Rotational position detection device and position detection device
The rotary position detection device improves tracking ability by transitioning through three states using a code plate with blocking and non-blocking sections and photointerrupters, addressing the limitations of conventional devices with four-state binary codes.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ALPS ALPINE CO LTD
- Filing Date
- 2025-12-26
- Publication Date
- 2026-07-23
AI Technical Summary
Conventional rotary encoders and position detection devices using two binary codes in four states have limited followability with respect to rotational and linear positions, necessitating an improvement in tracking ability.
A rotary position detection device utilizing a code plate with blocking and non-blocking sections, coupled with a first and second photointerrupter, where the output signal transitions through three states, allowing improved tracking of rotational and linear positions.
The device provides enhanced followability and tracking ability for rotational and linear movements by transitioning through three states, reducing power consumption and ensuring accurate position detection.
Smart Images
Figure JP2025045936_23072026_PF_FP_ABST
Abstract
Description
Rotary position detection device and position detection device
[0006]
[0001] The present disclosure relates to a rotary position detection device and a position detection device.
[0002] Conventionally, in a rotary encoder having a light emitting element and two light receiving elements, there is a rotary encoder that converts the outputs of the two light receiving elements into two binary codes and obtains rotation information based on the two binary codes in four states (see, for example, Patent Document 1).
[0003] Japanese Patent Application Laid-Open No. 2009-128061
[0004] By the way, a conventional rotary encoder obtains rotation information based on two binary codes in four states. That is, since the rotational position is detected based on the four states in which the outputs of the two light receiving elements transition, there is room for improvement in the followability with respect to the rotational position. If the number of states in which the output transitions can be reduced to three, the followability with respect to the rotational position can be improved. Further, not limited to the rotary encoder, when detecting a linearly moving position based on two binary codes in four states, there is similarly room for improvement in the followability with respect to rotation.
[0005] Therefore, an object is to provide a rotary position detection device and a position detection device having good followability with respect to a position that rotates or linearly moves by causing an output signal to transition through three states.
[0006] The rotary position detection device according to an embodiment of the present disclosure includes a blocking portion that blocks light and a non-blocking portion that transmits or reflects light, a code plate that rotates together with a rotating member, an output portion that outputs an output signal corresponding to the rotation of the code plate, and a control portion that acquires the output signal and detects the rotational position of the code plate, the output portion includes a first photointerrupter including a first photodiode and a first phototransistor, and a second photointerrupter including a second photodiode and a second phototransistor, the first photointerrupter and the second photointerrupter are connected so that the second photodiode can be lit when the first phototransistor is on, and the output signal transitions through three states.
[0007] By having the output signal transition through three states, it is possible to provide a rotational position detection device and a position detection device that have good tracking ability for rotationally moving positions or linearly moving positions.
[0008] This is a diagram showing a rotational position detection device according to an embodiment. This is a diagram showing an example of the circuit configuration of the rotational position detection device according to an embodiment. This is a diagram illustrating an example of the three state transitions of inputs A and B of the rotational position detection device according to an embodiment. This is a diagram illustrating an example of the three state transitions of inputs A and B of the rotational position detection device according to an embodiment. This is a diagram illustrating an example of the three state transitions of inputs A and B of the rotational position detection device according to an embodiment. This is a diagram illustrating an example of the three state transitions of inputs A and B of the rotational position detection device according to an embodiment. This is a diagram illustrating an example of the three state transitions of inputs A and B of the rotational position detection device according to an embodiment. This is a diagram illustrating an example of the circuit configuration of the rotational position detection device according to a first modified example of the embodiment. This is a diagram illustrating an example of the state transitions of inputs A and B in the rotational position detection device according to a first modified example of the embodiment. This is a diagram showing an example of the circuit configuration of the rotational position detection device according to a second modified example of the embodiment. This is a diagram illustrating an example of the three state transitions of input A of the rotational position detection device according to a second modified example of the embodiment. This is a diagram illustrating an example of the three state transitions of input A of the rotational position detection device according to a second modified example of the embodiment. This figure illustrates an example of three state transitions for input A of the rotational position detection device in the second modified embodiment. This figure illustrates an example of three state transitions for input A of the rotational position detection device in the second modified embodiment. This figure illustrates an example of three state transitions for input A of the rotational position detection device in the second modified embodiment. This figure illustrates an example of three state transitions for input A of the rotational position detection device in the second modified embodiment.
[0009] The following describes the rotational position detection device and embodiments to which the position detection device of this disclosure is applied.
[0010] <Embodiment> Figure 1 shows a rotational position detection device 100 according to an embodiment. The following description will use the XYZ Cartesian coordinate system.
[0011] The rotational position detection device 100 includes a code plate 110, an output unit 120, and an MCU 130. The MCU 130 is an example of a control unit.
[0012] In Figure 1, the code plate 110 is a circular disc-shaped member in XY plane view, and rotates together with a rotating member that rotates around a rotation axis parallel to the Z axis. The rotating member can be any rotating member whose rotational position needs to be detected, for example, the document feeder of a copier. Furthermore, the rotating member is not limited to the document feeder of a copier, but may also be, for example, the rotational operation part of a rotary input device that has a rotary operation part such as a dial operated by the user. In this case, the code plate 110 can be attached to the rotational axis of the rotational operation part to detect the rotational position of the rotational operation part. Furthermore, the rotating member may also be, for example, a rotating member that rotates together with the rotational axis of the drive mechanism of an automatic machine such as a belt conveyor that transports workpieces. In this case, the code plate 110 can be attached to the rotational axis of the drive mechanism of the belt conveyor to detect the rotational position of the rotational axis of the drive mechanism of the belt conveyor.
[0013] The code board 110 has a plurality of blocking sections 111 and a plurality of transparent sections 112. The transparent sections 112 are an example of non-blocking sections. The blocking sections 111 are opaque parts that block light. The transparent sections 112 are parts that transmit light and are made of transparent material or are made of openings provided in the code board 110.
[0014] Figure 1 shows two adjacent blocking sections 111 with one transparent section 112 in between. The multiple blocking sections 111 and multiple transparent sections 112 are arranged alternately in the circumferential direction along a circle concentric with the rotation axis of the code plate 110 in the XY plane view. The code plate 110 is a circular disc-shaped member in the XY plane view, but Figure 1 shows the two blocking sections 111 and the one transparent section 112 in a linear direction. In Figure 1, the circumferential direction of the code plate 110 is the lateral direction, and the blocking sections 111 and transparent sections 112 are described as moving in the lateral direction as the code plate 110 rotates. In the following explanation, the left-right direction in Figure 1 may be used.
