JP2008008298A - Fuel pressure control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain a torque shock and a rotating speed change immediately after finishing fuel cut. <P>SOLUTION: This fuel pressure control device 100 of a cylinder injection type engine supplies fuel to an injector 304 via a pressure accumulating pipe part 303 from a high-pressure fuel pump 307, and has a condition satisfaction determining means 101 shifted to a specific operation state such as the fuel cut without performing fuel injection on the basis of a predetermined parameter such as an engine speed, a target fuel pressure value calculating means 102 calculating a target fuel pressure value of the pressure accumulating pipe 303 requested immediately after finishing the specific operation state, and a fuel supply control means 103 forcibly stopping fuel supply to the pressure accumulating pipe 303 from the high pressure fuel pump 307 so that the fuel pressure of the pressure accumulating pipe 303 reaches the target fuel pressure value for an optional period up to actually be shifted to its specific operation state from when a condition of a shift to the specific operation state is satisfied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel pressure control method and apparatus in a direct injection engine in which fuel is supplied from a high-pressure fuel pump to an injector via a pressure accumulating pipe section.

  In a conventional variable discharge high pressure fuel pump, for example, in Japanese Patent Laid-Open No. 10-153157, three passages communicate with the pump chamber. One is an inflow passage through which low-pressure fuel flows into the pump chamber, one is a supply passage for sending high-pressure fuel to a common rail (accumulation piping section), 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 and closing the spill valve. Further, for example, in Japanese Patent Laid-Open 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 closing force is applied to the suction valve. An engagement member which is given a biasing force so as to engage when the suction valve moves in the valve closing direction, and engages a biasing force in a direction opposite to the biasing force by an external input. An actuator that acts on the member is provided, and the fuel discharge amount is adjusted by opening and closing the intake valve.

  In such a conventional high-pressure fuel pump system, the fuel pressure is adjusted by adjusting the consumption of the injector (fuel injection amount) and the discharge supply amount from the pump to the target fuel pressure value. The opening and closing timing is controlled. Here, the fuel pressure is controlled by the balance between the supply amount and the consumption amount, but the actual pressure increase is the pump discharge amount, and the pressure reduction is performed by the consumption amount by the injector. Discharging from the pump is stopped, and only the consumption from the injector is performed. For this reason, the relationship between supply and consumption is not established while the engine is operating under fuel cut and fuel consumption is not performed. Therefore, the fuel pressure increased until just before is maintained, and the fuel pressure is adjusted (decreased). ) Can be performed after recovery from fuel cut (return of fuel supply) (see FIG. 5 described later).

  Here, the influence of fuel pressure on lean (stratified / lean) combustion is large, and it is necessary to perform (permit) lean combustion under the fuel pressure at which combustion is established. Even if the operating state becomes the lean combustion permission region during the fuel cut, the fuel pressure is controlled only after the recovery as described above, so that a predetermined delay occurs before it becomes the target fuel pressure value. Therefore, there is a problem that even if the operation region is a region where lean combustion is desired to be performed for the purpose of improving fuel efficiency, it cannot be performed due to fuel pressure limitation. Further, if the fuel pressure is in the vicinity of the target fuel pressure value after recovery is in the steady stable region, combustion switching is performed from there. There is a difference in combustion efficiency and torque amount between homogeneous combustion and lean combustion, and there is a concern that torque shock and rotational speed fluctuations may be noticeable when switching 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 accumulator piping as described above, the fuel cut is immediately performed when the condition for shifting to the fuel cut is satisfied. If this is done, a torque shock may occur. Normally, for example, after the fuel cut condition is satisfied, first, only half of the cylinders are cut and then all cylinders are cut. Thus, 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 actual fuel cut start time is delayed from the time when the fuel cut condition is satisfied, there is a problem that the fuel pressure immediately after the recovery (return of fuel supply) does not reach the target fuel pressure value. As one measure for solving this problem, Japanese Patent Laid-Open No. 2000-18067 discloses that after the fuel cut condition is established, the fuel cut start time is delayed until the fuel pressure reaches the target fuel pressure value. It has been proposed to

  However, such a proposed measure is not preferable in terms of control because the period from when the fuel cut condition is satisfied until when the fuel cut condition is actually shifted to becomes longer.

  The present invention has been made in view of such a problem. The object of the present invention is to preliminarily estimate the timing for shifting to a specific operating state in which fuel injection such as fuel cut is not performed, and to determine the fuel pressure. Controls the fuel pressure value to match the required combustion state immediately after the end of a specific operating state, thereby suppressing torque shock and rotational speed fluctuation immediately after the end of fuel cut, etc., and expanding the lean combustion region A fuel pressure control device is provided.

