Control device for variable valve timing mechanism

Abstract

To suppress overshoot to improve controllability by early correcting the rotation angle of a camshaft.SOLUTION: A control device for a VVT mechanism is input with a crank signal from a crank angle sensor, which detects the teeth of a crank signal plate having an untoothed portion and outputs a pulse-shaped crank signal, and with a cam signal from a cam angle sensor, which outputs a cylinder discrimination signal, and changes the phase angle of a camshaft relative to a crankshaft to change valve timing. At this time, the control device for the VVT mechanism controls the VVT mechanism to a predetermined angle when an engine is stopped. Furthermore, when an untoothed portion is detected from the crank signal at the time of engine start-up (S20), the control device for the VVT mechanism corrects the camshaft rotation angle in accordance with the camshaft rotation angle identified by the untoothed portion (S21), and controls the VVT mechanism to a target angle in accordance with the corrected camshaft rotation angle.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a control device for a variable valve timing (VVT) mechanism that changes valve timing by varying the rotational phase of a camshaft relative to a crankshaft. [Background technology]

[0002] As described in JP 2020-79581 A (Patent Document 1), the control device for the VVT ​​mechanism estimates the rotation phase of the camshaft relative to the crankshaft in consideration of the cam torque estimated from the crank signal and the cam signal. Here, the control device for the VVT ​​mechanism obtains the rotation angle of the camshaft from the crank signal and the cam signal, and estimates the cam torque from the rotation angle of the camshaft by referring to a cam torque table that defines the relationship between the rotation angle of the camshaft and the cam torque. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-79581 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, since the rotation angle of the camshaft is unknown immediately after the engine is started, the rotation angle of the camshaft is obtained in synchronization with the crank signal, starting from a predetermined value, which is a default value. In this case, the rotation angle of the camshaft is not calibrated until the cam signal is input after a missing tooth is detected from the crank signal, in other words, until the normal cam signal is detected, and the cam torque is estimated based on the rotation angle of the camshaft that includes an error. If the VVT ​​mechanism is controlled using the cam torque estimated in this way, the period during which the estimated value of the cam torque differs from the actual value becomes long, which may result in overshooting and reduced controllability.

[0005] SUMMARY OF THE PRESENT DISCLOSURE In view of the above, an object of the present invention is to provide a control device for a VVT mechanism that suppresses overshoot and improves controllability by early calibrating the rotation angle of the camshaft. [Means for solving the problem]

[0006] According to one embodiment, the control device of the VVT ​​mechanism inputs a crank signal from a crank angle sensor that detects a tooth portion of a crank signal plate on which a missing tooth portion is formed and outputs a pulse-shaped crank signal, and a cam signal from a cam angle sensor that outputs a cylinder discrimination signal, and changes the phase angle of the camshaft relative to the crankshaft to change the valve timing. At this time, the control device of the VVT ​​mechanism controls the VVT ​​mechanism to a predetermined angle when the engine is stopped. Also, when the control device of the VVT ​​mechanism detects a missing tooth portion from the crank signal when the engine is started, the control device of the VVT ​​mechanism calibrates the rotation angle of the camshaft according to the rotation angle of the camshaft specified by the missing tooth portion, and controls the VVT ​​mechanism to a target angle according to the calibrated rotation angle of the camshaft.

[0007] According to another embodiment, a control device for the VVT ​​mechanism receives a crank signal from a crank angle sensor that detects teeth on a crank signal plate having a missing tooth portion and outputs a pulse-shaped crank signal, and a cam signal from a cam angle sensor that outputs a cylinder discrimination signal, and changes the phase angle of the camshaft relative to the crankshaft to change the valve timing. At this time, when the cam signal is received at engine start, the control device for the VVT ​​mechanism calibrates the rotation angle of the camshaft according to the rotation angle of the camshaft specified by the cam signal, and controls the VVT ​​mechanism to a target angle according to the calibrated rotation angle of the camshaft. Effect of the Invention

