. However, even in this state, the air pressure of the clean air can prevent some degree of material from entering the housing. Nevertheless, the relative movement between the scale unit and the sensor unit creates a situation similar to a piston operating in a cylinder, resulting in negative pressure inside the housing. When negative pressure occurs, oil mist and dust floating in the surrounding atmosphere of the linear encoder are drawn in, contaminating the scale surface.

[0019] To prevent this, if the air pressure of the clean air is steadily increased, the air consumption of the factory's air compressor will increase, making it inefficient. Furthermore, the increased airflow rate will accelerate the fouling of the air filters that generate the clean air, necessitating frequent filter replacement and other maintenance. Therefore, a configuration that can effectively suppress the entry of contaminants into the linear encoder housing is desired.

[0020] The objective of this invention is to prevent contaminating substances from entering the housing of a linear encoder. [Means for solving the problem]

[0021] The linear encoder according to the present invention includes a scale, a sensor unit having a detection head positioned opposite the scale and scanning the scale with the detection head to obtain position information, and a housing housing the scale and the detection head, wherein the sensor unit has a scanning head positioned outside the housing and a connecting portion connecting the scanning head and the detection head, and the housing has an opening extending in the longitudinal direction of the scale configured to allow the connecting portion of the sensor unit to move, a sealing member that closes the opening, and air inlets provided at both ends in the longitudinal direction of the scale, the linear encoder comprising an electro-pneumatic regulator that discharges pressure-adjusted air to air inlets at both ends of the housing, and a control device that controls the electro-pneumatic regulator so that the rear pressure is higher than the front pressure with respect to the front pressure, which is the pressure of the air discharged to the air inlet of the housing located on the front side in the direction of movement of the sensor unit, and the rear pressure, which is the pressure of the air discharged to the air inlet of the housing located on the rear side.

[0022] In the linear encoder according to the present invention, the control device may control the electro-pneumatic regulator such that the rear pressure when the sensor unit moves at a second speed faster than the first speed is higher than the rear pressure when the sensor unit moves at a first speed.

[0023] Furthermore, the machine tool according to the present invention includes the linear encoder, and the control device of the linear encoder is a numerical control device that controls the position of the object to which the sensor unit is connected. [Effects of the Invention]

[0024] According to the present invention, even if the sensor unit (detection head) moves relative to the scale, it is possible to suppress the generation of negative pressure inside the housing, so that the entry of contaminants into the housing can be suppressed. Suppressing the entry of contaminants into the linear encoder can lead to a reduction in the occurrence of problems such as detection failures and alarms related to the linear encoder, and thus it is also possible to reduce maintenance costs and replacement costs.

Brief Description of the Drawings

[0025] [Figure 1] FIG. 8 is a schematic configuration diagram showing an example of a machine tool including a linear encoder according to an embodiment of the present invention. [Figure 2] FIG. 11 is a schematic configuration diagram showing an example of a machine tool including a conventional linear encoder. [Figure 3] FIG. 14 is a cross-sectional view showing a cross-section of a linear encoder common to an embodiment of the present invention and the prior art.

Embodiments for Carrying Out the Invention

[0026] Hereinafter, embodiments of the present invention will be described based on the drawings. Note that the present invention is not limited to the embodiments described herein. The same reference numerals are given to the same elements in all the drawings, and redundant descriptions are omitted.

[0027] <First Embodiment> FIG. 1 is a schematic configuration diagram showing an example of a machine tool 10 including a linear encoder 12 according to an embodiment of the present invention. As shown in FIG. 1, in the present embodiment, in the air supply path introduced into the housing 301 of the linear encoder 12, instead of the pressure gauge-equipped regulator 204 (see FIG. 2), electro-pneumatic regulators 104a and 104b are arranged. Also, an electric wire is arranged between the numerical control device 11 and the electro-pneumatic regulators 104a and 104b so that control signals PSR and PSL can be transmitted from the numerical control device 11 to the electro-pneumatic regulators 104a and 104. Other configurations in FIG. 1 are the same as those in FIG. 2.

