JP5671353B2 - Encoder, motor unit, and actuator system - Google Patents

Description

  The present invention relates to an encoder, a motor unit, and an actuator system.

  Many electric actuators are used in highly automated factories and the like. The motor units of these electric actuators have an encoder that detects the number of rotations and the rotation angle (absolute position). And in such an encoder, in order to raise the operation rate of factory facilities etc., the absolute encoder which does not require an origin return operation after power-on is used in many cases.

  The absolute encoder generally includes a battery and a memory, and stores the number of rotations of the motor shaft in the memory by battery backup when the power is turned off. When the power is turned on, the rotational speed is read from the memory, and the rotational speed is newly added to the rotational speed. However, the battery must be periodically replaced, and there is a possibility that a malfunction that cannot be normally performed due to a voltage drop of the battery may occur. In addition, if the shaft rotates when the power is turned off, an error may occur in the rotational speed. Therefore, there is a demand for an absolute encoder that does not use a battery.

  On the other hand, the following patent document discloses an encoder that has a plurality of gears without using a battery and detects the number of rotations based on a combination of rotation angles of these gears.

Japanese Patent Publication No. 5-38243 JP 2010-44055 A

  However, in the encoders described in Patent Documents 1 and 2, the plurality of driven gears are connected so that the rotational force of the main driving gear that rotates integrally with the rotating shaft is transmitted in series. For this reason, in order to prevent the accumulation | aggregation | set of the backlash of a gearwheel, it is necessary to use a highly accurate and costly gearwheel. Moreover, since many driven gears are used, the encoder becomes large.

  The present invention has been made under the circumstances described above, and an object thereof is to provide a small-sized, low-cost, high-reliability encoder or the like.

In order to achieve the above object, an encoder according to the first aspect of the present invention provides:
A main driving gear formed with a first optical track having a pattern that rotates together with a rotating body and indicates a rotation angle;
A first driven gear which is arranged so as to mesh with the main driving gear, rotates by transmitting the rotation of the rotating body via the main driving gear, and has a second optical track formed of a pattern indicating a rotation angle; ,
A second driven gear disposed so as to mesh with the main driving gear, and rotated by transmitting the rotation of the rotating body via the main driving gear, and formed with a third optical track having a pattern indicating a rotation angle; ,
Comprising at least
To the teeth of the main driving gear, the first driven gear, and the second driven gear, tooth number numbers for identifying the respective teeth are given,
The first optical track, the second optical track, and the third optical track are irradiated with light, and the reflected light reflected by the first optical track, the second optical track, and the third optical track is reflected. received light, by outputting a signal corresponding to the intensity of the reflected light, and a light detecting means for detecting at least said first optical track, said second optical track, and light from the third optical track,
First calculating means for calculating a rotation angle of the rotating body and the main driving gear based on a signal corresponding to the intensity of the reflected light reflected by the first optical track;
Second computing means for computing a rotation angle of the first driven gear based on a signal corresponding to the intensity of the reflected light reflected by the second optical track;
Third computing means for computing a rotation angle of the second driven gear based on a signal corresponding to the intensity of the reflected light reflected by the third optical track;
Based on the rotation angle of each of the main driving gear, the first driven gear, and the second driven gear, the number of teeth of the tooth at a predetermined position is calculated, and based on the combination of the number of teeth Fourth calculation means for calculating the number of rotations of the rotating body;
Equipped with a,
The fourth calculating means determines the timing at which the number of teeth of the main gear changes to the next number of teeth, and adjusts the teeth of the first driven gear and the second driven gear according to the timing. It is characterized by switching several numbers .

  The number of teeth of the main driving gear may be larger than the number of teeth of the first driven gear and the second driven gear.

Said first optical track, said second optical track, and the third optical track, that the high reflectance region and the low reflectance region, PN (Pseudo Noise, Pseudo Random Noise) are arranged on the basis of the code sequence It may be constituted by.

The main gear is formed with a fourth optical track configured by alternately arranging high reflectance regions and low reflectance regions at equal intervals,
The light detecting means irradiates the fourth optical track of the rotating main driving gear with light, receives reflected light reflected by the fourth optical track, and has a period of 1 according to the intensity of the reflected light. Two signals whose phases are different from each other by / 4 may be output.

The light detection means has a plurality of sensor elements for detecting light from the first optical track,
The first computing means is in the vicinity of the boundary between the high reflectance region and the low reflectance region of the first optical track based on the two signals whose phases are different from each other by ¼ of the period. The output of the sensor element other than the output of the sensor element that has detected the reflected light is selected, and the rotation angle of the rotating body and the main driving gear is determined based on the signal output from the selected sensor element. You may calculate.

The motor unit according to the second aspect of the present invention is:
A shaft,
A rotor provided on the shaft;
A stator that rotates the shaft together with the rotor by electromagnetic interaction with the rotor;
An encoder according to a first aspect of the present invention for detecting rotation of the shaft;
It is characterized by providing.

An actuator system according to a third aspect of the present invention is:
A motor unit according to a second aspect of the present invention;
Control means for controlling the motor unit based on the detection result of the encoder;
It is characterized by providing.

  The encoder of the present invention detects light from each of the optical tracks formed on the main driving gear and the first driven gear and the second driven gear meshing with the main driving gear, thereby rotating the rotating body. It becomes possible to determine the angle and the number of rotations. Therefore, since any driven gear directly meshes with the main driving gear, it is possible to prevent detection problems due to accumulation of gear backlash and the like, and to reduce the size of the apparatus.

