JP2011001859A - Diagnostic device for valve timing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To overcome problems that conventionally, the reference position offset diagnosis of a variable valve timing mechanism is executed when prescribed time has passed after being in an idle operating state not requiring engine torque, the idle operating state hardly exists and sufficient learning time or diagnosis time cannot be secured in a vehicle which stops idling or a hybrid vehicle which is driven by an internal combustion engine and an electric motor, and there is a method for prohibiting shifting to idle-stop and performing diagnosis, but concerns about influence on fuel economy may be raised when the time for stopping the engine is delayed for the prescribed time.SOLUTION: The reference position offset diagnosis is executed in a lock mechanism restricting state in starting of the engine. In addition to the ordinary reference position offset diagnosis executed after a valve timing control start condition is established, the diagnosis is also executed before the valve timing control start condition is established, and thereby, a diagnosis frequency can be increased.

Description

  The present invention relates to a diagnosis of a valve timing device, and more specifically, a valve that changes the opening / closing timing of an intake valve or an exhaust valve that is opened / closed according to the rotation of the camshaft by changing the phase of the camshaft with respect to the crankshaft of the internal combustion engine. The present invention relates to a technique for diagnosing a reference position abnormality (reference position offset) of a timing device.

  As a mechanism for adjusting the opening / closing timing of an intake / exhaust cam of an internal combustion engine (hereinafter referred to as a variable valve timing mechanism), a mechanism using hydraulic pressure is known. In this device, as a variable valve timing mechanism, a vane type constituted by a vane that transmits a rotational force to a camshaft that opens and closes a valve, and a housing that stores the vane and transmits a rotational force from a crankshaft of an internal combustion engine. Is adopted. The housing containing the vanes has an advance chamber and a retard chamber, and the housing and the vane rotate relative to each other by supplying oil to the advance chamber or retard chamber using an oil control valve for controlling the hydraulic pressure. Thus, the valve timing is variably controlled by changing the rotational phase of the camshaft relative to the crankshaft. Since the variable valve timing mechanism is controlled by hydraulic pressure in this way, a certain level of hydraulic pressure is required. For this reason, it is difficult to accurately control the valve timing because the hydraulic pressure is low when starting or when the engine is stopped.

  Incidentally, the variable valve timing mechanism controls the actual cam phase by feedback control with respect to the target cam phase. The camshaft and crankshaft are driven via a driving force transmission mechanism such as a belt, chain, or gear. If the driving force transmission mechanism is elongated or worn due to deterioration over time, the camshaft and crankshaft rotate. Out of phase. Since the accuracy of feedback control deteriorates as the amount of deviation increases, reference position learning is periodically performed. (Patent Document 1) Further, when the amount of deviation greatly exceeds the learning amount, correction by learning becomes ineffective, and therefore, a reference position offset diagnosis (Patent Document 2) is generally performed to determine whether or not the amount of deviation exceeds a predetermined value. Have gone.

  In the learning and diagnosis as described above, the diagnosis is performed in a state where the actual cam phase is sufficiently stable with respect to the target cam phase in order to avoid erroneous diagnosis due to a transient shift amount. Generally, it is executed after a predetermined time has elapsed since the engine has entered an idle operation state that does not require engine torque.

  However, in a vehicle that is idle-stopped or a hybrid vehicle that is driven by an internal combustion engine and an electric motor, there is almost no idle operation state, so sufficient learning time and diagnosis time cannot be secured. In particular, in order to prevent misdiagnosis, the diagnosis requires a long time for diagnosis, and is almost impossible to execute. Therefore, as one of the countermeasures, there is a method of executing a diagnosis while prohibiting transition to idle stop.

JP 2007-270754 A Japanese Patent Laid-Open No. 2006-291738

  However, the conventional control technique described above delays the time for which the engine should be stopped by a predetermined time, so there is a concern about the influence on fuel consumption. In particular, idle stop vehicles and hybrid vehicles that emphasize fuel efficiency are required to eliminate wasted idle operations as much as possible.

