JP7723751B2 - Motor control device and motor control method - Google Patents

Description

The present invention relates to a motor control device and control method that rotates a rotating body equipped with a stopper that regulates the rotation angle using speed feedback control.

One example of a controlled device equipped with a mechanical stopper that limits the rotation angle of a rotor driven by a motor is the variable valve timing (VVT) mechanism described in JP 2018-123716 A (Patent Document 1). In a VVT mechanism, the valve timing of at least one of the intake valves and exhaust valves is changed by using a motor to change the relative rotation angle of the camshaft with respect to the crankshaft.

Japanese Patent Application Laid-Open No. 2018-123716

When controlling a VVT mechanism equipped with a stopper, a process is performed in which a rotating body driven by a motor is pressed against a mechanical stopper, for example, in order to learn the reference angle for valve timing. When this learning process is performed, if the learning accuracy of the reference angle is insufficient, it will not be possible to determine that the rotating body is pressed against the stopper, and excessive current will be supplied to the electric motor in an attempt to rotate the rotating body to the target angle.

Therefore, the present invention aims to provide a motor control device and a motor control method that prevent excessive current from being supplied to a motor that rotates a rotating body using speed feedback control when the rotation angle of the rotating body is restricted by a mechanical stopper.

A motor control device rotates a rotor equipped with a stopper that restricts the rotation angle by speed feedback control. When the absolute value of the deviation between the target rotation speed of the motor and its actual rotation speed remains above a predetermined lower limit and below a predetermined upper limit for a predetermined period of time, the motor control device determines that the rotation angle of the rotor is restricted by the stopper and restricts the current supplied to the motor.

According to the present invention, when the rotation angle of a rotating body is restricted by a mechanical stopper, excessive current can be prevented from being supplied to a motor that rotates the rotating body using speed feedback control.

1 is a schematic diagram illustrating an example of an engine system mounted on a vehicle. FIG. 2 is a vertical cross-sectional view showing an example of a VVT mechanism. 3 is a cross-sectional view taken along line AA in FIG. 2. 3 is a cross-sectional view taken along the line BB in FIG. 2. FIG. 1 is a diagram for explaining a defect in the prior art. 4 is a flowchart illustrating an example of a VVT control process. 4 is a flowchart illustrating an example of a VVT control process. 4 is a flowchart illustrating an example of a VVT control process. 4 is a flowchart illustrating an example of a VVT control process. 10A and 10B are explanatory diagrams showing a problem that occurs when a current limit value is inappropriate. 10A and 10B are diagrams illustrating a method for optimizing a current limit value and the effects thereof. 10A and 10B are diagrams illustrating the effect of limiting the current to the electric motor.

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 shows an example of an engine system mounted on a vehicle to which a motor control device according to this embodiment can be applied.

The engine 10 mounted on a vehicle such as an automobile is, for example, an in-line four-cylinder gasoline engine. An intake air flow sensor 14 is attached to a predetermined location in the intake pipe 12, which introduces intake air (intake air) into each cylinder. The intake air flow sensor 14 detects the intake air flow rate Q, which is one example of the load on the engine 10. For example, a hot-wire flow meter such as an air flow meter can be used as the intake air flow rate sensor 14. Note that the load on the engine 10 is not limited to the intake air flow rate Q; other state quantities closely related to torque, such as intake negative pressure, boost pressure, throttle opening, and accelerator opening, can also be used.

Each intake port 18, which introduces intake air into the combustion chamber 16 of each cylinder, is equipped with an intake valve 20 that opens and closes the end opening facing the combustion chamber 16. A fuel injection valve 22 is attached to a predetermined location on the intake port 18, located upstream of the intake valve 20. The fuel injection valve 22 injects fuel toward the back surface of the intake valve head. When magnetic attraction is generated by energizing the electromagnetic coil, the valve element of the fuel injection valve 22, which is biased by a spring in the valve closing direction, lifts, opening the nozzle hole at the tip and injecting fuel. The fuel injection valve 22 is supplied with fuel adjusted to a predetermined pressure so that the amount of fuel injected is approximately proportional to the duration the nozzle hole is open. The fuel injection valve 22 is not limited to a configuration that injects fuel toward the back surface of the intake valve head, but may also be a configuration that injects fuel directly into the combustion chamber 16, or a configuration that combines both.

Fuel injected from the nozzle hole of the fuel injection valve 22 is introduced into the combustion chamber 16 along with the intake air through the gap between the end opening of the intake port 18 and the intake valve 20, and is ignited and burned by spark ignition from the spark plug 24. As a result, the combustion pressure pushes the piston 26 toward the crankshaft (not shown), driving the crankshaft to rotate.

An exhaust port 28, which discharges exhaust gas from the combustion chamber 16, is equipped with an exhaust valve 30 that opens and closes the end opening facing the combustion chamber 16. When the exhaust valve 30 opens the end opening of the exhaust port 28, the exhaust gas passes through the gap between the end opening of the exhaust port 28 and the exhaust valve 30 and is discharged into an exhaust pipe 32. A catalytic converter 34 is attached to a predetermined location in the exhaust pipe 32. Harmful substances contained in the exhaust are purified into harmless components by the catalytic converter 34, and then released into the atmosphere from the end opening of the exhaust pipe 32. Here, the catalytic converter 34 can be, for example, a three-way catalyst that simultaneously purifies CO (carbon monoxide), HC (hydrocarbons), and NOx (nitrogen oxides) contained in the exhaust.

Attached to the end of the intake camshaft 36, which drives the intake valves 20 to open and close, is an electric VVT mechanism 100 that changes the valve timing of the intake valves 20 by changing the relative rotation angle of the intake camshaft 36 with respect to the crankshaft. The VVT mechanism 100 is not limited to being attached to the intake valve 20, but may be attached to at least one of the intake valves 20 and exhaust valves 30. Details of the VVT mechanism 100 will be described later.

