JP5020220B2 - Device for controlling the throttle valve when the internal combustion engine is stopped - Google Patents

Description

  The present invention relates to an apparatus for controlling a throttle valve when an internal combustion engine is stopped.

  In an internal combustion engine such as a diesel engine or a gasoline engine, even if combustion stops in the combustion chamber, the piston reciprocates several tens of times until the inertia of the piston is consumed by friction, causing the engine to vibrate. In order to reduce this vibration, the throttle valve on the intake passage is completely closed when the engine is stopped. However, if the throttle valve is completely closed and the intake passage is closed, the pressure in the intake passage becomes a large negative pressure due to the reciprocating motion of the piston that continues for a while after the combustion is stopped. In such a situation, the piston to be stopped cannot resist the inertial energy of the reciprocating motion due to the inertia of the piston as a result of the reduction of the air amount in the cylinder during the compression stroke. For this reason, the piston which performs inertial movement becomes easy to stop near the top dead center.

  Patent Document 1 describes that when the piston is stopped near the top dead center, the crank arm and the crank rod are in series, and the torque required to move the piston is large, so the engine startability is poor. Has been. For this reason, Patent Document 1 proposes that when the engine speed due to inertia falls below a preset value when the engine is stopped, the throttle valve is slightly opened to reduce the negative pressure in the intake passage.

  Patent Document 2 describes that the opening degree of the throttle valve is controlled more finely in order to reduce engine vibration when the engine is stopped.

In recent years, in order to improve the output and fuel consumption of an internal combustion engine, a valve overlap in which the open state of the intake valve and the open state of the exhaust valve partially overlap each other has been adopted. In particular, a valve overlap state frequently occurs in a variable valve mechanism (Variable Valve Timing and Lift Control System) that changes the opening / closing timing or lift amount of an intake valve or an exhaust valve. One example can be seen in Patent Document 3.
JP 2000-213375 A JP 2005-320909 A JP 2007-182760 A

  In an engine using valve overlap, if the piston of one cylinder stops near top dead center, at least one other cylinder may stop in a valve overlap state where both the intake and exhaust valves are open. is there. In this state, the exhaust system gas flows back into the intake pipe. If the engine is started in this state, exhaust gas is mixed in the intake air and the amount of oxygen is insufficient, so that the combustion becomes weak and the startability of the engine deteriorates.

  In order to avoid the piston from stopping near the top dead center, when opening the throttle valve and introducing air, the hardware has product variations, compared to the valve opening timing commanded by the electronic control unit (ECU). Since there are variations due to aging, etc., the timing at which the throttle valve actually opens varies.

  Therefore, a technique for operating the throttle valve at an appropriate timing in response to a command from the ECU is required.

  An apparatus for controlling a throttle valve when an internal combustion engine is stopped according to the present invention includes a throttle valve for controlling an intake air amount of the internal combustion engine, an actuator for driving the throttle valve, and an opening for detecting the opening of the throttle valve. A degree sensor, a rotational speed sensor that detects the rotational speed of the internal combustion engine, and an electronic control unit that controls the internal combustion engine. The electronic control unit calculates a delay time from a time when the command to open the throttle valve is sent to a time when the opening sensor detects that the throttle valve is opened, and the calculated delay time. In the memory and updating as a delay set value, and when the stop command for the internal combustion engine is issued, the rotational speed sensor is configured to open the throttle valve at a preset rotational speed of the internal combustion engine. Means for sending a command to open the throttle valve to the actuator in response to the rotational speed of the internal combustion engine detected at a predetermined value or less, and referring to the delay setting value stored in a memory. Means for correcting the predetermined value.

  With such a configuration, it is possible to operate a throttle valve having a variation in opening timing with an appropriate timing in response to a command from the ECU.

  Further, the updating means may be configured to replace the delay set value with the calculated delay time.

  Further, the updating means may be configured to replace the delay setting value with the calculated delay time when a difference between the calculated delay time and the delay setting value is larger than a predetermined value. .

  Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an overall configuration of an apparatus for controlling a throttle valve when the internal combustion engine is stopped. The engine 10 is, for example, a 4-cylinder automobile engine.

  A throttle valve 14 is disposed in the intake pipe 12. The throttle valve 14 is driven by an actuator 18 in response to a control signal from an electronic control unit (ECU) 60. The ECU 60 sends a control signal for controlling the opening of the throttle valve 14 to the actuator 18 in accordance with an output from an accelerator pedal opening sensor (not shown). This method is called a drive-by-wire method, and other methods include a method in which the wire 16 is connected to an accelerator pedal and the throttle valve is directly controlled by the accelerator pedal. A throttle valve opening sensor 20 is provided near the throttle valve 14 and outputs a signal corresponding to the throttle opening θTH.