  In order to achieve the above object, one of the fuel pressure control devices according to the present invention is a fuel pressure provided in a direct injection engine configured to supply fuel from a high-pressure fuel pump to an injector through a pressure accumulating pipe section. A condition establishment determination means for determining whether or not a condition for shifting to a specific operation state such as a fuel cut in which fuel injection is not performed is established based on a predetermined parameter such as an engine speed, When it is determined by the condition establishment determination means that the condition for shifting to the specific operation state is satisfied, the pressure accumulation pipe required immediately after the specific operation state is ended based on a predetermined parameter such as an engine speed The target fuel pressure value calculating means for calculating the target fuel pressure value of the part, and at least the specific operating state is actually transferred from the time when the condition for shifting to the specific operating state is satisfied Fuel supply control means for forcibly stopping fuel supply from the high-pressure fuel pump to the pressure accumulation piping section so that the fuel pressure of the pressure accumulation piping section becomes the target fuel pressure value for an arbitrary period between It is characterized by comprising.

  Another one of the fuel pressure control devices according to the present invention is a fuel pressure control device provided in an in-cylinder injection engine that is configured to supply fuel from a high-pressure fuel pump to an injector through a pressure accumulating pipe section. A transition predicting means for predicting in advance a transition to a specific operating state such as a fuel cut in which fuel injection is not performed, based on a predetermined parameter such as the engine speed, and the transition predicting means 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 ended based on a predetermined parameter such as an engine speed when the transition is predicted; The fuel pressure in the pressure accumulating piping section is the target during an arbitrary period from the time when it is predicted to shift to the specific operation state to at least the actual operation state. As a 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 pressure accumulating 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 the drive of the actuator And control means.

  In a preferred aspect of the fuel pressure control apparatus according to the present invention, the fuel supply control means is configured so that the high-pressure fuel pump is operated when the condition for shifting to the specific operating state is satisfied or when it is predicted to shift to the specific operating state. The fuel supply to the pressure accumulating pipe section is stopped.

  Under such a configuration, for example, the fuel supply from the high-pressure fuel pump to the pressure accumulating pipe section is stopped when the fuel cut condition is satisfied, so that the fuel cut is actually started after the fuel cut condition is satisfied. Up to this point, the fuel pressure in the pressure accumulating piping section is reduced by the amount consumed by the fuel injection from the injector. For this reason, when the fuel supply to the pressure accumulating piping section is continued from the time when the fuel cut condition is satisfied until the time when the fuel cut is actually started as in the prior art, the fuel immediately after the fuel cut starts and immediately after the fuel cut ends. While the pressure is considerably higher than the target fuel pressure value required immediately after the end of the fuel cut, in the device of the present invention, the fuel pressure at the start of the fuel cut and immediately after the end of the fuel cut is brought closer to the target fuel pressure value. It will be.

  As a result, when recovering from a fuel cut (returning fuel supply), it is possible to ensure an optimal fuel pressure at which lean combustion is established, and after the return from the fuel cut, lean combustion can be performed immediately. As a result, the lean combustion region is expanded and fuel efficiency can be improved. In addition, by starting the recovery from the fuel cut (return of fuel supply) with lean combustion, it is possible to eliminate the switching of combustion in the steady state, and it is possible to reduce torque shock and rotational speed fluctuation due to different combustion. .

Other preferred embodiments of the fuel pressure control device according to the present invention are listed below.
Preferably, the fuel supply control means supplies fuel from the high-pressure fuel pump to the pressure accumulation piping unit so that the fuel pressure in the pressure accumulation piping unit becomes the target fuel pressure value when the fuel pressure of the pressure accumulation piping unit shifts to the specific operation state. The timing to stop is delayed from the time when the condition for shifting to the specific operating state is satisfied or 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 for stopping the fuel supply from the high-pressure fuel pump to the pressure accumulating piping section at the time when the condition for shifting to the specific operation state is satisfied or the specific operation state. The determination is made in anticipation of a decrease in the fuel pressure in the pressure accumulating pipe section due to fuel injection from the injector from when it is predicted to shift to the actual operation state.

  In a more specific preferred aspect, the fuel supply control means reduces the fuel pressure drop amount of the pressure accumulating pipe section and the fuel pressure of the pressure accumulating pipe section to the target fuel pressure value by one fuel injection of the injector. The number of injections required for the fuel injection is calculated, and based on these, the timing for stopping the fuel supply from the high-pressure fuel pump to the pressure accumulating pipe section is determined.

  Thus, by delaying the timing for stopping the fuel supply, the fuel pressure is prevented from excessively decreasing, and the control accuracy of the fuel pressure is improved.

  On the other hand, the transition predicting means preferably predicts the transition to the specific operating state using at least the engine speed and the rate of increase thereof as parameters.

