Valve timing control device

Abstract

The present invention provides a valve timing control device that suppresses relative rotational phase displacement when the engine is stopped, thereby enabling rapid displacement to a target phase during engine startup. The valve timing control device includes a driving-side rotor A, a driven-side rotor B, gear mechanisms 25 and 30, an electric motor M capable of displacing the meshing position of the gear mechanisms 25 and 30 by rotating a rotational shaft Ma, and a control unit 10a for controlling the drive of the electric motor M. After the engine E stops, the control unit 10a intermittently energizes one phase of the electric motor M for a specified period of time.

Description

Technical Field

[0001] The present invention relates to a valve timing control device that sets the relative rotation phase between a driving-side rotating body and a driven-side rotating body by the driving force of an electric motor. Background Art

[0002] Conventionally, there is a known valve timing control device that includes a driving-side rotor that rotates synchronously with the crankshaft of an internal combustion engine about a rotational axis, a driven-side rotor that rotates coaxially with the rotational axis and integrally with a camshaft for opening and closing the valves of the internal combustion engine, and a three-phase electric motor that sets the relative rotational phase between the driving-side rotor and the driven-side rotor (for example, see Patent Document 1). This electric valve timing control device offers faster phase control responsiveness than a hydraulic valve timing control device and is effective in setting a relative rotational phase suitable for cranking the engine when starting the engine.

[0003] The valve timing control device described in Patent Document 1 includes a balancing mechanism, which balances the motor torque with the magnetic retaining torque (cogging torque) and the cam torque after the internal combustion engine stops, and a cancellation mechanism, which cancels the motor torque while the motor torque is balanced with the magnetic retaining torque and the cam torque. Specifically, Patent Document 1 describes a method for estimating the direction of the cam torque based on the amount of energization applied to the three-phase motor and the change in relative rotational phase. The three phases of the three-phase motor are energized to apply motor torque in a direction that counteracts the cam torque. The three phase energization is then gradually reduced to cancel the motor torque.

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-013975 Summary of the Invention

[0006] However, when the power to the three-phase motor is stopped, the inertial force that wants to continue rotating acts on the rotating shaft of the three-phase motor, and the rotating shaft continues to rotate until the inertial force is lower than the cogging torque and the cam torque. That is, in the valve timing control device described in Patent Document 1, even if the motor torque is eliminated in a state where the motor torque is balanced with the cam torque and the cogging torque, the rotating shaft of the three-phase motor will continue to rotate. As a result, dynamic friction dominates, and before a static friction state is formed in which the cogging torque exceeds the torque (generated torque) generated by the cam torque, etc., the relative rotation phase will continue to shift due to the rotation of the rotating shaft, so it takes a certain amount of time to set the optimal target phase for the next engine start.

[0007] Therefore, there is a need for a valve timing control device that can quickly shift the relative rotational phase to a target phase when the engine is started by suppressing the displacement of the relative rotational phase when the engine is stopped.

[0008] The characteristic structure of the valve timing control device involved in the present invention lies in the following aspects, which comprises: a driving side rotating body, a driven side rotating body, a gear mechanism, an electric motor and a control unit, the driving side rotating body rotates synchronously with the crankshaft of the internal combustion engine around the rotation axis; the driven side rotating body rotates integrally with the camshaft for opening and closing the valves of the internal combustion engine on the same axis as the rotation axis; the gear mechanism sets the relative rotation phase of the driving side rotating body and the driven side rotating body by shifting the meshing position; the electric motor can shift the meshing position of the gear mechanism by rotating the rotating shaft; the control unit controls the drive of the electric motor; after the internal combustion engine stops, the control unit intermittently performs control of one phase energization of the electric motor for a specified time.

[0009] When the internal combustion engine is stopped, even if the relative rotational phase is set to the optimal target phase for the next start, the inertia of the camshaft and the electric motor, which want to continue rotating, will exceed the cogging torque, preventing the camshaft from stopping. This cam torque will cause the relative rotational phase to shift. As a result, it will take some time to reach the optimal target phase the next time the internal combustion engine is started.

