Stepping motor control device, movement, timepiece, and stepping motor control method

Abstract

The present application simplifies the configuration of a detection circuit of a position of a pointer. A stepping motor control device is provided with: a driving section which is a driving circuit of a stepping motor having a rotor and a coil, and is provided with a first driving circuit which supplies a first current and a second driving circuit which supplies a second current; a control section which outputs a driving pulse for stepping rotation of the rotor by one revolution each time and a wobble pulse for wobbling the rotor to the driving section; a gear train which includes a load gear having a load tooth different from other teeth and a number of rotations of the rotor in one revolution is an odd number, and which transmits a rotational force from the rotor to a pointer; a voltage detection section which detects an induced voltage generated at one of first and second end portions of the coil in a case where the rotor vibrates; and a determination section which determines a mechanical load received by the rotor due to contact of the load tooth of the load gear and a tooth engaged with the load gear based on a result detected by the voltage detection section.

Description

Technical Field

[0001] This invention relates to a stepper motor control device, a movement, a watch, and a stepper motor control method. Background Technology

[0002] Previously, a technique was proposed to detect the rotational position of a gear by detecting the change in rotational load when a gear with elastically deformable teeth rotates as a change in the induced voltage generated in the drive coil of a stepper motor (for example, see Patent Document 1).

[0003] Prior art literature Patent documents Patent document 1: Japanese Patent Application Publication No. 2019-124681. Summary of the Invention

[0004] The problem that the invention aims to solve Based on prior art as described in Patent Document 1, the following problem arises: if the change in rotational load of the gear is to be detected accurately, the configuration of the detection circuit sometimes becomes complex.

[0005] The present invention was made in view of this situation, and its purpose is to simplify the configuration of the pointer position detection circuit.

[0006] Solution for solving the problem (1) A stepper motor control device according to one aspect of the present invention includes: a drive unit, which is a circuit for driving a stepper motor having a rotor that rotates a pointer and a coil that generates magnetic flux for rotating the rotor, and a first drive circuit that supplies a first current flowing in a direction from a first end to a second end of the coil and a second drive circuit that supplies a second current flowing in a direction from the second end to the first end; a control unit that outputs a drive pulse for rotating the rotor in half-turn increments and an oscillation pulse for oscillating the rotor to the drive unit; a gear train that includes a load gear having a load tooth with a rotational load different from the other teeth and having an odd number of rotation steps for the rotor when rotating one revolution, and transmits rotational force from the rotor to the pointer; a voltage detection unit that detects an induced voltage generated at one end of the first end and the second end of the coil when the rotor vibrates; and a determination unit that determines, based on the result detected by the voltage detection unit, the mechanical load on the rotor caused by contact between the load tooth of the load gear and the tooth meshing with the load gear.

[0007] (2) In a stepper motor control device according to one aspect of the present invention, the aforementioned gear train includes: a first wheel that rotates at an angular velocity consistent with the angular velocity of the aforementioned pointer; a second wheel that has a pinion gear meshing with the gear of the aforementioned first wheel and the aforementioned load gear; and a third wheel that has a pinion gear meshing with the aforementioned load gear of the aforementioned second wheel and a gear meshing with the aforementioned rotor.

[0008] (3) In one embodiment of the present invention, the number of steps of the aforementioned rotor rotating once in the second wheel is odd.

[0009] (4) In one embodiment of the present invention, the number of teeth of the second wheel is odd.

[0010] (5) In a stepper motor control device according to one aspect of the present invention, the gear of the first wheel has a load tooth with a rotational load different from the other teeth, and the determination part determines a first load as the mechanical load on the rotor caused by the contact between the pinion of the second wheel and the load tooth of the first wheel, and a second load as the mechanical load on the rotor caused by the contact between the pinion of the third wheel and the load tooth of the second wheel.

[0011] (6) In a stepper motor control device according to one aspect of the present invention, the stepper motor includes a plurality of the aforementioned coils, and the drive unit includes a first drive circuit and a second drive circuit corresponding to the plurality of the aforementioned coils respectively.

[0012] (7) In a stepper motor control device according to one aspect of the present invention, the determination unit determines the timing at which the induced voltage should be detected by interpolating the result detected by the voltage detection unit based on the detection cycle of the previously detected induced voltage.

[0013] (8) A stepper motor control device according to one aspect of the present invention includes: a drive unit having circuitry for driving a stepper motor having a rotor that rotates a pointer and a coil that generates magnetic flux for rotating the rotor; a control unit that outputs drive pulses for rotating the rotor and oscillation pulses for oscillating the rotor to the drive unit; a gear train including a load gear having load teeth that have a rotational load different from other teeth, for transmitting rotational force from the rotor to the pointer; a voltage detection unit that detects the induced voltage generated in the coil when the rotor vibrates; and a determination unit that, based on the result detected by the voltage detection unit, determines the mechanical load on the rotor caused by the contact between the load teeth of the load gear and the teeth of other gears meshing with the load gear, and determines the timing at which the mechanical load should be detected by interpolating the result detected by the voltage detection unit based on the detection cycle of the previously detected mechanical load.

[0014] (9) One embodiment of the present invention includes the aforementioned stepper motor control device and the aforementioned stepper motor.

[0015] (10) A watch according to one aspect of the present invention has the above-described movement.

[0016] (11) A stepper motor control method according to one aspect of the present invention is directed to a drive unit that drives a stepper motor having a rotor that rotates a pointer and a coil that generates magnetic flux for rotating the rotor, and has a first drive circuit that supplies a first current flowing in the direction from the first end to the second end of the coil and a second drive circuit that supplies a second current flowing in the direction from the second end to the first end. The drive unit outputs a drive pulse for rotating the rotor in half a revolution at a time and an oscillation pulse for oscillating the rotor. The drive unit detects the induced voltage generated at the first end of the coil in the induced voltage generated in the coil when the rotor vibrates. Based on the detection result of the induced voltage, the drive unit determines that the mechanical load on the rotor is caused by the contact between the load teeth of the load gear, which has a load teeth with a different rotational load than the other teeth and the number of rotation steps of the rotor when rotating one revolution, and the teeth of the other gears meshing with the load gear.

[0017] (12) A stepper motor control method according to one aspect of the present invention outputs a drive pulse for rotating the rotor and an oscillation pulse for oscillating the rotor to a drive unit having a circuit that drives a stepper motor having a rotor that rotates a pointer and a coil that generates magnetic flux for rotating the rotor. The method detects the induced voltage generated in the coil when the rotor vibrates. Based on the detection result of the induced voltage, it determines the mechanical load on the rotor caused by the contact between the load teeth of the load gear and the teeth of other gears meshing with the load gear. The method determines the timing at which the mechanical load should be detected by interpolating the detection result of the induced voltage based on the detection cycle of the previously detected mechanical load.

[0018] The effects of the invention According to the present invention, the configuration of the pointer position detection circuit can be simplified. Attached Figure Description

[0019] Figure 1 This is an external view of the clock according to the first embodiment.

[0020] Figure 2 This is a top view of the movement's face side according to the first embodiment.

[0021] Figure 3 This is a diagram illustrating an example of the load gear according to the first embodiment.

[0022] Figure 4 This is a diagram illustrating an example of the functional configuration of the clock according to the first embodiment.

[0023] Figure 5 This is a diagram illustrating an example of the configuration of the pointer driving unit according to the first embodiment.

[0024] Figure 6 This is a diagram illustrating an example of the oscillating pulse and drive pulse in the first embodiment.

[0025] Figure 7 This is a diagram illustrating an example of vibration in the first embodiment when the loaded tooth meshes with the pinion and when the standard tooth meshes with the pinion.

[0026] Figure 8 This is a flowchart illustrating an example of the operation of the stepper motor control device in the first embodiment.

[0027] Figure 9 This is a diagram illustrating an example of the specific configuration of the stepper motor control device according to this embodiment.

[0028] Figure 10This is a diagram illustrating an example of the specific configuration of the stepper motor control device in a modified example.

[0029] Figure 11 This is a diagram illustrating an example of the functional configuration of the clock according to the second embodiment.

[0030] Figure 12 This is a diagram illustrating an example of the load detection results in this embodiment.

[0031] Figure 13 This is a diagram illustrating an example of the specific configuration of a stepper motor control device based on a comparative example.

[0032] Figure 14 This is a diagram illustrating an example of the timing of load variations based on a comparative example.

[0033] Figure 15 This is a diagram illustrating an example of the relationship between the rotor assembly method and the timing of load variations, based on a comparative example.

