JP2007023801A - Fuel pressure control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To calculate a feed forward term used for drive control of a high pressure fuel pump to be an appropriate value of a value intended for previously supplying the corresponding amount of fuel to the fuel amount to be injected from a fuel injection valve. <P>SOLUTION: Depending on the amount of a target fuel pressure PO, the work load of the high pressure fuel pump 4 required for controlling the actual fuel pressure toward the target fuel pressure PO changes, and correspondingly, the appropriate value as the value having the above intention of a feed forward term FF changes. Taking this into consideration, upon calculating the feed forward term FF, not only an indication value Q and the engine speed are considered, but the target fuel pressure PO is also considered. Therefore, even when the appropriate value as the value having the above intention for the feed forward term FF changes according to the amount of the target fuel pressure PO, the calculated feed forward term FF can be changed according to the change of the appropriate value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel pressure control device for an internal combustion engine.

  As a fuel pressure control device for an internal combustion engine, for example, as shown in Patent Document 1, a high-pressure fuel pump that discharges fuel toward a fuel pipe connected to a fuel injection valve is driven based on a drive command value, and through the drive control There is known one that controls the fuel pressure in the fuel pipe to the target fuel pressure by adjusting the fuel discharge amount from the pump.

  A drive command value for a high-pressure fuel pump used for fuel pressure control in the apparatus is calculated based on a feedforward term, a proportional term, and an integral term. Here, the proportional term is a value that increases or decreases based on the deviation between the two in order to bring the actual fuel pressure in the fuel pipe closer to the target fuel pressure. The integral term is a value obtained by accumulating the deviations between the actual fuel pressure and the target fuel pressure in order to eliminate the residual deviation between the actual fuel pressure and the target fuel pressure that cannot be removed by the proportional term alone. . In the feedforward term, in order to quickly converge the actual fuel pressure to the target fuel pressure even during engine transient operation, etc., an amount of fuel corresponding to the amount of fuel injected from the fuel injection valve is supplied to the fuel pipe in advance. This is the intended value.

  By calculating the drive command value of the high pressure fuel pump based on the feedforward term, the proportional term, and the integral term as described above, when the drive control of the high pressure fuel pump is performed based on the drive command value, the actual fuel pressure is quickly And precisely controlled to the target fuel pressure.

  Here, the feedforward term included in the drive command value is calculated based on the indicated value of the amount of fuel injected from the fuel injection valve with the intention described above. Further, when calculating the feedforward term, the engine rotational speed is taken into consideration in addition to the indicated value because the fuel discharge efficiency of the high-pressure fuel pump changes according to the engine rotational speed. The fuel discharge efficiency of the high-pressure fuel pump changes according to the engine rotation speed because the high-pressure fuel pump is driven based on the engine rotation.

By calculating the feedforward term as described above, the feedforward term is set as a value having the above intention without being affected by a change in the fuel discharge efficiency of the high-pressure fuel pump in accordance with a change in the engine speed. Will be able to be appropriate. Accordingly, the actual fuel pressure is controlled even during engine transient operation by controlling the high pressure fuel pump based on the drive command value including the feed forward term and adjusting the fuel discharge amount from the pump through the drive control. It becomes possible to quickly converge to the target fuel pressure.
JP 2001-263144 A

  By the way, even if the feedforward term is calculated based on the indicated value of the amount of fuel injected from the fuel injection valve and the engine speed as described above, the feedforward term is not necessarily an appropriate value as the value having the above intention. It was confirmed that this is not always the case.

  This is because the amount of work of the high-pressure fuel pump required to control the actual fuel pressure toward the target fuel pressure varies depending on the magnitude of the target fuel pressure, and the appropriate value for the feedforward term is also correspondingly changed. It is related to change. That is, while the appropriate value varies depending on the target fuel pressure, in the above-described method of calculating the feedforward term, the calculated feedforward term corresponds to the change in the appropriate value. It cannot be changed. This is presumed to be the cause of the above-mentioned problems.

  Therefore, depending on the magnitude of the target fuel pressure, the calculated feedforward term becomes inappropriate as the value having the above intention, and when the high pressure fuel pump is driven and controlled based on the drive command value including the feedforward term etc., It becomes difficult to quickly converge the fuel pressure to the target fuel pressure.