[0010] Therefore, in this structure, after the internal combustion engine stops, control is intermittently performed to energize one phase of the electric motor for a specified period of time. When energizing one phase, the motor's rotating shaft stops at the energized phase position, counteracting the cam torque and fixing the meshing position of the gear mechanism, thereby stopping the relative rotational phase shift. However, when the one-phase energization is released, the rotating shaft and camshaft resume rotation due to inertia and are subjected to the cam torque, causing the relative rotational phase to shift. While the motor's rotating shaft rotates, dynamic friction dominates, causing the relative rotational phase to shift. However, when the motor's cogging torque exceeds the torque generated by the cam torque, etc., a static friction state is generated, and the relative rotational phase shift stops.

[0011] Specifically, this configuration prevents relative rotational phase displacement by energizing one phase and intermittently energizing the one phase. This suppresses relative rotational phase displacement during the transition from a dynamic friction state to a static friction state. As a result, the relative rotational phase can be quickly shifted to the target phase upon the next start of the internal combustion engine. This ensures that the relative rotational phase is reliably shifted to the target phase suitable for cranking before the ignition switch is turned on and the engine begins cranking.

[0012] In this manner, it is possible to provide a valve timing control device that suppresses the displacement of the relative rotational phase when the engine is stopped and can quickly displace the valve timing to a target phase when the engine is started.

[0013] Another characteristic configuration is that the control unit controls the interval between the one-phase energization and the next one-phase energization based on time.

[0014] If the interval of energizing one phase is controlled based on time as in this configuration, the control form is simpler.

[0015] Another characteristic configuration is that the control unit controls an interval between the one-phase energization and the next one-phase energization based on the rotation angle of the electric motor.

[0016] By controlling the interval at which one phase is energized based on the motor's rotation angle, as in this configuration, the rotating shaft can be stopped at the moment one phase is energized, thereby reliably preventing any shift in the relative rotational phase. Furthermore, stopping the rotating shaft at the point where the cam torque and cogging torque are balanced effectively eliminates the cam torque and shortens the transition time from dynamic friction to static friction. Consequently, shifts in the relative rotational phase can be effectively suppressed.

[0017] Another characteristic configuration is that the control unit determines the phase of the electric motor to which the one-phase is energized based on the rotation angle.

[0018] By determining the phase of the electric motor to be energized in one phase based on the rotation angle as in this configuration, the time required for the rotation shaft to stop can be shortened, and the displacement of the relative rotation phase can be further suppressed.

[0019] Another characteristic configuration is that the control unit sequentially energizes each phase of the electric motor.

[0020] If one phase is energized in sequence of each phase as in this configuration, the stopped state of the rotating shaft can be effectively established even without detecting the rotation angle of the rotating shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a cross-sectional view and block diagram of the valve timing control device.

[0022] Figure 2 This is a conceptual diagram showing a control mode when the engine is stopped.

[0023] Figure 3 A diagram showing the control flow of the valve timing control device.

[0024] Figure 4This is a conceptual diagram showing the relationship between cogging torque and cam torque. DETAILED DESCRIPTION

[0025] An embodiment of a valve timing control device according to the present invention will be described below with reference to the accompanying drawings. In this embodiment, a valve timing control device 100 provided on the intake side of an engine E will be described as an example of a valve timing control device. However, the present invention is not limited to the following embodiment, and various modifications are possible without departing from the spirit and scope of the present invention.

[0026] like Figure 1 As shown, the valve timing control device 100 includes a driving-side rotor A, a driven-side rotor B, a phase control motor M, and an electric VVT (Variable Valve Timing) control unit 10. The driving-side rotor A rotates synchronously with a crankshaft 1 of an internal combustion engine E about a rotation axis X. The driven-side rotor B is arranged radially inward of the driving-side rotor A and rotates integrally with an intake camshaft 2 (an example of a camshaft) for valve opening and closing about the rotation axis X. The phase control motor M is a three-phase motor (an example of a motor) that sets the relative rotational phase between the driving-side rotor A and the driven-side rotor B. Hereinafter, the electric valve timing control device 100 may also be referred to as an "electric VVT."

