CONTROL DEVICE FOR A VARIABLE VALVE CONTROL MECHANISM

Abstract

A control device for a variable valve control mechanism (14), comprising: a crank angle sensor (4) which outputs a crank angle signal in response to a rotation of a crankshaft (2), wherein the crank angle signal is preset to specify at least two reference positions; a cam sensor (5) which outputs at least two cam signal pulses in response to a rotation of an intake camshaft (3) to open and close an engine valve; an actuator (6) that rotates the intake camshaft (3) relative to the crankshaft (2) so that the actuator (6) can change a rotational phase angle of the intake camshaft (3) relative to the crankshaft (2); and a control unit (7) configured to calculate an actual rotational phase angle of the intake camshaft at the time of detection of the first camshaft signal pulse, based on a first cam signal pulse detected after the start of the starting process and a first reference position of the crankshaft signal detected after the detection of the first cam signal pulse, in order to determine an absolute position (θ1) of the variable valve control mechanism (14), wherein, when the actuator (6) is adjusted during a period from the detection of the first cam signal pulse after the start of the start-up until the detection of the first reference position of the crank angle signal, the control unit (7) is configured to obtain a change amount (θ2) of the actuator (6) from an actuator sensor (15) in order to correct the absolute position (θ1) of the variable valve control mechanism (14) based on the obtained change amount (θ2).

Description

TECHNICAL AREA

[0001] The present invention relates to a control device for a variable valve control mechanism and relates in particular to a control device for a variable valve control mechanism capable of achieving a rapid calculation of an absolute position of the variable valve control mechanism during start-up. STATE OF THE ART

[0002] A common control device for a variable valve timing mechanism is configured to calculate an actual valve timing at the time of output of a cam signal based on a crank angle signal output by a crank angle sensor and the cam signal output by a cam sensor, and to calculate a change in valve timing with respect to the actual valve timing at the time of output of the cam signal based on a speed difference between an engine and an intake camshaft, in order to calculate a final actual valve timing using the actual valve timing at the time of output of the cam signal and the valve timing change amount (see, for example, patent document 1).

[0003] Other common control devices are known from the publications DE 101 08 055 C1, US 2009 / 0 265 077 A and DE 100 39 921 A. REFERENCE DOCUMENT LIST PATENT DOCUMENT

[0004] Patent document 1: JP 4 123 127 B2 SUMMARY OF THE INVENTION

[0005] The present invention is defined by the independent claims. TASKS TO BE SOLVED FROM THE INVENTION

[0006] However, with regard to such a common control device for a variable valve timing mechanism, patent document 1 does not disclose a method for achieving a rapid calculation of the actual rotational phase angle of the intake camshaft, that is, the actual position of the variable valve timing mechanism during starting. For this reason, it could be difficult to achieve improved starting performance of a vehicle.

[0007] With regard to the problem, it is therefore an object of the present invention to provide a control device and a control method for a variable valve control mechanism capable of obtaining a rapid calculation of an actual position of the variable valve control mechanism during starting. MEANS OF SOLVING THE TASKS

[0008] To solve the problem, a control device for a variable valve control mechanism according to the present invention comprises: a crank angle sensor that outputs a crank angle signal in response to a rotation of a crankshaft, wherein the crank angle signal is preset, specifying at least two reference positions; a cam sensor that outputs at least two cam signal pulses in response to a rotation of an intake camshaft to open and close an engine valve; an actuator that rotates the intake camshaft relative to the crankshaft, so that the actuator can change a rotational phase angle of the intake camshaft relative to the crankshaft; and a control unit that calculates an actual rotational phase angle of the intake camshaft based on a first cam signal pulse detected after the start of the start-up and a first reference position of the crank signal detected thereafter, in order to calculate an absolute position of the variable valve control mechanism.