[0034] Figure 16 This is a diagram showing an example of the specific configuration of a stepper motor control device in the case of a 2-coil motor according to the comparative example. Detailed Implementation

[0035] Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. Furthermore, in the following description, components having the same or similar functions will be given the same reference numerals. Also, repeated descriptions of those components will sometimes be omitted.

[0036] [First Implementation] First, an overview of the technique for detecting the rotational position of a gear by means of an induced voltage generated in the drive coil of a stepper motor will be given. Next, a technique for simplifying the circuit for detecting the induced voltage generated in the drive coil will be explained.

[0037] [Gear rotation position detection] Generally speaking, the mechanical component that includes the drive mechanism of a watch is called a "movement." A watch is considered "finished" when the dial and hands are mounted on the movement and placed inside the watch case. The side of the main plate that forms the watch's base, where the glass of the watch case is located (i.e., the side where the dial is located), is called the "back side" of the movement. Conversely, the side of the main plate that houses the back cover of the watch case (i.e., the side opposite to the dial) is called the "face side" of the movement.

[0038] Figure 1 This is an external view of the clock according to the first embodiment.

[0039] like Figure 1As shown in the figure, the finished watch 1 of this embodiment has a movement 4 (watch movement), a dial 5 with scales, an hour hand 6 (hand), a minute hand 7 and a second hand 8 inside a watch case 2 composed of a case back cover (not shown) and a glass 3.

[0040] Figure 2 This is a top view of the movement's face side according to the first embodiment.

[0041] like Figure 2 As shown, the movement 4 includes a main board 11, a first motor 20A, a second motor 20B, a first wheel assembly 30, and a second wheel assembly 50. The main board 11 constitutes the base plate of the movement 4.

[0042] [The structure of the gear train] like Figure 2 As shown, the first motor 20A and the second motor 20B are stepper motors, each having a stator 21 and a rotor 22. Each of the first motor 20A and the second motor 20B rotates the rotor 22 by 180° in one step. The first motor 20A generates a clockwise rotation of 6 (see reference). Figure 1 The second motor 20B generates the power to rotate the minute hand 7 and the second hand 8 (both refer to the motor). Figure 1 The rotational power is generated by the rotors 22 of both the first motor 20A and the second motor 20B, which are equipped with small gears.

[0043] The first gear train 30 has a gear that rotates based on the rotation of the rotor 22 of the first motor 20A. The first gear train 30 is equipped with a gear that transmits the rotation of the rotor 22 of the first motor 20A to the clock hand 6 (see reference). Figure 1 ) ) the hour wheel train 31.

[0044] Furthermore, if the watch 1 has a 24-hour hand or a calendar function, the first gear train 30 may also have a calendar gear train that transmits the rotation of the rotor 22 of the first motor 20A to the date wheel of the 24-hour hand or calendar. Detailed description of the calendar gear train is omitted.

[0045] The hour hand gear train 31 has a third wheel 32, a second wheel 33, and a first wheel 34.

[0046] Round 3, 32 was defeated by the motherboard, 11 (refer to) Figure 2 It is rotatably supported. The third wheel 32 has a third gear 32a and a third pinion 32b. The third gear 32a meshes with the pinion of the rotor 22 of the first motor 20A.

[0047] The second gear 33 is rotatably supported by the main board 11. The second gear 33 has a second gear 33a and a second pinion 33b. The second gear 33a meshes with the third pinion 32b of the third gear 32. The second gear 33 is the driven gear relative to the third gear 32.

[0048] The first gear 34 is rotatably supported by the main board 11. The first gear 34 has a first gear 34a. The first gear 34a meshes with the second pinion 33b of the second gear 33. The first gear 34 is the driven gear relative to the second gear 33. An hour hand 6 is mounted on the first gear 34 (see reference). Figure 1 ).

[0049] like Figure 2 As shown, the second gear train 50 has gears that rotate based on the rotation of the rotor 22 of the second motor 20B. The second gear train 50 is equipped with gears that transmit the rotation of the rotor 22 of the second motor 20B to the second hand 8 and the minute hand 7 (both referred to in the diagram). Figure 1 The surface-side gear train 51 includes a first intermediate wheel 52, a second intermediate wheel 53, a third intermediate wheel 54, and a fourth intermediate wheel 55.

[0050] Furthermore, details regarding the second round of group 50 are omitted.

[0051] [Structure of the load-bearing gear] Figure 3 This is a diagram illustrating an example of the load gear according to the first embodiment.

[0052] like Figure 3 As shown in the diagram, the second wheel 33 has an elastic portion 65 and multiple teeth 60.

[0053] The plurality of teeth 60 includes a standard tooth 61 and a first load tooth 62A, which serves as a load tooth 62. The standard tooth 61 comprises all the teeth in the plurality of teeth 60 except for the first load tooth 62A. The standard tooth 61 is a tooth of a general gear, formed with an arcuate tooth shape, an involute tooth shape, a cycloidal tooth shape, or the like. The first load tooth 62A is one of the plurality of teeth 60 in the second gear 33. The first load tooth 62A is arranged on one side of the outer periphery of the second gear 33 in such a way that it does not contact the third gear pinion 32b at equal intervals when the second gear 33 rotates. The first load tooth 62A is formed so as to be elastically displaceable by being supported by an elastic part 65.

[0054] Each load tooth 62 is provided with an elastic portion 65. The elastic portion 65 is a cantilever beam formed with a load tooth 62 at its tip and capable of flexural deformation. The elastic portion 65 includes a first elastic portion 65A having a first load tooth 62A. The first elastic portion 65A is the portion formed between the first slit 67 and the second slit 68 of the second wheel 33. The first slit 67 extends radially inward from a tooth groove adjacent to the first load tooth 62A and then extends circumferentially to one side. The second slit 68 extends along the first slit 67 from another tooth groove adjacent to the first load tooth 62A. Thus, the first elastic portion 65A extends with a substantially constant width, allowing it to be elastically deformed in such a way that the first load tooth 62A at its tip is displaced in the radial direction.

[0055] Here, the first standard tooth 61A and the second standard tooth 61B among the multiple standard teeth 61 are defined as follows. The first standard tooth 61A is adjacent to the first load tooth 62A on the downstream side of the second wheel 33 in the forward rotation direction N (a predetermined rotation direction). The second standard tooth 61B is adjacent to the first load tooth 62A on the upstream side of the forward rotation direction N.

[0056] The spacing between the first load tooth 62A and the first standard tooth 61A is narrower than the spacing between the first load tooth 62A and the second standard tooth 61B. The width of the tooth groove between the first load tooth 62A and the first standard tooth 61A is smaller than the tooth thickness of the third pinion 32b. Furthermore, the width of the tooth groove between an adjacent pair of teeth 60 is the distance between a pair of teeth 60 on the pitch circle of the second gear 33. The tooth thickness of the tooth 60 is the thickness of the tooth 60 on the pitch circle of the second gear 33. Therefore, if a tooth of the third pinion 32b enters the tooth groove between the first load tooth 62A and the first standard tooth 61A, it contacts the first load tooth 62A. The width of the tooth groove between the first load tooth 62A and the second standard tooth 61B is greater than the tooth thickness of the third pinion 32b. Thus, the teeth of the third pinion 32b can enter the tooth groove between the first load tooth 62A and the second standard tooth 61B without contacting the first load tooth 62A.

[0057] Here, the function of the load tooth 62 will be explained. Furthermore, unless otherwise specified in the following description, the second gear 33 rotates in the forward direction N. The teeth of the third gear pinion 32b contact the teeth 60 of the second gear 33 from the upstream side in the forward direction N.

[0058] When tooth 60, engaged with the third pinion 32b, shifts to the first standard tooth 61A, the tooth of the third pinion 32b enters the tooth groove between the first standard tooth 61A and the first load tooth 62A. At this time, the tooth of the third pinion 32b contacts the first load tooth 62A before and after contacting the first standard tooth 61A, causing the first load tooth 62A to elastically displace, thereby widening the tooth groove between the first standard tooth 61A and the first load tooth 62A. As a result, energy loss occurs in the hour gear train 31 accompanied by the elastic displacement of the first load tooth 62A. Subsequently, if tooth 60, engaged with the third pinion 32b, shifts to the first load tooth 62A, the first load tooth 62A slowly returns to its initial position. Furthermore, when the tooth 60 engaged with the third pinion 32b shifts from the first load tooth 62A to the second standard tooth 61B, the tooth of the third pinion 32b completely separates from the first load tooth 62A in the tooth groove between the first load tooth 62A and the second standard tooth 61B, and the first load tooth 62A returns to its initial position.