[0027] The engine E is a four-stroke type, in which a piston 4 is housed in a plurality of cylinders 3 formed on a cylinder block, and the piston 4 is connected to a crankshaft 1 via a connecting rod 5. A timing chain 6 (which may also be a timing belt, etc.) is wound across an output sprocket 1S of the crankshaft 1 of the engine E and a drive sprocket 11S of the drive-side rotating body A. Thus, the rotation of the crankshaft 1 of the engine E is transmitted to the drive-side rotating body A. The drive of the engine E is controlled by an upper-level ECU (Electronic Control Unit) 50, which serves as a control device. The upper-level ECU 50 is composed of software or a collaboration of hardware and software, with a CPU (Central Processing Unit) and a memory as the core, which execute various processes.

[0028] Thus, when the engine E is driven, the entire valve timing control device 100 rotates about the rotation axis X. Furthermore, the driving force of the phase control motor M activates the phase adjustment mechanism C (described later), thereby displacing the driven-side rotor B relative to the driving-side rotor A in either the same direction or the opposite direction of rotation. This displacement sets the relative rotational phase between the driving-side rotor A and the driven-side rotor B, thereby controlling the opening and closing timing (opening and closing timing) of the intake valve 2B by the cam portion 2A of the intake camshaft 2.

[0029] It should be noted that the operation of displacing the driven-side rotating body B in the same direction as the rotation of the driving-side rotating body A is called an advance angle operation, and this advance angle operation increases the intake compression ratio. Furthermore, the operation of displacing the driven-side rotating body B in the opposite direction to the rotation of the driving-side rotating body A is called a retard angle operation, and this retard angle operation reduces the intake compression ratio.

[0030] [Valve timing control device]

[0031] The driving-side rotating body A comprises a cylindrical main body Aa centered on the rotation axis X, an Oldham coupling Cx that rotates synchronously with the main body Aa, and an input gear 30. The main body Aa is composed of a housing 11, with a drive sprocket 11S formed on its outer circumference, and a front plate 12, fastened together using multiple fastening bolts 13. The housing 11 is a bottomed cylindrical type with an opening at the bottom. The Oldham coupling Cx and the input gear 30, which constitute part of the driving-side rotating body A, also function as the phase adjustment mechanism C, described later. The input gear 30 is connected to the main body Aa via the Oldham coupling Cx.

[0032] The interior space of the housing 11 houses an intermediate member 20 (an example of the driven-side rotating element B) and a phase adjustment mechanism C having a hypocycloid gear mechanism. Furthermore, the phase adjustment mechanism C includes an Oldham coupling Cx, which reflects phase changes on the driving-side rotating element A and the driven-side rotating element B. This Oldham coupling Cx is positioned between the intermediate member 20 and the front plate 12 in the direction of the rotation axis X. A lubrication recess 12a is formed on the surface of the front plate 12 that faces the Oldham coupling Cx, creating a small gap in the direction of the rotation axis X.

[0033] In the intermediate member 20 constituting the driven-side rotating body B, a support wall portion 21 connected to the intake camshaft 2 in a posture perpendicular to the rotation axis X and a cylindrical wall portion 22 having a cylindrical shape centered on the rotation axis X and protruding in a direction away from the intake camshaft 2 are integrally formed.

[0034] The intermediate member 20 is inserted so as to be relatively rotatable with the outer surface of its cylindrical wall portion 22 in contact with the inner surface of the housing 11. It is secured to the end of the intake camshaft 2 by a fastening bolt 23 extending through a central through-hole in the support wall portion 21. An opening 21a is formed in a portion of the surface of the support wall portion 21 of the intermediate member 20 that contacts the intake camshaft 2. This opening guides oil into the interior of the eccentric member 26.

