JP2003035182A - Fuel-pressure control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel-pressure control device capable of suppressing torque shock or fluctuation in revolution, immediately after the operation finishing by fuel supply stop, such as fuel cut and also widening a lean combustion region. SOLUTION: The fuel pressure control device 100 controls the pressure of a fuel supplied from a high-pressure fuel pump 307 to an injector 304 via a pressure accumulation piping 303, and is provided with a condition materialization-determining means 101 for judging the shifting to a specified operation condition, such as fuel injection stop based on a prescribed parameter such as an engine revolution, a calculation means 102 for calculating, based on the parameter, a target fuel pressure value of the piping 303 immediately after terminating the specified operation condition, and a fuel supply control means 103 for forcibly stopping the fuel supply from the fuel pump 307 to the piping 303, in such a way that the pressure in the piping 303 reaches the above target value for an optional period during shifting to the specified operation condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel pressure control method and device for a direct injection engine, in which fuel is supplied from a high-pressure fuel pump to an injector via a pressure accumulating pipe section.

[0002]

2. Description of the Related Art In a conventional variable discharge high pressure fuel pump, for example, in Japanese Unexamined Patent Publication No. 10-153157, three passages communicate with a pump chamber. One is an inflow passage for letting the fuel into the low pressure fuel into the pump chamber, one is a supply passage for sending the high pressure fuel to the common rail (accumulation pipe portion), and one is a spill passage. A spill valve is connected to the spill passage, and the discharge amount is adjusted by controlling the spill amount to the fuel tank by opening / closing the spill valve. Further, for example, in Japanese Unexamined Patent Publication No. 2000-8997, when the pressure on the downstream side (pump side) of the suction valve is equal to or higher than the pressure on the upstream side (suction port side), the suction valve has a closing force. An engaging member that is biased to engage when the suction valve moves in the valve closing direction.
An actuator that applies an urging force in a direction opposite to the urging force to the engagement member by an external input is provided, and the fuel discharge amount is adjusted by opening and closing the intake valve.

[0003]

In such a high pressure fuel pump system of the prior art, the fuel pressure is adjusted so that the target fuel pressure value is obtained by the consumption amount (fuel injection amount) from the injector and the discharge supply amount from the pump. The opening and closing timings of the spill valve and the suction valve are controlled. Here, the fuel pressure is controlled by the balance between the supply amount and the consumption amount, but the actual pressure increase amount is the pump discharge amount, and the depressurization amount is performed by the consumption amount by the injector. The discharge from the pump is stopped, and only the consumption from the injector is used. Therefore, while the engine operating condition is fuel cut and fuel consumption is not performed, the relationship between supply and consumption is not established, so the fuel pressure increased up to immediately before is maintained and the fuel pressure is adjusted (lowered). ) Can be performed after recovery from fuel cut (return of fuel supply) (see FIG. 5 described later).

Here, the influence of the fuel pressure on the lean (stratified / lean) combustion is great, and it is necessary to perform (permit) the lean combustion under the fuel pressure at which the combustion is established. Even if the operating state is in the lean burn permission region during the fuel cut, the fuel pressure is controlled only after the recovery as described above, and therefore, there is a predetermined delay before it reaches the target fuel pressure value. Therefore, there is a problem in that even if a lean combustion is desired to be performed as an operating region for the purpose of improving fuel economy, it cannot be performed due to the limitation of the fuel pressure. Further, if it is in the steady stable region that the fuel pressure becomes close to the target fuel pressure value value after the recovery, the combustion switching is performed from there. There is a difference in the combustion efficiency and the torque amount between the homogeneous combustion and the lean combustion, and there is a concern that a torque shock and a fluctuation in the number of revolutions may significantly occur when switching the combustion.

By the way, in the in-cylinder injection engine in which the fuel is supplied from the high-pressure fuel pump to the injector through the pressure accumulating pipe portion as described above, when the condition for shifting to the fuel cut is satisfied, it is immediately performed. Since a torque shock may occur when performing fuel cut, normally, for example, after the fuel cut condition is satisfied, first, the fuel cut is performed for only half the cylinders, and then the fuel cut is performed for all the cylinders so that the torque is gradually reduced. As a result, the fuel cut (for all cylinders) is started after a predetermined period from the time when the condition is satisfied.

As described above, even when the timing of actually starting the fuel cut is delayed from the time when the fuel cut condition is satisfied, there is a problem that the fuel pressure immediately after the recovery (fuel supply return) does not reach the target fuel pressure value. However, as one measure for resolving such a problem, Japanese Patent Laid-Open No. 2000-18067 discloses a timing at which fuel cut is started after the fuel cut condition is satisfied until the fuel pressure reaches the target fuel pressure value. It has been proposed to delay. However, in the proposed measure, the period from the time when the fuel cut condition is satisfied to the time when the fuel cut is actually changed becomes long, which is not preferable for control.

The present invention has been made in view of the above problems, and an object thereof is to estimate in advance the timing of transition to a specific operating state where fuel injection such as fuel cut is not performed, and The pressure is controlled so that it becomes a fuel pressure value commensurate with the required combustion state immediately after the end of the specific operating state, to suppress torque shock and rotational speed fluctuation immediately after the end of fuel cut, etc. It is to provide a fuel pressure control device capable of expanding the fuel consumption.