[0008] According to the present invention, in control of the VVT ​​mechanism, the rotation angle of the camshaft is calibrated early, thereby making it possible to suppress overshoot and improve controllability. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an example of a control system for a four-stroke engine. [Diagram 2] FIG. 4 is a plan view showing an example of a crank signal plate. [Diagram 3] FIG. 4 is a plan view showing an example of a cam signal plate. [Figure 4] FIG. 2 is a perspective view showing an example of a VVT mechanism. [Diagram 5] FIG. 2 is an explanatory diagram of various parameters used in engine control. [Figure 6] FIG. 1 is an explanatory diagram illustrating a problem in the conventional technology. [Figure 7] 5 is a flowchart showing an example of a stop time process in the first embodiment. [Figure 8] 5 is a flowchart showing an example of a start-up process in the first embodiment. [Figure 9] FIG. 4 is an explanatory diagram showing the operation and effect of the first embodiment. [Figure 10] 10 is a flowchart showing an example of a start-up process in the second embodiment. [Figure 11] 13 is an explanatory diagram showing the operation and effect of the second embodiment. FIG. [Figure 12] FIG. 2 is an explanatory diagram showing advantages of the first and second embodiments over the conventional techniques. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] 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 a control system for a four-stroke engine mounted on a vehicle such as an automobile.

[0011] The engine 100 includes a cylinder block 110, a piston 120, a crankshaft 130, a connecting rod 140, and a cylinder head 150. A cylinder bore 110A is formed in the cylinder block 110, into which the piston 120 is inserted so as to be capable of reciprocating. A crankshaft 130 is disposed in a lower portion of the cylinder block 110 via a bearing (not shown) so as to be rotatable relative to the cylinder block 110. The piston 120 is coupled to the crankshaft 130 via the connecting rod 140 so as to be rotatable relative to the crankshaft 130.

[0012] The cylinder head 150 is formed with an intake port 150A for introducing intake air and an exhaust port 150B for discharging exhaust gas. The cylinder head 150 is fastened to the upper surface of the cylinder block 110, so that an area defined by the cylinder bore 110A of the cylinder block 110, the crown surface of the piston 120, and the lower surface of the cylinder head 150 functions as a combustion chamber 160. An intake valve 180 that is driven to open and close by an intake camshaft 170 is disposed at an open end of the intake port 150A facing the combustion chamber 160. An exhaust valve 200 that is driven to open and close by an exhaust camshaft 190 is disposed at an open end of the exhaust port 150B facing the combustion chamber 160.

[0013] An electromagnetic fuel injection valve 210 that directly injects fuel into the combustion chamber 160, and an ignition plug 220 that ignites and burns a mixture of fuel and intake air are attached to predetermined positions of the cylinder head 150 facing the combustion chamber 160. Note that the fuel injection valve 210 is not limited to a configuration that directly injects fuel into the combustion chamber 160, but may also be a configuration that injects fuel into the intake port 150A, or a configuration that has both of these.

[0014] A crank signal plate 230 is attached to the end of the crankshaft 130. As shown in FIG. 2, the crank signal plate 230 is a detectable member in which a disk-shaped plate portion 230A and a plurality of teeth portions 230B extending radially outward from the outer circumferential end of the plate portion 230A are integrated. In addition, the crank signal plate 230 is formed with a tooth-missing portion 230C that defines the angle reference at a crank angle of 360° by removing a part of the tooth portion 230B. Here, in the example of the crank signal plate 230 shown in FIG. 2, the tooth-missing portion 230C is formed by removing two teeth portions 230B, but the tooth-missing portion 230C may be formed by removing any number of teeth portions 230B.

[0015] In the case of a four-cylinder engine, the crank signal plate 230 has, for example, 34 teeth 230B with a predetermined angle of 10°, and a tooth-missing portion 230C spanning 30° in which two teeth 230B are missing. The crank signal plate 230 may have two or more tooth-missing portions 230C.