[0059] In addition, see the following text for reference. Figure 7 This describes the details of the meshing between the pinion teeth and the load teeth.

[0060] As described above, when the first load tooth 62A of the second gear 33 contacts the third pinion 32b, energy loss occurs in the clock gear train 31. If energy loss occurs in the clock gear train 31, the load on the rotor 22 of the first motor 20A changes. Therefore, the load tooth 62 can impart a change in the load on the rotor 22. Thus, a load change only occurs when the rotor 22 rotates one step when the first load tooth 62A of the second gear 33 contacts the third pinion 32b. Furthermore, the change in load imparted by the load tooth 62 differs from the load when the standard tooth 61 contacts the third pinion 32b. Hereinafter, the load on the rotor 22 will sometimes be referred to as the rotational load.

[0061] Furthermore, the first wheel 34 has the same configuration as the second wheel 33. That is, the first wheel 34 has a standard tooth 61a (not shown) corresponding to the standard tooth 61 of the second wheel 33 and a load tooth 62a (not shown) corresponding to the load tooth 62 of the second wheel 33.

[0062] That is, the gear of the first gear 34 has a load tooth that has a different rotational load than the other teeth.

[0063] In the following description, the second gear 33 will also be referred to as the second load gear, and the first gear 34 will also be referred to as the first load gear.

[0064] [Functional Components of a Clock] Figure 4This diagram illustrates an example of the functional configuration of the clock according to the first embodiment. The functional configuration of clock 1 will be described with reference to this diagram. Clock 1 includes an oscillation circuit 101, a frequency division circuit 102, a control circuit 103, a determination circuit 104, a voltage detection circuit 105, a motor drive circuit 106, a stepper motor 107, a clock case 2, a movement 4, an hour hand 6, a minute hand 7, a second hand 8, and a date window 5a.

[0065] From now on, the oscillation circuit 101, frequency divider circuit 102, control circuit 103, determination circuit 104, voltage detection circuit 105, and motor drive circuit 106 will be collectively referred to as stepper motor control device 100. In addition, the stepper motor control device 100 and the stepper motor 107 will be referred to as pointer drive unit 110.

[0066] That is, the movement 4 is equipped with a stepper motor control device 100 and a stepper motor 107. In addition, the first motor 20A and the second motor 20B mentioned above are examples of the stepper motor 107.

[0067] The oscillation circuit 101 generates a signal with a predetermined frequency and outputs the generated signal to the frequency divider circuit 102. The frequency divider circuit 102 divides the signal input from the oscillation circuit 101 to generate a clock signal that serves as a timing reference, and outputs the generated clock signal to the control circuit 103. The control circuit 103 outputs control signals to various parts of the clock 1 based on the clock signal and other signals input from the frequency divider circuit 102, and controls the operation of each part of the clock 1.

[0068] The motor drive circuit 106 obtains a control signal from the control circuit 103 and drives the stepper motor 107 based on the obtained control signal. When the obtained control signal is a drive pulse, the stepper motor 107 is driven by the motor drive circuit 106, causing the hour hand 6, minute hand 7, and second hand 8 to rotate via the gear train. When the obtained control signal is an oscillation pulse, the stepper motor 107 is driven by the motor drive circuit 106, causing the rotor to oscillate.

[0069] When the rotor of the stepper motor 107 vibrates (oscillates), the voltage detection circuit 105 detects the induced voltage generated in the coil. The voltage detection circuit 105 outputs the detected induced voltage to the determination circuit 104.

[0070] The determination circuit 104 determines the mechanical load on the rotor of the stepper motor 107 based on the value of the induced voltage detected by the voltage detection circuit 105. For example, the determination circuit 104 determines the mechanical load on the rotor based on whether the voltage value detected by the voltage detection circuit 105 exceeds a predetermined threshold.

[0071] [Structure of the pointer driver] Figure 5 This is a diagram showing an example of the configuration of the pointer drive unit 110 according to the first embodiment.

[0072] The stepper motor 107 includes a stator 201, a rotor 202, a through hole 203 for receiving the rotor, an inner slot 204, an inner slot 205, an outer slot 206, an outer slot 207, a magnetic core 208, and a coil 209. Hereinafter, the through hole 203 for receiving the rotor will also be referred to as a through hole for the rotor.

[0073] The magnetic core 208 is a component made of magnetic material and is coupled to both ends of the stator 201. A coil 209 is wound around the magnetic core 208, with one end connected to terminal OUT1 and the other end connected to terminal OUT2. The coil 209 generates magnetic flux by driving a current i. The stator 201 is also a component made of magnetic material. The stator 201 imparts the magnetic flux generated by the coil 209 to the rotor 202.

[0074] The rotor 202 is cylindrical and is inserted into the rotor receiving through-hole 203 formed in the stator 201 in a rotatable state. That is, the stepper motor 107 includes a stator 201 with a rotor receiving through-hole 203, a rotor 202 rotatably disposed within the rotor receiving through-hole 203, and a coil 209 provided in the stator 201. Furthermore, the rotor 202 has N poles and S poles due to magnetization. In the following description, the axis of the rotor 202 from the S pole to the N pole will be referred to as the magnetic pole axis A, and the direction of the magnetic pole axis A from the S pole to the N pole will be referred to as the positive direction of the magnetic pole axis A (or simply the direction of the magnetic pole axis A).

[0075] The rotor 202 rotates the pointer clockwise via the gear train by rotating in the forward direction, and rotates the pointer counterclockwise via the gear train by rotating in the reverse direction. That is, the rotor 202 causes the pointer to rotate clockwise in the forward direction and counterclockwise in the opposite direction to the forward direction.

[0076] Inner slots 204 and 205 are cuts formed in the wall of the through hole 203 for accommodating the rotor, determining the stopping position of the rotor 202 relative to the stator 201. That is, for example, when the coil 209 is not energized, the rotor 202 is stationary at a position where the magnetic pole axis is orthogonal to the line segment connecting the inner slots 204 and 205.

[0077] Outer slots 206 and 207 are cutouts formed on the inner and outer sides of the bent stator 201, respectively. A saturable portion 210 is formed between the outer slot 206 and the through hole 203 for rotor housing, and a saturable portion 211 is formed between the outer slot 207 and the through hole 203 for rotor housing. The saturable portions 210 and 211 are such that they will not become magnetically saturated due to the magnetic flux of the rotor 202, but will become magnetically saturated and have increased magnetic reluctance when the coil 209 is energized.

[0078] [Stepper motor drive] The motor drive circuit 106 generates a drive current i by applying a drive pulse between the terminals (terminal OUT1 and terminal OUT2) of the coil 209.

[0079] The stepper motor control device 100 reverses the direction of the drive current i supplied to the coil 209 according to the direction of the magnetic pole axis A at the stop position of the rotor 202, thereby causing the rotor 202 to rotate in a certain direction (e.g., the forward direction).

[0080] As an example, the drive in the forward direction will be explained. If the stepper motor control device 100 supplies a drive pulse between the first terminal OUT1 and the second terminal OUT2 of the coil 209, magnetic flux is generated in the stator 201. As a result, the saturable portions 210 and 211 saturate and the magnetic reluctance increases. Subsequently, due to the interaction between the magnetic poles generated in the stator 201 and the magnetic poles of the rotor 202, the rotor 202 rotates counterclockwise by 180 degrees and comes to a stable stop. With this approximately 180-degree rotation, the hand of the clock 1 can move by a predetermined amount of a scale mark. Sometimes, this predetermined amount of movement is referred to as one step. A gear train with an appropriate reduction ratio is appropriately arranged between the rotor 202 and the hand to achieve this predetermined amount of movement.

[0081] When rotor 202 is in Figure 5 In the state shown, if the stepper motor control device 100 supplies a drive pulse between the first terminal OUT1 and the second terminal OUT2 of the coil 209, current flows through the coil 209. In this example, when a pulse is applied where the first terminal OUT1 is at a high potential and the second terminal OUT2 is at a low potential (hereinafter referred to as the positive direction), the current flows in the direction of current i. If current flows through the coil 209, a magnetic flux is generated in the stator 201. Due to this magnetic flux, the rotor 202 rotates counterclockwise by approximately 180 degrees and comes to a stable stop.