  A fuel injection valve 24 is provided for each cylinder between the throttle valve 14 and the intake valve of the engine 10. The fuel injection valve 24 is connected to a fuel pump (not shown) and receives fuel from a fuel tank (not shown) via the fuel pump. The fuel injection valve 24 is driven according to a control signal from the ECU 60.

  An intake pipe pressure sensor 32 and an intake temperature sensor 34 are provided downstream of the throttle valve 14 in the intake pipe 12 and output electrical signals indicating the intake pipe absolute pressure PB and the intake temperature TA, respectively.

  A cylinder discrimination sensor (CYL) 40 is provided in the vicinity of the camshaft or crankshaft of the engine 10 and outputs, for example, a cylinder discrimination signal CYL at a predetermined crank angle position of the first cylinder. Further, a TDC sensor 42 and a crank angle sensor (CRK) 44 are provided, and the former outputs a TDC signal at a predetermined crank angle position related to the piston top dead center (TDC) position of each cylinder. The CRK signal is output at a crank angle (for example, 30 degrees) having a shorter cycle than the TDC signal.

  An exhaust pipe 46 is connected to the engine 10. The exhaust gas generated by the combustion is purified by the catalyst device 50 and discharged to the outside. A wide area air-fuel ratio (LAF) sensor 52 is provided upstream of the catalyst device 50 and outputs a signal proportional to the oxygen concentration in the exhaust gas in a wide range from lean to rich.

  A vehicle speed sensor 54 is disposed in the vicinity of the drive shaft that drives the wheels of the automobile, and outputs a signal every predetermined rotation of the drive shaft. The ignition switch 55 is arranged at the driver's seat, starts and stops the engine, and outputs an ON or OFF signal. The vehicle is provided with an atmospheric pressure sensor 56 and outputs a signal corresponding to the atmospheric pressure.

  Outputs of these sensors are sent to an ECU (electronic control unit) 60. The ECU 60 is constituted by a microcomputer, and includes a processor CPU 60a that performs calculations, a ROM 60b that stores lists, tables, and maps of control programs and various data, and a RAM 60c that temporarily stores calculation results by the CPU 60a. The ECU 60 includes a non-volatile memory, and stores data necessary for engine control in the next operation cycle in the non-volatile memory. The nonvolatile memory can be composed of an EEPROM, which is a rewritable ROM, or a RAM with a backup function that retains memory by supplying a holding current even when the vehicle is powered off.

  Outputs of various sensors are input to an input interface 60d of the ECU 60. The input interface 60d includes a circuit that shapes an input signal and corrects a voltage level, and an A / D converter that converts an analog signal into a digital signal.

  The CPU 60a counts the CRK signal from the crank angle sensor 44 with a counter to detect the engine speed NE, and also counts the signal from the vehicle speed sensor 54 to detect the running speed VP of the vehicle. The CPU 60a performs calculation according to a program stored in the ROM 60b, and sends a drive signal to the fuel injection valve 24, the actuator 18 of the throttle valve 14 and the like via the output interface 60e.

  FIG. 2 is a control flow of an engine stop control process according to an embodiment of the present invention. This process is executed by the CPU 60a of the ECU 60. In the present embodiment, the case where the ignition switch 55 is turned off will be described as an example. However, the engine stop command is not limited to the ignition off, and the engine may be automatically stopped during idling. It goes without saying that the present invention can also be applied to such an automatic engine stop.

  When the ignition switch 55 is turned off, the ECU 60 starts the engine stop control process in response to the input of the OFF signal accompanying the turning off of the ignition switch 55 (step S101: YES). If the ignition switch 55 is ON, the process is terminated (step S101: NO).

  In step S102, the ECU 60 detects the cylinder discrimination signal CYL via the input interface 60d, counts the CRK signal from the crank angle sensor 44 in a specific cylinder with a counter, and detects the engine speed NE to detect the engine. The rotational speed NE is compared with a predetermined value Nc.

  Here, the predetermined value Nc is an initial threshold value for determining whether the throttle valve 14 is closed or opened. When the ignition switch 55 is turned off, the engine speed NE gradually decreases. However, since the piston reciprocates due to inertia even after the combustion is stopped, the reciprocating motion vibrates the engine. Therefore, as described in Patent Document 1, if the throttle valve 14 is closed, the supply of intake air is stopped, and the vibration characteristics when the engine is stopped can be improved. The ECU 60 sends a signal to the actuator 18 to perform the valve closing control of the throttle valve 14 until the engine speed NE drops from the engine speed immediately after the ignition switch 55 is turned off to a predetermined value Nc (step S102: YES). (Step S103).