  Therefore, the present invention executes the reference position offset diagnosis in the lock mechanism restriction state at the time of engine start.

  According to the first aspect, in addition to the normal reference position offset diagnosis performed after the valve timing control start condition is satisfied, the diagnosis can be executed before the valve timing control start condition is satisfied, so that the diagnosis frequency can be increased. After the valve timing control start condition is satisfied, it is necessary to wait for diagnosis until the actual cam phase is stabilized with respect to the target cam phase, and it takes time to start diagnosis. Normally, the diagnosis is executed by returning the cam position to the reference position in an idle state where engine torque is not required. However, in a vehicle having almost no idle state, the vehicle is idled before the diagnosis is completed. In the lock mechanism restriction state before the valve timing control start condition is satisfied, the relative phase of the crankshaft and camshaft is always fixed regardless of the working fluid pressure state, so there is no need to ensure time for stabilization and reliable In addition, a mechanical deviation between the crankshaft and the camshaft can be detected. Since the lock mechanism mechanically performs restriction / release according to the fluid pressure, the operating state can be detected with high accuracy by measuring the fluid pressure of the working fluid.

  Since the lock mechanism state is estimated and calculated by the fluid pressure as in claim 1, an estimation error may occur. If the diagnosis is carried out assuming that the lock mechanism is released even though the lock mechanism is released, the actual cam phase may be shaken by the cam reaction force when the fluid pressure is not sufficiently high. In some cases, misdiagnosis may occur. In order to avoid such a misdiagnosis, as described in claim 2, the diagnosis may be performed by measuring whether or not the predetermined range is exceeded a predetermined number of times.

  In a completely restricted state, the crankshaft and camshaft are mechanically fixed, so the threshold value of the actual cam phase diagnostic counter can be set small. On the other hand, if it is in the released state, the diagnosis counter threshold is set to be larger because the diagnosis can be prevented by continuing the diagnosis until the fluid pressure becomes stable. By making the diagnostic counter threshold variable as described in claim 3, it is possible to end the diagnosis reliably and in a short time according to the state of the lock mechanism.

  The camshaft position is calculated based on the angle control based on the crankshaft signal and the time control based on the crankshaft signal and the camshaft signal. Decreases. For this reason, there is a risk of erroneous diagnosis due to a decrease in the accuracy of actual cam phase detection. Accordingly, it is possible to prevent erroneous diagnosis by changing the threshold value of the reference position offset and the threshold value of the diagnostic counter as described in claim 4. For example, when the rotational speed fluctuates greatly, it is possible to prevent misdiagnosis by loosening the threshold value of the reference position offset, and to ensure a long diagnosis time by increasing the threshold value of the diagnostic counter, thereby executing more accurate diagnosis. be able to.

  In a vehicle that is idle-stopped, if the first reference position offset diagnosis is not completed, the possibility that the second reference position offset diagnosis can be executed is extremely low. Therefore, when the first reference position offset diagnosis is not completed as described in claim 5, by prohibiting idle stop, an area that can be diagnosed reliably can be created and the first reference position offset diagnosis is completed. In this case, since normal idle stop control is executed, it is possible to minimize deterioration in fuel consumption.

  According to the present invention, it is possible to increase the frequency of the reference position offset diagnosis as compared with the prior art without extra idle operation.

The figure which shows the structural example of the engine to which the valve timing apparatus by this invention is applied. The perspective view which shows roughly the structure which drives a cam shaft. The internal block diagram of an engine control apparatus. The figure explaining the structure of the variable valve timing mechanism of a valve timing apparatus, and operation | movement of a locking mechanism. The flowchart of the reference position offset diagnosis at the time of a lock mechanism restriction state. The flowchart of the reference position offset diagnosis of the vehicle which carries out an idle stop. Operation time chart of reference position offset diagnosis. Operation time chart for setting allowable offset value due to engine speed fluctuation.