[0015] The output unit 120 includes a first photointerrupter 121 and a second photointerrupter 122. The first photointerrupter 121 is, for example, a transmissive type and comprises a first photodiode 121A and a first phototransistor 121B. The first photodiode 121A emits light toward the first phototransistor 121B.
[0016] The second photointerrupter 122 is, for example, a transmissive type and comprises a second photodiode 122A and a second phototransistor 122B. The second photodiode 122A emits light toward the second phototransistor 122B.
[0017] The first photodiode 121A and the first phototransistor 121B are arranged opposite each other across the circumferential track of the cutoff portion 111 and the transparent portion 112 of the code plate 110. Similarly, the second photodiode 122A and the second phototransistor 122B are arranged opposite each other across the circumferential track of the cutoff portion 111 and the transparent portion 112 of the code plate 110.
[0018] As the code plate 110 rotates, the first photointerrupter 121 switches between a state where the light emitted from the first photodiode 121A passes through the transmissive section 112 and is received by the first phototransistor 121B, as shown in Figure 1, and a state where it is blocked by the blocking section 111 and is not received by the first photointerrupter 121.
[0019] Similarly, as the code plate 110 rotates, the second photointerrupter 122 switches between a state where the light emitted from the second photodiode 122A passes through the transmissive section 112 and is received by the second phototransistor 122B, as shown in Figure 1, and a state where it is blocked by the blocking section 111 and not received by the second photointerrupter 122.
[0020] The MCU 130 is connected to the output unit 120 and acquires the output signal output from the output unit 120 to detect the rotational position of the code board 110. The output signal from the output unit 120 is a signal representing the potential of the first photointerrupter 121 and the second photointerrupter 122. Details of the output signal will be described later.
[0021] As shown in Figure 1, let w be the length of the blocking section 111 in the circumferential direction, L be the pitch between adjacent blocking sections 111 in the circumferential direction, and d be the pitch between the first photointerrupter 121 and the second photointerrupter 122 in the circumferential direction. The length w is the length of the blocking section 111 along the circumference and corresponds to an angle. The pitch L is the pitch between adjacent blocking sections 111 along the circumference and corresponds to an angle. The pitch between adjacent blocking sections 111 along the circumference is the distance between the centers of adjacent blocking sections 111 along the circumference. Therefore, pitch L corresponds to an angle. The pitch d is the pitch between the first photointerrupter 121 and the second photointerrupter 122 along the circumference and is the distance between the centers of the first photointerrupter 121 and the second photointerrupter 122 along the circumference. Therefore, pitch d corresponds to an angle. Here, we will describe an example of a configuration where d ≤ w < L holds, but it is sufficient that at least d ≤ w holds, and the configuration may be such that only one of the first photointerrupter 121 and the second photointerrupter 122 is located within the pitch L.
[0022] Here, we consider a state in which the first photointerrupter 121 is not blocked by the right-side blocking portion 111, and the second photointerrupter 122 is blocked by the right-side blocking portion 111 shown in Figure 1, and the left end of the right-side blocking portion 111 shown in Figure 1 coincides with the right end of the first photointerrupter 121. The state in which the left end of the right-side blocking portion 111 coincides with the right end of the first photointerrupter 121 is a state in which the first photointerrupter 121 is no longer blocked by the right-side blocking portion 111 as the code plate 110 rotates and moves to the right in Figure 1. From this state, as the code plate 110 rotates and moves to the right in Figure 1, the transparent portion 112 is positioned between the first photodiode 121A and the first phototransistor 121B, and between the second photodiode 122A and the second phototransistor 122B. In other words, the rotation angle from the state where the left end of the right-side blocking part 111 coincides with the right end of the first photointerrupter 121, to the state where the left end of the right-side blocking part 111 coincides with the right end of the second photointerrupter 122, as shown in Figure 1, is d. The state where the left end of the right-side blocking part 111 coincides with the right end of the second photointerrupter 122 is the state where the second photointerrupter 122 is no longer blocked by the right-side blocking part 111, as the code plate 110 rotates and moves to the right in Figure 1. The operation to obtain such a rotation angle d is referred to as operation (1).
[0023] In Figure 1, for the sake of simplicity, the first photodiode 121A and first phototransistor 121B of the first photointerrupter 121, and the second photodiode 122A and second phototransistor 122B of the second photointerrupter 122 are provided across the entire width in the X direction, and the width in the X direction of the light emitted by the first photodiode 121A and the second photodiode 122A is equal to the width in the X direction of the first photodiode 121A and the second photodiode 122A. For this reason, when the blocking unit 111 moves to the right, the position where the first photointerrupter 121 switches to a blocked state and the position where the first photointerrupter 121 switches to a state where it is no longer blocked are described as being at the right end of the first photointerrupter 121. The same applies to the second photointerrupter 122.
[0024] However, the first photodiode 121A and the first phototransistor 121B of the first photointerrupter 121 may not be present across the entire width in the X direction of the first photointerrupter 121, and the width in the X direction of the light emitted by the first photodiode 121A and received by the first phototransistor 121B may be narrower than the entire width in the X direction of the first photointerrupter 121. In such cases, the position where the first photointerrupter 121 switches to a blocked state and the position where the first photointerrupter 121 switches to a state where it is no longer blocked are the position where the optical path of the light emitted and received between the first photodiode 121A and the first phototransistor 121B is blocked and the position where it is no longer blocked. The same applies to the second photointerrupter 122.
[0025] Furthermore, as described above, from the state in which the transparent portion 112 is positioned between the first photodiode 121A and the first phototransistor 121B and between the second photodiode 122A and the second phototransistor 122B, the code plate 110 rotates and moves to the right in Figure 1, so that the left-side blocking portion 111 shown in Figure 1 is positioned between the first photodiode 121A and the first phototransistor 121B, and the transparent portion 112 is positioned between the second photodiode 122A and the second phototransistor 122B. That is, the rotation angle from the state in which the transparent portion 112 is positioned between the first photodiode 121A and the first phototransistor 121B and between the second photodiode 122A and the second phototransistor 122B until the right end of the left-side blocking portion 111 shown in Figure 1 coincides with the right end of the first photointerrupter 121 is L-w-d. The operation to obtain such a rotation angle L-w-d is referred to as operation (2).