In addition to the intake air flow rate sensor 14, a water temperature sensor 38, an engine speed sensor 40, a crank angle sensor 42, a cam angle sensor 44, and a motor speed sensor 46 are installed at predetermined locations in the engine system. The water temperature sensor 38 detects the coolant temperature (water temperature) Tw of the engine 10. The engine speed sensor 40 detects the rotational speed Ne of the engine 10. The crank angle sensor 42 detects the rotational angle θ _CRK of the crankshaft from a reference position. The cam angle sensor 44 detects the rotational angle θ _CAM of the intake camshaft 36 from a reference position. The motor speed sensor 46 detects the rotational speed Nm of the output shaft of the electric motor (details of which will be described later) of the VVT mechanism 100. In the following description, the rotational speed of the output shaft of the electric motor will be abbreviated as the rotational speed of the electric motor.

The output signals of the intake air flow sensor 14, water temperature sensor 38, engine speed sensor 40, crank angle sensor 42, cam angle sensor 44, and motor speed sensor 46 are input to an engine control module (ECM) 200, which incorporates a microcomputer (not shown). The engine control module 200 reads the intake air flow rate Q and engine speed Ne from the intake air flow rate sensor 14 and engine speed sensor 40, respectively, and calculates a basic fuel injection amount corresponding to the engine operating conditions based on these values. The engine control module 200 also reads the water temperature Tw from the water temperature sensor 38 and calculates a fuel injection amount obtained by correcting the basic fuel injection amount based on the water temperature Tw, etc. The engine control module 200 then outputs activation signals to the fuel injection valve 22 and spark plug 24 at timing corresponding to the engine operating conditions, causing the fuel injection valve 22 to inject fuel corresponding to the fuel injection amount and the spark plug 24 to ignite and burn the fuel-air mixture. At this time, the engine control module 200 reads the air-fuel ratio from an air-fuel ratio sensor (not shown) and feedback controls the fuel injection valve 22 so that the air-fuel ratio in the exhaust gas approaches the target air-fuel ratio.

In addition to controlling the fuel injectors 22 and spark plugs 24, the engine control module 200 reads the intake air flow rate Q and rotational speed Ne from the intake air flow rate sensor 14 and engine rotational speed sensor 40, respectively, and calculates the target angle of the VVT mechanism 100 according to the engine operating state. The engine control module 200 also multiplies the rotational speed Ne by 1/2 to calculate the rotational speed Nc of the intake camshaft 36 (Nc = Ne x 1/2), and reads the rotational speed Nm from the motor rotational speed sensor 46. Furthermore, the engine control module 200 calculates the rotational speed Nc of the intake camshaft 36, the rotational speed Nm of the electric motor, and the target rotational speed Nt of the electric motor according to the reduction ratio of the VVT mechanism 100, so that the VVT mechanism 100 approaches the target angle. Then, engine control module 200 transmits the target rotation speed Nt of the electric motor to a VVT controller 250, which has a built-in microcomputer (not shown), via a well-known in-vehicle network such as a Controller Area Network (CAN). Here, like engine control module 200, an output signal of a motor rotation speed sensor 46, which detects the rotation speed Nm of the electric motor, is input to VVT controller 250. Note that VVT controller 250 is an example of a motor control device.

The VVT controller 250 receives the target rotation speed Nt of the electric motor, reads the actual rotation speed (actual rotation speed) Nm of the electric motor from the motor rotation speed sensor 46, and feedback controls the current supplied to the electric motor so that the actual rotation speed Nm approaches the target rotation speed Nt. In other words, the VVT controller 250 controls the current supplied to the electric motor of the VVT mechanism 100 through speed feedback control.

Figures 2 to 4 show an example of a VVT mechanism 100. Note that the VVT mechanism 100 shown in Figures 2 to 4 is merely an example, and any VVT mechanism known to those skilled in the art may be used as long as it is equipped with a mechanical stopper that limits the rotation angle of a rotating body driven by an electric motor.

As shown in FIG. 2, the VVT mechanism 100 includes a timing sprocket (cam sprocket) 102, a cover member 104, and a phase change mechanism 106. The timing sprocket 102 is rotated by the crankshaft of the engine 10 via a timing chain 108. The timing sprocket 102 then rotates the intake camshaft 36, which is integrated with the timing sprocket 102. The cover member 104 is fastened with bolts 112 to a chain cover 110, which is a fixed structure of the engine 10, on the distal side of the timing sprocket 102 relative to the intake camshaft 36. The phase change mechanism 106 is disposed between the timing sprocket 102 and the intake camshaft 36 and changes the relative rotation angle of the timing sprocket 102 with respect to the intake camshaft 36. Here, the timing sprocket 102 is an example of a rotating body.

The timing sprocket 102 is rotatably mounted relative to the outer peripheral surface of the end of the intake camshaft 36 via a ball bearing 114. An annular member 116, with wavy internal teeth 116A (see Figure 3) formed on its inner circumference, and an annular plate 118 are fastened by bolts 120 to the side of the outer periphery of the timing sprocket 102, which is located distal to the intake camshaft 36. Furthermore, as shown in Figure 4, an arc-shaped stopper protrusion 102A is formed on part of the inner peripheral surface of the timing sprocket 102 over a predetermined length in the circumferential direction.

A cylindrical housing 126 extending distally from the intake camshaft 36 is fastened to the distal outer periphery of the plate 118 with bolts 128, covering the components of the reducer 122 of the phase change mechanism 106 and the electric motor 124. The housing 126 is made of a non-ferrous metal and functions as a yoke. An annular plate-shaped retaining portion 126A is integrally connected to the distal tip surface of the housing 126. The housing 126 is covered by the cover member 104, which is positioned further distally, with at least a predetermined distance between the housing 126 and the cover member 104.