  The present invention has been made in view of such circumstances, and its object is to provide a feed-forward term used for drive control of a high-pressure fuel pump in an amount corresponding to the amount of fuel injected from the fuel injection valve. Is to provide a fuel pressure control device for an internal combustion engine that can be calculated to an appropriate value as a value intended to be supplied to the fuel pipe in advance.

In the following, means for achieving the above object and its effects are described.
In order to achieve the above object, according to the first aspect of the present invention, there is provided a high pressure fuel pump that discharges fuel toward a fuel pipe connected to a fuel injection valve of an internal combustion engine, and a feed included in a drive command value of the high pressure fuel pump. A forward term is calculated based on an instruction value of the fuel amount injected from the fuel injection valve and an engine speed, and a fuel discharge amount from the pump is adjusted through drive control of the high-pressure fuel pump based on the drive command value. In the fuel pressure control apparatus for an internal combustion engine that controls the actual fuel pressure in the fuel pipe to the target fuel pressure, the feedforward term is the indicated value of the amount of fuel injected from the fuel injection valve and the engine speed In addition to the above, a calculation means for calculating the target fuel pressure is provided.

  The feedforward term included in the drive command value of the high-pressure fuel pump is calculated as a value intended to supply in advance to the fuel pipe an amount of fuel commensurate with the amount of fuel injected from the fuel injection valve. If such a feedforward term is calculated only from the amount of fuel injected from the fuel injection valve and the engine speed, the calculated feedforward term has the above intention depending on the target fuel pressure at that time. It becomes inappropriate as a value. This is because the work of the high-pressure fuel pump required to control the actual fuel pressure toward the target fuel pressure changes according to the target fuel pressure, and the appropriate value for the feedforward term changes accordingly. However, the above-described method of calculating the feedforward term is because the calculated feedforward term cannot be changed in response to the change in the appropriate value. However, according to the above configuration, the feedforward term is calculated not only based on the instruction value and the engine speed, but also in consideration of the target fuel pressure in addition to the above, and according to the target fuel pressure. Further, the calculated feedforward term can be changed corresponding to the change in the appropriate value. Therefore, the calculated feed-forward term becomes an appropriate value as the value having the above intention without being affected by the change in the target fuel pressure. When the high pressure fuel pump is driven and controlled based on the drive command value including this feedforward term, the actual fuel pressure can be quickly converged to the target fuel pressure.

  According to a second aspect of the present invention, in the first aspect of the present invention, the calculating means increases the feedforward term as the target fuel pressure increases, and decreases the feedforward term as the target fuel pressure decreases. It was supposed to be

  The higher the target fuel pressure, the greater the workload of the high-pressure fuel pump required to control the actual fuel pressure to the target fuel pressure, and accordingly, the appropriate value as the value having the above intention in the feedforward term is large. It becomes. In addition, the smaller the target fuel pressure, the smaller the work of the high-pressure fuel pump required to control the actual fuel pressure to the target fuel pressure, and accordingly, the appropriate value as the value having the above intention in the feedforward term. The value is small. According to the above configuration, the feedforward term can be increased as the target fuel pressure increases, and the feedforward term can be decreased as the target fuel pressure decreases. When the correct value changes, the calculated feedforward term can be accurately changed in response to the change of the appropriate value.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the calculating means calculates the feedforward term by multiplying the indicated value by a coefficient, and the coefficient is used as an engine speed and a target. It was supposed to be variable according to the fuel pressure.

  According to the above configuration, by changing the coefficient according to the target fuel pressure, the feedforward term obtained by multiplying the indicated value by the coefficient can be accurately changed according to the target fuel pressure.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the calculation means calculates the feedforward term based on an engine load as the indicated value. The gist is to use what was obtained by adding various corrections to the value.

  Since the amount of fuel injected from the fuel injector varies depending on the engine load and various corrections, a value intended to supply in advance to the fuel pipe an amount of fuel commensurate with the amount of fuel injected from the fuel injector. The feedforward term calculated as follows also needs to be changed according to the engine load and various corrections. According to the above configuration, the instruction value used for calculating the feedforward term, that is, the instruction value for the amount of fuel injected from the fuel injection valve is obtained by applying various corrections to the base value obtained according to the engine load. . Therefore, the calculated feedforward term can be changed according to the engine load and various corrections, and the feedforward term can be set to an appropriate value as the value having the above intention.