  In this way, the fuel pressure control is performed by setting the fuel supply stop timing by estimating the transition to the specific operation state such as the fuel cut by the transition predicting means under the condition different from the fuel cut condition. The control can be started earlier than when the cutting condition is established, and the degree of freedom in control is improved.

  The fuel supply control means preferably releases the stop of fuel supply from the high-pressure fuel pump to the pressure accumulation pipe when the fuel pressure in the pressure accumulation pipe reaches the target fuel pressure value. The

  Further, the fuel supply control means preferably cancels 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. The

  By doing as described above, the fuel pressure is prevented from excessively decreasing, and the fuel pressure value adapted to the operating state is maintained.

  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 start stratified combustion or lean combustion immediately after the lean combustion, that is, from the end of the fuel cut.

In a further preferred aspect, a fuel injection amount control means for controlling a fuel injection amount (drive pulse width = duty ratio) from the injector is provided, and fuel supply from the high-pressure fuel pump to the pressure accumulating piping section by the fuel supply control means is provided. Control is performed such that the fuel pressure in the pressure accumulating piping section is set to the target fuel pressure value by stopping and controlling the fuel injection amount by the fuel injection amount control means.
As a result, the degree of control freedom and control accuracy are further improved.

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

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 apparatus 100 of the illustrated embodiment is provided in a direct injection engine 200 that is configured to supply fuel from a high-pressure fuel pump 307 to an injector 304 via a pressure accumulating pipe section (common rail) 303, and its basic configuration Is a condition establishment determination means 101 for determining whether or not a condition for shifting to fuel cut is established based on predetermined parameters such as engine speed, driving load, accelerator opening, vehicle speed, and the like. When it is determined by the means 101 that the condition for shifting to the fuel cut is satisfied, the pressure accumulation required 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 piping section 303 and the time when the condition for shifting to fuel cut is satisfied. The fuel from the high pressure fuel pump 307 to the pressure accumulating pipe section 303 is set so that the fuel pressure in the pressure accumulating pipe section 303 becomes the target fuel pressure value for an arbitrary period until the actual shift to the fuel cut. Fuel supply control means 103 for forcibly stopping supply and fuel injection amount control means 104 for supplying a drive signal having a required duty ratio (pulse width) to the injector 304 are provided.

  The fuel supply control means 103 stops the fuel supply to the pressure accumulating pipe section 303 by returning the fuel from the pump chamber 315 to the fuel tank 320 side in the compression discharge stroke of the high pressure fuel pump 307. A suction valve 311 provided in the pump chamber 315 of the high-pressure fuel pump 307, an electromagnetic actuator 309 capable of opening the suction valve 311 at an arbitrary timing, and an actuator drive control means for controlling the drive of the actuator 309 105.

  The condition establishment determining means 101, the target fuel pressure value calculating means 102, the actuator drive control means 105 of the fuel supply control means 103, and the fuel injection amount control means 104 are programs executed by a microcomputer built in the control unit 301. A part is specifically expressed by functional blocks.

  FIG. 2 shows a specific overall configuration of the direct 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 the engine operating state measuring means, and controls the intake flow rate. The collector 223 is entered through the throttle body 221 in which the valve 224 is accommodated. The airflow sensor 218 outputs a signal representing the intake air flow rate to a control unit 301 that is an engine control device.

  The throttle body 221 is provided with a throttle sensor 217 which is one of engine operating state measuring means for detecting the opening degree of the electric throttle valve 224, and the signal is also output to the control unit 301. It is like that. The air sucked into the collector 223 is distributed to the intake pipes 225 connected to the cylinders 229 of the engine 200 and then guided to the combustion chamber 228 of the cylinder 229.

On the other hand, the fuel such as gasoline is first pressurized from the fuel tank 320 by the low-pressure fuel pump 319 and fixed at a constant pressure (for example, 3 kg / kg) by the fuel pressure regulator 318, as can be understood by referring to FIG. 3 in addition to FIG. The pressure is adjusted to be cm ² ), and is secondarily pressurized (for example, 50 kg / cm ² ) to a higher pressure by the high-pressure fuel pump 307 and is pumped to the pressure accumulating pipe section (common rail) 303. The high-pressure fuel is injected into the combustion chamber 228 from an injector 304 provided in each cylinder 229. The fuel injected into the combustion chamber 228 is ignited by the spark plug 215 by the ignition signal that has been increased in voltage by the ignition coil 211. A 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 shaft in order to detect the rotation and phase of the crankshaft 240 of the engine, and its output is input to the control unit 301.

  Furthermore, an A / F sensor 208 provided upstream of the catalyst 210 in the exhaust pipe 209 detects exhaust gas and outputs a detection signal to the control unit 301.