[0016] A crank angle sensor 240 is attached to the lower part of the cylinder block 110 at a predetermined position facing the outer circumferential end of the crank signal plate 230. The crank angle sensor 240 detects the teeth 230B of the crank signal plate 230 and outputs a pulse-like crank signal CRS.

[0017] A cam signal plate 250 is attached to the end of the intake camshaft 170. As shown in Fig. 3, the cam signal plate 250 is a detectable member that is an integrated member of a disk-shaped plate portion 250A and an arc-shaped extension portion 250B that extends radially outward from a part of the outer circumferential end of the plate portion 250A.

[0018] A cam angle sensor 260 is attached to an upper portion of the cylinder head 150 at a predetermined position facing the outer circumferential end of the cam signal plate 250, which detects the extension portion 250B of the cam signal plate 250 and outputs a rectangular cam signal CMS. The extension portion 250B of the cam signal plate 250 is formed so that, for example, at two tooth missing positions where the crank angle sensor 240 detects the tooth missing portion 230C of the crank signal plate 230 during two rotations of the crankshaft 130, a LOW signal is output at the tooth missing position in the first rotation and a HIGH signal is output at the tooth missing position in the second rotation. Therefore, the cam angle sensor 260 outputs a cam signal CMS of different levels depending on whether or not the extension portion 250B of the cam signal plate 250 is detected.

[0019] By monitoring such a cam signal CMS, it is possible to distinguish whether the crankshaft 130, which rotates at twice the rotation speed of the intake camshaft 170, is rotating in its first rotation (0° to 360°) corresponding to 0° to 180° of the intake camshaft 170, or in its second rotation (360° to 720°) corresponding to 180° to 360° of the intake camshaft 170. In other words, it is possible to distinguish whether the crankshaft 130 is rotating in its first rotation or in its second rotation while the intake camshaft 170 rotates once. The cam signal plate 250 is not limited to the shape shown in FIG. 3, and may have any shape as long as it can output signals of different levels at the tooth-missing position in the first rotation and the tooth-missing position in the second rotation.

[0020] An electric VVT mechanism 270 is further attached to the end of the intake camshaft 170, which changes the valve timing of the intake valve 180 by changing the rotation phase of the intake camshaft 170 relative to the crankshaft 130. As shown in FIG. 4, the VVT ​​mechanism 270 is integrated with a cam sprocket 270A around which a cam chain for transmitting the rotational driving force of the crankshaft 130 is wound, and the valve timing of the intake camshaft 170 is advanced or retarded by rotating the cam sprocket 270A relative to the intake camshaft 170 by an electric motor 270B (actuator) with a built-in speed reducer. Here, the element indicated by the reference symbol 270C in FIG. 4 is a connector for connecting a harness for supplying a driving current to the electric motor 270B. The VVT ​​mechanism 270 is not limited to the intake camshaft 170, and may be provided on at least one of the intake camshaft 170 and the exhaust camshaft 190. Furthermore, the VVT ​​mechanism 270 is not limited to having the configuration shown in FIG. 4, and may have a well-known configuration.

[0021] The crank signal CRS of the crank angle sensor 240 and the cam signal CMS of the cam angle sensor 260 are input to an engine control module (ECM) 280 incorporating a microcomputer 280A. In addition to the output signals of the crank angle sensor 240 and the cam angle sensor 260, the engine control module 280 also receives output signals from a rotation speed sensor 290 that detects the rotation speed Ne of the engine 100, a load sensor 300 that detects the load Q of the engine 100, a water temperature sensor 310 that detects the water temperature Tw of the engine 100, and an air-fuel ratio sensor 320 that detects the air-fuel ratio A / F in the exhaust. Here, as the load Q of the engine 100, for example, a state quantity closely related to the required torque of the engine 100, such as an intake flow rate, an intake negative pressure, a supercharging pressure, an accelerator opening, or a throttle opening, can be used. The engine control module 280 is an example of a control device for the VVT ​​mechanism 270. Moreover, the engine control module 280 may calculate the rotation speed Ne from the crank signal CRS of the crank angle sensor 240 instead of reading the rotation speed Ne from the rotation speed sensor 290.