Hereinafter, an embodiment in which the present invention is applied to an in-cylinder injection internal combustion engine for an automobile will be described with reference to FIGS.
FIG. 1 is a schematic diagram showing the entire fuel supply system of the internal combustion engine. As shown in the figure, the fuel supply system includes a feed pump 2 for sending fuel from a fuel tank 1 and a delivery for pressurizing the fuel sent by the feed pump 2 to connect to the fuel injection valve 3 of the internal combustion engine. A high-pressure fuel pump 4 that discharges toward the pipe 13 is provided.

  The high-pressure fuel pump 4 includes a plunger 8 that reciprocates in a cylinder 9 based on the rotation of a cam 6 attached to a camshaft 5 of an internal combustion engine and the urging force of a coil spring 7. Further, the high-pressure fuel pump 4 is formed with a pressurizing chamber 10 which is partitioned by a plunger 8 and a cylinder 9 and whose volume changes as the plunger 8 reciprocates. As the cam 6 rotates, the suction stroke in which the plunger 8 moves in the direction of expanding the pressurizing chamber 10 and the pressure feeding stroke in which the plunger 8 moves in the direction of reducing the pressurizing chamber 10 are alternately performed. Repeated. The suction stroke is a stroke in which the fuel from the feed pump 2 is sucked into the pressurizing chamber 10 through the suction passage 11. The pressure feeding stroke is the fuel in the pressurizing chamber 10 being pressurized and discharged into the discharge passage 12. Is the process. The high-pressure fuel discharged from the high-pressure fuel pump 4 in this pumping stroke is supplied to the delivery pipe 13 for distributing the fuel to the fuel injection valve 3 through the discharge passage 12.

  The high-pressure fuel pump 4 is provided with an electromagnetic spill valve 14 that opens and closes so as to communicate and block between the suction passage 11 and the pressurizing chamber 10. The electromagnetic spill valve 14 includes an electromagnetic solenoid 15 and opens and closes by controlling voltage application to the solenoid 15. In other words, in the state where the energization to the electromagnetic solenoid 15 is stopped, the electromagnetic spill valve 14 is opened by the urging force of the coil spring 17 and the suction passage 11 and the pressurizing chamber 10 are in communication with each other. When the electromagnetic solenoid 15 is energized, the electromagnetic spill valve 14 is closed against the biasing force of the coil spring 17 and the suction passage 11 and the pressurizing chamber 10 are shut off.

  In the high-pressure fuel pump 4, the electromagnetic spill valve 14 is opened during the intake stroke, thereby permitting fuel to flow from the intake passage 11 into the pressurizing chamber 10. In the pressure feed stroke, the electromagnetic spill valve 14 is closed only for a predetermined period, and the fuel in the pressurizing chamber 10 overflows into the suction passage 11 while the spill valve 14 is opened, and the spill The overflow is prohibited while the valve 14 is closed. Thus, when the overflow of the fuel is prohibited, the fuel in the pressurizing chamber 10 is discharged into the discharge passage 12 in a pressurized state. Therefore, the fuel discharge amount of the high-pressure fuel pump 4 is adjusted by controlling the valve closing time of the electromagnetic spill valve 14 in the pressure feed stroke and adjusting the amount of fuel overflowing from the pressurizing chamber 10 to the suction passage 11. be able to.

  Such drive control of the high-pressure fuel pump 4 is performed by an electronic control unit 18 that controls various devices mounted on the internal combustion engine. The electronic control unit 18 includes a CPU that executes various calculations related to the above control, a ROM that stores programs and data necessary for the control, a RAM that temporarily stores the calculation results of the CPU, and signals between the outside Are provided with an input / output port and the like.

Various sensors including the following sensors are connected to the input port of the electronic control unit 18.
A fuel pressure sensor 19 that detects fuel pressure in the delivery pipe 13 (pressure of fuel supplied to the fuel injection valve 3).

A crank position sensor 20 that outputs a signal corresponding to the rotation of the crankshaft of the internal combustion engine and is used for detection of the engine rotation speed and the like.
A cam position sensor 21 that outputs a signal corresponding to the rotational position of the shaft 5 in response to the rotation of the cam shaft 5 of the internal combustion engine.

An accelerator position sensor 22 that detects the amount of depression of the accelerator pedal (accelerator depression amount) that is depressed by the driver of the automobile.
A throttle position sensor 23 that detects the opening (throttle opening) of the throttle valve of the internal combustion engine.