FIG. 1 is a diagram illustrating a configuration example of an engine 1 to which a valve timing device 51 is applied. The engine body 2 of the engine 1 is a DOHC type multi-cylinder four-cycle engine in which a cylinder head 3 is provided with a cam shaft 31 for an intake valve 32 and a cam shaft 33 for an exhaust valve 34.
However, only one cylinder is shown in FIG. 1 for simplification.

  A cam pulley 37 having a variable valve timing mechanism is provided at one end of the camshaft 31 for the intake valve 32, and the phase of the camshaft 33 with respect to the crankshaft 6 does not change at one end of the camshaft 33 for the exhaust valve 34. A cam pulley 38 is provided. The cam pulleys 37 and 38 are connected to the crankshaft 6 by a timing belt 39 spanned between the crankshaft 6 and the crank pulley 6a, and are rotated by the rotational force transmitted from the crankshaft 6.

  An oil pump 7 is connected to the crankshaft 6 and rotates in synchronization with the crankshaft 6 to discharge hydraulic oil as a working fluid and generate hydraulic pressure as a fluid pressure to lubricate the engine body 2. Oil is supplied to hydraulic drive actuators such as the oil control valve 24 and the like.

  An air cleaner 11, an air flow sensor 43, a throttle body 13, a collector 14, and an intake pipe 15 are attached to the intake side of the engine body 2. The air flow sensor 43 detects the intake air amount of air taken from the air cleaner 11. The throttle body 13 houses a throttle valve 13a that controls the amount of intake air supplied to the engine body 2, and a throttle sensor 42 that detects the opening of the throttle valve 13a is attached. An intake pipe internal pressure sensor 44 that detects the internal pressure of the intake pipe 15 is attached to the intake pipe 15.

  The air taken in from the air cleaner 11 passes through the air flow sensor 43 and the throttle body 13, is introduced into the collector 14, is distributed to each cylinder 4 a of the cylinder block 4 by the intake pipe 15, and then the piston 5, the cylinder 4 a, etc. To the combustion chamber 2a formed.

  The engine body 2 is provided with an injector 21 and a spark plug 22 for each cylinder. The injector 21 injects fuel such as gasoline supplied from a fuel tank (not shown) through a fuel pipe (not shown) at a predetermined timing. The fuel injected from the injector 21 is mixed with air in the intake pipe 15 of the engine body 2 and supplied to the combustion chamber 2a as an air-fuel mixture. The fire plug 22 ignites in the combustion chamber 2 a by the ignition signal that has been increased in voltage by the ignition coil 23.

  A water temperature sensor 41, a crank angle sensor 45, and a cam angle sensor 46 are attached to the engine body 2. The water temperature sensor 41 measures the water temperature of the cooling water that cools the engine body 2 and outputs the signal to the engine control device 8. The crank angle sensor 45 detects the rotation angle of the rotating body 36 attached to the crankshaft 6 of the engine body, and outputs an angle signal indicating the rotation position of the crankshaft 6 to the engine control device 8. The cam angle sensor 46 detects the rotation angle of the rotating body 35 that is rotatably attached to the cam shaft 31 that drives the intake valve 32, and outputs an angle signal representing the rotation position of the cam shaft 31 to the engine control device. 8 is output.

  An exhaust pipe 16 is attached to the exhaust side of the engine body 2. The exhaust pipe 16 is provided with an air-fuel ratio sensor 17 that detects the oxygen concentration in the exhaust gas and outputs a detection signal to the engine control device 8, an exhaust gas purification catalyst 18, and the like.

  FIG. 3 is an internal configuration diagram of the engine control device 8. The main part of the engine control device 8 includes an MPU 8a, an EP-ROM 8b, a RAM 8c, and an I / O LSI 8d including an A / D converter.