[0008]

[Means for Solving the Problems] To achieve the above object,
One of the fuel pressure control devices according to the present invention is a fuel pressure control device provided in a cylinder injection type engine configured to supply fuel from a high-pressure fuel pump to an injector via a pressure accumulating pipe section. Based on a predetermined parameter such as the number of revolutions, condition satisfaction determining means for determining whether a condition for shifting to a specific operating state such as fuel cut in which fuel injection is not performed, and the condition satisfaction determining means are used to When it is determined that the condition for shifting to the specific operating state is satisfied, the target fuel pressure value of the pressure accumulating pipe section required immediately after the specific operating state is finished is calculated based on a predetermined parameter such as the engine speed. Target fuel pressure value calculating means, and any period from the time when the condition for shifting to the specific operating state is satisfied to the actual shifting to at least the specific operating state, Fuel supply control means for forcibly stopping the fuel supply from the high-pressure fuel pump to the pressure accumulation pipe section so that the fuel pressure in the pressure accumulation pipe section becomes the target fuel pressure value. I am trying.

Another one of the fuel pressure control devices according to the present invention is a fuel pressure control device provided in a cylinder injection engine adapted to supply fuel from a high pressure fuel pump to an injector through a pressure accumulating pipe section. And a transition predicting means for predicting in advance a transition to a specific operating state such as fuel cut in which fuel injection is not performed, based on a predetermined parameter such as engine speed, and the specific operation by the transition predicting means. When the transition to the state is predicted, the target fuel pressure value calculating means for calculating the target fuel pressure value of the pressure accumulating pipe section required immediately after the specific operation state is ended based on a predetermined parameter such as the engine speed. And an arbitrary period between the time when it is predicted to shift to the specific operating state and the actual shift to at least the specific operating state, the fuel pressure of the pressure accumulating pipe section. So it becomes the target fuel pressure value comprises a fuel supply control means for forcibly stopping the fuel supply to the accumulator pipe portion from the high pressure fuel pump.

The fuel supply control means preferably stops the fuel supply to the accumulator pipe section by returning the fuel from the pump chamber to the fuel tank side in the compression discharge stroke of the high pressure fuel pump. . In a more preferred aspect, the fuel supply control means includes an intake valve provided in a pump chamber of the high-pressure fuel pump, an actuator that can open the intake valve at an arbitrary timing, and an actuator drive that controls driving of the actuator. It consists of control means.

In a preferred aspect of the fuel pressure control device of the present invention, the fuel supply control means is configured to increase the high pressure at a time when a condition for shifting to the specific operating state is satisfied or at a time when it is predicted to shift to the specific operating state. The fuel supply from the fuel pump to the pressure accumulating pipe section is stopped.

Under such a configuration, for example, when the fuel cut condition is satisfied, the fuel supply from the high-pressure fuel pump to the accumulator piping is stopped, so that the fuel cut is actually performed after the fuel cut condition is satisfied. Until the start, the fuel pressure in the pressure accumulating pipe is reduced by the amount consumed by the fuel injection from the injector. Therefore, if the fuel supply to the accumulator pipe section is continued from the time when the fuel cut condition is satisfied to the time when the fuel cut is actually started as in the conventional case, the fuel immediately after the fuel cut is started and immediately after the fuel cut is completed. While the pressure is considerably higher than the target fuel pressure value required immediately after the fuel cut,
In the device of the present invention, the fuel pressure at the start of fuel cut and immediately after the end of fuel cut is brought close to the target fuel pressure value.

This makes it possible to secure an optimum fuel pressure at which lean combustion is achieved during recovery from fuel cut (recovery of fuel supply), and lean burn is immediately performed after returning from fuel cut. Therefore, the lean burn region can be expanded and the fuel consumption can be improved. Also, by starting recovery from fuel cut (recovery of fuel supply) with lean combustion, switching of combustion in the steady region can be eliminated, and it is possible to reduce torque shock and rotational speed fluctuation due to combustion difference. . Other preferable aspects of the fuel pressure control device according to the present invention will be listed below.

The fuel supply control means preferably supplies the fuel from the high pressure fuel pump to the pressure accumulating pipe so that the fuel pressure in the pressure accumulating pipe reaches the target fuel pressure value when the fuel pressure in the pressure accumulating pipe changes to the specific operating state. The timing of stopping the fuel supply is delayed from the time when the condition for shifting to the specific operating state is satisfied or from the time when it is predicted to shift to the specific operating state.

In this case, the fuel supply control means preferably sets the timing of stopping the fuel supply from the high-pressure fuel pump to the pressure accumulating pipe section to a time point when the condition for shifting to the specific operation state is satisfied or the specific time point. The fuel pressure in the pressure accumulating pipe section is expected to be reduced by the fuel injection from the injector from the time when it is predicted to shift to the operating state until the actual shift to the specific operating state.

In a more specific preferred embodiment, the fuel supply control means sets the fuel pressure decrease amount of the pressure accumulating pipe portion by one fuel injection of an injector and the fuel pressure of the pressure accumulating pipe portion to the target fuel pressure value. The number of injections required to lower the pressure is calculated, and the timing for stopping the fuel supply from the high-pressure fuel pump to the pressure accumulating pipe section is determined based on these. In this way, by delaying the timing of stopping the fuel supply, it is possible to prevent the fuel pressure from being excessively lowered, and to improve the control accuracy of the fuel pressure.

On the other hand, the migration predicting means is preferably
At least the engine speed and the rate of increase thereof are used as parameters to predict the transition to the specific operating state. In this manner, the transition predicting means estimates the transition to a specific operating state such as fuel cut under conditions other than the fuel cut condition, and sets the fuel supply stop timing to control the fuel pressure. The control can be started earlier than when the cutting conditions are satisfied, and the degree of control freedom is improved.

Further, preferably, the fuel supply control means releases the stop of the fuel supply from the high pressure fuel pump to the pressure accumulation pipe portion when the fuel pressure in the pressure accumulation pipe portion reaches the target fuel pressure value. To be done. Further, preferably, the fuel supply control means is configured to cancel the stop of the fuel supply when the acceleration state of the vehicle is detected even before the fuel pressure in the pressure accumulating pipe section reaches the target fuel pressure value. It

By doing so, the fuel pressure is prevented from being excessively lowered, and is maintained at the fuel pressure value adapted to the operating condition. Further, the target fuel pressure value is preferably set to a fuel pressure value that enables stratified combustion or lean combustion. As a result, it becomes possible to perform lean combustion early, that is, to start stratified combustion or lean combustion immediately after the end of fuel cut.

