JP4544024B2 - Multi-cylinder engine fuel supply system - Google Patents

Description

  The present invention relates to a fuel supply device for a multi-cylinder engine, and more particularly, to a fuel injection valve that supplies fuel discharged from a high-pressure fuel pump driven by the engine.

An actuator such as a cam driven by a crankshaft, a high-pressure fuel pump for discharging high-pressure fuel driven by the actuator, and a high-pressure fuel pump opened for a predetermined fuel injection pulse width at a predetermined fuel injection timing There is a fuel supply device for an engine provided with a fuel injection valve for supplying high-pressure fuel from the engine to the engine (see Patent Document 1).
JP 2000-320385 A

  By the way, in the technique of the said patent document 1, since the pressure of the fuel discharged | emitted from a high pressure fuel pump can be set arbitrarily by using a high pressure fuel pump, based on the fuel pressure and required fuel amount, it is set as a fuel injection valve. The fuel injection pulse width to be given is calculated.

  However, since the fuel injection valve cannot avoid variations in the injection amount due to unstable valve behavior of the fuel injection valve, variations in the injection amount increase under operating conditions where the fuel injection pulse width given to the fuel injection valve is small. As a result, the air-fuel ratio cannot be controlled to the target value, and the combustion stability deteriorates.

  Referring to FIG. 10, the horizontal axis represents the fuel injection pulse width given to the fuel injection valve, and the vertical axis represents the fuel amount. The fuel amount until the fuel injection pulse width reaches a predetermined value A. Is zero. This indicates that even if a fuel injection pulse width less than the predetermined value A is given to the fuel injection valve, the fuel injection valve cannot be opened. As can be seen from the fact that the characteristics of the fuel injection pulse width are undulating in the section where the fuel injection pulse width is larger than the predetermined value A, the injection amount variation is large in this AB section. Therefore, the required fuel amount cannot be accurately supplied to the engine under the operating conditions in which the AB section is used.

  Therefore, the present invention provides that the fuel injection pulse width actually applied to the fuel injection valve is the minimum injection per cylinder even when the calculated value of the fuel injection pulse width applied to the fuel injection valve is less than the minimum injection pulse width per cylinder. An object of the present invention is to provide an apparatus for preventing the pulse width from being less than the pulse width.

The present invention includes a high-pressure fuel pump that is driven by an actuator and discharges high-pressure fuel;
In a fuel supply device for a multi-cylinder engine, which is opened for a predetermined fuel injection pulse width at a predetermined fuel injection timing and supplies high-pressure fuel from the high-pressure fuel pump to the engine, the fuel is supplied to the fuel injection valve The fuel injection pulse width is calculated, and when the calculated fuel injection pulse width is less than the minimum injection pulse width per cylinder, fuel injection of some cylinders is stopped, and the calculated fuel injection pulse width is 1 The fuel injection pulse width of the injection cylinder is increased when it is less than the minimum injection pulse width per cylinder. The minimum injection pulse width per cylinder is increased as the pressure of fuel discharged from the high-pressure fuel pump increases.

  According to the present invention, the fuel injection pulse width given to the fuel injection valve is calculated, and when the calculated fuel injection pulse width is less than the minimum injection pulse width per cylinder, the fuel injection of some cylinders is stopped. Since the fuel injection pulse width of the injection cylinder is increased, the fuel injection pulse width that is actually applied to the fuel injection valve will not be less than the minimum injection pulse width per cylinder. Even when it becomes less than the minimum injection pulse width per cylinder, it becomes possible to stabilize the valve operation of the fuel injection valve provided in the injection cylinder, and the combustion stability in the injection cylinder is improved.

  1 is a schematic configuration diagram of an engine fuel supply apparatus according to an embodiment of the present invention, FIG. 2 is a plan view of a pump drive cam 12 (plate cam) as an actuator driven by a crankshaft, and FIG. 3 is a high-pressure fuel pump. 11 is a waveform diagram for illustrating the action of No. 11. FIG.

  In FIG. 1, the fuel supply device of the engine mainly includes a fuel tank 1, a feed pump 2, a high-pressure fuel pump 11, a common rail (fuel gallery) 21, and a fuel injection valve.

  The feed pump 2 is driven by the electric motor 3 and pumps the fuel in the fuel tank 1 to the fuel supply passage 8. Fuel filters 4 and 5 are provided on the upstream side and the downstream side of the feed pump 2, respectively. In order to prevent the discharge pressure of the feed pump 2 from exceeding a certain pressure, a low-pressure pressure regulator 6 is provided in a return passage 9 that branches from the fuel supply passage 8 and returns to the fuel tank 1.