An air flow meter 24 that detects the flow rate of air taken into the combustion chamber of the internal combustion engine (intake air flow rate).
Drive circuits of various devices such as the fuel injection valve 3 and the electromagnetic spill valve 14 are connected to the output port of the electronic control unit 18.

  The electronic control unit 18 outputs a command signal to the drive circuit of various devices connected to the output port in accordance with the engine operation state grasped by the detection signals from the various sensors, and executes control of those devices. . In this way, various controls such as the fuel injection amount control of the internal combustion engine and the fuel pressure control in the delivery pipe 13 are performed by the electronic control unit 18.

  Here, in the fuel injection amount control, an instruction value Q of the fuel amount injected from the fuel injection valve 3 is calculated based on, for example, the following equation (1), and the fuel injection valve 3 is driven and controlled based on the instruction value Q. This is realized by injecting an amount of fuel corresponding to the indicated value Q from the fuel injection valve 3.

Q = KL · H · Qmax (1)
Q: indicated value
KL: Load factor
H: Correction coefficient
Qmax: Full load injection amount The full load injection amount Qmax used in the equation (1) is a theoretical value of the fuel amount to be injected from the fuel injection valve 3 at the maximum engine load (full load), and depends on the internal combustion engine. It is a fixed value determined in advance. Further, the load factor KL of the equation (1) is a value indicating the current load ratio with respect to the maximum engine load, and is calculated based on the amount of air taken into the combustion chamber per cycle of the internal combustion engine. The amount of air is obtained based on parameters such as the accelerator depression amount, the throttle opening, the intake air flow rate, and the engine speed. A value “KL · Qmax” obtained by multiplying the load factor KL and the total load injection amount Qmax is a base value of the instruction value Q and corresponds to the engine load. Further, the correction coefficient H in the equation (1) is for applying various corrections to the base value “KL · Qmax”, and is increased or decreased according to the engine operating state for the correction.

  The fuel pressure in the delivery pipe 13 is controlled by driving the pump 4 based on a pump duty DT that is a drive command value for driving the high-pressure fuel pump 4, and the amount of fuel discharged from the pump 4 through the drive control. It is realized by adjusting. More specifically, the valve closing time of the electromagnetic spill valve 14 during the pumping stroke of the high-pressure fuel pump 4 is controlled based on the pump duty DT, thereby adjusting the fuel discharge amount from the high-pressure fuel pump 4 and The fuel pressure is controlled.

Here, the pump duty DT will be described with reference to FIG.
This figure is a graph showing how the lift amount of the plunger 8 changes with respect to the change of the cam angle of the cam 6 that lifts the plunger 8 of the high-pressure fuel pump 4. In the figure, “θ 0” represents the cam angle (maximum cam angle) of the cam 6 corresponding to the entire pumping stroke of the high-pressure fuel pump 4, and “θ” is the target of the valve closing time of the electromagnetic spill valve 14 during the pumping stroke. The cam angle (target cam angle) of the cam 6 corresponding to the value is represented. The pump duty DT indicates the ratio of the target cam angle θ to the maximum cam angle θ0, and varies between 0 and 100%.

  The closer this pump duty DT is to "0%", the shorter the valve closing time during the pumping stroke of the electromagnetic spill valve 14 controlled based on the pump duty DT. As a result, the amount of fuel discharged from the high-pressure fuel pump 4 decreases, and the fuel pressure in the delivery pipe 13 decreases. Conversely, the closer the pump duty DT is to “100%, the shorter the valve closing time during the pumping stroke of the electromagnetic spill valve 14 controlled based on the pump duty DT. As a result, the fuel from the high-pressure fuel pump 4 is reduced. The discharge amount increases and the fuel pressure in the delivery pipe 13 increases.

Next, a procedure for calculating the pump duty DT will be described.
The pump duty DT is calculated using the following equation (2) based on the feedforward term FF, the proportional term DTp, and the integral term DTi.

DT = FF + DTp + DTi (2)
DT: Pump duty
FF: Feed forward term
DTp: proportional term
DTi: integral term The feedforward term FF, proportional term DTp, and integral term DTi used in this equation (1) are calculated as follows.

[Proportional term DTp]
The proportional term DTp increases or decreases based on the deviation (pressure difference) between the two so that the actual fuel pressure P in the delivery pipe 13 detected by the fuel pressure sensor 19 approaches the target fuel pressure P0 calculated based on the engine operating state. The value to be Specifically, the proportional term DTp is calculated using the following equation (3) based on the fuel pressure P, the target fuel pressure P0, and the like.