In a further preferred aspect, a fuel injection amount control means for controlling the fuel injection amount (driving pulse width = duty ratio) from the injector is additionally provided, and the fuel supply control means is used to connect the high pressure fuel pump to the accumulator pipe section. By stopping the fuel supply and controlling the fuel injection amount by the fuel injection amount control means, the fuel pressure in the pressure accumulating pipe section is controlled to the target fuel pressure value. As a result, the degree of control freedom and control accuracy are further improved.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a functional block diagram showing a basic configuration of an embodiment of a fuel pressure control device according to the present invention.

The fuel pressure control device 100 of the illustrated embodiment
Is provided in the in-cylinder injection engine 200 configured to supply fuel from the high-pressure fuel pump 307 to the injector 304 via the pressure accumulating pipe section (common rail) 303,
The basic configuration is a condition satisfaction determination means 101 for determining whether or not a condition for shifting to fuel cut is satisfied based on predetermined parameters such as engine speed, operating load, accelerator opening, vehicle speed, and the like. When the condition satisfaction determining means 101 determines that the condition for shifting to fuel cut is satisfied, it is requested immediately after the fuel cut is completed (at the time of recovery) based on predetermined parameters such as the engine speed and the operating load. The target fuel pressure value calculating means 102 for calculating the target fuel pressure value of the pressure accumulating pipe section 303, and at least an arbitrary period from the time when the condition for shifting to the fuel cut is satisfied to the actual shift to the fuel cut, So that the fuel pressure in the accumulator pipe section 303 becomes the target fuel pressure value,
Fuel supply control means 10 for forcibly stopping the fuel supply from the high-pressure fuel pump 307 to the accumulator pipe section 303.
3 and a fuel injection amount control means 104 for supplying a drive signal of a required duty ratio (pulse width) to the injector 304.

The fuel supply control means 103 controls the pump chamber 31 in the compression discharge stroke of the high-pressure fuel pump 307.
The fuel supply to the pressure accumulating pipe section 303 is stopped by returning the fuel from the No. 5 to the fuel tank 320 side, and the suction valve 311 provided in the pump chamber 315 of the high pressure fuel pump 307, Electromagnetic actuator 309 that can open the intake valve 311 at an arbitrary timing
And an actuator drive control means 105 for controlling the drive of the actuator 309.

The condition satisfaction determination means 101, the target fuel pressure value calculation means 102, the actuator drive control means 105 of the fuel supply control means 103, and the fuel injection amount control means 1
Reference numeral 04 is a concrete expression of a part of the program executed by the microcomputer incorporated in the control unit 301 by a functional block.

FIG. 2 shows a specific overall structure of the in-cylinder injection engine 200 and the fuel pressure control device 100 provided therein. The fuel pressure control device 100 includes a high pressure fuel pump 307 driven by the engine 200. The intake air introduced into the cylinder 229 is taken in from the inlet 219 of the air cleaner 220, passes through an air flow meter (air flow sensor) 218 which is one of engine operating condition measuring means, and controls the intake air flow. Throttle body 22 accommodating valve 224
Enter collector 223 through 1. From the air flow sensor 218, a signal representing the intake air flow rate is output to the control unit 301 which is an engine control device.

Further, the throttle body 221 has
A throttle sensor 217, which is one of engine operating condition measuring means for detecting the opening degree of the electronically controlled throttle valve 224, is attached, and the signal thereof is also output to the control unit 301. The collector 2
The air sucked into the cylinder 23 is distributed to each intake pipe 225 connected to each cylinder 229 of the engine 200, and then introduced into the combustion chamber 228 of the cylinder 229.

On the other hand, the fuel such as gasoline is stored in the fuel tank 320 as will be understood by referring to FIG. 3 in addition to FIG.
Is primarily pressurized by a low-pressure fuel pump 319, and a constant pressure (for example, 3 kg / c) by a fuel pressure regulator 318.
The pressure is adjusted to m ² ), and the high-pressure fuel pump 307 secondarily pressurizes the pressure to a higher pressure (for example, 50 kg / cm ² ) and pressure-feeds it to the pressure accumulating pipe section (common rail) 303. The high-pressure fuel is injected into the combustion chamber 228 from the injector 304 provided in each cylinder 229. The combustion chamber 22
The fuel injected at No. 8 is ignited at the ignition plug 215 by the ignition signal whose voltage has been increased by the ignition coil 211. Further, the cam angle sensor 207 attached to the camshaft 202 of the exhaust valve outputs a signal for detecting the phase of the camshaft 202 to the control unit 301. Here, the cam angle sensor may be attached to the camshaft on the intake valve side. Further, a crank angle sensor 230 is provided on the crankshaft axis to detect the rotation and phase of the crankshaft 240 of the engine, and its output is input to the control unit 301.

Further, the A / F sensor 208 provided upstream of the catalyst 210 in the exhaust pipe 209 detects the exhaust gas and outputs the detection signal to the control unit 301. The main part of the control unit 301 is shown in FIG.
As shown in, MPU402, ROM401, RAM4
03, an I / O LSI 404 including an A / D converter, and the like, which is one of the means for measuring (detecting) the operating state of the engine, and the fuel pressure sensor 3
Signals from various sensors including 02 are taken as inputs, predetermined arithmetic processing is executed, various control signals calculated as the arithmetic results are output, and each injector 30
4. A predetermined control signal is supplied to (the solenoid 309a of) the actuator 309 of the ignition coil 211 and the high-pressure pump 307 to execute fuel supply amount control, ignition timing control, and fuel pressure control.