[0009] Furthermore, a control method of a variable valve control mechanism according to the present invention comprises: A first step in starting a process; a second step of initiating the process of receiving a crank angle signal output by a crank angle sensor in response to a rotation of a crankshaft, wherein the rotation angle signal is preset to specify at least two reference positions, and of initiating the process of receiving at least two cam signal pulses output by a cam sensor in response to a rotation of an intake camshaft for opening and closing an engine valve; a third step in determining a first cam signal pulse after the start of the starting process; a fourth step of determining an initial reference position of the crank angle signal after the third step; and a fifth step of calculating an actual rotational phase angle of the intake camshaft with respect to the crankshaft, based on the cam signal pulse determined in the third step and the reference position determined in the fourth step, in order to calculate an absolute position of the variable valve control mechanism. ADVANTAGES OF THE INVENTION

[0010] According to the present invention, a rapid calculation of the actual position of the variable valve mechanism during starting can be achieved. This can improve the starting performance of a vehicle. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic view representing a control device for a variable valve control mechanism according to an embodiment of the present invention. Fig. Figure 2 is an explanatory view showing the construction of a crank angle sensor and the construction of a cam sensor in the control device. Fig. Figure 3 is a flowchart showing the output characteristics of the crankshaft angle sensor and the camshaft sensor. Fig. 4 is a cross-sectional view along a line AA of Fig. 2. Fig. Figure 5 is a flowchart describing an example of a calculation method for determining the actual position of the variable valve control mechanism during start-up. Fig. Figure 6 is a flowchart to describe a first embodiment of a control method for the variable valve control mechanism of the present invention. Fig. Figure 7 is a flowchart to describe a second embodiment of a control method for the variable valve control mechanism of the present invention. Fig. Figure 8 is a flowchart to describe a third embodiment of a control method for the variable valve control mechanism of the present invention. Fig. Figure 9 is a flowchart to describe a fourth embodiment of a control method for the variable valve control mechanism of the present invention. FORM OF EXECUTION OF THE INVENTION

[0011] The following describes embodiments of the present invention with reference to the accompanying drawings. Fig. Figure 1 is a schematic view depicting a control device for a variable valve timing mechanism according to an embodiment of the present invention. The control device for the variable valve timing mechanism controls a relative rotational phase angle between a crankshaft 2 and an intake camshaft 3 of an internal combustion engine 1 and includes a crankshaft angle sensor 4, a camshaft sensor 5, an electric motor 6, and an electronic control unit 7.

[0012] The crankshaft angle sensor 4 outputs a pulsed rotation signal in response to the rotation of the crankshaft 2, which is an output shaft of the internal combustion engine 1, and the crankshaft angle sensor 4 includes, in detail, as shown in Fig. Figure 2 shows: a signal plate 9, which is axially supported by the crankshaft 2 and has projections 8 formed around it, which act as detection sections; and a rotation detection device 10, which is attached to the internal combustion engine 1 and detects the projections 8 and thereby outputs a crank angle signal POS.

[0013] The rotation detection device 10 includes various processing circuits, such as a waveform generation circuit and a selection circuit, together with a sensor for detecting the projections 8. The crank angle signal POS output by the rotation detection device 10 is a pulse signal that forms a pulse train and normally has a low level, changing to a high level for a predetermined duration when the projection 8 is detected.

[0014] The projections 8 of the signal plate 9 are formed at equal intervals of 10 degrees in the crank angle. There are two missing sections of projections 8. In each of the missing sections, two consecutive projections 8 are missing. The two missing sections are located on opposite sides of the rotation axis of the crankshaft 2. However, the number of missing projections 8 can be one, or three or more consecutive projections 8 can be missing. The following describes a case in which the number of missing projections 8 is two.

[0015] This structure, as in Fig. As shown in Figure 3, the crank angle signal POS output by the crank angle sensor 4 (rotation detection device 10) changes to the H level 16 times consecutively every 10 degrees of crank angle (unit crank angle), followed by remaining at the L level for 30 degrees, and then the crank angle signal POS changes to the H level again 16 times consecutively.

[0016] This results in an initial crankshaft angle signal being output after the L-level phase of 30 degrees of crankshaft angle (which represents a missing lead or section, hereinafter referred to as the "reference position") at intervals of 180 degrees of crankshaft angle. This 180-degree crankshaft angle corresponds to a stroke phase difference between cylinders in a four-cylinder engine; in other words, it corresponds to a firing interval.