[0082] When rotor 202 is in the slave position Figure 5When the rotor 202 rotates approximately 180 degrees from its initial state, and the stepper motor control device 100 applies a pulse where the first terminal OUT1 is at a low potential and the second terminal OUT2 is at a high potential (hereinafter referred to as the negative direction), a magnetic flux opposite to that applied in the positive direction is generated in the stator 201. As a result, the saturable portions 210 and 211 saturate first, and thereafter, due to the interaction between the magnetic poles generated in the stator 201 and the magnetic poles of the rotor 202, the rotor 202 rotates approximately 180 degrees counterclockwise and comes to a stable stop. By supplying signals of different polarities (alternating signals) to the coil 209 in this way, the rotor 202 rotates approximately 180 degrees counterclockwise each time.

[0083] [Oscillating pulse and driving pulse] Figure 6 This is a diagram illustrating an example of the oscillating pulse and drive pulse in the first embodiment. Figure 6 (A) is a timing diagram illustrating the timing of the applied oscillating pulse and drive pulse. Figure 6 (B) is a diagram used to illustrate the angle of rotor 202. Figure 6 In the description of (A), the horizontal axis shows the time, "Out1" shows the magnitude of the voltage applied to the first terminal OUT1 at each time, and "Out2" shows the magnitude of the voltage applied to the second terminal OUT2 at each time.

[0084] In addition, Figure 6 In the explanation of (B), Figure 5 The position of the magnetic pole axis A is defined as 0 degrees, and the angle of counterclockwise rotation of the magnetic pole axis A is defined as the positive rotation angle to describe the rotational position of the rotor 202. The control from time t11 to time t21 is to rotate the rotor 202 clockwise from 0 degrees to 180 degrees, and the control from time t21 to time t29 is to rotate the rotor 202 clockwise from 180 degrees to 0 degrees.

[0085] The control circuit 103 causes the rotor 202 to rotate by outputting drive pulses to the motor drive circuit 106, and causes the rotor 202 to oscillate by outputting oscillation pulses to the motor drive circuit 106. The oscillation pulses and drive pulses will be described below.

[0086] Between time t11 and time t12, the stepper motor control device 100 applies a positive pulse to terminal OUT2. If the positive pulse continues to be applied to terminal OUT2, the rotor 202 remains stationary at a position with a rotation of -45 degrees. If the stepper motor control device 100 stops applying the pulse at time t12, the rotor 202 is pulled back to the 0-degree position and remains stationary. Here, when the rotor 202 returns from the -45-degree position to the 0-degree position, it rotates counterclockwise at least once due to inertia until it reaches a position with a positive rotation angle, and then rotates clockwise until it reaches a position with a negative rotation angle. The rotor 202 repeats the counterclockwise and clockwise rotations. That is, the rotor 202 vibrates, and through vibration decay, it comes to rest at the 0-degree position.

[0087] Furthermore, the pulse applied between time t11 and time t12 is not intended to rotate the rotor 202 approximately 180 degrees, but rather to detect the vibration state of the rotor 202 by causing it to vibrate. Hereafter, the pulse intended to vibrate the rotor 202 will be distinguished from the usual drive pulses and referred to as an oscillating pulse.

[0088] Furthermore, the duration of the oscillating pulse application is only sufficient for the rotor 202 to vibrate; it is not necessary to apply the pulse until the rotor 202 comes to rest at a rotational position of -45 degrees.

[0089] Between time t12 and time t15, the stepper motor control device 100 determines the mechanical load on the rotor 202 caused by the application of the oscillation pulse. Specifically, the determination circuit 104 determines the mechanical load on the rotor 202 based on the voltage detected by the voltage detection circuit 105.

[0090] In addition to the magnitude of the voltage detected by the voltage detection circuit 105, the determination circuit 104 may also determine the mechanical load on the rotor 202 based on the timing of the voltage detection circuit 105 detecting a voltage value exceeding a predetermined value, instead of the magnitude of the voltage detected by the voltage detection circuit 105. For example, the determination circuit 104 may also determine the mechanical load on the rotor 202 based on whether the timing of the generation of the voltage value detected by the voltage detection circuit 105 is within a predetermined period.

[0091] Between time t15 and time t16, the stepper motor control device 100 applies a positive pulse to the first terminal OUT1. If the positive pulse continues to be applied to the first terminal OUT1, the rotor 202 remains stationary at a position rotated 135 degrees. If the stepper motor control device 100 stops applying the pulse at time t16, the rotor 202 is pulled to a position of 180 degrees and remains stationary. The pulse applied between time t15 and time t16 is a pulse used to rotate the rotor 202 approximately 180 degrees, and is therefore a drive pulse. The drive pulse is output by the control circuit 103. That is, after outputting the oscillation pulse, the control circuit 103 outputs the drive pulse after a predetermined period of time.

[0092] Furthermore, the duration of the applied drive pulse (pulse width of the drive pulse) is only sufficient for the rotor 202 to rotate 180 degrees; it is not necessary to apply the pulse until the rotor 202 is stationary at a rotational position of 135 degrees.

[0093] Furthermore, the timing of applying the drive pulse can also be determined based on the mechanical load determined by the determination circuit 104. In this case, the control circuit 103 controls the output timing of the drive pulse based on the mechanical load determined by the determination circuit 104.

[0094] Between time t21 and time t22, the stepper motor control device 100 applies a positive pulse, i.e., an oscillating pulse, to the first terminal OUT1. If the positive pulse continues to be applied to the first terminal OUT1, the rotor 202 remains stationary at a position rotated 135 degrees. If the stepper motor control device 100 stops applying the pulse at time t22, the rotor 202 is pulled back to a position of 180 degrees and remains stationary. Here, the rotor 202 vibrates as it returns from the 135-degree position to the 180-degree position, and comes to rest at the 180-degree position through vibration attenuation.

[0095] Between time t22 and time t25, the stepper motor control device 100 determines the mechanical load on the rotor 202 caused by the application of the oscillation pulse. Specifically, the determination circuit 104 determines the mechanical load on the rotor 202 based on the voltage detected by the voltage detection circuit 105.

[0096] Between time t25 and time t26, the stepper motor control device 100 applies a positive pulse, i.e., a drive pulse, to the second terminal OUT2. If the positive pulse continues to be applied to the second terminal OUT2, the rotor 202 remains stationary at a position rotated 315 degrees. If the stepper motor control device 100 stops applying the pulse at time t26, the rotor 202 is pulled to a position of 0 degrees and remains stationary.

[0097] That is, the control circuit 103 (control unit) outputs the drive pulse for making the rotor 22 rotate half a turn each time and the oscillation pulse for making the rotor 22 oscillate to the motor drive circuit 106 (drive unit).

[0098] Figure 7 This is a diagram illustrating an example of vibration in the first embodiment when the load tooth meshes with the pinion and when the standard tooth meshes with the pinion. The vibrations in the load tooth meshing with the pinion and when the standard tooth meshes with the pinion will be explained with reference to this diagram.

[0099] The upper part of the figure shows an example of standard gear meshing with a pinion, and the lower part shows an example of load gear meshing with a pinion. Specifically, an example is illustrated where the second gear 33, having load gear 62, meshes with the third gear pinion 32b. In the illustration, the second gear 33 is sometimes referred to simply as a gear (or second gear) and the third gear pinion 32b is sometimes referred to simply as a pinion (or first gear). The first gear is a gear that rotates based on the rotation of the rotor 202, and the second gear is a gear with load gear.

[0100] The left side of the diagram shows the meshing state of the gear and pinion. The right side of the diagram shows the timing of applying the oscillating pulse and the timing of generating the induced voltage.

[0101] First, an example from the previous section regarding the meshing of the standard gear 61 with the pinion will be explained. As shown in the diagram on the left side of the previous section, if the rotor 202, which drives the pinion, vibrates by applying an oscillating pulse, the pinion will vibrate due to the vibration of the rotor 202. The range of vibration that the rotor 202 can achieve varies depending on the size of the backlash between the gear and the pinion. When the standard gear 61 is meshing with the pinion, the backlash is large, and therefore the range of vibration that the rotor 202 can achieve is also wide.

[0102] As shown in the diagram on the right side of the upper section, an oscillating pulse is applied between times t31 and t32. The rotor 202 vibrates based on the applied oscillating pulse, generating an induced voltage between times t33 and t35. With the standard tooth 61 meshing with the pinion, the rotor 202 can vibrate over a wider range, thus generating a larger induced voltage. In one example shown in the diagram, a voltage v1 is generated at time t34. If voltage v1 is greater than a determination threshold, the determination circuit 104 determines that the pinion is not in contact with the load teeth of the gear.