[0022] The engine control module 280 executes application programs stored in a non-volatile memory (not shown) of the microcomputer 280A, thereby electronically controlling the fuel injector 210, the spark plug 220, and the electric motor 270B of the VVT ​​mechanism 270 in response to the output signals of the crank angle sensor 240, the cam angle sensor 260, the rotational speed sensor 290, the load sensor 300, the water temperature sensor 310, and the air-fuel ratio sensor 320.

[0023] At this time, in consideration of the fact that the crank signal CRS of the crank angle sensor 240 is generated every 10° and has low resolution, the engine control module 280 uses a multiplication circuit (not shown) built into the microcomputer 280A to generate a multiplied crank signal CRS' by multiplying (doubling the frequency) the crank signal CRS by 10, as shown in Fig. 5. Therefore, the multiplied crank signal CRS' indicates that the crankshaft 130 has rotated by 1°. Note that the multiplied crank signal CRS' is not limited to a configuration in which the crank signal CRS is multiplied by 10, and may be generated by multiplying the crank signal CRS by a predetermined factor in consideration of, for example, control accuracy.

[0024] Here, the multiplication circuit sequentially measures the output interval of two consecutive crank signals CRS, and generates a multiplied crank signal CRS' by multiplying the output interval of the previous crank signal CRS by 10. Furthermore, when two consecutive crank signals CRS sandwich a missing tooth position, the multiplication circuit generates a multiplied crank signal CRS' by multiplying the output interval of the previous crank signal CRS by 10. On the other hand, the multiplication circuit generates a multiplied crank signal CRS' by multiplying the output interval of the crank signal CRS immediately before the missing tooth position by 10, because the precision is poor immediately after the missing tooth position due to the missing tooth position.

[0025] Furthermore, the engine control module 280 uses a crank signal counter, a crank angle, and a crank angle counter as parameters used in fuel injection control, ignition control, and valve timing control, as shown in FIG.

[0026] The crank signal counter is a counter for determining whether or not the rotation angle of the crankshaft 130 is at a position corresponding to the missing tooth portion 230C of the crank signal plate 230. The crank signal counter counts up in synchronization with the crank signal CRS, and when the count value reaches or exceeds a missing tooth determination threshold value (predetermined threshold value), it is reset by the input of the next crank signal CRS.

[0027] The crank angle is, for example, a counter that starts from the top dead center (TDC) of the #1 cylinder and periodically counts from 0° to 720° of the crankshaft 130. The crank angle recognition value is counted up in synchronization with the crank signal CRS, and is reset when the top dead center of the #1 cylinder is detected.

[0028] The crank angle counter is a counter for controlling the fuel injection timing, the ignition timing, and the valve timing. The crank angle counter counts up in synchronization with a crank signal CRS' obtained by multiplying the crank signal CRS by 10, and is reset by the input of the next crank signal CRS after a tooth chipping determination is performed for a specific cylinder. At this time, the crank angle counter is updated successively taking into account the tooth chipping portion 230C of the crank signal plate 230.

[0029] The crank signal counter, crank angle and crank angle counter may be counted and reset by the engine control module 280, or may be counted and reset by a dedicated electronic circuit.

[0030] The engine control module 280 reads the rotation speed Ne and the load Q from the rotation speed sensor 290 and the load sensor 300, respectively, and calculates a basic fuel injection amount according to the engine operating state specified by the rotation speed Ne and the load Q. The engine control module 280 also reads the water temperature Tw from the water temperature sensor 310, and calculates a fuel injection amount obtained by correcting the basic fuel injection amount with the water temperature Tw. Furthermore, the engine control module 280 calculates the fuel injection timing and the ignition timing according to the rotation speed Ne, the load Q, and the fuel injection amount, respectively.