[0017] The cam sensor 5 is configured to detect the rotation angle of the intake camshaft 3 for opening and closing an internal combustion engine valve, and the cam sensor 5 includes, in detail, as described in Fig. Figure 2 shows a signal plate 12, which is axially supported by one end of the intake camshaft 3 and has projections 11 formed around it which act as detection sections; and a rotation detection device 13, which is attached to the internal combustion engine 1 and which detects the projections 11 and thereby outputs a cam signal PHASE.

[0018] The rotation detection device 13 includes various processing circuits, such as a waveform generation circuit, together with a sensor for detecting the projections 11.

[0019] One, three, four, and two projections 11 of the signal plate 12 are positioned at four positions per 90-degree cam angle. The distance between the projections 11 is set to 30 degrees crank angle (15 degrees cam angle) in a section where at least two projections 11 are formed consecutively.

[0020] The cam signal PHASE output by the cam sensor 5 (rotation detection device 13) is a pulse signal that forms a pulse train and normally has a low level and changes to a high level for a predetermined duration when the projection 11 is detected, with the pulse signal changing to be high level once alone, three times in succession, four times in succession and twice in succession for every 90 degrees of cam angle or 180 degrees of crank angle.

[0021] Furthermore, the single cam signal output and the first signal of at least two consecutive cam signals output (hereinafter referred to as "cam signal pulses") are configured to be output at a phase of 180 degrees crank angle.

[0022] At the other end of the intake camshaft 3 is an electric motor 6 (actuator), as shown in Fig. The electric motor 6 forms part of a variable valve timing mechanism (hereinafter referred to as an "electric VTC") 14, which changes the rotational phase of the intake camshaft 3 relative to the crankshaft 2 and thereby changes the valve timing of an intake valve that opens and closes an intake port through which intake air is introduced into a combustion chamber of each cylinder of the internal combustion engine 1. Furthermore, the electric motor 6 is equipped with a motor rotation sensor (actuator sensor) 15, which has a high detection frequency and can determine the motor shaft rotation angle (amount of change) of the electric motor 6, including its direction of rotation, at any time.

[0023] The electric VTC 14 is integrated with a control wheel 17, around which a timing chain 16 is wound to transmit the rotational drive force of the crankshaft 2. The electric VTC 14 is configured to rotate the intake camshaft 3 relative to the control wheel 17 by the electric motor 6, which includes a built-in reduction gear unit to advance or retard the valve timing. The electric VTC 14 is not limited to being provided for the intake valve and can be provided for at least one intake valve and one exhaust valve.

[0024] As in Fig. Figure 4 shows the cross-sectional view along line AA of Fig. The electric VTC 14, as described in section 2, specifically comprises: an annular main wheel body 17a having a stepped inner circumferential surface; and a gear 18 integrally provided on the outer circumference of the main wheel body 17a, the gear 18 receiving a rotational force transmitted from the crankshaft 2 via the timing chain 16 wound around it. Furthermore, the gear 18 is rotatably mounted on the intake camshaft 3 by a ball bearing (not shown), inserted between an annular groove formed on the inner circumference of the main wheel body 17a and the outer circumference of a thick flange (not shown) integrally provided on the front end section of the intake camshaft 3.

[0025] Furthermore, in Fig. As shown in Figure 4, a part of the inner circumferential surface of the wheel main body 17a is formed such that it has a stop-convex section 19 which acts as an arc-shaped engagement section having a predetermined length along the circumferential direction.

[0026] Furthermore, in Fig. As shown in Figure 4, the flange of the intake camshaft 3 is designed to have a stop concave groove 20, which acts as a locking section that receives the stop convex section 19 of the main gear body 17a and is formed along the circumferential direction. The stop concave groove 20 is formed in an arc shape with a predetermined length in the circumferential direction. Both edges 19a, 19b of the stop convex section 19, which move circularly within the area of ​​the predetermined length, contact the opposite edges 20a and 20b respectively in the circumferential direction to define relative rotational positions on the side of the maximum advanced angle and the side of the maximum retarded angle of the intake camshaft 3 with respect to the timing gear 17.

