Pulse signal generator

Abstract

To enable transmission of a plurality of pieces of information requiring synchronization on one signal line in PWM communication.SOLUTION: In a control device for communicating with external by generating a pulse signal, the pulse signal is generated as follows. At first, the voltage level of the pulse signal is changed from a first level to a second level, at occurrence of each predetermined event occurring periodically. Then, the voltage level is maintained at the second level until a period corresponding current state elapses within periods defined in different lengths respectively corresponding to a plurality of states mutually exclusive occurring along with the predetermined event. Then, the voltage level is changed back to the first level after elapsing the period.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a device for generating pulse signals transmitted and received in PWM communication. [Background technology]

[0002] An electric variable valve timing (VVT) mechanism adjusts the opening and closing timing of the intake or exhaust valves of a vehicle's internal combustion engine by driving a motor to change the relative rotational phase of a camshaft with respect to the crankshaft. In one example of such a VVT mechanism, a motor rotation angle signal and rotation direction signal are sent from the motor driver (lower controller) to an electronic control unit (upper controller). The electronic control unit then calculates the target rotation speed of the motor and feeds it back to the driver to control the motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-136007 Summary of the Invention [Problem to be solved by the invention]

[0004] To reduce the cost of VVT mechanisms, a centralized configuration is sometimes adopted, concentrating the functions of the motor's lower-level controller in a higher-level controller. In this case, communication between the higher-level controller and the lower-level controller is often performed using low-function communication such as PWM (Pulse Width Modulation) communication. Conventional PWM communication methods require separate transmission of rotation angle and rotation direction signals, resulting in the installation of many signal lines. This can result in problems such as poor controllability and increased costs due to missynchronization of these signal information. These problems can occur not only in VVT mechanisms but also in other control devices that transmit and receive multiple pieces of information via PWM communication.

[0005] Therefore, an object of one aspect of the present invention is to enable a plurality of pieces of information requiring synchronization to be transmitted over a single signal line in PWM communication. [Means for solving the problem]

[0006] One aspect of the present invention is PWM A control device that generates a pulse signal and communicates with an external device, The electric motor rotates a specified angle Each time, PWM Switches the voltage level of the pulse signal from the first level to the second level When the electric motor is rotating in the forward direction, The voltage level is set to the second level. 1st period Maintain and No. 1 After a period of time has elapsed, the voltage level is returned to the first level. On the other hand, when the electric motor is rotating in the reverse direction, the voltage level is maintained at the second level for a second period different from the first period, and after the second period has elapsed, the voltage level is returned to the first level, thereby generating the PWM pulse signal including information on the rotation angle and rotation direction of the electric motor. It is configured as are. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to transmit a plurality of pieces of information requiring synchronization over a single signal line. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a vertical cross-sectional view showing an example of a VVT mechanism. [Figure 2] 2 is a cross-sectional view taken along the line AA in FIG. 1. [Figure 3] 2 is a cross-sectional view of FIG. 1 taken along line B-B. [Figure 4] FIG. 2 is a diagram showing a schematic configuration of an electric motor. [Figure 5] FIG. 2 is a block diagram showing an example of a mechanism related to VVT control processing. [Figure 6] 4 is a timing chart illustrating an example of a sensor signal and a rotation signal when the electric motor is rotating in the forward direction. [Figure 7] 10 is a timing chart of an example of a sensor signal and a rotation signal when the electric motor is rotating in reverse. [Figure 8]4 is a flowchart showing an example of a VVT control process. [Figure 9] 4 is a flowchart showing an example of a VVT control process. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Fig. 1 is a partial vertical cross-sectional view showing the VVT ​​mechanism according to this embodiment, Fig. 2 is a cross-sectional view taken along line AA in Fig. 1, and Fig. 3 is a cross-sectional view taken along line BB in Fig. 1. Note that although this embodiment describes a VVT mechanism applied to the intake side of an internal combustion engine, it is also possible to apply it to the exhaust side.

[0010] The VVT ​​mechanism 100 includes a timing sprocket 1 (hereinafter referred to as sprocket 1) which is a driving rotor, a camshaft 2 which is rotatably supported on the cylinder head via bearings, and a phase change mechanism 3 which is disposed between the sprocket 1 and the camshaft 2 and which changes the relative rotational phase between the sprocket 1 and the camshaft 2 depending on the driving state of the engine.