  In step S102, when the engine speed NE is smaller than the predetermined value Nc, the process proceeds to a process for determining whether or not to perform the valve opening control of the throttle valve 14.

  Before describing the process in detail, an example of a determination method will be described with reference to FIGS. FIG. 3 is a diagram for explaining the behavior of the exhaust valve and the intake valve, and FIG. 4 is a diagram for explaining the engine speed NE, the command of the ECU 60, and the opening / closing behavior of the throttle valve 14.

  A period in which the exhaust valve and the intake valve are simultaneously opened near the piston top dead center (TDC) shown in FIG. 3 is referred to as valve overlap. The valve overlap is set to capture as much air-fuel mixture as possible to improve engine output. In order to improve engine startability, it is necessary to avoid that the piston stops near the top dead center so that valve overlap does not occur when the engine is stopped. In order to avoid this, the work of the piston, the friction of the engine, the inertia of the engine, and the like are taken into consideration. However, as described in Patent Document 1, the throttle valve 14 is set to an actual engine speed NE. By performing valve opening control at a preset rotation speed Nk, it is possible to increase the pressure in the intake pipe 12 and prevent the piston from stopping near the top dead center.

  However, since there are variations in hardware, variability due to aging, etc., when the throttle valve 14 is opened and air is introduced, the actual opening timing of the throttle valve relative to the opening timing commanded by the ECU 60 Cause variations. For this reason, the piston may stop near the top dead center.

  Referring to FIG. 4, when the ignition switch 55 is turned off, the ECU 60 sends a signal to the actuator 18 to close the throttle valve 14. The engine speed NE indicated by the two-dot chain line gradually decreases. When the engine speed NE reaches a predetermined value Np, the ECU 60 sends a drive signal of a control command ECUCMD for opening the throttle valve 14 to the actuator 18 via the output interface 60e. The predetermined value Np is a value set from the beginning, and when the engine rotational speed NE reaches the predetermined value Np, a control command for opening the throttle valve 18 is output, whereby the actual engine rotational speed NE is output. Can open the throttle valve 14 at a preset rotation speed Nk. The predetermined value Np is set in consideration of the time required for hardware operation for standard valve opening, and can be set at the time of factory shipment, for example.

  That is, the actuator 18 drives the throttle valve 14, but first it is necessary to operate the hardware after receiving a signal from the ECU 60, which is seen in the behavior of the throttle valve opening θthp shown by the solid line in FIG. As described above, a certain delay CRDP occurs from when the drive signal is transmitted to when it actually operates. As shown in FIG. 4, the CRDP and CRDA described later represent the time until the throttle valve 14 starts to open after a command for driving the throttle valve 14 in the opening direction is output from the ECU 60.

  This delayed CRDP may be different for each vehicle (engine) due to variations in communication delay and variations in hardware itself. A broken line in FIG. 4 indicates a change in the throttle valve opening θtha detected in a certain engine when a drive signal of a control command ECUCMD for opening the throttle valve 14 is received from the ECU 60. The delay CRDA actually detected in a certain engine indicated by the broken line θtha is further delayed by the difference DCRD with respect to the line with the delay CRDP indicated by the solid line θthp which is the set value of the product. For this reason, deviation occurs from the preset engine speed condition Nk (ΔNE in FIG. 4), and as a result, the piston stop position may not be the intended location.

  Therefore, in the present embodiment, a delay CRDA in a certain engine indicated by a broken line is detected by the throttle valve opening sensor 20. Then, the difference between this delay CRDA and the delay CRDP of the set value of the product is taken, and as shown by the one-dot chain line in FIG. 4, the black arrow indicates the timing at which the ECU 60 sends the drive signal of the control command ECUCMD to the actuator 18 The angle is advanced in the direction. The engine rotational speed NE that shifts to the opening control of the throttle valve 14 by the correction for advancement is a new predetermined value Nd that is corrected to advance by a difference DCRD from the predetermined value Np that is an initial set value. Is done. In this way, the predetermined value is corrected with reference to the difference DCRD that is the delay setting value stored in the memory. With this correction, as indicated by the white arrow in FIG. 4, the change in the throttle valve opening θtha in a certain engine indicated by the broken line θtha coincides with the solid line θthp, and the engine speed NE when the throttle valve 14 is actually opened is shown. Can be eliminated.

  Returning to the process flow of FIG. 2 again, when the engine speed NE is smaller than the predetermined value Nc (step S102: NO), the ECU 60 is a threshold value for determining whether or not to perform throttle valve opening control. The rotational speed Nd is calculated (step S104).