[0027] An electronic control unit (control unit) 7 is provided such that it is electrically connected to the crankshaft angle sensor 4, the camshaft sensor 5, the electric motor 6, and the engine rotation sensor 15. The electronic control unit 7 calculates an actual rotational phase angle (hereinafter referred to as the "actual rotational phase angle") of the intake camshaft 3, based on a first cam signal pulse detected after the start of the crankshaft start and a subsequently detected crankshaft reference position, which is a first reference position of the crankshaft angle signal, in order to calculate an absolute position of the electrical VTC 14 (the actual rotational phase angle of the electrical VTC 14 with respect to the crankshaft 2). The electronic control unit 7 includes a microcomputer, executes the calculation process according to a program pre-stored in a memory unit, and outputs an operating signal to control the drive of a fuel injection device 21 or the electric motor 6.

[0028] The actual rotational phase angle of the intake camshaft 3 corresponds to the absolute position of the electrical VTC 14. Therefore, if the actual rotational phase angle of the intake camshaft 3 is calculated, the absolute position of the electrical VTC 14 can be calculated.

[0029] Specifically, the electronic control unit 7 switches a drive mode of the electric motor 6 from an OFF drive to a drive with a control or from a drive with a control to the drive with the control, at the time when the absolute position of the electrical VTC 14 has been calculated and the electronic control unit 7 controls the drive of the electric motor 6 so that the absolute position of the electrical VTC 14 approaches a target position.

[0030] More precisely, if the electric motor 6 is adjusted in a period from the detection of the first cam signal pulse after the start-up until the detection of the crankshaft reference position of the crankshaft signal, the electronic control unit 7 corrects the absolute position of the electric VTC 14 based on the motor shaft rotation angle (adjusted amount) received from the motor rotation sensor 15.

[0031] Alternatively, if the electric motor 6 is adjusted by a control after starting, the electronic control unit 7 can obtain the motor shaft rotation angle (amount of change) of the electric motor 6 from the motor rotation sensor 15 in order to correct the absolute position of the electric VTC 14, based on the obtained motor shaft rotation angles (amounts of change) on a motor shaft rotation angle (amount of change) from the detection of the first cam signal pulse after starting until the detection of the crankshaft reference position of the crank angle signal.

[0032] If the absolute position of the electric VTC 14 is different from a starting position (default position) when the combustion engine 1 is in a stop state, the electronic control unit 7 can preferentially control the drive of the electric motor 6 such that the amount of change of the electric motor 6 after the drive starts is reduced for a predetermined period.

[0033] The electronic control unit 7 can be configured to control the drive of the electric VTC 14 and to perform intercommunication with an additional electronic control unit 7 for controlling the fuel injection device 21, an ignition device, and similar components of the internal combustion engine 1. Furthermore, in Fig. 1 a reference number 22 is assigned to an air mass sensor for determining an intake air quantity Q of the combustion engine 1. In addition, in Fig. 4 a reference number 23 is assigned to a large-diameter annular plate for carrying a phase-changing mechanism (not shown) which changes a relative rotational phase between the control wheel 17 and the intake camshaft 3, and a reference number 24 is assigned to a screw for securing the control wheel 17 to the large-diameter annular plate 23.

[0034] Next, the operation of the electric VTC 14, which has the configuration described above, will be described.

[0035] Normally, when the internal combustion engine 1 stops, the electric VTC 14 returns to a predetermined standard position (starting position) that is set beforehand and then remains stationary. However, a situation may arise in which the electric VTC 14 has been moved due to an external force during a previous stop state of the internal combustion engine 1, and its position deviates from the standard position at start-up. In such a case, an incorrect absolute position of the electric VTC 14 could be obtained. This could cause the electric motor 6 to be driven to a target position based on an incorrect controlled change amount determined based on the incorrect position of the electric VTC 14, and thus risks arise that the Fig. 4 the depicted stop convex section 19 collides with the opposite edge 20a or 20b of the stop concave groove 20 of the inlet camshaft 3, which leads to damage or risks of engagement and blockage in the cam mechanism for actuating the electric VTC 14.