It is a perspective view showing an actuator concerning a 1st embodiment of the present invention. It is a perspective view which shows a motor unit. It is XY sectional drawing which shows a motor unit. It is sectional drawing which shows an encoder unit. It is YZ sectional drawing which shows an encoder unit. (A) is a front view which shows a main drive gear, (B) is a front view which expands and shows a part of main drive gear. (A) is a front view (the 1) which shows a driven gear, (B) is a front view (the 2) which shows a driven gear. (A) is a front view which shows a detection unit, (B) is BB sectional drawing of (A). It is a block diagram which shows an encoder unit and a controller. (A) And (B) is a figure for demonstrating the selection method of the sensor element of an absolute position calculator. It is a figure of the table which shows correspondence number of teeth number and rotation speed. It is a block diagram concerning the modification of an encoder unit.

  Hereinafter, a motor unit 10 according to an embodiment of the present invention will be described. For easy understanding, XYZ coordinates with the X axis as the front direction of the motor unit 10, the Y axis as the vertical direction, and the Z axis as the side surface direction are set and referred to as appropriate.

  As shown in FIG. 1, the motor unit 10 is attached inside an actuator 200 including a slider 201 that reciprocates in the X-axis direction, for example. Inside the actuator 200, a ball screw and a ball nut to which the slider 201 is fixed are installed. The lead of the ball screw is, for example, 10 mm. This ball screw is connected to the rotating shaft of the motor unit 10. The ball screw rotates together with the rotating shaft by the rotating force of the rotating shaft of the motor unit 10. Further, the ball nut moves in the X-axis direction as the ball screw rotates. By this movement of the ball nut, the slider 201 moves in the X-axis direction. A cable 202 is connected to the actuator 200. A controller to be described later is connected to the other end of the cable 202.

  As shown in FIG. 2, the motor unit 10 includes a servo motor 20, a shaft 30 that is rotated around an axis parallel to the X axis by the servo motor 20, a rotation angle (absolute position), and a rotation speed of the shaft 30. And an encoder unit 40 for detection.

  The servo motor 20 has a housing 21 formed in a hollow rectangular parallelepiped shape. Cutout portions 21a along the X axis are formed at corner portions of the housing 21 parallel to the X axis. Further, an attachment portion 21b in which a through hole is formed is formed at an end portion on the + X side of the housing 21. The motor unit 10 is fixed inside the actuator 200 by bolts and screws inserted into the through holes of the mounting portion 21b. Further, as shown in FIG. 3, circular openings 21c and 21d penetrating in the X-axis direction are formed on the −X side and the + X side of the housing 21, respectively. The shaft 30 is inserted into the openings 21c and 21d.

  The servomotor 20 includes a rotor 22 fixed to the outer peripheral surface of the shaft 30, a stator 23 disposed so as to surround the outer periphery of the rotor 22, and a pair of bearings 24 a and 24 b that support the shaft 30. It is stored.

  The rotor 22 is formed in a cylindrical shape and has a through hole through which the shaft 30 passes. The rotor 22 is magnetized so that a plurality of N poles and S poles appear alternately along a circumference around the shaft 30.

  The stator 23 is formed in a cylindrical shape. The stator 23 has a plurality of poles facing the rotor 22 along a circumference around the shaft 30. The plurality of poles is divided into several groups. And the coil of the pole which comprises each group is connected in series.

  The bearings 24 a and 24 b support the shaft 30 so as to be rotatable, and are disposed inside the housing 21 so as to be coaxial with the openings 21 c and 21 d of the housing 21. The shaft 30 is inserted into the bearings 24a and 24b.

  The shaft 30 is formed in a cylindrical shape whose longitudinal direction is the X-axis direction. The shaft 30 is inserted into the openings 21 c and 21 d and the bearings 24 a and 24 b of the housing 21, so that both ends in the X-axis direction are rotatably supported in a state of projecting from the housing 21 to the outside.

  4 and 5 are sectional views showing the encoder unit 40, and FIG. 4 is a sectional view taken along line IV-IV in FIG. As shown in FIGS. 4 and 5, the encoder unit 40 includes a main driving gear 50 fixed to the shaft 30, driven gears 60 and 70 to which the rotation of the main driving gear 50 is transmitted, and the −X side of the main driving gear 50. The encoder base 41 is disposed, the encoder base 43 that rotatably supports the driven gears 60 and 70 via the shafts 46 and 47, and the casing 42 that accommodates them. Further, the shafts 46 and 47 are rotatably attached to the encoder base 43 through the bearings 44.

  As shown in FIG. 6A, the main driving gear 50 is configured as a spur gear having a plurality of tooth portions 51 formed on the outer periphery. The number of the tooth portions 51 is arbitrary, but 41 tooth portions 51 are formed on the outer periphery of the main driving gear 50 of the present embodiment. Each tooth 51 has a No. 1 to No. Teeth number numbers up to 41 are given. A circular opening 52 is formed in the central portion of the main driving gear 50. The main gear 50 is fixed to the shaft 30 by fitting the small diameter portion 31 formed at the end portion on the −X side of the shaft 30 into the opening 52. Thereby, the main driving gear 50 rotates together with the shaft 30.

  On the surface of the main driving gear 50 on the −X side, a ring-shaped optical track 53 is formed around the rotation axis of the main driving gear 50. As shown in FIG. 6B, the optical track 53 is configured as an incremental scale by alternately arranging a plurality of sector-shaped high reflectance regions 53a and low reflectance regions 53b. The optical track 53 is formed to have a pitch of approximately 80 μm (high reflectance region 53a = approximately 40 μm, low reflectance region 53b = approximately 40 μm).

  A ring-shaped optical track 54 smaller than the diameter of the optical track 53 is formed on the surface of the main drive gear 50 on the −X side. The optical track 54 is configured as an absolute scale by arranging fan-shaped high reflectance regions 54a and low reflectance regions 54b based on a PN (Pseudo Noise, Pseudo Random Noise) code sequence. The optical track 54 is formed so that the bit width coincides with the angular pitch of the optical track 53 and corresponds thereto.