[0026] Furthermore, as described above, the left-side cutoff portion 111 shown in Figure 1 is located between the first photodiode 121A and the first phototransistor 121B, and the transparent portion 112 is located between the second photodiode 122A and the second phototransistor 122B. As the code plate 110 rotates and moves to the right in Figure 1, the left-side cutoff portion 111 shown in Figure 1 is located between the first photodiode 121A and the second phototransistor 122B, and between the second photodiode 122A and the second phototransistor 122B. That is, the rotation angle from the state in which the left-side cutoff portion 111 shown in Figure 1 is located between the first photodiode 121A and the first phototransistor 121B, and the transparent portion 112 is located between the second photodiode 122A and the second phototransistor 122B, until the right end of the left-side cutoff portion 111 coincides with the right end of the second photointerrupter 122, is d.
[0027] Furthermore, as described above, the left-side blocking portion 111 shown in Figure 1 is positioned between the first photodiode 121A and the first phototransistor 121B and between the second photodiode 122A and the second phototransistor 122B. As the code plate rotates and moves to the right in Figure 1, the transparent portion 112 is positioned between the first photodiode 121A and the first phototransistor 121B, and the left-side blocking portion 111 shown in Figure 1 is positioned between the second photodiode 122A and the second phototransistor 122B. That is, the rotation angle from the state in which the left-side blocking portion 111 shown in Figure 1 is positioned between the first photodiode 121A and the first phototransistor 121B and between the second photodiode 122A and the second phototransistor 122B until the left end of the left-side blocking portion 111 coincides with the right end of the first photointerrupter is w-d. The operation to obtain the rotation angle w obtained by combining the rotation angle d and the rotation angle w-d is referred to as operation (3).
[0028] In operations (1), (2), and (3), the condition for the rotation angles L-w-d, d, and w to be equal is that L-w-d = d = w, so w = d = L / 3. In this case, with respect to the pitch L of the transparent portion 112 in the circumferential direction, the length of the transparent portion 112 in the circumferential direction is L / 3, and the distance between the first photointerrupter 121 and the second photointerrupter 122 in the circumferential direction is L / 3.
[0029] Although Figure 1 shows the first and second photointerrupters 121 and 122, which are of the transmissive type, the first and second photointerrupters 121 and 122 may also be of the reflective type. In this case, the code plate 110 may have a portion that absorbs or blocks light instead of the blocking portion 111, and a reflective portion that reflects light instead of the transmissive portion 112. For example, if the light is infrared light, the absorbing portion may be made black and the reflective portion may be made white.
[0030] <Circuit Configuration of Rotation Position Detection Device 100> Figure 2 shows an example of the circuit configuration of the rotation position detection device 100. Figure 2 shows an example of the connection relationship between the output unit 120 and the MCU 130. The output unit 120 has a first photo interrupter 121, a second photo interrupter 122, connection points 125A and 125B, and wiring 126A and 126B. The MCU 130 has input ports 130A and 130B. Wiring 126A and 126B are connected to input ports 130A and 130B, respectively.
[0031] In the following, when two components, A and B, are present, the expression "component A and component B are connected" includes the state in which component A and component B are connected via a resistor or the like.
[0032] Furthermore, Figure 2 shows three power supplies Vcc. The three power supplies Vcc are common, but when distinguished for the purpose of explaining the circuit configuration, they are referred to as power supplies Vcc(1), Vcc(2), and Vcc(3). When power supplies Vcc(1), Vcc(2), and Vcc(3) are not specifically distinguished, they are simply referred to as power supply Vcc. Power supplies Vcc(1), Vcc(2), and Vcc(3) may, for example, be power supplies supplied from a device having a rotating member, or power supplies directly supplied to the rotational position detection device 100.
[0033] The anode of the first photodiode 121A is connected to the power supply Vcc(1) via a resistor, and the cathode of the first photodiode 121A is connected to GND. GND is an example of a reference potential point. The emitter of the first phototransistor 121B is connected to GND, and the collector of the first phototransistor 121B is connected to the cathode of the second photodiode 122A and to the input port 130A of the MCU 130.
[0034] The anode of the second photodiode 122A is connected to the power supply Vcc(2) via a resistor, the collector of the second phototransistor 122B is connected to the power supply Vcc(3) via a resistor, and the emitter of the second phototransistor 122B is connected to GND.
[0035] The second photodiode 122A is connected between the power supply Vcc(2) and the first phototransistor 121B, and therefore lights up when the first phototransistor 121B is on (conducting).
[0036] The connection point 125A is the connection point that connects the collector of the first phototransistor 121B and the cathode of the second photodiode 122A, and is connected to the input port 130A of the MCU 130 via wiring 126A. The output unit 120 outputs output signal A to the input port 130A of the MCU 130 via connection point 125A and wiring 126A.
[0037] Connection point 125B is a connection point that connects the collector of the second phototransistor 122B to a resistor connected to the power supply Vcc (3). Connection point 125B is connected to the input port 130B of the MCU 130 via wiring 126B. The output unit 120 outputs output signal A to the input port 130B of the MCU 130 via connection point 125B and wiring 126B.
[0038] The MCU 130 digitally converts the output signals A and B of the output unit 120, which are input to input ports 130A and 130B, and determines whether the signal levels of the digitally converted output signals A and B are Hi (High) or Lo (Low) levels. The MCU 130 uses a threshold for Hi level determination and a threshold for Lo level determination for this determination. The threshold for Hi level determination is greater than the threshold for Lo level determination. Inputs A and B, which are input to the MCU 130 from input ports 130A and 130B, are digital signals of either Lo level or Hi level.
[0039] Output signal A, which represents the potential at connection point 125A, is one of two output signals that output from output unit 120 to MCU 130, and is input to input port 130A of MCU 130 via wiring 126A. Output signal A, which represents the potential at connection point 125A, is a signal that represents the potential of the collector of the first phototransistor 121B. Since connection point 125A connects the collector of the first phototransistor 121B and the cathode of the second photodiode 122A, the potential at connection point 125A is the potential of the collector of the first phototransistor 121B and the potential of the cathode of the second photodiode 122A.