[0028] The machine tool 10 is an NC machine tool equipped with a numerical control device 11. The machine tool 10 comprises the numerical control device 11, a table 110 as the object to be controlled, and a linear encoder 12 connected to the table 110. The basic configuration of the machine tool 10 and the linear encoder 12 is the same as that of the machine tool 100 and the linear encoder 102 described using Figures 2 and 3.

[0029] As shown in Figure 1, the linear encoder 12 comprises a scale unit 102a and a sensor unit 102b. The scale unit 102a includes a scale 302 (see Figure 3) and a housing 301. The sensor unit 102b includes a detection head 312 (see Figure 3) positioned opposite the scale 302, a scanning head 305 positioned outside the housing 301, and a connecting portion 308 connecting the scanning head 305 and the detection head 312.

[0030] The scale 302 is, for example, a glass plate with a grid-like light-shielding film laid on it. The detection head 312 includes a light-emitting unit 306 and a light-receiving unit 307 (optical sensor element) positioned opposite each other with the scale 302 in between. As the ball screw nut 109 moves, the sensor unit 102b scans the scale 302 with the detection head 312, acquires position information with the light-receiving unit 307 and a processing circuit board (not shown), and transmits the position information to the numerical control device 11. Thus, the linear encoder 12 is a transmissive encoder.

[0031] The linear encoder 12 may also be a reflective encoder. That is, the scale may be, for example, a steel plate with a grid-like reflective light-shielding film laid on it, and the detection head may have both a light-emitting unit and a light-receiving unit (optical sensor element) arranged on one side of the scale.

[0032] The housing 301 houses the scale 302 and the detection head 312. The housing 301 includes an opening 310 extending in the longitudinal direction of the scale, configured to allow the connecting portion 308 of the sensor unit 102b to move, dust seals 304a and 304b (sealing members) that close the opening 310, and air inlets 118 provided at both ends 114 (see Figure 1) in the longitudinal direction of the scale. The ends 114 of the housing 301 in the longitudinal direction of the scale are closed by end plates, and the air inlets 118 are provided on the end plates.

[0033] The linear encoder 12 includes electro-pneumatic regulators 104a and 104b. The electro-pneumatic regulators 104a and 104b draw in compressed air (compressed air supplied from a compressor) supplied via the air filter unit 103, adjust the pressure of the compressed air, and discharge it to the air inlet 118 of the housing 301. Specifically, the electro-pneumatic regulator 104a discharges air to the air inlet 118 at the right end 114 of the housing 301, and the electro-pneumatic regulator 104b discharges air to the air inlet 118 at the left end 114 of the housing 301. In this embodiment, two electro-pneumatic regulators 104a and 104b are used, but a single electro-pneumatic regulator integrating these two may also be used.

[0034] The numerical control device 11 controls the pressure of the discharged air from the electro-pneumatic regulator 104a by transmitting a control signal PSR, and controls the pressure of the discharged air from the electro-pneumatic regulator 104b by transmitting a control signal PSL. In this embodiment, since a linear encoder 12 is used in the machine tool 10, the numerical control device 11 is used as the control device for the electro-pneumatic regulators 104a and 104b. However, depending on the device or system in which the linear encoder 12 is used, other control devices may be used to control the electro-pneumatic regulators 104a and 104b. The control device includes a processor having a CPU and a memory device. The processor operates according to the program and control data stored in the memory device and controls the electro-pneumatic regulators 104a and 104b.

[0035] The numerical control device 11 controls the electro-pneumatic regulators 104a and 104b so that the forward pressure, which is the pressure of the air discharged to the air inlet 118 of the housing 301 located on the front side in the direction of movement of the sensor unit 102b (detection head 312), and the rear pressure, which is the pressure of the air discharged to the air inlet 118 of the housing 301 located on the rear side, are higher than the forward pressure. This will be explained in detail below.

[0036] The numerical control device 11 outputs a control current to the motor 106 to eliminate the difference between the detected position fed back from the sensor unit 102b and the commanded position, based on the input driving program and the commanded position from the operator, thereby rotating the rotation axis of the motor 106. As the rotation axis of the motor 106 rotates, the ball screw 108 connected via the coupling 107 rotates, and the ball screw nut 109, whose rotation is constrained, moves axially. This allows the table 110, which is connected to the ball screw nut 109, to be moved to the desired position. Therefore, before moving the table 110 to the desired position, the numerical control device 11 can determine from the difference between the commanded position and the detected position whether the sensor unit 102b will move to the left or right relative to the scale unit 102a.

