Mechanical system

Abstract

To suppress the occurrence of vibration phenomena caused by electromagnetic noise when a fixed part and a movable part of a machine are in a non-contact state during axial operation, in a mechanical system including an optical linear encoder having a non-contact structure between a scale and a slider, and a machine.SOLUTION: The mechanical system includes: a linear encoder including a scale 1 and a slider 2; a machine to which the linear encoder is mounted, the machine including a fixed part 21 and a movable part 22; a conduction part 31 and a contact part 32, each electrically connected to one of the slider 2 and the scale 1; and a contact element 27 mounted to the conduction part 31. The scale 1 and the slider 2 are respectively mounted to one of the fixed part 21 and the movable part 22. The contact element 27 comes into contact with the contact part 32 so that the scale 1 and the slider 2 become electrically equipotential when either an operating speed of the movable part 22 or a contact resistance between the movable part 22 and the fixed part 21 exceeds a threshold.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a mechanical system including a linear encoder and a machine. [Background technology]

[0002] When controlling the position of a feed axis of an NC machine tool, etc., highly accurate positioning is possible by performing full closed loop control using the position detected by a linear encoder attached to a table or saddle in addition to the position detected by a rotary encoder built into the servo motor. This is because high accuracy position control is not possible using only the position detected by a rotary encoder due to torsion phenomena in the ball screw, etc. Linear encoders are broadly divided into two types: optical and magnetic, but here we will explain the optical type.

[0003] FIG. 6 is a diagram showing the structure of a typical optical linear encoder.

[0004] The optical linear encoder shown in Figure 6 comprises a scale 1, a slider 2, a main scale 3, a steel base 4, an aluminum case 5, and a lip seal 6. The glass surface of the main scale 3 has evenly spaced gratings. The main scale 3 is adhesively fixed inside the steel base 4. The steel base 4 also mounts the scale 1 to the machine. The aluminum case 5 is provided to prevent shaft lubricant, cutting fluid, chips, etc. from entering the inside of the scale 1. The lip seal 6 maintains the airtightness of the inside of the scale 1 and, like the aluminum case 5, is also attached to prevent shaft lubricant, etc. from entering the inside of the scale 1.

[0005] As shown in FIG. 6 , the optical linear encoder further includes a light-emitting unit 7, a light-receiving unit 8, a signal amplifier circuit board 9, a signal calculation circuit board 10, a slider frame 11, a light-receiving unit mounting portion 12, and a machine mounting portion 13. The signal amplifier circuit board 9 is a signal amplifier circuit board for the light-receiving unit 8. Of the parallel light output from the light-emitting unit 7, the parallel light that passes through the grating of the main scale 3 is converted into an electrical signal by the light-receiving unit 8 and the signal amplifier circuit board 9. The signal calculation circuit board 10 calculates the position of the slider 2 from the signal output from the signal amplifier circuit board 9. The slider frame 11 refers to the entire slider frame, and the light-emitting unit 7, light-receiving unit 8, signal amplifier circuit board 9, and signal calculation circuit board 10 are mounted on the slider frame 11. The light-receiving unit mounting portion 12 is a part of the slider frame 11 that mounts the light-receiving unit 8 to the slider frame 11. The machine mounting portion 13 is a portion of the slider frame 11 that mounts the slider 2 to a machine.

[0006] Optical linear encoders are also classified into two types, shielded and open, depending on whether they have a protective structure. As shown in Figure 6, the shielded type has a structure in which the slider 2, main scale 3, etc. are enclosed in an aluminum case 5 or the like to protect them from shaft lubricant, cutting fluid, chips, etc. The open type has a structure in which the slider 2, main scale 3, etc. are not enclosed in an aluminum case 5 or the like, as they are used in environments such as clean rooms.

[0007] The shielded type will be explained below. Shielded types are classified into the following two types depending on the configuration of the slider frame. The first type is a type in which the slider frame 11 is made up of two parts, a light-receiving unit mounting part 12 and a machine mounting part 13, which are connected by a spring or the like, and the light-receiving unit mounting part 12 moves while contacting a guide inside the scale 1. The second type is a type in which there is no guide inside the scale 1, and the light-receiving unit mounting part 12 and machine mounting part 13 of the slider frame 11 are integrated, and the light-receiving unit mounting part 12 moves without contacting anything other than the lip seal 6.

