JP2009156217A - Valve timing control device for internal combustion engine - Google Patents

Abstract

There is provided a valve timing control device capable of surely locking a VVT when an engine is stopped.
When an engine stop request is detected, the VVT is operated in the return direction at the maximum speed (the direction in which the lock pin is inserted into the lock hole) and a predetermined delay time (after the engine stop request is detected). The engine stop is delayed until (Teoff) elapses. The delay time (Teoff) is set based on the VVT return speed (VTc) and the oil temperature (tho) when the VVT is operated in the return direction at the maximum speed.
[Selection] Figure 5

Description

  The present invention relates to a valve timing control device for an internal combustion engine. More specifically, the relative rotation between a housing and a vane body can be locked by inserting a lock pin of a variable valve timing mechanism (hereinafter referred to as VVT) into a lock hole. The present invention relates to a valve timing control device.

  Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-239209, a valve timing control device is known in which the operation of a VVT at the start of an internal combustion engine is regulated by a lock mechanism. The lock mechanism includes a lock pin provided in the VVT vane body and a lock hole provided in the housing, and the relative rotation between the housing and the vane body can be locked by inserting the lock pin into the lock hole. Yes.

  As the driving force of the lock pin, the pressure of oil supplied to the VVT and the biasing force of the spring are used. The urging force of the spring acts in the direction for fitting the lock pin into the lock hole, and the hydraulic pressure acts in the direction for removing the lock pin from the lock hole. For this reason, when the internal combustion engine whose hydraulic pressure is reduced due to the stop of the oil pump is stopped, the lock pin receives the urging force of the spring and is held in the lock hole. After the internal combustion engine is started, when the oil pressure increases with the operation of the oil pump, the oil pressure acting on the lock pin eventually overcomes the urging force of the spring, and the lock pin is detached from the lock hole and the housing and the vane body. Can be rotated relative to each other.

  If the VVT lock is released with the start of the internal combustion engine, the VVT can be operated by supplying oil through the oil control valve. However, the waiting time from the start of the internal combustion engine to the release of the VVT lock depends on the increased hydraulic pressure. For this reason, depending on the timing of starting the operation of the VVT, the VVT may be forcibly operated in a state where the lock has not yet been released, which may cause a malfunction of the VVT due to a lock release failure.

Japanese Patent Application Laid-Open No. 2004-239209 discloses a preventive measure related to incomplete unlocking at start-up. In the valve timing control device disclosed herein, the operation start timing of the VVT immediately after the start of the internal combustion engine is changed according to the oil temperature. The oil viscosity is strongly influenced by the oil pressure increase immediately after the internal combustion engine is started, and the oil viscosity depends on the oil temperature. Therefore, it is possible to predict the timing at which the VVT is unlocked by measuring the oil temperature at the start, and by changing the operation start timing of the VVT according to the oil temperature, the VVT is unlocked before the VVT is unlocked. Can be prevented from operating.
JP 2004-239209 A Japanese Patent Laid-Open No. 11-236831 JP-A-4-284107

  The above-mentioned problem of insufficiency in unlocking at the time of start-up is a problem that can occur only when the VVT is securely locked at the time of start-up of the internal combustion engine. If the VVT is unlocked in a state where the hydraulic pressure is insufficient, another problem arises that the vane body collides with the housing due to the reaction torque received by the camshaft from the valve, and sound is generated. Therefore, in order to prevent the occurrence of such a problem and to make the technique disclosed in Japanese Patent Application Laid-Open No. 2004-239209 effective, the VVT is securely locked when the internal combustion engine is started. It is required to keep.

  In order to lock the VVT, it is necessary to adjust the rotational phase of the vane body with respect to the housing so that the positions of the lock pin and the lock hole coincide with each other. During the operation of the internal combustion engine, the VVT is also operated so as to realize the valve timing according to the operation state. Therefore, the operation of adjusting the rotational phase for locking the VVT is performed after the operation of the internal combustion engine is finished. It becomes from. In the conventional valve timing control device, the VVT is operated in the locking direction using the remaining hydraulic pressure from when the ignition is turned off until the rotation of the internal combustion engine stops completely.

  However, not only the oil pressure but also the oil viscosity affects the operating speed of the VVT. The oil viscosity varies depending on the oil temperature, and also varies depending on the deterioration state of the oil. The higher the oil viscosity, the higher the resistance for operating the VVT. Therefore, if the oil pressure is constant, the higher the oil viscosity, the lower the operating speed of the VVT. For this reason, in the conventional valve timing control device, although the oil viscosity is high, the operating speed of the VVT is slow, and as a result, the ignition engine is turned off and the rotation of the internal combustion engine is completely stopped. There was a possibility that VVT lock could not be completed.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a valve timing control device capable of ensuring the lock of the VVT when the operation of the internal combustion engine is stopped.

In order to achieve the above object, a first aspect of the present invention provides a hydraulic valve timing variable mechanism that varies a valve timing of an internal combustion engine, an oil supply line connected to the valve timing variable mechanism, and the internal combustion engine An oil pump that is driven by the engine to generate oil pressure in the oil in the supply line, and the housing and vane body of the variable valve timing mechanism are moved in a predetermined direction by utilizing the remaining oil pressure when the internal combustion engine is stopped. In a valve timing control device that relatively rotates and inserts a lock pin provided in one of the housing and the vane body into a lock hole provided in any one of the other,
Stop request detecting means for detecting a stop request of the internal combustion engine;
Control means for controlling connection between the valve timing variable mechanism and the supply line so that the housing and the vane body rotate relative to each other in the predetermined direction when the stop request is detected;
Delay means for delaying the stop of the internal combustion engine until a predetermined delay time elapses after the stop request is detected;
Oil temperature measuring means for measuring the temperature of oil supplied to the variable valve timing mechanism;
A response speed measuring means for measuring a response speed of the valve timing variable mechanism when the valve timing variable mechanism is operated by supplying oil;
A delay time setting means for setting the delay time based on the oil temperature measured by the oil temperature measuring means and the response speed measured by the response speed measuring means;
It is characterized by having.