[0031] Then, when the rotation angle of crankshaft 130 specified by the crank angle counter reaches the fuel injection timing, engine control module 280 outputs a control signal corresponding to the fuel injection amount to fuel injector 210, causing fuel injector 210 to inject fuel into combustion chamber 160. Also, when the rotation angle of crankshaft 130 specified by the crank angle counter reaches the ignition timing, engine control module 280 outputs an operation signal to ignition plug 220, causing the mixture of fuel and intake air to ignite and burn. At this time, engine control module 280 reads air-fuel ratio A / F from air-fuel ratio sensor 320, and feedback controls fuel injector 210 so that the air-fuel ratio A / F in the exhaust approaches the target air-fuel ratio.

[0032] In addition to controlling the fuel injector 210 and the spark plug 220, the engine control module 280 electronically controls the VVT ​​mechanism 270 as described below. That is, the engine control module 280 calculates a target angle of the VVT ​​mechanism 270 according to the rotation speed Ne and the load Q read from the rotation speed sensor 290 and the load sensor 300, respectively. The engine control module 280 also obtains a rotation angle of the intake camshaft 170 according to the rotation angle of the crankshaft 130 specified by the crank angle counter and the cam signal CMS read from the cam angle sensor 260. Furthermore, the engine control module 280 refers to a cam torque table in which the rotation angle of the intake camshaft 170 and the cam torque are associated with each other, and estimates a cam torque according to the rotation angle of the intake camshaft 170 obtained as described above. Thereafter, engine control module 280 obtains a motor output torque corresponding to the drive current output to electric motor 270B of VVT mechanism 270, and estimates the actual angle (VVT angle) of VVT mechanism 270 from the estimated values ​​of this motor output torque and cam torque. Then, engine control module 280 feedback controls the drive current output to electric motor 270B of VVT mechanism 270 so that the VVT ​​angle estimated in this manner converges to the target angle.

[0033] By having engine control module 280 electronically control VVT mechanism 270 as described above, the phase angle of intake camshaft 170 relative to crankshaft 130 becomes an angle appropriate for the engine operating state, thereby simultaneously improving engine output, fuel economy, exhaust characteristics, etc.

[0034] Incidentally, the actual angle of the VVT ​​mechanism 270 is estimated according to the rotation angle of the crankshaft 130 specified by the crank angle counter and the cam signal CMS read from the cam angle sensor 260, as described above. However, since the rotation angle of the intake camshaft 170 is indefinite when the engine is stopped, the rotation angle of the intake camshaft 170 immediately after the engine is started is unknown. Therefore, in the conventional technology, as shown in FIG. 6, when the engine is started, the rotation angle of the intake camshaft 170 is sequentially updated in synchronization with the multiplied crank signal CRS', starting from a predetermined value that is a default value, and the cam torque and the actual angle of the VVT ​​mechanism 270 are estimated using this. Then, after the engine is started, when the initial cam signal CMS is input after the first tooth chipping determination is performed, this is determined to be a normal cam signal, and calibration is performed to set the rotation angle of the intake camshaft 170 to a rotation angle corresponding to the normal cam signal.

[0035] Therefore, in the conventional technology, the rotation angle of the intake camshaft 170 including an error was used during the period from the start of the engine until the normal cam signal was input, so that the period during which the estimated value of the cam torque shown by the dashed line and the actual value of the cam torque shown by the solid line diverged (mismatched) became long, as shown in Fig. 6. As a result, there was a possibility that an overshoot occurred and controllability was deteriorated.

[0036] Therefore, in this embodiment, the rotation angle of intake camshaft 170 is calibrated early by control that will be described in detail below, thereby suppressing overshoot and improving controllability.