[0103] Next, an example will be described in the following section regarding the case where the load tooth 62 meshes with the pinion. As shown in the diagram on the left side of the following section, if the rotor 202, which drives the pinion, vibrates by applying an oscillating pulse, the pinion will vibrate due to the vibration of the rotor 202. However, when the load tooth 62 meshes with the pinion, the clearance is small, and therefore the range of vibration that the rotor 202 can achieve is also narrow.

[0104] As shown in the diagram on the right side of the following section, an oscillating pulse is applied between time t41 and time t42. The rotor 202 vibrates based on the applied oscillating pulse, generating an induced voltage between time t43 and time t45. However, with the load teeth 62 meshing with the pinion, the range of vibration that the rotor 202 can achieve is narrow, thus the generated induced voltage is also smaller. In one example shown in the diagram, a voltage v2 is generated at time t44. Voltage v2 is smaller compared to voltage v1. Since voltage v1 is smaller than the determination threshold, the determination circuit 104 determines that the pinion is a mechanical load in contact with the load teeth of the gear.

[0105] Furthermore, when the pinion is engaged between the load tooth 62 and the first standard tooth 61A, the vibration decreases; conversely, when the pinion is engaged between the load tooth 62 and the second standard tooth 61B, the vibration increases. The pointer position can also be detected by comparing the vibrations of these two engagements with the vibration when the standard tooth 61 is engaged with the pinion.

[0106] Figure 8 This is a flowchart illustrating an example of the operation of the stepper motor control device 100 in the first embodiment. A series of operations of the stepper motor control device 100 will be described with reference to this diagram.

[0107] (Step S110) The control circuit 103 outputs the oscillation pulse to the motor drive circuit 106. The motor drive circuit 106 drives the stepper motor 107 based on the obtained oscillation pulse.

[0108] (Step S120) The voltage detection circuit 105 detects the induced voltage caused by the vibration of the rotor 202. The determination circuit 104 determines the mechanical load of the rotor 202 based on the value of the detected induced voltage or the timing of the detection of the induced voltage.

[0109] (Step S130) If a predetermined time has elapsed since the output swing pulse (Step S130; Yes), the control circuit 103 advances the process to step S140. If the predetermined time has not elapsed since the output swing pulse (Step S130; No), the voltage detection circuit 105 repeats step S120.

[0110] (Step S140) The control circuit 103 outputs a drive pulse to the motor drive circuit 106. The magnitude (voltage and time) of the drive pulse can be a predetermined value or a value based on the mechanical load of the rotor 202 determined in step S120.

[0111] [Regarding the reduction ratio of the gear train] Here, the reduction ratio of the gear train in this embodiment is compared with the reduction ratio of the gear train according to the comparative example.

[0112] (1) Reduction ratio of the gear train in this embodiment (an example) The number of teeth of the gears and the number of teeth of the pinion in the gear train (clock gear train 31) constituting this embodiment are as follows.

[0113] Number of teeth on the pinion of rotor 22: 8 The number of teeth on gear 32 of the third wheel: 40 The number of teeth on the pinion of the third gear (gear 32) is 10. The number of teeth on gear 33 in the second round: 45 The number of teeth on the pinion of gear 33 in the second round: 7 The number of teeth on gear 34 in the first round: 56 That is, regarding the second round 33, the number of teeth is odd.

[0114] Here, rotor 22 rotates 180 degrees in each step. That is, rotor 22 rotates 1 revolution in 2 steps.

[0115] The third wheel 32 rotates relative to the rotor 22 at a reduction ratio of 5. That is, for every 5 revolutions (i.e., 10 steps) of the rotor 22 of the first motor 20A, the third wheel 32 rotates once.

[0116] The second wheel 33 rotates relative to the third wheel 32 at a reduction ratio of 4.5. That is, for every 22.5 revolutions (i.e., 45 steps) that the rotor 22 of the first motor 20A rotates, the second wheel 33 rotates once.

[0117] The first wheel 34 rotates relative to the second wheel 33 at a reduction ratio of 8. That is, for every 180 revolutions (i.e., 360 steps) of the rotor 22 of the first motor 20A, the first wheel 34 rotates once.

[0118] In the gear reduction ratio of the above gear train, the fact that the second gear 33 rotates once for every 22.5 revolutions (i.e., 45 steps) of rotor 22 means that the number of rotation steps of rotor 22 when the second gear 33 rotates once is odd.

[0119] That is, the hour hand gear train 31 (gear train) includes a load gear with a load tooth that has a different rotational load than the other teeth and whose number of rotation steps of the rotor 22 is odd when it rotates 1 revolution, which transmits the rotational force from the rotor 22 to the hand.

[0120] The hour hand gear train 31 (gear train) includes: a first gear 34 that rotates at an angular velocity consistent with the angular velocity of the hand; a second gear 33 that has a pinion gear and a load gear that mesh with the gear of the first gear 34; and a third gear 32 that has a pinion gear that meshes with the load gear of the second gear 33 and a gear that meshes with the rotor 22.

[0121] (2) Reduction ratio of the gear train based on the comparative example (an example) The number of teeth on the gears and the number of teeth on the pinion of the gear train (clock gear train) based on the comparative example are as follows.

[0122] Number of teeth on the pinion of the rotor: 6 The number of teeth on the third gear: 36 The number of teeth on the pinion of the third gear: 12 The number of teeth on the second gear: 60 Number of teeth on the pinion of the second gear: 10 Number of teeth on the first gear: 60 This rotor, like rotor 22 in this embodiment, rotates 180 degrees in each step. That is, this rotor rotates one revolution in two steps.

[0123] The third wheel rotates relative to the rotor at a reduction ratio of 6. That is, the third wheel rotates once for every 6 revolutions (i.e., 12 steps) of the rotor.

[0124] The second wheel rotates at a reduction ratio of 5 relative to the third wheel. That is, the second wheel rotates once for every 30 revolutions (i.e., 60 steps) of the rotor.

[0125] The first wheel rotates at a reduction ratio of 6 relative to the second wheel. That is, the first wheel rotates once for every 180 revolutions (i.e., 360 steps) of the rotor.

[0126] In the gear train reduction ratio in this comparative example, the fact that the second gear rotates once for every 30 revolutions (i.e., 60 steps) of the rotor means that the number of rotation steps of the rotor when the second gear rotates once is an even number.

[0127] [The relationship between the direction of the rotor's magnetic poles and the rotational position of the load teeth] Here, the assembly direction of rotor 22 relative to the gear train (clockwise gear train 31) will be explained. Rotor 22 ( Figure 5 The rotor 202 shown is magnetized by two poles, N and S. The magnetic poles (N and S) of the rotor 202 are difficult to distinguish visually. Therefore, when the load tooth 62 of the second gear 33 meshes with the pinion of the third gear 32, a first direction is generated with the direction of the magnetic poles of the rotor 202 within the stator 201 as the first direction (e.g., ...). Figure 5The assembly is in the manner shown in the diagram (in the direction shown) and in the manner that it becomes the second direction (e.g., from the direction shown in the diagram). Figure 5 The assembly method shown is a rotation of 180 degrees in the direction indicated.

[0128] Furthermore, in the following description, the case in which the rotor 202 is assembled in the first direction as described above will be referred to as "assembly in the first direction" (or "surface mounting"), and the case in which the rotor 202 is assembled in the second direction as described above will be referred to as "assembly in the second direction" (or "back mounting").

[0129] [Construction of a voltage detection circuit] (1) Configuration of the voltage detection circuit in this embodiment Figure 9 This is a diagram illustrating an example of the specific configuration of the stepper motor control device 100 according to this embodiment.

[0130] The motor drive circuit 106 includes a first driver 1061 and a second driver 1062. The output terminal of the first driver 1061 is connected to one end of the coil 209. The output terminal of the second driver 1062 is connected to the other end of the coil 209. The first driver 1061 and the second driver 1062 output drive current to the coil 209 exclusively, thereby alternating the direction of the current flowing through the coil 209. This generates an alternating magnetic field in the stator 201, causing the rotor 202 to rotate in a predetermined direction.

[0131] That is, the motor drive circuit 106 (drive unit) is a circuit that drives a stepper motor (first motor 20A, second motor 20B) having a rotor 22 that rotates a pointer and a coil 209 that generates magnetic flux to rotate the rotor 22. In addition, the motor drive circuit 106 (drive unit) includes a first driver 1061 (first drive circuit) that supplies a first current flowing in the direction from the first end to the second end of the coil 209 and a second driver 1062 (second drive circuit) that supplies a second current flowing in the direction from the second end to the first end.