According to a second invention, in the first invention,
The control means controls connection between the variable valve timing mechanism and the supply line so as to relatively rotate the housing and the vane body in the predetermined direction at a maximum speed.

According to a third invention, in the first or second invention,
The delay time setting means includes a reference delay time storage means for storing a reference value for delay time (hereinafter referred to as reference delay time) corresponding to the oil temperature, and a reference value for response speed (hereinafter referred to as reference response speed) as the oil temperature. The reference delay time determined from the oil temperature is corrected based on the comparison between the reference response speed storage means stored in correspondence with the reference temperature and the reference response speed determined from the oil temperature and the actual response speed measured by the response speed measurement means. And a correction means, and a reference delay time after correction is set as a final delay time.

A fourth invention is any one of the first to third inventions,
The delay time setting means changes the setting of the delay time corresponding to the oil temperature and the response speed depending on whether the automatic transmission to which the internal combustion engine is connected is controlled to a shift range of a travel range or a non-travel range. It is characterized by doing.

According to a fifth invention, in any one of the first to fourth inventions,
The delay time setting means changes the setting of the delay time corresponding to the oil temperature and the response speed according to the engine speed when the stop request is detected.

A sixth invention is any one of the first to fifth inventions,
Compression ratio variable means for reducing the compression ratio of the internal combustion engine when the stop request is detected;
Is further provided.

A seventh invention is the invention according to any one of the first to sixth inventions,
The stop request is that an off signal of the ignition switch is detected, and the delay time is a time from when the off signal is detected to when the ignition is actually turned off.

  According to the first invention, when the stop request for the internal combustion engine is detected, the stop of the internal combustion engine is delayed based on the oil temperature and the response speed of the variable valve timing mechanism. The operation time of the timing variable mechanism can be secured. Thereby, even if the oil viscosity when the engine is stopped is high, the lock pin can be securely inserted into the lock hole when the engine is stopped. Moreover, the delay time is set based on the oil temperature highly correlated with the oil viscosity and the response speed of the variable valve timing mechanism, so that the engine stop can be delayed unnecessarily while ensuring the lock of the variable valve timing mechanism. It can also prevent the driver from feeling uncomfortable.

  According to the second invention, by rotating the housing and the vane body relative to each other at the maximum speed, it is possible to minimize the operation time of the variable valve timing mechanism required for fitting the lock pin into the lock hole. Accordingly, the required delay time can be shortened.

  According to the third aspect of the invention, it is possible to set an optimal delay time in order to achieve both reliable locking of the variable valve timing mechanism and prevention of uncomfortable feeling due to a delay in engine stop. More specifically, although the required delay time is determined by the oil viscosity, if the temperature dependence characteristic of the oil viscosity is constant, the delay time can be determined from the oil temperature. However, the temperature dependence characteristic of oil viscosity varies depending on the deterioration state of the oil. The index value that indicates the deterioration state of the oil is a comparison value between the reference response speed determined from the oil temperature and the actual response speed, and the reference delay time determined from the oil temperature is corrected by this comparison value. It is possible to set an optimal delay time that reflects the degradation state of.

  According to the fourth aspect of the invention, the delay time setting is changed depending on whether the shift range of the automatic transmission is controlled to the traveling range or the non-traveling range, so that the valve can be set in any range. It is possible to achieve both the reliable locking of the timing variable mechanism and the prevention of uncomfortable feeling due to the delay of the engine stop.

  According to the fifth aspect of the invention, the delay time setting is changed in accordance with the engine rotational speed when a request for stopping the internal combustion engine is detected, so that the valve can be operated in any rotational state. It is possible to achieve both the reliable locking of the timing variable mechanism and the prevention of uncomfortable feeling due to the delay of the engine stop.

  According to the sixth aspect of the present invention, when a request to stop the internal combustion engine is detected, the inertial stop time of the internal combustion engine can be increased by reducing the compression ratio of the internal combustion engine. Can be shortened.

  According to the seventh aspect, since the delay time from when the ignition switch is turned off until when the ignition is actually turned off can be used as the delay time, the control circuit is changed with respect to the conventional valve timing control device. Can be minimized.

Embodiment 1 FIG.
Hereinafter, a valve timing control apparatus for an internal combustion engine (hereinafter referred to as an engine) as Embodiment 1 of the present invention will be described with reference to FIGS.

  The outline of the configuration of the valve timing control apparatus of the present embodiment can be described with reference to FIG. FIG. 1 shows a hydraulic circuit of the valve timing control device. As shown in this figure, the valve timing control device includes a variable valve timing mechanism (hereinafter referred to as VVT) 20 which is a hydraulic actuator. It is assumed that this VVT 20 is combined with an intake valve. The VVT 20 includes a housing 22 connected to a crankshaft by a belt or a chain, and a vane body 24 that is disposed in the housing 22 and rotates integrally with the camshaft.

  Two oil chambers 26 and 28 defined by a vane body 24 are formed inside the housing 22. According to the VVT 20, by changing the volume ratio between the two oil chambers 26 and 28, the vane body 24 can be rotated with respect to the housing 22, and the rotational phase of the camshaft with respect to the crankshaft can be changed. The valve timing can be changed. Of the two oil chambers 26, 28, the oil chamber 26 on the side that expands the volume when the valve timing is advanced is referred to as an advance oil chamber, and the oil chamber 28 on the side that reduces the volume is referred to as a retarded oil chamber. Conversely, when the valve timing is retarded, the volume of the retard oil chamber 28 is increased and the volume of the advance oil chamber 26 is decreased.

  The VVT 20 can change the volume ratio between the oil chambers 26 and 28 by selectively supplying oil (operating oil) to either the advance oil chamber 26 or the retard oil chamber 28. When oil is supplied to the advance oil chamber 26, the advance oil chamber 26 expands by the amount of the supplied oil, and the oil from the retard oil chamber 28 increases as the advance oil chamber 26 expands. Extruded. Conversely, when oil is supplied to the retarded oil chamber 28, the retarded oil chamber 28 expands by the amount of the supplied oil, and the advanced oil chamber 26 contracts as the oil is pushed out.