DTp = K2 · (P0−P) (3)
DTp: proportional term
K2: coefficient
P0: Target fuel pressure
P: Actual fuel pressure The coefficient K2 in this equation (3) is used to convert the parameter "P0 -P" between the actual fuel pressure P and the target fuel pressure P0 into a parameter corresponding to the pump duty DT. belongs to.

  Further, the target fuel pressure P0 used in the equation (3) is calculated based on the engine load and the engine speed. As the engine load here, the amount of air taken into the combustion chamber per cycle of the internal combustion engine is used. As shown in FIG. 3, the target fuel pressure P0 calculated as described above increases as the engine load increases and increases as the engine speed increases.

  The target fuel pressure P0 is increased as the engine load increases because the fuel injection amount from the fuel injection valve 3 increases as the engine load increases, and the fuel present in the delivery pipe 13 increases. This is because the amount of fuel supplied to the delivery pipe 13 needs to be increased correspondingly. On the other hand, the target fuel pressure P0 is set to a larger value as the engine speed increases. The period during which fuel injection from the fuel injection valve 3 during one cycle of the internal combustion engine can be performed becomes shorter as the engine speed increases. Correspondingly, the fuel pressure in the delivery pipe 13 is increased so that fuel for the indicated value Q can be injected from the fuel injection valve 3 in a shorter time.

  As can be seen from the equation (3), when the actual fuel pressure P is lower than the target fuel pressure P0, the proportional term DTp becomes larger as the actual fuel pressure P becomes lower than the target fuel pressure P0. The pump duty DT is changed to the 100% side. Accordingly, in this case, the closing time of the electromagnetic spill valve 14 during the pumping stroke of the high-pressure fuel pump 4 becomes longer, the fuel discharge amount of the pump 4 is increased, and the actual fuel pressure P is directed toward the target fuel pressure P0. Raised. On the other hand, if the actual fuel pressure P is higher than the target fuel pressure P0, the proportional term DTp becomes smaller as the actual fuel pressure P becomes higher than the target fuel pressure P0, and the pump duty DT is reduced to 0%. Will change to the side. Therefore, in this case, the closing time of the electromagnetic spill valve 14 during the pumping stroke of the high-pressure fuel pump 4 is shortened, the fuel discharge amount of the pump 4 is reduced, and the actual fuel pressure P is directed toward the target fuel pressure P0. Reduced.

[Integration term DTi]
The integral term DTi is a value obtained by accumulating the deviation between the fuel pressure P and the target fuel pressure P0 in order to eliminate the residual deviation between the actual fuel pressure P and the target fuel pressure P0 that cannot be removed by the proportional term DTp alone. It is. Specifically, the integral term DTi is calculated using the following equation (4) based on the previous integral term DTi, fuel pressure P, target fuel pressure P0, and the like.

DTi = previous DTi + K2.multidot. (P0-P) (4)
DTi: integral term
K2: coefficient
P0: Target fuel pressure
P: Actual fuel pressure As the coefficient K3 in the equation (4), a value smaller than the coefficient K2 in the equation (2) described above is used.

  As can be seen from the equation (4), the integral term DTi is added with a value obtained by multiplying the deviation "P0 -P" between the actual fuel pressure P and the target fuel pressure P0 by the coefficient K3. Therefore, as long as the actual fuel pressure P is lower than the target fuel pressure P0, the integral term DTi is gradually updated to a larger value as a cumulative value of the deviation "P0-P". The pump duty DT is changed to 100%. While the actual fuel pressure P is higher than the target fuel pressure P0, the integral term DTi is gradually updated to a smaller value as a cumulative value of the deviation "P0-P". DT is changed to 0%. As described above, the proportional duty DTp is removed by changing the pump duty DT based on the integral term DTi and adjusting the closing time of the electromagnetic spill valve 14 during the pumping stroke of the high-pressure fuel pump 4 accordingly. It is possible to eliminate the residual deviation between the actual fuel pressure P and the target fuel pressure P0 that cannot be achieved.

[Feed forward term FF]
The feed-forward term FF supplies in advance a delivery pipe 13 with an amount of fuel commensurate with the amount of fuel injected from the fuel injection valve 3 in order to quickly converge the actual fuel pressure P to the target fuel pressure P0 even during engine transient operation or the like. The value is intended to be supplied to Specifically, the feedforward term FF is calculated using the following formula (5) based on the indicated value Q of the fuel amount injected from the fuel injection valve based on the above-described intention. Calculation is performed.