[0040] The potential at connection point 125A is approximately equal to the GND potential when the first phototransistor 121B is ON (conducting). Therefore, when the first phototransistor 121B is ON, the output signal A representing the potential at connection point 125A is determined to be at a Lo level by the MCU 130, resulting in a Lo level input A. When the first phototransistor 121B is OFF, the second photodiode 122A is OFF, and the potential of the cathode of the second photodiode 122A is approximately equal to the potential Vcc of the power supply Vcc(2). Therefore, when the first phototransistor 121B is OFF, the output signal A representing the potential at connection point 125A is determined to be at a Hi level by the MCU 130, resulting in a Hi level input A.
[0041] The output signal B, which represents the potential at connection point 125B, is the other of two output signals that the output unit 120 outputs to the MCU 130, and is input to the input port 130B of the MCU 130 via wiring 126B. The potential at connection point 125B is approximately equal to the GND potential when the second phototransistor 122B is ON (conducting). Therefore, when the second phototransistor 122B is ON, the output signal B representing the potential at connection point 125B is determined to be a Lo level in the MCU 130, and becomes a Lo level input B. When the second phototransistor 122B is OFF, the potential at connection point 125B is approximately equal to the potential Vcc of the power supply Vcc(3). Therefore, when the second phototransistor 122B is OFF, the output signal B representing the potential at connection point 125B is determined to be a Hi level in the MCU 130, and becomes a Hi level input B.
[0042] As described above, the two output signals A and B output by the output unit 120 are signals representing the potential of the collector of the first phototransistor 121B and the potential of the collector of the second phototransistor 122B.
[0043] In addition, the first photointerrupter 121 and the second photointerrupter 122 are connected so that the second photodiode 122A can be lit when the first phototransistor 121B is on (conducting state).
[0044] <Examples of Three State Transitions of Inputs A and B> FIGS. 3A, 3B, 4A, 4B, 5A, and 5B are diagrams for explaining an example of three state transitions of inputs A and B of the rotational position detection device 100. FIGS. 3A, 4A, and 5A show the presence or absence of the blocking portion 111 in the first photointerrupter 121 and the second photointerrupter 122 in the circuit diagram of FIG. 2, and the operations of the first photointerrupter 121 and the second photointerrupter 122. FIGS. 3B, 4B, and 5B show the state transitions of inputs A and B.
[0045] The MCU 130 detects the rotational position of the code plate 110 based on the inputs A and B generated from the output signals A and B. The inputs A and B transition to four types of states over the periods (1) to (4) shown in FIGS. 3B, 4B, and 5B. Hereinafter, the direction in which the code plate 110 rotates in the direction in which the periods (1) to (4) elapse is referred to as the forward rotation, and the direction in which the code plate 110 rotates in the direction in which the periods (4) to (1) elapse is referred to as the reverse rotation.
[0046] <Periods (1) and (4)> In FIG. 3A, the blocking portion 111 is located between the first photodiode 121A and the first phototransistor 121B of the first photointerrupter 121. Also, in FIG. 3A, the blocking portion 111 may or may not be located between the second photodiode 122A and the second phototransistor 122B of the second photointerrupter 122, so the blocking portion 111 is shown by a dashed line.
[0047] The state shown in FIG. 3A is the state during the period (1) when the first photointerrupter 121 and the second photointerrupter 122 are blocked by the blocking portion 111, and the period (4) when the first photointerrupter 121 is blocked by the blocking portion 111 and the second photointerrupter 122 is not blocked by the blocking portion 111.
[0048] During the periods (1) and (4), the first photodiode 121A is on (lit state), but since the first phototransistor 121B is not exposed to light and turns off, the second photodiode 122A turns off. Therefore, the second phototransistor 122B turns off in both the period (1) when the second photointerrupter 122 is blocked by the blocking portion 111 and the period (4) when the second photointerrupter 122 is not blocked by the blocking portion 111.
[0049] From the above, in the periods (1) and (4), input A becomes Hi level and input B becomes Hi level. Since the second photodiode 122A does not turn on when the first phototransistor 121B is off, in the periods (1) and (4), both input A and B become Hi level.
[0050] <Period (2)> In FIG. 4A, the blocking portion 111 is not located between the first photodiode 121A and the first phototransistor 121B of the first photointerrupter 121. Also, in FIG. 4A, the blocking portion 111 is located between the second photodiode 122A and the second phototransistor 122B of the second photointerrupter 122.
[0051] The state shown in FIG. 4A is the state during the period (2) when the first photointerrupter 121 is not blocked by the blocking portion 111 and the second photointerrupter 122 is blocked by the blocking portion 111.
[0052] During the period (2), the first photodiode 121A is on (lit state), and since the first phototransistor 121B is exposed to light and turns on, the second photodiode 122A turns on (lit state), but the second phototransistor 122B is not exposed to light and turns off.
[0053] Based on the above, during period (2), input A is at a low level and input B is at a high level.
[0054] <Period (3)> In Figure 5A, the cutoff section 111 is not located between the first photodiode 121A and the first phototransistor 121B of the first photointerrupter 121, nor is the cutoff section 111 located between the second photodiode 122A and the second phototransistor 122B of the second photointerrupter 122.
[0055] The state shown in Figure 5A is the state during the period (3) when neither the first photointerrupter 121 nor the second photointerrupter 122 is interrupted by the interruption unit 111.
[0056] During period (3), the first photodiode 121A is turned on (lit), and the first phototransistor 121B receives light and turns on, so the second photodiode 122A also turns on (lit). Then, the second phototransistor 122B receives light and turns on.
[0057] Based on the above, during period (3), input A is at a low level and input B is at a low level.
[0058] In the rotational position detection device 100, during periods (1) to (4) of the combination of interruption / non-interruption of the first photointerrupter 121 and the second photointerrupter 122, the levels of inputs A and B are equal during periods (1) and (4). Therefore, in the rotational position detection device 100, inputs A and B transition through three states. In other words, the output signals A and B of the rotational position detection device 100 transition through three states.
[0059] The three states of output signals A and B are examples of the first, second, and third states, respectively. The first state is the state in which output signals A and B are obtained during periods (1) and (4), and operation (3) of the code board 110 corresponds to this state. The second state is the state in which output signals A and B are obtained during period (2), and operation (1) of the code board 110 corresponds to this state. The third state is the state in which output signals A and B are obtained during period (3), and operation (2) of the code board 110 corresponds to this state.