  As shown in FIG. 7A, the driven gear 60 is formed as a spur gear having a plurality of tooth portions 61 smaller than the number of tooth portions 51 of the main driving gear 50 and having a smaller diameter than the main driving gear 50. ing. The number of tooth portions 61 is, for example, 24, and each tooth portion 61 has a No. 1 in order. 1 to No. Teeth number numbers up to 24 are given. The number of teeth is assigned in the direction opposite to the direction in which the number of teeth is assigned to the tooth portion 51 of the main gear 50. A circular opening 62 is formed at the center of the driven gear 60. The driven gear 60 is fixed to the shaft 46 by fitting the small diameter portion 46 a formed at the end of the shaft 46 on the −X side into the opening 62. As a result, the driven gear 60 rotates together with the shaft 46. Similarly to the main gear 50, an optical track 63 configured as an incremental scale and an optical track 64 configured as an absolute scale are formed on the surface of the driven gear 60 on the −X side.

  As shown in FIG. 7B, the driven gear 70 is formed as a spur gear having a plurality of teeth 71 smaller than the number of teeth 51 of the main gear 50 and having a smaller diameter than the main gear 50. ing. The number of the tooth portions 71 is, for example, 23. 1 to No. Numbers of teeth up to 23 are given. The number of teeth is assigned in the direction opposite to the direction in which the number of teeth is assigned to the tooth portion 51 of the main gear 50. A circular opening 72 is formed at the center of the driven gear 70. The driven gear 70 is fixed to the shaft 47 by fitting the small diameter portion 47 a formed at the end of the shaft 47 on the −X side into the opening 72. As a result, the driven gear 70 rotates together with the shaft 47. Similarly to the main driving gear 50 and the driven gear 60, an optical track 73 configured as an incremental scale and an optical track 74 configured as an absolute scale are formed on the surface of the driven gear 70 on the −X side. Yes.

  Note that the number of teeth of the tooth portion 51 of the main gear 50 (41), the number of teeth of the tooth portion 61 of the driven gear 60 (24), and the number of teeth of the tooth portion 71 of the driven gear 70 (23) are mutually prime. It is formed so that it may become a relation.

  As shown in FIG. 5, the encoder substrate 41 is a rectangular member, for example, and is fixed to the casing 42. Further, detection units 80, 90, 100 for detecting the absolute position (rotation angle) and the rotation speed of the shaft 30 are mounted on the surface of the encoder board 41 on the + X side. The three detection units 80, 90, 100 are mounted so as to face the main driving gear 50 and the driven gears 60, 70, respectively.

  As shown in FIG. 8A, the detection unit 80 includes an LED light emitting unit 82 that irradiates light to the main driving gear 50, and an optical detector 83 that detects light reflected by the optical tracks 53 and 54 of the main driving gear 50. 84 and a detection unit main body 81 that supports them.

  As shown in FIG. 8B, the LED light emitting unit 82 is disposed near the center of the detection unit main body 81 and irradiates light to the optical tracks 53 and 54 of the main driving gear 50. The light emitted from the LED light emitting unit 82 is reflected with high reflectivity when entering the high reflectivity regions 53a and 54a, and is reflected or scattered with low reflectivity when entering the low reflectivity regions 53b and 54b. It is absorbed.

  The optical detector 83 is disposed on the −Y side of the LED light emitting unit 82 and detects two systems of light reflected on the optical track 53 (incremental scale) of the main driving gear 50. The phase difference between these two systems of light is 90 ° (1/4 pitch) when the pitch of the optical track 53 is 360 °. Then, the optical detector 83 outputs two systems of voltage signals corresponding to the detected intensity of the two systems of reflected light. The optical detector 83 includes, for example, two or two sets of photodiodes. Hereinafter, for convenience of explanation, it is assumed that two voltage signals output from the optical detector 83 are an A-phase signal and a B-phase signal, respectively.

  The optical detector 84 is disposed on the + Y side of the LED light emitting unit 82 and detects light reflected by the optical track 54 (absolute scale) of the main driving gear 50. And the voltage signal according to the intensity | strength of the detected reflected light is output. The optical detector 84 is composed of 512 CMOS image sensor elements.

  As shown in FIG. 9, the detection unit 80 includes a phase calculator 85, an absolute position calculator 86, a correction calculator 87, and a storage unit that stores information such as tables used by these calculators for calculation. It has further. These arithmetic units are configured as part of an FPGA (Field-Programmable Gate Array), for example.

By using the optical track 53 (incremental scale) formed so that the phase corresponds to the optical track 54 (absolute scale) and 1: 1, the phase calculator 85 allows the phase A signal output from the optical detector 83 to be output. The phase θ in one bit of the optical track 54 is calculated from the B phase signal based on the following equation (1).
θ = arc tan ⁻¹ (V _A / V _B ) (1)
Here, V _A is the output value of the sine wave signal in the A phase signal, and V _B is the output value of the sine wave signal in the B phase signal. Then, the phase calculator 85 outputs a signal corresponding to this phase θ. For example, when the phase θ in one bit is calculated as 45 ° based on the A phase signal and the B phase signal output from the optical detector 83, if 1 bit = 80 μm, the phase θ is 10 μm ( = 80 μm × 45/360).

The absolute position calculator 86 is used to calculate the absolute position Z _{0 in} units of bits of the optical track 54 (the rotation angle of the main gear 50 in units of bits (approximately 80 μm)) from the signal output from the optical detector 84. It is done. Hereinafter, the operation of the absolute position Z ₀ of the absolute position calculator 86 will be described.

