JP2006070825A - Valve timing control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve timing control device of an internal combustion engine. <P>SOLUTION: As indicated in the figure 1, a crank angle is detected by a crank angle detecting means 32 just after cylinder internal pressure detected by a cylinder internal pressure detecting means 27 for detecting the cylinder internal pressure of an engine 1, exceeds the peak in a state of opening an intake valve 7a after the intake bottom dead center, and is set as the target intake valve closing timing TIVC. Operation of an intake valve closing timing adjusting mechanism 8a for adjusting the valve closing timing of the intake valve 7a, is controlled by a control means 31 so that the valve closing timing RIVC of the intake valve 7a becomes the target intake valve closing timing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a valve timing control device for an internal combustion engine, and more particularly to control of closing timing of an intake valve.

  Some internal combustion engines include a variable valve timing mechanism that moves the opening / closing timing of an intake valve to an advance side or a retard side. This variable valve timing mechanism is appropriately adjusted according to the operating state of the internal combustion engine so as to open and close the intake valve at a timing at which air is efficiently taken into the combustion chamber. For example, in Patent Document 1, the volume of the intake air is controlled by controlling the phase of the intake valve so that the differential pressure between the in-cylinder pressure at the intake bottom dead center and the in-cylinder pressure at a predetermined crank position during the compression stroke is maximized. Techniques for improving efficiency are disclosed.

Japanese Utility Model Publication 3-38422

Patent Document 1 focuses only on the differential pressure between the in-cylinder pressure at the intake bottom dead center and the in-cylinder pressure at a predetermined crank position during the compression stroke in order to improve volumetric efficiency. Cannot cope with this problem and cannot cope with the change in the amount of residual gas in the combustion chamber, and further improvement is desired.
An object of the present invention is to provide a valve timing control device for an internal combustion engine capable of efficiently improving the volumetric efficiency of intake air by synchronizing the intake pulsation and the closing timing of the intake valve. .

  In order to achieve the above object, an internal combustion engine valve timing control device according to the present invention includes an intake valve closing timing adjusting mechanism for adjusting an intake valve closing timing of an internal combustion engine, and an in-cylinder pressure for detecting an in-cylinder pressure of the internal combustion engine. A crank angle detecting means for detecting the crank angle of the engine; a crank immediately after the in-cylinder pressure detected by the in-cylinder pressure detecting means with the intake valve opened after the intake bottom dead center exceeds a peak; The crank angle detected by the angle detection means is set as the target intake valve closing timing, and the operation of the intake valve closing timing adjustment mechanism is controlled by the control means so that the intake valve closing timing becomes the target intake valve closing timing. Yes.

  The valve timing control apparatus for an internal combustion engine according to the present invention is characterized in that when the throttle opening is equal to or greater than a predetermined value, the control means executes a process for setting a target intake valve closing timing. For this reason, the target intake valve closing timing is set in the operating range where the intake pulsation with the throttle opening greater than or equal to the predetermined value is more likely to occur, so the target intake valve closing timing can be set appropriately and the volumetric efficiency of intake air is improved. The effect can be enhanced.

  In the valve timing control device for an internal combustion engine according to the present invention, when the in-cylinder pressure drops from a peak by a predetermined value, the control means sets the crank angle detected by the crank angle detection means to the crank immediately after the in-cylinder pressure exceeds the peak. It is characterized by being set as a corner. For this reason, the intake pulsation and the closing timing of the intake valve can be more easily synchronized.

  In the valve timing control device for an internal combustion engine according to the present invention, the control means determines the actual intake valve closing timing of the intake valve based on the detection output of the in-cylinder pressure detecting means, and this actual intake valve closing timing is determined as the target intake valve closing timing. It is characterized by controlling the operation of the intake valve closing timing adjustment mechanism so that the timing is reached. For this reason, since the actual intake valve closing timing of the intake valve can be accurately determined based on the detection output of the in-cylinder pressure detecting means, more accurate control can be realized.

