JP2009215936A - Control system for variable valve train - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent generation of torque shock at the time of mode change over in a variable valve train driving a camshaft with using an electric motor. <P>SOLUTION: ECU 22 controls drive of a first and a second electric motor 19, 21, and drives camshafts 12, 13 with using the first and the second electric motor 19, 21 respectively. In a regular rotation mode, the first and the second electric motor 19, 21 are continuously rotated in regular direction and an intake valve 11 is driven at the maximum lift. In rocking mode, the first and the second electric motor 19, 21 are rotated in regular and reverse direction to adjust lift of the intake valve 11. Change over between the regular rotation mode and the rocking mode is done by change over to the regular direction during regular rotation in a base circle section. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control system for a variable valve mechanism that drives a camshaft with an electric motor.

In a valve operating mechanism for an intake / exhaust valve of an internal combustion engine, generally, the power of a crankshaft is used to drive a camshaft. However, in recent years, a system has been proposed in which the camshaft is mechanically separated and independent from the crankshaft and the intake and exhaust valves are opened and closed by driving the camshaft using an electric motor. In such a valve mechanism using an electric motor, the operating angle of the valve can be made variable by swinging the rotation of the motor forward and backward (see Patent Document 1).
International Publication No. 2005/119019 Pamphlet

  However, when the electric motor is switched from the peristaltic mode to the normal rotation mode or from the normal rotation mode to the peristaltic mode, torque shock may occur, resulting in deterioration of controllability and combustion such as fuel consumption and emission. There is a fear.

  An object of the present invention is to prevent occurrence of torque shock at the time of mode switching in a variable valve mechanism that drives a camshaft using an electric motor.

  A control system for a variable valve mechanism according to the present invention is a control system for a variable valve mechanism that drives a camshaft by an electric motor, and is a normal rotation that drives the valve with a maximum lift amount by continuously rotating the electric motor in the normal direction. Mode switching between the mode and the peristaltic mode that adjusts the valve lift by rotating the electric motor forward and reverse is performed during the forward rotation in the base circle section, and the mode after switching is forward rotation. It is characterized by starting from.

  In order to respond to the mode switching request more quickly, the mode switching is preferably performed in the base circle section where the forward rotation operation is first performed after the mode switching request is generated.

  According to the present invention, in a variable valve mechanism that drives a camshaft using an electric motor, it is possible to prevent the occurrence of torque shock at the time of mode switching.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic perspective view showing the configuration of a control system for a variable valve drive mechanism using an electric motor according to an embodiment of the present invention. FIG. 1 shows only the configuration related to the intake valve, but the same applies to the exhaust valve, and the following description will be made by taking the intake valve as an example. In this embodiment, the case of four cylinders will be described as an example, but the number of cylinders is not limited to this.

  In the variable valve mechanism 10, each of the first cylinder # 1 to the fourth cylinder # 4 includes a pair of intake valves 11. The variable valve mechanism 10 is provided in, for example, the first camshaft 12 that drives the intake valves 11 provided in the first and fourth cylinders # 1 and # 4, and the second and third cylinders # 2 and # 3. A hollow second camshaft 13 for driving the intake valve 11 is provided. The first camshaft 12 penetrates through the hollow second camshaft 13 to form an integral structure, and is engaged with the intake valve 11 of the first cylinder # 1 on both sides of the second camshaft 13 respectively. And a pair of cams 15 that engage with the intake valve 11 of the fourth cylinder # 4. On the other hand, the second camshaft 13 includes a pair of cams 16 and a pair of cams 17 that respectively engage with the intake valves 11 of the second and third cylinders # 2 and # 3. That is, the cams 14 and 15 provided on the first camshaft 12 are integrally rotated, and independently of this, the cams 16 and 17 provided on the second camshaft 13 are integrally rotated.

  The rotation of the first camshaft 12 is driven and controlled by the electric motor 19 via the first gear train 18, and the rotation of the second camshaft 13 is driven and controlled by the electric motor 21 via the second gear train 20. The rotations of the first and second electric motors 19 and 21 are controlled by the ECU 22, and motor angle sensors are incorporated in the first and second electric motors 19 and 21, and the respective rotation angles are detected by the ECU 22. Is done. The ECU 22 is further connected with a first cam angle sensor 23 that detects the rotation angle of the first camshaft 12 and a second cam angle sensor 24 that detects the rotation angle of the second camshaft, and various sensors (not shown). Thus, for example, various well-known signals such as crankshaft angle, intake air amount and engine temperature are inputted and used for controlling the internal combustion engine.