[0011] The sprocket 1 is formed into an annular integral shape from an iron-based metal and comprises an annular sprocket body 1a and a gear portion 1b that is integrally formed on the outer periphery of the sprocket body 1a and receives rotational force from the engine crankshaft via a timing chain (not shown) wound around the outer periphery. An annular internal gear 5, which forms part of a reduction gear mechanism 13 (described later), is integrally provided at the front end of the sprocket body 1a. The internal gear 5 is integrally connected to the sprocket body 1a in the direction of the rotation axis, and has multiple wavy internal teeth 5a formed on its inner circumference. A plain bearing mechanism 6 is provided between the inner peripheral surface of the sprocket body 1a and the outer peripheral surface of a driven member 9, which is a driven rotating body fixed to one end 2a in the rotational axis direction of the camshaft 2. This plain bearing mechanism 6 supports the sprocket 1 on the outer periphery of the driven member 9 so that it can rotate relative to the driven member 9.

[0012] Furthermore, an annular retaining plate 8 is fixed to the rear end face of the sprocket body 1a, on the axially opposite side of the internal gear 5. A central hole 8a is formed through the center of the retaining plate 8, and the inner peripheral portion 8b on the side of this central hole 8a is positioned so as to cover one end opening of the bearing recess 10 of the plain bearing mechanism 6 on the camshaft 2 side. Furthermore, a stopper projection 8c that projects radially inward, i.e., toward the central axis, is integrally formed at a predetermined position on the inner peripheral edge of the central hole 8a of the retaining plate 8. This stopper projection 8c is formed in a substantially inverted trapezoid shape, with its tip surface formed in an arc that follows the arc-shaped inner peripheral surface of the stopper groove 4b of the adapter 4.

[0013] The adapter 4 is formed in a disk shape with an outer diameter slightly smaller than the inner diameter of the central hole 8a of the retaining plate 8, and fits into the central hole 8a. The adapter 4 also has an insertion hole 4a formed through its center, into which the cylindrical portion 9b of the driven member 9 is inserted, and a stopper groove 4b is provided at a predetermined position on its outer periphery. The stopper groove 4b is formed in an arc shape over a predetermined range along the outer periphery of the adapter 4, thereby mechanically restricting the relative rotational position of the driven member 9 (camshaft 2) with respect to the sprocket 1 on the maximum advance side or maximum retard side.

[0014] A front plate 15, which is a plate member, is provided on the front end surface of the sprocket 1 on the side of the internal gear 5. An insertion hole 15a is formed through the front plate 15, into which the eccentric shaft 21 is inserted. The sprocket body 1a including the internal gear 5, the front plate 15, and the retaining plate 8 are fixed together with bolts 7.

[0015] The camshaft 2 has two drive cams per cylinder on its outer periphery that open intake valves (not shown). The camshaft 2 also has an insertion hole 2b formed from the tip surface of one end 2a along the internal axial direction. A cam bolt 14 is fastened into this insertion hole 2b. The driven member 9 has a bolt insertion hole 9a formed at its central position through which a cam bolt 14 is inserted, and is fastened axially to the camshaft 2 by the cam bolt 14. A cylindrical portion 9b that protrudes toward the camshaft 2 is formed integrally with the edge of the bolt insertion hole 9a. A journal portion 11 that constitutes part of the sliding bearing mechanism 6 is also formed integrally with the driven member 9 on its outer circumferential surface.

[0016] As described above, the plain bearing mechanism 6 has an annular bearing recess 10 formed on the inner circumferential surface of the sprocket body 1a, and a journal 11 provided on the outer circumferential surface of the driven member 9 and positioned inside the bearing recess 10. The annular outer circumferential surface of the journal 11 is able to slide over the entire plain bearing surface 10a of the bearing recess 10.

[0017] The phase change mechanism 3 is mainly composed of an electric motor 12 arranged on the front end side of the driven member 9, and a speed reduction mechanism 13 that reduces the rotational speed transmitted from the electric motor 12 via the Oldham coupling and transmits the reduced speed to the camshaft 2.

[0018] The electric motor 12 is a three-phase brushless motor and has a cylindrical motor housing 16 with a bottom that is fixed to the chain case, a stator 17 that is fixed to the inner surface of the motor housing 16, a motor output shaft 18 that is arranged on the inner side of the stator 17, a rotor 19 that is fixed to the outer periphery of the motor output shaft 18, and a control mechanism 20 that is provided on the opposite side of the motor housing 16 from the sprocket 1.

[0019] The motor housing 16 has an internal storage space for accommodating the stator 17 and other components. A through-hole 16b, through which the motor output shaft 18 passes, is formed in approximately the center of the bottom wall 16a on the side of the reduction gear mechanism 13. The motor housing 16 and the casing 40 of the control mechanism 20 are fastened together with bolts 26 and are also fixed to a chain case (not shown). The stator 17 is molded by winding three-phase coils 17b around the outer periphery of an iron core 17a.