  First, the absolute position calculator 86 selects only the output of the sensor element that detected stable reflected light from the 512 CMOS image sensor elements of the optical detector 84. Specifically, the absolute position calculator 86 is unstable in the vicinity of the boundary between the high reflectivity region 54a and the low reflectivity region 54b based on a signal corresponding to the phase θ from the phase calculator 85. The output of the sensor element other than the output of the sensor element that has detected the reflected light is selected.

  FIG. 10 is a diagram for explaining a method of selecting the sensor elements 84-1 to 84-3 performed by the absolute position calculator 86. For example, in FIG. 10A, the sensor element 84-1 is arranged so as to detect the vicinity of the phase 0 ° in one bit, and the sensor elements 84-2 and 84-3 are connected to the sensor element 84-1. On the other hand, they are arranged at intervals of 120 ° and 240 °. In this case, the absolute position calculator 86 detects the reflected light near the boundary between the high reflectance region 54a and the low reflectance region 54b based on the signal corresponding to the phase θ from the phase calculator 85. Other than the output of the sensor element 84-1, the output of the sensor elements 84-2 and 84-3 near the center (180 °) in one bit is selected. In FIG. 10B, the sensor elements 84-1 and 84-2 are arranged so as to detect the vicinity of the center (180 °) within one bit, and the sensor element 84-3 is disposed within one bit. It arrange | positions so that the phase 360 degree vicinity may be detected. In this case, the absolute position calculator 86 is the center in one bit other than the output of the sensor element 84-3 that detects the reflected light in the vicinity of the boundary between the high reflectance region 54a and the low reflectance region 54b. 180 °) The output of the sensor elements 84-1 and 84-2 in the vicinity is selected. As described above, the absolute position calculator 86 outputs the sensor element that performs stable detection other than the output of the sensor element that detects the reflected light near the boundary between the high reflectance region 54a and the low reflectance region 54b. Can be selected.

Then, the absolute position calculator 86, for example, by referring to the table showing the correspondence between the combination and the absolute position Z ₀ of the output signal of the sensor element stored in the storage unit, the selection of the optical detector 84 and it calculates the absolute position Z ₀ from an output signal of the sensor element. Then, the absolute position calculator 86 outputs a signal corresponding to the absolute position Z _0.

Returning to FIG. 9, the correction calculator 87 adds the phase θ output from the phase calculator 85 to the absolute position Z ₀ output from the absolute position calculator 86, thereby increasing the resolution higher than the absolute position Z _0. The absolute position Z is calculated. Then, the correction calculator 87 outputs a signal corresponding to the absolute position Z. For example, if the phase θ within 1 bit is 45 °, the phase θ = 10 μm is calculated when the 1-bit width is 80 μm. Therefore, by adding this phase θ = 10 μm to the absolute position Z ₀ , 1 An absolute position Z with higher resolution than the bit can be calculated.

  Similarly to the detection unit 80, the detection unit 90 includes an LED light emitting unit that irradiates light to the optical tracks 63 and 64 of the driven gear 60, and optical detectors 93 and 94 that detect light reflected by the optical tracks 63 and 64. , A phase calculator 95, an absolute position calculator 96, a correction calculator 97, and a storage unit for storing information such as a table. These phase calculator 95, absolute position calculator 96, and correction calculator 97 are configured as part of an FPGA, for example.

  The LED light emitting unit irradiates the optical tracks 63 and 64 of the driven gear 60 with light. The light emitted from the LED light emitting part is reflected with high reflectivity when entering the high reflectivity regions 63a and 64a, and is reflected or scattered or absorbed with low reflectivity when entering the low reflectivity regions 63b and 64b. Or

  The optical detector 93 detects two systems of light reflected on the optical track 63 (incremental scale) of the driven gear 60. The phase difference between these two systems of light is 90 ° (1/4 pitch) when the pitch of the optical track 63 is 360 °. Then, the optical detector 93 outputs two systems of A-phase signals and B-phase signals according to the detected intensity of the two systems of reflected light. The optical detector 93 is composed of, for example, two photodiodes.

  The optical detector 94 detects light reflected by the optical track 64 (absolute scale) of the driven gear 60. And the voltage signal according to the intensity | strength of the detected reflected light is output. The optical detector 94 is composed of, for example, a 512 pixel CMOS image sensor.

  The phase calculator 95 calculates the phase in one bit of the optical track 64 from the A-phase signal and B-phase signal output from the optical detector 93 based on the equation (1). Then, the phase calculator 95 outputs a signal corresponding to this phase.

The absolute position calculator 96 calculates the absolute position α _{0 in} units of bits of the optical track 64 (the rotation angle of the driven gear 60 in units of bits) from the signal output from the optical detector 94. Absolute position calculator 96, for example, by referring to the table showing the correspondence relationship between the voltage signal and the absolute position alpha ₀ from the optical detector 94 stored in the storage unit, calculates the absolute position alpha _0. Then, the absolute position calculator 96 outputs a signal corresponding to the absolute position alpha _0.

Correction arithmetic unit 97, the absolute position alpha ₀ output from the absolute position computing unit 96, by adding the output phase from the phase calculator 95, the absolute position alpha of higher resolution than the absolute position alpha ₀ operation To do. Then, the correction calculator 97 outputs a signal corresponding to the absolute position α.

Similarly to the detection units 80 and 90, the detection unit 100 includes an LED light emitting unit that irradiates light to the optical tracks 73 and 74 of the driven gear 70, and an optical detector 103 that detects the light reflected by the optical tracks 73 and 74. 104, a phase calculator 105, an absolute position calculator 106, and a correction calculator 107. Then, the correction computing unit 107 adds the phase output from the phase computing unit 105 to the absolute position β ₀ output from the absolute position computing unit 106, so that the absolute position β having higher resolution than the absolute position β ₀ is obtained. Is calculated. Then, the correction calculator 107 outputs a signal corresponding to the absolute position β.