  The VVT 20 is provided with a locking mechanism for locking the operation of the VVT 20. The lock mechanism includes a lock pin 30 provided in the vane body 24 of the VVT 20 and a lock hole 32 formed in the housing 22. When the lock pin 30 is engaged with the lock hole 32, the vane body 24 is fixed to the housing 22 at a predetermined rotation angle. The lock of the VVT 20 by the lock mechanism is performed when the engine 2 is stopped, and is released when the engine 2 is started. The position of the lock hole 32 is not limited when the present invention is applied to the valve timing control device, but in the present embodiment, the lock hole 32 is provided at a position where the valve timing is most retarded. To do.

  The driving force for driving the lock pin 30 in this lock mechanism is the urging force of a spring (not shown) built in the vane body 24 and the hydraulic pressure of oil supplied to the VVT 20. The biasing force of the spring acts in a direction to push the lock pin 30 into the lock hole 32, and the oil pressure of the oil acts in a direction to push out the lock pin 30 from the lock hole 32. Therefore, when the engine 2 is started, the lock pin 30 remains fitted in the lock hole 32 until the oil pressure of the oil rises due to the rotation of the oil pump 4, and the VVT 20 is held in the locked state. When the hydraulic pressure rises to some extent, the lock pin 30 is pushed out from the lock hole 32, and the lock of the VVT 20 is released.

  The oil supplied to the VVT 20 is taken out from the main oil gallery 6 through the VVT line 8. The main oil gallery 6 is a main oil flow path extending from the oil pump 4, and the oil flowing there is supplied not only to the hydraulic actuators other than the VVT 20, but also to the sliding portions in the engine 2 as lubricating oil. ing. The oil pump 4 is connected to the crankshaft of the engine 2 by a gear, a chain, or a belt, and is rotated by the driving force of the engine 2 to generate oil pressure in the oil in the main oil gallery 6. The oil temperature in the main oil gallery 6 can be measured by an oil temperature sensor 42 attached to the main oil gallery 6. The VVT line 8 is a branch channel branched from the main oil gallery 6 and constitutes an oil supply line together with the main oil gallery 6.

  An oil control valve (hereinafter referred to as OCV) 10 is attached to the tip of the VVT line 8. The OCV 10 and the advance oil chamber 26 of the VVT 20 are connected by an advance oil chamber line 38, and the retard oil chamber 28 of the VVT 20 is connected by a retard oil chamber line 36. The OCV 10 is a line switching valve that switches the oil supply destination between the advance oil chamber line 38 and the retard oil chamber line 36, and at the same time, is a flow rate adjustment valve that can adjust the oil supply amount by controlling the opening degree. .

  Specifically, the OCV 10 is an electromagnetically driven spool valve that can control the supply and discharge of oil to and from the advance oil chamber line 38 and the retard oil chamber line 36 according to the position of the spool in the sleeve. The spool has one end in the moving direction supported by a spring and the other end supported by a solenoid. The position of the spool can be controlled by the duty ratio of the drive current supplied to the solenoid. When the solenoid is not energized, the spool is placed at a predetermined initial position by the biasing force of the spring. In this initial position, the VVT line 8 is connected to the retarded oil chamber line 36.

  The control of the OCV 10 is performed by an electronic control unit (hereinafter referred to as ECU) 40 that integrally controls the entire engine 2. In addition to the oil temperature sensor 42 attached to the main oil gallery 6, the ECU 40 receives signals from various sensors and switches such as a crank angle sensor 44, a cam angle sensor 46, a throttle opening sensor 48, and an ignition switch 50. Is done. The ignition switch 50 is a switch disposed in the vehicle interior, and an ON signal means an engine start request from the driver to the ECU 40, and an OFF signal means an engine stop request from the driver to the ECU 40. The ECU 40 controls the engine 2 based on signals from these sensors and switches, and also controls the OCV 10.

  The ECU 40 supplies the OCV 10 with a duty ratio signal for driving the solenoid. The duty ratio is determined based on the deviation between the target value and the actual value of the valve timing. The solenoid is driven by the supplied duty ratio signal, and moves the spool to a position determined by the duty ratio. As a result, a desired amount of oil is supplied to a desired side of the two oil chambers 26, 28 of the VVT 20, and the target valve timing is realized.

  Supply of the duty ratio signal to the OCV 10 by the ECU 40 is performed after the engine 2 is started and after the lock of the VT 20 is released. The VVT 20 immediately after the start of the engine 20 is in a locked state at the most retarded position that is the locked position. However, when the oil pump 4 is driven by the engine 2 and the oil whose hydraulic pressure has been increased by the oil pump 4 is supplied to the VVT 20, the lock pin 30 is eventually removed from the lock hole 32 and the operation of the VVT 20 becomes possible. If the OCV 10 is controlled to the advance side after the lock of the VVT 20 is released, it is possible to prevent the occurrence of problems such as lock release failure.

  On the other hand, when the operation of the engine 2 is stopped, the ECU 40 controls the OCV 10 to the retard side to operate the VVT 20 to the lock position. The rotation of the oil pump 4 driven by the engine 2 is also stopped, and the oil pressure of the oil in the hydraulic circuit is lowered as the operation of the oil pump 4 is stopped. However, there is a time lag from the stop of operation of the oil pump 4 until the hydraulic pressure has dropped, and the remaining hydraulic pressure exists in the hydraulic circuit for a while. By controlling the OCV 10 to the retard side when the operation of the engine 2 is stopped, it is possible to operate the VVT 20 toward the lock position using the remaining hydraulic pressure in the hydraulic circuit.