[0020] One end 18a of the motor output shaft 18, which is on the reduction mechanism 13 side in the rotational axis direction, protrudes from the through hole 16b via an oil seal 28. Meanwhile, the other end 18b of the motor output shaft 18 is rotatably supported by first and second ball bearings 42, 43, which are bearings provided in a casing 40 of the control mechanism 20. An intermediate member 27 is provided on one end 18a of the motor output shaft 18. This intermediate member 27 constitutes a part of an Oldham coupling, which is a coupling connected to the reduction mechanism 13, and is fixed to one end 18a of the motor output shaft 18.

[0021] The rotor 19 is formed in a cylindrical shape, and has a plurality of permanent magnets 19a fixed thereto. A circuit board 41 is fixed in the board housing space within the casing 40. The board housing space also houses and arranges a motor control device 120 (not shown in FIG. 1) that is electrically connected to the circuit board 41 and controls the driving of the electric motor 12, as well as electronic components such as a rotation angle sensor. Control by the motor control device 120 will be described in detail later.

[0022] The reduction mechanism 13 is provided axially separately from the electric motor 12, and each component is housed and disposed inside the sprocket 1 between the retaining plate 8 and the front plate 15. Specifically, the reduction mechanism 13 is mainly composed of a cylindrical eccentric shaft 21 which is an input shaft with a portion disposed inside the sprocket body 1a, a ball bearing 22 which is a bearing provided on the outer periphery of the eccentric shaft 21, a plurality of rollers 23 which are provided on the outer periphery of the ball bearing 22 and are held so as to be rollable within each internal tooth 5a of the internal gear 5, and a cage 24 which is provided integrally on the outer periphery of the driven member 9 and which holds the plurality of rollers 23 in the rolling direction while allowing them to move in the radial direction.

[0023] The eccentric shaft 21 has an eccentric shaft portion 21a arranged on the outer periphery of a needle bearing 25, which is a bearing provided on the outer periphery of the cam bolt 14, and a cylindrical connecting portion 21b integrally formed on the electric motor 12 side of the eccentric shaft portion 21a. The eccentric shaft portion 21a is formed in a cylindrical shape whose axial length is longer than the axial length of the needle bearing 25. The eccentric shaft portion 21a has a thickness that varies over the entire circumferential direction, and the axis of the eccentric shaft portion 21a is slightly eccentric with respect to the axis of the cam bolt 14.

[0024] The connecting portion 21b protrudes from inside the sprocket body 1a toward the electric motor 12 through the insertion hole 15a of the front plate 15. The connecting portion 21b, together with the intermediate member 27, constitutes an Oldham coupling. The needle bearing 25 has a plurality of needle rollers 25a that roll on the outer peripheral surface of the cam bolt 14, and a cylindrical shell 25b that is fixed to a stepped surface formed on the inner peripheral surface of the eccentric shaft portion 21a and has a plurality of grooves on its inner peripheral surface that hold the needle rollers 25a in a rotatable manner.

[0025] The ball bearing 22 is disposed radially so as to overlap the needle bearing 25, and is composed of an inner ring 22a, an outer ring 22b, balls 22c interposed between the inner ring 22a and the outer ring 22b, and a cage 22d that holds the balls 22c. The inner ring 22a is thicker and wider than the outer ring 22b and is press-fitted and fixed to the outer peripheral surface of the eccentric shaft portion 21a. In contrast, the outer ring 22b is not fixed in the axial direction and is free. The outer peripheral surfaces of the rollers 23 rollably abut against the outer peripheral surface of the outer ring 22b. An annular clearance is formed between the outer peripheral surface of the outer ring 22b and the inner surface of the cage 24. Therefore, the ball bearing 22 can move eccentrically in the radial direction via the clearance in response to the eccentric rotation of the eccentric shaft portion 21a.

[0026] The cage 24 is cylindrical and is provided integrally with the outer periphery of the driven member 9. The cage 24 also has a plurality of substantially rectangular roller holding holes 24b formed along the axial direction, which hold the plurality of rollers 23 so that they can roll freely. The total number of roller holding holes 24b (the number of rollers 23) is smaller than the total number of internal teeth 5a of the internal gear 5, thereby achieving a predetermined reduction ratio. Each roller 23 moves radially in accordance with the eccentric movement of the ball bearing 22 and is fitted into the internal teeth 5a of the internal gear 5. Each roller 23 is guided in the circumferential direction by both side edges of each roller holding hole 24b, and swings radially.

[0027] The operation and effects of the valve timing control device of this embodiment will be described below. When the sprocket 1 rotates via the timing chain in accordance with the rotational drive of the crankshaft, this rotational force is transmitted to the internal gear 5. The rotational force of this internal gear 5 is transmitted from each roller 23 to the cage 24 and the driven member 9 to the camshaft 2. As a result, the drive cam of the camshaft 2 opens and closes each intake valve.