  As shown in FIG. 5, the main part of the control unit 301 is composed of an MPU 402, a ROM 401, a RAM 403, an I / O LSI 404 including an A / D converter, and the like, and is one of means for measuring (detecting) the operating state of the engine. Each of the injectors receives signals from various sensors including the air flow sensor 218 and the fuel pressure sensor 302 as inputs, executes predetermined calculation processing, outputs various control signals calculated as the calculation results, 304, a predetermined control signal is supplied to the ignition coil 211 and the actuator 309 (the solenoid 309a thereof) of the high pressure pump 307 to execute fuel supply amount control, ignition timing control, and fuel pressure control.

  An example of the configuration and operation of the high-pressure fuel pump 307 will be described with reference to FIGS. A fuel suction passage 313, a discharge passage 306, and a pressurizing chamber 315 are formed in the pump body 307A. A plunger 314 is slidably held in the pressurizing chamber 315. The suction passage 313 and the discharge passage 306 are provided with a suction valve 311 and a discharge valve 316, which are held in one direction by springs 312 and 317, respectively, and serve as check valves that limit the fuel flow direction. . Further, an electromagnetic actuator 309 including a solenoid 309a, a suction element 309b, a spring 308, and a plunger-type engaging member 310 is held by the pump body 307A. When the energization of the solenoid 309a is OFF, the engaging member 310 is biased by a spring 308 in a direction to open the suction valve 311. Since the urging force of the spring 308 is larger than the urging force of the suction valve spring 312, the suction valve 311 is in an open state when the energization of the solenoid 309a is OFF. The fuel is pressure-regulated at a constant pressure by the pressure regulator 318 and guided from the tank 320 to the fuel inlet of the pump body 307A by the low-pressure pump 319. Thereafter, the pressure is increased by the pump main body 307 </ b> A and is pumped 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 accumulation piping unit 303. The injector 304 is mounted in accordance with the number of cylinders of the engine, and the fuel injection amount is controlled by a drive signal from the engine control unit 301. The relief valve 305 is opened when the pressure in the pressure accumulating piping section 303 exceeds a predetermined value, and prevents damage to the piping system.

The operation in the above configuration will be described below.
A lifter 321 provided at the lower end of the plunger 314 is pressed against the cam 202 by a spring 322. The plunger 314 is reciprocated by a cam 202 rotated by a camshaft or the like of an intake valve or exhaust valve of an engine to change the volume in the pump chamber 315. When the suction valve 311 closes during the compression stroke of the pump chamber 315 in which the plunger 314 rises, the pressure in the pump chamber 315 rises, whereby the discharge valve 316 is automatically opened, and the fuel is supplied to the pressure accumulating pipe section 303. Pump.

  The suction valve 311 automatically opens when the pressure in the pump chamber 315 becomes lower than the fuel inlet, but the closing is determined by the operation of the solenoid 309a. When the solenoid 309a is kept in the ON (energized) state, an electromagnetic force greater than the urging force of the spring 308 is generated, and the engaging member 310 is pulled toward the attractor 309b. Therefore, the engaging member 310 and the suction valve 311 are separated. Is 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 suction valve 311 is closed, and the fuel corresponding to the volume reduction of the pump chamber 315 pushes the discharge valve 316 and is pumped to the pressure accumulating pipe section 303. Therefore, the maximum discharge of the pump can be performed regardless of the responsiveness of the solenoid 309a.

  On the other hand, when the solenoid 309a is kept OFF (non-energized), the engaging member 310 is engaged with the intake valve 311 by the urging force of the spring 308, and the intake valve 311 is held in the open state. Accordingly, even during the compression stroke, the pressure in the pump chamber 315 is maintained at a low pressure that is substantially the same as that of the fuel inlet, so the discharge valve 316 cannot be opened, and the fuel corresponding to the volume reduction in the pump chamber 315 is reduced. The fuel is returned to the fuel inlet side (fuel tank 320 side) through the intake valve 311. Therefore, the pump discharge amount can be set to zero.

  In addition, if the solenoid 309a is turned on during the compression stroke, the fuel is pressure-fed to the pressure accumulating pipe section 303 from this time. In addition, once the pumping starts, the pressure in the pump chamber 315 increases, so that even if the solenoid 309a is turned off thereafter, the suction valve 311 maintains the closed state and automatically opens in synchronization with the start of the suction stroke. I speak. Therefore, the discharge amount (the 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 the 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, based on the signal from the pressure sensor 302, the control unit 301 calculates an appropriate discharge timing and controls the solenoid 309a, so that the fuel pressure in the pressure accumulating piping 303 can be feedback controlled to the target fuel pressure value.

FIG. 6 shows a time chart of a change in fuel pressure when a fuel cut occurs in a conventional fuel pressure control device.
In the high-pressure fuel pump, as described above, the discharge amount is variably controlled to control the fuel supply to the injector. Therefore, the fuel pressure that has been once increased can be reduced only by the consumption from the injector. Can not. In the normal injection state (up to point a in the figure), since there is consumption (fuel injection) from the injector, the fuel pressure in the pressure accumulating piping is adjusted to the required fuel pressure by controlling the discharge amount from the pump. .