  Various sensors including a crank angle sensor 45, a cam angle sensor 46, a water temperature sensor 41, a throttle sensor 42, an air flow sensor 43, and an intake pipe internal pressure sensor 44 are connected to the input side of the I / O LSI 8d. The control device 8 captures input signals from these various sensors.

  The engine control device 8 executes predetermined calculation processing based on these input signals, outputs various control signals calculated as the calculation results from the I / O LSI 8d, and a fuel pump (not shown) as an actuator. ), A predetermined control signal is supplied to the throttle valve 13a, the injector 21, the ignition coil 23, the oil control valve 24, and the like to execute fuel injection amount control, ignition timing control, cam phase control, and the like.

  The valve timing device 51 includes a cam phase control means that is executed by the engine control device 8 described above, and a variable valve timing mechanism 52 and a lock mechanism 61 described later.

  FIG. 2 is a perspective view schematically showing a structure for driving the cam shafts 31 and 33, and FIG. 4 is a diagram for explaining the mechanism and operation of the valve timing device 51.

  As shown in FIG. 4, the variable valve timing mechanism 52 includes a substantially annular housing 53 (first rotating body) that is a first rotating body and a vane that is a second rotating body housed therein. And a body 54 (second rotating body). The housing 53 is connected to the cam pulley 37 so as to be integrally rotatable, and the vane body 54 is connected to the cam shaft 31 for the intake valve 32 so as to be integrally rotatable.

  The housing 53 has a plurality of recesses 53a that are recessed from the inner peripheral surface of the housing 53 toward the radially outer side and are formed at predetermined intervals in the circumferential direction. The vane body 54 has a plurality of vanes 54a that protrude outward in the radial direction and are arranged so as to be reciprocally movable in the rotation direction in the respective recesses 53a.

  The recess 53a of the housing 53 is partitioned by the vane 54a of the vane body 54 into an advance side that is one side in the rotational direction and a retard side that is the other side in the rotational direction. The recessed portion 53a and the vane 54a form an advance chamber F that is a first pressure chamber and a retard chamber B that is a second pressure chamber. In the present embodiment, the advance direction is set as the pulley rotation direction shown clockwise in FIG. The vane body 54 can relatively rotate in a range from a phase in which the vane 54a contacts the advance side wall of the recess 53a to a phase in contact with the retard side wall. The change in the phase between the housing 53 and the vane body 54 coincides with the change in the phase of the camshaft 31 with respect to the crankshaft 6. Then, the most retarded angle position (rotation limiting phase) in which the vane body 54 is relatively rotated relative to the housing 53 relative to the retard angle side is the position in the engine stop state, that is, the oil control valve 24 is The initial position when the operation is not controlled by the control device 8 is set. The actual cam phase, which is the actual phase of the camshaft 31 with respect to the crankshaft 6, is an angle signal indicating the rotational position of the crankshaft 6 output from the crank angle sensor 45 and the camshaft 31 output from the cam angle sensor 46. It is calculated by the engine control device 8 using an angle signal representing the rotational position.

  If the hydraulic oil supplied from the oil pump 7 is led to the retard chamber B through the oil control valve 24 and the hydraulic oil in the advance chamber F is discharged to the oil pan, the vane body 54 is delayed with respect to the housing 53. The cam phase can be changed to the retard angle side by rotating relative to the angle side. On the other hand, if the hydraulic oil is guided to the advance chamber F and the hydraulic oil in the retard chamber B is discharged to the oil pan, the vane body 54 can be rotated relative to the housing 53 toward the advance side, and the cam phase Can be changed to the advance side. The oil control valve 24 has a solenoid (not shown). By controlling the current value, the solenoid can be driven to guide the hydraulic oil to the retard chamber or the advance chamber.

  The engine control device 8 feedback-controls the current value of the solenoid so that the target cam phase calculated based on the operation state detected from each sensor is equal to the actual cam phase. Here, as a method for controlling the current value of the solenoid, a method is used in which the ratio (duty ratio) of the time during which the voltage is applied to the solenoid and the time during which the voltage is not applied is changed within a unit time.