  The fuel discharged from the feed pump 2 is supplied to the high-pressure fuel pump 11 via the fuel supply passage 8. The fuel supply passage 8 is provided with a damper 10 for suppressing fuel pressure pulsation.

  The configuration (not known) of the high-pressure fuel pump 11 will be described. The high-pressure fuel pump 11 includes a pump drive cam 12 (plate cam) as an actuator driven by a crankshaft, and a plunger pump 14 driven by the pump drive cam 12. And a normally closed suction check valve 15, a normally closed discharge check valve 16, and a control solenoid 17. The plunger pump 14 further includes a cylinder 14a, a plunger 14b that is driven by the peripheral surface of the pump drive cam 12 and reciprocated in the vertical direction in the figure, and a high-pressure chamber defined by the plunger 14b and the cylinder 14a. 14c, a spring 14d for urging the plunger 14b toward the peripheral surface of the cam 12, and a spill passage 18 for returning the fuel in the high pressure chamber 14c to the fuel tank 1.

  As shown in FIG. 2, the pump drive cam 12 has lift portions that rise from the base circle at left and right opposing positions that are 180 degrees apart, and the pump drive cam 12 rotates clockwise in FIG. As a result, the spring 14d biases the plunger 14b in the direction of the cam 12 when descending from the left or right maximum lift position shown in FIG. 2 to the base circle, so that the plunger 14b moves downward in FIG. . Further, when the pump drive cam 12 rotates and this time rises away from the base circle toward another maximum lift position 180 degrees away, the plunger 14b resists the biasing force of the spring 14d in FIG. Move upward.

  FIG. 3 shows the operation of the high-pressure fuel pump 11 as a model. Now, when the suction check valve 15 is opened at the timing t1 when the plunger 14b is at the highest lift position, and when the plunger 14b is lowered from the highest lift position to the timing t2 when the lowest lift position is reached, the feed pump 2 is supplied to the high pressure chamber 14c. Of low pressure fuel. That is, the section from t1 to t2 is the intake stroke of the high-pressure fuel pump 11.

  The plunger 14b rises toward the maximum lift position from t2, but at this time, since the control solenoid 17 opens the spill passage 18, the fuel in the high pressure chamber 14c is returned to the fuel tank 1 through the spill passage 18. However, the fuel in the high-pressure chamber 14 c is not pumped to the common rail 21.

  When the plunger 14b rises and the control solenoid 17 closes the spill passage 18 at the timing t3, the fuel pressure in the high-pressure chamber 14c is increased during the period from the timing t3 to the timing t4 when the plunger 14b reaches the maximum lift position. Ascending, the discharge check valve 16 is opened, and high-pressure fuel is supplied to the common rail 21 through the orifice 19. That is, the section from t2 to t3 is the spill stroke of the high-pressure fuel pump 11, and the section from t3 to t4 is the discharge stroke of the high-pressure fuel pump 11. A series of operations in a section from t1 to t4 is a group, and after the timing of t4, this group of operations is repeated.

  As the timing at which the control solenoid 17 closes the spill passage 18 (timing at t3) is advanced, the discharge amount of the high pressure fuel pump 11 increases, and conversely, as the timing at which the control solenoid 17 closes the spill passage 18 is delayed, the high pressure fuel pump 11 increases. The discharge amount of the high-pressure fuel pump 11 can be controlled by controlling the timing at which the control solenoid 17 closes the spill passage 18 to the advance side or the retard side.

  Returning to FIG. 1, the pump drive cam 12 is provided integrally with the intake valve camshaft 13. The cam sprocket fixed to the front end of the intake valve camshaft 13 and the front end of a crankshaft (not shown). A chain or belt is wound around a fixed crank sprocket, and the intake valve camshaft 13 is indirectly driven by the crankshaft.

  A safety valve 22 is provided at the rear end of the common rail 21. When the actual common rail fuel pressure exceeds the allowable pressure, the safety valve 22 is opened and a part of the high-pressure fuel in the common rail 21 is returned to the fuel tank 1.

  The high-pressure fuel stored in the common rail 21 is distributed to the high-pressure fuel injection valve of each cylinder. FIG. 1 shows a case of a four-cylinder engine, and high-pressure fuel stored in the common rail 21 acts on the four high-pressure fuel injection valves 31A, 31B, 31C, and 31D.

  When the fuel injection valves 31A to 31D are opened at a predetermined timing according to the ignition timing of each cylinder, fuel is supplied to the combustion chamber of the cylinder having the opened fuel injection valve. Further, the common rail fuel pressure is reduced by the disappearance of a predetermined amount of fuel from the fuel injection valve.