  While the fuel cut condition is satisfied (between a and b in the figure), the fuel injection from the injector is stopped and consumption is eliminated, so that the fuel pressure immediately before the fuel cut is maintained. Since the target fuel pressure is set by a map or the like according to parameters such as engine speed and load as shown in FIG. 7, if the engine speed decreases during fuel cut, the operating range changes, and the target fuel pressure changes. 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 lowering the fuel pressure is consumption from the injector, and since it can be controlled to the target fuel pressure only after the fuel supply is restored from the fuel cut, the actual fuel pressure behaves as shown by a broken line. . At the point b in the figure, when viewed from the operating state, even if it is desired to start stratified combustion, the fuel pressure at which combustion is established is not achieved, so the stratified combustion can actually be started after the point c in the figure. .

  In stratified combustion, combustion is established by igniting when fuel injected from the injector is transported in the vicinity of the spark plug in the cylinder. Therefore, combustion as shown in FIG. 8 is achieved by a combination of ignition timing and injection timing. A stable region is determined. The allowable combustion stability region is narrow, and for example, even if only the injection timing is changed, the combustion stability is rapidly deteriorated. Therefore, it is necessary to precisely control these in each operation state. Here, the influence of the fuel pressure on the stratified combustion is large, and an example thereof is shown in FIG. The fuel pressure range that is below the surge limit in each operation state such as an idle state or a partial state 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 combustion is started in a state where the fuel pressure is outside the combustion establishment range, various problems such as exhaust deterioration due to misfire, rotational fluctuation, and torque shock may occur. End up. According to the present invention, the fuel pressure is always set to the optimum value in the operation region where stratified combustion can be realized from the aspect of output torque, so that the restriction of the responsiveness of the fuel pressure control can be eliminated. It is possible to expand the stratified combustion operation region that is carried out for the purpose of improving the exhaust performance.

An example of a time chart of fuel pressure control in the embodiment of the present invention is shown in FIG.
Conventionally, the pressure just before the fuel cut is maintained at the pressure just before that, so even if you want to realize stratified combustion at the time of fuel cut recovery, the fuel pressure is not the required fuel pressure, so a delay of a predetermined time S Later, stratified combustion will be started. In the embodiment of the present invention, when the fuel cut condition is satisfied, a fuel pressure securing request is generated, and the fuel pressure at which combustion at the time of fuel supply return from the fuel cut is established while the fuel pressure is controllable. The fuel pressure behavior indicated 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 (at the time of fuel supply return) is calculated based on a predetermined parameter such as the engine speed, and when the fuel cut condition is satisfied The fuel supply from the high pressure fuel pump 307 to the pressure accumulating pipe section 303 is forcibly stopped so that the fuel pressure in the pressure accumulating pipe section 303 becomes the target fuel pressure value during a period from when the fuel cut to actual fuel cut. Let As a result, stratified combustion is possible at the time of fuel supply return from the fuel cut, and the stratified 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 a fuel pressure securing request.
When the fuel cut condition is satisfied, it is not necessary to start the fuel cut immediately due to the drivability requirement such as torque shock, but after the condition is satisfied, the normal fuel injection is continued for a predetermined time or the predetermined number of injections. If there is, only a predetermined cylinder is cut, and then all cylinders are cut to avoid sudden changes in output torque. Conventionally, while fuel consumption from the injector is present, the drive pulse to the discharge control solenoid of the high pressure fuel pump is always output until immediately before the fuel cut of all cylinders in order to always keep the fuel pressure at the target value. In the embodiment, 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 and fuel injection to cylinders outside the predetermined cylinder, the pressure of X is reduced at the start of the all-cylinder fuel cut at point C in the figure. As described above, in the embodiment of the present invention, the fuel pressure is lowered by destroying the relationship between the fuel supply and consumption by the pump and the injector, and the fuel pressure required for combustion when the fuel supply is returned from the fuel cut is ensured. .

  FIG. 12 shows an example of a control time chart during a fuel pressure ensuring request with a delay (a fuel supply stop request to the pressure accumulating piping section 303). The drive pulse to the solenoid 309a of the actuator 309, in other words, the stop of the fuel supply from the high pressure fuel pump 307 to the pressure accumulating pipe section 303 is delayed for a predetermined time, not from the establishment of the fuel cut condition (point A in the figure), This is an example of stopping at point A ′ in the figure. When the driving pulse from the point A to the solenoid 309a is stopped, the fuel pressure decreases as shown by the broken line in the drawing, and may fall below the surge limit fuel pressure upper limit of homogeneous combustion. This makes combustion unstable and causes exhaust and torque shock. For this reason, it is necessary to ensure 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 combustion is not established.