FF = Q · K1 (5)
FF: Feed forward term
Q: Indicated value of the amount of fuel injected from the fuel injection valve
K1: Coefficient The coefficient K1 in the equation (5) is for converting the parameter corresponding to the fuel injection amount of the instruction value Q into a parameter corresponding to the pump duty DT, and is variable according to the engine speed. Is set. The coefficient K1 is changed according to the engine rotational speed in consideration of the fact that the fuel discharge efficiency of the high-pressure fuel pump 4 that operates based on the rotation of the internal combustion engine changes according to the engine rotational speed. This is for the feedforward term FF to be an appropriate value as the above-described intention even if the change in the value occurs.

  By calculating the pump duty DT based on the proportional term DTp, the integral term DTi, and the feedforward term FF described above, when the high pressure fuel pump 4 is driven and controlled based on the pump duty DT, the actual fuel pressure P is quickly determined. And it becomes possible to control to the target fuel pressure P0 accurately.

Next, the effect when the feed-forward term FF is included in the pump duty DT will be described with reference to the time chart of FIG. 4 in comparison with the case where it is not included.
The solid line in the figure shows the transition of the actual fuel pressure P with respect to the target fuel pressure P0 when the pump duty DT is calculated without including the feed forward term FF and the high pressure fuel pump 4 is driven and controlled based on the pump duty DT. ing. In this case, the fuel in the delivery pipe 13 is consumed based on the fuel injection from the fuel injection valve 3, and after the fuel pressure P has decreased by a corresponding amount to the target fuel pressure P0, the deviation "P0 -P" between them is proportional. It is reflected in the term DTp and the like. Then, the amount of fuel discharged from the high-pressure fuel pump 4 is increased by an amount corresponding to the deviation “P0−P” in the proportional term DTp, and the actual fuel pressure P is brought closer to the target fuel pressure P0.

  However, in this case, after the fuel injection from the fuel injection valve 3 is performed, the high pressure fuel pump 4 for controlling the fuel pressure P to the target fuel pressure P0 must be changed after the fuel pressure P changes. Thus, the fuel discharge amount is not increased, and the convergence of the fuel pressure P with respect to the target fuel pressure P0 is deteriorated. For this reason, the fuel pressure P is disturbed with respect to the target fuel pressure P0 every time fuel is injected from the fuel injection valve 3, and the fuel injection amount from the fuel injection valve 3 is likely to change greatly, especially during engine transient operation. Under this condition, the turbulence of the fuel pressure P with respect to the target fuel pressure P0 tends to increase. Such disturbance of the fuel pressure P with respect to the target fuel pressure P0 is suppressed by calculating the pump duty DT including the feedforward term FF.

  The broken line in FIG. 4 shows the transition of the actual fuel pressure P with respect to the target fuel pressure P0 when the pump duty DT including the feedforward term FF is calculated and the high-pressure fuel pump 4 is driven and controlled based on the pump duty DT. Yes. In this case, prior to the fuel injection from the fuel injection valve 3, based on the instruction value Q of the fuel amount injected from the fuel injection valve 3, the feed forward term FF supplies in advance a quantity of fuel corresponding to the fuel amount. 13 is calculated as a value intended to be supplied to 13. Therefore, the fuel discharge amount from the high-pressure fuel pump 4 when the pump duty DT is calculated including the feedforward term FF is the fuel pressure P in the delivery pipe 13 corresponding to the amount of fuel injected from the fuel injection valve 3. In anticipation of the decline, it will be increased accordingly. As a result, it is possible to suppress the disturbance of the fuel pressure P with respect to the target fuel pressure P0 caused by the fuel injection from the fuel injection valve 3 as shown by a broken line in FIG.

  By the way, even if the feedforward term FF is calculated as described above, the feedforward term FF is supplied to the delivery pipe 13 in advance with an amount corresponding to the intention, that is, the amount of fuel injected from the fuel injection valve 3. It was confirmed that the value having the intention is not necessarily an appropriate value.