  According to the present invention, the crank detected by the crank angle detecting means immediately after the in-cylinder pressure detected by the in-cylinder pressure detecting means exceeds the peak in a state where the intake valve of the internal combustion engine is opened after the intake bottom dead center. The angle is set as the target intake valve closing timing, and the operation of the intake valve closing timing adjustment mechanism that adjusts the intake valve closing timing so that the intake valve closing timing becomes the target intake valve closing timing is controlled. Since the in-cylinder pressure is highly correlated with the intake pipe internal pressure when the valve is opened, the intake valve is closed immediately after the in-cylinder pressure exceeds the peak after the intake bottom dead center is opened. Thus, intake pulsation and intake valve closing can be reliably synchronized, and the volumetric efficiency of intake air can be improved efficiently.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, reference numeral 1 denotes an engine which is an internal combustion engine. The engine 1 is configured as an intake pipe injection type engine, and a DOHC 4-valve type is adopted as the valve operating mechanism. A cylinder head 2 is mounted on an upper portion of a cylinder block 2a constituting the engine 1. The intake side valve mechanism 50 includes an intake valve 7a that opens and closes an intake port 11 formed in the cylinder head 2 so as to communicate with the combustion chamber 40, and an intake valve that abuts the upper end of the intake valve 7a via a rocker arm (not shown). The intake camshaft 21 is formed with a cam 3a, and a known valve spring that biases the intake valve 7a in the valve closing direction. The exhaust-side valve mechanism 51 includes an exhaust valve 7b that opens and closes an exhaust port 17 formed in the cylinder head 2 so as to communicate with the combustion chamber 40, and an exhaust that abuts the upper end of the exhaust valve 7b via a rocker arm (not shown). The exhaust camshaft 22 is formed with a cam 3b, and a known valve spring that biases the exhaust valve 7b in the valve closing direction.

  Timing pulleys 4a and 4b are mounted on the ends of the intake camshaft 21 and the exhaust camshaft 22, respectively. These timing pulleys 4 a and 4 b are connected to a crankshaft 6 via a timing belt 5. The timing pulleys 4 a and 4 b and the camshafts 21 and 22 are rotationally driven as the crankshaft 6 rotates, and the intake and exhaust valves 7 a and 7 b are opened and closed in synchronization with the rotation of the engine 1 by the camshafts 21 and 22. Driven.

  Between each camshaft 21 and the timing pulley 4a, a variable timing variable mechanism 8a (hereinafter referred to as “VVT8a”) as a variable timing mechanism on the intake side is provided. The structure of the VVT 8a is a so-called vane type variable timing mechanism, and an advance hydraulic chamber and a retard hydraulic chamber (not shown) that variably adjust the phase between the cam shaft 21 provided with the intake cam 3a and the timing pulley 4a. On the other hand, the hydraulic oil supplied from the oil pump 10 of the engine 1 is switched by an oil control valve (hereinafter referred to as “OCV”) 9a, thereby controlling the phase of the camshaft 21 relative to the crank angle to thereby control the intake valve 7a. It is set as the known structure which adjusts the opening-and-closing time of. In this embodiment, the VVT 8a constitutes an intake valve closing timing adjustment mechanism.

  A throttle valve 14 and an electromagnetic fuel injection valve 15 as fuel injection means are provided in the intake path 12 connected to the intake port 11. The throttle valve 14 is connected to an accelerator pedal 34 via a wire (not shown) or an electronic control mechanism, and its opening degree is adjusted according to the depression amount of the accelerator pedal 34.

  As the engine 1 is started, the intake air is introduced from the air cleaner 13 as the piston 16 descends up and down in FIG. 1 as the engine 1 starts, and the throttle valve 14 in the intake path 12 After the flow rate is adjusted in accordance with the opening, it is mixed with the fuel injected from the fuel injection valve 15 and flows into the cylinder 2A through the intake port 11 when the intake valve 7a is opened. The fuel injection valve 15 is set with a fuel injection amount corresponding to the operating state of the engine 1, and an injection signal is applied from the ECU 31 as a control means, thereby executing fuel injection at an optimal timing for combustion.

  The cylinder head 2 has an ignition plug 19 as an ignition means that faces the combustion chamber 40 and ignites in the combustion chamber 40, and an in-cylinder pressure sensor 27 as an in-cylinder pressure detection means that detects the in-cylinder pressure in the combustion chamber 40. Is provided. The spark plug 19 is ignited by applying an ignition signal controlled by the ECU 31.