A driven member 130, which is a driven rotor, is fastened to the end of the intake camshaft 36 by a cam bolt 132. Furthermore, as shown in Figure 4, a circular-arc-shaped stopper groove 36A is formed over a predetermined length along the circumferential direction on part of the outer peripheral surface of the tip of the intake camshaft 36. The stopper protrusion 102A of the timing sprocket 102 fits into the stopper groove 36A for relative rotation. The stopper protrusion 102A of the timing sprocket 102 and the stopper groove 36A of the intake camshaft 36 form a stopper.

When the timing sprocket 102 rotates relative to the intake camshaft 36 and the stopper protrusion 102A abuts against the inner surface of the stopper groove 36A, the timing sprocket 102 is prevented from rotating relative to the intake camshaft 36. This defines the maximum advance and maximum retard positions of the timing sprocket 102 relative to the intake camshaft 36, thereby limiting the variable range of valve timing for the intake valve 20.

The driven member 130 is made of an iron-based metal and, as shown in Figures 2 and 3, includes a disk portion 130A located proximal to the intake camshaft 36 and a cylindrical portion 130B located distal to the intake camshaft 36. A ring-shaped protrusion 130C having approximately the same diameter as the intake camshaft 36 is integrally formed on the disk portion 130A, into which a portion of the inner ring of the ball bearing 114 is fitted. Furthermore, a retainer 136 that holds multiple rollers 134 is integrally formed on the outer periphery of the disk portion 130A.

The phase change mechanism 106 is composed of an electric motor 124 arranged concentrically with the intake camshaft 36 and a reducer 122 that transmits the rotational speed of the electric motor 124 to the intake camshaft 36 while reducing the rotational speed.

The electric motor 124 includes a housing 126 that rotates integrally with the timing sprocket 102, a motor shaft 138 that is rotatably disposed within the housing 126, a pair of permanent magnets 140, 142 fixed to the inner surface of the housing 126, and a stator 144 fixed to the retaining portion 126A of the housing 126. The motor shaft 138 is cylindrical and functions as an armature. An iron core rotor 146 with multiple poles is fixed to the outer periphery of the motor shaft 138 approximately at the center. An electromagnetic coil 148 is wound around the iron core rotor 146.

The motor shaft 138 is arranged to be rotatable relative to the outer periphery of the cam bolt 132 and the outer periphery of the cylindrical portion 130B of the driven member 130 via a ball bearing 150 and a needle bearing 152. Furthermore, a cylindrical eccentric shaft portion 154, which constitutes part of the reducer 122, is integrally formed at the proximal end of the motor shaft 138.

The reducer 122 is composed of an eccentric shaft portion 154 that rotates eccentrically, a ball bearing 156 arranged on the outer periphery of the eccentric shaft portion 154, a roller 134 arranged on the outer periphery of the ball bearing 156, a retainer 136 that holds the roller 134 in the rolling direction while allowing it to move in the radial direction, and a driven member 130 that is integrated with the retainer 136. The axis of the cam surface formed on the outer periphery of the eccentric shaft portion 154 is slightly eccentric in the radial direction from the axis X of the motor shaft 138. Here, the ball bearing 156, roller 134, etc. function as a planetary meshing portion.

In addition, rollers 134 are constantly in contact with the outer peripheral surface of the outer ring of ball bearing 156. Furthermore, an annular gap 158 is formed on the outer periphery of ball bearing 156, and this gap 158 allows the entire ball bearing 156 to move radially in conjunction with the eccentric rotation of eccentric shaft portion 154, in other words, to be eccentric. Each roller 134 moves radially in conjunction with the eccentric movement of ball bearing 156, fitting into internal teeth 116A of annular member 116, and is configured to oscillate radially while being guided circumferentially by cage 136.

Next, the operation of the VVT mechanism 100 will be described.
When the crankshaft of the engine 10 rotates, the timing sprocket 102 is rotated via the timing chain 108, and the resulting rotational force synchronously rotates the electric motor 124 via the annular member 116, plate 118, and housing 126. Meanwhile, the rotational force of the annular member 116 is transmitted to the intake camshaft 36 via the roller 134, cage 136, and driven member 130. This rotates the intake camshaft 36, and the cam formed thereon opens and closes the intake valve 20.

To change the relative rotation angle of the intake camshaft 36 with respect to the crankshaft, i.e., the valve timing of the intake valve 20, the electromagnetic coil 148 is energized to operate the electric motor 124. When the electric motor 124 is operating, its rotational force is transmitted to the intake camshaft 36 via the reducer 122. Specifically, as the eccentric shaft portion 154 rotates eccentrically in conjunction with the rotation of the motor shaft 138, each roller 134 is guided radially by the retainer 136 and moves over one internal tooth 116A of the annular member 116, rolling onto the adjacent internal tooth 116A. Each roller 134 then rotates in the circumferential direction, repeatedly repeating this process. The rotation of the motor shaft 138 is then transmitted to the driven member 130 at a reduced speed as each roller 134 rotates. The reduction ratio when the rotation of the motor shaft 138 is transmitted to the driven member 130 can be set arbitrarily depending on the number of rollers 134, etc.

As a result, the intake camshaft 36 rotates forward and backward relative to the timing sprocket 102, changing the relative rotation angle. This changes the opening and closing timing of the intake valve 20 to the advance or retard side.

At this time, the forward and reverse relative rotation of the intake camshaft 36 with respect to the timing sprocket 102 is restricted by the stopper protrusion 102A abutting against the inner surface of the stopper groove 36A. That is, the driven member 130 rotates relative to the timing sprocket 102 in the same direction as the rotation of the timing sprocket 102 in conjunction with the eccentric rotation of the eccentric shaft portion 154, causing the stopper protrusion 102A to abut against one side of the stopper groove 36A, restricting further rotation. This changes the relative rotation angle of the intake camshaft 36 with respect to the timing sprocket 102 to maximum advance. Meanwhile, the driven member 130 rotates relative to the timing sprocket 102 in the opposite direction to the rotation of the timing sprocket 102, causing the stopper protrusion 102A to abut against the other side of the stopper groove 36A, restricting further rotation. This changes the relative rotation angle of the intake camshaft 36 with respect to the timing sprocket 102 to maximum retard.