  As shown in FIG. 9, the encoder unit 40 includes a rotation speed calculation unit 110 and an output unit 120 in addition to the detection units 80, 90, and 100.

  The rotation speed calculation unit 110 includes a rotation speed calculator 111 and a storage unit that stores information such as a table T indicating the correspondence between the tooth number and the rotation speed R. First, the rotational speed calculator 111 is on the −Y side of each of the main driving gear 50 and the driven gears 60 and 70 based on signals corresponding to the absolute positions Z, α, and β from the correction calculators 87, 97, and 107. The number of teeth of the tooth portions 51, 61, 71 is determined. At this time, the rotational speed calculator 111 determines the timing at which the number of teeth of the main driving gear 50 is switched to the next number of teeth based on the absolute position Z having a resolution finer than the number of teeth of the main driving gear 50. The number of teeth of each of the driven gears 60 and 70 is switched in accordance with the timing.

  Next, the rotational speed calculator 111 refers to the table T and calculates the rotational speed R of the shaft 30 from the combination of these tooth number numbers. Then, the rotational speed calculator 111 outputs a signal corresponding to the rotational speed R.

  FIG. 11 shows a specific example of the table T. This table T is an example in which the number of teeth of the main driving gear 50 and the driven gears 60 and 70 is set to 5, 4, and 3, respectively. In the table T shown in FIG. 11, the leftmost first column indicates a combination number of the number of teeth of the tooth portions 51, 61, 71 on the −Y side of each of the main driving gear 50 and the driven gears 60, 70. . The second column on the right side of the first column indicates the number of teeth of the tooth portion 51 on the −Y side of the main driving gear 50. Similarly, the third row and the fourth row indicate the number of teeth of the tooth portion 61 on the −Y side of the driven gear 60 and the number of teeth of the tooth portion 71 on the −Y side of the driven gear 70. The fifth column on the rightmost side of the table T indicates the rotational speed R of the shaft 30 (main drive gear 50).

  As can be seen from FIG. 11, the total number of combinations of the tooth number numbers of the main driving gear 50 and the driven gears 60 and 70 is 60 (60 = 5 × 4 × 3). For example, when the combination of each tooth number number is (No.1, No.2, No.3), the combination number is No.1. 006. Therefore, the rotational speed calculator 111 can calculate the rotational speed R = 1 of the shaft 30 by referring to the table T. Moreover, when the combination of each tooth number number is (No.1, No.2, No.2), the combination number is No.1. 026. Therefore, the rotational speed calculator 111 can calculate the rotational speed R of the shaft 30 as 5 by referring to this table T.

  However, the above example shows that even if the number of teeth of the driven gear 70 is different by one, the rotational speed calculator 111 outputs a significantly different rotational speed R. Therefore, the rotational speed calculator 111 of the present embodiment has the tooth number numbers of the main driving gear 50 and the driven gears 60 and 70 immediately before switching, immediately after switching, or after switching until the next switching. Is detected and determined. When these meshing states are different from each other, the rotation speed calculator 111 changes the meshing state (timing at which the tooth number number is switched) of each of the driven gears 60 and 70 to the meshing state (tooth number number tooth). The timing of switching to several numbers). For example, when the timing for switching the number of teeth of the main gear 50 is just after switching, and when the timing for switching the number of teeth of the driven gears 60 and 70 is just before switching, the rotational speed calculator 111 may change the number of driven gears 60, The timing at which the number of teeth number 70 is switched is set immediately after the timing is switched in accordance with the timing at which the number of teeth number of the main driving gear 50 is switched. That is, the rotation speed calculator 111 switches the number of teeth of the driven gears 60 and 70 in accordance with the switching timing of the number of teeth of the main gear 50. As a result, the rotation speed calculator 111 can determine the correct number of teeth for each of the main driving gear 50 and the driven gears 60 and 70, and as a result, can output an accurate rotation speed R.

  Such adjustment of the number of teeth of the gear is performed in order to prevent a state where the meshing state of the gear is changed due to the backlash of the gear. Specifically, in this embodiment, since all the driven gears 60 and 70 are meshed with the main driving gear 50, the meshing state of all the gears (such as the timing of switching the number of teeth) is essentially the same. It is desirable that However, depending on the size of the backlash of the gear, the meshing state of the gear may be different. On the other hand, in the present embodiment, the rotation speed calculator 111 outputs an accurate rotation speed R by switching the number of teeth of the driven gears 60 and 70 according to the main driving gear 50. Yes.

  Further, as described above, the resolutions of the absolute positions Z, α, β output from the detection units 80, 90, 100 are sufficiently finer than those of the tooth portions 51, 61, 71 of the main driving gear 50 and the driven gears 60, 70. . Therefore, for example, the rotation speed calculator 111 divides each tooth portion 51, 61, 71 into three timings (immediately before switching, immediately after switching, and immediately after switching until the next switching). To detect. In accordance with these three timings, the rotation speed calculator 111 switches the number of teeth of the driven gears 60 and 70, so that the rotation speed calculator 111 can change the number of teeth of the main driving gear 50 and the driven gears 60 and 70, respectively. Is prevented from being mistakenly determined.

  The rotation speed calculator 111 calculates the rotation speed R of the shaft 30 from the combination of these tooth number numbers with reference to the table T. However, the calculation method is arbitrary. For example, in this embodiment, the number of the combination of the number of teeth is a constant integer value, and the number of teeth of each gear (the main driving gear 50, the driven gear 60, 70) is a known value, The number of rotations of each gear is an unknown value (variable). Therefore, three linear equations composed of three variables can be created. Based on these equations, the rotational speed calculator 111 can also calculate the rotational speed R.