[0008] In the first shielded type described above, the light receiving unit mounting part 12 and the machine mounting part 13 are separated, and interference between the light receiving unit mounting part 12 and the main scale 3 is prevented, so the light receiving unit mounting part 12 moves while contacting a guide inside the scale 1. For this reason, no special care is required when mounting the slider 2 to the machine. However, because of the separated structure, lost motion occurs between the light receiving unit mounting part 12 and the machine mounting part 13, and this lost motion may affect the position detection accuracy.

[0009] In the second shielded type described above, the light receiving unit mounting portion 12 and the machine mounting portion 13 are an integrated structure, so lost motion does not occur. With this structure, accurate mounting of the slider 2 to the machine prevents interference between the light receiving unit mounting portion 12 and the main scale 3. Therefore, if the mounting accuracy of the slider 2 to the machine is poor, there is a possibility that interference will occur between the light receiving unit mounting portion 12 and the main scale 3 inside the scale 1.

[0010] Next, we will explain the machine side where the linear encoder is attached. The scale 1 and slider 2 are attached to the fixed part or movable part of the machine. In some cases, the scale 1 is attached to the fixed part and the slider 2 is attached to the movable part, and in other cases, the scale 1 is attached to the movable part and the slider 2 is attached to the fixed part. Examples of fixed parts include a bed and a saddle. Examples of movable parts include a table and a ram. Furthermore, the fixed and movable parts of the machine are combined with sliding guide surfaces, rolling guide surfaces, hydrostatic guide surfaces, etc.

[0011] If the guide surface that guides the movement of the moving part relative to the fixed part of a machine is a sliding guide surface, the fixed and moving parts are in contact when the moving part is stopped or operating at a low speed. On the other hand, as the operating speed of the moving part increases, the fixed and moving parts are put out of contact due to a lubricating oil film. If the guide surface is a rolling guide surface, the fixed and moving parts are always in contact, whether the moving part is operating or stopped. If the guide surface is a hydrostatic guide surface, the fixed and moving parts are always out of contact, whether the moving part is operating or stopped.

[0012] 7 and 8 show an example of a conventional technique for a feed axis of a machine tool or the like that has a sliding guide surface and is equipped with an optical linear encoder.

[0013] As shown in Figure 7, the machine has a fixed part 21 and a movable part 22. In Figure 7, the fixed part 21 of the machine is a saddle in this example, and has a linear encoder scale 1 attached to it. The movable part 22 of the machine is a ram in this example, and has a linear encoder slider 2 attached to it. The scale 1 is a shielded type, as shown in Figure 6. The slider 2 has an integrated structure in which the light-receiving unit mounting part 12 and the machine mounting part 13 of the slider frame 11 are integrated, and the light-receiving unit mounting part 12 moves inside the scale 1 without coming into contact with anything other than the lip seal 6.

[0014] In FIG. 8, the signal amplifier circuit board 9, signal calculation circuit board 10, slider frame 11, light-receiving unit mounting portion 12, and machine mounting portion 13 have the same configurations as the components of the optical linear encoder shown in FIG. 6. When the signal amplifier circuit board 9 and the signal calculation circuit board 10 are fixed to the slider frame 11 with screws, the ground (GND) potential of the signal amplifier circuit board 9 and the signal calculation circuit board 10 via the screws becomes the same as the slider frame 11. Also, as shown in FIG. 8, the machine equipped with the optical linear encoder includes a cable 23, a unit 24, a distribution board 25, and an earth bar 26. The cable 23 supplies circuit power to the slider 2. The cable 23 also transfers position data of the slider 2 calculated by the signal calculation circuit board 10 to a downstream unit 24. The unit 24 is a servo drive unit for driving a feed axis servo motor and a spindle servo motor (not shown). The earth bar 26 is at the same potential as the machine ground potential.

[0015] When a machine equipped with an optical linear encoder is equipped with a spindle for machining a workpiece, such as an NC machine tool, so-called electromagnetic noise, known as PWM noise due to PWM control, is superimposed on the current flowing through the power cable of the spindle servo motor. This electromagnetic noise is emitted from inside the power cable of the spindle servo motor to the outside, or flows into the earth cable of the spindle servo motor. This electromagnetic noise also flows from the machine body to the ground through the fixed part 21 and movable part 22 of the machine to which the housing of the spindle servo motor is fixed.