[0036] According to the present invention, the control unit of the electric VTC 14 is configured to start the operation of the electric motor 6 of the electric VTC 14 after determining an absolute position θ1 of the electric VTC 14 during start-up.

[0037] An example of a method for determining the actual rotational phase angle of the intake camshaft 3 with respect to the crankshaft 2 during starting can be found in Fig. The procedure specified in point 5 includes this. That is, after the start of the engine (time a of Fig. 5) The first reference position of the crank angle signal POS from the crank angle sensor 4 is considered a crankshaft reference position (time b of Fig. 5) determined. Then, after the crankshaft reference position is determined, when the first cam signal pulse of the cam signal PHASE (time c of Fig. 5) is detected, a rotational phase angle is determined from the crankshaft reference position to the first cam signal pulse (between times b and c of Fig. 5) calculated. This allows the actual rotational phase angle of the intake camshaft 3 relative to the crankshaft 2, i.e., the absolute position θ1 of the electric VTC 14, to be determined. Then, by starting the actuation of the electric motor 6 to actuate the electric VTC 14 at the time when the first cam signal pulse is detected (time c in Fig. 5), in which the actual rotational phase angle of the inlet camshaft 3 is determined as described above, the risk of damage to the electrical VTC 14 is avoided.

[0038] Regarding the electrical VTC position of Fig. Figure 5 indicates a relative angle of the electric VTC 14, which is determined using the engine rotation sensor 15 and the crankshaft angle sensor 4. During the period from the start of the starting process until the actual rotational phase angle of the intake camshaft 3 is obtained (absolute position θ1 of the electric VTC 14), the absolute position of the electric VTC 14 is unknown, and therefore neither its absolute position nor its relative angular offset is known. However, once the actual rotational phase angle of the intake camshaft 3, i.e., the absolute position θ1 of the electric VTC 14, is obtained, the absolute position of the electric VTC 14 and the relative angle coincide. Subsequently, the electric VTC 14 is operated based on an actuation controlled by the electric motor 6, and the relative angle increases successively to approach a target position θtr.On the other hand, the absolute position of the electrical VTC 14 also changes, approaching the target position θtr. However, each time a cam signal pulse is detected by the cam sensor 5, a new absolute position of the electrical VTC 14 is calculated and updated, and until the next cam signal pulse is detected, the absolute position remains unchanged at that time. Thus, the absolute position of the electrical VTC 14 changes incrementally to approach the target position θtr, as shown in [reference]. Fig. 5 to see, to approach.

[0039] In Fig. 5. The cam signal PHASE is displayed as a single pulse signal, focusing solely on the cam signal output, and only the first signal of each of the three, four, and two successive pulse signals transitioning to the H level, which are used to determine the rotational phase angle of the intake camshaft 3 relative to the crankshaft 2, is shown for the sake of brevity. The horizontal axis of Fig. 5 represents time. The following will Fig. 6, Fig. 7, Fig. 8 to Fig. 9 described in a similar way.

[0040] In the procedure, as in Fig. As shown in Figure 5, the first actual rotational phase angle of the intake camshaft 3 (the absolute position of the electric VTC 14), calculated after starting, is obtained based on a cam signal pulse acquired after the camshaft reference position has been determined, as described above. This means that the cam signal pulse acquired before the crankshaft reference position is established is not taken into account. This results in an offset in the activation time of the electric VTC 14. Such an offset in the activation time could adversely affect a vehicle's starting performance.

[0041] Therefore, the control device for the electric VTC 14 according to the present invention aims to avoid the risk of damage to the electric VTC 14 and to achieve a rapid start of operation of the electric VTC 14. A control method for the electric VTC 14 according to the present invention will be described in more detail below.