  In order for the VVT 20 to reliably return to the lock position and the lock pin 30 to be securely inserted into the lock hole 32, the hydraulic pressure remains in the hydraulic circuit until that time. Therefore, in the valve timing control apparatus of the present embodiment, a delay time is provided between the time when the engine 2 stop request is detected and the time when the engine 2 is actually stopped. The return operation of the VVT 20 to the locked position starts from the time when the engine 2 is requested to stop. By delaying the stop of the engine 2, the return of the VVT 20 to the lock position can be advanced during the delay time, and the insertion of the lock pin 30 into the lock hole 32 can be ensured. Hereinafter, control for delaying engine stop in the present embodiment is referred to as engine stop delay control.

  In the engine stop delay control of the present embodiment, the engine stop delay time is changed according to the oil viscosity. However, in order to directly measure the oil viscosity, a dedicated measuring device is required, which is not realistic when considering the cost. In the present embodiment, the oil viscosity is estimated based on information obtained by an existing sensor, instead of directly measuring the oil viscosity. One piece of information that can be used to estimate the oil viscosity is the oil temperature that can be measured by the oil temperature sensor 42. FIG. 2 is a graph showing the relationship between oil viscosity and oil temperature. As shown in this figure, the viscosity of the oil is high when the oil temperature is low, and has a temperature-dependent characteristic that it decreases as the oil temperature increases.

  The temperature-dependent characteristics of oil viscosity (hereinafter referred to as oil viscosity characteristics) vary depending on the oil type and the deterioration status. FIG. 2 illustrates oil viscosity characteristics of a new high-viscosity oil and a deteriorated one, and a new low-viscosity oil and a deteriorated one. Even if the oil temperature is the same, if the viscosity characteristics are different, the oil viscosity has a different value, so that there is a difference in the delay time required in the engine stop delay control. Therefore, it is required to consider the viscosity characteristics of the oil currently used for setting the delay time.

  In the engine stop delay control according to the present embodiment, a reference delay time is preset for each oil temperature. As the reference delay time, an optimum delay time when a predetermined reference oil (for example, a new low-viscosity oil) is used is used. FIG. 3 is a diagram showing the relationship between the oil temperature (tho) and the reference delay time (kTeoff). The ECU 40 stores the relationship shown in FIG. 3 as map data. By obtaining the reference delay time (kTeoff) corresponding to the oil temperature (tho) from the map shown in FIG. 3 and correcting it according to the viscosity characteristics of the oil currently used, the optimum delay corresponding to the oil viscosity is obtained. It becomes possible to set the time.

  The oil viscosity characteristic is reflected in the responsiveness of the VVT 20 when the OCV 10 is controlled to operate the VVT 20. When the oil used is a high-viscosity oil, the oil viscosity at the same oil temperature is higher than that of a low-viscosity oil, and as a result, the responsiveness of the VVT 20 becomes dull. Specifically, the response of the VVT 20 can be represented by the response speed of the VVT 20 when a constant duty ratio signal is supplied to the OCV 10. The response speed of the VVT 20 can be measured using the crank angle signal from the crankshaft sensor 44 and the cam angle signal from the camshaft sensor 46. The change speed of the phase difference between the crank angle signal and the cam angle signal is the response speed of the VVT 20.

  In the engine stop delay control according to the present embodiment, a reference response speed corresponding to the oil temperature is calculated and compared with the actual response speed. As the reference response speed, the return speed when the above-described reference oil is used and the duty ratio signal supplied to the OCV 10 is set to 0% is used. FIG. 4 is a diagram showing the relationship between the oil temperature (tho) and the reference VVT return speed (kVTc). The ECU 40 stores the relationship shown in FIG. 4 as map data. Obtain the reference VVT return speed (kVTc) corresponding to the current oil temperature from the map shown in FIG. 4 and calculate the VVT return speed ratio (kVTc / VTc), which is the ratio of this to the actual VVT return speed (VTc). Thus, it is possible to obtain an index value indicating the viscosity characteristic of the currently used oil. The greater the VVT return speed ratio (kVTc / VTc), the higher the viscosity characteristic of the oil. By correcting the above-mentioned reference delay time using this VVT return speed ratio (kVTc / VTc), an optimum delay time corresponding to the current oil viscosity can be obtained.

  FIG. 5 is a flowchart showing a routine when the ECU 40 executes the engine stop delay control. The ECU 40 executes the routine shown in the flowchart of FIG. 5 at a constant cycle. Hereinafter, the flow of the engine stop delay control executed in the present embodiment will be described with reference to the flowchart of FIG.

  In the first step S102 of the routine shown in FIG. 5, the VVT return speed (VTc) when the duty ratio signal supplied to the OCV 10 is set to 0% and the VVT 20 is operated at the maximum speed on the retard side is captured. In step S104, the oil temperature (tho) measured by the oil temperature sensor 42 is captured.

In the next step S106, a reference VVT return speed (kVTc) corresponding to the oil temperature (tho) is obtained based on the map shown in FIG. In step S108, a reference delay time (kTeoff) corresponding to the oil temperature (tho) is obtained based on the map shown in FIG. In step S110, the delay time (Teoff) is obtained by the following equation 1 using the VVT return speed (VTc), the reference VVT return speed (kVTc), and the reference delay time (kTeoff). In Equation 1, the VVT return speed ratio (kVTc / VTc) is used as a correction coefficient for the reference delay time (kTeoff).
Teoff = kTeoff × (kVTc / VTc) Equation 1

  In step S112, it is determined whether an engine stop request has been detected. It is determined that an engine stop request has been received from the driver when the off signal of the ignition switch 50 is detected. Until the engine stop request is detected, the following processing is skipped, and the processing from steps S102 to S110 is repeated.

  If an engine stop request is detected, the processing after step S114 is performed. First, in step S114, the elapsed time (Te) from the detection of the engine stop request is captured. In the next step S116, the delay time (Teoff) obtained in step S110 is compared with the current elapsed time (Te) to determine whether or not the delay time (Teoff) has elapsed since the detection of the engine stop request. Is done. If the delay time (Teoff) has not elapsed as a result of the determination in step S116, the engine stop delay control is continued as it is (step S120). On the other hand, if the delay time (Teoff) has elapsed, the ignition is turned off and the engine 2 is stopped (step S118).