[0060] The first state is a state in which the blocking portion 111 is located between the first photodiode 121A and the first phototransistor 121B and between the second photodiode 122A and the second phototransistor 122B, and a state in which the blocking portion 111 is located between the first photodiode 121A and the first phototransistor 121B and the non-blocking portion (transmissive portion 112) is located between the second photodiode 122A and the second phototransistor 122B.
[0061] In the first state, the cutoff section 111 is located between the first photodiode 121A and the first phototransistor 121B, and the non-cutoff section (transmitting section 112) is located between the second photodiode 122A and the second phototransistor 122B. This state is characterized by the first phototransistor 121B being turned off, which in turn causes the second photodiode 122A to be in a non-lit state.
[0062] The second state is one in which a non-blocking section (transmitting section 112) is located between the first photodiode 121A and the first phototransistor 121B, and a blocking section 111 is located between the second photodiode 122A and the second phototransistor 122B.
[0063] The third state is one in which non-blocking sections (transmitting sections 112) are located between the first photodiode 121A and the first phototransistor 121B and between the second photodiode 122A and the second phototransistor 122B.
[0064] The MCU 130 can detect the rotational position and direction of the code plate 110 by converting inputs A and B in the order of first state to third state, or third state to first state. Since the first state to third state have different combinations of Hi and Lo levels for inputs A and B, the MCU 130 can accurately detect the rotational position and direction of the code plate 110 even if it rotates in the reverse direction midway through the first state to third state or third state to first state. Furthermore, the MCU 130 can accurately detect the rotational position and direction of the code plate 110 even if the state starts midway through the first state to third state or third state to first state.
[0065] <Effects> The rotation position detection device 100 includes a code plate 110 that rotates together with a rotating member, a code plate 110 that rotates together with a rotating member, a code plate 120 that outputs an output signal corresponding to the rotation of the code plate 110, and an MCU 130 that acquires the output signal and detects the rotation position of the code plate 110. The output unit 120 includes a first photointerrupter 121 equipped with a first photodiode 121A and a first phototransistor 121B, and a second photointerrupter 122 equipped with a second photodiode 122A and a second phototransistor 122B. The first photointerrupter 121 and the second photointerrupter 122 are connected such that the second photodiode 122A can be lit when the first phototransistor 121B is ON, and the output signal transitions through three states. The second photodiode 122A is connected so that it can be lit when the first phototransistor 121B is ON. Therefore, when the first phototransistor 121B is OFF, the level of the output signal based on the operating state of the second photointerrupter 122 will be the same whether the second photointerrupter 122 is blocked by the blockage unit 111 or not.
[0066] Therefore, by having the output signal transition through three states, a rotational position detection device 100 with good tracking ability for rotational movement can be provided. In addition, since the second photodiode 122A does not light up when the first phototransistor 121B is off, power consumption can be reduced.
[0067] Alternatively, the anode of the first photodiode 121A is connected to the power supply Vcc, the cathode of the first photodiode 121A is connected to GND, the emitter of the first phototransistor 121B is connected to GND, the collector of the first phototransistor 121B is connected to the cathode of the second photodiode 122A, the anode of the second photodiode 122A is connected to the power supply Vcc, the collector of the second phototransistor 122B is connected to the power supply Vcc, and the emitter of the second phototransistor 122B is connected to GND. The output signal may represent the potential of the cathode of the second photodiode 122A and the potential of the collector of the second phototransistor 122B. Since the collector of the first phototransistor 121B is connected to the cathode of the second photodiode 122A, when the first phototransistor 121B is off, the second phototransistor 122B is off during both the period (1) when the second photointerrupter 122 is interrupted by the interruption unit 111 and the period (4) when the second photointerrupter 122 is not interrupted by the interruption unit 111. As a result, the levels of inputs A and B are both equal to a high level during periods (1) and (4), and the output signal transitions through three states. This makes it possible to provide a rotational position detection device 100 with good tracking ability for rotational movement.
[0068] In addition, the above description concerns a rotation position detection device 100 that detects the rotational position of the cord plate 110 which rotates together with the rotating member. However, instead of a rotatable cord plate 110, a position detection device that detects the position of a cord plate using a cord plate that moves linearly may also be used.
[0069] In other words, the device includes a code board 110 having a blocking section 111 that blocks light and a non-blocking section (transmitting section 112) that transmits or reflects light, and movable in the direction connecting the blocking section 111 and the non-blocking section (transmitting section 112); an output section 120 that outputs an output signal according to the position of the code board 110; and an MCU 130 that acquires the output signal and detects the position of the code board 110. The output section 120 includes a first photointerrupter 121 having a first photodiode 121A and a first phototransistor 121B, and a second photointerrupter 122 having a second photodiode 122A and a second phototransistor 122B. The first photointerrupter 121 and the second photointerrupter 122 are connected such that the second photodiode 122A can be lit when the first phototransistor 121B is ON. The output signal may be a position detection device that transitions through three states. By having the output signal transition through three states, a position detection device with good tracking ability for moving positions can be provided.
[0070] Furthermore, the above describes a configuration in which the first photointerrupter 121 and the second photointerrupter 122 are at the same position in the Z direction. However, as an example, if there are two code plates that are spaced apart in the Z direction and move linearly together, the positions of the first photointerrupter 121 and the second photointerrupter 122 in the Z direction may be different. In this case, the first photointerrupter 121 may be provided corresponding to one code plate, and the second photointerrupter 122 may be provided corresponding to the other code plate. In this case, the position detection device can detect the position of a code plate in the same way as when using the first photointerrupter 121 and the second photointerrupter 122, which are at the same position in the Z direction with respect to one linearly moving code plate.
[0071] Alternatively, the position detection device may use a first photointerrupter 121 and a second photointerrupter 122, which are positioned at different locations in the Y direction, to detect the position of a single linearly moving code board, similar to the case where a first photointerrupter 121 and a second photointerrupter 122 are positioned at the same location in the Y direction for a single linearly moving code board.
[0072] Furthermore, if there are two circular, disc-shaped code plates 110 in an XY plane view, and they are spaced apart in the Z direction and rotate together around the same axis of rotation, the positions of the first photointerrupter 121 and the second photointerrupter 122 in the Z direction may be different. In this case, the first photointerrupter 121 may be provided corresponding to one code plate 110, and the second photointerrupter 122 may be provided corresponding to the other code plate 110. This means that the position detection device can detect the positions of the two code plates 110 in the same way as when using the first photointerrupter 121 and the second photointerrupter 122, which are at the same position in the Z direction relative to one rotating code plate 110.