  FIG. 13 is a flowchart showing an example of a program for realizing the control shown in the time charts of FIGS.

  First, in step S11, it is determined whether the fuel cut condition is satisfied. If the fuel cut condition is satisfied, the fuel pressure is decreased by one fuel injection based on the injection pulse width (injection amount) that is currently injected from the injector 304. The amount is calculated (step S12). The relationship between the injection pulse width (injection amount) and the fuel pressure decrease amount is determined by the characteristics of the injector and the common rail piping volume, etc., and is not calculated by calculation, but is preset as a table value as shown in FIG. You can also. Next, the target reduced fuel pressure amount is calculated (step S13). As shown in FIG. 14, since the fuel pressure range in which combustion is established in each combustion and operating state is determined, it is necessary to ensure it until all cylinder fuel cuts are started. Therefore, the target fuel pressure reduction is calculated from the current fuel pressure to the fuel pressure that can realize the current combustion and satisfy the combustion request after the fuel cut is restored. In step S14, the required number of injections (A) indicating how many injections are required only to satisfy the target reduced fuel pressure amount by the fuel pressure reduction amount due to the fuel injection amount from one injector is calculated in step S14. Next, the number of injections (B) from the establishment of the fuel cut condition to the start of the fuel cut for all cylinders is calculated in consideration of the specific cylinder fuel cut and the like based on the engine speed (step S15). In step S16, the above (A) and (B) are compared, and if the number of injections (B) until the start of all cylinder cut is large, the drive pulse to the solenoid 309a is stopped after the predetermined delay A has elapsed, that is, the high pressure A process for forcibly stopping the fuel supply from the fuel pump 307 to the pressure accumulating pipe section 303 is performed (step S17). Conversely, if the required number of injections (A) is large, the immediate drive pulse is stopped and the fuel pressure is reduced (step S18). Here, it may be possible that the fuel pressure cannot be reduced to the target fuel pressure by the start of the cut of all cylinders only by stopping the drive pulse of the solenoid 309a. It is also possible to manipulate (increase) the fuel injection amount for each time.

  As a result, the fuel pressure is lowered while ensuring the combustion establishment from the establishment of the fuel cut condition, and at the same time, the required fuel pressure (target fuel pressure value) such as stratified combustion after the return of fuel supply from the fuel cut is secured. It becomes possible. Here, when the combustion after the fuel supply return from the fuel cut is not stratified combustion, for example, when the acceleration request is generated by the driver's accelerator operation during the fuel cut, the torque is required, so the normal combustion instead of the lean combustion is required. When the fuel cut is restored by homogeneous combustion, according to the embodiment of the present invention, the fuel pressure that establishes the combustion just before the fuel cut is ensured, and in homogeneous combustion, the influence of the fuel pressure on the combustion is small (sensitivity). Therefore, there is no problem with operability and exhaust performance.

FIG. 16 is a functional block diagram showing a basic configuration of another embodiment of the fuel pressure control device according to the present invention.
The fuel pressure control device 150 of the illustrated embodiment is provided in a direct injection engine 200 configured to supply fuel from a high-pressure fuel pump 307 to an injector 304 via a pressure accumulating pipe section (common rail) 303, and its basic configuration Is provided with a transition predicting means 107 in place of the condition establishment determining means 101 of FIG.

  The transition predicting means 107 predicts the transition to the fuel cut in advance based on predetermined parameters such as the engine speed and its rate of increase, the driving load, the accelerator opening, the vehicle speed, and the gear position. When the shift predicting unit 107 predicts the shift to the fuel cut, the target fuel pressure value calculating unit is requested based on a predetermined parameter such as the engine speed and immediately after the fuel cut is completed, the pressure accumulating pipe unit 303. The fuel pressure in the pressure accumulating pipe section 303 is calculated during the period from when the fuel supply control means 103 is predicted to shift to the fuel cut until it actually shifts to the fuel cut. The fuel supply from the high pressure fuel pump 307 to the pressure accumulating pipe section 303 is forcibly stopped so as to reach the target fuel pressure value.

  FIG. 17 shows an example of a time chart of a fuel pressure securing request (a fuel supply stop request to the pressure accumulating piping unit 303) in the prediction of establishment of the fuel cut condition performed under such a configuration.