[0132] The voltage detection circuit 105 includes a comparator 1051, a voltage detection resistor 1052, and a voltage detection switch 1053.

[0133] A voltage sensing resistor 1052 is connected between the voltage sensing point 1054 and the voltage sensing switch 1053. The resistance of the voltage sensing resistor 1052 is relatively high. If current flows between the voltage sensing point 1054 and the voltage sensing switch 1053, a relatively large potential difference is generated across the voltage sensing resistor 1052. The voltage sensing point 1054 is located between the first driver 1061 and one end of the coil 209, indicating the potential at one end of the coil 209.

[0134] The voltage detection switch 1053 operates based on the control of the control circuit 103, switching between a state in which current flows through the voltage detection resistor 1052 (e.g., on state) and a state in which no current flows (e.g., high impedance state).

[0135] When the voltage detection switch 1053 is in the ON state, the comparator 1051 outputs a signal indicating whether the voltage at the voltage detection point 1054 exceeds a predetermined threshold voltage to the aforementioned determination circuit 104.

[0136] That is, the voltage detection circuit 105 (voltage detection unit) detects the induced voltage generated at one of the first and second ends of the coil 209 when the rotor 22 vibrates.

[0137] The determination circuit 104 (determination unit) determines the mechanical load on the rotor 22 caused by the contact between the load teeth of the load gear and the teeth meshing with the load gear based on the result detected by the voltage detection circuit 105 (voltage detection unit).

[0138] In addition, the determination circuit 104 (determination unit) may be configured to determine the first load as the mechanical load on the rotor 22 caused by the contact between the pinion of the second wheel 33 and the load tooth of the first wheel 34, and the second load as the mechanical load on the rotor 22 caused by the contact between the pinion of the third wheel 32 and the load tooth of the second wheel 33.

[0139] (2) Construction of the voltage detection circuit based on the comparative example Figure 13 This is a diagram illustrating an example of the specific configuration of a stepper motor control device 500 according to a comparative example.

[0140] The detection circuit according to the comparative example includes a control circuit 503, a determination circuit 504, a voltage detection circuit 505, and a motor drive circuit 506. Furthermore, correspondingly, the control circuit 503 has the same configuration as the control circuit 103 of this embodiment, the determination circuit 504 has the same configuration as the determination circuit 104 of this embodiment, and the motor drive circuit 506 has the same configuration as the motor drive circuit 106 of this embodiment, and their descriptions are omitted.

[0141] The voltage detection circuit 505 differs from the voltage detection circuit 105 of this embodiment in that it is configured to detect the voltages at two points, the first voltage detection point 5054A and the second voltage detection point 5054B. More specifically, the voltage detection circuit 505 includes a first comparator 5051A and a first voltage detection resistor 5052A, and detects the voltage at the first voltage detection point 5054A. Additionally, the voltage detection circuit 505 includes a second comparator 5051B and a second voltage detection resistor 5052B, and detects the voltage at the second voltage detection point 5054B.

[0142] That is, the voltage detection circuit 505 according to this comparative example is configured to detect the voltage across the two ends of the coil 209.

[0143] [Comparison of the voltage detection circuit in the comparative example with the voltage detection circuit in this embodiment] Figure 14 This is a diagram illustrating an example of the timing of load variations based on a comparative example.

[0144] In the configuration of the gear train in the comparative example described above, the second gear rotates once for every 60 steps of the rotor. Therefore, in any one of the 60 steps of the rotor, the load teeth of the second gear mesh with the pinion of the third gear, resulting in a load variation. For example, as shown in the figure, the first load is generated when the rotor has approximately 105-110 steps, and the second load is generated when the rotor has 0, 60, 120...360 steps.

[0145] As described above, the rotor can be assembled in the first direction (i.e., on the front side) or assembled in the second direction (i.e., on the back side).

[0146] When the rotor is assembled along the first direction, the second load will be detected only under polarity 0, and when the rotor is assembled along the second direction, the second load will be detected only under polarity 1.

[0147] Figure 15 This is a diagram illustrating an example of the relationship between the rotor assembly method and the timing of load variations, based on a comparative example.

[0148] Figure [A] shows the timing of the generation of the first load when the rotor is mounted on the front side. Figure [B] shows the timing of the generation of the first load when the rotor is mounted on the back side.

[0149] Furthermore, the timing of the generation of the first load is illustrated in the figure, but the timing of the generation of the second load is also different from that of the first load, depending on whether the rotor is mounted on the front side or the rotor is mounted on the back side.

[0150] Specifically, when the rotor is mounted on the front side and when the rotor is mounted on the back side, the polarity of the drive pulse that rotates the rotor at the location where the load change due to the load teeth of the second wheel occurs (i.e., the direction of the current flowing in the drive coil) is different. That is, when the rotor is mounted on the front side and when the rotor is mounted on the back side, the polarity of the voltage induced in the drive coil based on the load change due to the load teeth is different.

[0151] Therefore, in the configuration of the gear train in the comparative example described above, in order to detect the induced voltage caused by load variation due to the load teeth regardless of whether it is mounted on the front or back side, a circuit configuration capable of detecting two induced voltages with different polarities is required. Therefore, in the configuration of the gear train in the comparative example, a circuit configuration is adopted in which the first comparator 5051A and the second comparator 5051B described above detect these two induced voltages respectively.

[0152] That is, in the case of the gear train configuration of the comparative example, in order to detect the induced voltage caused by load changes due to load teeth, two comparators are required for each drive coil.

[0153] On the other hand, in the configuration of the gear train (clockwise gear train 31) of this embodiment, the second gear rotates once for every 45 steps of the rotor 202. Therefore, in any one of the 45 steps of the rotor 202, the load teeth of the second gear mesh with the pinion of the third gear, resulting in a load change. That is, in the configuration of the gear train (clockwise gear train 31) of this embodiment, a load change occurs for every odd number of steps of the rotor 202.

[0154] Therefore, whether the rotor 202 is mounted on the front side or the rotor 202 is mounted on the back side, the polarity of the voltage induced in the drive coil due to the load change caused by the load tooth 62 will change with each load change.

[0155] Therefore, in the configuration of the gear train (clock gear train 31) of this embodiment, regardless of whether the rotor is mounted on the front or back side, a load variation due to the load teeth occurs every 90 steps at the first voltage detection point 5054A. Therefore, it can be detected by only one comparator that detects the induced voltage of either polarity.

[0156] That is, in the case of the gear train (clock gear train 31) configuration of this embodiment, in order to detect the induced voltage caused by load changes due to load teeth, each drive coil can be equipped with one comparator (for example, comparator 1051).

[0157] Thus, according to the stepper motor control device 100 of this embodiment, only one comparator is needed for each drive coil. That is, compared with the comparative example, the stepper motor control device 100 of this embodiment can reduce one comparator for sensing voltage for each drive coil.

[0158] Therefore, the stepper motor control device 100 according to this embodiment can simplify the circuit configuration of the voltage detection circuit 105.

[0159] Furthermore, according to the stepper motor control device 100 of this embodiment, one comparator for sensing voltage can be reduced for each drive coil, thus further simplifying the circuit configuration of the voltage detection circuit 105 when multiple stepper motors are provided in one mechanism.

[0160] [Modification (in the case of a 2-coil motor)] In the stepper motor control device 100 of this embodiment described above, the case of a so-called single-coil motor in which either the first motor 20A or the second motor 20B has a single coil for a single rotor 22 has been described, but it is not limited thereto.

[0161] Specifically, the number of steps of rotor 22 per revolution of load gear can be odd as described above, or it can be a so-called 2-coil motor in which either the first motor 20A or the second motor 20B has 2 coils for each rotor 22.

[0162] That is, the stepper motor (first motor 20A, second motor 20B) of this modified example has a plurality of coils 209. In addition, the motor drive circuit 106 (drive unit) of this modified example has a set of first driver (first drive circuit) and second driver (second drive circuit) corresponding to the plurality of coils 209 respectively.

[0163] As described above, in the case of a single-coil motor, the induced voltage generated by the load variation of the load gear 62 is determined by the rotor's mounting angle and occurs at either the first or second end of the coil. That is, in the case of a two-coil motor, there are two terminals that generate the induced voltage. Therefore, in the comparative example where the number of steps of the rotor 22 per revolution of the load gear is even, two comparators are required in the single-coil motor for induced voltage detection.