The mechanical stopper of the VVT mechanism 100 is used, for example, to learn the reference phase of the valve timing, to set the timing to the most retarded phase when the engine 10 is stopped in preparation for the next start, or to set the timing to the most advanced phase while the engine 10 is running. When the electric motor 124 of the VVT mechanism 100 is driven to rotate by speed feedback control, if the reference angle learning accuracy is insufficient, it may be impossible to determine whether the stopper is restricting the relative rotation of the timing sprocket 102 with respect to the intake camshaft 36. In this case, the VVT controller 250 attempts to rotate the timing sprocket 102 to the stopper activation position relative to the intake camshaft 36. Then, as shown in FIG. 5, the VVT controller 250 gradually increases the current supplied to the electric motor 124 to bring the actual rotational speed of the electric motor 124 closer to the target rotational speed. Ultimately, this results in an excessive current being supplied to the electric motor 124.

Therefore, when the absolute value of the deviation between the target rotational speed Nt of the electric motor 124 and its actual rotational speed Nm remains within a predetermined range for a predetermined period of time, the VVT controller 250 determines that the stopper protrusion 102A of the timing sprocket 102 is abutting against the inner surface of the stopper groove 36A of the intake camshaft 36. If the VVT controller 250 determines that the stopper protrusion 102A is abutting against the inner surface of the stopper groove 36A, it limits the current supplied to the electric motor 124 to prevent excessive current from being supplied to the electric motor 124. This process is described in detail below.

Figures 6 to 9 show an example of VVT control processing that is repeatedly executed at predetermined time intervals by the microcomputer of the VVT controller 250 when the VVT controller 250 is started. The microcomputer of the VVT controller 250 executes the VVT control processing in accordance with an application program stored in a non-volatile memory, such as flash ROM (Read Only Memory). A variable area reserved in advance in volatile memory, such as RAM (Random Access Memory) of the microcomputer, holds a determination flag that holds the result of determining whether the stopper is being pressed. The determination flag is selectively set to either "TRUE (e.g., 1)," which indicates that the stopper is being pressed, or "FALSE (e.g., 0)," which indicates that the stopper is not being pressed, with its initial value being "FALSE."

In step 10 (abbreviated as "S10" in Figure 6, and the same applies below), the microcomputer of the VVT controller 250 calculates the speed deviation between the target rotational speed and the actual rotational speed of the electric motor 124. Specifically, the microcomputer of the VVT controller 250 reads the rotational speed Nm of the electric motor 124 from the motor rotational speed sensor 46 and calculates the speed deviation by subtracting the rotational speed Nm from the target rotational speed Nt received from the engine control module 200 (speed deviation = target rotational speed Nt - rotational speed Nm). Note that the rotational speed Nm detected by the motor rotational speed sensor 46 represents the actual rotational speed of the electric motor 124, and therefore will be referred to as the "actual rotational speed Nm" in the following description. Furthermore, since the rotational speed Ne of the engine 10 is closely related to the actual rotational speed Nm of the electric motor 124, the rotational speed Ne of the engine 10 may also be considered to be the actual rotational speed Nm of the electric motor 124.

In step 11, the microcomputer of the VVT controller 250 calculates the current command value to be supplied to the electric motor 124 based on the speed deviation calculated in step 10 and the current value (actual current value) of the current actually supplied to the electric motor 124.

In step 12, the microcomputer of the VVT controller 250 determines whether the determination flag is "FALSE," in other words, whether the stopper is being pressed. If the microcomputer of the VVT controller 250 determines that the determination flag is "FALSE," i.e., that the stopper is not being pressed (Yes), it proceeds to step 13. On the other hand, if the microcomputer of the VVT controller 250 determines that the determination flag is "TRUE," i.e., that the stopper is being pressed (No), it proceeds to step 17.

In step 13, the microcomputer of the VVT controller 250 determines whether the absolute value of the speed deviation is greater than or equal to a predetermined lower limit and less than or equal to a predetermined upper limit. Here, the predetermined lower limit and the predetermined upper limit are parameters for determining whether the stopper is being pressed, and can be determined appropriately taking into account, for example, the operating characteristics of the VVT mechanism 100. If the microcomputer of the VVT controller 250 determines that the absolute value of the speed deviation is greater than or equal to the predetermined lower limit and less than or equal to the predetermined upper limit (Yes), it proceeds to step 14. On the other hand, if the microcomputer of the VVT controller 250 determines that the absolute value of the speed deviation is not greater than or equal to the predetermined lower limit and less than or equal to the predetermined upper limit, in other words, if it determines that the absolute value of the speed deviation is less than the predetermined lower limit or greater than the predetermined upper limit (No), it proceeds to step 19.

In step 14, the microcomputer of the VVT controller 250, for example, uses a timer function to determine whether the absolute value of the speed deviation has remained above a predetermined lower limit and below a predetermined upper limit for a predetermined period of time. Here, the predetermined period of time is another parameter used to determine whether the stopper is being pressed, and can be determined appropriately, for example, taking into account the time it takes for the stopper to be pressed. If the microcomputer of the VVT controller 250 determines that the absolute value of the speed deviation has remained above a predetermined lower limit and below a predetermined upper limit for a predetermined period of time (Yes), it proceeds to step 15. On the other hand, if the microcomputer of the VVT controller 250 determines that the absolute value of the speed deviation has not remained above a predetermined lower limit and below a predetermined upper limit for a predetermined period of time (No), it proceeds to step 19.

In step 15, the microcomputer of the VVT controller 250 stores the actual current value of the current supplied to the electric motor 124 in a variable area previously allocated in volatile memory.