[0016] In FIG. 7, the housing of the spindle servo motor (not shown) is fixed to the ram of the movable part 22. When the movable part 22 is stopped or operating at a low speed, the saddle of the fixed part 21 and the ram of the movable part 22 are in contact and at the same potential. As a result, electromagnetic noise flows from the ram of the movable part 22 through the saddle of the fixed part 21 to the machine body and then to the ground, or through the earth cable of the spindle servo motor. On the other hand, when the operating speed increases, electromagnetic noise flows only through the earth cable. This is because the saddle of the fixed part 21 and the ram of the movable part 22 are in a non-contact state due to a lubricating oil film, and the ram of the movable part 22 is insulated from the machine body.

[0017] If the earth cable for the spindle servo motor is long, the earth cable itself becomes an impedance, making it difficult for electromagnetic noise to flow through the earth cable. As a result, the electromagnetic noise remains stored as energy in the ram of the movable part 22, and the circuit signals on the signal amplifier circuit board 9 of the light receiving unit 8 of the slider 2 attached to the ram of the movable part 22 and the signal calculation circuit board 10 inside the slider 2 are affected by this electromagnetic noise, causing fluttering.

[0018] Next, when the operating speed of the movable part 22 changes from high to low or comes to a stop, the saddle of the fixed part 21 and the ram of the movable part 22 come into contact again, and the electromagnetic noise energy stored in the ram of the movable part 22 flows from the ram of the movable part 22 through the saddle of the fixed part 21 and from the machine body to the ground.

[0019] As a result, the circuit signals on the signal amplifier circuit board 9 of the light receiving unit 8 of the slider 2 attached to the ram of the movable part 22 and the signal calculation circuit board 10 inside the slider 2 are no longer affected by this electromagnetic noise, and the fluttering phenomenon is eliminated.

[0020] To solve the problem of circuit signals fluttering due to the influence of electromagnetic noise as described above, fixed part 21 and movable part 22 can be connected with an earth cable so that fixed part 21 and movable part 22 are always at the same potential. However, if the movable range of movable part 22 is long, the earth cable must be long. In this case, the earth cable itself becomes an impedance, making it difficult for electromagnetic noise to flow through the earth cable, so fixed part 21 and movable part 22 are not necessarily at the same potential.

[0021] Furthermore, in order to reduce electromagnetic noise from the spindle servo motor, it is sufficient to connect a noise filter to the power cable of the spindle servo motor. However, noise filters are generally expensive, and because the noise filter itself is large, a separate installation location is required. Furthermore, noise filters do not always provide the desired countermeasure against electromagnetic noise. Summary of the Invention [Problem to be solved by the invention]

[0022] In conventional technology, when the scale of an optical linear encoder is a shielded type and the slider moves inside the scale without touching anything, if the fixed part and movable part of a machine having a sliding guide surface are not in contact with each other due to a lubricating oil film during axis operation, the electromagnetic noise from the spindle servo motor causes the circuit signals of the slider's signal amplification circuit board and signal calculation circuit board to flutter. To eliminate this flutter, the fixed part and movable part of the machine can be connected with an earth cable, but if the movable part has a long range of motion, a long earth cable must be wired, and in this case, the earth cable itself becomes an impedance, which poses the problem that the fixed part and movable part are not necessarily at the same potential.

[0023] Furthermore, in order to reduce electromagnetic noise from the spindle servo motor, it is sufficient to connect a noise filter to the power cable of the spindle servo motor, but the noise filter itself is expensive, a dedicated installation location is required, and there are problems in that it is not always possible to provide the desired countermeasure against electromagnetic noise.

[0024] The present invention has been made in view of the above circumstances, and aims to provide a means for solving the problem that, in an optical linear encoder having a shielded scale in which a slider moves without coming into contact with anything inside the scale, when the fixed part and movable part of a machine having a sliding guide surface are in a non-contact state due to a lubricating oil film during axial operation, the circuit signals of the slider's signal amplification circuit board and signal calculation circuit board flutter due to the influence of electromagnetic noise from the spindle servo motor. [Means for solving the problem]

[0025] The mechanical system disclosed in this specification comprises a linear encoder having a scale and a slider, a machine to which the linear encoder is attached, the machine having a fixed part and a movable part, a conductive part that is electrically connected to one of the slider and the scale, a contact part that is electrically connected to the other of the slider and the scale, and a contactor attached to the conductive part, wherein when the scale is attached to the fixed part, the slider is attached to the movable part, and when the scale is attached to the movable part, the slider is attached to the fixed part, and when the operating speed of the movable part or the contact resistance between the movable part and the fixed part exceeds a threshold, the contactor comes into contact with the contact part so that the scale and the slider are electrically at the same potential.

