JP4204568B2 - Rotational position detector for electric motor - Google Patents

Description

  The present invention relates to a rotational position detection device for an electric motor that can absolutely detect the rotational position of a rotational shaft of the electric motor.

In many cases, it is necessary to detect the position of the rotation position of an electric motor (motor). For this reason, the electric motor may incorporate a rotation sensor for detecting the absolute rotational position of the rotation shaft. However, the rotation sensor that detects the absolute position is expensive, and there is a demand to detect the absolute position by using an inexpensive encoder that detects the relative rotation position. As such a thing, there exists a thing as described in the following [patent document 1].
JP 2004-56858 A

  In the device described in [Patent Document 1], an encoder is attached to the rotation shaft of the motor, and includes means for storing the target position of the encoder set by the target setting means. Then, at the time of starting the motor, the initial position alignment of the rotational position of the motor is performed by setting the already stored target position to the target position at the time of starting the motor. However, since the encoder that detects the relative position is used, learning (specification) of the starting position is required before the target position is set. In addition, since it is necessary to always store the target position in the storage means, it is not possible to cope with the lack of memory capacity. Accordingly, an object of the present invention is to provide a rotational position detection device for an electric motor that can always accurately detect the rotational position of the rotational shaft of the electric motor using an inexpensive encoder that detects the relative position.

An apparatus for detecting a rotational position of an electric motor according to claim 1 is based on an output of the electric motor, a relative encoder for detecting a relative rotational position of the rotational shaft of the electric motor, and a predetermined rotational position of the rotational shaft. A detecting means for detecting a rotational position of the rotating shaft; a gear connected to the rotating shaft, which is in a state where it does not move when the electric motor is not energized; and the rotating shaft is configured to stop the power supply to the motor; the power supply to the motor is stopped after being rotated in a predetermined rotational position, when the power supply start to the electric motor, and a control means for performing the starting control for rotating the rotary shaft to a predetermined position, the control means When the power supply stop is normally performed, the startup control is not performed. When the power supply stop is not normally performed, the startup control is performed .

According to a second aspect of the present invention, in the rotational position detecting device for the electric motor according to the first aspect, the judging means for judging whether or not the power supply to the electric motor is stopped in a state where the rotating shaft is rotated to a predetermined position. When the determining means determines that the power supply to the motor is not stopped with the rotating shaft rotated to a predetermined position, the control means mechanically restricts the rotation of the rotating shaft. The electric motor is driven to a position where the rotation is performed, and the detection means detects the rotational position of the rotation shaft on the basis of the position of the encoder at a position where the rotation of the rotation shaft is mechanically restricted.
According to a third aspect of the present invention, in the motor rotational position detecting device according to the first or second aspect, the motor variably controls the engine valve lift amount according to the rotational position of the rotating shaft.

According to the first aspect of the present invention, when the motor is stopped, the control means always rotates the rotating shaft to a predetermined position. Further, the rotating shaft is not rotated by the gear while the electric motor is stopped. For this reason, at the time of starting the electric motor, the rotation shaft is always in a predetermined position, and the absolute rotation position of the rotation shaft can always be accurately detected by the predetermined position and the relative rotation position detected by the encoder. . In addition, it is possible to perform the start control in consideration of a case where the motor is not normally stopped due to a sudden power interruption.

According to the rotation position detection device for an electric motor according to claim 2, the determination means determines whether or not the rotation shaft has been rotated to a predetermined position when the electric motor is stopped. For example, when the electric motor is not normally terminated, the rotating shaft may not be rotated to a predetermined position when the electric motor is stopped. In such a case, the absolute rotation position of the rotation shaft cannot be detected because the rotation shaft is not in a predetermined position when the electric motor is started. Therefore, here, when it is determined that the power supply to the motor has not been stopped when the rotating shaft is in a predetermined position, the motor is driven to a position where the rotation of the rotating shaft is mechanically restricted, and this The rotational position of the rotary shaft is detected based on the position of the encoder at the position. By doing in this way, the absolute rotation position of a rotating shaft can be detected correctly. The mechanically restricted position is, for example, a position where the rotation shaft cannot be rotated any further by the gear.
According to the rotational position detection device for an electric motor according to claim 3, the valve lift amount of the engine can be accurately controlled.

  An embodiment of a rotational position detection device for an electric motor according to the present invention will be described below. FIG. 1 shows a configuration diagram of the detection apparatus of the present embodiment. The electric motor (motor) 1 of this embodiment is mounted on a vehicle driven by an internal combustion engine (engine), and functions as an actuator for variably controlling the valve lift amount of the engine. Since the variable valve lift control mechanism itself is not directly related to the detection device of the present invention, detailed description thereof is omitted here.