  In the present embodiment, the total number of combinations of the tooth number numbers of the main driving gear 50 and the driven gears 60 and 70 is 22,632 (22,632 = 41 × 24 × 23), and the encoder unit 40 is , 552 rotations (552 = 22,632 / 41). Therefore, since the lead of the ball screw of the actuator 200 is 10 mm as described above, the position of the slider 201 can be determined within the stroke range of 5,520 mm (5,520 = 552 × 10).

  As illustrated in FIG. 9, the output unit 120 includes a multiplexer 121 that switches between two sets of signals ({A, B} and {Z, R}), and a line driver 122.

  The multiplexer 121 first outputs a voltage signal corresponding to the absolute position Z output from the correction calculator 87 of the detection unit 80 and the rotation output from the rotation speed calculator 111 of the rotation speed calculation unit 110 after power-on or reset. A voltage signal corresponding to the number R is output. Based on these signals, the controller of the controller, which will be described later, determines the current position. Next, the multiplexer 121 switches between the A phase signal and the B phase signal output from the optical detector 83 of the detection unit 80, and outputs the A phase signal and the B phase signal. Based on these signals, the control unit counts up and down and updates the current position (incremental encoder function).

  The line driver 122 outputs a differential signal based on the difference between the signal output from the multiplexer 121 and a signal obtained by inverting the phase of this signal.

  As shown in FIG. 9, a controller 300 is connected to the motor unit 10 including the encoder unit 40 described above. The controller 300 includes a line receiver 302 and a control unit 301.

  The line receiver 302 converts the differential signal output from the line driver 122 into an original signal. Then, this signal is input to the control unit 301.

  The control unit 301 includes a CPU (Central Processing Unit), a main storage unit, an auxiliary storage unit, and the like, and determines and recognizes the current position based on a signal from the line receiver 302 and controls the servo motor 20.

  The operation of the motor unit 10 configured as described above will be described with reference to FIG.

When the power of the actuator system including the motor unit 10 and the controller 300 is turned on, the detection unit 80 of the encoder unit 40 detects the main driving gear 50 based on the reflected light from the optical track 54 (absolute scale) of the main driving gear 50. It calculates the absolute position _{Z 0.} Further, the phase θ in one bit of the optical track 54 is calculated based on the reflected light from the optical track 53 (incremental scale). Based on the absolute position Z ₀ and the phase θ, the detection unit 80 calculates an absolute position Z with higher resolution than the absolute position Z ₀ . Then, the detection unit 80 outputs a signal corresponding to the absolute position Z to the rotation speed calculation unit 110 and the output unit 120.

Similarly to the detection unit 80, the detection units 90 and 100 also have absolute positions α ₀ and β _{0 of the} driven gears 60 and 70 based on the reflected light from the optical tracks 64 and 74 (absolute scale) of the driven gears 60 and 70. Is output. Further, based on the reflected light from the optical tracks 63 and 73 (incremental scale), the phase within one bit of the optical tracks 64 and 74 of the driven gears 60 and 70 is calculated. Based on these absolute positions α ₀ and β ₀ and the phase, the detection units 90 and 100 calculate absolute positions α and β with higher resolution than the absolute positions α ₀ and β ₀ . Then, the detection units 90 and 100 output signals corresponding to the absolute positions α and β to the rotation speed calculation unit 110.

  The rotation speed calculation unit 110 calculates the number of teeth of each of the main driving gear 50 and the driven gears 60 and 70 based on the signals corresponding to the absolute positions Z, α, and β from the detection units 80, 90, and 100. From the combination, the rotational speed R of the shaft 30 is calculated. Then, the rotation speed calculation unit 110 outputs a signal corresponding to the rotation speed R to the output unit 120.

  The output unit 120 outputs a signal corresponding to the absolute position Z and a signal corresponding to the rotation speed R to the controller 300 after the power is turned on or at the time of resetting, and thereafter, the A phase signal of the main gear 50 is switched by switching the multiplexer 121. The B phase signal continues to be output to the controller 300.

  Based on the signal corresponding to the absolute position Z from the encoder unit 40 and the signal corresponding to the rotational speed R, the controller 300 converts the absolute position Z and rotational speed R of the main driving gear 50 into the absolute position Z and rotational speed of the shaft 30. The initial value of R is stored, and based on the A-phase signal and B-phase signal of the main driving gear 50, the current position is updated by counting up and down to the initial value.

  When the absolute position Z and the rotation speed R are stored, the controller 300 causes a current to flow through the coil of the stator 23 of the servo motor 20. And the coil which sends an electric current is switched. As a result, the coil is excited and a repulsive force or attractive force is generated between the stator 23 and the rotor 22, and as a result, the shaft 30 rotates together with the stator 23.

  When the shaft 30 rotates, the main driving gear 50 rotates with the shaft 30. Further, due to the meshing with the main driving gear 50, the driven gear 60 and the driven gear 70 also rotate in the rotation direction opposite to the rotation direction of the main driving gear 50.

  When the rotation speed of the shaft 30 is constant, the light emitted from the LED light emitting unit 82 of the detection unit 80 is reflected by the optical track 53 (incremental scale) while increasing or decreasing its reflection intensity. The detection unit 80 outputs an A phase signal and a B phase signal corresponding to the intensity of the light reflected by the optical track 53 to the controller 300. The value of the A phase signal changes from the high level to the low level every time the period T elapses. Further, the B phase signal advances by a period of T / 4 with respect to the A phase signal, and changes from a high level to a low level every time the period T elapses.

  The controller 300 counts the pulses of the A phase signal or the B phase signal with respect to the absolute position Z of the shaft 30 and the initial value of the rotation speed R. From this count, the absolute position Z of the rotating shaft 30 and the current value of the rotational speed R are obtained. The controller 300 controls the servo motor 20 based on the absolute position Z and the current value of the rotation speed R.