[0026] The slider also includes a slider frame attached to the movable part or the fixed part, a light-receiving unit, a signal amplification circuit board of the light-receiving unit, and a signal calculation circuit board that calculates the position of the slider from a signal output from the signal amplification circuit board, the signal amplification circuit board and the signal calculation circuit board being insulated and separated from the slider frame, and the signal amplification circuit board and the signal calculation circuit board being connected to the machine via a cable that connects to the slider, thereby maintaining the GND potential at a stable level.

[0027] The conductive portion is a part of the movable portion, and the contact portion is a part of the fixed portion.

[0028] In addition, the surface where the movable part and the fixed part are in contact is a sliding guide surface, and the threshold value is defined based on the value when the movable part and the fixed part change from a contact state to a non-contact state.

[0029] Furthermore, a conductive roller that comes into contact with the contact piece and establishes electrical continuity is attached to the tip of the contact piece that comes into contact with the contact portion. [Effects of the Invention]

[0030] According to the present invention, it is possible to suppress the occurrence of the phenomenon in which the circuit signals of the signal amplifier circuit board and the signal calculation circuit board of the slider flutter due to the influence of electromagnetic noise from the spindle servo motor, without connecting the fixed part and the movable part of the machine with an earth cable and without connecting a noise filter to the power cable of the spindle servo motor. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 is a diagram illustrating a first embodiment of the present invention. [Figure 2] 10A and 10B are diagrams showing the states of the contacts and the fixed part relative to the speed of the movable part in the first embodiment of the present invention. [Figure 3] FIG. 10 is a diagram illustrating a second embodiment of the present invention. [Figure 4]10A and 10B are diagrams showing the states of the contacts and the fixed part relative to the speed of the movable part in the second embodiment of the present invention. [Figure 5] FIG. 10 is a diagram illustrating a third embodiment of the present invention. [Figure 6] FIG. 1 is a diagram illustrating the structure of an optical linear encoder. [Figure 7] FIG. 1 is a diagram showing a conventional embodiment. [Figure 8] FIG. 10 is a diagram showing another conventional embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0032] FIG. 1 is a diagram illustrating a first embodiment of the present invention. FIG. 2 is a diagram illustrating the state of a contactor and a fixed portion relative to the speed of a movable portion in the first embodiment of the present invention. More specifically, FIG. 1 is a diagram schematically illustrating a mechanical system including a linear encoder and a machine. The mechanical system illustrated in FIG. 1 differs from the conventional embodiment illustrated in FIG. 7 in that a contactor 27 is provided. The contactor 27 is attached to a conductive portion 31 and is capable of contacting a contact portion 32. The conductive portion 31 is a portion that is electrically connected to one of the scale 1 and the slider 2, and the contact portion 32 is a portion that is electrically connected to the other of the scale 1 and the slider 2. In this example, the conductive portion 31 is a portion that is electrically connected to the movable portion 22 and is electrically connected to the slider 2. The contact portion 32 is a portion of the fixed portion 21 and is electrically connected to the scale 1. In FIG. 1, the conductive portion 31, which is a portion of the movable portion 22, is indicated by a darker shade, and the contact portion 32, which is a portion of the fixed portion 21, is indicated by a lighter shade. In this example, the scale 1 is attached to the fixed part 21 and the slider 2 is attached to the movable part 22, but the scale 1 may be attached to the movable part 22 and the slider 2 may be attached to the fixed part 21.

[0033] When the movable part 22 is operating at a low speed, the fixed part 21 and the movable part 22 are not in a non-contact state, and the movable part 22 operates with a part of the movable part 22 in contact with the fixed part 21. On the other hand, as the operating speed of the movable part 22 increases, the fixed part 21 and the movable part 22 come out of contact with each other due to the lubricating oil film between the fixed part 21 and the movable part 22. As a result, electromagnetic noise from a spindle servo motor (not shown) mounted on the movable part 22 cannot flow to the fixed part 21.