[0035] The phase-controlled motor M is supported on the engine E via a support frame 7, with the axis of its output shaft Ma (an example of a rotating shaft) aligned with the axis of rotation X. A pair of engaging pins 8 are formed on the output shaft Ma of the phase-controlled motor M, oriented orthogonally to the axis of rotation X. The phase-controlled motor M in this embodiment is comprised of a three-phase motor comprising a rotor (not shown) with the output shaft Ma fixed to its inner periphery and permanent magnets embedded in its outer periphery, and a stator (not shown) that generates magnetic flux for imparting rotational force to the rotor. The stator comprises three stator coils (not shown) for U, V, and W phases. The inverter 10b of the control unit 10, described later, converts a DC voltage into an AC voltage, which is then applied to each stator coil. The stator coils are electrically connected via a Δ connection or a Y connection. Furthermore, the phase-controlled motor M is provided with a rotation angle sensor S3. Multiple rotation angle sensors S3 are provided in the rotational direction of the output shaft Ma, and detect the rotational phase and rotational speed of the output shaft Ma.

[0036] The phase adjustment mechanism C is composed of multiple components and is used to change the relative rotational phase between the driving-side rotating body A and the driven-side rotating body B by phase-controlling the driving force of the electric motor M. The phase adjustment mechanism C includes an intermediate member 20, an output gear 25 (an example of a gear mechanism) formed on the inner circumferential surface of the cylindrical wall portion 22 of the intermediate member 20, an eccentric member 26, a leaf spring 27, a first bearing 28, a second bearing 29, a fixing ring 31, an Oldham coupling Cx, and an input gear 30 (an example of a gear mechanism).

[0037] In the inner periphery of the cylindrical wall portion 22 of the intermediate component 20, a support surface 22S centered on the rotation axis X is formed on the inner side along the direction of the rotation axis X (adjacent to the support wall portion 21), and an output gear 25 centered on the rotation axis X is integrally formed on the outer side of the support surface 22S along the direction of the rotation axis X (on the side away from the intake camshaft 2).

[0038] The eccentric member 26 is cylindrical and includes a first portion 26A and a second portion 26B. The first portion 26A supports the radially inner side of the driven-side rotor B (intermediate member 20) on the inner side (closer to the intake camshaft 2) along the rotation axis X, while the second portion 26B supports the radially inner side of the driving-side rotor A (input gear 30) on the outer side (farther from the intake camshaft 2) along the rotation axis X. An eccentric support surface 26E is formed on the second portion 26B. This eccentric support surface 26E is an outer circumferential surface parallel to the rotation axis X and centered at an eccentric axis Y offset from the rotation axis X by a predetermined eccentricity Dy. A leaf spring 27 is fitted into a recess 26F formed on the outer circumference of the eccentric support surface 26E. Furthermore, a protrusion 26S is formed on the first portion 26A, protruding radially outward from the radial outer surface of the leaf spring 27. A circumferential support surface 26Sa centered on the rotation axis X is formed on the outer peripheral surface of the protruding portion 26S.

[0039] A pair of engagement grooves 26T are formed on the inner circumference of the eccentric member 26, parallel to the rotation axis X, and capable of engaging with the pair of engagement pins 8 of the phase control motor M. Furthermore, an annular protrusion 26a is formed on the inner end (on the support wall 21 side) of the eccentric member 26 in the direction of the rotation axis X, projecting radially outward. This protrusion 26a is sandwiched between the support wall 21 of the driven-side rotating body B and the first bearing 28 in the direction of the rotation axis X, and functions to prevent the eccentric member 26 from falling out.

[0040] In this phase adjustment mechanism C, the number of teeth on the external teeth portion 30A of the input gear 30 is set to be only one less than the number of teeth on the internal teeth portion 25A of the output gear 25. Furthermore, a portion of the external teeth portion 30A of the input gear 30 meshes with a portion of the internal teeth portion 25A of the output gear 25, thereby forming a gear mechanism. A leaf spring 27 biases the input gear 30, causing a portion of the external teeth portion 30A of the input gear 30 to mesh with a portion of the internal teeth portion 25A of the output gear 25. This biasing force of the leaf spring 27 eliminates backlash in the meshing portion between the input gear 30 and the output gear 25.

[0041] The fixing ring 31 is a C-shaped annular member fixed in a fitted state to the eccentric member 26 on the outer side of the eccentric support surface 26E in the rotation axis X direction (the side away from the intake camshaft 2), thereby preventing the second bearing 29 from falling off.

