JP2019007442A - Internal Combustion Engine System - Google Patents

Abstract

To suppress a torque step which is formed at the changeover of drive cams.SOLUTION: This internal combustion engine system has a plurality of cylinders. Intake valves are arranged at a plurality of the cylinders, respectively, and two kinds of intake cams different in cam profiles are arranged in response to the respective intake valves. A throttle valve for adjusting suction air amounts introduced into an intake passage by being opened and closed is arranged in the intake passage of the internal combustion engine. The internal combustion engine system further comprises a changeover mechanism and a control device. The changeover mechanism switches drive cams for actually driving the intake valves between the two kinds of the intake cams. When switching the drive cams, the control device starts the control of the throttle valve to a direction in which a difference between the air amounts which are introduced into the cylinders become small before and after the changeover of the drive cams simultaneously with the valve-closing timing of the intake valves immediately before the changeover of the drive cams in the cylinder in which a stroke immediately before the changeover of the drive cams becomes an intake stroke.SELECTED DRAWING: Figure 1

Description

The present invention relates to an internal combustion engine system. More specifically, 2 different cam profiles
The present invention relates to an internal combustion engine system including a mechanism capable of switching a drive cam between different types of intake cams.

  Patent Document 1 discloses an output control device that includes two types of intake cams with different cam profiles and controls the output of an internal combustion engine that can switch between two types of intake cams to drive the intake valve. Yes. The output control device is configured to correct the throttle opening and the ignition timing when the cam is switched in order to suppress a torque step before and after the cam switching.

Japanese Patent Laid-Open No. 5-44558

  The output control device of Patent Document 1 controls the throttle opening simultaneously with the cam switching. However, there is a possibility that the torque step at the time of switching the cam cannot be sufficiently suppressed due to the response delay of the change in intake air amount.

  In order to solve the above-described problems, the present invention suppresses a torque step generated when a drive cam is switched in an internal combustion engine system capable of switching a drive cam that drives an intake valve between two types of intake cams. It is an object of the present invention to provide an internal combustion engine system improved so as to be able to do so.

  The internal combustion engine system of the present invention has a plurality of cylinders. An intake valve is disposed in each of the plurality of cylinders. Two types of intake cams having different cam profiles are arranged corresponding to each intake valve. In addition, a throttle valve that adjusts the amount of intake air introduced into the intake passage by opening and closing is disposed in the intake passage of the internal combustion engine.

  The internal combustion engine system further includes a switching mechanism and a control device. The switching mechanism switches the drive cam that actually drives the intake valve between the two types of intake cams. When switching the drive cam, the control device starts control of the throttle valve simultaneously with the closing timing of the intake valve immediately before switching of the drive cam in the cylinder in which the stroke immediately before switching of the drive cam becomes the intake stroke. It is configured. In this control, the throttle valve is controlled so that the difference in the amount of air introduced into the cylinder before and after the switching of the drive cam is reduced.

  According to the present invention, the control device starts the control of the throttle valve simultaneously with the closing timing of the intake valve immediately before the switching of the driving cam before the switching of the driving cam. Therefore, the control of the throttle valve can be started at an early stage within a range that does not affect the charging efficiency of the cylinder in the intake stroke immediately before switching. As a result, the delay in the change in the intake air amount when the drive cam is switched can be reduced, and the torque step at the time of switching the drive cam can be reduced.

It is a timing chart for demonstrating the outline | summary of the control in embodiment of this invention.

  The system in the present embodiment has an internal combustion engine. In the present embodiment, the internal combustion engine is a spark ignition type multi-cylinder engine (hereinafter simply referred to as an engine) having four cylinders, and the ignition sequence is No. 1 cylinder # 1, No. 3 cylinder # 3, No. 4 The order is cylinder # 4 and cylinder # 2. However, the number and arrangement of cylinders are not limited to this.