  As described above, according to the engine stop delay control of the present embodiment, when an engine stop request is detected, the engine 2 is stopped based on the oil temperature (tho) and the VVT return speed (VTc). Therefore, the operation time of the VVT 20 can be secured longer by the delay time (Teoff). Thereby, even if the oil viscosity when the engine is stopped is high, the lock pin 30 can be securely inserted into the lock hole 32 when the engine is stopped.

  Moreover, according to the engine stop delay control of the present embodiment, the delay time (Teoff) is set based on the oil temperature (tho) and the VVT return speed (VTc) that are highly correlated with the oil viscosity. More specifically, the oil viscosity characteristics are reflected by correcting the reference delay time (kTeoff) determined from the oil temperature (tho) by the VVT return speed ratio (kVTc / VTc), which is an index value of the oil viscosity characteristics. Optimal delay time (Teoff) is set. By optimally setting the delay time (Teoff), it is possible to prevent the driver 2 from feeling uncomfortable by unnecessarily delaying the stop of the engine 2 while ensuring the lock of the VVT 20.

  Next, control during operation of the engine 2 that is performed together with the above-described engine stop delay control in the valve timing control device of the present embodiment will be described.

  In the engine stop delay control described above, the reference delay time (kTeoff) and the reference VVT return speed (kVTc) are set on the assumption that the VVT 20 is operated at the maximum speed on the retard side. This is because the delay time required for reliable locking of the VVT 20 is shortened to minimize the engine stop delay. However, since it is not known when the stop request for the engine 2 is generated, the VVT 20 does not always operate at the maximum speed on the retard side depending on the operating state of the engine 2. Therefore, the ECU 40 performs the VVT duty 0% priority control described below during operation of the engine 2 in order to maximize the effect of the engine stop delay control.

  In the VVT duty 0% priority control, the duty ratio signal for operating the VVT 20 to the retarded angle side is forcibly set to 0% under a certain condition, and no matter what time the engine 2 stop request is generated, the VVT 20 Is a control that makes it possible to operate at a maximum speed on the retard side. FIG. 6 is a flowchart showing a routine when the ECU 40 executes the VVT duty 0% priority control. The ECU 40 executes the routine shown in the flowchart of FIG. 6 at a constant cycle. Hereinafter, the flow of the VVT duty 0% priority control executed in the present embodiment will be described with reference to the flowchart of FIG.

  In the first step S202 of the routine shown in FIG. 6, the current VVT return speed (VTc) is captured. In step S204, the oil temperature (tho) measured by the oil temperature sensor 42 is captured. In step S206, a reference VVT return speed (kVTc) corresponding to the oil temperature (tho) is obtained based on the map shown in FIG.

  In the next step S208, the VVT return speed (VTc) captured in step S202 is compared with the reference VVT return speed (kVTc). As a result of the comparison, if the current VVT return speed (VTc) is equal to or higher than the reference VVT return speed (kVTc), the routine proceeds to step S220, where normal valve timing control (hereinafter, normal VVT control) is performed. In the normal VVT control, the duty ratio signal supplied to the OCV 10 is determined based on the deviation between the target value and the actual value of the valve timing.

  On the other hand, when the current VVT return speed (VTc) has not reached the reference VVT return speed (kVTc), the processing from step S210 is performed. First, in step S210, the current engine speed (NE) and throttle opening (TA) are captured. In the next step S212, it is determined whether or not the engine speed (NE) is smaller than the threshold value A. If the engine speed (NE) is smaller than the reference value A, it is further determined whether or not the throttle opening (TA) is smaller than the threshold value B in the next step S214. If the engine speed (NE) is greater than or equal to the threshold A or the throttle opening (TA) is greater than or equal to the threshold B, the process proceeds to step S220 and normal VVT control is performed.

  When the engine speed (NE) is smaller than the threshold value A and the throttle opening (TA) is smaller than the threshold value B, that is, when the engine 2 is operated in a low rotation and low load region, the process goes to VVT20. It is determined whether or not there is a retardation request (step S216). When there is no retard angle request, that is, when there is no valve timing change request or when the request is an advance angle request, the routine proceeds to step S220, where normal VVT control is performed. On the other hand, when the retardation request for VVT 20 is detected, the duty ratio signal is forcibly set to 0% by the VVT duty 0% priority control (step S218).

  As described above, according to the VVT duty 0% priority control of the present embodiment, the duty ratio signal when the VVT 20 is operated to the retard side is forcibly set to 0%, so Even when a stop request is generated, the VVT 20 can be operated to the retard side at the maximum speed. According to this, the operation time of the VVT 20 required for fitting the lock pin 30 into the lock hole 32 can be minimized, and the required delay time can be shortened accordingly.

  In addition, since the VVT duty 0% priority control is limited to the case where the engine 2 is operated in a low rotation and low load range, the engine 2 in the high rotation range and high load range where accurate valve timing control is required. There is no effect on driving performance. On the other hand, with regard to the reliable locking of the VVT 20 when the engine is stopped, the reliable locking is ensured without performing the VVT duty 0% priority control in the high rotation range or high load range. This is because when the engine 2 is in the high rotation range, there is a margin in the time until the rotation of the engine 2 stops completely. Further, since the accelerator is always returned before the ignition is turned off, it may be considered that a request to stop the engine 2 from the driver does not occur in the high load region.

  The valve timing control device as the first embodiment of the present invention has been described above. The correspondence relationship between the first embodiment and the first invention and each invention subordinate thereto is as follows. First, in FIG. 1, VVT 20 corresponds to the “valve timing variable mechanism” of the first invention. The main oil gallery 6 and the VVT line 8 correspond to the “oil supply line” of the first invention, and the oil pump 4 corresponds to the “oil pump” of the first invention.