2 and 3, the high-pressure fuel pump 307
An example of the configuration and operation of will be described. In the pump body 307A, the fuel suction passage 313, the discharge passage 306, the pressurizing chamber 31
5 is formed. The pressurizing chamber 315 has a plunger 3
14 is slidably held. A suction valve 311 and a discharge valve 316 are provided in the suction passage 313 and the discharge passage 306, respectively, which are held in one direction by springs 312 and 317, respectively, and serve as check valves that limit the flow direction of fuel. . An electromagnetic actuator 309 including a solenoid 309a, a suction element 309b, a spring 308, and a plunger-type engagement member 310 is held by the pump body 307A. The engaging member 310 is the solenoid 3
When the energization of 09a is OFF, the spring 308 applies a biasing force to the intake valve 311 in the opening direction. Spring 3
Since the biasing force of 08 is larger than the biasing force of the suction valve spring 312, the suction valve 311 is in the open state when the energization of the solenoid 309a is OFF. Fuel is supplied from the tank 320 to the pump main body 307 by the low pressure pump 319.
The pressure regulator 318 regulates and guides the fuel at the fuel inlet A at a constant pressure. Then, it is pressurized by the pump main body 307A and is pressure-fed to the pressure accumulating pipe section (common rail) 303 through the fuel discharge passage 306.
An injector 304, a relief valve 305, and a pressure sensor 302 are attached to the pressure accumulating pipe section 303. The injectors 304 are mounted according to the number of cylinders of the engine, and the fuel injection amount is controlled by a drive signal from the control unit 301 of the engine. Also,
The relief valve 305 opens when the pressure inside the pressure accumulating pipe section 303 exceeds a predetermined value, and prevents damage to the piping system. The operation of the above configuration will be described below.

The lifter 321 provided at the lower end of the plunger 314 is pressed against the cam 202 by a spring 322. The plunger 314 reciprocates by the cam 202 rotated by a cam shaft of an intake valve or an exhaust valve of the engine, and changes the volume in the pump chamber 315. When the intake valve 311 is closed during the compression stroke of the pump chamber 315 in which the plunger 314 is raised, the pressure in the pump chamber 315 rises, which causes the discharge valve 316 to automatically open and the fuel to be accumulated in the pressure accumulating pipe section 303. Send by pressure.

The suction valve 311 automatically opens when the pressure in the pump chamber 315 becomes lower than the fuel introduction port, but the closing of the suction valve 311 is determined by the operation of the solenoid 309a. When the solenoid 309a maintains the ON (energized) state, an electromagnetic force equal to or greater than the biasing force of the spring 308 is generated to draw the engaging member 310 toward the suction element 309b, so that the engaging member 310 and the suction valve 311 are separated. To be done. In this state, the suction valve 311 is an automatic valve that opens and closes in synchronization with the reciprocating motion of the plunger 314. Therefore, during the compression stroke, the intake valve 311 is closed, and the fuel corresponding to the decrease in the volume of the pump chamber 315 pushes the discharge valve 316 open and the pressure accumulation pipe portion 303.
Pumped to. Therefore, the maximum discharge of the pump can be performed regardless of the response of the solenoid 309a.

On the other hand, the solenoid 309a is turned off.
When (non-energized) is maintained, the engaging member 310 engages with the intake valve 311 by the biasing force of the spring 308, and the intake valve 3
11 is kept open. Therefore, even during the compression stroke, the pressure in the pump chamber 315 maintains a low pressure state that is substantially the same as that in the fuel inlet port, so the discharge valve 316 cannot be opened, and the amount of fuel corresponding to the decrease in the volume of the pump chamber 315 cannot be released. , And is returned to the fuel introduction port side (fuel tank 320 side) through the suction valve 311. Therefore, the pump discharge amount can be zero.

During the compression stroke, the solenoid 30
If 9a is turned on, the accumulator pipe section 3 starts from this time.
Fuel is pumped to 03. Further, once the pressure feeding is started, the pressure in the pump chamber 315 rises. Therefore, even if the solenoid 309a is turned off thereafter, the suction valve 311 maintains the closed state and is automatically opened in synchronization with the start of the suction stroke. Speak. Therefore, the discharge amount (supply amount to the pressure accumulating pipe section 303) can be adjusted by the ON timing of the solenoid 309a.

As described above, by controlling the ON time or ON timing of the solenoid 309a in the compression stroke, the discharge amount to the pressure accumulating pipe section 303 can be variably controlled. Further, the control unit 301 calculates an appropriate discharge timing based on the signal from the pressure sensor 302 and controls the solenoid 309a, so that the fuel pressure in the pressure accumulating pipe section 303 can be feedback-controlled to the target fuel pressure value.

FIG. 6 shows a time chart of the fuel pressure change when a fuel cut occurs in the conventional fuel pressure control device. In the high-pressure fuel pump, since the discharge amount is variably controlled as described above to control the fuel supply to the injector,
The fuel pressure that has been boosted once can be reduced only by the consumption from the injector. In the normal injection state (up to point a in the figure), there is consumption (fuel injection) from the injector, so by controlling the discharge amount from the pump, the fuel pressure in the pressure accumulating pipe section is adjusted to the required fuel pressure. .

While the fuel cut condition is satisfied (a in the figure)
During (b), the fuel injection from the injector is stopped and the consumption is stopped, so the fuel pressure immediately before the fuel cut is maintained. As shown in FIG. 7, the target fuel pressure is set by a map using parameters such as engine speed and load. Therefore, if the engine speed decreases due to fuel cut, the operating range changes and The fuel pressure naturally changes to a value that satisfies the combustion set in the operating range (A → B in the figure). However, as described above, the technique for reducing the fuel pressure is the consumption from the injector, and since the control to the target fuel pressure can be performed only after the fuel supply is restored from the fuel cut, the actual fuel pressure has the behavior shown by the broken line. . At the point b in the figure, from the operating state, even if it is desired to start the stratified charge combustion, the fuel pressure at which the combustion is established is not established, so that the stratified charge combustion can actually be started in the figure
It will be after the point.