[0164] In the case of a two-coil motor, the induced voltage generated by the load variation of the load teeth 62 is determined by the rotor's mounting angle and is generated at any one of the first end of the first coil, the second end of the first coil, the first end of the second coil, and the second end of the second coil. That is, in the case of a two-coil motor, there are four terminals that generate the induced voltage. Therefore, in the case of the two-coil motor in the comparative example, as follows, four comparators are required for induced voltage detection.

[0165] Figure 16 This is a diagram illustrating an example of the specific configuration of a stepper motor control device in the case of a two-coil motor according to a comparative example. In the case of a two-coil motor, the stepper motor control device 500a according to the comparative example includes a voltage detection circuit 505a and a motor drive circuit 506.

[0166] The motor drive circuit 506 in this variant has four (or two groups) drivers 5062a that drive the two coils 209A and 209B.

[0167] The voltage detection circuit 505a is configured to detect the voltage at four points: the first voltage detection point 5054A to the fourth voltage detection point 5054D. More specifically, the voltage detection circuit 505a includes a first comparator 5051A and a first voltage detection resistor 5052A, detecting the voltage at the first voltage detection point 5054A. The voltage detection circuit 505a includes a second comparator 5051B and a second voltage detection resistor 5052B, detecting the voltage at the second voltage detection point 5054B. The voltage detection circuit 505a includes a third comparator 5051C and a third voltage detection resistor 5052C, detecting the voltage at the third voltage detection point 5054C. Furthermore, the voltage detection circuit 505a includes a fourth comparator 5051D and a fourth voltage detection resistor 5052D, detecting the voltage at the fourth voltage detection point 5054D.

[0168] The voltage detection circuit 505a according to this comparative example is configured to detect the voltage across the two ends of coil 209A and the voltage across the two ends of coil 209B.

[0169] That is, the voltage detection circuit 505a according to this comparative example has 4 comparators.

[0170] When load detection is performed in forward rotation, comparator 5051A detects the induced voltage generated at voltage detection point 5054A after the oscillating pulse is output from driver 5062a. Comparator 5051B detects the induced voltage generated at voltage detection point 5054B after the oscillating pulse is output from driver 5061a. When load detection is performed in reverse rotation, comparator 5051D detects the induced voltage generated at voltage detection point 5054D after the oscillating pulse is output from driver 5061b. Comparator 5051C detects the induced voltage generated at voltage detection point 5054C after the oscillating pulse is output from driver 5062b.

[0171] Furthermore, the forward drive pulse following the output of the oscillation pulse from driver 5062a is output in the order of driver 5062a and driver 5062b. The forward drive pulse following the output of the oscillation pulse from driver 5061a is output in the order of driver 5061a and driver 5061b.

[0172] On the other hand, if the number of steps of rotor 22 rotating once per revolution of the load gear in the second wheel is odd, the number of comparators can be halved, as in the stepper motor control device 100 described above. Therefore, according to the stepper motor control device 100, in the case of a 2-coil motor, only 2 comparators are needed for induced voltage detection, which reduces the number of comparators by 2 compared to the comparison example.

[0173] Figure 10 This is a diagram illustrating an example of the specific configuration of the stepper motor control device in a modified example. The stepper motor control device 100a of this modified example includes a voltage detection circuit 105a.

[0174] The voltage detection circuit 105a is configured to detect the voltage at two points: a first voltage detection point 5054A and a second voltage detection point 5054B. More specifically, the voltage detection circuit 105a includes a first comparator 1051A and a first voltage detection resistor 1052A, and detects the voltage at the first voltage detection point 1054A. Additionally, the voltage detection circuit 105a includes a second comparator 1051B and a second voltage detection resistor 1052B, and detects the voltage at the second voltage detection point 1054B.

[0175] That is, the voltage detection circuit 105a can detect the voltage across the two ends of coil 209A and the voltage across the two ends of coil 209B using two comparators.

[0176] Based on the stepper motor control device 100 configured in this way, the circuit configuration of the voltage detection circuit 105 can be further simplified.

[0177] Furthermore, in the case of a 2-coil motor, it is possible to detect the induced voltage generated by the load variation of the load tooth 62 only when the rotor rotates forward (or only when the rotor rotates in reverse). With this configuration, even in the case of a 2-coil motor, if a comparator is provided for induced voltage detection, the induced voltage generated by the load variation of the load tooth 62 can be detected.

[0178] Based on the stepper motor control device 100 configured in this way, the circuit configuration of the voltage detection circuit 105 can be further simplified.

[0179] [Second Implementation] The second embodiment will be described. Furthermore, descriptions of configurations or functions identical to those in the first embodiment will be omitted.

[0180] Figure 11 This diagram illustrates an example of the functional configuration of the clock according to the second embodiment. Regarding the clock 1 of this embodiment, the hand drive unit 110A includes a stepper motor control device 100A. The stepper motor control device 100A differs from the stepper motor control device 100 in that it also includes a storage unit 108 in addition to the functional units described above.

[0181] The stepper motor control device 100A of this embodiment has an interpolation function for load detection results.

[0182] The storage unit 108 stores the detection result of the induced voltage detected by the voltage detection circuit 105 in a corresponding manner with the number of steps of the rotor 22, based on the control of the control circuit 103.

[0183] [Interpolation function for load detection results] Figure 12 This is a diagram illustrating an example of the load detection results in this embodiment. The clock gear train 31 described above is used as an example.

[0184] In the hour wheel train 31, the second wheel 33 and the third wheel 32 each have load teeth. In the following description, the load change caused by the load teeth of the third wheel 32 will be referred to as the first load, and the load change caused by the load teeth of the second wheel 33 will be referred to as the second load.

[0185] The hour gear train 31 has the gear ratio described in the first embodiment. In the case of the hour gear train 31 with the above gear ratio, if the rotor 22 advances 360 times, the first gear 34 rotates once. If the rotor 22 advances 45 times, the second gear 33 rotates once.

[0186] As described above, regarding the second gear 33, one tooth of the second gear 33a becomes a load tooth. Regarding the first gear 34, one tooth of the first gear 34a becomes a load tooth. Therefore, the first load is generated once for every revolution of the first gear 34. The second load is generated once for every revolution of the second gear 33.

[0187] In the case of the clockwise gear train 31 with the aforementioned gear ratio, the rotational angular velocity of the first gear 34 is smaller than that of the second gear 33. Therefore, the duration of the first load caused by the first gear 34 is longer than the duration of the second load caused by the second gear 33. That is, the first load caused by the first gear 34 lasts longer than the second load caused by the second gear 33.

[0188] Therefore, the control circuit 103 can determine whether it is the first load or the second load based on the difference in the generation width of the load variation. The control circuit 103 can control the rotation position of the pointer (e.g., the hour hand 6) by combining the generation timing of the first load with the generation timing of the second load.

[0189] Here, assuming that the induced voltage generated by the load teeth of the second wheel 33 is less than the judgment threshold voltage of the voltage detection circuit 105, and the voltage detection circuit 105 cannot detect the load change, the control circuit 103 may sometimes be unable to grasp the rotation position of the pointer (e.g., the hour hand 6).

[0190] In this embodiment, the control circuit 103 stores the timing of the generation of the second load detected by the voltage detection circuit 105 in the storage unit 108 in correspondence with the number of steps of the rotor 22.

[0191] As described above, the second load is generated every time the second wheel 33 rotates once. That is, as... Figure 12 As shown, the rotor 22 generates the second load every 90 steps.

[0192] In this example, the second load generated at the steps "45", "225" and "315" of rotor 22 was detected, but the second load generated at the step "135" of rotor 22 could not be detected.

[0193] If the generation of a second load is detected when the number of steps in rotor 22 is "45", the control circuit 103 stores the detection result of the second load in the storage unit 108 in a correspondence with the number of steps in rotor 22 "45".

[0194] Next, if the first load is detected at approximately "107" to "111" steps of rotor 22, the position at step "45" of rotor 22 where the second load is generated is determined as the reference position of the needle. The current needle position is calculated from this reference position and stored in the storage unit 108.

[0195] On the other hand, if the generation of the second load is not detected at step "135" of rotor 22, the control circuit 103 does not store the detection result in the storage unit 108.

[0196] If a second load is detected at step number "225" of rotor 22, the control circuit 103 stores the detection result of the second load in the storage unit 108 in correspondence with step number "225" of rotor 22. Furthermore, if the induced voltage of the second load is below a threshold for some reason at step number "135" of rotor 22, but the detection result is interpolated as if a second load has occurred, it is determined that there is no needle position shift. If a second load is detected at a step other than "225" of rotor 22, such as "226" or "224", it is determined that a timing event occurred at some point after step number "45" and the needle position shifted, and the number of steps from the reference position to the current needle position is corrected.