  In the exhaust path 18 connected to the exhaust port 17, the exhaust gas after combustion in the combustion chamber 40 is guided from the exhaust port 17 as the piston 16 rises when the exhaust valve 7 b is opened, and the exhaust path 18 enters the exhaust path 18. It is discharged to the outside through the three-way catalyst 20 as a catalyst provided and a silencer (not shown).

  In the vehicle interior, an input / output device (not shown), a storage device (ROM, RAM, etc.) used for storing control programs, control maps, etc., a central processing unit (CPU), an ECU as a control means including a timer counter, etc. An engine control unit (hereinafter referred to as “ECU”) 31 is installed and performs overall control of the engine 1. On the input side of the ECU 31 are an in-cylinder pressure sensor 27, a cam angle sensor 28 that detects the rotation angle of the camshaft 21, a crank angle sensor 32 as a crank angle detection means that detects the crank angle of the crankshaft 6, and an engine load. Various sensors such as a throttle opening sensor 33 as load detecting means for detecting the opening of the throttle valve 14 and a timer (not shown) are connected. An OCV 9a, a fuel injection valve 15, a spark plug 19 and the like are connected to the output side of the ECU 31.

  In this embodiment, it is assumed that the crankshaft 6 rotates twice for a series of four strokes of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke in the engine 1, and the crank angle sensor 32 has a rate of 30 ° CA per pulse. The crank angle is detected. The ECU 31 determines the fuel injection amount and the like based on detection information from each sensor, and drives and controls the fuel injection valve 15. That is, the ECU 31 determines the fuel injection amount from the fuel injection valve 15 and the ignition timing for the spark plug 19 based on the crank angle signal from the crank angle sensor 32 and the load information from the throttle opening sensor 33. A map (not shown) is set, and the fuel injection amount and the ignition timing are appropriately controlled based on the map information.

  In the ROM (not shown) of the ECU 31, a predetermined value θ1 used when determining the throttle opening state and a predetermined pressure c used for determining a rate of decrease from the peak pressure of the in-cylinder pressure detected by the in-cylinder pressure sensor 27 are set. Yes. In this embodiment, θ1 is a fully open value of the throttle valve, and the predetermined value c is a value of about 1/3 from the peak pressure. In this embodiment, in order to more accurately detect the actual intake valve closing timing, a plurality of in-cylinder pressure detections are used, and two predetermined values for determining whether or not the in-cylinder pressure exceeds the peak pressure are used. Different predetermined pressures a and b are set in the ROM. The relationship between the two is a predetermined pressure a <a predetermined pressure b.

  The ECU 31 detects that the in-cylinder pressure detected by the in-cylinder pressure sensor 27 exceeds the peak pressure with the intake valve 7a opened after the intake bottom dead center (BDC) detected by the crank angle signal from the crank angle sensor 32. If it is determined immediately after that, the crank angle detected by the crank angle sensor 32 is set as the target intake valve closing timing TIVC, and the actual intake valve closing timing RIVC of the intake valve 7a becomes the target intake valve closing timing TIVC. Controls the operation of the OCV 9a. The ECU 31 includes a routine for executing a target intake valve closing timing setting process when the throttle opening is equal to or greater than a predetermined value θ1. The ECU 31 sets the crank angle detected by the crank angle sensor 32 when the in-cylinder pressure has decreased from the peak pressure by a predetermined value as the crank angle TIVC immediately after the in-cylinder pressure exceeds the peak pressure. The ECU 31 determines the actual intake valve closing timing RIVC of the intake valve 7a based on the detection output of the in-cylinder pressure sensor 27, and controls the operation of the OCV 9a so that the actual intake valve closing timing becomes the target intake valve closing timing TIVC.

  FIG. 2 is a diagram showing the characteristics of the opening / closing of the intake valve 7a and the intake pipe internal pressure and the cylinder internal pressure. In general, the in-cylinder pressure and the intake pipe internal pressure have a correlation while the intake valve 7a is open (IVO), and the in-cylinder pressure becomes a peak pressure just before the intake valve 7a is closed (IVC), and the crank pressure is slightly higher than this peak. It is known that closing the intake valve 7a when the angle advances leads to the highest volumetric efficiency of the intake air into the combustion chamber 40. However, since the detection signals from the cam angle sensor 28 and the crank angle sensor 32 may be misaligned due to errors or the like, in this embodiment, the parameter for controlling the valve closing timing of the intake valve 7a is determined based on fluctuations in the in-cylinder pressure. It is said.