  An intake port and an exhaust port communicating with the combustion chamber of each cylinder are formed in the cylinder head of the engine. An intake valve is provided in the opening portion that communicates with the combustion chamber of the intake port, and an exhaust valve is provided in the opening portion that communicates with the combustion chamber of the exhaust port. The intake port communicates with the intake manifold, and the intake manifold communicates with the intake passage. A throttle valve for adjusting the amount of intake air introduced into the intake passage by opening and closing the intake passage is disposed. The exhaust port communicates with the exhaust manifold, and the exhaust manifold communicates with the exhaust passage.

  Two intake cams having different cam profiles are provided for each intake valve, and one of them drives the intake valve via a rocker arm. In the present embodiment, one of the two types of intake cams has a smaller working angle and lift amount than the other cam. Hereinafter, for convenience of explanation, a cam having a relatively small working angle and a small lift amount is also referred to as a “small cam”, and a cam having a relatively large working angle and a large lift amount is also referred to as a “large cam”.

  The two intake cams are provided adjacent to each other in the axial direction of the camshaft. A cam carrier is provided on the camshaft. By sliding the cam carrier, the cam facing the rocker arm (hereinafter also referred to as “drive cam”) is switched between the large cam and the small cam. Thus, the cam for driving the intake valve is switched. However, the configuration of the switching mechanism for switching the drive cam is not limited to this, and may be another configuration.

  The system according to the present embodiment includes an ECU as a control device. The ECU includes a RAM, a ROM, a CPU, and the like. The ECU captures and processes signals from various sensors mounted on the vehicle. The various sensors include a crank angle sensor that outputs a signal corresponding to the rotation angle of the crankshaft, a gap sensor that detects a drive cam, and the like. The ECU controls the throttle opening, the ignition timing, the switching of the drive cam, and the like by processing the signals of the various sensors taken in and operating the various actuators according to a predetermined control program.

  FIG. 1 is a timing chart for explaining an outline of control executed by the ECU in the present embodiment. The example of FIG. 1 shows an example in which the drive cam is switched from the small cam to the large cam. In FIG. 1, (a) is the stroke of each cylinder, (b) is the intake valve lift amount, (c) is the throttle opening, (d) is the intake manifold pressure, (e) is the charging efficiency, (f) is the ignition timing. Represents. Further, (c) throttle opening, (d) intake manifold pressure, (e) charging efficiency, (f) broken line in ignition timing shows the case of the conventional control as a comparative example, and the solid line shows the case of the control of the present embodiment. Show.

  In the present embodiment, the small cam is a cam with characteristics focusing on fuel consumption, and the large cam is a cam with characteristics focusing on output. The operating region of the internal combustion engine is divided into a region where a large cam is used and a region where a small cam is used.

  The ECU detects a drive cam switching request based on a current driving situation such as an accelerator operation amount. When the drive cam switching request is detected, the “first switching cylinder” and the “final switching cylinder” are specified. Here, the “first switching cylinder” is a cylinder in which the driving cam is switched first when the driving cam is switched, that is, a cylinder in which the intake valve is driven first after switching of the driving cam is started. The “final switching cylinder” is a cylinder in which the drive cam is switched last, that is, a cylinder in which a stroke immediately before the switching of the drive cam is an intake stroke. In the example of FIG. 1, the first switching cylinder is the first cylinder # 1, and the last switching cylinder is the second cylinder # 2. In addition, the ECU detects the valve timing of the intake valve, and detects the current valve closing timing IVC of the last switching cylinder (that is, immediately before switching the drive cam).

  Here, when the drive cam is switched between the large cam and the small cam, if the same throttle opening is maintained, the torque step before and after the switching becomes large. Therefore, at the time of switching the drive cam, the target throttle opening with the generated torque before and after the switching as an equal torque is calculated.