  This is because the magnitude of the target fuel pressure P0 changes as shown by the arrow in FIG. 4, and the actual fuel pressure is controlled toward the target fuel pressure P0 according to the magnitude of the target fuel pressure P0. The amount of work required for the high-pressure fuel pump 4 changes, and the appropriate value for the feedforward term FF changes accordingly. That is, while the appropriate value changes depending on the magnitude of the target fuel pressure P0 in this way, in the above-described method of calculating the feedforward term FF, the calculated feedforward term FF is changed to the appropriate value. It cannot be changed correspondingly. This is presumed to be the cause of the above-mentioned problems.

  Therefore, depending on the magnitude of the target fuel pressure P0, the calculated feedforward term FF becomes inappropriate as the value having the above intention, and the high pressure fuel pump 4 is controlled based on the pump duty DT calculated including the feedforward term FF. When the drive control is performed, it becomes difficult to quickly converge the actual fuel pressure P to the target fuel pressure P0. In particular, under the special operating conditions such as immediately after starting the internal combustion engine or immediately after returning from the fuel cut, the decrease in convergence of the fuel pressure P with respect to the target fuel pressure P0 becomes remarkable.

  Next, the calculation of the feedforward term FF according to the present embodiment performed to suppress the above-described problem will be described in detail with reference to the flowchart of FIG. 5 showing a feedforward term calculation routine. The feedforward term calculation routine is executed through the electronic control unit 18 by, for example, an angle interruption for each predetermined crank angle.

  In this routine, first, an instruction value Q for the amount of fuel injected from the fuel injection valve 3 is calculated based on the above equation (1) (S101). Subsequently, the coefficient K1 is calculated based on the engine speed and the target fuel pressure P0 (S102). Then, the feedforward term FF is calculated using the above equation (5) based on the indicated value Q and the coefficient K1. The feedforward term FF becomes a large value as the coefficient K1 increases, and becomes a small value as the coefficient K1 decreases.

  In step S102, when calculating the coefficient K1, not only the engine speed but also the target fuel pressure P0 is taken into account. For this reason, the feedforward term FF is calculated in consideration of the target fuel pressure P0 in addition to the command value Q and the engine speed. By calculating the feedforward term FF in this way, even if an appropriate value as the value having the intent in the feedforward term FF changes according to the magnitude of the target fuel pressure P0, The calculated feedforward term FF can be changed. Therefore, the calculated feedforward term FF is not affected by the change in the target fuel pressure P0, and becomes an appropriate value having the above intention.

  Incidentally, the coefficient K1 is calculated in step S102 so as to increase as the target fuel pressure P0 increases as shown in FIG. 6 and decrease as the target fuel pressure P0 decreases.

  Here, as the target fuel pressure P0 increases, the work amount of the high-pressure fuel pump 4 required to control the actual fuel pressure P to the target fuel pressure P0 increases, and the above-mentioned intention in the feedforward term FF is accordingly obtained. The appropriate value is large. Further, the smaller the target fuel pressure P0, the smaller the work amount of the high-pressure fuel pump 4 required to control the actual fuel pressure P to the target fuel pressure P0. Accordingly, the above-mentioned intention in the feedforward term FF is obtained. The appropriate value is small.

  On the other hand, the feedforward term FF calculated as described above increases with an increase in the target fuel pressure P0 based on the change in the coefficient K1 with respect to the change in the target fuel pressure P0 shown in FIG. It becomes to decrease according to the decrease of. Therefore, when the appropriate value in the feedforward term FF changes according to the target fuel pressure P0, the calculated feedforward term FF can be accurately changed corresponding to the change in the appropriate value. it can.

According to the embodiment described in detail above, the following effects can be obtained.
(1) In calculating the feedforward term FF, not only the command value Q and the engine speed but also the target fuel pressure P0 is taken into account. For this reason, even if an appropriate value as the value having the intent in the feedforward term FF changes according to the target fuel pressure P0, the calculated feedforward term FF is changed according to the change in the appropriate value. Can be changed. More specifically, when the target fuel pressure P0 becomes large and the appropriate value becomes large, the feedforward term FF is increased accordingly, and when the target fuel pressure P0 becomes small and the appropriate value becomes small, the feed is increased. The forward term FF can be reduced accordingly. As described above, the feedforward term FF is set to an appropriate value having the above intention without being influenced by the change in the target fuel pressure P0. When the high pressure fuel pump 4 is driven and controlled based on the pump duty DT including the feedforward term FF, the actual fuel pressure P can be quickly converged to the target fuel pressure P0.