  An example of the driving condition is a downshift operation while the driver is moving away from the accelerator (coast). When the foot is released, the idle SW is turned from OFF to ON. After that, when the shift stage is downshifted from the 3rd speed to the 2nd speed for the purpose of engine braking or the like, the low speed stage is obtained, and therefore the engine speed starts to increase after the point A. When this state continuously exceeds the predetermined engine speed determined by the fuel cut condition, fuel cut is permitted (started) as indicated by point C in the figure. In the present embodiment, it is possible to predict the transition 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 accumulating pipe section 303). The fuel cut is predicted based on the engine speed, its rate of increase (increase speed), and other operating parameters from when the downshift is performed until the engine speed exceeds the fuel cut permission engine speed (between AC in the figure). In addition, 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 supply of fuel is interrupted and only the consumption from the injector 304 is made, so that the fuel pressure is reduced in accordance with the amount of consumption. In this operation, at the start of the fuel cut, the fuel pressure X in the steady state is decreased to a value of Y, and the fuel pressure of the combustion request at the time of the fuel cut return is secured or close to the request. That is what I intended. Of course, the value of the fuel pressure to be reduced is set within a range in which combustion before fuel cut is established.

  FIG. 18 shows an example of a fuel pressure control start determination program based on fuel cut prediction in a flowchart example. First, in step S21, it is determined from the engine speed, the accelerator opening, the engine water temperature, the 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 rise, 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 ensure the current combustion, it is determined here whether the engine speed is equal to or higher than a predetermined speed with the engine speed as 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 from this that a fuel cut will occur (step 23). When these conditions are satisfied, the fuel pressure is decreased and secured by fuel pressure control (step 24).

  FIG. 19 is a flowchart showing an example of an end determination program for fuel pressure control based on fuel cut prediction. Basically, the state in which the fuel cut condition is canceled is determined by acceleration determination or the like, and the fuel pressure control is terminated, that is, the stop of the fuel supply from the high pressure fuel pump 307 to the pressure accumulating piping unit 309 is canceled (steps S31 and S34). ). Further, when the actual fuel pressure is unintentionally lowered to a predetermined pressure or lower in the fuel pressure control of the present invention, the combustion cannot be ensured in the same manner, so that the control is terminated (fuel supply stop cancellation) (step S32). , S34). Also, fuel pressure control is started by predicting a fuel cut, but if it is determined that the fuel cut will not be performed after that, for example, the increase speed of the engine speed has fallen below the predetermined value, the fuel pressure control is also performed. End (steps S33, S34).

  As mentioned above, although several embodiment of the control apparatus of this invention was explained in full detail, this invention is not limited to the said embodiment, In the range which does not deviate from the mind of the invention described in the claim, Various changes can be made in the design.

The functional block diagram which shows the basic composition of one Embodiment of the fuel pressure control apparatus which concerns on this invention. 1 is an overall configuration diagram showing an in-cylinder injection engine and a fuel pressure control device provided therein. Diagram showing an example of the configuration and operation of a high-pressure fuel pump The figure which shows the detailed structure of a high pressure fuel pump. The figure which shows an example of the principal part of a control unit. The time chart which shows an example of the fuel pressure change at the time of the fuel cut generation in the past. The figure which shows the example of a setting of a target fuel pressure value. The figure which shows an example of the combustion stable area | region in a cylinder injection engine. The figure used for description of the influence which fuel pressure has on stratified combustion. The time chart which shows an example of the fuel pressure control of this invention. The time chart which shows the example of the fuel pressure control in the fuel pressure ensuring request | requirement. The time chart which shows the example of the fuel pressure control in the fuel ensuring request | requirement with a delay. The flowchart which shows an example of the program which implement | achieves control of FIG. 11, FIG. The graph which shows the relationship between an injection pulse width (injection amount) and a fuel pressure fall amount. The graph which shows the fuel pressure range of combustion establishment in each combustion operation state. The functional block diagram which shows the basic composition of other embodiment of the fuel pressure control apparatus which concerns on this invention. The time chart which shows the example of the fuel pressure control in fuel cut condition establishment prediction. The flowchart which shows the example of the fuel pressure control start determination program by fuel cut prediction. An example of a flowchart showing an example of a fuel pressure control end determination program based on fuel cut prediction

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Fuel pressure control apparatus 101 ... Condition establishment 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 ... Accumulator piping (common rail)
304 ... Injector 305 ... Relief valve 306 ... Fuel discharge passage 307 ... High pressure fuel pumps 308, 312, 317 ... Spring 309 ... Electromagnetic actuator 309a ... Solenoid 310 ... Engagement member 311 ... Suction valve 313 ... Fuel suction passage 314 ... Plunger 315 ... Pump chamber (pressurizing chamber)
316 ... Discharge valve 318 ... Fuel pressure regulator 319 ... Low pressure fuel pump 320 ... Fuel tank

Claims (13)