[0034] Here, when the operating speed of the movable part 22 detected by a rotary encoder built in a servo motor (not shown) for driving the movable part 22 exceeds a threshold V1 set as shown in FIG. 2 , it is determined that the fixed part 21 and the movable part 22 have changed from a contact state to a non-contact state. At this time, a contactor 27 attached to a conductive part 31 electrically connected to the slider 2 (in other words, the contactor 27 provided on the movable part 22 in this example) is brought into contact with a contact part 32 electrically connected to the scale 1 (in other words, the contact part 32 provided on the fixed part 21 in this example). The contactor 27 comes into contact with the contact part 32 by being displaced or deformed. For example, the contactor 27 has a bar that can swing around a predetermined axis, and when the operating speed exceeds the threshold V1, the contactor 27 swings in a direction toward the contact part 32 to come into contact with the contact part 32. Alternatively, when the operating speed exceeds the threshold V1, the contactor 27 may move to a position where it comes into contact with the contact part 32. To displace or deform the contactor 27, the contactor 27 may have an electric actuator powered by, for example, a motor, an electromagnetic cylinder, or an air cylinder. Furthermore, a controller having a processor and memory, or an electric circuit, may be provided to control the driving of the electric actuator. The electric circuit may include, for example, a comparator that compares an electric signal indicating the operating speed with a threshold value, and a conversion circuit that converts the output signal from the comparator into a drive signal for the electric actuator. Furthermore, the portion of the contactor 27 attached to the conductive portion 31 and the portion that contacts the contact portion 32 are electrically connected by a conductive material. Therefore, contact between the contactor 27 and the contact portion 32 brings the scale 1 and the slider 2 into the same electrical potential.

[0035] Furthermore, when the operating speed of the movable part 22 becomes equal to or less than the threshold value V1, it is determined that the fixed part 21 and the movable part 22 have changed from a non-contact state to a contact state. At this time, the contactor 27 and the contact part 32 are prevented from contacting each other.

[0036] As a result, the fixed part 21 and the movable part 22 are always in contact regardless of the operating speed of the movable part 22, so that the electromagnetic noise from the movable part 22 flows to the fixed part 21, and the slider 2 becomes less susceptible to the effects of the electromagnetic noise.

[0037] The threshold value V1 to be set varies depending on the size and structure of the machine, changes over time in the machine, the amount of lubricant applied, etc., and can be adjusted as needed. In addition, in order to suppress wear due to contact with contact portion 32 and vibration of movable portion 22 due to reaction force from contact portion 32, contactor 27 has a conductive roller 27a (e.g., a roller made of conductive metal) attached to its tip, which comes into contact with contactor 27 for electrical conduction, and contactor 27 and roller 27a are configured with a contact mechanism such as a conductive spring (not shown).

[0038] Fig. 3 is a diagram showing a second embodiment of the present invention. Fig. 4 is a diagram showing the state of the contactor and the fixed part relative to the speed of the movable part in the second embodiment of the present invention. Fig. 3 differs from Fig. 7, which shows the conventional embodiment, in that contactor 27 and circuit 28 for measuring the contact resistance between fixed part 21 and movable part 22 are provided.

[0039] In the second embodiment, instead of continuously measuring the operating speed of the movable part 22 as in the first embodiment, the contact resistance between the fixed part 21 and the movable part 22 is measured. When this contact resistance exceeds a threshold V2 set as shown in Fig. 4, it is determined that a state has been reached in which electromagnetic noise no longer flows from the movable part 22 to the fixed part 21. At this time, a contactor 27 attached to a conductive part 31 that is conductive with the slider 2 (in other words, the contactor 27 provided on the movable part 22 in this embodiment) is brought into contact with a contact part 32 that is conductive with the scale 1 (in other words, the contact part 32 provided on the fixed part 21 in this embodiment). This contact between the contactor 27 and the contact part 32 makes the scale 1 and the slider 2 electrically equivalent in potential.

[0040] Furthermore, when the contact resistance becomes equal to or less than the threshold value V2, it is determined that electromagnetic noise is flowing from the movable part 22 to the fixed part 21. At this time, the contactor 27 and the contact part 32 are prevented from contacting each other.

[0041] As a result, the fixed part 21 and the movable part 22 are always in contact regardless of the operating speed of the movable part 22, so that electromagnetic noise from the movable part 22 flows to the fixed part 21, making the slider 2 less susceptible to the effects of electromagnetic noise.

[0042] The threshold value V2 to be set varies depending on the size and structure of the machine, aging of the machine, the amount of lubricant oil applied, etc., so it can be adjusted and set as needed. The structure of the contact 27 is the same as in the first embodiment.

[0043] Fig. 5 is a diagram showing a third embodiment of the present invention. In the embodiment of Fig. 5, the GND potential of the signal amplifier circuit board 9 of the light-receiving unit 8 and the signal calculation circuit board 10 inside the slider 2 are insulated and separated from the slider frame 11, i.e., the main body of the slider 2. Although some parts are not shown in the figure, in the third embodiment, the slider 2 includes the slider frame 11, the light-receiving unit 8, the signal amplifier circuit board 9, and the signal calculation circuit board 10.