  In step S104, the ECU 60 refers to the difference DCRD between CRDA and CRDP stored in the memory (step S105), and refers to a map or the like stored in the memory of the ECU 60 to calculate the rotation speed Nd as a threshold value. . In this map, for example, as shown in step S1041 in FIG. 2, the difference DCRD is set on the horizontal axis, and the engine speed NE is set on the vertical axis. Here, the difference DCRD is a difference of (CRDA−CRDP), and the arrow direction on the horizontal axis in FIG. 2 indicates a positive (+) value, and the reverse direction indicates a negative (−) value.

  As the difference DCRD increases with a positive (+) value, the predetermined value Nd increases compared to Np, while as the difference DCRD increases in the negative (-) direction, the predetermined value Nd compares with Np. Become smaller. That is, in this map, the case where the throttle valve 14 is operated with a delay with respect to 0 is taken as the right arrow direction, and the left direction shows the case where the response of the throttle valve 14 is earlier than the set value. This is because there are two cases where the operation of the throttle valve 14 is delayed and when the operation is accelerated.

  When a difference DCRD, which is a set value of variation, is calculated, a new predetermined value Nd is calculated by the map and used as a threshold value. Note that since the delayed CRDA is not detected when the first process is executed, Nd is set to Np, which is an initial set value.

  In step S106, the ECU 60 compares the engine speed NE with Nd. If the engine speed NE is greater than Nd (step S106: NO), the ECU 60 sends a signal to the actuator 18 to continue the closing control of the throttle valve 14 (step S103). If the engine speed NE is smaller than Nd (step S106: YES), the ECU 60 sends a signal to the actuator 18 to execute the opening control of the throttle valve 14 (step S107).

  In step S108, the ECU 60 obtains a signal corresponding to the throttle opening θTH by the throttle valve opening sensor 20 provided near the throttle valve 14. Then, ECU 60 calculates a delay CRDA from the drive signal of control command ECUCMD and the signal of throttle opening θTH.

  In step S109, the ECU 60 calculates a difference DCRD between the delay CRDP and the calculated delay CRDA when the throttle valve opening control is executed at the set value Np, stores it in the memory, and ends the process. The delayed CRDA calculated at this time is also stored in the memory, and this CRDA is used as the previous value CRDP in the next process.

  The calculation of CRDA and DCRD described in steps S108 and 109 is preferably executed in conjunction with the control using these calculation results (steps S106 and 107). However, CRDA and DCRD may be calculated during drive control of the throttle valve 14 during normal operation.

  With this configuration, the present embodiment can operate the throttle valve at an appropriate timing in response to a command from the ECU. When the throttle valve is opened and air is introduced, the piston is dead even when there is a variation in the product or variation due to aging with respect to the valve opening timing commanded by the electronic control unit (ECU). You can avoid stopping near the point.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and can be modified and used without departing from the spirit of the present invention.

It is a block diagram which shows the whole structure of the idle speed control apparatus of an internal combustion engine. 5 is a control flow of an engine stop control process according to an embodiment of the present invention. It is a figure for demonstrating the behavior of an exhaust valve and an intake valve. It is a figure for demonstrating the engine speed NE, ECU instruction | command, and the opening / closing behavior of a throttle valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine 12 Intake pipe 14 Throttle valve 18 Actuator 20 Throttle opening sensor 60 ECU

Claims (3)

A throttle valve for controlling the intake air amount of the internal combustion engine;
An actuator for driving the throttle valve;
An opening sensor for detecting the opening of the throttle valve;
A rotational speed sensor for detecting the rotational speed of the internal combustion engine;
An electronic control unit for controlling the internal combustion engine,
The electronic control device
Delay time from the time when the command for opening the throttle valve is sent during the stop operation of the internal combustion engine or during normal operation other than the stop operation to the time when the opening sensor detects that the throttle valve is open Means for calculating
Means for storing the calculated delay time in a memory and updating it as a delay setting value;
When the internal combustion engine is instructed to stop, the rotational speed of the internal combustion engine detected by the rotational speed sensor is less than or equal to a predetermined value so that the throttle valve is opened at a preset rotational speed of the internal combustion engine. And means for sending a command to the actuator to open the throttle valve in order to control the stop position of the piston ,
Means for correcting the predetermined value with reference to the updated delay setting value stored in a memory;
An apparatus for controlling a throttle valve when the internal combustion engine is stopped. The apparatus according to claim 1, wherein the updating unit replaces the delay setting value with the calculated delay time. The apparatus according to claim 2, wherein the updating means replaces the delay setting value with the calculated delay time when a difference between the calculated delay time and the delay setting value is larger than a predetermined value. .

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