[0028] At this time, the motor control device 120 energizes each coil 17b of the electric motor 12, thereby rotating the motor output shaft 18. When the motor output shaft 18 rotates in the same direction and at the same speed as the sprocket 1, the relative rotational phase of the camshaft 2 with respect to the sprocket 1, i.e., the relative rotational phase of the camshaft 2 with respect to the crankshaft, is maintained.

[0029] On the other hand, when the motor output shaft 18 rotates faster or slower than the sprocket 1, or when the motor output shaft 18 rotates in the opposite direction relative to the sprocket 1, the eccentric shaft portion 21a rotates eccentrically in response to the rotation of the motor output shaft 18. With each rotation of the motor output shaft 18, each roller 23 is guided radially by the cage 24, moves over one internal tooth 5a, and rolls onto the adjacent internal tooth 5a. The rollers 23 then repeat this process, rolling in the circumferential direction, and the rotation of the motor output shaft 18 is transmitted to the driven member 9 at a reduced speed. This shifts the relative rotational phase of the camshaft 2 with respect to the crankshaft to the advance or retard side, thereby changing the opening and closing timing of the intake valve. The reduction ratio at which the rotation of the motor output shaft 18 is transmitted to the driven member 9 can be set as desired, depending on the number of rollers 23, etc.

[0030] FIG. 4 is a diagram showing a schematic configuration of an example of the electric motor 12. As shown in FIG. Stator 17 has 12 iron cores 17a and coils 17b wound around each iron core 17a. Iron cores 17a are arranged at equal intervals of 30° from one another. Coils 17b include three U-phase coils, V-phase coils, and W-phase coils. U-phase coils, V-phase coils, and W-phase coils are wound around iron core 17a in this order so that they are adjacent to each other in a clockwise direction. That is, four U-phase coils, four V-phase coils, and four W-phase coils are arranged, and these four coils are arranged at 90° intervals from one another. When current flows through these U-phase coils, V-phase coils, and W-phase coils, magnetic flux is generated from the coils through which the current flows.

[0031] Rotor 19 has eight permanent magnets 19a embedded in a cylindrical iron core. Permanent magnets 19a are arranged at 45° intervals from one another so that the north pole and south pole are adjacent around the axis of rotor 19. In other words, the magnetic flux generated by permanent magnets 19a and acting between coil 17b changes periodically every time rotor 19 rotates 90°. Furthermore, three Hall sensors 50u, 50v, and 50w are arranged as rotation angle sensors in positions facing the permanent magnet 19a in the electric motor 12. The Hall elements of these Hall sensors 50u, 50v, and 50w are arranged at equal intervals of 120° from each other.

[0032] When current flows through coil 17b, magnetic flux generated from the U-phase coil, V-phase coil, and W-phase coil acts on permanent magnet 19a of rotor 19, generating rotational torque in rotor 19. This causes motor output shaft 18, which is fixed to rotor 19, to rotate. As rotor 19 rotates, Hall sensors 50u, 50v, and 50w detect changes in the magnetic field generated by permanent magnet 19a and output sensor signals. Drive control of electric motor 12 using these sensor signals will be described in detail later.

[0033] FIG. 5 is a block diagram showing an example of a mechanism related to the control process of the VVT ​​mechanism 100 according to this embodiment. An engine control module (ECM) 110 controls an engine (for example, an in-line four-cylinder gasoline engine) 200 mounted on a vehicle. The ECM 110 has a built-in microcomputer (not shown), and includes a target rotational speed calculation unit 111 and a rotational angle calculation unit 112 as components related to the control of the VVT ​​mechanism 100.

[0034] The target rotational speed calculation unit 111 receives rotational angle information of the camshaft 2 and the crankshaft detected by a cam angle sensor 201 and a crank angle sensor 202, respectively, provided in the engine 200. The target rotational speed calculation unit 111 also acquires torque-related information, such as the engine rotational speed, intake air flow rate for each cylinder, and accelerator opening, from various sensors. The target rotational speed calculation unit 111 also acquires current rotational angle information and rotational direction information of the electric motor 12 from a rotational angle calculation unit 112, which will be described later. Based on this information, the target rotational speed calculation unit 111 calculates a target relative rotational phase for the VVT ​​mechanism 100, and calculates a target rotational speed and a target rotational direction of the electric motor 12 for achieving this relative rotational phase. The target rotational speed calculation unit 111 then transmits the target rotational speed and target rotational direction information to the motor control device 120.

[0035] The rotation angle calculation unit 112 receives a rotation signal, which is a pulse signal including information on both the current rotation angle and rotation direction of the electric motor 12, from a rotation signal generation unit 122 of the motor control device 120, which will be described later. The rotation angle calculation unit 112 calculates the current rotation angle and rotation direction of the electric motor 12 based on the pulse signal including the rotation information. The calculation method will be described in detail later. The rotation angle calculation unit 112 then notifies the target rotation speed calculation unit 111 of the calculated current rotation angle and rotation direction of the electric motor 12.