[0044] When the slider frame 11 is attached to the movable part 22 and the GND potential of the signal amplifier circuit board 9 and the signal calculation circuit board 10 is the same as that of the slider frame 11, if the fixed part 21 and the movable part 22 are not in contact with each other, the electromagnetic noise superimposed on the movable part 22 will be superimposed on the GND potential of the signal amplifier circuit board 9 and the signal calculation circuit board 10 through the slider frame 11. In this case, the circuit signals will be affected by the electromagnetic noise.

[0045] Therefore, by insulating and separating the signal amplifying circuit board 9 and the signal calculating circuit board 10 from the slider frame 11, the circuit signals are made less susceptible to the effects of electromagnetic noise.

[0046] The signal amplifying circuit board 9 and the signal calculating circuit board 10 are at the same potential as the fixed part 21 of the machine through the cable 23 connected to the slider 2. Furthermore, the signal amplifying circuit board 9 and the signal calculating circuit board 10 are connected to the earth bar 26 of the switchboard 25, which is at the same potential as the ground potential of the machine, so that the GND potential is at a stable level.

[0047] The above description is merely an example. In the mechanical system disclosed in this specification, the contactor 27 attached to the conductive portion 31 is configured to contact the contact portion 32 so that the scale 1 and the slider 2 are electrically at the same potential when the operating speed of the movable portion 22 or the contact resistance between the movable portion 22 and the fixed portion 21 exceeds a threshold. Therefore, other configurations may be changed as appropriate. For example, in the embodiment, the conductive portion 31 is electrically connected to the slider 2 attached to the movable portion 22. As shown in FIG. 1 , the conductive portion 31 is part of the movable portion 22. However, the configuration of the conductive portion 31 is not limited to this, and the conductive portion 31 may be part of the scale 1, the slider 2, or the fixed portion 21. Similarly, the contact portion 32 may be part of the scale 1, the slider 2, or the movable portion 22. In other words, the contactor 27 is not limited to being attached to the movable portion 22, but may be attached to any of the scale 1, the slider 2, and the fixed portion 21. [Explanation of symbols]

[0048] 1 Scale, 2 Slider, 3 Main scale within scale, 4 Steel base, 5 Aluminum case, 6 Lip seal, 7 Light emitting unit, 8 Light receiving unit, 9 Signal amplification circuit board of light receiving unit 8, 10 Signal calculation circuit board, 11 Slider frame, 12 Mounting portion of light receiving unit 8 on slider frame 11, 13 Machine mounting portion on slider frame 11, 21 Fixed portion of machine, 22 Moving portion of machine, 23 Cable connected to slider, 24 Servo drive unit, 25 Distribution board, 26 Earth bar, 27 Contactor, 27a Roller, 28 Circuit for measuring contact resistance between fixed portion 21 and moving portion 22, 31 Conductive portion, 32 Contact portion.

Claims

1. a linear encoder including a scale and a slider; a machine to which the linear encoder is attached, the machine comprising a fixed part and a movable part; a conductive portion electrically connected to one of the slider and the scale; a contact portion electrically connected to the other of the slider and the scale; a contact attached to the conductive portion; Equipped with When the scale is attached to the fixed part, the slider is attached to the movable part, and when the scale is attached to the movable part, the slider is attached to the fixed part; the contactor comes into contact with the contact portion so that the scale and the slider are electrically at the same potential when the operating speed of the movable portion or the contact resistance between the movable portion and the fixed portion exceeds a threshold value. A mechanical system characterized by:

2. The slider includes: a slider frame attached to the movable portion or the fixed portion; A light receiving unit; a signal amplification circuit board of the light receiving unit; a signal calculation circuit board that calculates the position of the slider from the signal output from the signal amplification circuit board; Equipped with the signal amplifying circuit board and the signal calculating circuit board are insulated and separated from the slider frame, The signal amplification circuit board and the signal calculation circuit board are connected to the machine via a cable connected to the slider, thereby maintaining a stable GND potential. The mechanical system of claim 1 .

3. the conductive portion is a part of the movable portion, and the contact portion is a part of the fixed portion; The mechanical system of claim 1 .

4. a surface where the movable portion and the fixed portion are in contact with each other is a sliding guide surface; The threshold value is defined based on a value when the movable part and the fixed part change from a contact state to a non-contact state. The mechanical system of claim 1 .

5. A conductive roller is attached to the tip of the contactor on the side that comes into contact with the contact portion, and the roller comes into contact with the contactor to establish electrical continuity. The mechanical system of claim 1 .

Images