  An example of the processing operation by the valve timing control device having such a configuration will be described with reference to the flowcharts shown in FIGS. The flowchart of FIG. 4 is for setting the target intake valve closing timing (TIVC) after the peak of the in-cylinder pressure among the processes executed by the ECU 31. This process is executed as an interrupt routine for each predetermined crank angle during operation of the engine 1.

  When the processing of FIG. 4 is started, it is determined from the crank angle of the crank angle sensor 32 whether the process of the engine 1 is within the range of the most retarded angle of the intake valve 7a from the intake bottom dead center (BDC) in step S1. The When the crank angle is within this range, the routine proceeds to step S2, where it is determined whether or not the throttle opening is a predetermined value θ1 (fully open), and when it is not within this range, this routine is terminated. If the throttle opening is fully open, the routine proceeds to step S3, where the sampling of the in-cylinder pressure and the peak value of the in-cylinder pressure are detected by jumping to the routine shown in FIG. Finish.

  In the routine shown in FIG. 5, it is determined from the crank angle from the crank angle sensor 32 whether or not the compression process is in step S40, and if it is not the compression process, the process proceeds to steps S41 and S42 to set the flag and the sampling number value N, respectively. The routine ends with 0 (zero). When it is a compression process, it progresses to step S43 and the state of a flag is determined. When the flag is set (FLAG = 1), this routine is finished and the process returns to step S4 in FIG. If the flag is not set in step S43, the process proceeds to step S44 to acquire the in-cylinder pressure data (P1) from the in-cylinder pressure sensor 27 and to enter the in-cylinder pressure peak value setting operation. In step S45, the number of samplings is added. In step S46, it is determined whether the number of samplings has reached a predetermined number. In this embodiment, the predetermined number of times is three. For this reason, the process proceeds to steps S51 and S52 until the predetermined number of times becomes three in step S46, and the sampled in-cylinder pressure data is replaced with the latest one.

  When the number of samplings reaches the predetermined number (three times) in step S46, the process proceeds to step S47, and the difference between the first predetermined pressure a and the first and second in-cylinder pressure data is determined. If the pressure does not exceed the first predetermined pressure a, it is determined that the peak pressure has not been detected yet, and the process proceeds to step S51 and step S52, and the in-cylinder pressure data from the in-cylinder pressure sensor 27 is updated to the latest data. To do. When the first predetermined pressure a is exceeded in step S47, the process proceeds to step S48, and the difference between the second predetermined value b and the second and third in-cylinder pressure data is determined. Then, if the pressure does not exceed the second predetermined pressure b, it is determined that the peak pressure has not been exceeded yet, the process proceeds to step S51 and step S52, and the cylinder pressure data from the cylinder pressure sensor 27 is updated. If the second predetermined pressure b is exceeded in step S48, it is determined that the in-cylinder pressure has decreased beyond the peak, and the routine proceeds to step S49 where the crank angle sensor 32 detects the in-cylinder pressure data P3. The angle is stored in the RAM as the actual intake valve closing timing (RIVC), and the process proceeds to step S50 where the flag is set to 1. And it memorize | stores as a peak value of in-cylinder pressure data P1, and returns to step S4 of FIG.

  In step S4, it is determined whether or not the in-cylinder pressure peak detection has been completed based on the flag state. If the flag is “1”, the process proceeds to step S5, and the in-cylinder pressure detection value is determined from the stored peak value by a predetermined value. It is determined whether or not it has decreased by c. If the in-cylinder pressure detection value has decreased from the peak value by a predetermined value c, the process proceeds to step S6. In step S6, the crank angle from the crank angle sensor 32 at the time of reduction is stored in the RAM as the target intake valve closing timing (TIVC).

  The routine shown in FIG. 3 is an interrupt process for each TDC. In this routine, the actual intake valve closing timing (RIVC) becomes the target intake valve closing timing (TIVC) set by the routine of FIG. In this way, the intake VVT is controlled by controlling the OCV 8a to control the phase of the intake cam.