[0036] The electric motor 12 has a stator 17, a rotor 19 (shown as a motor body 12a in FIG. 5), and a motor control device 120 that controls the rotation of the rotor 19. As described above, the electric motor 12 is provided with Hall sensors 50u, 50v, and 50w as rotation angle sensors. The motor control device 120 is a driver with a built-in microcomputer (not shown), and controls the rotation of the rotor 19 based on target rotational speed information and target rotational direction information of the electric motor 12 received from the ECM 110. Then, it transmits current rotational angle information and rotational direction information of the rotor 19 to the ECM 110. At this time, the ECM 110 and the motor control device 120 communicate with each other using PWM (Pulse Width Modulation).

[0037] The motor control device 120 includes a rotation control unit 121 and a rotation signal generation unit 122 . The rotation control unit 121 calculates an increase or decrease in the rotational torque of the electric motor 12 based on the target rotational speed and target rotational direction included in the signal received from the ECM 110 and the current rotational angle and rotational direction of the rotor 19 based on detection signals from the Hall sensors 50u, 50v, and 50w. The rotation control unit 121 is electrically connected to the U-phase coil, V-phase coil, and W-phase coil of the coil 17b via the inverter circuit 123. Based on the calculated increase or decrease in rotational torque, the rotation control unit 121 controls the on / off of the U-phase, V-phase, and W-phase switching elements of the inverter circuit 123, thereby controlling the supply of current to the U-phase coil, V-phase coil, and W-phase coil, thereby controlling the rotation of the rotor 19.

[0038] The rotation signal generating unit 122 generates a rotation signal, which is a pulse signal containing information on both the rotation angle and rotation direction of the rotor 19, based on the detection signals output from the Hall sensors 50u, 50v, and 50w, and outputs it to the ECM 110.

[0039] The processing in the rotation signal generation unit 122 will be described in detail below. Figures 6 and 7 are timing charts showing an example of the U-phase sensor signal, V-phase sensor signal, and W-phase sensor signal generated based on the magnetic fields detected by the Hall sensors 50u, 50v, and 50w, and the rotation signal generated by the rotation signal generation unit 122. The Hall sensors 50u, 50v, and 50w generate pulse signals of the U-phase sensor signal, V-phase sensor signal, and W-phase sensor signal through binarization processing based on the voltages output by the Hall elements when the magnetic fields are detected.

[0040] As described above, in the electric motor 12 of this embodiment, the eight permanent magnets 19a are arranged at 45° intervals from one another so that the north pole and south pole are adjacent to each other around the axis of the rotor 19. As a result, the voltage levels of the U-phase sensor signal, V-phase sensor signal, and W-phase sensor signal generated by the Hall sensors 50u, 50v, and 50w each switch from high to low or from low to high when the rotor 19 rotates 180 electrical degrees.

[0041] As described above, the Hall sensors 50u, 50v, and 50w are arranged at 120° intervals around the axis of the rotor 19. This causes the magnetic fields of the permanent magnet 19a detected by the Hall sensors 50u, 50v, and 50w to be shifted by 120° electrical degrees from one another. The phases of the detection signals output by the Hall sensors 50u, 50v, and 50w are also shifted by 120° electrical degrees from one another. Therefore, every time the rotation angle of the rotor 19 advances by 60° electrical degrees, the voltage level of one of the U-phase, V-phase, and W-phase sensor signals generated by the Hall sensors 50u, 50v, and 50w changes. By detecting a change in the voltage level of one of the U-phase, V-phase, and W-phase sensor signals, i.e., by detecting the pulse edges of these sensor signals, it is possible to detect that the rotor 19 has rotated 60° electrical degrees. This 60° electrical rotation of the rotor 19 is an example of a periodic occurrence of a predetermined event.

[0042] The rotation signal generation unit 122 detects the rotation direction of the rotor 19 based on the switching of the voltage levels of the U-phase sensor signal, V-phase sensor signal, and W-phase sensor signal. The sensor signal shown in FIG. 6 is a timing chart of an example of the sensor signal when the rotor 19 is rotating forward. In this example, as time passes from T1 to T7, the voltage levels of the U-phase sensor signal, V-phase sensor signal, and W-phase sensor signal switch from low to high in this order, resulting in rising edges. The rotation signal generation unit 122 determines that the rotor 19 is rotating forward when the edges of the U-phase sensor signal, V-phase sensor signal, and W-phase sensor signal rise in this order. Meanwhile, the sensor signal shown in FIG. 7 is a timing chart of an example of the sensor signal when the rotor 19 is rotating backward. In this example, as time passes from T1 to T7, the voltage levels of the W-phase sensor signal, V-phase sensor signal, and U-phase sensor signal switch from low to high in this order, resulting in rising edges. The rotation signal generator 122 determines that the rotor 19 is rotating in reverse when the edges of the U-phase sensor signal, V-phase sensor signal, and W-phase sensor signal rise in this order. Note that the forward or reverse rotation of the rotor 19 is an example of a plurality of mutually exclusive states that occur together with a predetermined event.