  Further, even when separately provided initial value resetting means is executed, the controller 300 stores the initial values of the absolute position Z and the rotational speed R of the shaft 30. Then, the pulses of the A-phase signal and the B-phase signal are counted up and down, and the current values of the absolute position Z and the rotation speed R of the rotating shaft 30 are obtained by this count. The controller 300 controls the servo motor 20 based on the absolute position Z and the current value of the rotation speed R.

  As described above, the encoder unit 40 according to the present embodiment includes the optical track 53, which is formed on the main driving gear 50 and the first driven gear 60 and the second driven gear 70 that are meshed with the main driving gear 50. Light from each of 54, 63, 64, 73 and 74 is detected, and thereby the absolute position Z (rotation angle) of the rotation speed R of the shaft 30 is determined. Accordingly, since both the driven gears 60 and 70 are directly meshed with the main driving gear 50, it is possible to prevent erroneous detection due to accumulation of gear backlash and the like, and to reduce the size of the encoder unit 40 and the like.

  In addition, since there is no accumulation of gear backlash compared to a conventional encoder unit in which the driven gear is connected in series, the gear of the conventional encoder unit having the same rotational speed detection range, The gear of the encoder unit 40 does not need to be formed so precisely, and as a result, the manufacturing cost can be reduced.

  Further, since the rotational speed R can be detected only by the main driving gear 50 and the two driven gears 60 and 70, a battery and a memory can be dispensed with.

  Further, in the present embodiment, the rotational speed calculator 111 is a timing at which the number of teeth of the main driving gear 50 is switched to the next number of teeth based on the absolute position Z having a resolution finer than the number of teeth of the main driving gear 50. The number of teeth of each of the driven gears 60 and 70 is switched in accordance with this timing. Thereby, even if a gear with a large backlash is used, there is no error in reading the number of teeth number, and high reliability can be obtained.

  In the present embodiment, the driven gear 60 and the driven gear 70 are directly meshed with the main driving gear 50, so that the number of gears can be greatly reduced, and the thickness (dimension in the X-axis direction) of the encoder unit 40 is reduced. As a result, the motor unit 10 can be reduced in size.

  In addition, the encoder unit 40 of the present embodiment includes the LED light emitting unit 82, the LED light emitting units of the detection units 90 and 100, and the optical detectors 83, 84, 93, 94, 103, and 104 on the same encoder substrate 41. Is a reflective optical encoder. Therefore, the thickness of the encoder unit 40 can be reduced, and as a result, the motor unit 10 can be reduced in size and cost.

  In the present embodiment, the main driving gear 50 used for outputting the A-phase signal and the B-phase signal is formed so that the diameter thereof is larger than that of the driven gears 60 and 70, and is simply the number of teeth number. The driven gears 60 and 70 used for this calculation are formed so that the diameter thereof is smaller than that of the main driving gear 50. Thereby, the size (dimension in the Y-axis direction and the Z-axis direction) of the encoder unit 40 can be reduced while forming the optical tracks 53 and 54 that require high resolution with a large diameter. As a result, the motor unit 10 can be reduced in size.

  Further, in the present embodiment, the absolute position calculator 86 selects only the output of the sensor element that has detected stable reflected light from the 512 CMOS image sensor elements of the optical detector 84. Thereby, the absolute position Z with high reliability can be calculated.

  As mentioned above, although embodiment of this invention was described, this invention is not limited by the said embodiment etc.

  In the above embodiment, the encoder unit 40 includes the two driven gears 60 and 70, but may include three driven gears. For example, when a third driven gear having 25 teeth is added, the total number of combinations of the respective tooth number numbers is 565,800 (565,800 = 41 × 24 × 23 × 25), and the encoder unit 40 can be discriminated up to 13,800 rotations (13,800 = 565, 800/41). Therefore, the position of the slider 201 within the stroke range of 138 m (138,000 = 13,800 × 10) can be determined. It is also possible to provide four or more driven gears.

  In the above embodiment, the number of teeth of the tooth portion 51 of the main gear 50 (41), the number of teeth of the tooth portion 61 of the driven gear 60 (24), and the number of teeth of the tooth portion 61 of the driven gear 70 (23). The book) is formed so as to have a prime relationship with each other. However, the present invention is not limited to this, and the number of teeth may not be in a prime relationship. However, when the relationship is not a prime relationship, the same combination of the number of teeth at the same rotation speed increases, and the corresponding conversion table becomes larger.

  In this embodiment, the controller 300 stores the initial values of the absolute position Z and the rotational speed R of the shaft 30 when the power of the actuator system is turned on and when the initial value resetting means is executed. Yes. Then, the pulses of the A phase signal or the B phase signal are counted, and the current value of the absolute position Z and the rotational speed R of the rotating shaft 30 is obtained by this count. However, the present invention is not limited to this, and the initial value of the absolute position Z and the rotational speed R of the shaft 30 may be stored at regular time intervals. It is also possible to always store the absolute position Z of the shaft 30 and the initial value of the rotational speed R.

  Further, in the present embodiment, a signal obtained by combining the signal corresponding to the absolute position Z and the signal corresponding to the rotation speed R, and the signal obtained by combining the A phase signal and the B phase signal from the line driver 122. Are output as parallel signals. However, the present invention is not limited to this and may be output as a serial signal.

  Further, as shown in FIG. 9, the detection unit 80 of the above embodiment directly outputs the A-phase signal and the B-phase signal from the optical detector 83 to the output unit 120. However, the present invention is not limited to this, and as shown in FIG. 12, a divider 88 (interpolator) may be arranged to output the A phase signal and the B phase signal to the output unit 120 via the divider 88. Good. In this case, the resolution of the A phase signal and the B phase signal can be improved.