  When the ECU 40 detects the off signal of the ignition switch 50, the “stop request detecting means” of the first invention is realized. When the ECU 40 takes in the oil temperature signal from the oil temperature sensor 42, the “oil temperature measuring means” of the first invention is realized. Further, the ECU 40 captures the crank angle signal from the crankshaft sensor 44 and the cam angle signal from the camshaft sensor 46, thereby realizing the “response speed measuring means” of the first invention. The ECU 40, together with the OCV 10, constitutes the “control means” of the first invention. The ECU 40 executes the routine shown in FIG. 6 to realize the “control means” of the second invention.

  The ECU 40 executes steps S112, S114, S116, S118, and S120 of the routine shown in FIG. 5 to realize the “delay means” of the first invention. The ECU 40 executes steps S102, S104, S106, S108 and S110 of the routine shown in FIG. 5 to realize the “delay time setting means” of the first and third aspects of the invention. The map shown in FIG. 3 corresponds to “reference delay time storage means” of the third invention, and the map shown in FIG. 4 corresponds to “reference response speed storage means” of the third invention. The process of step S110 corresponds to the “correction unit” of the third invention.

Embodiment 2. FIG.
Next, a valve timing control device as a second embodiment of the present invention will be described with reference to FIG. 1, FIG. 4, FIG. 7 and FIG. The valve timing control apparatus of the present embodiment includes a hydraulic circuit having the same configuration as that of the first embodiment. Therefore, in the following description, it is assumed that the configuration shown in FIG.

  The valve timing control device according to the present embodiment and the one according to the first embodiment are common in that a delay time is provided from the detection of the engine stop request to the engine stop in order to ensure the lock of the VVT 20 when the engine is stopped. To do. However, there is a difference between the present embodiment and the first embodiment in the content of the engine stop delay control for delaying the engine stop. Hereinafter, features of the engine stop delay control performed in the present embodiment will be described with reference to FIGS.

  The engine stop delay control of the present embodiment is characterized in that a difference is provided in the setting of the delay time depending on the shift range of the automatic transmission when the engine is stopped. When the shift range of the automatic transmission is in the D, R range (traveling range), the engine speed is lower than in the N, P range (non-traveling range). For this reason, the time required for the engine 2 to stop rotating after the ignition is turned off is shorter in the D and R ranges, and the required delay time is increased accordingly. FIG. 7 is a diagram showing a map for determining the reference delay time (kTeoff) from the oil temperature (tho) used in the present embodiment. In this map, map data for the D and R ranges and map data for the N and P ranges are prepared separately. If the oil temperature (tho) is the same, the reference delay time (kTeoff) for the D and R ranges is set to a larger value than the reference delay time (kTeoff) for the N and P ranges. Yes.

  FIG. 8 is a flowchart showing a routine when the ECU 40 executes the engine stop delay control. The ECU 40 executes the routine shown in the flowchart of FIG. 8 at a constant cycle. Hereinafter, the flow of engine stop delay control executed in the present embodiment will be described with reference to the flowchart of FIG. In FIG. 8, the same step numbers are assigned to the processes common to the engine stop delay control according to the first embodiment. In the following description, description of contents common to those of the first embodiment will be omitted or simplified.

  In the first step S102 of the routine shown in FIG. 8, the VVT return speed (VTc) when the duty ratio signal supplied to the OCV 10 is set to 0% is captured, and in step S104, the oil temperature (tho) is captured. In the next step S106, a reference VVT return speed (kVTc) corresponding to the oil temperature (tho) is obtained based on the map shown in FIG.

  Next, in the engine stop delay control of the present embodiment, it is determined whether or not the shift range of the automatic transmission is in the D or R range (step S302). The shift range of the automatic transmission can be determined by a signal generated by the shift switch. As a result of the determination, if the shift range is the D or R range, the reference delay time (kTeoff) for the D and R ranges corresponding to the oil temperature (tho) is obtained based on the map shown in FIG. 7 (step S304). ). On the other hand, if the shift range is the N or P range, the reference delay time (kTeoff) for the N and P ranges corresponding to the oil temperature (tho) is obtained based on the map shown in FIG. 7 (step S306).

  In the next step S110, the delay time (Teoff) is obtained by the above-described equation 1 based on the reference delay time (kTeoff) obtained in step S304 or S306. Since the processing after step S112 is completely the same as that of the first embodiment, the description thereof is omitted.

  As described above, according to the engine stop delay control of the present embodiment, the delay time (Teoff) is set depending on whether the shift range of the automatic transmission is controlled to the D, R range, N, or P range. Is changed. This makes it possible to achieve both reliable locking of the VVT 20 and prevention of a sense of incongruity due to a delay in engine stop, regardless of the range of the automatic transmission when the engine is stopped.

  In the second embodiment, the “delay time setting means” according to the fourth aspect of the present invention is realized when the ECU 40 executes steps S302, S304, and S306 of the routine shown in FIG. The correspondence relationship between the second embodiment and other inventions is common to the correspondence relationship between the first embodiment and other inventions.

Embodiment 3 FIG.
Next, a valve timing control device as a third embodiment of the present invention will be described with reference to FIG. 1, FIG. 3, FIG. 4, FIG. 9 and FIG. The valve timing control apparatus of the present embodiment includes a hydraulic circuit having the same configuration as that of the first embodiment. Therefore, in the following description, it is assumed that the configuration shown in FIG.

  The valve timing control device according to the present embodiment and the one according to the first embodiment are common in that a delay time is provided from the detection of the engine stop request to the engine stop in order to ensure the lock of the VVT 20 when the engine is stopped. To do. However, there is a difference between the present embodiment and the first embodiment in the content of the engine stop delay control for delaying the engine stop. Hereinafter, features of the engine stop delay control implemented in the present embodiment will be described with reference to FIGS. 9 and 10.

  The engine stop delay control according to the present embodiment is characterized in that the delay time is changed according to the engine speed when the engine stop request is detected. The lower the engine speed, the shorter the time required for the engine 2 to stop rotating after the ignition is turned off, so the delay time required for reliable locking of the VVT 20 becomes longer. FIG. 9 is a diagram showing a map for determining a delay time correction coefficient (kneend) from the engine speed (NEend) at the time of engine stop request, which is used in the present embodiment. In this map, the basic value of the correction coefficient (kneend) is 1.0, and when the engine speed (NEend) is equal to or less than a predetermined value, the lower the engine speed (NEend), the correction coefficient (kneend) is greater than 1.0. Is also set to be large.