[0037] <<First embodiment>> In the first embodiment, the engine control module 280 controls the VVT ​​mechanism 270 to a predetermined angle, for example, the most retarded position of the VVT ​​mechanism 270, when the engine is stopped. When the engine control module 280 detects the missing tooth portion 230C from the crank signal CRS at the time of engine start, the engine control module 280 calibrates the rotation angle of the intake camshaft 170 obtained from the multiplied crank signal CRS' with a predetermined value as the starting point at the time of engine start according to the rotation angle of the intake camshaft 170 specified by the missing tooth portion 230C. Specifically, the engine control module 280 sets the rotation angle of the intake camshaft 170 obtained from the multiplied crank signal CRS' with a predetermined value as the starting point at the time of engine start as the rotation angle of the intake camshaft 170 specified by the missing tooth portion 230C. Then, the engine control module 280 controls the VVT ​​mechanism 270 to a target angle according to the rotation angle of the intake camshaft 170 calibrated in this way. The engine control module 280 determines the cam torque according to the rotation angle of the intake camshaft 170 calibrated as described above, and estimates the phase angle of the intake camshaft 170 relative to the crankshaft 130 according to this cam torque (and so on below).

[0038] 7 shows an example of a stoppage process that is executed during a self-shutdown process by the microcomputer 280A of the engine control module 280 when the engine 100 is stopped. The stoppage process is executed according to an application program stored in the non-volatile memory of the microcomputer 280A.

[0039] In step 10 (abbreviated as "S10" in FIG. 7, and the same applies below), microcomputer 280A of engine control module 280 outputs a drive current to electric motor 270B of VVT mechanism 270, thereby controlling VVT mechanism 270 to the most retarded position.

[0040] 8 shows an example of a startup process that is repeatedly executed at predetermined time intervals by the microcomputer 280A of the engine control module 280 upon starting of the engine 100. The startup process is executed according to an application program stored in the non-volatile memory of the microcomputer 280A.

[0041] In step 20, the microcomputer 280A of the engine control module 280 determines whether or not it has detected the first missing tooth portion 230C of the crank signal plate 230 from the crank signal CRS. If the microcomputer 280A of the engine control module 280 determines that it has detected the first missing tooth portion 230C (Yes), it proceeds to step 21. On the other hand, if the microcomputer 280A of the engine control module 280 determines that it has not detected the first missing tooth portion 230C (No), it proceeds to step 22.

[0042] In step 21, the microcomputer 280A of the engine control module 280 calibrates the rotation angle of the intake camshaft 170 obtained from the multiplied crank signal CRS' with a predetermined value as a starting point, in accordance with the rotation angle of the intake camshaft 170 specified by the missing tooth portion 230C of the crank signal plate 230. Here, since the rotation angle of the intake camshaft 170 specified by the missing tooth portion 230C is not the normal cam signal described above, it may contain a slight error and may not be necessarily accurate.

[0043] In step 22, the microcomputer 280A of the engine control module 280 determines whether or not the cam signal CMS has been input from the cam angle sensor 260, in other words, whether or not the extension portion 250B of the cam signal plate 250 has been detected. If the microcomputer 280A of the engine control module 280 determines that the cam signal CMS has been input (Yes), the process proceeds to step 23. On the other hand, if the microcomputer 280A of the engine control module 280 determines that the cam signal CMS has not been input (No), the microcomputer 280A of the engine control module 280 ends the start-up process in the current control cycle.

[0044] In step 23, the microcomputer 280A of the engine control module 280 further calibrates the rotation angle of the intake camshaft 170 calculated from the multiplied crank signal CRS' with a predetermined value as a starting point in accordance with the rotation angle of the intake camshaft 170 specified by the cam signal CMS. Note that if the cam signal CMS is input after the initial detection of the missing tooth portion 230C, this cam signal CMS is a normal cam signal, so it is desirable to determine that the rotation angle of the intake camshaft 170 has been calibrated by the input of the normal cam signal and to end the start-up process that is repeatedly executed at predetermined time intervals in order to suppress an increase in the processing load.

[0045] According to these start-up and stop-up processes, when engine 100 is stopped, VVT mechanism 270 is controlled to the most retarded position, and, for example, valve timing can be set appropriate for starting engine 100. In addition, by controlling VVT mechanism 270 to the most retarded position when the engine is stopped, an error in a predetermined value that defines the rotation angle of intake camshaft 170 at engine start is reduced, and controllability can be improved until the rotation angle is finally calibrated.