In the stratified charge combustion, the fuel injected from the injector is ignited when the fuel is transported to the vicinity of the spark plug in the cylinder, so that the combustion is established. Therefore, the combination of the ignition timing and the injection timing is shown in FIG. Such a combustion stable region is determined. The allowable combustion stability region is narrow, and even if only the injection timing is changed, the combustion stability deteriorates rapidly. Therefore, these must be precisely controlled in each operating state. Here, the influence of the fuel pressure on the stratified charge combustion is large, and an example thereof is shown in FIG. In each operating state such as the idle state and the partial state, the fuel pressure range below the surge limit is different. This is because the penetration force (penetration) and atomization characteristics of the fuel injected from the injector change depending on the fuel pressure, and it is necessary to precisely control the ignition timing and the injection timing. At point b shown in FIG. 6, if stratified charge combustion is started in a state where the fuel pressure is outside the combustible range, various problems such as exhaust deterioration due to misfire, rotational fluctuation, and torque shock occur. I will end up. According to the present invention, in this part, the fuel pressure is always set to the optimum value in the operation region where the stratified charge combustion can be realized in terms of the output torque, so that the constraint of the responsiveness of the fuel pressure control can be eliminated, and the original fuel consumption, It is possible to expand the stratified charge combustion operation range that is performed for the purpose of improving exhaust performance. FIG. 10 shows an example of a time chart of fuel pressure control in the embodiment of the present invention.

Conventionally, the fuel pressure during fuel cut is maintained at the pressure immediately before that, so even if it is desired to realize stratified charge combustion at the time of fuel cut recovery, the fuel pressure does not reach the combustion request fuel, and therefore the predetermined time is required. After the delay of S, stratified charge combustion will be started. In the embodiment of the present invention, when the fuel cut condition is satisfied, the fuel pressure securing request is generated, and the fuel pressure at which the combustion is established when the fuel supply is restored from the fuel cut while the fuel pressure is controllable Is ensured and the behavior of the fuel pressure shown by the broken line in the figure is realized. In other words, the target fuel pressure value of the pressure accumulating pipe section 303 required immediately after the fuel cut is completed (when the fuel supply is restored) is calculated based on a predetermined parameter such as the engine speed, and when the fuel cut condition is satisfied. During the period from the actual shift to the fuel cut, the fuel supply from the high-pressure fuel pump 307 to the pressure accumulation pipe section 303 is forcibly stopped so that the fuel pressure of the pressure accumulation pipe section 303 becomes the target fuel pressure value. Let As a result, stratified charge combustion becomes possible when the fuel supply is restored from the fuel cut, and the stratified charge region can be expanded as compared with the conventional case. The combustion performed here is not limited to stratified combustion, but may be homogeneous lean combustion.

FIG. 11 shows an example of a control time chart during the fuel pressure securing request. When the fuel cut condition is satisfied, the fuel cut is not started immediately due to the driveability requirement such as torque shock, but after the condition is satisfied, it is necessary to continue the normal fuel injection for a predetermined time or a predetermined number of injections. If there is, fuel cut is performed only for a predetermined cylinder, and then fuel cut for all cylinders is started to avoid a sudden change in output torque.
Conventionally, while the fuel consumption from the injector was present, the drive pulse to the discharge amount control solenoid of the high-pressure fuel pump was always output until just before the fuel cut for all cylinders in order to set the fuel pressure to the target value. In the mode, the solenoid drive pulse is stopped when the fuel cut condition is satisfied. Since the fuel is consumed by the above-described normal injection after the fuel cut condition is satisfied or the fuel is injected into the cylinders outside the predetermined cylinder, the pressure of X decreases at the time of starting the fuel cut for all cylinders at point C in the figure. As described above, in the embodiment of the present invention, the fuel pressure is lowered by breaking the relationship between the fuel supply and the consumption by the pump and the injector, and the fuel pressure required for the combustion is secured when the fuel supply is restored from the fuel cut. .

FIG. 12 shows an example of a control time chart during a request for securing fuel pressure with delay (request for stopping fuel supply to the pressure accumulating pipe section 303). Actuator 30
No. 9 drive pulse to the solenoid 309a, in other words, the stop of fuel supply from the high-pressure fuel pump 307 to the pressure accumulating pipe section 303 is delayed for a predetermined time rather than when the fuel cut condition is satisfied (point A in the figure). This is an example of stopping at the middle A'point. When the drive pulse from the point A to the solenoid 309a is stopped, the fuel pressure may decrease as indicated by the broken line in the figure, and may fall below the surge limit fuel pressure upper limit of homogeneous combustion. This makes combustion unstable and causes exhaust and torque shock.
Therefore, it is necessary to secure at least the establishment of combustion until the fuel cut is started. By providing the delay, it is possible to prevent the fuel pressure from being excessively lowered due to the fuel injection performed until all cylinders are cut, and the combustion not being established.