[0042] First, a first embodiment of a control method of the electrical VTC 14 of the present invention is described with reference to Fig. 6 will be described. First embodiment

[0043] First, as a first step, a starter motor (not shown) is switched on to begin starting the internal combustion engine 1 (time a of Fig. 6) This causes the crankshaft 2 to begin rotating, and consequently, the intake camshaft 3 also begins to rotate.

[0044] Next, as a second step, the electronic control unit 7 begins to receive the crank angle signal POS output by the crank angle sensor 4 in response to the rotation of the crankshaft 2.

[0045] At the same time, the electronic control unit 7 begins to receive the cam signal PHASE issued by the cam sensor 5 in response to the rotation of the intake camshaft 3.

[0046] Then, as a third step, the electronic control unit 7 receives data after the start of the ignition (time a of Fig. 6) a first cam signal pulse of the cam signal PHASE (time b of Fig. 6) Then, when the first cam signal pulse is received, the electronic control unit 7 begins to count up in response, with the counting being performed every 10 degrees of crank angle.

[0047] Additionally, as a fourth step, after detecting the first cam signal pulse, the electronic control unit 7 determines that a first reference position of the crank angle signal POS output by the crank angle sensor 4 is a crankshaft reference position (time c of Fig. 6) Then, based on the count value taken after receiving the first cam signal pulse until the crankshaft reference position is detected, the electronic control unit 7 calculates a rotational phase angle between the first cam signal pulse and the crankshaft reference position (between times b and c of Fig. 6) The result is temporarily stored in a memory unit. In this case, if the count value is denoted by n (n being a positive integer), the rotation phase angle can be n × 10 degrees.

[0048] As a fifth step, the electronic control unit 7 calculates an actual rotational phase angle of the intake camshaft 3 with respect to the crankshaft 2 (between times a and b of Fig. 6), based on the first cam signal pulse and the crankshaft reference position. More precisely, since the crank angle signal reference positions are output in 180-degree crank angle intervals, the crank angle between the previously determined crankshaft reference position and a previous reference position is 180 degrees (fixed value). Thus, the crank angle between the previous reference position of the above crank angle reference position and the first cam signal pulse can be "180 degrees - n×10 degrees". That is, this crank angle is determined as the actual rotational phase angle of the intake camshaft 3 with respect to the crankshaft 2, i.e., the absolute position θ1 of the electrical VTC 14 at the time of detection of the first cam signal pulse after starting.

[0049] Although Fig. 6 indicates a case where the start time and the reference position of the crank angle signal POS coincide, but these do not always have to coincide.

[0050] When the absolute position of the electric VTC 14 is calculated as described above, the electronic control unit 7 begins to actuate the electric motor 6 to actuate the electric VTC 14 at the calculation time (time c of Fig. 6). Then, similar to Fig. 5, the electric motor 6 is actuated by the control system to ensure that the absolute position of the electric VTC 14 reaches the actual position θtr. This changes the absolute position of the electric VTC 14 so that it becomes the target position θtr.

[0051] Once the electric VTC 14 begins operation, as described in Fig. 6 is displayed, an absolute position of the electrical VTC 14 is calculated and updated every time a cam signal pulse of the cam signal PHASE is detected.

[0052] Fig. Figure 7 is a flowchart describing a second embodiment of a control method for the electrical VTC 14 of the present invention. The second embodiment is described below with reference to Fig. 7. The differences from the first embodiment are described below. Second embodiment

[0053] If the electric motor 6, for example, is subjected to an external force after the start of the starting process and during a period from the detection of a first cam signal until a crankshaft reference position is established (between times b and c of Fig. 7) If the position of the electric VTC 14 has been shifted, it may deviate from the absolute position θ1 of the electric VTC 14, which is determined based on the first cam signal and the crankshaft reference position. If the electric VTC 14 is operated in such a state, the electronic control unit 7 could determine that a true position of the electric VTC 14 is the defined absolute position θ1 and could set a control amount for the electric motor 6 based on the position and the target position θtr in order to actuate the electric motor 6. This could pose a risk of damage to the electric motor 6 in such a case.