[0043] Then, based on the rotation angle and rotation direction of rotor 19 detected as described above, rotation signal generator 122 generates a rotation signal, which is a pulse signal including information on both the rotation angle and rotation direction. Specifically, as shown in Figures 6 and 7, when an edge of the pulse signal of any one of the U-phase sensor signal, V-phase sensor signal, and W-phase sensor signal is detected, rotation signal generator 122 switches the voltage level of the pulse signal of the rotation signal from low to high. In this case, the low level corresponds to the first level, and the high level corresponds to the second level.

[0044] At this time, the rotation signal generating unit 122 sets the length of the High-level period (pulse width) in one cycle of the rotation signal to different lengths depending on the direction of rotation of the motor. In the motor control device 120, periods of different lengths corresponding to the rotation directions of the motor, i.e., forward rotation and reverse rotation, are pre-set in the memory of the microcomputer. In this embodiment, as an example, the first period (t1) corresponding to forward rotation is set to 250 microseconds, and the second period (t2) corresponding to reverse rotation is set to 125 microseconds. When the rotor 19 is rotating forward, as shown in FIG. 6, the rotation signal generating unit 122 sets the period during which the High level is maintained to 250 microseconds, the first period (t1) corresponding to forward rotation. After the first period has elapsed, the rotation signal generating unit 122 returns the voltage level to a Low level. Furthermore, when the next pulse edge of the sensor signal output by any of the Hall sensors is detected, the rotation signal generating unit 122 again switches the voltage level from a Low level to a High level. The rotation signal generating unit 122 continuously generates a pulse signal of the rotation signal by repeating this switching of the voltage level. On the other hand, when the rotor 19 is rotating in the reverse direction, the rotation signal generating unit 122 maintains the high level for a second period (t2) of 125 microseconds corresponding to the reverse rotation, as shown in FIG. 7 . Then, after the second period has elapsed, the rotation signal generating unit 122 returns the voltage level to the low level. The rotation signal generating unit 122 outputs the rotation signal generated in this manner to the ECM 110.

[0045] Meanwhile, the rotation angle calculation unit 112 of the ECM 110 receives the rotation signal from the motor control device 120 and can calculate the rotation angle of the rotor 19 based on the switching of the voltage level in the rectangular wave of the pulse signal. Also, the lengths of periods corresponding to forward and reverse rotation are set in advance on the ECM 110 side, and the rotation angle calculation unit 112 can determine whether the rotation direction of the electric motor 12 is forward or reverse based on the length of the period of the high level in the pulse signal.

[0046] Next, among the mechanisms related to the control processing of the VVT ​​mechanism 100 described above, the processing executed by the rotation signal generating unit 122 of the motor control device 120, which generates a rotation signal indicating the current rotation angle and rotation direction of the electric motor 12, will be described with reference to the flowchart shown in FIG.

[0047] In step 101 (denoted as S101 in the figure, and the same applies below), the rotation signal generating unit 122 detects a change (edge) in the voltage level of any one of the U-phase sensor signal, V-phase sensor signal, and W-phase sensor signal generated by the Hall sensors 50u, 50v, and 50w. In step 102, the rotation signal generating unit 122 determines the rotation direction of the electric motor 12 based on the order (switching pattern) of the voltage levels of the U-phase sensor signal, V-phase sensor signal, and W-phase sensor signal as described above. In step 103, the rotation signal generating unit 122 determines whether the rotation direction of the electric motor 12 determined in step 102 is forward rotation or reverse rotation. If the rotation direction is forward rotation, the process proceeds to step 104, and if the rotation direction is reverse rotation, the process proceeds to step 105.

[0048] In step 104, the rotation signal generating unit 122 generates a rotation signal, defining a first period (t1) as a period during which the voltage level of the pulse signal is at a high level, and outputs the rotation signal to the ECM 110. Specifically, the rotation signal generating unit 122 switches the voltage level of the pulse signal from a low level to a high level, maintains the voltage level at the high level until the first period has elapsed, and switches the voltage level back to a low level after the first period has elapsed. In step 105, the rotation signal generating unit 122 generates a rotation signal for a second period (t2) during which the voltage level of the pulse signal is at a high level, and outputs the rotation signal to the ECM 110. Specifically, the rotation signal generating unit 122 switches the voltage level of the pulse signal from a low level to a high level, maintains the voltage level at the high level until the second period has elapsed, and switches the voltage level back to a low level after the second period has elapsed.