FIG. 13 is a flowchart showing an example of a program for realizing the control shown in the time charts of FIGS. 11 and 12. First, in step S11, it is determined whether the fuel cut condition is satisfied. If the fuel cut condition is satisfied, then the fuel pressure is reduced by one fuel injection based on the injection pulse width (injection amount) currently injected from the injector 304. The amount is calculated (step S12). Injection pulse width (injection amount)
The relationship between the fuel pressure decrease amount and the fuel pressure decrease amount is determined based on the injector characteristics, the common rail pipe volume, and the like, and may be set as a table value in advance as shown in FIG. 14, instead of being calculated by calculation. Next, the target reduced fuel pressure amount is calculated (step S13). As shown in FIG. 14, the fuel pressure range in which combustion is established in each combustion and operating state is fixed, so it is necessary to secure it until the fuel cut for all cylinders is started. Therefore, the target reduced fuel pressure amount is calculated up to the fuel pressure that can realize the current combustion from the current fuel pressure and that satisfies the combustion request after the fuel cut is restored. The required number of injections (A) that indicates how many injections are necessary only to satisfy the target reduced fuel pressure amount with the fuel pressure reduction amount due to the fuel injection amount from these injectors in step S
Calculate with 14. Next, the number of injections (B) from the satisfaction of the fuel cut condition to the start of fuel cut for all cylinders is calculated based on the engine speed in consideration of the fuel cut for the specific cylinder and the like (step S15). In step S16,
Comparison of (A) and (B), the number of injections until the start of all cylinder cuts
If (B) is large, a process of stopping the drive pulse to the solenoid 309a after the lapse of the predetermined delay A, that is, a process of forcibly stopping the fuel supply from the high-pressure fuel pump 307 to the pressure accumulating pipe section 303 is performed (step S17). ). On the contrary, if the required number of injections (A) is large, the drive pulse is immediately stopped to reduce the fuel pressure (step S18). Here, it may be considered that the target fuel pressure cannot be reduced by the start of all cylinder cuts only by stopping the drive pulse of the solenoid 309a. However, the amount that cannot be covered by the number of times is also included in the fuel injection amount control. It is also possible to operate (increase) the fuel injection amount for each injection.

As a result, the fuel pressure is lowered while ensuring the combustion feasibility from the fuel cut condition being satisfied, and at the same time, the required fuel pressure (target fuel pressure value) such as stratified combustion after the fuel supply is restored from the fuel cut. Can be secured. Here, when the combustion after the fuel supply is restored from the fuel cut is not stratified combustion, for example, when an acceleration request by the driver's accelerator operation occurs during the fuel cut, torque is requested, so normal combustion is not used but lean combustion. According to the embodiment of the present invention, when the fuel cut is restored by the homogeneous combustion, the fuel pressure that ensures the combustion immediately before the fuel cut is secured, and in the homogeneous combustion, the influence of the fuel pressure on the combustion is small (sensitivity). However, there is no problem with drivability and exhaust performance.

FIG. 16 is a functional block diagram showing the basic structure of another embodiment of the fuel pressure control system according to the present invention. In the fuel pressure control device 150 of the illustrated embodiment, fuel is fed from the high-pressure fuel pump 307 to a pressure accumulating pipe section (common rail).
The in-cylinder injection engine 200 is configured to be supplied to the injector 304 via 303, and the basic configuration thereof includes a transition predicting means 107 instead of the condition satisfaction determining means 101 of FIG. It has a similar structure.

The shift predicting means 107 predicts the shift to fuel cut in advance based on predetermined parameters such as the engine speed and its rate of increase, operating load, accelerator opening, vehicle speed, and gear position. When the transition predicting means 107 predicts the transition to the fuel cut, the target fuel pressure value calculating means calculates the pressure accumulation required immediately after the fuel cut is completed based on a predetermined parameter such as the engine speed. The fuel of the pressure accumulating pipe section 303 is calculated during the period from the time when the fuel supply control means 103 calculates the target fuel pressure value of the pipe section 303 to the time when the fuel supply control means 103 predicts that the fuel cut will occur, until the fuel cut actually occurs. The fuel supply from the high-pressure fuel pump 307 to the pressure accumulating pipe section 303 is forcibly stopped so that the pressure reaches the target fuel pressure value. FIG. 17 shows an example of a time chart of the fuel pressure securing request (fuel supply stop request to the pressure accumulating pipe section 303) in the fuel cut condition satisfaction prediction performed under such a configuration.

The driving condition is, for example, a downshift operation in a state where the driver releases his / her foot from the accelerator (coast) while traveling. Idle SW is switched from OFF to ON by releasing the foot
Becomes After that, when the gear is downshifted from the 3rd speed to the 2nd speed for the purpose of engine braking or the like, the low speed is set, so that the engine speed starts to increase after the point A. When this state continuously exceeds the predetermined engine speed defined by the fuel cut condition, the fuel cut is permitted (started) as indicated by point C in the figure. In the present embodiment, it is possible to predict the shift from the operating state or the like to the fuel cut before this fuel cut, and to perform the fuel pressure control (stop the fuel supply to the pressure accumulation pipe section 303). From the downshift until the engine speed exceeds the fuel cut permission engine speed (between A and C in the figure), the fuel cut is predicted by the engine speed, its rate of increase (rate of increase), and other operating parameters. The drive pulse to the solenoid 309a is stopped, that is, the fuel supply from the high-pressure fuel pump 307 to the pressure accumulating pipe section 303 is stopped (point B in the figure). As a result, the fuel supply is cut off and the fuel is consumed only from the injector 304, so that the fuel pressure is reduced in proportion to the consumed amount. In this operation, at the start of fuel cut, the fuel pressure X in the steady state is reduced to a value of Y, and the fuel pressure required for combustion at the time of fuel cut recovery is secured or kept close to the required value. This is the intention. Of course, the value of fuel pressure to be reduced is
Perform within the range where combustion before the fuel cut is established.