  Next, the lock mechanism 61 of the valve timing device 51 and its operating principle will be described.

  The variable valve timing mechanism 52 described above is provided with a lock mechanism 61 that restricts relative rotation of the vane body 54 when the hydraulic oil pressure decreases. The lock mechanism 61 restricts relative rotation of the vane body 54 with respect to the housing 53 at the most retarded angle position, and is based on the hydraulic pressure of the hydraulic oil supplied to at least one of the advance chamber F and the retard chamber B. It has the structure which cancels | releases the restriction | limiting of rotation.

  One of the vanes 54a is formed with a stepped accommodation hole 63 extending in the same direction as the rotation axis direction of the vane body 54, and a lock pin 62 is disposed in the accommodation hole 63 so as to be reciprocally movable. ing. As shown in FIGS. 4A to 4D, the lock pin 62 has the outer peripheral surface of the lock pin 62 slidably in contact with the inner peripheral surface of the accommodation hole 63, and the tip end portion 62a of the lock pin 62 protrudes from the vane 54a. It reciprocates between a protruding position (see FIG. 4A) and a retracted position for retracting in the vane 54a.

  The lock pin 62 is urged toward the protruding side by a lock pin spring 64. At the base end of the lock pin 62, a diameter-expanded portion 62a having a diameter increased through a step is formed. Between the diameter-expanded portion 62a and the stepped portion of the accommodation hole 63, an unlocking pressure chamber R1 is formed. Is formed. The unlocking pressure chamber R1 communicates with the retarding chamber B via a retarding hydraulic fluid passage r1 formed in the vane 54a, so that the pressure in the retarding chamber B is transmitted. .

  The housing 53 has a recessed recess 66 into which the tip of the lock pin 62 can be inserted when the vane body 54 is positioned at the most retarded angle position, and the lock pin 62 is moved to the projecting position. The vane body 54 is mechanically fastened to the housing 53 by inserting the distal end portion 62a of the 62 into the lock hole 66, and the relative rotation of the vane body 54 is limited.

  A space formed between the lock hole 66 and the tip end portion 62 a of the lock pin 62 is an unlocking pressure chamber R <b> 2, and the advance side operation formed on the sliding surface between the vane 54 and the housing 53. It communicates with the advance chamber F via the oil passage r2, and the pressure in the advance chamber F is transmitted.

  The pressure of the hydraulic oil in the unlocking pressure chambers R1 and R2 acts in a direction in which the lock pin 62 is removed from the lock hole 66. For example, when the pressure in the retarding chamber B is sufficiently increased and the hydraulic pressure in the retarding chamber B is transmitted to the unlocking pressure chamber R1 through the retarding-side hydraulic oil passage r1, the pressure in the retarding chamber B is as shown in FIG. As shown, the tip 62a of the lock pin 62 can be completely removed from the lock hole 66, the lock pin 62 can be moved from the protruding position to the retracted position, and the restriction by the lock mechanism 61 can be released.

  When the pressure in the advance chamber F is sufficiently increased, as shown in FIG. 4C, the hydraulic pressure in the advance chamber F is transmitted to the unlocking pressure chamber R2 through the advance side hydraulic oil passage r2. The lock pin 62 is held in the retracted position, and the vane body 54 can be smoothly relatively rotated toward the advance side.

  Further, when hydraulic oil is supplied to the retarding chamber B so as to relatively rotate the vane body 54 toward the retarding side and the pressure in the retarding chamber B is sufficiently increased, as shown in FIG. The hydraulic pressure in the retarded chamber B is transmitted to the unlocking pressure chamber R1 through the corner side hydraulic oil passage r1, and the lock pin 62 is held in the retracted position, and the vane body 54 is smoothly rotated relatively to the retarded side. Can do.