  FIG. 10 is a flowchart showing a routine when the ECU 40 executes the engine stop delay control. The ECU 40 executes the routine shown in the flowchart of FIG. 10 at a constant cycle. Hereinafter, the flow of engine stop delay control executed in the present embodiment will be described with reference to the flowchart of FIG. In FIG. 10, the same step numbers are assigned to the processes common to the engine stop delay control according to the first embodiment. In the following description, description of contents common to those of the first embodiment will be omitted or simplified.

  The processing from steps S102 to S110 of the routine shown in FIG. 10 is completely the same as that in the first embodiment. A delay time (Teoff) corresponding to the VVT return speed (VTc) and the oil temperature (tho) when the duty is 0% is obtained using the maps shown in FIGS. In step S112, it is determined whether an engine stop request has been detected. Until the engine stop request is detected, the following processing is skipped, and the processing from step S102 to S110 is repeated.

If an engine stop request is detected, the processing after step S402 is performed. First, in step S402, the engine speed (NEend) when the engine stop request is detected is taken. In the next step S404, a delay time correction coefficient (kneend) corresponding to the engine speed (NEend) is obtained based on the map shown in FIG. In step S406, the final delay time (TEOFF) is obtained by the following equation 2 using the delay time (Teoff) and the delay time correction coefficient (kneend).
TEOFF = Teoff × kneend ・ ・ ・ Equation 2

  In the next step S114, an elapsed time (Te) from the detection of the engine stop request is captured. In step S408, the final delay time (TEOFF) obtained in step S406 is compared with the current elapsed time (Te), and whether the delay time (TEOFF) has elapsed since the detection of the engine stop request is detected. It is determined whether or not. If the delay time (TEOFF) has not elapsed as a result of the determination in step S408, the engine stop delay control is continued as it is (step S120). On the other hand, if the delay time (TEOFF) has elapsed, the ignition is turned off and the engine 2 is stopped (step S118).

  As described above, according to the engine stop delay control of the present embodiment, the delay time (TEOFF) is set according to the engine rotation speed (NEend) when the stop request of the engine 2 from the driver is detected. Is changed. This makes it possible to achieve both reliable locking of the VVT 20 and prevention of a sense of incongruity due to a delay in engine stop, regardless of the rotation state of the engine 2.

  In the third embodiment, the “delay time setting means” according to the fifth aspect of the present invention is realized when the ECU 40 executes steps S402, S404 and S406 of the routine shown in FIG. The correspondence between the third embodiment and other inventions is common to the correspondence between the first embodiment and other inventions.

Embodiment 4 FIG.
Next, a valve timing control apparatus according to a fourth embodiment of the present invention will be described with reference to FIGS. The valve timing control apparatus of the present embodiment includes a hydraulic circuit having the same configuration as that of the first embodiment. Therefore, in the following description, it is assumed that the configuration shown in FIG.

  The valve timing control device according to the present embodiment and the one according to the first embodiment are common in that a delay time is provided from the detection of the engine stop request to the engine stop in order to ensure the lock of the VVT 20 when the engine is stopped. To do. However, there is a difference between the present embodiment and the first embodiment in the content of the engine stop delay control for delaying the engine stop. Hereinafter, features of the engine stop delay control performed in the present embodiment will be described with reference to FIGS. 11 and 12.

  First, as a premise of the engine stop delay control of the present embodiment, it is assumed that the engine 2 is provided with a compression ratio variable mechanism capable of changing the compression ratio. The compression ratio variable mechanism may be a means for making the compression ratio variable by mechanically changing the piston stroke length or the cylinder volume, or a means for making the substantial compression ratio variable by changing the closing timing of the exhaust valve. Good. The compression ratio of the engine 2 affects the speed at which the engine speed decreases after the ignition is turned off. If the compression ratio is low, the pumping loss and the friction are also reduced, and the reduction speed of the engine speed is correspondingly reduced.

  The engine stop delay control of the present embodiment is characterized in that the compression ratio is lowered when an engine stop request is detected. Decreasing the compression ratio slows down the engine speed, and accordingly, the delay time required for reliable locking of the VVT 20 can be shortened. FIG. 11 is a diagram showing a comparison between a decrease in engine speed and a necessary delay time when the compression ratio of the engine 2 is high and when the compression ratio is low.

  FIG. 12 is a flowchart showing a routine when the ECU 40 executes engine stop delay control. The ECU 40 executes the routine shown in the flowchart of FIG. 12 at a constant cycle. Hereinafter, the flow of the engine stop delay control executed in the present embodiment will be described with reference to the flowchart of FIG. In FIG. 12, the same step numbers are assigned to processes common to the engine stop delay control according to the first embodiment. In the following description, description of contents common to those of the first embodiment will be omitted or simplified.

  The processing from step S102 to S110 of the routine shown in FIG. 12 is completely the same as that of the first embodiment. A delay time (Teoff) corresponding to the VVT return speed (VTc) and the oil temperature (tho) when the duty is 0% is obtained using the maps shown in FIGS. In step S112, it is determined whether an engine stop request has been detected. Until the engine stop request is detected, the following processing is skipped, and the processing from step S102 to S110 is repeated.

  When an engine stop request is detected, first, the process of step S502 is performed, and then the processes after step S114 are performed. In step S502, the compression ratio of the engine 2 is lowered to the lowest compression ratio that can be realized by the variable compression ratio mechanism. In the present embodiment, it is assumed that a map (reference map shown in FIG. 3) of the reference delay time (kTeoff) is created assuming this minimum compression ratio. Since the processing after step S114 is completely the same as that of the first embodiment, the description thereof is omitted.

  As described above, according to the engine stop delay control of the present embodiment, when the stop request of the engine 2 from the driver is detected, the compression ratio of the engine 2 is changed to the minimum compression ratio. Thereby, since the inertial stop time of the engine 2 after the ignition is turned off becomes longer, the necessary delay time (Teoff) can be shortened accordingly, and the driver can be prevented from feeling uncomfortable.