FIG. 18 is a flowchart showing an example of a fuel pressure control start determination program based on fuel cut prediction. First, in step S21, it is determined from the engine speed, accelerator opening, engine water temperature, engine load, and the like that a condition other than the engine speed is satisfied in the fuel cut condition. That is, if the engine speed continues to increase, it is determined that the fuel cut is always performed. Next, in order to determine the minimum allowable value of the fuel pressure that can secure the current combustion, it is determined here whether the engine speed is equal to or higher than a predetermined speed using a threshold value (step S22). Next, it is determined that the engine speed increase rate (Δ rotation) is equal to or greater than a predetermined value, and it is determined that a fuel cut will occur (step 2).
3). When these conditions are satisfied, the fuel pressure is reduced and secured by the fuel pressure control (step 24).

FIG. 19 is a flow chart showing an example of the program for determining the end of fuel pressure control based on fuel cut prediction. Basically, the state where the fuel cut condition is released is determined by acceleration determination or the like, and the fuel pressure control is ended, that is, the stop of the fuel supply from the high pressure fuel pump 307 to the pressure accumulating pipe section 309 is released (steps S31, S34). ). Also,
In the fuel pressure control of the present invention, even if the actual fuel pressure is unintentionally lowered to a predetermined pressure or less, the combustion cannot be ensured in the same manner, so the control is terminated (fuel supply stop cancellation) (steps S32 and S34). ). Also, when fuel pressure control is started by predicting fuel cut, but fuel pressure control is also performed when it is determined that fuel cut will not be performed afterwards because the speed of increase in engine speed has fallen below a certain value. It is ended (steps S33 and S34). Although some embodiments of the control device of the present invention have been described in detail above, the present invention is not limited to the above embodiments,
Various modifications can be made in the design without departing from the spirit of the invention described in the claims.

[0048]

According to the present invention, by predicting the next operating state in advance and securing the fuel pressure near a predetermined value, lean combustion can be realized from the time of recovery from fuel cut, for example. Therefore, the operating range of the lean combustion can be expanded, and the conventional operation of once changing the homogeneous combustion to the lean combustion after the recovery is unnecessary, so that it is possible to eliminate the rotational speed fluctuation and the torque shock due to the switching.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing a basic configuration of an embodiment of a fuel pressure control device according to the present invention.

FIG. 2 is an overall configuration diagram showing a cylinder injection engine and a fuel pressure control device provided therein.

FIG. 3 is a diagram showing an example of the configuration and operation of a high-pressure fuel pump.

FIG. 4 is a diagram showing a detailed configuration of a high-pressure fuel pump.

FIG. 5 is a diagram showing an example of a main part of a control unit.

FIG. 6 is a time chart showing an example of a change in fuel pressure when a fuel cut occurs in the related art.

FIG. 7 is a diagram showing an example of setting a target fuel pressure value.

FIG. 8 is a diagram showing an example of a combustion stable region in a direct injection engine.

FIG. 9 is a diagram provided for explaining the influence of fuel pressure on stratified charge combustion.

FIG. 10 is a time chart showing an example of fuel pressure control of the present invention.

FIG. 11 is a time chart showing an example of fuel pressure control during a fuel pressure securing request.

FIG. 12 is a time chart showing an example of fuel pressure control during a fuel securing request with delay.

FIG. 13 is a flowchart showing an example of a program that realizes the control of FIGS. 11 and 12.

FIG. 14 is a graph showing a relationship between an injection pulse width (injection amount) and a fuel pressure decrease amount.

FIG. 15 is a graph showing a fuel pressure range in which combustion is established in each combustion operation state.

FIG. 16 is a functional block diagram showing the basic configuration of another embodiment of the fuel pressure control device according to the present invention.

FIG. 17 is a time chart showing an example of fuel pressure control in prediction of satisfaction of a fuel cut condition.

FIG. 18 is a flowchart showing an example of a fuel pressure control start determination program based on fuel cut prediction.

FIG. 19 is an example of a flowchart showing an example of a fuel pressure control end determination program based on fuel cut prediction.

[Explanation of symbols]

100 ... Fuel pressure control device 101 ... Confirmation condition determination means 102: Target fuel pressure value determination means 103 ... Fuel supply control means 104 ... Fuel injection amount control means 105 ... Actuator drive control means 107 ... Transition prediction means 200 ... In-cylinder injection engine 207 ... Cam angle sensor 208 ... A / F sensor 209 ... Exhaust pipe 210 ... Catalyst 211 ... Ignition coil 215 ... Spark plug 217 ... Throttle sensor 218 ... Air flow meter (air flow sensor) 220 ... Air cleaner 221 ... Throttle body 223 ... Collector 224: Electric throttle valve 225 ... Intake pipe 228 ... Combustion chamber 229 ... Cylinder 230 ... crank angle sensor 301 ... Control unit 302 ... Fuel pressure sensor 303 ... Accumulation pipe section (common rail) 304 ... Injector 305 ... Relief valve 306 ... Fuel discharge passage 307 ... High-pressure fuel pump 308, 312, 317 ... Spring 309 ... Electromagnetic actuator 309a ... Solenoid 310 ... Engaging member 311 ... Suction valve 313 ... Fuel intake passage 314 ... Plunger 315 ... Pump chamber (pressurizing chamber) 316 ... Discharge valve 318 ... Fuel pressure regulator 319 ... Low-pressure fuel pump 320 ... Fuel tank

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI theme code (reference) F02M 59/34 F02M 59/34 59/36 59/36 (72) Inventor Nobuhiro Akasaka Hitachinaka City, Ibaraki Field 2520 Stock company Hitachi Ltd. Automotive equipment group (72) Inventor Takashi Okamoto Takara, Hitachi, Ibaraki Prefecture Takara Takaba 2520 Stock company Hitachi Ltd. Automotive equipment group F term (reference) 3G066 AA02 AB02 AD12 BA00 BA19 CA01S CA04U CA09 CA20U CB01 CB12 CC01 CD03 CD25 CD26 CE02 CE22 DA01 DA06 DB16 DB17 DC00 DC04 DC05 DC09 DC11 DC18 DC24 DC26 3G301 HA04 HA06 HA15 HA16 JA04 KA15 KA16 LB06 LB16 LB17 LC01 MA01 MA11 MA24 MA25 MA28 NA08 ND14 NE21 ND02 ND02 ND02 ND07 ND07 ND02 ND02 ND02 NEND PB03Z PB08A PB08Z PD02Z PE01Z PE03Z PF01Z PF03Z PF16Z