In step 16, the microcomputer of the VVT controller 250 sets the judgment flag to "TRUE", in other words, it determines that the stopper is being pressed.

In step 17, the microcomputer of the VVT controller 250 determines whether the sign of the speed deviation has reversed, specifically, whether the sign of the speed deviation in the previous control cycle is different from the sign of the speed deviation in the current control cycle. If the microcomputer of the VVT controller 250 determines that the sign of the speed deviation has reversed (Yes), it proceeds to step 18. On the other hand, if the microcomputer of the VVT controller 250 determines that the sign of the speed deviation has not reversed (No), it proceeds to step 19.

In step 18, the microcomputer of the VVT controller 250 sets the judgment flag to "FALSE," i.e., determines that the pressure on the stopper has been released. The microcomputer of the VVT controller 250 then proceeds to step 19.

In step 19, the microcomputer of the VVT controller 250 determines whether the determination flag is "TRUE," i.e., whether it has determined that the stopper is being pressed. If the microcomputer of the VVT controller 250 determines that the determination flag is "TRUE" (Yes), it proceeds to step 20. On the other hand, if the microcomputer of the VVT controller 250 determines that the determination flag is not "TRUE," i.e., that the stopper is not being pressed (No), it proceeds to step 45.

In step 20, the microcomputer of the VVT controller 250 determines whether the speed deviation calculated in step 10 is greater than or equal to 0, in other words, whether there is a push toward the advance angle side. If the microcomputer of the VVT controller 250 determines that the speed deviation is greater than or equal to 0 (Yes), it proceeds to step 21. On the other hand, if the microcomputer of the VVT controller 250 determines that the speed deviation is not greater than or equal to 0, in other words, there is a push toward the retard angle side (No), it proceeds to step 33.

In step 21, the microcomputer of the VVT controller 250 determines whether the determination flag was "FALSE" in the previous control cycle, in other words, whether the stopper was not pressed in the previous control cycle. If the microcomputer of the VVT controller 250 determines that the determination flag was "FALSE" in the previous control cycle (Yes), it proceeds to step 22. On the other hand, if the microcomputer of the VVT controller 250 determines that the determination flag was not "FALSE" in the previous control cycle, in other words, whether the stopper was pressed in the previous control cycle (No), it proceeds to step 27.

In step 22, the microcomputer of the VVT controller 250 determines whether the determination flag is "TRUE" in the current control cycle, in other words, whether the stopper is being pressed in the current control cycle. If the microcomputer of the VVT controller 250 determines that the determination flag is "TRUE" in the current control cycle (Yes), it proceeds to step 23. On the other hand, if the microcomputer of the VVT controller 250 determines that the determination flag is not "TRUE" in the current control cycle, in other words, that the stopper is not being pressed (No), it proceeds to step 27.

In step 23, the microcomputer of the VVT controller 250 determines whether the learned value on the advance side is equal to or less than the actual current value when the stopper is pressed against it. If the microcomputer of the VVT controller 250 determines that the learned value on the advance side is equal to or less than the actual current value (Yes), it proceeds to step 24. On the other hand, if the microcomputer of the VVT controller 250 determines that the learned value on the advance side is not equal to or less than the actual current, i.e., that the learned value on the advance side is greater than the actual current value (No), it proceeds to step 26.

In step 24, the microcomputer of the VVT controller 250 sets the current limit value, which is a parameter for limiting the current supplied to the electric motor 124, to the actual current value at the time of determining whether the stopper is being pressed against it.

In step 25, the microcomputer of the VVT controller 250 sets the advance side learning value to the actual current value when determining whether the stopper is being pressed. The microcomputer of the VVT controller 250 then proceeds to step 27.

In step 26, the microcomputer of the VVT controller 250 adopts the learned value on the advance side as the current limit value. The microcomputer of the VVT controller 250 then proceeds to step 27.

In step 27, the microcomputer of the VVT controller 250 reads the actual rotational speed Nm of the electric motor 124 from the motor rotational speed sensor 46 and determines whether this is 0, in other words, whether the engine 10 is being pressed against the stopper when stopped. If the microcomputer of the VVT controller 250 determines that the actual rotational speed Nm of the electric motor 124 is 0 (Yes), it proceeds to step 28. On the other hand, if the microcomputer of the VVT controller 250 determines that the actual rotational speed Nm of the electric motor 124 is not 0 (No), it proceeds to step 31.

In step 28, the microcomputer of the VVT controller 250 increases the current limit value by a predetermined value. That is, the microcomputer of the VVT controller 250 increases the current limit value by a predetermined value, taking into consideration that, for example, the cam torque of the intake camshaft 36 when the engine 10 is stopped may prevent the VVT mechanism 100 from operating at the current current limit value.

In step 29, the microcomputer of the VVT controller 250 determines whether the current limit value is equal to or greater than a predetermined current upper limit value, in other words, whether the intake camshaft 36 is being pressed against the stopper against the cam torque. If the microcomputer of the VVT controller 250 determines that the current limit value is equal to or greater than the current upper limit value (Yes), it proceeds to step 30. On the other hand, if the microcomputer of the VVT controller 250 determines that the current limit value is not equal to or greater than the current upper limit value, in other words, whether the intake camshaft 36 is not being pressed against the stopper against the cam torque (No), it proceeds to step 31.

In step 30, the microcomputer of the VVT controller 250 turns off the power supply to the electric motor 124. In short, the microcomputer of the VVT controller 250 determines that pressing against the stopper has been completed during the engine 10 stopping process, and stops the supply of current to the electric motor 124, for example, to reduce unnecessary power consumption.