[0197] That is, the determination circuit 104 (determination unit) in this embodiment determines the timing at which the induced voltage should be detected by interpolating the result detected by the voltage detection circuit 105 (voltage detection unit) based on the detection cycle of the previously detected induced voltage.

[0198] Therefore, according to the stepper motor control device 100A, even if the generation of the second load cannot be detected temporarily, the control circuit 103 can still grasp the rotation position of the pointer (e.g., the hour hand 6).

[0199] The stepper motor control device 100A configured in this way eliminates the need for complex circuitry to detect the generation of the second load, thus simplifying the configuration of the pointer position detection circuit.

[0200] Furthermore, in this embodiment, the interpolation operation of the load detection result performed by the control circuit 103 is described, but it is not limited to this. For example, the determination circuit 104 may also be configured to perform the interpolation operation of the load detection result.

[0201] In addition, in this embodiment, the gear train (clock gear train 31) driven by the stepper motor control device 100A has the gear ratio described in the first embodiment, but is not limited thereto.

[0202] For example, the gear train driven by the stepper motor control device 100A may also have the gear ratio described as a comparative example in the first embodiment described above.

[0203] In this embodiment, the first wheel 34, the second wheel 33, and the third wheel 32 are described as examples of wheel number two, wheel number three, and wheel number four, respectively, but other wheel systems may also be used. For example, in a configuration where the rotor linked to the second and minute hands is composed of wheel number five, wheel number four, wheel number three, and wheel number two in sequence, wheel number two has the first load and wheel number four has the second load. Alternatively, in a configuration where the rotor is composed of intermediate wheel A, intermediate wheel B, and wheel number two (or hour wheel in the case of the hour hand) in sequence, starting from the rotor independent of the minute or hour hand, wheel number two (or hour wheel) has the first load and intermediate wheel B has the second load.

[0204] Alternatively, the control circuit 103 may be pre-assigned a detection cycle for the second load, or it may be configured to determine the detection cycle based on past detection results of the second load.

[0205] Furthermore, all or part of the functions of the clock 1 described above can be recorded as a program on a computer-readable recording medium, which is then executed by the computer system. A computer system is a hardware system that includes an operating system, peripheral devices, etc. Additionally, computer-readable recording media include portable media such as floppy disks, magneto-optical disks, ROM (Read Only Memory), and CD-ROMs; storage devices such as hard disks built into computer systems; and volatile memory (RAM) found in servers on networks such as the Internet. Furthermore, volatile memory is an example of a recording medium that stores a program for a certain period of time.

[0206] In addition, the above-mentioned program can also be transmitted to other computer systems via transmission media, such as networks like the Internet, or communication lines like telephone lines.

[0207] Alternatively, the program described above can be a program that implements all or part of the functions described above. Furthermore, a program that implements part of the functions described above can also be a program that can be implemented in combination with a program that pre-records the functions described above in the computer system; this is known as a differential program.

[0208] The embodiments of the present invention have been described above with reference to the accompanying drawings, but the specific configuration is not limited to the embodiments described above, and also includes design changes, etc., without departing from the spirit of the present invention.

[0209] Symbol Explanation 1... Clock, 4... Movement (clock movement), 6... Hour hand (hand), 20A... First motor (stepper motor), 22... Rotor, 31... Hour hand gear train, 32... Third wheel, 33... Second wheel, 34... First wheel, 62... Load tooth, 100... Stepper motor control device, 103... Control circuit, 104... Decision circuit, 105... Voltage detection circuit, 106... Motor drive circuit, 1061... First driver, 1062... Second driver, 1051... Comparator, 1052... Voltage detection resistor, 1053... Voltage detection switch, 1054... Voltage detection point.

Claims

1. A stepper motor control device, comprising: The drive unit is a circuit that drives a stepper motor having a rotor that rotates a pointer and a coil that generates magnetic flux for rotating the rotor. It includes a first drive circuit that supplies a first current flowing in the direction from a first end to a second end of the coil and a second drive circuit that supplies a second current flowing in the direction from the second end to the first end. The control unit outputs drive pulses for causing the rotor to rotate in half a revolution at a time and oscillation pulses for causing the rotor to oscillate to the drive unit. A gear train, comprising load teeth having a different rotational load than the other teeth and an odd number of rotational steps of the rotor in one revolution, transmits rotational force from the rotor to the pointer; The voltage detection unit, which is connected only to the first end of the coil, detects only the induced voltage generated at the first end of the coil when the rotor vibrates; as well as The determination unit determines, based on the result detected by the voltage detection unit, the mechanical load on the rotor caused by the contact between the load teeth of the load gear and the teeth meshing with the load gear.

2. The stepper motor control device according to claim 1, wherein, The gear train comprises: a first gear that rotates at an angular velocity consistent with the angular velocity of the pointer; a second gear having a pinion gear meshing with the gear of the first gear and the load gear; and a third gear having a pinion gear meshing with the load gear of the second gear and a gear meshing with the rotor.

3. The stepper motor control device according to claim 2, wherein, The number of rotation steps of the rotor in the second rotation is odd.

4. The stepper motor control device according to claim 2, wherein, The second wheel has an odd number of teeth.

5. The stepper motor control device according to any one of claims 2 to 4, wherein, The first gear has a load-bearing tooth that has a different rotational load than the other teeth. The determination part determines the first load as the mechanical load on the rotor caused by the contact between the pinion of the second wheel and the load tooth of the first wheel, and the second load as the mechanical load on the rotor caused by the contact between the pinion of the third wheel and the load tooth of the second wheel.

6. The stepper motor control device according to claim 1, wherein, The stepper motor has multiple coils. The driving unit includes a group of first driving circuits and second driving circuits that correspond to the plurality of coils respectively.

7. The stepper motor control device according to claim 1, wherein, The determination unit determines the timing at which the induced voltage should be detected by interpolating the results detected by the voltage detection unit based on the detection cycle of the previously detected induced voltage.

8. A stepper motor control device, comprising: The drive unit includes circuitry for driving a stepper motor that has a rotor that rotates a pointer and a coil that generates magnetic flux to rotate the rotor. The control unit outputs drive pulses for rotating the rotor and oscillation pulses for oscillating the rotor to the drive unit; A gear train, including a load gear having load teeth that are different from the other teeth in terms of rotational load, transmits rotational force from the rotor to the pointer; The voltage detection unit, which is connected only to the first end of the coil, detects only the induced voltage generated in the first end of the coil when the rotor vibrates; as well as The determination unit determines, based on the results detected by the voltage detection unit, the mechanical load on the rotor caused by the contact between the load teeth of the load gear and the teeth of other gears meshing with the load gear, and determines the timing at which the mechanical load should be detected by interpolating the results detected by the voltage detection unit based on the detection cycle of the previously detected mechanical load.

9. A movement comprising: The stepper motor control device according to claim 1 or claim 8; and The stepper motor.

10. A timepiece comprising the movement according to claim 9.

11. A stepper motor control method, A drive unit, which is a circuit for driving a stepper motor having a rotor that rotates a pointer and a coil that generates magnetic flux for rotating the rotor, and having a first drive circuit that supplies a first current flowing in the direction from a first end to a second end of the coil and a second drive circuit that supplies a second current flowing in the direction from the second end to the first end, outputs drive pulses for causing the rotor to rotate half a revolution at a time and oscillation pulses for causing the rotor to oscillate to the drive unit. Only the induced voltage generated at the first end of the coil is detected in the induced voltage generated in the coil under the condition of rotor vibration. Based on the detection result of the induced voltage, it is determined that the mechanical load on the rotor is caused by the contact between the load teeth of the load gear, which has a load tooth that has a different rotational load than the other teeth in the gear train that transmits rotational force from the rotor to the pointer, and the number of rotation steps of the rotor in one revolution is odd, and the teeth of the other gears meshing with the load gear.

12. A stepper motor control method, The drive unit, which has a circuit for driving a stepper motor having a rotor that rotates a pointer and a coil that generates magnetic flux to rotate the rotor, outputs drive pulses for rotating the rotor and oscillation pulses for oscillating the rotor. Only the induced voltage generated at the first end of the coil under the condition of rotor vibration is detected. Based on the detection result of the induced voltage, it is determined that the mechanical load on the rotor is caused by the contact between the load teeth of the load gear and the teeth of other gears meshing with the load gear. The timing at which the mechanical load should be detected is determined by interpolating the detection results of the induced voltage based on the detection cycle of the previously detected mechanical load.

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