  When the hydraulic oil pressure is not applied to the unlocking pressure chambers R1 and R2, for example, when the engine is stopped, as shown in FIG. The distal end portion 62 a is inserted into the lock hole 66, and the restriction state restricts the relative rotation of the vane body 54 with respect to the housing 53.

  When the hydraulic pressure in the retard chamber B rises as the engine starts and the hydraulic pressure in the unlocking pressure chamber R1 exceeds the urging force of the lock pin spring 64, the lock pin 62 is moved from the protruding position to the retracted side, and the lock The tip 62a of the pin 62 is removed from the lock hole 66, and the restriction state of the lock mechanism 61 is released. When the working oil is supplied to the advance chamber F from the released state as shown in FIG. 4C, the vane body 54 can be relatively rotated to the advance side as described above.

  Next, examples of the present invention will be described.

  FIG. 5 shows a flowchart for performing a reference position offset diagnosis for diagnosing that the reference position of the variable valve timing mechanism 52 is offset when the lock mechanism 61 is in the restricted state.

  After the program starts, it is determined in step S102 whether or not a normal valve timing control (hereinafter referred to as VTC) start condition is satisfied. Since the VTC can be driven after the hydraulic pressure is sufficiently developed after warming up, the condition is not satisfied in starting after cooling. If the VTC start condition is satisfied in S102, the VTC is driven in step S122 immediately after warming up, and normal valve timing control is performed. On the other hand, if the condition is not satisfied in step S102, the process proceeds to step S104 to determine the state of the lock mechanism. If the lock mechanism is not in the restricted state, the first reference position offset diagnosis is not performed and the process returns to step S102, and the diagnosis is not performed and the VTC drive is waited until the normal VTC start condition is satisfied. When the lock mechanism 61 is in the restricted state, the process proceeds to step S106 and the first reference position offset diagnosis is started. Thereafter, in step S108, it is determined whether or not the diagnostic counter exceeds a predetermined threshold value. If not, the process returns to step S102, and steps S102 to S108 are repeated until the diagnostic counter exceeds the predetermined threshold value. When the normal VTC start condition is satisfied in a state where the diagnostic counter does not exceed the predetermined threshold, the first reference position offset diagnosis is terminated and the normal VTC drive control in step S122 is executed. If the diagnosis counter exceeds a predetermined threshold value in step S108, the process proceeds to step S110 to determine whether or not the first reference position offset diagnosis is abnormal. If it is determined that the first reference position offset diagnosis is not abnormal, the process returns to step S102 and waits for VTC drive until the normal VTC drive condition is satisfied. If it is determined in step S110 that the diagnosis is abnormal, the process proceeds to step S112 to perform fail-safe control. Normally, fail-safe control prohibits VTC drive and fixes the reference position. Here, the position is fixed at the most retarded position. On the other hand, when the normal VTC start condition is satisfied and the normal VTC drive is executed in step S122, the second reference position offset diagnosis in step S124 is executed at the timing when the VTC returns to the reference position. In general, the VTC returns to the reference position when engine torque is unnecessary, and there are many idle states. The second reference position offset diagnosis is a diagnosis after the hydraulic pressure is generated and the VTC drive is performed. In order to execute the diagnosis, a predetermined time delay is required until the actual cam phase returns to the reference position, and the diagnosis starts. Become slow. After the second reference position offset diagnosis is started, the process proceeds to step S126, and it is determined whether or not the second reference position offset diagnosis is abnormal. If not abnormal, the process returns to step S122 to perform normal VTC drive. If it is determined that there is an abnormality, the process proceeds to step S112, the fail safe control is executed, and the process ends.

  In the flowchart of FIG. 5, when the first reference position offset diagnosis is not completed, the diagnosis can be executed by the second reference position offset diagnosis after the VTC drive, but the idle state is very small. There is a possibility that the second reference position offset diagnosis cannot be executed in an idle stop vehicle or a hybrid vehicle. FIG. 6 shows a diagnosis flowchart suitable for a vehicle with very few idle states.