In step 31, the microcomputer of the VVT controller 250 determines whether the stopper is still being pressed. Specifically, the microcomputer of the VVT controller 250 recalculates the current speed deviation and determines whether the absolute value of the value obtained by subtracting the current speed deviation from the speed deviation calculated in step 10 is equal to or less than a predetermined deviation; in other words, whether the stopper is still being pressed based on the two speed deviations. If the microcomputer of the VVT controller 250 determines that the stopper is still being pressed (Yes), it proceeds to step 45. On the other hand, if the microcomputer of the VVT controller 250 determines that the stopper is not still being pressed (No), it proceeds to step 32.

In step 32, the microcomputer of the VVT controller 250 increases the current limit value by a predetermined value. In short, the microcomputer of the VVT controller 250 takes into account that the set current limit value cannot keep up with the increase in engine speed of the engine 10 when pressing against the advance side stopper, and increases the current limit value by a predetermined value to address this. The microcomputer of the VVT controller 250 then proceeds to step 45.

In step 33, the microcomputer of the VVT controller 250 reads the actual rotational speed Nm of the electric motor 124 from the motor rotational speed sensor 46 and determines whether this is equal to or less than a predetermined rotational speed. In other words, the microcomputer of the VVT controller 250 determines whether the rotational speed of the intake camshaft 36, which is closely related to the actual rotational speed Nm of the electric motor 124 when pressing against the retard side stopper, is equal to or less than a predetermined value. If the microcomputer of the VVT controller 250 determines that the actual rotational speed Nm of the electric motor 124 is equal to or less than the predetermined rotational speed (Yes), it proceeds to step 34. On the other hand, if the microcomputer of the VVT controller 250 determines that the actual rotational speed Nm of the electric motor 124 is not equal to or less than the predetermined rotational speed, in other words, if it determines that the actual rotational speed Nm of the electric motor 124 is greater than the predetermined rotational speed (No), it proceeds to step 35.

In step 34, the microcomputer of the VVT controller 250 turns off the power supply to the electric motor 124. In short, when the rotational speed of the intake camshaft 36 is below a predetermined value, the microcomputer of the VVT controller 250 stops supplying current to the electric motor 124 to reduce unnecessary power consumption, because the cam torque of the intake camshaft 36 can press it against the retard side stopper. The microcomputer of the VVT controller 250 then proceeds to step 35.

In step 35, the microcomputer of the VVT controller 250 determines whether the determination flag in the previous control cycle was "FALSE," in other words, whether the stopper was not pressed during the previous control cycle. If the microcomputer of the VVT controller 250 determines that the determination flag in the previous control cycle was "FALSE" (Yes), it proceeds to step 36. On the other hand, if the microcomputer of the VVT controller 250 determines that the determination flag in the previous control cycle was not "FALSE," in other words, whether the stopper was pressed during the previous control cycle (No), it proceeds to step 41.

In step 36, the microcomputer of the VVT controller 250 determines whether the determination flag for the current control cycle is "TRUE," in other words, whether the stopper is being pressed against in the current control cycle. If the microcomputer of the VVT controller 250 determines that the determination flag for the current control cycle is "TRUE" (Yes), it proceeds to step 37. On the other hand, if the microcomputer of the VVT controller 250 determines that the determination flag for the current control cycle is not "TRUE," in other words, whether the stopper is not being pressed against in the current control cycle (No), it proceeds to step 41.

In step 37, the microcomputer of the VVT controller 250 determines whether the learned value on the retard side is equal to or less than the actual current value when the stopper is pressed against it. If the microcomputer of the VVT controller 250 determines that the learned value on the retard side is equal to or less than the actual current (Yes), it proceeds to step 38. On the other hand, if the microcomputer of the VVT controller 250 determines that the learned value on the retard side is not equal to or less than the actual current value, i.e., is greater than the actual current value (No), it proceeds to step 40.

In step 38, the microcomputer of the VVT controller 250 sets the current limit value to the actual current value when determining whether the stopper is being pressed against it.

In step 39, the microcomputer of the VVT controller 250 sets the retard side learning value to the actual current value at the time of stopper pressing determination. The microcomputer of the VVT controller 250 then proceeds to step 41.

In step 40, the microcomputer of the VVT controller 250 adopts the retarded learning value as the current limit value. The microcomputer of the VVT controller 250 then proceeds to step 41.

In step 41, the microcomputer of the VVT controller 250 reads the actual rotational speed Nm of the electric motor 124 from the motor rotational speed sensor 46 and determines whether this is 0, in other words, whether the engine 10 is being pressed against the stopper when stopped. If the microcomputer of the VVT controller 250 determines that the actual rotational speed Nm of the electric motor 124 is 0 (Yes), it proceeds to step 42. On the other hand, if the microcomputer of the VVT controller 250 determines that the actual rotational speed Nm of the electric motor 124 is not 0 (No), it proceeds to step 45.

In step 42, the microcomputer of the VVT controller 250 increases the current limit value by a predetermined value. That is, the microcomputer of the VVT controller 250 increases the current limit value by a predetermined value, taking into consideration that, for example, the cam torque of the intake camshaft 36 when the engine 10 is stopped may prevent the VVT mechanism 100 from operating at the current current limit value.

In step 43, the microcomputer of the VVT controller 250 determines whether the current limit value is equal to or greater than a predetermined current upper limit value, in other words, whether the intake camshaft 36 is being pressed against the stopper against the cam torque. If the microcomputer of the VVT controller 250 determines that the current limit value is equal to or greater than the current upper limit value (Yes), it proceeds to step 44. On the other hand, if the microcomputer of the VVT controller 250 determines that the current limit value is not equal to or greater than the current upper limit value, in other words, whether the intake camshaft 36 is not being pressed against the stopper against the cam torque (No), it proceeds to step 45.

In step 44, the microcomputer of the VVT controller 250 turns off the power supply to the electric motor 124. In short, the microcomputer of the VVT controller 250 determines that pressing against the stopper has been completed during the engine 10 stopping process, and stops the supply of current to the electric motor 124, for example, to reduce unnecessary power consumption.