  The cam 14 of the first cylinder # 1 provided on the first camshaft 12 and the cam 15 of the fourth cylinder # 4 are provided with a 180 ° phase shift, and are similarly provided on the second camshaft 13. The cam 16 of the second cylinder # 2 and the cam 17 of the third cylinder # 3 are provided with a 180 ° phase shift. Each of the cams 14 to 17 includes a zero lift part formed along the circumference of the camshaft where the lift of the intake valve 11 to be engaged becomes zero, and a projection part that projects from the circumference and lifts the intake valve 11. Is done. That is, in the first camshaft 12, the protrusions of the cams 14 and 15 protrude in the radial direction in opposite directions from the first camshaft 12, and in the second camshaft 13, the protrusions of the cams 16 and 17 are similarly formed. Project radially from the second camshaft 13 in opposite directions.

  FIG. 2 shows the arrangement of the cams 14 and 15 provided on the first camshaft 12. FIG. 2 is a diagram schematically showing the arrangement of the cams 14 and 15 when the first camshaft 12 is viewed in the axial direction. Since the same applies to the cams 16 and 17 of the second camshaft 13, only the first camshaft 12 will be described below, and the description regarding the second camshaft 13 will be omitted.

  As shown in FIG. 2, the cams 14 and 15 include protrusions 25 and 26 that protrude from the circumference of the first camshaft 12 and have symmetrical shapes, respectively. The protrusions 25 and 26 extend in the opposite directions in the radial direction of the first camshaft 12. The region occupied by the protrusions 25 and 26 along the circumferential direction of the first camshaft 12 is a lift section where the intake valve 11 is pushed out and lifted, and two lift sections formed by the protrusions 25 and 26. The section between is a base circle section where the zero lift portions of the cams 14 and 15 overlap. That is, in the base circle section, the intake valve 11 is not lifted in any of the first and fourth cylinders # 1 and # 4. 2 schematically shows the intake valve 11 being brought into contact with the cams 14 and 15 by a biasing member 27 such as a spring. In FIG. Is in contact with

  Next, with reference to FIGS. 3 and 4, the mode switching operation between the normal rotation / swing mode in the control system for the variable valve mechanism of the present embodiment will be described.

  In the present embodiment, the control system includes the ECU 22 and the first and second electric motors 19 and 21. In the normal rotation mode, the control system continuously rotates the first and second electric motors 19 and 21 to drive the intake valve 11 with the maximum lift amount. On the other hand, in the peristaltic mode, the first and second electric motors 19 and 21 are reversed before the lift amount of the intake valve 11 reaches the maximum, and are normally rotated within a range of less than 180 ° according to the required operating angle. , Repeated inversion and driven.

  FIG. 3 is a graph showing the relationship between the mode switching request signal from the peristaltic mode to the forward rotation mode and the cam angle in time series.

In the present embodiment, the mode switching is performed in a base circle section where there is no torque fluctuation. However, as shown in FIG. 3, if the request for switching from the peristaltic mode to the forward rotation mode is issued at time t ₀ after the base circle interval during forward rotation during the peristaltic mode operation, In the period between the time points t _{1 and} t ₂ ), a reversal operation is performed. For example, when switching to forward rotation only by being in the base circle during a fuel cut at the time of deceleration, the abrupt transition from reversal to normal rotation occurs. Switching occurs and a torque shock occurs, deteriorating controllability.

Therefore, in this embodiment, the mode after switching request is generated after the mode change request generated by the base circle section (this embodiment the forward operation, initially the base circle section (time t ₃ ~t ₄ as a forward operation Until the forward rotation mode is delayed until the base circle interval (between time points t _{3 and} t ₄ ) is switched to the normal rotation mode. By continuing (that is, the mode after switching starts with forward rotation), smooth switching is performed without generating a torque shock. In the example of FIG. 3, the rotation is switched to the forward rotation operation at the same time (time point t ₃ ) when entering the base circle interval in which the forward rotation operation is performed, but the base circle interval (from time t _{3 to} t _{4 in} the forward rotation operation) is switched. Switching may be performed at any point in time.

Note that a request for switching from the peristaltic mode to the forward rotation mode occurs during the reverse operation (including the base circle interval) or during the forward rotation operation outside the base circle interval between time points t _{2 and} t ₃ . Sometimes, the mode switching is delayed until the base circle section in which the forward rotation operation is performed (in this embodiment, the base circle section in which the forward rotation operation is first performed after the mode switching request is generated). On the other hand, if a request for switching from the peristaltic mode to the forward rotation mode occurs during the forward rotation operation in the base circle interval, the forward rotation operation may be immediately switched or the base circle interval ends. Switching may be performed until or at any time in the subsequent base circle interval.