  For this reason, the engine controller 41 has in advance a target fuel pressure of the common rail 21 corresponding to the engine load and the rotational speed as a map, and the actual common rail fuel pressure detected by the fuel pressure sensor 42 is the engine pressure at that time. The discharge amount of the high-pressure fuel pump 11 is controlled via the control solenoid 17 so as to coincide with the target fuel pressure corresponding to the load and the rotational speed. For example, when the actual common rail fuel pressure is lower than the target fuel pressure, the timing at which the control solenoid 17 closes the spill passage 18 is advanced to increase the discharge amount of the high-pressure fuel pump 11 to increase the actual common rail fuel pressure to the target fuel pressure. Move closer. On the other hand, when the actual common rail fuel pressure is higher than the target fuel pressure, the timing at which the control solenoid 17 closes the spill passage 18 is delayed to reduce the discharge amount of the high-pressure fuel pump 11 and to decrease the actual common rail fuel pressure. Approach the fuel pressure.

  If the engine load and rotational speed are determined, the required fuel amount per cylinder and cycle is uniquely determined, and if the required fuel amount per common cylinder and cycle and the common rail fuel pressure are determined, the valve opening that is given to the fuel injection valve The pulse width (fuel injection pulse width) is determined. Therefore, the engine controller 41 has a map of the required fuel amount per cylinder per cycle corresponding to the engine load and the rotational speed, and the required fuel per cylinder per cycle from the engine load and the rotational speed at that time. A map of the amount is searched to obtain the required fuel amount per cylinder and one cycle, and the valve opening pulse width to be given to the fuel injection valve is calculated from the required fuel amount per cylinder and one cycle and the common rail fuel pressure. When the injection timing is reached, the fuel injection valve is opened with this valve opening pulse width to supply fuel to each cylinder.

  In the present embodiment, the high-pressure fuel injection valves 31A to 31D are provided facing the combustion chambers of the respective cylinders, and the stratified combustion is performed by performing the compression stroke injection for each cylinder from the time of engine cranking. ing. For example, if the injection end timing is fixed, a predetermined fuel injection pulse width Ti corresponding to the required fuel amount is advanced from the fixed injection end timing by a value converted into a crank angle using the engine speed at that time. The crank angle position on the corner side is the injection start timing. Therefore, a predetermined crank angle position before the actual injection timing arrives is determined as the injection timing calculation timing, and the injection timing (injection start timing) is calculated at this injection timing calculation timing. In this case, there is a Ref signal as a signal of a predetermined crank angle position before the actual injection timing comes. The Ref signal is known and is a signal of the crank angle reference position for each cylinder. For example, as described later, there is a Ref signal that rises at 110 ° before compression top dead center of each cylinder for a four-cylinder engine.

  Now, the fuel injection valves 31 </ b> A to 31 </ b> D have injection amount variations due to the valve behavior of the fuel injection valves. Explaining this, FIG. 4 shows the characteristics (experimental results) of the injection amount variation when the required fuel amount Q and the common rail fuel pressure are made different. As shown in the figure, if the common rail fuel pressure is constant, the variation in the injection amount increases as the required fuel amount Q decreases. If the same required fuel amount Q, the larger the common rail fuel pressure increases.

  Now, the injection amount variation at three typical common rail fuel pressures Pa, Pb, and Pc is shown again as a model in FIG. However, it is assumed that a relationship of Pa <Pb <Pc is established between the three common rail fuel pressures Pa, Pb, and Pc.

  Assuming that the allowable value limit of the injection amount variation in FIG. 5 is at the position of the alternate long and short dash line, the required fuel whose injection amount variation becomes the allowable value limit when the common rail fuel pressure is Pa, Pb, and Pc, respectively, from the characteristics of FIG. The quantities are Qa, Qb and Qc, respectively (Qa <Qb <Qc). Here, since the relationship between the required fuel amount Q and the fuel injection pulse width Ti is expressed by the following equation (1), the fuel injection pulse widths Tia, Tib that give the three required fuel amounts Qa, Qb, Qc are given. , Tic is as follows.

Tia = K × Qa / Pa (Supplement 1)
Tib = K × Qb / Pb (Supplement 2)
Tic = K × Qc / Pc (Supplement 3)
That is, when the common rail fuel pressure is Pa, the fuel injection pulse width Ti calculated from the common rail fuel pressure Pa at this time and the required fuel amount determined from the operating conditions is less than the fuel injection pulse width Tia of the (Supplement 1) type. Then, the injection amount variation exceeds the allowable value limit. Similarly, when the common rail fuel pressure is Pb, the fuel injection pulse width Ti calculated from the common rail fuel pressure Pb at this time and the required fuel amount determined from the operating conditions is the fuel injection pulse width of (Supplement 2). If it is less than Tib, the variation in the injection amount exceeds the allowable limit, and when the common rail fuel pressure is Pc, the fuel injection pulse width Ti calculated from the common rail fuel pressure Pc at this time and the required fuel amount determined from the operating conditions. However, if the fuel injection pulse width Tic is less than (Supplement 3), the injection amount variation exceeds the allowable value limit.