In step 45, the microcomputer of the VVT controller 250 determines whether the current command value calculated in step 11 is greater than the current limit value. If the microcomputer of the VVT controller 250 determines that the current command value is greater than the current limit value (Yes), it proceeds to step 46. On the other hand, if the microcomputer of the VVT controller 250 determines that the current command value is not greater than the current limit value, in other words, that the current command value is equal to or less than the current limit value (No), it proceeds to step 47.

In step 46, the microcomputer of the VVT controller 250 sets the current command value to the current limit value. In short, the microcomputer of the VVT controller 250 limits the current command value to the current limit value.

In step 47, the microcomputer of the VVT controller 250 supplies a current corresponding to the current command value to the electric motor 124, and performs feedback control of the electric motor 124, for example, by PID control or PI control. As a result, the electric motor 124 of the VVT mechanism 100 is subjected to speed feedback control.

In step 48, the microcomputer of the VVT controller 250 determines whether the pressure against the stopper has been released, specifically, whether the pressure against the stopper was applied in the previous control cycle and whether the pressure against the stopper is not applied in the current control cycle. If the microcomputer of the VVT controller 250 determines that the pressure against the stopper has been released (Yes), it proceeds to step 49. On the other hand, if the microcomputer of the VVT controller 250 determines that the pressure against the stopper has not been released (No), it terminates the VVT control processing for the current control cycle.

In step 49, since the pressure against the stopper has been released, the microcomputer of the VVT controller 250 clears the integral term in the feedback control. By clearing the integral term in the feedback control, it is possible to suppress a decrease in controllability after the stopper pressure is released. The microcomputer of the VVT controller 250 then ends the VVT control processing for this control cycle.

According to this VVT control process, if it is determined that the electric motor 124 is not being pressed against the stopper, and the absolute value of the deviation between the target speed and the actual speed of the electric motor 124 remains above a predetermined lower limit and below a predetermined upper limit for a predetermined period of time, it is determined that the electric motor 124 is being pressed against the stopper. If it is determined that the electric motor 124 is being pressed against the stopper, the actual current value of the current being supplied to the electric motor 124 at that time is saved, and a determination flag indicating the determination result of whether the electric motor 124 is being pressed against the stopper is set to "TRUE." On the other hand, if it is determined that the electric motor 124 is being pressed against the stopper, and the sign of the deviation between the target speed and the actual speed of the electric motor 124 is inverted between the previous control cycle and the current control cycle, the determination flag is cleared to "FALSE." Therefore, the deviation between the target speed and the actual speed of the electric motor 124 can be used to determine whether the electric motor 124 has been pressed against the stopper or whether the stopper has been released.

If it is determined that the stopper is being pressed, if the speed deviation of the electric motor 124 is equal to or greater than 0, it is determined that the stopper is being pressed against the advance side stopper, whereas if the speed deviation of the electric motor 124 is less than 0, i.e., a negative value, it is determined that the stopper is being pressed against the retard side stopper. In short, by determining the rotation direction of the electric motor 124 according to the sign of the speed deviation of the electric motor 124, it is possible to determine whether the stopper is being pressed against the advance side stopper or the retard side stopper.

If it is determined that the stopper is being pressed against the advance angle side, and the stopper was not pressed against in the previous control cycle but is being pressed against in the current control cycle, a determination is made as to whether the advance angle side learned value is equal to or less than the actual current value at the time of the determination that the stopper was being pressed against. If the advance angle side learned value is equal to or less than the actual current value, the advance angle side learned value is determined to be inappropriate, and the current limit value is set to the actual current value, and the advance angle side learned value is also set to the actual current value. On the other hand, if the advance angle side learned value is greater than the actual current value at the time of the determination that the stopper was being pressed against the stopper, the advance angle side learned value is determined to be appropriate, and the advance angle side learned value is adopted as the current limit value. Therefore, as a countermeasure for when the stopper is not being pressed against the current limit value, a learned value for limiting the advance angle side current can be learned.

If the actual rotational speed Nm of the electric motor 124 is then 0, i.e., if the engine 10 is being pressed against the stopper during the process of stopping, the current limit value is increased by a predetermined value to enable the electric motor 124 of the VVT mechanism 100 to rotate against the cam torque of the intake camshaft 36. Then, when the current limit value reaches a predetermined current upper limit value, it is determined that the electric motor 124 is being pressed against the stopper, and power to the electric motor 124 is turned off. Therefore, if the engine 10 is being pressed against the stopper during the process of stopping, power to the electric motor 124 is turned off, thereby reducing unnecessary power consumption.

To press against the advance side stopper, the electric motor 124 needs to rotate faster than the rotational speed of the intake camshaft 36. Therefore, by limiting the current value supplied to the electric motor 124, the rotational speed of the electric motor 124 may fall below the rotational speed of the intake camshaft 36, as shown in Figure 10, and it may become impossible to press against the advance side stopper. Therefore, if it is not possible to continue pressing against the advance side stopper, the current limit value is increased by a predetermined value, as shown in Figure 11, so that it becomes possible to press against the advance side stopper.

On the other hand, if it is determined that the electric motor 124 is being pressed against the retard side stopper, and the actual rotational speed Nm of the electric motor 124 is equal to or lower than a predetermined rotational speed, i.e., the rotational speed of the intake camshaft 36 is equal to or lower than a predetermined value, it is determined that the cam torque of the intake camshaft 36 can be used to press the electric motor 124 against the retard side stopper. If it is determined that the cam torque can be used to press the electric motor 124 against the retard side stopper, the power supply to the electric motor 124 is turned off to reduce unnecessary power consumption.