[0054] Therefore, in the control method of the electric VTC 14 according to the second embodiment of the present invention, in a case in which the electric motor 6 is operated for a period from the determination of the first actual rotational phase angle (absolute position θ1 of the electric VTC 14) of the inlet camshaft 3 after starting until the determination of the crankshaft reference position (i.e., the period extends from time b to time c of Fig. 7), a motor shaft rotation angle (amount of change) of the electric motor 6 is determined by the motor rotation sensor 15 and at the time of determining the crankshaft reference position (time c of Fig. 7) The absolute position of the electric VTC 14 is corrected by adding the motor shaft rotation angle (change amount) θ2 to the determined absolute position θ1 of the electric VTC 14. In this way, the true position (θ1 plus θ2) of the electric VTC 14 is determined. The drive control of the electric VTC 14 is then the same as in the first embodiment.

[0055] Fig. Figure 8 is a flowchart describing a third embodiment of a control method for the electrical VTC 14 of the present invention. The third embodiment is described below with reference to Fig. 8 will be described. Third embodiment

[0056] To reduce the adverse effects of the positional deviation of the electric VTC 14 caused by an external force, the drive of the electric motor 6 can be started simultaneously with a control by a predetermined amount at the beginning of the starting process. In this case, an absolute position of the electric VTC 14 is established at the time when a first cam signal pulse occurs after the start of the starting process (time a of Fig. 8) is detected (time b of Fig. 8) calculated as in the first embodiment and the absolute position is θ1.

[0057] As the electric motor 6 continues to rotate, the electric VTC 14 moves during a period from the detection of the first cam signal pulse until the determination of the crankshaft reference position (between times b and c of Fig. 8) further, and thus the true position of the electric VTC 14 differs from the absolute position θ1 of the electric VTC 14 calculated on the basis of the first cam signal pulse and the crankshaft reference position. Thus, in the third embodiment of the present invention, the motor shaft rotation angle (change amount) θ2 of the electric motor 6, which occurs in a period from the detection of the first cam signal pulse until the determination of the crankshaft reference position (between times b and c of Fig. 8) has been shifted, as measured by the engine rotation sensor 15, and at the time of determining the crankshaft reference position, the absolute position of the electric VTC 14 is corrected by adding the engine shaft rotation angle (change amount) θ2 to the calculated absolute position θ1 of the electric VTC 14. The subsequent drive control of the electric VTC 14 is the same as in the first embodiment. In this way, the response of the electric VTC 14 can be further improved.

[0058] Fig. Figure 9 is a flowchart describing a fourth embodiment of a control method for the electrical VTC 14 of the present invention. The fourth embodiment is described below with reference to Fig. 9 will be described. Fourth embodiment

[0059] If the absolute position of the electric VTC 14 differs from a standard position in which the electric VTC 14 should normally be positioned when the internal combustion engine 1 is stopped, there could be a risk of damage to the electric VTC 14, as mentioned above. Therefore, in the control method of the electric VTC according to the fourth embodiment of the present invention, a controlled change in the electric motor 6 is applied at the beginning of the actuation of the electric VTC 14 for a predetermined period, as described in Fig. Figure 9 shows a reduction. Therefore, the movement speed of the electric VTC 14 can be reduced, and it becomes possible to minimize the risks of collisions. Fig.4 shown stop convex section 19 with the opposite edges of the stop concave groove 20 of the inlet camshaft 3 to avoid an overshoot of the electric VTC 14 which leads to damage or the risks of engagement and blocking which occurs in the cam mechanism for actuating the electric VTC 14.