  As shown in FIG. 1C, in the present embodiment, the control for setting the throttle valve to the target throttle opening is started before the drive cam switching is started. Thus, the throttle opening is set to the target throttle opening early. More specifically, the closing of the throttle valve is started simultaneously with the closing timing IVC of the intake valve of the final switching cylinder.

  As shown in FIG. 1D, there is a delay in the response of the intake manifold pressure (hereinafter referred to as “in manifold pressure”) with respect to the closing of the throttle valve. In order to cancel the difference in generated torque before and after the drive cam switching due to this delay, the following control is further executed.

  First, the estimated value of the charging efficiency and the estimated value of the cylinder intake air amount are calculated from the current throttle opening considering the response of the intake manifold pressure. Based on the estimated value of the cylinder intake air amount, an estimated value of the expected generated torque is calculated. The expected generated torque is a torque generated when the ignition timing is MBT under the current operating conditions.

  When the estimated value of the expected generated torque is calculated, a torque increase with respect to the generated torque before switching the drive cam is calculated, and an ignition timing retardation amount for canceling the torque increase is calculated. The ignition timing is retarded according to the ignition timing retardation amount. Thereby, generation | occurrence | production of the torque level difference at the time of drive cam switching is suppressed.

  According to the control of the present embodiment, the throttle valve can be set to the target throttle opening earlier than in the conventional case by starting the control of the throttle opening before switching the drive cam. .

  The intake manifold pressure changes with a delay with respect to the control of the throttle valve. However, as shown in the intake manifold pressure in FIG. it can. Therefore, it is possible to more reliably prevent the occurrence of a torque step when the drive cam is switched.

  Further, since the response of the intake manifold pressure is made forward, an increase in the cylinder intake air amount can be suppressed as compared with the case of the conventional control as shown in the charging efficiency of FIG. . Therefore, the ignition timing retardation amount for canceling the increase in torque can be suppressed smaller than in the case of the conventional control, and the loss of fuel consumption at the time of switching the drive cam can be reduced.

  In the present embodiment, the case where the drive cam is switched from the small cam to the large cam has been described, but the same control is executed when the drive cam is switched from the large cam to the small cam. That is, before switching from the large cam to the small cam, the control for setting the throttle valve to the target throttle opening is started simultaneously with the closing timing IVC of the intake valve immediately before the drive cam switching in the final switching cylinder.

  However, the control start timing of the throttle valve is not limited to the intake valve closing timing IVC immediately before the drive cam switching in the last switching cylinder, and may be configured to start before the drive cam switching. However, if the throttle valve is closed before the closing timing IVC of the intake valve of the last switching cylinder immediately before the drive cam is switched, the charging efficiency may be reduced before the drive cam is switched. Therefore, it is desirable that the control of the throttle valve be started after the closing timing IVC of the intake valve of the last switching cylinder immediately before the drive cam is switched. Further, it is desirable that the control of the throttle valve be started at a timing earlier than the intake valve opening timing IVO and the intake TDC immediately after the drive cam switching of the first switching cylinder.

  In the above embodiment, when referring to the number of each element, quantity, quantity, range, etc., the reference is made unless otherwise specified or the number is clearly specified in principle. The invention is not limited to the numbers. Further, the structure and the like described in this embodiment are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

Claims (1)

A plurality of cylinders arranged in the internal combustion engine;
An intake valve disposed in each of the plurality of cylinders;
Two types of intake cams having different cam profiles arranged corresponding to the intake valves,
A switching mechanism for switching a drive cam that actually drives the intake valve between the two types of intake cams;
A throttle valve that is disposed in the intake passage of the internal combustion engine and adjusts the amount of intake air introduced into the intake passage by opening and closing;
When the drive cam is switched, in the cylinder in which the stroke immediately before the drive cam switching is the intake stroke, the intake valve closing timing immediately before the drive cam switching is the same as that in the cylinder before and after the drive cam switching. A control device configured to start control of the throttle valve in a direction in which the difference in the amount of air introduced into the
An internal combustion engine system comprising:

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