[0042] The Oldham coupling Cx is composed of a plate-shaped coupling member, which has a pair of external engagement arms (not shown) engaged with the housing 11 and a pair of internal engagement arms (not shown) engaged with the input gear 30. The Oldham coupling Cx is displaceable relative to the housing 11 in a first direction (a direction perpendicular to the rotation axis X) in which the external engagement arms project, while the input gear 30 is freely displaceable relative to the Oldham coupling Cx in a second direction (a direction perpendicular to the rotation axis X and the first direction) along the direction in which the internal engagement arms are formed.

[0043] Lubricating oil supplied from the oil pump P is supplied from the lubricating oil passage 15 of the intake camshaft 2 through the opening 21a of the support wall 21 of the intermediate member 20 into the interior of the eccentric member 26. Centrifugal force causes the supplied lubricating oil to flow through the gap between the protrusion 26a of the eccentric member 26 and the support wall 21 of the driven-side rotor B, supplying it to the first bearing 28, thereby ensuring smooth operation of the first bearing 28. Simultaneously, centrifugal force also flows the lubricating oil within the eccentric member 26 into the Oldham coupling Cx, the second bearing 29, and the space between the internal teeth 25A of the output gear 25 and the external teeth 30A of the input gear 30. The lubricating oil supplied to the Oldham coupling Cx is then discharged to the exterior through the gap between the Oldham coupling Cx and the housing 11.

[0044] According to the above structure, the support wall portion 21 of the intermediate member 20 is connected to the end of the intake camshaft 2 by a connecting bolt 23, allowing the intake camshaft 2 and the intermediate member 20 to rotate integrally. The eccentric member 26 is supported by the first bearing 28 so as to be rotatable relative to the intermediate member 20 about the rotation axis X. The input gear 30 is supported by the second bearing 29 relative to the eccentric support surface 26E of the eccentric member 26. Due to the biasing force of the leaf spring 27, a portion of the external teeth 30A of the input gear 30 meshes with a portion of the internal teeth 25A of the output gear 25. Furthermore, since the front plate 12 is disposed outside the Oldham coupling Cx, the Oldham coupling Cx can move in a direction perpendicular to the rotation axis X while in contact with the inner surface of the front plate 12. Furthermore, a pair of engaging pins 8 formed on the output shaft Ma of the phase control motor M engage with the engaging grooves 26T of the eccentric member 26.

[0045] The phase control motor M is controlled by a control unit 10. The engine E is equipped with a crankshaft sensor S1 and a camshaft sensor S2 capable of detecting the rotational speed (revolutions per unit time) and respective rotational phases of the crankshaft 1 and intake camshaft 2. Detection signals from these sensors are input to the host ECU 50. Upon receiving a phase command from the host ECU 50 to maintain the relative rotational phase, the control unit 10 drives the phase control motor M at a speed equal to the rotational speed of the intake camshaft 2 during engine E operation, thereby maintaining the relative rotational phase. Conversely, upon receiving a phase command from the host ECU 50 to shift the relative rotational phase, the control unit 10 reduces the rotational speed of the phase control motor M below that of the intake camshaft 2 to advance the angle, and increases the rotational speed to retard the angle.

[0046] When the phase control motor M rotates at a speed equal to that of the housing 11 (the speed equal to that of the intake camshaft 2), the relative rotational phase of the driven side rotating body B relative to the driving side rotating body A can be maintained because the meshing position of the external tooth portion 30A of the input gear 30 relative to the internal tooth portion 25A of the output gear 25 does not change.

[0047] In contrast, by rotating the output shaft Ma of the phase control motor M at a speed higher or lower than the speed of the housing 11 in proportion to the gear mechanism's reduction ratio, the eccentric axis Y in the phase adjustment mechanism C orbits about the rotation axis X. This orbital movement causes the meshing position of the external teeth 30A of the input gear 30 with the internal teeth 25A of the output gear 25 to shift along the inner circumference of the output gear 25, and a rotational force acts between the input gear 30 and the output gear 25. Specifically, a rotational force centered on the rotation axis X acts on the output gear 25, while a rotational force tending to cause the input gear 30 to rotate about the eccentric axis Y acts on the input gear 30.