[0060] The embodiments described above are not implemented if the electric VTC 14 has learned the standard position. Furthermore, the embodiments are not implemented if the target position of the rotational phase angle of the intake camshaft 3 is not within a control angle range between a control limit on the leading side and a control limit on the lagging side of the electric VTC 14. Reference symbol list 1 Internal combustion engine (engine) 2 Crankshaft 3 Intake camshaft 4 Crank angle sensor 5 cam sensor 6 Electric motor (actuator) 7 electronic control unit (control unit) 14 electric VTC (variable valve control mechanism) 15 Motor rotation sensor (actuator sensor)

Claims

[1] A control device for a variable valve control mechanism (14), comprising: a crank angle sensor (4) which outputs a crank angle signal in response to a rotation of a crankshaft (2), wherein the crank angle signal is preset to specify at least two reference positions; a cam sensor (5) which outputs at least two cam signal pulses in response to a rotation of an intake camshaft (3) to open and close an engine valve; an actuator (6) that rotates the intake camshaft (3) relative to the crankshaft (2) so that the actuator (6) can change a rotational phase angle of the intake camshaft (3) relative to the crankshaft (2); and a control unit (7) configured to calculate an actual rotational phase angle of the intake camshaft at the time of detection of the first camshaft signal pulse, based on a first cam signal pulse detected after the start of the starting process and a first reference position of the crankshaft signal detected after the detection of the first cam signal pulse, in order to determine an absolute position (θ1) of the variable valve control mechanism (14), wherein, when the actuator (6) is adjusted during a period from the detection of the first cam signal pulse after the start of the start-up until the detection of the first reference position of the crank angle signal, the control unit (7) is configured to obtain a change amount (θ2) of the actuator (6) from an actuator sensor (15) in order to correct the absolute position (θ1) of the variable valve control mechanism (14) based on the obtained change amount (θ2). [2] A control device for the variable valve control mechanism (14), comprising a crank angle sensor (4) which outputs a crank angle signal in response to a rotation of a crankshaft (2), wherein the crank angle signal is preset to specify at least two reference positions; a cam sensor (5) which outputs at least two cam signal pulses in response to a rotation of an intake camshaft (3) to open and close an engine valve; an actuator (6) that rotates the intake camshaft (3) relative to the crankshaft (2) so that the actuator (6) can change a rotational phase angle of the intake camshaft (3) relative to the crankshaft (2); and a control unit (7) configured to calculate an actual rotational phase angle of the intake camshaft at the time of detection of the first camshaft signal pulse, based on a first cam signal pulse detected after the start of the starting process and a first reference position of the crankshaft signal detected after the detection of the first cam signal pulse, in order to determine an absolute position (θ1) of the variable valve control mechanism (14), wherein the control unit (7) is configured, when the actuator (6) is adjusted with a control after the start of the start-up, to obtain a change amount of the actuator by an actuator sensor (15) in order to correct the absolute position (θ1) of the variable valve control mechanism based on a change amount (θ2) from the detection of the first cam signal pulse after the start of the start-up until the detection of the first reference position of the crank angle signal, from the obtained change amounts (θ2). [3] A control device for the variable valve control mechanism (14), comprising a crank angle sensor (4) which outputs a crank angle signal in response to a rotation of a crankshaft (2), wherein the crank angle signal is preset to specify at least two reference positions; a cam sensor (5) which outputs at least two cam signal pulses in response to a rotation of an intake camshaft (3) to open and close an engine valve; an actuator (6) that rotates the intake camshaft (3) relative to the crankshaft (2) so that the actuator (6) can change a rotational phase angle of the intake camshaft (3) relative to the crankshaft (2); and a control unit (7) configured to calculate an actual rotational phase angle of the intake camshaft at the time of detection of the first camshaft signal pulse, based on a first cam signal pulse detected after the start of the starting process and a first reference position of the crankshaft signal detected after the detection of the first cam signal pulse, in order to determine an absolute position (θ1) of the variable valve control mechanism (14), wherein the control unit (7) is configured to switch an actuation mode of the actuator (6) from an OFF actuation to an actuation with control or from an actuation with control to the actuation with control, at a time (c) when the absolute position (θ1) of the variable valve mechanism (14) has been calculated, and wherein, when the absolute position (θ2) of the variable valve control mechanism is different from a home position when an engine is stopped, the control unit is configured to actuate the actuator (6) while decreasing a control change amount of the actuator.

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