  As described above, the cylinder pressure data detected by the cylinder pressure sensor 27 with the intake valve 7a opened after the intake bottom dead center (BDC) is detected by the crank angle sensor 32 immediately after the peak value exceeds the peak value. The crank angle is set as the target intake valve closing timing (TIVC), and the valve closing timing of the intake valve 7a is adjusted so that the actual intake valve closing timing (RIVC) of the intake valve 7a becomes the target intake valve closing timing (TIVC). Therefore, the intake valve 7a can be closed immediately after the in-cylinder pressure exceeds the peak value in a state where the intake valve 7a is opened after the intake bottom dead center (BDC), and the intake pulsation and the timing of closing the intake valve 7a are possible. Can be reliably synchronized as shown in FIG. 3, and the volumetric efficiency of intake air can be improved efficiently. Further, since the actual intake valve closing timing (RIVC) of the intake valve 7a is corrected by the target intake valve closing timing (TIVC), an accurate valve closing timing is achieved, and a GR device that is an exhaust gas recirculation device is provided. In the engine, the internal EGR amount and the pumping loss can be reduced to improve the fuel consumption, and the NOX can be reduced by securing an appropriate internal EGR amount.

  In the present embodiment, since the fully closed timing of the intake valve 7a is adjusted in an operation region where the intake pulsation is more likely to occur when the accelerator opening after the intake bottom dead center (BDC) is fully open, the target intake valve closing timing ( TIVC) can be set appropriately and the effect of improving the volumetric efficiency of intake air can be further enhanced.

  When the in-cylinder pressure drops from the peak value by a predetermined value c, the crank angle detected by the crank angle sensor is set as the crank angle immediately after the in-cylinder pressure exceeds the peak, so that the intake pulsation and the intake valve 7a are closed. Timing can be synchronized more easily. Further, the ECU 31 determines the actual intake valve closing timing (RIVC) of the intake valve 7a based on the detection output of the in-cylinder pressure sensor 27, and this actual intake valve closing timing (RIVC) is the target intake valve closing timing (TIVC). Since the operation of the VVT 8a is controlled so that the actual intake valve closing timing (RIVC) of the intake valve 7a can be accurately determined by the detection output of the in-cylinder pressure sensor 27, more accurate control can be realized.

  In this embodiment, the actual intake valve closing timing (RIVC) of the intake valve 7a is obtained from the in-cylinder pressure data. However, as shown in FIG. 6, the output signal difference w (from the cam angle sensor 28 and the crank angle sensor 32) You may obtain | require in ECU31 from an angle difference. Then, a difference between the actual intake valve closing timing (RIVC) obtained from the output signal difference w (angle difference) and the target intake valve closing timing (TIVC) obtained from the in-cylinder pressure data is obtained as a learning value, and this learning value is obtained. The OCV 9a of the VVT 8a may be controlled so that

  In the above embodiment, the peak value of the in-cylinder pressure and the actual intake valve closing timing (RIVC) at that time are obtained by using the routine shown in FIG. 5. However, if only the software is obtained in this way, the load on the CPU constituting the ECU 31 is increased. Is large and requires a high operating frequency, which may increase costs.

  Therefore, instead of the routine shown in FIG. 5, a mode in which the circuit 100 shown in FIG. 7 samples the in-cylinder pressure, detects the peak value of the in-cylinder pressure, and obtains the actual intake valve closing timing (RIVC) will be described. FIG. 7 is a circuit for obtaining the peak value and the actual intake valve closing timing (RIVC), and FIG. 8 is a timing chart of components used in the circuit 100 shown in FIG.