A fuel pressure control device provided in an in-cylinder injection engine configured to supply fuel from a high-pressure fuel pump to an injector through an accumulator pipe,
Based on a predetermined parameter such as the engine speed, a condition establishment determination unit that determines whether or not a condition for shifting to a specific operation state such as a fuel cut in which fuel injection is not performed is established, and the condition establishment determination unit When it is determined that the condition for shifting to the specific operating state is established, the target fuel pressure value of the pressure accumulating pipe section required immediately after the specific operating state is ended based on a predetermined parameter such as an engine speed. The target fuel pressure value calculating means for calculating, and the fuel pressure of the pressure accumulating pipe section during the arbitrary period between the time when the condition for shifting to the specific operating state is satisfied and at least the time of actually shifting to the specific operating state are the target pressure Fuel supply control means for forcibly stopping fuel supply from the high-pressure fuel pump to the pressure accumulating pipe section so as to obtain a fuel pressure value. Fuel pressure control apparatus. A fuel pressure control device provided in an in-cylinder injection engine configured to supply fuel from a high-pressure fuel pump to an injector through an accumulator pipe,
Based on a predetermined parameter such as engine speed, a transition predicting means for predicting in advance a transition to a specific operating state such as a fuel cut in which fuel injection is not performed, and a transition to the specific operating state by this transition predicting means Is predicted, based on a predetermined parameter such as the engine speed, 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 completed, and the specific The high-pressure fuel so that the fuel pressure in the pressure accumulating piping section becomes the target fuel pressure value for an arbitrary period from the time when the transition to the operation state is predicted to the actual transition to the specific operation state. And a fuel supply control means for forcibly stopping the fuel supply from the pump to the pressure accumulating pipe section.   The fuel supply control means is configured to stop the fuel supply to the pressure accumulating 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. The fuel pressure control apparatus according to claim 1 or 2.   The fuel supply control means includes: a suction valve provided in a pump chamber of the high-pressure fuel pump; an actuator that can open the suction valve at an arbitrary timing; and an actuator drive control means that controls driving of the actuator. The fuel pressure control device according to any one of claims 1 to 3, wherein the fuel pressure control device is configured.   The fuel supply control means stops the fuel supply from the high-pressure fuel pump to the pressure accumulating pipe section when a condition for shifting to the specific operation state is satisfied or when it is predicted to shift to the specific operation state. The fuel pressure control device according to any one of claims 1 to 4, wherein the fuel pressure control device is configured as described above.   The fuel supply control means stops the fuel supply from the high-pressure fuel pump to the pressure accumulating pipe section so that the fuel pressure in the pressure accumulating pipe section reaches the target fuel pressure value when the fuel pressure in the pressure accumulating pipe section shifts to the specific operation state. 5 is delayed from the time point when the condition for shifting to the specific operation state is satisfied or the time point at which it is predicted to shift to the specific operation state. The fuel pressure control device described in 1.   The fuel supply control means is configured to stop the fuel supply from the high-pressure fuel pump to the pressure accumulating pipe section at a time when a condition for shifting to the specific operation state is satisfied or a time when the condition is predicted to shift to the specific operation state 7. The fuel according to claim 6, wherein the fuel pressure is determined in anticipation of a decrease in fuel pressure in the pressure accumulating piping portion due to fuel injection from an injector until the actual operation state is shifted to the specific operation state. Pressure control device.   The fuel supply control means includes: a fuel pressure decrease amount of the pressure accumulating piping portion due to one fuel injection of an injector; and an injection number required to reduce the fuel pressure of the pressure accumulating piping portion to the target fuel pressure value. The fuel pressure control according to claim 6 or 7, wherein a timing for stopping the fuel supply from the high-pressure fuel pump to the pressure accumulating pipe portion is determined based on the calculated values. apparatus.   3. The fuel pressure control according to claim 2, wherein the transition predicting unit is configured to predict a transition to the specific operation state using at least an engine speed and an increase rate thereof as parameters. apparatus.   The fuel supply control means is configured to cancel the stop of fuel supply from the high-pressure fuel pump to the pressure accumulating piping when the fuel pressure in the pressure accumulating piping reaches the target fuel pressure value. The fuel pressure control device according to any one of claims 1 to 9.   The fuel supply control means releases the stop of the fuel supply when the acceleration state of the vehicle is detected even before the fuel pressure of the pressure accumulating pipe reaches the target fuel pressure value. The fuel pressure control device described in 1.   The fuel pressure control apparatus according to any one of claims 1 to 11, wherein the target fuel pressure value is set to a fuel pressure value that enables stratified combustion or lean combustion.   Fuel injection amount control means for controlling the fuel injection amount from the injector is attached, the fuel supply control means stops the fuel supply from the high pressure fuel pump to the pressure accumulation piping section, and the fuel injection amount by the fuel injection amount control means The fuel pressure control device according to any one of claims 1 to 12, wherein the control is performed so that the fuel pressure of the pressure accumulating pipe section is the target fuel pressure value.

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