[0073] Alternatively, a position detection device may be used that detects the position of a single rotating disc-shaped code plate 110 using a first photointerrupter 121 and a second photointerrupter 122 that are at different radial positions on the code plate 110, similar to the case where a first photointerrupter 121 and a second photointerrupter 122 are at the same radial position on a single rotating code plate 110.
[0074] <First Modification> Figure 6A shows an example of the circuit configuration of the rotational position detection device 100M1 of the first modification of the embodiment. Components similar to those of the rotational position detection device 100 shown in Figure 2 are denoted by the same reference numerals, and their descriptions are omitted.
[0075] The rotational position detection device 100M1 has a configuration in which a buffer transistor 123 is added to the output unit 120 of the rotational position detection device 100 shown in Figure 2, and the connection of the second photodiode 122A to the connection point 125A is changed.
[0076] The buffer transistor 123 has an emitter connected to the power supply Vcc(2) and a collector connected to the anode of the second photodiode 122A. The emitter and base of the buffer transistor 123 are connected by a resistor R1, and the base of the buffer transistor 123 is connected to connection point 125A via a resistor R2. The cathode of the second photodiode 122A is connected to GND via a resistor.
[0077] Output signal A, output from connection point 125A, represents the collector potential of the first phototransistor 121B, and output signal B, output from connection point 125B, represents the collector potential of the second phototransistor 122B.
[0078] The buffer transistor 123 has the characteristic of turning off when a voltage higher than the high-level determination threshold used by the MCU 130 to determine whether the output signal A input to the input port 130A is at a high level is input to its base.
[0079] <Operation of Rotation Position Detection Device 100M1> Figure 6B is a diagram showing an example of the state transitions of inputs A and B in the rotation position detection device 100M1. Here, the rotation position detection device 100 will be explained using the same periods (1) to (4) as those explained using Figures 3A, 3B, 4A, 4B, 5A, and 5B.
[0080] <Periods (1) and (4)> During periods (1) and (4), the first photodiode 121A is on (lit), but the first phototransistor 121B does not receive light and turns off, so the second photodiode 122A turns off. As a result, the buffer transistor 123 turns off, the second photodiode 122A turns off, and the second phototransistor 122B turns off.
[0081] Therefore, the second phototransistor 122B is turned off during both the period (1) when the second photointerrupter 122 is blocked by the blockage unit 111 and the period (4) when the second photointerrupter 122 is not blocked by the blockage unit 111.
[0082] Therefore, during periods (1) and (4), input A is at a high level and input B is at a high level. Since the second photodiode 122A does not turn on when the first phototransistor 121B is off, during periods (1) and (4), both inputs A and B are at a high level.
[0083] <Period (2)> During period (2), the first photodiode 121A is on (lit), and the first phototransistor 121B receives light and turns on, so the buffer transistor 123 turns on. As a result, the second photodiode 122A turns on (lit), but the second phototransistor 122B does not receive light and turns off.
[0084] Based on the above, during period (2), input A is at a low level and input B is at a high level.
[0085] <Period (3)> During period (3), the first photodiode 121A is on (lit), and the first phototransistor 121B receives light and turns on, so the buffer transistor 123 turns on. As a result, the second photodiode 122A is turned on (lit), and the second phototransistor 122B receives light and turns on.
[0086] Based on the above, during period (3), input A is at a low level and input B is at a low level.
[0087] Then, as the code board 110 rotates in the forward direction and transitions from period (3) to period (4), the cutoff section 111 is positioned between the first photodiode 121A and the first phototransistor 121B. As a result, the first phototransistor 121B turns off, the buffer transistor 123 turns off, the second photodiode 122A turns off, and the second phototransistor 122B turns off. In this way, when transitioning from period (3) to period (4), the buffer transistor 123 switches from on to off.
[0088] Here, when periods (1) to (4) switch, the levels of analog output signals A and B will change, so there is a possibility that the timing of output signals A and B may be out of sync.
[0089] If the timing of output signals A and B is not out of sync, when the code board 110 rotates in the forward direction and moves from period (3) to period (4), both output signals A and B transition to a Hi level. However, if the timing of output signals A and B is out of sync, and when the code board 110 rotates in the forward direction from period (3), a state occurs where output signal A is at a Lo level and output signal B is at a Hi level, the MCU 130 may mistakenly detect that the state has changed from period (3) to period (2).
[0090] This is a false detection that can occur when the code board 110 rotates in the positive direction from period (3), causing a timing difference between output signals A and B, resulting in a state where output signal A is at a low level and output signal B is at a high level.
[0091] To suppress such false detections, the rotational position detection device 100M1 is equipped with a buffer transistor 123, and the buffer transistor 123 is configured to turn off when a voltage higher than the threshold for determining the Hi level of the MCU 130 is input to its base.
[0092] Therefore, in the rotation position detection device 100M1, when the code plate 110 rotates in the positive direction and enters period (4) from period (3), input A based on output signal A transitions to a Hi level, and then the buffer transistor 123 turns off, causing input B based on output signal B to transition to a Hi level. In other words, it is possible to suppress the occurrence of a state where output signal A is at a Low level and output signal B is at a Hi level during the process of the code plate 110 rotating in the positive direction and entering period (4) from period (3).
[0093] Therefore, the rotational position detection device 100M1 can suppress the MCU 130 from mistakenly detecting a change from period (3) to period (2) when the code plate 110 rotates in the positive direction from period (3).
[0094] Furthermore, during the process in which the code board 110 rotates in the positive direction and enters period (3) from period (4), a state may occur where output signal A is at a high level and output signal B is at a low level. However, the MCU 130 can be set to ignore this state where output signal A is at a high level and output signal B is at a low level. In this way, even if a state occurs where output signal A is at a high level and output signal B is at a low level, the rotation position detection device 100M1 can appropriately detect the rotation position of the code board 110.