[0046] Then, when engine 100 is started, the rotation angle of intake camshaft 170, which has been successively updated starting from an initial value, is calibrated upon detection of missing tooth portion 230C of crank signal plate 230 attached to the end of crankshaft 130. Also, the rotation angle of intake camshaft 170 is calibrated upon input of cam signal CMS. In short, when engine 100 is started, calibration is performed in response to detection of missing tooth portion 230C, and calibration is performed in response to input of cam signal CMS.

[0047] 9, the rotation angle of intake camshaft 170 is calibrated early after engine start without waiting for the input of the normal cam signal, and therefore the period during which the rotation angle of intake camshaft 170 deviates from the actual value is shortened compared to the conventional technology (see FIG. 6), thereby improving controllability. Although the rotation angle of intake camshaft 170 calibrated in this manner may contain some error as described above, it is further calibrated in response to the input of the normal cam signal, and therefore in the subsequent processing, VVT mechanism 270 can be controlled according to the rotation angle that contains only the measurement error.

[0048] <<Second embodiment>> In the second embodiment, when the cam signal CMS is input at the time of engine start, the engine control module 280 calibrates the rotation angle of the intake camshaft 170 obtained from the multiplied crank signal CRS' with a predetermined value as a starting point at the time of engine start in accordance with the rotation angle of the intake camshaft 170 specified by the cam signal CMS. Specifically, the engine control module 280 sets the rotation angle of the intake camshaft 170 obtained from the multiplied crank signal CRS' with a predetermined value as a starting point at the time of engine start as the rotation angle of the intake camshaft 170 specified by the cam signal CMS. Then, the engine control module 280 controls the VVT ​​mechanism 270 to a target angle in accordance with the rotation angle of the intake camshaft 170 calibrated in this way.

[0049] 10 shows an example of a start-up process that is repeatedly executed at predetermined time intervals by the microcomputer 280A of the engine control module 280 when the engine 100 is started. Note that, unlike the first embodiment, in the second embodiment, it is not always necessary to execute the stop-up process that is executed when the engine 100 is stopped.

[0050] In step 30, the microcomputer 280A of the engine control module 280 determines whether or not the cam signal CMS has been input from the cam angle sensor 260. If the microcomputer 280A of the engine control module 280 determines that the cam signal CMS has been input (Yes), the process proceeds to step 31. On the other hand, if the microcomputer 280A of the engine control module 280 determines that the cam signal CMS has not been input (No), the microcomputer 280A of the engine control module 280 ends the start-up process in the current control cycle.

[0051] In step 31, the microcomputer 280A of the engine control module 280 calibrates the rotation angle of the intake camshaft 170 calculated from the multiplied crank signal CRS' with a predetermined value as a starting point, in accordance with the rotation angle of the intake camshaft 170 specified by the cam signal CMS. Since the rotation angle of the intake camshaft 170 has been calibrated by inputting the cam signal CMS, it is desirable to terminate the start-up process that is repeatedly executed at predetermined time intervals in order to suppress an increase in the processing load.

[0052] According to this stop-time processing, when the engine 100 is started, the rotation angle of the intake camshaft 170, which has been successively updated starting from an initial value, is calibrated upon input of the cam signal CMS due to detection of the extension portion 250B of the cam signal plate 250 attached to the end of the intake camshaft 170. At this time, since the cam signal CMS can accurately identify the rotation angle of the intake camshaft 170 (however, a measurement error is included), it becomes possible to calibrate the rotation angle of the intake camshaft 170 early after the engine is started, without performing a two-stage calibration as in the first embodiment.