  Here, as shown in FIG. 6A, the horizontal axis represents the common rail fuel pressure, the vertical axis represents the fuel injection pulse width Ti, and the coordinates (Pa, Tia), (Pb, Tib), (Pc, Tic). ) Is entered as shown in the figure, and a curve connecting these points is obtained. This curve has a characteristic that gives a fuel injection pulse width corresponding to the allowable limit of the injection amount variation at the current common rail fuel pressure.

  If the fuel injection pulse width on the vertical axis determined by the characteristics shown in FIG. 6A is changed to the minimum injection pulse width Timin per cylinder as shown in FIG. 6B, the common rail fuel pressure is calculated at the injection timing calculation timing. When the fuel injection pulse width Ti is calculated from the required fuel amount and the calculated fuel injection pulse width Ti is less than the minimum injection pulse width Timin per cylinder, the injection amount variation exceeds the allowable limit. Therefore, in the present invention, when the fuel injection pulse width Ti is less than the minimum injection pulse width Timin per cylinder, the fuel injection of some cylinders is stopped and the remaining fuel injection is not stopped. For the injection cylinder, fuel injection is performed by adding the fuel injection pulse width of the inactive cylinder to the fuel injection pulse width of the injection cylinder. It was vignetting by which the valve operation of the fuel injection valve stabilize the combustion state in the injection cylinder so as not become unstable.

  This control executed by the engine controller 41 will be described in detail according to the following flowchart.

  FIG. 7 is for setting the stratified combustion permission flag, and is executed at regular time intervals (for example, every 10 msec).

  In step 1, the signal from the starter switch 45 is observed. When the signal from the starter switch 45 is ON, it is determined that the engine is being cranked, and the routine proceeds to step 2 to check whether or not there is a request for stratified combustion. The engine operating speed and engine load parameters are divided into two main areas: a stratified combustion area where stratified combustion is performed on the low load side and a homogeneous combustion area where homogeneous combustion is performed under high load. Yes. This is because stratified combustion is performed by compression stroke injection on the low load side where a large engine output is not required, and on the contrary, when the high load side where a large engine output is required, the combustion state is stratified combustion. In order to switch to so-called homogeneous combustion, in which fuel vaporization is sufficiently promoted throughout the entire combustion chamber before the intake stroke injection is performed and combustion is performed. Therefore, if the operating conditions determined from the engine speed and engine load at that time are in the stratified combustion zone, there will be a request for stratified combustion. On the other hand, the operation determined from the engine speed and engine load at that time If the condition is in the homogeneous combustion region, there is no requirement for stratified combustion.

  In the present embodiment, the stratified combustion is performed by performing the compression stroke injection even when the engine is cranked when the starter switch 45 is turned on. For this reason, when the starter switch 45 is ON, it is determined that there is a request for stratified combustion, and the routine proceeds to step 3 where the actual common rail fuel pressure Pr detected by the fuel pressure sensor 42 is read. The fuel pressure Pr is compared with the specified value.

  This specified value is an injection permission fuel pressure described later. The amount of fuel per cylinder and one cycle supplied from the fuel injection valve is determined by the common rail fuel pressure and the fuel injection pulse width. Here, the minimum amount of fuel necessary to stably rotate the engine by stratified combustion and the minimum fuel injection pulse width that compensates for the valve opening accuracy are determined in advance. Therefore, the minimum value of the common rail fuel pressure necessary to stably rotate the engine by stratified combustion is determined from these two values. The specified value is the minimum value of the common rail fuel pressure necessary to stably rotate the engine by this stratified combustion. If the actual common rail fuel pressure Pr is equal to or greater than the specified value, it is determined that the common rail fuel pressure is capable of performing stratified combustion, and the routine proceeds to step 5 where the stratified combustion permission flag (initially set to zero) = 1. To do.

  On the other hand, when the actual common rail fuel pressure Pr is less than the specified value in step 4, it is determined that the common rail fuel pressure capable of performing stratified combustion has not been reached and stratified combustion cannot be performed. Proceed to step 6, and set the injection prohibition flag (initially set to zero) = 1.

  Further, when there is no request for stratified combustion in step 2, the routine proceeds to step 6 where the injection prohibition flag = 1 is set.

