JP5085483B2 - High pressure fuel pump control device for engine - Google Patents

Description

  The present invention relates to a high-pressure fuel pump control device for an engine mounted on an automobile or the like, and more particularly, to a high-pressure fuel pump control device for an engine that can properly maintain a fuel pressure in a common rail.

  2. Description of the Related Art Conventionally, in an engine, various techniques for increasing the pressure of fuel and pumping high-pressure fuel to the fuel injection valve have been proposed in order to reduce the particle size of fuel injected from the fuel injection valve. Here, when high pressure fuel is supplied to the common rail by the high pressure fuel pump and high pressure fuel is injected from the fuel injection valve, the fuel pressure in the common rail decreases due to fuel injection by the fuel injection valve. Since the injection amount is limited in engine operation, the fuel pressure in the common rail may become extremely high.

  Therefore, for example, in Patent Document 1 below, a relief valve (relief valve) for escaping fuel in the accumulator chamber is connected to the common rail, and the fuel pressure in the accumulator chamber is determined from a predetermined set pressure when fuel supply to the engine is stopped. When the pressure is higher, the relief valve is opened until the fuel pressure in the pressure accumulating chamber falls below the set pressure.

Japanese Patent Laid-Open No. 7-103029

  On the other hand, the configuration around the high-pressure fuel pump includes a pump that sucks and discharges fuel, a solenoid that adjusts the amount of fuel discharged by the pump, and a discharge that controls the discharge amount of the pump by supplying an electric signal to the solenoid In the case of comprising a quantity control means, there is a maximum and minimum fuel quantity that can be discharged by the pump due to its mechanical characteristics.

  Here, as described in the above-mentioned Patent Document 1, when the required fuel amount of the engine is smaller than the minimum amount of fuel that can be discharged, not when the fuel supply is stopped, the fuel balance of the common rail is excessively supplied, so that the common rail The fuel pressure in the fuel tank rises, and as a result, a small amount of fuel cannot be injected due to an increase in the pressure difference between the upstream and downstream sides of the fuel injection valve, the fuel injection valve cannot be opened, and fuel leakage may occur due to exceeding the fuel pressure resistance.

  The present invention has been made in view of such problems, and the object of the present invention is not to increase the fuel pressure in the common rail even when the required fuel amount of the engine is smaller than the minimum dischargeable fuel amount, An object of the present invention is to provide a high-pressure fuel pump control device for an engine that can be maintained within a desired pressure range.

In order to achieve the above object, the high pressure fuel pump control device for an engine according to the present invention basically supplies an electric signal to a solenoid for adjusting the fuel discharge amount of the high pressure fuel pump to provide the high pressure fuel pump. Discharge amount control means for controlling the discharge amount, common rail for accumulating and holding the fuel discharged from the high-pressure fuel pump, fuel deriving means for guiding the fuel in the common rail to a fuel injection valve, and fuel relief for relieving the fuel from the common rail And a relief valve opening degree control means for controlling the opening degree of the fuel relief valve, wherein the relief valve opening degree control means includes a minimum fuel amount that can be discharged by the high-pressure fuel pump and the fuel injection valve. When the minimum amount of fuel that can be discharged is approximately equal to or exceeds the fuel supply amount, the fuel release It is characterized by increasing the valve opening or the opening degree of the valve.

In a preferred aspect, the discharge amount control means controls the discharge amount of the high-pressure fuel pump to be the minimum dischargeable fuel amount, and the relief valve opening control means controls the discharge amount of the high-pressure fuel pump. The opening degree is controlled so that a difference from the fuel supply amount is relieved from the fuel relief valve.

In this case, in a preferred embodiment, the fuel relief valve has a means for detecting the fuel pressure in the common rail, and the relief valve opening control means controls the opening of the fuel relief valve so that the fuel pressure in the common rail becomes a target value. To be done.

In another preferred aspect, the relief valve opening control means holds the fuel relief valve at a predetermined opening, and the discharge amount control means includes a fuel amount relieved from the fuel relief valve, a fuel supply amount, The discharge amount is controlled so that the sum is discharged from the high-pressure fuel pump.

In this case, in a preferred aspect, the fuel cell has a means for detecting the fuel pressure in the common rail, and the discharge amount control means controls the discharge amount of the high-pressure fuel pump so that the fuel pressure in the common rail becomes a target value. To be done.

  In the engine high-pressure fuel pump control apparatus according to the present invention configured as described above, the required fuel amount (fuel injection amount) of the engine is smaller than the minimum amount of fuel that can be discharged, and the fuel balance of the common rail may become excessively supplied. If there is, the amount of fuel to be relieved from the relief valve can be made larger than the amount of fuel to be excessively supplied, so that the fuel pressure in the common rail is not increased and maintained within a desired pressure range. As a result, it is possible to effectively prevent the occurrence of a small amount of fuel injection due to a rise in the pressure difference between the upstream and downstream of the fuel injection valve, the inability to open the fuel injection valve, and fuel leakage due to exceeding the fuel pressure resistance. be able to.

  Embodiments of a high-pressure fuel pump control device for an engine according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a system configuration diagram showing an embodiment of a high-pressure fuel pump control device for an engine according to the present invention, together with an engine to which it is applied.

  The engine 507 in the illustrated example is a four-cylinder in-cylinder injection engine provided with a fuel injection valve 54 that directly injects fuel into the combustion chamber 507c, and air taken into each cylinder (cylinder) 507b is air cleaner 502. And enters the collector 506 through the air flow meter (air flow sensor) 503, through the throttle body 505 in which the electric throttle valve 505a for controlling the intake flow rate is accommodated. The air sucked into the collector 506 is distributed to an intake pipe 501 connected to each cylinder 507b of the engine 507, and then guided to a combustion chamber 507c formed by the piston 507a, the cylinder 507b, and the like.