[0048] As described above, because the input gear 30 is engaged with the internal engagement arms of the Oldham coupling Cx, it does not rotate relative to the housing 11. The rotational force of the main body Aa of the driving-side rotor A acts on the output gear 25. This rotational force causes the intermediate member 20 and the output gear 25 to rotate relative to the housing 11 about the rotation axis X. As a result, the relative rotational phase between the driving-side rotor A and the driven-side rotor B is set, enabling the intake camshaft 2 to be set in its opening and closing timing.

[0049] In addition, when the eccentric axis Y of the input gear 30 revolves around the rotation axis X, as the input gear 30 is displaced, the cross slider coupling Cx is displaced relative to the housing 11 in the direction in which the external engaging arm protrudes (the first direction), and the input gear 30 is displaced in the direction in which the internal engaging arm protrudes (the second direction).

[0050] As described above, the number of teeth of the external tooth portion 30A of the input gear 30 is set to be only one tooth less than the number of teeth of the internal tooth portion 25A of the output gear 25. Therefore, by rotating the output shaft Ma of the phase-controlled motor M by the reduction ratio of the gear mechanism, when the eccentric axis Y of the input gear 30 revolves one circle around the rotation axis X, the output gear 25 only rotates by one tooth, thereby achieving a larger reduction in speed.

[0051] [Electric VVT control unit]

[0052] The control unit 10 includes a control unit 10a that controls the drive of the phase-controlled motor M and an inverter 10b that receives a phase instruction from the control unit 10a and applies an AC voltage to each phase of the phase-controlled motor M. The control unit 10 is electrically connected to the upper ECU 50 that controls the drive of the engine E via a wired connection such as a cable. Therefore, the control unit 10 and the upper ECU 50 are configured to be able to send and receive various types of information to each other. It should be noted that the control unit 10 and the upper ECU 50 can also be configured to be able to communicate wirelessly. The various functional units of the control unit 10 are composed of software centered around a CPU and a memory that perform various processes, or a collaboration of hardware and software.

[0053] In the host ECU 50, the current relative rotational phase (actual phase) obtained from the crankshaft sensor S1 that detects the rotational position of the crankshaft 1 and the cam sensor S2 that detects the rotational phase of the intake camshaft 2, as well as the target phase, which is the optimal relative rotational phase set according to the operating state of the engine E, are transmitted to the control unit 10. The control unit 10a receives the phase command from the host ECU 50 that controls the drive of the engine E and controls the drive of the phase control motor M (the rotational speed of the output shaft Ma) so that the current relative rotational phase is at the target phase, thereby setting the relative rotational phase of the driven-side rotating body B with respect to the driving-side rotating body A.

[0054] The control unit 10a sends a drive signal to each switching element (not shown) of the inverter 10b to control the amount of current flowing to the stator coils of the three phases, namely the U phase, V phase and W phase, of the phase control motor M. When controlling the amount of current flowing, it is executed based on the actual phase and target phase received from the upper ECU 50 during the driving of the engine E. On the other hand, when the engine E stops, the control unit 10a controls the amount of current flowing to the inverter 10b to become the optimal target phase (for example, the maximum lag angle phase) at the next start, and stops energizing the phase control motor M at the moment of becoming the target phase. At this time, the inertia force of the intake camshaft 2 that wants to continue rotating and the inertia force of the phase control motor M that wants to continue rotating exceed the cogging torque, the intake camshaft 2 does not stop, and the relative rotation phase is displaced due to the cam torque (refer to Figure 2As a result, when the engine E is started next time, it takes a certain amount of time to set to the optimal target phase.