  The flow when the normal VTC start condition is not satisfied (step S202: NO) is the same as that in FIG.

  If the normal VTC drive start condition is satisfied in step S202, the process proceeds to step S222, and it is determined whether or not the first reference position offset diagnosis has been completed. If the first reference position offset diagnosis has been completed, the process proceeds to step S234 and normal VTC drive is performed. On the other hand, if the first reference position offset diagnosis has not been completed, the process proceeds to step S224 to set the idle stop prohibited state. Thereafter, the process proceeds to step S226, and normal VTC drive is executed. When the engine torque is no longer necessary, the idle stop is normally performed. However, since the idle stop is prohibited in step S224, the idle state is entered. At this time, since the VTC returns to the reference position, the second reference position offset diagnosis can be started in step S228. After starting the second reference position offset diagnosis, the process proceeds to step S230 to determine whether or not the diagnosis is abnormal. If the diagnosis is abnormal, the process proceeds to step S212 and shifts to fail-safe control. On the other hand, if it is determined in S230 that the diagnosis is not abnormal, the process proceeds to step S232, and the idle stop prohibition is canceled. As a result, when the engine torque is not required as it is, the engine shifts to the idle stop. On the other hand, when the torque is required and the VTC is driven, the normal VTC drive is performed in step S234. In the above embodiment, even in a vehicle having no idle state or a small number of vehicles, it is possible to minimize deterioration in fuel consumption while ensuring the diagnosis frequency.

  FIG. 7 shows a time chart of the reference position offset diagnosis.

  The solid line in the actual cam position chart indicates the movement of the actual cam position when the lock mechanism is released. The broken line represents the movement of the actual cam position when the lock mechanism is activated and the actual cam phase, which is the cam shaft phase detected by the cam angle sensor, is in the restricted state. When a certain amount of oil pressure is generated and the lock mechanism is released, the actual cam fluctuates according to the cam reaction force until the oil pressure is stabilized. For example, when the pressure to the hydraulic piping is not uniform, the hydraulic pressure is generated for a moment as the lock mechanism is released, but the pressure is moved to another hydraulic piping by the cam reaction force. Similarly, when the engine is stopped in a state where the lock mechanism is not well regulated and the engine is started in that state, the actual cam varies according to the cam reaction force. In such a case, if the offset amount is originally greater than or equal to the allowable value due to chain elongation or the like, the diagnosis is NG and no erroneous diagnosis is made, but if the offset amount is less than or equal to the allowable value, there is a risk of misdiagnosis (in the figure). Hunting area). On the other hand, when the lock mechanism is in the restricted state, the VTC does not fluctuate and shows a relatively stable actual cam position. As described above, since the movement of the actual cam position is changed depending on the lock mechanism state, it is possible to achieve both early diagnosis completion and prevention of erroneous diagnosis by individually setting the threshold values of the diagnosis counter. Specifically, when the lock mechanism is in the restricted state, the threshold value of the diagnosis counter is set low (t1), and the diagnosis is terminated early. In a state where it is unknown whether the lock mechanism is released or restricted or released, the diagnosis counter is set to a high value (t2) so as to continue the diagnosis until the hydraulic pressure is stabilized to some extent, thereby preventing erroneous diagnosis. Incidentally, in the embodiment of FIGS. 5 and 6, the first reference position offset diagnosis is performed only when the lock mechanism is in the restricted state (the flow in the state where it is unknown whether the lock mechanism is released or restricted or released is not shown). After completion of the first reference position offset diagnosis, when the VTC start condition is satisfied due to the water temperature condition or the like (t3), the target cam phase is fixed at the reference value when the diagnosis is abnormal, and is set to achieve the required torque when the diagnosis is normal.