[0095] <Effect> The rotational position detection device 100M1 includes a buffer transistor 123 having an emitter connected to the power supply Vcc and a collector connected to the anode of the second photodiode 122A. The anode of the first photodiode 121A is connected to the power supply Vcc, the cathode of the first photodiode 121A is connected to GND, the emitter of the first phototransistor 121B is connected to GND, the collector of the first phototransistor 121B is connected to the power supply Vcc and the base of the buffer transistor 123, the cathode of the second photodiode 122A is connected to GND, the collector of the second phototransistor 122B is connected to the power supply Vcc, and the emitter of the second phototransistor 122B is connected to GND. The output signal is a signal representing the potential of the collector of the first phototransistor 121B and the potential of the collector of the second phototransistor 122B.
[0096] Therefore, by having the output signal transition through three states, a rotational position detection device 100M1 with good tracking ability for rotational movement can be provided. In addition, the rotational position detection device 100M1 can suppress false detection by the MCU 130 during the process in which the code plate 110 rotates in the positive direction and enters period (3) from period (4).
[0097] <Second Modification> Figure 7 shows an example of the circuit configuration of the rotational position detection device 100M2 of the second modification of the embodiment.
[0098] The rotational position detection device 100M2 has a configuration that is modified from the output unit 120 of the rotational position detection device 100 shown in Figure 2 by adding a drive transistor 124 and a PWM (Pulse Width Modulation) drive unit 124A, removing connection point 125B and wiring 126B, and changing the connection between the cathode of the first photodiode 121A and the collector of the second phototransistor 122B.
[0099] The drive transistor 124 has its emitter connected to GND, its collector connected to the cathode of the first photodiode 121A and the collector of the second phototransistor 122B, and its base connected to the output terminal of the PWM drive unit 124A.
[0100] The PWM drive unit 124A is a drive circuit that outputs a PWM signal having a duty cycle corresponding to the drive signal output from the MCU 130 to the base of the drive transistor 124.
[0101] <Operation of Rotation Position Detection Device 100M2> Figures 8A, 8B, 9A, 9B, 10A, and 10B illustrate an example of three state transitions for input A of the rotation position detection device 100M2. Figures 8A, 9A, and 10A show the presence or absence of the cutoff section 111 in the first photointerrupter 121 and second photointerrupter 122 of the circuit diagram in Figure 7, and the operation of the first photointerrupter 121 and second photointerrupter 122. In addition to on and off, the operation of the first photointerrupter 121 and second photointerrupter 122 also shows PWM drive, which is a state driven by a PWM signal. Figures 8B, 9B, and 10B show the state transitions of input A.
[0102] The MCU 130 detects the rotational position of the code board 110 based on input A generated from output signal A. Input A transitions through four different states over periods (1) to (4) shown in Figures 8B, 9B, and 10B. Periods (1) to (4) are the same as periods (1) to (4) explained using Figures 3A, 3B, 4A, 4B, 5A, and 5B.
[0103] <Periods (1) and (4)> The state shown in Figure 8A is the state during period (1) when the first photointerrupter 121 and the second photointerrupter 122 are blocked by the blocking unit 111, and during period (4) when the first photointerrupter 121 is blocked by the blocking unit 111 and the second photointerrupter 122 is not blocked by the blocking unit 111.
[0104] During periods (1) and (4), the first photodiode 121A is intermittently turned on by PWM drive, but the first phototransistor 121B is turned off because it does not receive light, so the second photodiode 122A is turned off. For this reason, the second phototransistor 122B is turned off during both the period (1) when the second photointerrupter 122 is blocked by the blockage unit 111 and the period (4) when the second photointerrupter 122 is not blocked by the blockage unit 111.
[0105] Based on the above, during periods (1) and (4), input A is at a high level.
[0106] <Period (2)> The state shown in Figure 9A is the state during period (2) when the first photointerrupter 121 is not blocked by the blocking unit 111, and the second photointerrupter 122 is blocked by the blocking unit 111.
[0107] During period (2), the first photodiode 121A is intermittently turned on by PWM drive, and the first phototransistor 121B is intermittently turned on by intermittent light reception. Since the first phototransistor 121B is effectively driven by PWM, it is described as being driven by PWM.
[0108] The second photodiode 122A is intermittently turned on by the intermittently turned on of the first phototransistor 121B. The second photodiode 122A is effectively PWM driven, and is therefore described as PWM driven. However, the second phototransistor 122B is not receiving light and is therefore turned off.
[0109] Therefore, during period (2), input A intermittently alternates between a low level and a high level using a pulse waveform obtained by inverting the PWM signal.
[0110] <Period (3)>
[0111] The state shown in Figure 10A is the state during the period (3) when neither the first photointerrupter 121 nor the second photointerrupter 122 is interrupted by the interruption unit 111.
[0112] During period (3), when the first photodiode 121A is turned on for the first time by PWM drive, the first phototransistor 121B receives light and turns on, and the second photodiode 122A turns on (lights up). Then, the second phototransistor 122B receives light and turns on.
[0113] When the second phototransistor 122B is turned on (conducting), current flows from the cathode of the first photodiode 121A through the second phototransistor 122B to GND. Therefore, instead of being turned on intermittently by PWM drive as in periods (1), (2), and (4), it is turned on continuously. That is, in period (3), the first photodiode 121A is latched in the ON state.
[0114] Based on the above, during period (3), the first photodiode 121A is latched in the ON state, and input A is at a Low level.
[0115] In the rotational position detection device 100M2, input A transitions through three states as described above. In other words, the output signal A of the rotational position detection device 100M2 transitions through three states.
[0116] <Effect> The rotational position detection device 100M2 includes a PWM-driven drive transistor 124. The anode of the first photodiode 121A is connected to the power supply Vcc, the cathode of the first photodiode 121A is connected to the collector of the drive transistor 124, the emitter of the drive transistor 124 is connected to GND, the emitter of the first phototransistor 121B is connected to GND, the collector of the first phototransistor 121B is connected to the cathode of the second photodiode 122A, the anode of the second photodiode 122A is connected to the power supply Vcc, the collector of the second phototransistor 122B is connected to the cathode of the first photodiode 121A and the collector of the drive transistor 124, the emitter of the second phototransistor 122B is connected to GND, and the output signal of the output unit 120 is a signal representing the potential of the cathode of the second photodiode 122A. The second photodiode 122A is connected so that it can be lit when the first phototransistor 121B is ON. Therefore, when the first phototransistor 121B is OFF, the level of the output signal based on the operating state of the second photointerrupter 122 will be the same whether the second photointerrupter 122 is blocked by the blockage unit 111 or not.