[0055] Therefore, after the engine E stops, the control unit 10a in this embodiment intermittently performs control to energize one phase of the phase-controlled electric motor M for a predetermined time (eg, 50 ms). Figure 2 An example of energization control of the phase-controlled motor M by the control unit 10a is shown. As shown in the figure, after the engine E stops, the control unit 10a controls the amount of power supplied to the inverter 10b so as to achieve the optimal target phase (for example, the maximum lag angle phase) at the next start-up, and stops energizing the phase-controlled motor M at the moment of reaching the target phase. The control unit 10a then sends a drive signal to each switching element of the inverter 10b to energize one of the three phases of the phase-controlled motor M: the U phase, the V phase, and the W phase. When this single phase is energized, the output shaft Ma of the phase-controlled motor M stops at the position of the energized phase, counteracting the cam torque and fixing the meshing position of the gear mechanism (the input gear 30 and the output gear 25), thereby stopping the displacement of the relative rotational phase.

[0056] Next, the control unit 10a stops energizing the phase-controlled motor M. As a result, the output shaft Ma of the phase-controlled motor M and the intake camshaft 2 resume rotation due to inertia. The cam torque applied to the motor causes the meshing position of the gear mechanism (input gear 30 and output gear 25) to change, shifting the relative rotational phase (e.g., toward the advanced angle). Next, the control unit 10a again sends a drive signal to each switching element of the inverter 10b to energize one of the three phases: U, V, and W. The control unit 10a repeats this cycle of energizing and de-energizing one phase of the phase-controlled motor M multiple times (six times in this embodiment) before completely stopping energizing the phase-controlled motor M. In this embodiment, the control unit 10a controls the interval between energizing one phase and the next energizing of the same phase based on time (e.g., 60 ms).

[0057] When the power supply to the phase-controlled motor M is stopped and the output shaft Ma of the phase-controlled motor M is rotating, dynamic friction dominates and the relative rotation phase shifts. However, when the tooth torque of the phase-controlled motor M exceeds the torque generated by the cam torque, etc., it will become a static friction state and the shift of the relative rotation phase will stop.

[0058] That is, in this embodiment, if Figure 2 As shown by the solid line of the "relative rotation phase", the relative rotation phase is stopped by energizing one phase of the phase control motor M. By intermittently energizing the one phase, the relative rotation phase is stopped compared to not energizing the one phase. Figure 2 Compared to the conventional example shown by the dashed line of the "relative rotational phase" of FIG, the displacement of the relative rotational phase during the period from the dynamic friction state to the static friction state can be suppressed. As a result, the relative rotational phase can be quickly shifted to the target phase when the engine E is next started. Therefore, the relative rotational phase can be reliably shifted to the target phase suitable for cranking before the ignition switch is turned on and the engine E starts cranking.

[0059] Figure 3 The control flow of the valve timing control device 100 according to this embodiment is shown. When the engine E is driven, the control unit 10a of the valve timing control device 100 controls the relative rotational phase based on a phase command from the host ECU 50 (#31). Then, when the ignition switch is turned off and the engine E is stopped (#32), the control unit 10a controls the amount of power supplied to the inverter 10b based on the phase command from the host ECU 50 to achieve the optimal target phase (e.g., the most retarded phase) for the next start-up. At the time the target phase is reached, power to the phase control motor M is stopped (#33).

[0060] Next, after the engine E stops, the control unit 10a performs a braking action (#34), which is to intermittently perform control of one phase of the phase-controlled motor M for a specified time (for example, 50 ms). The interval between the one-phase energization and the next one-phase energization is controlled based on time (for example, 60 ms, etc.). Then, when a specified time (for example, 600 ms) has passed since the control unit 10a started the intermittent control of the one-phase energization (#35 is), the power supply to the phase-controlled motor M is completely stopped (#36). Then, when the ignition switch is turned on and the engine E is started (#37), the control unit 10a controls the phase-controlled motor M based on the phase command from the host ECU 50, performs a relative rotational phase shift to become the target phase suitable for cranking (for example, the maximum lag angle phase), and starts cranking (#38, #39). As described above, since the control unit 10a can suppress the displacement of the relative rotational phase from the dynamic friction state to the static friction state, the relative rotational phase can be reliably displaced to the target phase suitable for cranking when the engine E is started next time.