  On the other hand, when the starter switch 45 is OFF in step 1 (however, the ignition switch is in the ON state), the process proceeds to step 7 and subsequent steps. Step 7 and subsequent steps are controls after the engine is started. That is, in step 7, it is determined whether or not there is a request for stratified combustion. As described above, if the operating condition determined from the engine rotational speed and the engine load at that time is in the stratified combustion region, there is a request for stratified combustion, and on the other hand, from the engine rotational speed and the engine load at that time, If the determined operating condition is in the homogeneous combustion region, there is no request for stratified combustion. Therefore, when there is a request for stratified combustion, the routine proceeds to step 5 where the stratified combustion permission flag = 1 is set, and when there is no stratified combustion request, step 8 is executed. Then, the stratified combustion permission flag = 0 is set.

  FIGS. 8A and 8B are for calculating the injection timing (injection start timing), and are executed at each rising timing of the Ref signal of each cylinder. That is, the rising timing of the Ref signal is the injection timing calculation timing. The Ref signal is a crank angle reference position signal for each cylinder calculated from a signal from the crankshaft position sensor 21 and a signal from the camshaft position sensor 22.

  In step 11, the stratified combustion permission flag set according to FIG. Since the compression stroke injection should not be permitted when the stratified charge permission flag = 0, the routine proceeds to step 24, where the compression stroke injection permission flag = 0.

  When the stratified combustion permission flag = 1, the routine proceeds to step 12, where the actual common rail fuel pressure Pr [Pa] detected by the fuel pressure sensor 42 is read. In step 13, the common rail fuel pressure Pr and the specified value at the injection timing calculation timing are read. Compare This specified value is the injection permitting fuel pressure (common rail fuel pressure permitting compression stroke injection). Specifically, a value of about 2 MPa is set as the specified value. When the common rail fuel pressure Pr at the injection timing calculation timing is less than the specified value, the routine proceeds to step 22 where the compression stroke injection permission flag = 0.

  When the common rail fuel pressure Pr at the injection timing calculation timing is equal to or higher than a specified value, it is determined that the common rail fuel pressure is reached at which the compression stroke injection can be performed at the injection timing, and the routine proceeds to step 14 where the compression stroke injection permission flag = Set to 1.

  In step 15, the engine speed Ne and the engine load are read, and from these, a predetermined map is searched in step 16, thereby calculating the required fuel amount Q [mg / cycle] per cylinder and one cycle. The required fuel amount Q per cylinder and cycle is a value that increases as the engine load increases if the engine speed is the same.

  In step 17, the fuel injection pulse width Ti [msec] is calculated by the following equation using the required fuel amount Q per cylinder and the common rail fuel pressure Pr at the injection timing calculation timing.

Ti = K × Q / Pr (1)
Where K is a constant,
Equation (1) is obtained as follows. Since the required fuel amount Q [mg / 1 cycle] per cylinder and one cycle is proportional to the common rail fuel pressure P [Pa] and the fuel injection pulse width Ti [msec], it is given by the following equation.

Q = P × Ti × C (2)
Where C: proportionality constant,
When the equation (2) is solved for the fuel injection pulse Ti, the following equation is obtained.

Ti = (1 / C) × Q / P (3)
Here, when 1 / C of the equation (3) is again set to K, the above equation (1) is obtained.

  In step 18, the minimum injection pulse width Timin [msec] per cylinder is calculated from the common rail fuel pressure Pr at the injection timing calculation timing. The minimum injection pulse width Timin per cylinder is a value corresponding to the allowable limit of the injection amount variation caused by the valve behavior of the fuel injection valve. If the specifications of the fuel injection valve are different, the minimum injection pulse width Timin per cylinder is also Is different. The minimum injection pulse width Timin per cylinder may be obtained by storing the characteristics shown in FIG. 6B determined by the specifications of the fuel injection valve as a table and searching the table.

  In step 19, the fuel injection pulse width Ti obtained in step 17 is compared with the minimum injection pulse width Timin per cylinder. When the fuel injection pulse width Ti is equal to or greater than the minimum injection pulse width Timin per cylinder, the injection amount variation of the fuel injection valve does not exceed the allowable value limit. That is, the routine proceeds to step 20, where the fuel injection pulse width Ti is converted into a crank angle using the engine rotational speed at that time, and the crank angle on the advance side by this converted crank angle from the injection end timing ITend [° BTDC]. Is set as the injection start timing ITst [° BTDC]. Here, the injection end timing ITend is a crank angle measured from the compression top dead center of each cylinder toward the advance side, and is a fixed value. For this reason, the injection start timing ITst also becomes the crank angle measured from the compression top dead center of each cylinder to the advance side.