[0117] Therefore, by having the output signal transition through three states, a rotational position detection device 100 with good tracking ability for rotational movement can be provided. In addition, current consumption can be suppressed by driving the first photodiode 121A with PWM. Furthermore, by using a PWM-driven drive transistor 124, the input A in period (2) becomes a PWM-formatted signal, thus suppressing erroneous detection of the rotational direction.
[0118] Furthermore, when the drive transistor 124 is PWM driven, the first photodiode 121A lights up, the first phototransistor 121B turns on, and the second photodiode 122A lights up. When the second phototransistor 122B turns on, current flows from the first photodiode 121A to the second phototransistor 122B, causing the first photodiode 121A to light up. Therefore, in period (3), the input A remains constant at the Low level, making it possible to distinguish between the transition from period (3) to period (4) and the transition from period (3) to period (2).
[0119] Although exemplary embodiments of the rotational position detection device and position detection device of this disclosure have been described above, this disclosure is not limited to the specifically disclosed embodiments, and various modifications and changes are possible without departing from the scope of the claims.
[0120] This international application claims priority based on Japanese Patent Application No. 2025-005732, filed on 15 January 2025, the entire contents of which are incorporated herein by reference.
[0121] 100, 100M1, 100M2 Rotation position detection device 110 Code board 111 Blocking section 112 Transmitting section (example of non-blocking section) 120 Output section 121 First photointerrupter 121A First photodiode 121B First phototransistor 122 Second photointerrupter 122A Second photodiode 122B Second phototransistor 123 Buffer transistor 124 Drive transistor 124A PWM drive section 125A, 125B Connection points 126A, 126B Wiring 130 MCU 130A, 130B Input port
Claims
1. A rotational position detection device comprising: a cord plate having a light-blocking section that blocks light and a non-blocking section that transmits or reflects light, and which rotates together with a rotating member; an output section that outputs an output signal corresponding to the rotation of the cord plate; and a control section that acquires the output signal and detects the rotational position of the cord plate, wherein the output section comprises a first photointerrupter having a first photodiode and a first phototransistor, and a second photointerrupter having a second photodiode and a second phototransistor, the first photointerrupter and the second photointerrupter being connected such that the second photodiode can be lit when the first phototransistor is on, and the output signal transitions through three states.
2. The rotational position detection device according to claim 1, wherein the anode of the first photodiode is connected to a power supply, the cathode of the first photodiode is connected to a reference potential point, the emitter of the first phototransistor is connected to a reference potential point, the collector of the first phototransistor is connected to the cathode of the second photodiode, the anode of the second photodiode is connected to a power supply, the collector of the second phototransistor is connected to a power supply, the emitter of the second phototransistor is connected to a reference potential point, and the output signal is a signal representing the potential of the cathode of the second photodiode and the potential of the collector of the second phototransistor.
3. The rotational position detection device according to claim 1, further comprising a buffer transistor having an emitter connected to a power supply and a collector connected to the anode of the second photodiode, wherein the anode of the first photodiode is connected to a power supply, the cathode of the first photodiode is connected to a reference potential point, the emitter of the first phototransistor is connected to a reference potential point, the collector of the first phototransistor is connected to a power supply and the base of the buffer transistor, the cathode of the second photodiode is connected to a reference potential point, the collector of the second phototransistor is connected to a power supply, the emitter of the second phototransistor is connected to a reference potential point, and the output signal is a signal representing the potential of the collector of the first phototransistor and the potential of the collector of the second phototransistor.
4. The rotational position detection device according to claim 1, further comprising a PWM-driven drive transistor, wherein the anode of the first photodiode is connected to a power supply, the cathode of the first photodiode is connected to the collector of the drive transistor, the emitter of the drive transistor is connected to a reference potential point, the emitter of the first phototransistor is connected to a reference potential point, the collector of the first phototransistor is connected to the cathode of the second photodiode, the anode of the second photodiode is connected to a power supply, the collector of the second phototransistor is connected to the cathode of the first photodiode and the collector of the drive transistor, the emitter of the second phototransistor is connected to a reference potential point, and the output signal of the output unit is a signal representing the potential of the cathode of the second photodiode.
5. The rotational position detection device according to claim 4, wherein the drive transistor is PWM driven so that the first photodiode lights up, the first phototransistor turns on so that the second photodiode lights up, and when the second phototransistor turns on, current flows from the first photodiode to the second phototransistor so that the first photodiode lights up.
6. The rotational position detection device according to any one of claims 1 to 5, wherein the plurality of blocking portions and the plurality of non-blocking portions are alternately provided in the circumferential direction of the code plate, and if the pitch of the non-blocking portions in the circumferential direction is L, then the length of the non-blocking portions in the circumferential direction is L / 3, and the distance between the first photointerrupter and the second photointerrupter in the circumferential direction is L / 3.
7. The rotational position detection device according to any one of claims 1 to 6, wherein the three states of the output signal are a first state, a second state, and a third state, the first state being a state in which the cutoff portion is located between the first photodiode and the first phototransistor and between the second photodiode and the second phototransistor, and the cutoff portion is located between the first photodiode and the first phototransistor and the non-cutoff portion is located between the second photodiode and the second phototransistor, the second state being a state in which the non-cutoff portion is located between the first photodiode and the first phototransistor and the cutoff portion is located between the second photodiode and the second phototransistor, and the third state being a state in which the non-cutoff portion is located between the first photodiode and the first phototransistor and between the second photodiode and the second phototransistor.
8. The rotational position detection device according to claim 7, wherein the state in the first state in which the cutoff portion is located between the first photodiode and the first phototransistor, and the non-cutoff portion is located between the second photodiode and the second phototransistor, is a state in which the first phototransistor is turned off, causing the second photodiode to be in a non-lit state.
9. A position detection device comprising: a code board having a light-blocking section that blocks light and a light-transmitting or light-reflecting section, and movable in the direction connecting the light-blocking section and the light-reflecting section; an output section that outputs an output signal corresponding to the position of the code board; and a control section that acquires the output signal and detects the position of the code board, wherein the output section comprises a first photointerrupter comprising a first photodiode and a first phototransistor, and a second photointerrupter comprising a second photodiode and a second phototransistor, the first photointerrupter and the second photointerrupter being connected such that the second photodiode can be lit when the first phototransistor is on, and the output signal transitions through three states.