In the present embodiment, the absolute position calculators 86, 96, and 106 indicate the correspondence relationship between the combination of output signals of the sensor elements stored in the storage unit and the absolute positions Z ₀ , α ₀ , β _0. With reference to the table, the absolute positions Z ₀ , α ₀ , β ₀ are calculated from the output signals of the selected sensor elements of the optical detectors 84, 94, 104. However, the present invention is not limited to this, and the absolute positions Z ₀ , α ₀ , β ₀ may be calculated using a shift register (LFSR).

  In the present embodiment, the servo motor 20 is used, but it goes without saying that a pulse motor may be used instead.

  In the present embodiment, the optical detection method is used, but it goes without saying that the same function can be configured by a capacitance type or a magnetic type.

  Various embodiments and modifications can be made to the present invention without departing from the broad spirit and scope of the present invention. The above-described embodiments are for explaining the present invention, and do not limit the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Motor unit 20 Servo motor 21 Housing 21a Notch part 21b Attachment part 21c, 21d Opening 22 Rotor 23 Stator 24a, 24b Bearing 30 Shaft (rotary body)
31 Small diameter part 40 Encoder unit (encoder)
41 Encoder board 42 Casing 43 Encoder base 44 Bearing 46, 47 Shaft 46a, 47a Small diameter part 50 Driving gear 51, 61, 71 Tooth part 52, 62, 72 Opening 53 Optical track (fourth optical track)
53a, 54a High reflectivity region 53b, 54b Low reflectivity region 54 Optical track (first optical track)
60 driven gear (first driven gear)
63, 73 Optical track 64 Optical track (second optical track)
70 driven gear (second driven gear)
74 Optical track (third optical track)
80, 90, 100 detection unit (light detection means)
81 Detection unit body 82 LED light emitting unit 83 Optical detector (second detection unit)
84 Optical detector (first detector)
85 Phase calculator 86 Absolute position calculator (first calculation means)
87 Correction calculator (first calculation means)
88 Dividers 93, 94, 103, 104 Optical detector 95 Phase calculator 96 Absolute position calculator (second calculation means)
97 Correction calculator (second calculation means)
105 Phase calculator 106 Absolute position calculator (third calculation means)
107 Correction calculator (third calculation means)
110 Rotational speed calculation unit 111 Rotational speed calculator (fourth calculation means)
DESCRIPTION OF SYMBOLS 120 Output unit 121 Multiplexer 122 Line driver 200 Actuator 201 Slider 202 Cable 300 Controller 301 Control part 302 Line receiver

Claims (7)

A main driving gear formed with a first optical track having a pattern that rotates together with a rotating body and indicates a rotation angle;
A first driven gear which is arranged so as to mesh with the main driving gear, rotates by transmitting the rotation of the rotating body via the main driving gear, and has a second optical track formed of a pattern indicating a rotation angle; ,
A second driven gear disposed so as to mesh with the main driving gear, and rotated by transmitting the rotation of the rotating body via the main driving gear, and formed with a third optical track having a pattern indicating a rotation angle; ,
Comprising at least
To the teeth of the main driving gear, the first driven gear, and the second driven gear, tooth number numbers for identifying the respective teeth are given,
The first optical track, the second optical track, and the third optical track are irradiated with light, and the reflected light reflected by the first optical track, the second optical track, and the third optical track is reflected. received light, by outputting a signal corresponding to the intensity of the reflected light, and a light detecting means for detecting at least said first optical track, said second optical track, and light from the third optical track,
First calculating means for calculating a rotation angle of the rotating body and the main driving gear based on a signal corresponding to the intensity of the reflected light reflected by the first optical track;
Second computing means for computing a rotation angle of the first driven gear based on a signal corresponding to the intensity of the reflected light reflected by the second optical track;
Third computing means for computing a rotation angle of the second driven gear based on a signal corresponding to the intensity of the reflected light reflected by the third optical track;
Based on the rotation angle of each of the main driving gear, the first driven gear, and the second driven gear, the number of teeth of the tooth at a predetermined position is calculated, and based on the combination of the number of teeth Fourth calculation means for calculating the number of rotations of the rotating body;
Equipped with a,
The fourth calculating means determines the timing at which the number of teeth of the main gear changes to the next number of teeth, and adjusts the teeth of the first driven gear and the second driven gear according to the timing. An encoder characterized by switching several numbers . The main driving teeth of the gear, encoder according to claim 1, characterized in that more than the number of teeth of the first driven gear and the second driven gear. Said first optical track, said second optical track, and the third optical track, that the high reflectance region and the low reflectance region, PN (Pseudo Noise, Pseudo Random Noise) are arranged on the basis of the code sequence the encoder according to claim 1 or 2, characterized in that it is constituted by. The main gear is formed with a fourth optical track configured by alternately arranging high reflectance regions and low reflectance regions at equal intervals,
The light detecting means irradiates the fourth optical track of the rotating main driving gear with light, receives reflected light reflected by the fourth optical track, and has a period of 1 according to the intensity of the reflected light. The encoder according to claim 3 , wherein two signals whose phases are different from each other by / 4 are output. The light detection means has a plurality of sensor elements for detecting light from the first optical track,
The first computing means is in the vicinity of the boundary between the high reflectance region and the low reflectance region of the first optical track based on the two signals whose phases are different from each other by ¼ of the period. The output of the sensor element other than the output of the sensor element that has detected the reflected light is selected, and the rotation angle of the rotating body and the main driving gear is determined based on the signal output from the selected sensor element. The encoder according to claim 4 , wherein the calculation is performed. A shaft,
A rotor provided on the shaft;
A stator that rotates the shaft together with the rotor by electromagnetic interaction with the rotor;
The encoder according to any one of claims 1 to 5, which detects rotation of the shaft;
A motor unit comprising: A motor unit according to claim 6 ;
Control means for controlling the motor unit based on the detection result of the encoder;
An actuator system comprising:

Images