  (2) The feedforward term FF is calculated by multiplying the indicated value Q by a coefficient K1 that is variable according to the target fuel pressure P0. Therefore, the feedforward term FF can be accurately changed according to the magnitude of the target fuel pressure P0 by changing the coefficient K1 according to the target fuel pressure P0.

  (3) Since the amount of fuel injected from the fuel injection valve 3 varies depending on the engine load and various corrections, the amount of fuel commensurate with the fuel amount is a value intended to be supplied to the delivery pipe 13 in advance. A certain feedforward term FF also needs to be changed according to the engine load and various corrections. In consideration of this point, a base value “KL · Qmax” in which the indicated value Q of the fuel amount used for calculation of the feedforward term FF is a value corresponding to the engine load as shown in the equation (1). On the other hand, it is obtained by multiplying the correction coefficient H for performing the various corrections. Therefore, the calculated feedforward term FF can be changed according to the engine load and various corrections, and can be set to an appropriate value as the value having the intention.

In addition, about the said embodiment, it can also be changed as follows, for example.
The feedforward term FF is not necessarily calculated manually using Equation (5), but may be performed using other procedures.

The calculation of the instruction value Q is not necessarily performed using the equation (1), but can be performed using other procedures.
For the coefficient K1 used for calculating the feedforward term FF, the trend of the coefficient K2 with respect to the change in the target fuel pressure P0 does not necessarily have to be a linear trend as shown in FIG. You may make it take the tendency of a quadratic curve.

  It is not always necessary to include the integral term DTi in the pump duty DT.

1 is a schematic diagram showing an entire fuel supply system of an internal combustion engine to which a fuel pressure control device of an embodiment is applied. The timing chart which shows transition of the plunger lift amount of a high pressure fuel pump with respect to the change of a cam angle. The graph which shows the transition tendency of the target fuel pressure with respect to the change of engine load and engine speed. The time chart which shows how the actual fuel pressure changes when controlling an actual fuel pressure to a target fuel pressure. The flowchart which shows the calculation procedure of a feedforward term. A graph showing how the coefficient K1 used for calculating the feedforward term changes when the target fuel pressure P0 changes under the condition of constant engine speed.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel tank, 2 ... Feed pump, 3 ... Fuel injection valve, 4 ... High pressure fuel pump, 5 ... Cam shaft, 6 ... Cam, 7 ... Coil spring, 8 ... Plunger, 9 ... Cylinder, 10 ... Pressure chamber, DESCRIPTION OF SYMBOLS 11 ... Suction passage, 12 ... Discharge passage, 13 ... Delivery pipe, 14 ... Electromagnetic spill valve, 15 ... Electromagnetic solenoid, 17 ... Coil spring, 18 ... Electronic control unit (calculation means), 19 ... Fuel pressure sensor, 20 ... Crank position Sensor: 21 ... Cam position sensor, 22 ... Accelerator position sensor, 23 ... Throttle position sensor, 24 ... Air flow meter.

Claims (4)

A high-pressure fuel pump that discharges fuel toward a fuel pipe connected to the fuel injection valve of the internal combustion engine is provided, and a feed-forward term included in the drive command value of the high-pressure fuel pump is designated as an indication of the amount of fuel injected from the fuel injection valve The actual fuel pressure in the fuel pipe is set to the target fuel pressure by calculating the fuel discharge amount from the pump through the drive control of the high-pressure fuel pump based on the drive command value and calculating based on the value and the engine rotational speed. In a fuel pressure control device for an internal combustion engine to be controlled,
A fuel pressure control apparatus for an internal combustion engine, comprising: calculation means for calculating the feedforward term by taking into account the target fuel pressure in addition to an instruction value of the amount of fuel injected from the fuel injection valve and the engine speed. . The fuel pressure control device for an internal combustion engine according to claim 1, wherein the calculating means increases the feedforward term as the target fuel pressure increases, and decreases the feedforward term as the target fuel pressure decreases. The internal combustion engine according to claim 1 or 2, wherein the calculation means calculates the feedforward term by multiplying the indicated value by a coefficient, and makes the coefficient variable according to an engine speed and a target fuel pressure. Engine fuel pressure control device. The said calculation means uses what was obtained by adding various correction | amendments with respect to the base value calculated | required according to an engine load as said instruction | indication value, when calculating the said feedforward term. A fuel pressure control device for an internal combustion engine according to claim 1.

Images