  In step 21, the injection start timing ITst set in this way is moved to the output register.

  On the other hand, when the fuel injection pulse width Ti is less than the minimum injection pulse width Timin per cylinder in step 19, the variation in the injection amount of the fuel injection valve will exceed the allowable value limit as it is, so FIG. Proceed to step 22 and subsequent steps.

  Here, typical operating conditions in which the fuel injection pulse width Ti is less than the minimum injection pulse width Timin per cylinder include the following.

<1> During low load operation This is because the fuel injection pulse width Ti becomes smaller as a result of the numerator on the right side of the above equation (1) becoming smaller during low load operation where the required fuel amount Q is small, such as during idle operation. .

<2> During fuel cut recovery when the common rail fuel pressure is high This is because the common rail 21 receives heat during fuel cut and the common rail fuel pressure rises. This is because the pulse width Ti becomes small.

<3> At the time of failure of the high-pressure fuel pump <1> and <2> are cases where the high-pressure fuel pump 11 is normal, but when the high-pressure fuel pump 11 is fully discharged (that is, the spill passage 18 is closed). The high pressure fuel pump 11 continues to discharge the maximum amount, and the safety valve 22 is activated to release the fuel in the common rail 21), and the common rail fuel pressure exceeds the normal use range. This is because the denominator on the right side of the above equation (1) is increased and the fuel injection pulse width Ti is decreased.

  In step 22, the smallest integer B that satisfies the following conditional expression is calculated.

Ti × number of cylinders / (number of cylinders−B)> Timin (4)
Here, the integer B represents the number of cylinders that stop fuel injection. Considering the four cylinders specifically, the inequality of equation (4) is as follows.

Ti × 4 / (4-B)> Timin (5)
Since the values that can be taken as the integer B in the formula (5) are 0, 1, 2, and 3, the integers satisfying the formula (5) by substituting B = 0, 1, 2, and 3 into the formula (5), respectively. The value of B is left, and the smallest value is selected as B. Here, it is assumed that the value of B is any one of 1, 2, and 3 as a result of selection.

  In steps 23 and 24, it is checked whether the selected integer B has a value of 1, 2 or 3.

  When the integer B is 1 in step 23, the process proceeds to step 25 to inject fuel in 3 cylinders out of 4 cylinders and stop the fuel injection in the remaining 1 cylinder. 3-1 flag (initially set to zero when the engine is started) = 1 And Then, in order to allocate the fuel for one cylinder that has stopped fuel injection to the remaining three cylinders that perform fuel injection, in step 26, the fuel injection pulse width Ti obtained in step 17 of FIG. The tripled value is set as the fuel injection pulse width Tizou of the injection cylinder. The fuel injection pulse width Tizou set in this way is larger than the minimum injection pulse width Timin per cylinder. As a result, fuel for one idle cylinder is evenly distributed to the remaining three cylinders, and an engine torque equivalent to that in the case where fuel injection is performed in all four cylinders is generated in the entire four cylinders.

  When the integer B is 2 in step 24, the routine proceeds to step 27 to inject fuel in 2 of the 4 cylinders and stop fuel injection in the remaining 2 cylinders. 2-2 flag (initially set to zero when the engine is started) = 1 And Then, in order to allocate the fuel for the two cylinders that have stopped fuel injection to the remaining two cylinders that perform fuel injection, in step 28, the fuel injection pulse width Ti obtained in step 17 of FIG. A value multiplied by 2 (= 2) is set as the fuel injection pulse width Tizou of the injection cylinder. The fuel injection pulse width Tizou set in this way is larger than the minimum injection pulse width Timin per cylinder. As a result, the fuel for the two idle cylinders is evenly distributed to the remaining two cylinders, and an engine torque equivalent to that in the case where fuel injection is performed in all four cylinders is generated in the entire four cylinders.

  When the integer B is 3 in step 24, the fuel injection is performed in one cylinder and the fuel injection is stopped in the remaining three cylinders. Then, the process proceeds to step 29 and the 1-3 flag (initially set to zero when the engine is started) is set to 1. Then, in order to allocate the fuel for the three cylinders that have stopped fuel injection to the remaining one cylinder that performs fuel injection, in step 30, the fuel injection pulse width Ti obtained in step 17 of FIG. A value multiplied by 1 (= 4) is set as the fuel injection pulse width Tizou of the injection cylinder. The fuel injection pulse width Tizou set in this way is larger than the minimum injection pulse width Timin per cylinder. As a result, the fuel for the three idle cylinders is all distributed to the remaining one cylinder, and the engine torque equivalent to that in the case where fuel injection is performed in all the four cylinders is generated in the entire four cylinders.