Furthermore, if the stopper was not pressed against the previous control cycle but is pressed against the stopper in the current control cycle, a determination is made as to whether the retard side learned value is equal to or less than the actual current value when the stopper is pressed against the stopper. If the retard side learned value is equal to or less than the actual current, the retard side learned value is determined to be inappropriate, and the current limit value is set to the actual current value, and the retard side learned value is also set to the actual current value. On the other hand, if the retard side learned value is greater than the actual current value when the stopper is pressed against the stopper, the retard side learned value is determined to be appropriate, and the retard side learned value is adopted as the current limit value. Therefore, as a countermeasure for when the stopper is not pressed against the current limit value, a learned value for limiting the retard side current can be learned.

If the actual rotational speed Nm of the electric motor 124 is then 0, i.e., if the engine 10 is being pressed against the stopper during the process of stopping, the current limit value is increased by a predetermined value to enable the electric motor 124 of the VVT mechanism 100 to rotate against the cam torque of the intake camshaft 36. Then, when the current limit value reaches a predetermined current upper limit value, it is determined that the electric motor 124 is being pressed against the stopper, and power to the electric motor 124 is turned off. Therefore, if the engine 10 is being pressed against the stopper during the process of stopping, power to the electric motor 124 is turned off, thereby reducing unnecessary power consumption.

In this way, when advance or retard processing is executed, or when it is determined that the stopper is not being pressed in the current control cycle, if the current command value is greater than the current limit value, the current command value is limited to the current limit value. The electric motor 124 is then feedback-controlled in accordance with the current command value. Therefore, as shown in Figure 12, when the stopper is being pressed, the current value of the current supplied to the electric motor 124 is limited, preventing excessive current from flowing through the electric motor 124.

In addition, when the pressure against the stopper is released, the integral term of the feedback control of the electric motor 124 is cleared, thereby suppressing a decrease in controllability after the pressure against the stopper is released.

In addition, a person skilled in the art will easily understand that new embodiments can be created by omitting parts of the technical ideas of the above embodiments, combining parts as appropriate, or replacing parts with well-known technology.

For example, the engine 10 installed in the vehicle is not limited to a gasoline engine, but may also be a diesel engine. Furthermore, the current limit value for limiting the current supplied to the electric motor 124 of the VVT mechanism 100 may be a fixed value set, for example, taking into consideration the characteristics of the electric motor 124. Furthermore, it goes without saying that this embodiment can be applied not only to the VVT mechanism 100, but also to any well-known controlled device equipped with a stopper that limits the rotation angle of a rotor driven by a motor.

36... Intake camshaft 36A... Stopper groove 46... Motor rotation speed sensor 100... VVT mechanism 102... Timing sprocket (rotating body) 102A... Stopper protrusion 124... Electric motor 250... VVT controller (motor control device)

Claims (13)

A control device for a motor that rotates a rotor provided with a stopper that restricts the rotation angle by speed feedback control,
when the absolute value of the deviation between the target rotation speed of the motor and the actual rotation speed of the motor continues to be equal to or greater than a predetermined lower limit value and equal to or less than a predetermined upper limit value for a predetermined time, it is determined that the rotation angle of the rotor is restricted by the stopper, and the current supplied to the motor is restricted.
Motor control device. The current supplied to the motor is limited to a predetermined current limit value.
The motor control device according to claim 1 . when the absolute value of the deviation between the target rotation speed of the motor and the actual rotation speed of the motor continues to be equal to or greater than a predetermined lower limit value and equal to or less than a predetermined upper limit value for a predetermined period of time, a learned value of the current limit value is learned in accordance with the actual current value of the current supplied to the motor.
The motor control device according to claim 2 . determining a rotation direction of the motor according to a sign of a deviation between a target rotation speed of the motor and an actual rotation speed of the motor, and learning the learned values corresponding to the rotation directions of the motor;
The motor control device according to claim 3 . When the learned value is equal to or less than the actual current value, the learned value is adopted as the current limit value.
The motor control device according to claim 3 . When the current limit value reaches a predetermined current upper limit value, power supply to the motor is stopped.
The motor control device according to claim 5 . When the rotation of the motor is stopped by limiting the current supplied to the motor, the current limit value is gradually increased.
The motor control device according to claim 2 . in a state in which the current supplied to the motor is limited, a determination is made as to whether or not the rotation angle of the rotating body is restricted by the stopper in accordance with the deviation between the target rotation speed of the motor and the actual rotation speed of the motor when the absolute value of the deviation between the target rotation speed of the motor and the actual rotation speed of the motor continues to be in a state in which the deviation is equal to or greater than a predetermined lower limit value and is equal to or less than a predetermined upper limit value for a predetermined period of time, and the deviation between the current target rotation speed of the motor and the actual rotation speed of the motor; and if it is determined that the rotation angle of the rotating body is not restricted by the stopper, the current limit value is gradually increased.
The motor control device according to claim 2 . A control device for a motor that rotates a rotating body provided with a stopper that restricts the rotation angle by speed feedback control,
when the absolute value of the deviation between the target rotation speed of the motor and the actual rotation speed of the motor continues to be equal to or greater than a predetermined lower limit value and equal to or less than a predetermined upper limit value for a predetermined time, it is determined that the rotation angle of the rotor is restricted by the stopper, and the current supplied to the motor is restricted.
How to control a motor. a control device for the motor that limits the current supplied to the motor to a predetermined current limit value;
The motor control method according to claim 9 . the motor control device learns a learned value of the current limit value in accordance with an actual current value of the current supplied to the motor when a state in which an absolute value of a deviation between a target rotation speed of the motor and an actual rotation speed of the motor remains equal to or greater than a predetermined lower limit value and equal to or less than a predetermined upper limit value for a predetermined period of time;
The motor control method according to claim 10 . the motor control device determines a rotation direction of the motor according to a sign of a deviation between a target rotation speed of the motor and an actual rotation speed of the motor, and learns the learned values corresponding to the rotation directions of the motor.
The motor control method according to claim 11 . the motor control device adopts the learned value as the current limit value when the learned value is equal to or less than the actual current value;
The motor control method according to claim 11 .