[0037] In Figure 1, when the command position for moving the table 110 to the left is reached, the sensor unit 102b also moves to the left relative to the scale unit 102a. When this state is reached, the numerical control device 11 outputs a control signal PSR to the electro-pneumatic regulator 104a, commanding it to increase the air pressure value (air pressure value) introduced into the right air inlet 118 of the scale unit 102a (housing 301). Conversely, it outputs a control signal PSL to the electro-pneumatic regulator 104b, commanding it to decrease the air pressure value introduced into the left air inlet 118 of the scale unit 102a (housing 301). Then, when the table 110 reaches the command position, the numerical control device 11 outputs control signals PSR and PSL so that the air pressure values ​​of each electro-pneumatic regulator 104a and 104b are balanced.

[0038] On the other hand, in Figure 1, when the command position for moving the table 110 to the right is reached, the control signal PSR to the electro-pneumatic regulator 104a outputs a command to decrease the pressure value of the air introduced into the right air inlet 118 of the scale unit 102a, and the control signal PSL to the electro-pneumatic regulator 104b outputs a command to increase the pressure value of the air introduced into the left air inlet 118 of the scale unit 102a.

[0039] Here, we will explain an example of air pressure values. Although it will vary depending on the structure and size of the linear encoder 12, air is introduced into each of the two air inlets 118 of the housing 301 at an air pressure value of, for example, about 0.03 MPa. Therefore, for example, when the sensor unit 102b moves, it is good to output control signals PSR and PSL such that the side on which you want to increase the air pressure value (the rear side in the direction of movement) is 0.05 MPa and the side on which you want to decrease it (the front side in the direction of movement) is 0.01 MPa. Also, the side on which the air pressure value is to be relatively decreased does not necessarily have to be lower than the balanced 0.03 MPa when the unit is not moving. That is, even if it remains at 0.03 MPa, it is sufficient if the side on which the air pressure value is to be increased (the rear side in the direction of movement) exceeds that value. In other words, the air pressure value introduced by the sensor unit 102b into the inner chamber of the scale unit 102a on the moving side (the front side in the direction of movement) should be lower than the air pressure value in the inner chamber on the opposite side (the rear side in the direction of movement).

[0040] In other words, it is ideal to command an air pressure value such that negative pressure does not occur in the inner chamber of the scale unit 102a (housing 301) on the side where the sensor unit 102b is moving away (the rear side in the direction of movement). If the conditions under which negative pressure occurs are measured in advance through experiments, it will be possible to command an even more reasonable air pressure value. Note that the air pressure value shown here is just an example, and the air pressure value can be changed as appropriate.

[0041] According to the embodiment described above, when the sensor unit 102b (detection head 312) moves, it is possible to suppress the generation of negative pressure in the inner chamber on the rear side in the direction of detection head movement of the housing 301, thereby suppressing the entry of contaminants into the housing 301 through the opening 310. Suppressing the entry of contaminants into the linear encoder reduces the occurrence of failures and alarms related to detection errors of the linear encoder, which in turn reduces maintenance and replacement costs.

[0042] Furthermore, the numerical control device 11 (control device) may control the electro-pneumatic regulators 104a and 104b so that the total pressure value of the air supplied to the two air inlets 118 when the sensor unit 102b is moving (moving pressure value) does not increase compared to the total pressure value of the air supplied to the two air inlets 118 when the sensor unit 102b is not moving (stopped). In other words, it may suppress increasing the airflow rate when the sensor unit 102b is moving. This can suppress the air consumption of the compressor that supplies compressed air and suppress the progression of filter fouling in the air filter unit 103.

[0043] <Second Embodiment> Next, a linear encoder of the second embodiment will be described. The linear encoder of the second embodiment has the same basic configuration as the linear encoder of the embodiment described above (the first embodiment), but differs in that it changes the pressure of the air supplied to the housing 301 according to the moving speed of the sensor unit 102b.