Others.
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  In the above-described embodiment, the VVT 20 is combined with the intake valve, but may be combined with the exhaust valve. In that case, the VVT 20 is locked at a position where the valve timing is most advanced. Further, the position of the spool of the OCV 10 when not energized is a position where the VVT line 8 is connected to the advance oil chamber 26. In the case of the VVT 20 for the exhaust valve, if the VVT 20 is not securely locked when the engine 2 is started, the VVT 20 moves due to the reaction force of the cam. In this case, since the VVT 20 moves in a direction that retards the valve timing of the exhaust valve, the valve overlap is enlarged, which leads to deterioration of combustion at the start. Therefore, when the VVT 20 is used for an exhaust valve, more reliable locking is required when the engine is stopped than when the VVT 20 is used for an intake valve.

  In the above-described embodiment, the oil temperature is directly measured by the oil temperature sensor 42, but may be indirectly measured by a water temperature sensor. This is because there is a correlation between the oil temperature of the oil in the engine 2 and the coolant temperature. In this case, the “oil temperature measuring means” is configured by the ECU 40 and the water temperature sensor.

It is a figure which shows schematic structure of the valve timing control apparatus as Embodiment 1 of this invention. It is a figure which shows the relationship between oil viscosity and oil temperature about several oil from which a viscosity characteristic differs. It is a figure which shows the map for determining a reference | standard delay time from the oil temperature used in Embodiment 1 of this invention. It is a figure which shows the map for determining reference | standard VVT return speed from the oil temperature used in Embodiment 1 of this invention. It is a flowchart which shows the routine of the engine stop delay control performed in Embodiment 1 of this invention. It is a flowchart which shows the routine of VVT duty 0% priority control performed in Embodiment 1 of this invention. It is a figure which shows the map for determining a reference | standard delay time from the oil temperature used in Embodiment 2 of this invention. It is a flowchart which shows the routine of the engine stop delay control performed in Embodiment 2 of this invention. It is a figure which shows the map for determining a delay time correction coefficient from the engine speed at the time of the engine stop request | requirement used in Embodiment 3 of this invention. It is a flowchart which shows the routine of the engine stop delay control performed in Embodiment 3 of this invention. It is a figure which compares the case where the compression ratio of an engine is a high compression ratio, and the case where it is a low compression ratio, and compares the fall condition of engine speed, and required delay time, respectively. It is a flowchart which shows the routine of the engine stop delay control performed in Embodiment 4 of this invention.

Explanation of symbols

2 Engine 4 Oil pump 6 Main oil gallery 8 VVT line 10 Oil control valve 20 Variable valve timing mechanism (VVT)
22 housing 24 vane body 26 advance oil chamber 28 retard oil chamber 30 lock pin 32 lock hole 34 retard oil chamber line 36 advance oil chamber line 40 ECU
42 Oil temperature sensor 44 Crankshaft sensor 46 Camshaft sensor 48 Throttle opening sensor 50 Ignition switch

Claims (7)

A hydraulic valve timing variable mechanism that varies the valve timing of the internal combustion engine, an oil supply line connected to the valve timing variable mechanism, and an oil pressure that is driven by the internal combustion engine to generate oil in the supply line An oil pump for rotating the housing and the vane body of the variable valve timing mechanism in a predetermined direction by utilizing the remaining oil pressure when the internal combustion engine is stopped, and either the housing or the vane body In the valve timing control device that fits the lock pin provided on the other into the lock hole provided on the other,
Stop request detecting means for detecting a stop request of the internal combustion engine;
Control means for controlling connection between the valve timing variable mechanism and the supply line so that the housing and the vane body rotate relative to each other in the predetermined direction when the stop request is detected;
Delay means for delaying the stop of the internal combustion engine until a predetermined delay time elapses after the stop request is detected;
Oil temperature measuring means for measuring the temperature of oil supplied to the variable valve timing mechanism;
A response speed measuring means for measuring a response speed of the valve timing variable mechanism when the valve timing variable mechanism is operated by supplying oil;
A delay time setting means for setting the delay time based on the oil temperature measured by the oil temperature measuring means and the response speed measured by the response speed measuring means;
A valve timing control device for an internal combustion engine, comprising:   2. The control unit according to claim 1, wherein the control unit controls connection between the valve timing variable mechanism and the supply line so as to relatively rotate the housing and the vane body in the predetermined direction at a maximum speed. A valve timing control device for an internal combustion engine.   The delay time setting means includes a reference delay time storage means for storing a reference value for delay time (hereinafter referred to as reference delay time) corresponding to the oil temperature, and a reference value for response speed (hereinafter referred to as reference response speed) as the oil temperature. The reference delay time determined from the oil temperature is corrected based on the comparison between the reference response speed storage means stored in correspondence with the reference temperature and the reference response speed determined from the oil temperature and the actual response speed measured by the response speed measurement means. 3. The valve timing control apparatus for an internal combustion engine according to claim 1, further comprising a correction means, wherein the corrected reference delay time is set as a final delay time.   The delay time setting means changes the setting of the delay time corresponding to the oil temperature and the response speed depending on whether the automatic transmission to which the internal combustion engine is connected is controlled to a shift range of a travel range or a non-travel range. The valve timing control device for an internal combustion engine according to any one of claims 1 to 3, wherein:   The delay time setting means changes the setting of the delay time corresponding to the oil temperature and the response speed according to the engine speed when the stop request is detected. The valve timing control device for an internal combustion engine according to claim 1. Compression ratio variable means for reducing the compression ratio of the internal combustion engine when the stop request is detected;
The valve timing control device for an internal combustion engine according to claim 1, further comprising:   The stop request is that an off signal of an ignition switch is detected, and the delay time is a time from when an off signal is detected until the ignition is actually turned off. The valve timing control device for an internal combustion engine according to any one of claims 6 to 6.

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