Claims (13)

[Claims] 1. A fuel pressure control device provided in a cylinder injection type engine adapted to supply fuel from a high-pressure fuel pump to an injector via a pressure accumulating pipe section, wherein a predetermined parameter such as engine speed is set. Based on the conditions, a condition satisfaction determining means for determining whether or not a condition for shifting to a specific operating state such as a fuel cut in which fuel injection is not performed and a condition for shifting to the specific operating state by the condition satisfaction determining means are provided. When it is determined that it has been established, based on a predetermined parameter such as the engine speed, a target fuel pressure value calculating means for calculating a target fuel pressure value of the pressure accumulating pipe section required immediately after the specific operation state is finished, The fuel pressure of the accumulator pipe section is any period between the time when the condition for shifting to the specific operating state is satisfied and the actual shift to at least the specific operating state. So that it becomes the target fuel pressure value,
And a fuel supply control unit for forcibly stopping the fuel supply from the high-pressure fuel pump to the accumulator pipe section. 2. A fuel pressure control device provided in a cylinder injection type engine adapted to supply fuel from a high pressure fuel pump to an injector through a pressure accumulating pipe section, wherein a predetermined parameter such as engine speed is set. Based on the transition prediction means for predicting a transition to a specific operation state such as fuel cut in which fuel injection is not performed in advance, and when the transition prediction means predicts a transition to the specific operation state, the engine speed Based on a predetermined parameter such as, the target fuel pressure value calculation means for calculating the target fuel pressure value of the pressure accumulating pipe section required immediately after the specific operation state is finished, and it is predicted to shift to the specific operation state. At any time from the time when the fuel pressure in the accumulator pipe section reaches the target fuel pressure value for at least an arbitrary period from the time when the fuel pressure in the accumulator pipe section actually shifts to the specific operating state. Fuel supply control means for forcibly stopping the fuel supply from the fuel pump to the accumulator pipe section,
A fuel pressure control device comprising: 3. The fuel supply control means stops the fuel supply to the accumulator pipe section by returning the fuel from the pump chamber to the fuel tank side in the compression discharge stroke of the high pressure fuel pump. Claim 1 characterized by the above.
Or the fuel pressure control device according to item 2. 4. The fuel supply control means comprises an intake valve provided in a pump chamber of the high-pressure fuel pump, an actuator capable of opening the intake valve at an arbitrary timing, and an actuator drive for controlling the drive of the actuator. The fuel pressure control device according to any one of claims 1 to 3, further comprising a control means. 5. The fuel supply control means feeds fuel from the high pressure fuel pump to the accumulator pipe section at a time when a condition for shifting to the specific operating state is satisfied or at a time when it is predicted to shift to the specific operating state. The fuel pressure control device according to any one of claims 1 to 4, wherein the supply is stopped. 6. The fuel supply control means supplies fuel from the high-pressure fuel pump to the pressure accumulation pipe so that the fuel pressure in the pressure accumulation pipe reaches the target fuel pressure value when the fuel pressure in the pressure accumulation pipe changes to the specific operating state. The timing for stopping the supply is delayed from a time point when a condition for shifting to the specific operation state is satisfied or a time point when it is predicted to shift to the specific operation state.
5. The fuel pressure control device according to claim 4. 7. The fuel supply control means shifts the timing of stopping the fuel supply from the high-pressure fuel pump to the accumulator pipe section to a time point when a condition for shifting to the specific operation state is satisfied or to the specific operation state. Then, from the time predicted to actually shift to the specific operating state,
7. The fuel pressure control device according to claim 6, wherein the fuel pressure control device is configured to determine a decrease in fuel pressure in the pressure accumulating pipe portion due to fuel injection from an injector. 8. The fuel supply control means is required to reduce the fuel pressure decrease amount in the pressure accumulating pipe portion by one fuel injection of an injector and the fuel pressure in the pressure accumulating pipe portion to the target fuel pressure value. The number of injections performed is calculated, and the timing for stopping the fuel supply from the high-pressure fuel pump to the accumulator pipe section is determined based on the calculated number of injections. A fuel pressure control device as described. 9. The shift predicting means is adapted to predict a shift to the specific operating state by using at least an engine speed and an increase rate thereof as parameters. A fuel pressure control device as described. 10. The fuel supply control means releases the stop of fuel supply from the high pressure fuel pump to the pressure accumulation pipe section when the fuel pressure in the pressure accumulation pipe section reaches the target fuel pressure value. The fuel pressure control device according to claim 1, wherein the fuel pressure control device is a fuel pressure control device. 11. The fuel supply control means releases the stop of the fuel supply when an acceleration state of the vehicle is detected even before the fuel pressure in the pressure accumulating pipe section reaches the target fuel pressure value. The fuel pressure control device according to claim 10. 12. The fuel pressure control device according to claim 1, wherein the target fuel pressure value is set to a fuel pressure value that enables stratified combustion or lean combustion. 13. A fuel injection amount control means for controlling the fuel injection amount from the injector is additionally provided, and the fuel supply control means stops the fuel supply from the high-pressure fuel pump to the accumulator pipe section and controls the fuel injection amount. 13. The control of the fuel injection amount by means for controlling the fuel pressure in the pressure accumulating pipe section to the target fuel pressure value is performed. Fuel pressure control device.