[0049] The rotation signal generating unit 122 repeats the processing of steps 101 to 105 to continuously output a rotation signal to the ECM 110. As described above, in the electric motor 12 of this embodiment, the voltage level of one of the U-phase sensor signal, V-phase sensor signal, and W-phase sensor signal changes when the rotor 19 rotates by 60 electrical degrees. Therefore, one pulse period in the rotation signal generated by the rotation signal generating unit 122 indicates that the electric motor 12 has rotated by 60 electrical degrees.

[0050] Next, among the mechanisms related to the control processing of the VVT ​​mechanism 100 described above, the processing executed by the rotation angle calculation unit 112 on the ECM 110 side, which receives a rotation signal indicating the current rotation angle and rotation direction of the electric motor 12 from the motor control device 120, will be described with reference to the flowchart shown in FIG. In step 201 , the rotation angle calculation unit 112 receives a pulse signal of a rotation signal indicating the current rotation angle and rotation direction of the electric motor 12 from the rotation signal generation unit 122 of the electric motor 12 . In step 202, rotation angle calculation unit 112 determines whether the high level period in one cycle of the pulse signal of the received rotation signal is the first period or the second period. If the high level period is the first period, the process proceeds to step 203, and if the high level period is the second period, the process proceeds to step 204.

[0051] In step 203, the rotation angle calculation unit 112 determines that the rotation direction of the electric motor 12 is forward rotation. In step 204, the rotation angle calculation unit 112 determines that the rotation direction of the electric motor 12 is reverse. In step 205, the rotation angle calculation unit 112 calculates the current rotation angle of the electric motor 12 based on the rotation signal. As described above, one period of the pulses of the rotation signal received from the rotation signal generation unit 122 indicates that the electric motor 12 has rotated by 60° in electrical angle. Based on this, the rotation angle calculation unit 112 can calculate the current rotation angle of the electric motor 12. Then, the rotation angle calculation unit 112 notifies the target rotation speed calculation unit 111 of information indicating the current rotation angle and rotation direction of the electric motor 12.

[0052] The target rotation speed calculation unit 111 of the ECM 110 calculates the current rotation speed of the electric motor 12 based on information indicating the current rotation angle and rotation direction of the electric motor 12 notified from the rotation angle calculation unit 112. The target rotation speed calculation unit 111 can calculate the rotation speed of the electric motor 12 by detecting a change in the angle of the rotation signal per unit time. Note that the rotation angle calculation unit 112 may perform the calculation of the rotation speed itself. The target rotation speed calculation unit 111 calculates a target rotation speed and a target rotation direction of the electric motor 12 using the rotation speed and rotation direction of the electric motor 12 and drive information received from the engine 200, including rotation angle information from the cam angle sensor 201 and the crank angle sensor 202. The target rotation speed calculation unit 111 then transmits the target rotation speed and target rotation direction to the rotation control unit 121 of the motor control device 120.

[0053] [Effects, Modifications, etc. of the Present Embodiment] As described above, according to this embodiment, when the motor control device 120 transmits the rotation angle and rotation direction of the electric motor 12 to the ECM 110 in the control of the electric motor 12 in the VVT ​​mechanism 100, a rotation signal is generated as follows. That is, a pulse signal is generated such that the length of the high-level period in one cycle varies depending on the rotation direction (forward or reverse) of the electric motor 12. As a result, the ECM 110 that receives the pulse signal can determine not only the rotation angle of the electric motor 12 but also the rotation direction of the electric motor 12 based on the length of the high-level period of the pulse signal. Therefore, it is possible to transmit rotation angle information and rotation direction information of the electric motor 12 via a single signal line in PWM communication. As a result, it is possible to reduce synchronization errors between the two pieces of information, which are caused by communication errors on each signal line, compared to when the rotation angle information and the rotation direction information are transmitted separately via multiple signal lines. This makes it possible to suppress errors that may occur in the ECM 110's calculation of the rotation angle of the electric motor 12 and in the calculation of the target rotation speed using the rotation angle information. Furthermore, reducing the number of signal lines in this way also contributes to cost reduction.

[0054] In the specific examples of the rotation signal shown in FIGS. 6 and 7, the first period (t1) corresponding to the electric motor 12 rotating forward is shorter than the second period (t2) corresponding to the electric motor 12 rotating reversely. However, these periods may be set to any lengths as long as they are different from each other. For example, the pulse signal may be generated so that the high-level period when the electric motor 12 is rotating reversely is longer than the high-level period when the electric motor 12 is rotating forwardly. In either case, it is desirable to set both the first period and the second period shorter than the length of one period in a state where the electric motor 12 rotates at the highest rotation speed, i.e., a state where switching of the sensor signal occurs most frequently and one period of the rotation information pulse signal is shortest. Furthermore, it is desirable to set the first period and the second period so that the ECM 110 can reliably determine the rotation direction of the electric motor 12, even taking into account response delays and signal detection delays of the circuits in the motor control device 120 and the ECM 110.