  FIG. 8 shows a time chart for changing the allowable offset value according to the engine speed fluctuation. Since the engine speed is not stable when the engine is started, the engine speed fluctuates as shown in the figure. Since the actual cam position is calculated by a combination of the angle control and the time control, the accuracy of the time control is deteriorated according to the variation of the engine. As a result, the accuracy of the actual cam position deteriorates, and therefore, there is a possibility that a misdiagnosis may occur beyond the offset allowable value due to fluctuations in the engine speed. Therefore, by making the allowable value of the offset variable according to the engine speed, it is possible to prevent erroneous diagnosis.

  In the scene (t0 to t1) in which the engine speed is increasing, the actual cam position is shifted to the advance side, so that the allowable offset value on the advance side is increased. On the other hand, in the scene (t1 to t2) in which the engine speed is decreasing, the actual cam position shifts to the retard side, so the offset allowable value on the retard side is increased. By calculating the allowable offset value according to the change rate of the engine speed fluctuation, it is possible to absorb the influence of only the engine speed fluctuation.

  In addition, since this error is likely to cause an error in the allowable offset value, in order to prevent erroneous diagnosis more reliably, the diagnosis counter threshold value may be increased correspondingly to extend the diagnosis time.

  As mentioned above, although embodiment of this invention was explained in full detail, this invention is not limited to the above-mentioned embodiment, Various in design, without deviating from the mind of this invention described in the claim. Can be changed.

  For example, in the above-described embodiment, the operation of the intake valve has been described, but the same applies to the exhaust valve.

1 Engine 2 Engine body 2a Combustion chamber 3 Cylinder head 4 Cylinder block 4a Cylinder 5 Piston 6 Crankshaft 7 Oil pump 8 Engine control device 8a MPU
8b EP-ROM
8c RAM
8d I / O LSI
DESCRIPTION OF SYMBOLS 11 Air cleaner 13 Throttle body 13a Throttle valve 14 Collector 15 Intake pipe 16 Exhaust pipe 17 Air fuel ratio sensor 18 Catalyst 21 Injector 22 Spark plug 24 Oil control valve 31, 33 Cam shaft 32 Intake valve 34 Exhaust valve 37, 38 Cam pulley 39 Timing belt 41 Water temperature sensor 42 Throttle sensor 43 Air flow sensor 44 Intake pipe internal pressure sensor 51 Valve timing device 52 Variable valve timing mechanism 53 Housing 54 Vane body 60 Crank pulley 61 Lock mechanism 62 Lock pin 64 Lock pin spring 66 Lock hole

Claims (5)

A variable valve timing mechanism that changes the phase of the camshaft relative to the crankshaft of the internal combustion engine by supplying a working fluid; and a lock mechanism that limits or releases the phase of the camshaft relative to the crankshaft according to the fluid pressure of the working fluid; In a vehicle diagnostic apparatus comprising:
The diagnostic device characterized in that the lock mechanism performs a first reference position offset diagnosis of the variable valve timing mechanism when limiting a phase of the camshaft with respect to the crankshaft.   The first reference position offset diagnosis measures the frequency of whether or not the phase of the camshaft is in a predetermined range, and executes a diagnosis determination when the frequency exceeds a diagnosis counter threshold value. The diagnostic apparatus according to 1.   The diagnosis apparatus according to claim 1, wherein the first reference position offset diagnosis makes the diagnosis counter threshold variable according to a state of a lock mechanism.   4. The diagnostic apparatus according to claim 1, wherein the predetermined range and / or the diagnostic counter threshold value are made variable in accordance with fluctuations in engine speed. The vehicle has an idle stop function of automatically stopping the engine when a predetermined driving condition is satisfied, and automatically starting the engine when the predetermined driving condition is satisfied,
5. The diagnostic apparatus according to claim 1, wherein when the first reference position offset diagnosis cannot be completed, idle stop is prohibited and the second reference position offset diagnosis is executed.

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