  However, during variable control of the valve lift amount, the control shaft is moved forward and backward, and the valve lift amount is changed by the forward and backward movement of the control shaft. In the motor 1 in which the detection device of the present embodiment is incorporated, the rod is moved back and forth. In addition, since the detection apparatus according to the present embodiment is mounted on a vehicle, power supply to the motor 1 may be interrupted, or there may be an unexpected interruption of power supply due to an engine stall or the like. In the detection apparatus of the embodiment described below, consideration is given to such a case.

  As shown in FIG. 1, the detection device of the present embodiment detects the rotational position of the motor 1. The motor 1 includes a rotating shaft 2, and a gear (differential roller gear) 3 having a structure that does not move by an external force is connected to the rotating shaft 2. The motor 1 incorporates a relative (incremental) encoder 4 that detects a relative rotational position of the rotary shaft 2. The motor 1 is controlled by the ECU 5. A power line (drive signal line) of the motor 1 is connected to a CPU 7 in the ECU 5 via a pre-driver 6 in the ECU 5. The pre-driver 6 that has received the drive signal generated by the ECU 7 supplies power to the motor 1 according to the drive signal and controls the motor 1.

  Further, the above-described encoder 4 is also connected to the CPU 7 in the ECU 5, and the detection result of the encoder 4 is also processed in the ECU 5. Further, a non-volatile memory 8 for storing information necessary for controlling the rotational position of the motor 1 (rotating shaft 2) using the detection result of the encoder 4 is also built in the ECU 5.

  Next, the structure of the motor 1 will be described in more detail with reference to FIG. As described above, the motor 1 is a brushless motor, and is fixed to the cam carrier 9 that holds the valve camshaft as an actuator for variably controlling the cam lift amount of the engine. Inside the body 10 of the motor 1, a stator 11 and a rotor 12 that are main components of the motor 1 are disposed. The stator 11 is fixed to the inner wall of the body 10. The rotor 12 is fixed on the outer peripheral surface of the cylindrical roller gear 13. The roller gear 13 is rotatably held inside the body 10 by a pair of bearings 14.

  The roller gear 13 functions as a rotating shaft (output shaft) of the motor 1 having the stator 11 and the rotor 12. When the motor 1 is driven to rotate, the roller gear 13 rotates and the control shaft 15 moves forward and backward in the axial direction. However, even if the control shaft 15 is moved in the axial direction when the motor 1 is stopped, it does not move.

  At one end of the roller gear 13, a multi-pole magnet 16 arranged in an annular shape is attached. A Hall IC 17 serving as a magnetic sensor is disposed at a position facing the magnet 16. The position of the Hall IC 17 is fixed with respect to the body 10. When the multi-pole magnet 16 is rotated by rotating the roller gear 13, the magnetic flux passing through the Hall IC 17 is changed accordingly. The rotational position of the roller gear 13 is detected by using the Hall IC 17 for this magnetic flux change. That is, the magnet 16 and the Hall IC 17 function as an encoder. The ECU 5 functions as a detection unit, a control unit, and a determination unit.

  Control of the motor 1 by the detection device having the above-described configuration will be described based on the flowcharts of FIGS. 3 and 4. First, the control at the end of the end drive of the motor 1 will be described based on the flowchart of FIG. At the end of driving of the motor 1, a driving end signal is generated by the CPU 7 in the ECU 5. When this drive end signal is generated, the pre-driver receives it and drives the motor 1 to move the roller gear 13, that is, the rotation shaft of the motor 1 to a predetermined rotation position (step 300). Since the description here is at the end, the absolute rotational position of the roller gear 13 is already detectable, and the predetermined position can be detected from the detection value of the encoder described above. .

  Alternatively, the stroke amount of the control shaft 15 has a mechanical limit, and any of the limit positions may be set as the predetermined position. In this case, the motor 1 may be driven until the control shaft 15 reaches the limit position (until no rotation is detected by the encoder). In the case of this embodiment, the position where the member 18 in FIG. 2 contacts the cam carrier 9 or the holder 19 is the stroke limit of the control shaft 15. In this way, when the roller gear 13 (the rotation shaft of the motor 1) is moved to the predetermined rotation position, the normal end flag is set to ON (step 310). This flag is recorded in the nonvolatile memory 8 in the ECU 5 described above.