[0044] Specifically, in the second embodiment, the numerical control device 11 controls the electro-pneumatic regulators 104a and 104b such that the rear pressure when the sensor unit 102b moves at a fast speed (second speed, second speed > first speed) is higher than the rear pressure (referred to as rear pressure) when the sensor unit 102b moves at a slow speed (first speed) in the rear inner chamber of the housing 301 in the direction of detection head movement.

[0045] For example, the numerical control device 11 increases the air pressure value in the rear inner chamber of the housing 301 in the direction of detection head movement (a value higher than the air pressure value when the sensor unit 102b is stopped) in proportion to the movement speed of the sensor unit 102b. As an example, the numerical control device 11 outputs a command to the electro-pneumatic regulators 104a and 104b to increase the air pressure value in the rear inner chamber of the housing 301 in the direction of detection head movement at a rate of, for example, 0.01 MPa per 1 m / min for the feed speed that moves the table 110. In this second embodiment as well, it is possible to effectively suppress the entry of contaminants into the housing 301.

[0046] Although embodiments of the present invention have been described above, the present invention is not limited to these forms. In Figure 1, the feed axis was described as a single-axis configuration, but it may also be a three-axis configuration (X-axis, Y-axis, Z-axis), etc. Also, although the feed mechanism was driven by a ball screw 108, a linear motor drive system may also be used. A linear motor drive system allows for higher speeds and greater acceleration / deceleration, making it easier for a negative pressure state to occur inside the housing 301 as the sensor unit 102b moves, thus making it easier to achieve the effects of the above-described embodiments.

[0047] Even if the above-mentioned components are slightly modified, a control device that controls the pressure of the air introduced to the linear encoder 102, taking into account the decrease in air pressure inside the housing due to the movement of the sensor unit 102b, the state of the surrounding environment, the state of the target system, etc., can be said to be within the scope of the present invention. [Explanation of Symbols]

[0048] 10,100 Machine tool, 11,101 Numerical control device (control device), 12,102 Linear encoder, 102a Scale unit, 102b Sensor unit, 103 Air filter unit, 104a,104b Electro-pneumatic regulator, 105 Rotary encoder, 106 Motor, 107 Coupling, 108 Ball screw, 109 Ball screw nut, 110 Table (object to be controlled), 114 End, 118 Air inlet, 204 Regulator with pressure gauge, 301 Housing (scale cover), 302 Scale, 303 Rubber cord, 304a,304b Dustproof seal (sealing member), 305 Scanning head, 306 Light-emitting unit, 307 Light-receiving unit (optical sensor element), 308 Connecting part, 309 Holding part, 310 Opening, 312 Detection head.

Claims

1. The system includes a scale, a sensor unit having a detection head positioned opposite the scale and scanning the scale with the detection head to obtain positional information, and a housing that houses the scale and the detection head. The sensor unit has a scanning head located outside the housing and a connecting portion that connects the scanning head and the detection head. The housing is a linear encoder having an opening extending in the longitudinal direction of the scale, configured to allow the connecting portion of the sensor unit to move, a sealing member that closes the opening, and air inlets provided at both ends in the longitudinal direction of the scale, An electro-pneumatic regulator that discharges pressure-regulated air to air inlets at both ends of the housing, The device comprises a control device that controls the electro-pneumatic regulator so that the forward pressure is higher than the forward pressure, with respect to the forward pressure, which is the pressure of the air discharged to the air inlet of the housing located on the front side in the direction of movement of the sensor unit, and the rear pressure, which is the pressure of the air discharged to the air inlet of the housing located on the rear side. A linear encoder characterized by the following features.

2. In the linear encoder according to claim 1, The control device is The electro-pneumatic regulator is controlled such that the rear pressure when the sensor unit moves at a second speed faster than the first speed is higher than the rear pressure when the sensor unit moves at a first speed. A linear encoder characterized by the following features.

3. Includes the linear encoder according to claim 1 or 2, The control device of the linear encoder is a numerical control device that controls the position of the object to which the sensor unit is connected. A machine tool characterized by the following features.

Images