  In step 31, it is determined whether or not the cylinder is an injection cylinder. Here, when the integer B = 1, which one of the four cylinders is a deactivated cylinder, when the integer B = 2, which two of the four cylinders are deactivated, or the integer B = In the case of 3, it is only necessary to determine in advance which of the four cylinders are to be deactivated cylinders, and therefore the injection cylinders are also determined. If it is not an injection cylinder (that is, it is a non-injection cylinder), the current process is terminated without calculating the injection start timing.

  If the cylinder is an injection cylinder, the routine proceeds to step 32, where the fuel injection pulse width Tizou set in any of the above steps 26, 28, 30 is converted into a crank angle using the engine speed at that time, and the injection end timing is reached. The crank angle that is advanced by the converted crank angle from ITend [° BTDC] is set as the injection start timing ITst [° BTDC] of the injection cylinder.

  In step 32, the injection start timing ITst of the injection cylinder set in this way is transferred to the output register.

  In the present invention, the intake stroke injection is performed in the homogeneous combustion region, and the calculation of the fuel injection pulse width in the homogeneous combustion region, that is, the homogeneous combustion region is not omitted.

  FIG. 9 is for executing fuel injection, and the execution timing is the injection start timing of each cylinder.

  In step 41, the injection prohibition flag set in FIG. When the injection prohibition flag = 1, the current process is terminated without executing the fuel injection.

  When the injection prohibition flag = 0 in step 41, the routine proceeds to step 42 and the compression stroke injection permission flag set in FIG. 8 (A) and FIG. 8 (B) is viewed. When the compression stroke injection permission flag = 1, the routine proceeds to steps 43, 44, 45, and the 3-1 flag, 2-2 flag, and 1-3 flag are viewed.

  If 3-1 flag = 1 in step 43, the process proceeds to step 46 to check whether the cylinder is an injection cylinder. If it is not an injection cylinder, the process is terminated (cylinder deactivation). If the cylinder is an injection cylinder, the routine proceeds to step 49, where fuel injection in the compression stroke is executed using the injection start timing ITst (obtained at step 32 of FIG. 8B) and the injection end timing ITend. That is, the fuel injection valve is opened during the period from the injection start timing ITst to the injection end timing ITend.

  When 2-2 flag = 1 at step 44, the routine proceeds to step 47 where it is determined whether or not the cylinder is an injection cylinder. If it is not an injection cylinder, the process is terminated (cylinder deactivation). When the cylinder is an injection cylinder, the routine proceeds to step 50, and fuel injection is executed in the compression stroke using the injection start timing ITst (obtained at step 32 of FIG. 8B) and the injection end timing ITend. That is, the fuel injection valve is opened during the period from the injection start timing ITst to the injection end timing ITend.

  When 1-3 flag = 1 in step 45, the routine proceeds to step 48, where it is determined whether or not the cylinder is an injection cylinder. If it is not an injection cylinder, the process is terminated (cylinder deactivation). When the cylinder is an injection cylinder, the routine proceeds to step 51, where fuel injection in the compression stroke is executed using the injection start timing ITst (obtained at step 32 of FIG. 8B) and the injection end timing ITend. That is, the fuel injection valve is opened during the period from the injection start timing ITst to the injection end timing ITend.

  In this way, when the integer B = 1, the compression stroke injection is performed for three of the four cylinders, and the fuel injection is stopped for the remaining one cylinder. When the integer B = 2, compression stroke injection is performed in two of the four cylinders, and fuel injection is stopped in the remaining two cylinders. When the integer B = 1, the compression stroke injection is performed in one cylinder of the four airs, and the fuel injection is stopped in the remaining three cylinders.

  When the 3-1 flag, the 2-2 flag, and the 1-3 flag are all zero in steps 43, 44, and 45, the process proceeds to step 52 and is obtained at the injection start timing ITst (step 20 of FIG. 8A). ) And the injection end timing ITend, the fuel injection in the compression stroke is executed. That is, the fuel injection valve is opened during the period from the injection start timing ITst to the injection end timing ITend. The flow to step 52 is when the fuel injection pulse width Ti is greater than or equal to the minimum injection pulse width Timin per cylinder in step 19 of FIG. 8A. At this time, compression stroke injection is executed in all cylinders. .

  On the other hand, when the compression stroke injection permission flag = 0, the routine proceeds from step 42 to step 50, where fuel injection in the intake stroke is executed.

  Here, the effect of the present embodiment will be described.