  In FIG. 7, a circuit 100 includes an AND circuit 101 to which a crank angle signal A from a crank angle sensor 32 and a compression process pulse B from a cam angle sensor 28 are input, and an output (pressure signal) from an in-cylinder pressure sensor 27. A / D conversion circuit 104 that receives and converts signal D that has been amplified by amplifier circuit 102 and noise-removed by low-pass filter 103, delays 105 and 106 that serve as delay circuits, and A / D conversion circuit 104 A difference circuit 107 between the signal E output from the delay hold 105 to the delay hold 106 and a signal F output from the delay hold 106 to the delay hold 106; a difference circuit 111 between the signal F and the signal G output from the delay hold 106; A comparator 108 that compares the signal H from the difference circuit 107 with a pressure increase reference value a as a set value; A comparator 113 that compares the signal I from the path 111 with the pressure increase reference value b as a set value, an AND circuit 110 to which the signals J and K output from the comparators 108 and 113 are input, and a crank angle signal A counter 114 that counts A, a sampling frequency signal M output from the town 114, and a latch circuit 115 that outputs the signal N to the ECU 31 using the signal L output from the AND circuit as a hold.

  A clock signal C is input to the A-D conversion circuit 104, the delay hold 105, and the delay hold 106, and each signal is output at a clock timing at which these signals are input. The comparator 108 outputs a signal J when the signal H is higher than the pressure increase reference value a, and the comparator 113 outputs a signal J when the signal I is higher than the pressure increase reference value b. The counter 114 and the latch 115 are configured to clear data when the compression process pulse A is input as a clear signal.

  According to the circuit thus configured, when the signal J from the comparator 108 and the signal K from the comparator 113 are input to the AND circuit 110, the signal L indicating that the in-cylinder pressure has exceeded the peak value is latched. 115, and the crank angle signal (signal indicating the actual intake valve opening timing) held in the counter 114 is output to the ECU 31, so that the load on the CPU of the ECU 31 can be reduced.

  In the above embodiment, the software and the circuit 100 have been described as separate forms, but may be a form in which both are provided at the same time. For example, the peak pressure of the in-cylinder pressure may be set using the flowchart of FIG. 5 when the engine speed is relatively low and using the circuit 100 when the engine speed is high.

It is a figure which shows the structure of the valve timing control apparatus of the internal combustion engine which shows one embodiment of this invention. It is a diagram which shows the opening / closing of an intake valve, a cylinder internal pressure, and the pressure change in an intake pipe. 6 is a flowchart for changing an actual intake valve closing timing to a target intake valve closing timing. It is a flowchart for calculating the target intake valve closing timing by the control means. 4 is a flowchart for deriving an actual intake valve closing timing and an in-cylinder pressure peak value. It is a timing chart of a crank angle sensor and a cam angle sensor. It is a block diagram which shows the structure of the circuit which functions as a control means. It is a timing chart of the signal of the circuit shown in FIG.

Explanation of symbols

1 Internal combustion engine 7a Intake valve 8a Intake valve closing timing adjustment mechanism 28 In-cylinder pressure detection means 32 Crank angle detection means TIVC Target intake valve closing timing RIVC closing timing (actual intake valve closing timing)
31,100 Control means

Claims (4)

  An intake valve closing timing adjusting mechanism for adjusting the closing timing of the intake valve of the internal combustion engine, an in-cylinder pressure detecting means for detecting an in-cylinder pressure of the internal combustion engine, a crank angle detecting means for detecting a crank angle of the internal combustion engine, The crank angle detected by the crank angle detecting means immediately after the in-cylinder pressure detected by the in-cylinder pressure detecting means exceeds the peak with the intake valve opened after the intake bottom dead center is determined as the target intake valve closing timing. And a control means for controlling the operation of the intake valve closing timing adjusting mechanism so that the valve closing timing of the intake valve becomes the target intake valve closing timing. Control device. The valve timing control device for an internal combustion engine according to claim 1,
The valve timing control device for an internal combustion engine, wherein the control means executes the target intake valve closing timing setting process when the throttle opening is equal to or greater than a predetermined value. The valve timing control device for an internal combustion engine according to claim 1,
The control means sets the crank angle detected by the crank angle detection means when the in-cylinder pressure drops from a peak by a predetermined value as a crank angle immediately after the in-cylinder pressure exceeds the peak. A valve timing control device for an internal combustion engine. The valve timing control device for an internal combustion engine according to claim 1,
The control means determines the actual intake valve closing timing of the intake valve based on the detection output of the in-cylinder pressure detecting means, and the intake valve closing timing so that the actual intake valve closing timing becomes the target intake valve closing timing. A valve timing control device for an internal combustion engine, which controls the operation of an adjustment mechanism.

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