[0055] In this embodiment, the rotation signal generating unit 122 switches the voltage level of the rotation signal from low to high when an edge of the sensor signal is detected, but it may also switch it from high to low. In this case, the low level is maintained until a period corresponding to the rotation direction of the electric motor 12 has elapsed, and then the high level is restored, and this process is repeated repeatedly. In this case, the high level corresponds to the first level, and the low level corresponds to the second level.

[0056] Furthermore, a different duty ratio may be set for the first period corresponding to when the electric motor 12 is rotating forward and the second period corresponding to when it is rotating reversely, instead of the time lengths (250 microseconds and 125 microseconds) as in the examples shown in Figures 6 and 7. If a duty ratio is set, it is possible to avoid the risk that the first period or the second period will be longer than the period of the pulse signal when the electric motor 12 is rotating at the maximum speed.

[0057] Furthermore, instead of switching the voltage level of the rotation signal when an edge of the sensor signal from the Hall sensors 50u, 50v, and 50w is detected, the rotation signal generating unit 122 may perform the following control. That is, the rotation signal generating unit 122 may detect which open phases, to which no current is applied, and which phases are applied in the U-phase coil, V-phase coil, and W-phase coil of the electric motor 12, and detect that the electric motor 12 has rotated a predetermined angle based on this current application pattern. The voltage level of the rotation signal may then be switched based on the detection result. With this type of control, it is possible to generate a similar rotation signal even when the electric motor 12 is a sensorless motor that does not have the Hall sensors 50u, 50v, and 50w.

[0058] When the engine 200 is stopped, the VVT ​​mechanism 100 can control the electric motor 12 to press the camshaft against a stopper and lock the stopper on the retard side. If the crankshaft rotates reversely in this state, the electric motor 12 also rotates reversely. At this time, the ECM 110 can determine that the crankshaft is rotating reversely by detecting a change in the rotation direction of the electric motor 12 based on a rotation signal transmitted from the motor control device 120 of the electric motor 12. According to this embodiment, the motor control device 120 generates a pulse signal of the rotation signal as described above, thereby reducing missynchronization between the rotation angle information and the rotation direction information, and the ECM 110 can detect a change in the rotation direction of the electric motor 12 with more accurate timing. Therefore, reverse rotation of the engine 200 can be detected with high accuracy even if the crank angle sensor 202 does not have a reverse rotation detection function.

[0059] The pulse signal generation method described in this embodiment is not limited to application to communication between control devices in a VVT mechanism. This pulse signal generation method can be applied to various devices in which a predetermined event occurs periodically and multiple pieces of information related to the predetermined event, particularly multiple pieces of information that must be synchronized with each other, are communicated over a single signal line using PWM communication.

[0060] Furthermore, a person skilled in the art would easily understand that new embodiments can be created by omitting parts of the technical ideas of the above embodiments, combining parts of the ideas appropriately, or replacing parts of the ideas with well-known technology. [Explanation of symbols]

[0061] 100...VVT mechanism, 110...ECM, 111...target rotation speed calculation unit, 112...rotation angle calculation unit, 120...motor control device, 121...rotation control unit, 122...rotation signal generation unit, 12...electric motor, 17...stator, 19...rotor, 50v·50w·50u...Hall sensor

Claims

1. A control device that generates a PWM pulse signal and communicates with an external device, a control device configured to switch the voltage level of the PWM pulse signal from a first level to a second level each time the electric motor rotates by a predetermined angle, to maintain the voltage level at the second level for a first period when the electric motor is rotating in a forward direction, and to return the voltage level to the first level after the first period has elapsed, while maintaining the voltage level at the second level for a second period when the electric motor is rotating in a reverse direction, which is different from the first period, and to return the voltage level to the first level after the second period has elapsed, thereby generating the PWM pulse signal that includes information about the rotation angle and the rotation direction of the electric motor.

2. A control device as described in claim 1, wherein the first period and the second period are set to periods shorter than the period in which the electric motor rotates the specified angle when rotating at the maximum rotational speed.

3. 2. The control device according to claim 1, wherein the electric motor is a brushless motor, and when a voltage level of a detection signal output by a rotation angle sensor installed in the brushless motor is switched, it is detected that the electric motor has rotated a predetermined angle, and the voltage level of the PWM pulse signal is switched from the first level to the second level.

4. 4. The control device according to claim 1, wherein the period is set to one of a length of time or a duty ratio corresponding to each of the plurality of states.

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