  After step 310, power supply to the motor 1 is stopped (step 320). At this time, the rotational position of the motor 1 is always at a predetermined position by the processing of step 300, and the position does not move due to the structure of the roller gear 13 while the motor 1 is stopped. For this reason, the motor 1 can always be driven from a predetermined position when the motor 1 is started next time, and it is not necessary to learn the reference position every time the motor 1 is started.

  As described above, the motor 1 of the present embodiment functions as an actuator that controls the valve lift amount of the engine. The motor 1 is started at the same time as the engine is started. However, when the valve lift amount is not a desired amount when the engine is started, the engine does not start normally. At this time, if the rotational position of the motor has to be learned each time, there will be a time lag in starting the engine. However, according to this embodiment, since the rotational position can be grasped simultaneously with the start-up of the motor 1, this does not occur.

  However, as described above, since it is an in-vehicle device, there is a possibility that unexpected power interruption may occur. In such a case, the control of FIG. 3 is not performed normally, and the rotational position of the motor 1 is set to a predetermined position at the start. It may not be. Therefore, in the present embodiment, start control is performed in consideration of such a situation. Next, the start control of the motor 1 will be described with reference to FIG. When there is a start command for the motor 1, the CPU 6 reads the normal end flag stored in the nonvolatile memory 8. Then, it is determined whether or not the read normal end flag is ON (step 400).

  If step 400 is affirmed, it can be determined that the rotational position of the motor 1 is at a predetermined position, and thus the control of the motor 1 is started as it is (the startup control is terminated). On the other hand, if step 400 is negative, it can be estimated that step 300 in the flowchart of FIG. 3 has not been executed. In this case, the motor 1 is driven to a position where the rotation of the roller gear 13 (the rotation shaft of the motor 1) is restricted (the limit position described above) (step 420). At this time, since the relative rotational position can be detected by the encoder, the limit position can be detected when the encoder stops detecting the rotation.

  After step 420, the limit position is set as a reference position (step 430), and thereafter the absolute rotational position of the motor 1 can be detected by the encoder. That is, the ECU 5 uses the normal end flag to determine whether or not the power supply is stopped in a state where the rotation shaft of the motor 1 is rotated to a predetermined position.

  The present invention is not limited to the embodiment described above. For example, in the above-described embodiment, the present invention is applied to detect the rotational position of an electric motor as an actuator that controls the valve lift amount of the engine, but the present invention is not limited to such an application.

It is a block diagram of one Embodiment of the detection apparatus of this invention. It is sectional drawing of a motor. It is a flowchart of the end time control. It is a flowchart of control at the time of starting.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Motor, 2 ... Rotating shaft, 3, 13 ... Differential roller gear (rotating shaft), 4 ... Encoder, 5 ... ECU, 6 ... Pre-driver, 7 ... CPU, 8 ... Non-volatile memory, 11 ... Stator, 12 ... Rotor, 15 ... control shaft, 16 ... magnet (encoder), 17 ... Hall IC (encoder).

Claims (3)

An electric motor,
A relative encoder for detecting the relative rotational position of the rotating shaft of the electric motor;
In a rotational position detection device for an electric motor, comprising: a detecting means for detecting a rotational position of the rotary shaft based on an output of the encoder with a predetermined rotational position of the rotary shaft as a reference ;
A gear connected to the rotating shaft and in a state where it does not move when the electric motor is in a non-energized state, and restricts rotation of the rotating shaft;
Upon stoppage of power supply to the motor, rotating the rotary shaft stops power supply to the motor after rotation at the predetermined rotational position, when the power supply start to the electric motor, the rotary shaft to a predetermined position and a control means for controlling startup to,
The control means does not perform the start-up control when the power supply stop is normally performed, and performs the start-up control when the power supply stop is not normally performed. Rotation position detection device. A judgment means for judging whether power supply to the electric motor is stopped in a state in which the rotary shaft is rotated to the predetermined position;
When the determination means determines that power supply to the electric motor is not stopped in a state where the rotation shaft is rotated to the predetermined position,
The control means drives the electric motor to a position where rotation of the rotary shaft is mechanically restricted,
The rotation position of the electric motor according to claim 1, wherein the detection unit detects a rotation position of the rotation shaft with reference to a position of the encoder at a position where rotation of the rotation shaft is mechanically restricted. Detection device.   3. The electric motor rotational position detecting device according to claim 1, wherein the electric motor variably controls an engine valve lift amount according to a rotational position of the rotating shaft.

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