  According to the present embodiment (the invention described in claim 1), the fuel injection pulse width Ti given to the fuel injection valves 31A to 31D is calculated (step 17 in FIG. 8B), and the calculated fuel injection pulse width is calculated. When Ti is less than the minimum injection pulse width Timin per cylinder, the fuel injection of some cylinders is stopped (step 19 in FIG. 8A, steps 22, 23, 24, and 25 in FIG. 8B). 27, 29, steps 43, 44, 45, 46, 47, 48 in FIG. 9), the fuel injection pulse width of the injection cylinder is increased (step 19 in FIG. 8A, step in FIG. 8B). 22, 23, 24, 26, 28, 30), the fuel injection pulse width Tizou that is actually given to the fuel injection valve will not be less than the minimum injection pulse width Timin per cylinder. Even when the pulse width Ti is less than the minimum injection pulse width Timin per cylinder, it is possible to stabilize the valve operation of the fuel injection valve provided in the injection cylinder, and the combustion stability in the injection cylinder is improved. .

  In the embodiment, the pump drive cam 12 is provided on the intake valve camshaft and the high-pressure fuel pump is driven by the pump drive cam. However, the present invention is not limited to this configuration. For example, the high-pressure fuel pump may be a swash plate type, or the pump drive cam 12 may be provided on the exhaust valve camshaft. Furthermore, the pump drive cam can be provided on a shaft other than the camshaft. The high pressure fuel pump may be driven by a motor. It is not essential to provide a common rail.

  In the embodiment, the case where the present invention is applied to the compression stroke injection has been described, but the present invention can also be applied to the intake stroke injection. Furthermore, the present invention can also be applied to a fuel injection valve provided facing the intake port.

  The function of the fuel injection pulse width calculating means of claim 1 is according to step 17 in FIG. 8B, and the function of the partial cylinder deactivation means is step 19 in FIG. 8A and steps 22 and 23 in FIG. 8B. , 24, 25, 27, 29, and steps 43, 44, 45, 46, 47, and 48 of FIG. 9, the function of the injection cylinder fuel injection pulse width increasing means is as shown in steps 19 and 8 of FIG. ) Steps 22, 23, 24, 26, 28 and 30.

1 is a schematic configuration diagram of a fuel supply device according to a first embodiment of the present invention. The top view of a pump drive cam. The wave form diagram for demonstrating the action | operation of a high pressure fuel pump. The characteristic figure of injection amount variation. The characteristic figure of injection amount variation. The characteristic view which shows the relationship between the common rail fuel pressure and the fuel injection pulse width in the allowable value limit of injection quantity dispersion | variation. The characteristic diagram of the minimum injection pulse width per cylinder. The flowchart for demonstrating the setting of a stratified combustion permission flag. The flowchart for demonstrating injection timing calculation. The flowchart for demonstrating injection timing calculation. The flowchart for demonstrating execution of fuel injection. The characteristic view which shows the relationship between a fuel-injection pulse width and fuel amount.

Explanation of symbols

12 Pump drive cam (actuator)
31A to 31D Fuel injection valve 41 Engine controller 42 Fuel pressure sensor

Claims (5)

A high pressure fuel pump driven by an actuator to discharge high pressure fuel;
In a fuel supply device for a multi-cylinder engine comprising: a fuel injection valve that opens for a predetermined fuel injection pulse width at a predetermined fuel injection timing and supplies high-pressure fuel from the high-pressure fuel pump to the engine;
Fuel injection pulse width calculating means for calculating the fuel injection pulse width given to the fuel injection valve;
Partial cylinder deactivation means for deactivating fuel injection in some cylinders when the calculated fuel injection pulse width is less than the minimum injection pulse width per cylinder;
And an injection cylinder fuel injection pulse width increasing means for increasing the fuel injection pulse width of the injection cylinder when the calculated fuel injection pulse width is less than the minimum injection pulse width per cylinder.
A fuel supply apparatus for a multi-cylinder engine, wherein the minimum injection pulse width per cylinder is increased as the pressure of fuel discharged from the high-pressure fuel pump increases. 2. The number of idle cylinders for stopping the fuel injection that can increase the fuel injection pulse width of the injection cylinder to be equal to or larger than the minimum injection pulse width per cylinder is calculated. Fuel supply system for cylinder engines. 3. The fuel supply apparatus for a multi-cylinder engine according to claim 2 , wherein a minimum value is selected from the calculated number of idle cylinders. Wherein the fuel injection pulse width of the injection cylinder, the fuel supply apparatus for a multi-cylinder engine according to claim 1, characterized in that increasing in correspondence to the number of cylinders has suspended the fuel injection. 5. The fuel supply apparatus for a multi-cylinder engine according to claim 4 , wherein the fuel injection pulse width of the injection cylinder is increased as the number of cylinders that stopped the fuel injection is increased .

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