[0053] Therefore, as shown in FIG. 11, the rotation angle of the intake camshaft 170 is calibrated early after the engine is started without waiting for the input of the normal cam signal, and therefore the period during which the rotation angle of the intake camshaft 170 deviates from the actual value is shortened, compared with the conventional technology (see FIG. 6), and controllability can be improved. Then, in the subsequent processing, the VVT ​​mechanism 270 can be controlled according to the rotation angle including only the measurement error. Here, in the second embodiment, as is clear from FIG. 11, the rotation angle of the intake camshaft 170 is calibrated without waiting for the detection of the tooth-missing portion 230C of the crank signal plate 230, which is particularly advantageous when the cam signal CMS is input before the detection of the tooth-missing portion 230C of the crank signal plate 230.

[0054] By implementing the control according to the first and second embodiments, the results shown in FIG. 12 can be achieved. That is, in the conventional technology, when the actual VVT angle shown by the thick line converges to the target angle shown by the thin line, a certain amount of time t1 is required until the rotation angle of the intake camshaft 170 is calibrated by inputting the regular cam signal, and the overshoot from the target angle is relatively large. In contrast, in the proposed technology of this embodiment, when the actual VVT angle shown by the thick line converges to the target angle shown by the thin line, the rotation angle of the intake camshaft 170 is calibrated by detecting the missing tooth portion 230C or inputting the cam signal CMS without waiting for the input of the regular cam signal. Therefore, as is clear from FIG. 12, the time t2 until the rotation angle of the intake camshaft 170 is calibrated is shorter than in the conventional technology, and this makes it possible to suppress overshoot from the target angle.

[0055] Furthermore, 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 of the embodiments as appropriate, or replacing parts of the embodiments with well-known technology.

[0056] As an example, engine 100 mounted on a vehicle is not limited to a gasoline engine, and may be a diesel engine, etc. Furthermore, engine control module 280 may be divided into a module that electronically controls fuel injector 210 and spark plug 220, and a module that electronically controls VVT mechanism 270. [Explanation of symbols]

[0057] 130...crankshaft, 170...intake camshaft (camshaft), 230...crank signal plate, 230B...tooth portion, 230C...missing tooth portion, 240...crank angle sensor, 260...cam angle sensor, 270...VVT mechanism, 280...engine control module (control device), CRS...crank signal, CMS...cam signal

Claims

1. A control device for a variable valve timing mechanism, which receives a crank signal from a crank angle sensor that detects teeth of a crank signal plate having a missing tooth portion and outputs a pulse-shaped crank signal, and a cam signal from a cam angle sensor that outputs a cylinder discrimination signal, and changes a phase angle of a camshaft relative to a crankshaft to change valve timing, Controlling the variable valve timing mechanism to a predetermined angle when the engine is stopped; when the missing tooth portion is detected from the crank signal at engine start, a rotation angle of the camshaft is calibrated according to a rotation angle of the camshaft specified by the missing tooth portion; controlling the variable valve timing mechanism to a target angle in accordance with the calibrated rotation angle of the camshaft; A control device for a variable valve timing mechanism.

2. The predetermined angle is a most retarded position of the variable valve timing mechanism. The control device for a variable valve timing mechanism according to claim 1 .

3. A control device for a variable valve timing mechanism, which receives a crank signal from a crank angle sensor that detects teeth of a crank signal plate having a missing tooth portion and outputs a pulse-shaped crank signal, and a cam signal from a cam angle sensor that outputs a cylinder discrimination signal, and changes a phase angle of a camshaft relative to a crankshaft to change valve timing, When the cam signal is input at the time of starting the engine, a rotation angle of the camshaft is calibrated in accordance with the rotation angle of the camshaft specified by the cam signal; controlling the variable valve timing mechanism to a target angle in accordance with the calibrated rotation angle of the camshaft; A control device for a variable valve timing mechanism.

4. A cam torque is calculated according to the rotation angle of the calibrated camshaft. estimating a phase angle of the camshaft relative to the crankshaft in response to the cam torque; The control device for a variable valve timing mechanism according to any one of claims 1 to 3.

5. The calibration of the rotation angle of the camshaft is performed every time the cam signal is input after the calibration is performed in response to the detection of the missing tooth portion. The control device for a variable valve timing mechanism according to claim 4.

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