[0061] [Other embodiments]

[0062] (1) The control unit 10a may also control the interval between the energization of one phase of the phase-controlled motor M and the next energization of one phase based on the rotation angle of the phase-controlled motor M detected by the rotation angle sensor S3. If the interval between energization of one phase is controlled based on the rotation angle of the phase-controlled motor M in this way, the output shaft Ma of the phase-controlled motor M can be stopped at the moment of energization of one phase, thereby reliably stopping the displacement of the relative rotation phase. In addition, if Figure 4 In the static friction state shown, stopping the rotation of the output shaft Ma at the moment when the cogging torque intersects the cam torque (the moment when the cam torque and cogging torque are balanced) effectively eliminates the cam torque and shortens the time it takes to transition from the dynamic friction state to the static friction state. As a result, the displacement of the relative rotational phase caused by the cam torque can be effectively suppressed.

[0063] (2) The control unit 10a may determine the phase of the phase-controlled motor M to be energized as one phase based on the rotation angle of the phase-controlled motor M detected by the rotation angle sensor S3. By determining the phase of the phase-controlled motor M to be energized as one phase based on the rotation angle of the phase-controlled motor M in this manner, the time required for the output shaft Ma of the phase-controlled motor M to stop can be shortened, and the displacement of the relative rotational phase can be further suppressed.

[0064] (3) The control unit 10a may sequentially energize each phase of the phase-controlled motor M. If the phases are sequentially energized in this manner, the output shaft Ma of the phase-controlled motor M can be effectively stopped even without detecting the rotation angle of the output shaft Ma.

[0065] (4) Phase Control The rotation angle of the electric motor M can be estimated based on the detection values ​​of the crank sensor S1 and the cam sensor S2.

[0066] (5) The valve timing control device 100 as an electric VVT is not limited to the above-described embodiment, and may have any configuration as long as it is a device that displaces the relative rotational phase using an electric actuator.

[0067] (6) The phase-controlled electric motor M is not particularly limited as long as it is a motor composed of multiple phases, such as a brushless DC motor, an AC asynchronous motor, or an AC synchronous motor.

[0068] [Industrial Applicability]

[0069] The present invention can be used in a valve timing control device that sets the relative rotational phase between a driving-side rotating body and a driven-side rotating body using the driving force of an electric motor.

[0070] Explanation of symbols

[0071] 1: Crankshaft

[0072] 2: Intake camshaft (camshaft)

[0073] 10: Control unit

[0074] 10a: Control Unit

[0075] 100: Valve timing control device

[0076] 25: Output gear (gear mechanism)

[0077] 30: Input gear (gear mechanism)

[0078] A: Driving side rotating body

[0079] B: Driven side rotating body

[0080] E: Engine (internal combustion engine)

[0081] M: Phase control motor (motor)

[0082] Ma: Output shaft (rotational axis)

[0083] X: Rotation axis

Claims

1. A valve timing control device comprising: a driving-side rotating body that rotates about a rotation axis in synchronization with a crankshaft of the internal combustion engine; a driven-side rotating body that rotates integrally with a camshaft for opening and closing valves of the internal combustion engine on the same axis as the rotation axis; a gear mechanism that sets a relative rotational phase between the driving-side rotating body and the driven-side rotating body by shifting a meshing position; an electric motor capable of displacing the meshing position of the gear mechanism by rotating a rotating shaft; and a control unit that controls driving of the electric motor, After the internal combustion engine stops, the control unit intermittently performs control to energize one phase of the electric motor for a specified time, and stops energizing the electric motor in an interval between the one-phase energization and the next one-phase energization.

2. The valve timing control device according to claim 1, wherein: The control unit controls an interval between the one-phase energization and the next one-phase energization based on time.

3. The valve timing control device according to claim 1, wherein: The control unit controls an interval between the one-phase energization and the next one-phase energization based on a rotation angle of the motor.

4. The valve timing control device according to claim 3, wherein: The control unit determines a phase of the electric motor to which the one phase is energized based on the rotation angle.

5. The valve timing control device according to claim 1 or 2, wherein: The control unit sequentially performs the one-phase energization on each phase of the electric motor.

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