  FIG. 4 is a graph showing, in time series, the relationship between the signal for requesting mode switching from the normal rotation mode to the peristaltic mode and the cam angle.

As shown in FIG. 4, the switching request from the forward mode to the swing mode, when emitted at time t ₅ outside the base circle section, mode switching the mode change request after the occurrence of the base circle section (time t ₆ ~ It performed in a section) between t ₇ (forward rotation), immediately after mode switching, swing mode is started from forward operation. In the switching from the normal rotation mode to the peristaltic mode, the base circle section immediately after the switching request always performs the normal rotation operation, so that it is possible to switch to the peristaltic mode in the immediately subsequent base circle section. In the example of FIG. 4, but has been switched to the rocking mode in the base circle section end time t7, by performing switching at any time as long as the base circle section (section between time t ₆ ~t ₇₎ Also good.

  FIG. 5 is a flowchart of the mode switching process between the normal rotation / swing mode. The mode switching process is executed in the ECU 22 when a switching request is issued.

  In step S100, it is determined whether or not the mode switching request is switching from the peristaltic mode to the normal rotation mode. If the mode switching request is switching from the peristaltic mode to the forward rotation mode, it is determined in step S102 whether or not the current cam angle is the base circle section. This is determined based on, for example, the values of the motor angle sensors provided in the first and second electric motors 19 and 21, or the values of the first and second cam angle sensors 23 and 24 (see FIG. 1). Is repeated until it is determined to be a base circle segment.

If it is determined in step S102 that it is a base circle section, it is determined in step S104 whether or not a forward rotation operation is being performed. If it is not a forward rotation operation, the process returns to step S102 and the same processing is repeated. On the other hand, if it is determined in step S104 that the forward rotation operation is being performed, switching to the forward rotation mode is executed in step S106 (time point t _{3 in} the example of FIG. ₃ ). The mode switching process between the peristaltic modes ends.

  On the other hand, when it is determined in step S100 that the mode switching request is not switching from the peristaltic mode to the normal rotation mode, the mode switching request is a switching from the normal rotation mode to the peristaltic mode, and the process proceeds to step S108. . In step S108, as in step S102, it is determined whether or not the current cam angle is the base circle section, and this determination is repeated until it is determined that the current cam angle is the base circle section.

If it is determined in step S108 that it is a base circle section, switching to the peristaltic mode in the forward direction (forward rotation direction) is executed in step S110 (time t _{7 in} the example of FIG. 4). The mode switching process between the normal rotation mode and the peristaltic mode ends.

  As described above, according to the present embodiment, when the mode is switched between the forward rotation mode and the peristaltic mode, the forward switching is always performed in the base circle section. It is possible to prevent a torque shock from being generated without being suddenly switched to. As a result, it is possible to prevent deterioration of controllability and deterioration of combustion such as fuel consumption and emission.

It is a typical perspective view which shows the structure of the control system of the variable valve mechanism which is one Embodiment of this invention. It is a figure which shows typically arrangement | positioning of the cam of a 1st cylinder, and the cam of a 2nd cylinder when a 1st camshaft is seen to an axial direction. It is a graph which shows the relationship between the signal of the mode switching request | requirement from peristaltic mode to normal rotation mode, and a cam angle in time series. It is a graph which shows the signal of the mode switching request | requirement from normal rotation mode to peristaltic mode, and the relationship of a cam angle in a time series. It is a flowchart of the mode switching process between normal rotation / peristaltic mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Variable valve mechanism 11 Intake valve 12 1st cam shaft 13 2nd cam shaft 14, 15 Cam 19, 21 Electric motor 22 ECU
24 Second cam angle sensor 25, 26 Protruding portion 27 Biasing member

Claims (2)

  A control system for a variable valve mechanism that drives a camshaft by an electric motor, wherein the electric motor is continuously rotated in the forward direction to drive the valve with a maximum lift amount, and the electric motor is rotated in the forward and reverse directions. The mode switching between the peristaltic mode for adjusting the lift amount of the valve is performed during the normal rotation in the base circle section, and the mode after the switching is started from the normal rotation operation. Control system for variable valve mechanism.   2. The control system for a variable valve mechanism according to claim 1, wherein the mode switching is performed in a base circle section in which a forward rotation operation is first performed after a mode switching request is generated.

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