  Further, the air flow sensor 503 supplies a signal representing the intake flow rate to a control unit 515 which is a main component of the high pressure fuel pump control device of the present embodiment. Further, the throttle body 505 is provided with a throttle sensor 504 for detecting the opening degree of the electric throttle valve 505a, and the signal is also supplied to the control unit 515.

On the other hand, fuel such as gasoline is primarily pressurized from a fuel tank 50 by a low-pressure fuel pump 51 and regulated to a constant pressure (for example, 3 kg / cm ² ) by a fuel pressure regulator 52, and at a later-described high-pressure fuel pump 1. Secondary pressure is applied to a higher pressure (for example, 50 kg / cm ² ), and the fuel is injected into a combustion chamber 507 c from a fuel injection valve (hereinafter referred to as an injector) 54 provided for each cylinder 507 b through a common rail 53. The The fuel injected into the combustion chamber 507c is ignited by the ignition plug 508 by the ignition signal that has been increased in voltage by the ignition coil 522.

  A crank angle sensor (hereinafter referred to as a position sensor) 516 attached to the crankshaft 507d of the engine 507 outputs a signal indicating the rotational position of the crankshaft 507d to the control unit 515, and the opening / closing timing of the exhaust valve 526 is variable. A crank angle sensor (hereinafter referred to as a phase sensor) 511 attached to a camshaft (not shown) having a mechanism for turning the camshaft outputs an angle signal indicating the rotational position of the camshaft to the control unit 515 and an exhaust valve An angle signal indicating the rotational position of the pump drive cam 100 of the high-pressure fuel pump 1 rotating with the rotation of the cam shaft 526 is also output to the control unit 515.

  As shown in FIG. 2, the control unit 515 includes an MPU 603, an EP-ROM 602, a RAM 604, an I / O LSI 601 including an A / D converter, and the like, and includes a position sensor 516, a phase sensor 511, a water temperature sensor 517, In addition, signals from various sensors including the fuel pressure sensor 56 are input as inputs, predetermined calculation processing is executed, various control signals calculated as the calculation results are output, and the high-pressure pump solenoid 200 which is an actuator, A predetermined control signal is supplied to each of the fuel injection valves 54, the ignition coil 522, etc., and fuel discharge amount control, fuel injection amount control, ignition timing control, and the like are executed.

  FIG. 3 is an overall configuration diagram of a fuel system including the high-pressure fuel pump 1, and FIG. 4 is a longitudinal sectional view of the high-pressure fuel pump 1.

  The high-pressure fuel pump 1 pressurizes the fuel from the fuel tank 50 and pumps the high-pressure fuel to the common rail 53. A fuel suction passage 10, a discharge passage 11, and a pressurizing chamber 12 are formed. In the pressurizing chamber 12, a plunger 2 as a pressurizing member is slidably held. A discharge valve 6 is provided in the discharge passage 11 so as to prevent the high-pressure fuel on the downstream side from flowing back into the pressurizing chamber. The intake passage 10 is provided with an electromagnetic valve 8 that controls the intake of fuel. The electromagnetic valve 8 is a normally closed type electromagnetic valve, and a force acts in the valve closing direction when not energized, and a force acts in the valve opening direction when energized.

  The fuel is led from the tank 50 to the fuel inlet of the pump body 1 by the low-pressure pump 51 after being regulated to a constant pressure by the pressure regulator 52. After that, the pump body 1 is pressurized and is pumped from the fuel discharge port to the common rail 53. A fuel injection valve 54 is connected to the common rail 53 via a conduit, and a pressure sensor 56 and a pressure adjustment valve (hereinafter referred to as a relief valve) 55 are mounted. The relief valve 55 is opened when the fuel pressure in the common rail 53 exceeds a predetermined value, and prevents damage to the high-pressure piping system. The fuel injection valves 54 are mounted according to the number of cylinders of the engine, and inject fuel according to the injection drive pulse (drive current) given from the control unit 515. The pressure sensor 56 outputs the acquired pressure data to the control unit 515. The control unit 515 calculates an appropriate amount of fuel to be injected, fuel pressure, etc. based on engine state quantities (for example, crank rotation angle, throttle opening, engine speed, fuel pressure, etc.) obtained from various sensors, and the pump 1 and fuel injection The valve 54 is controlled.

  The plunger 2 reciprocates via the lifter 3 pressed against the pump drive cam 100 that rotates with the rotation of the cam shaft of the exhaust valve 526 in the engine 507 to change the volume of the pressurizing chamber 12. When the plunger 2 descends and the volume of the pressurizing chamber 12 increases, the electromagnetic valve 8 opens and fuel flows into the pressurizing chamber 12 from the fuel suction passage 10. Hereinafter, the stroke in which the plunger 2 descends is referred to as an intake stroke. When the plunger 2 rises and the electromagnetic valve 8 closes, the fuel in the pressurizing chamber 12 is pressurized and passes through the discharge valve 6 and is pumped to the common rail 53. Hereinafter, the stroke in which the plunger 2 moves up is referred to as a compression stroke.

  FIG. 5 shows an operation timing chart of the high-pressure fuel pump 1. The actual stroke (actual position) of the plunger 2 driven by the pump drive cam 100 is a curve as shown in FIG. 6, but in order to make the positions of the top dead center and the bottom dead center easy to understand, The stroke of the plunger 2 is expressed linearly.

  If the electromagnetic valve 8 is closed during the compression stroke, the fuel sucked into the pressurizing chamber 12 during the suction stroke is pressurized and discharged to the common rail 53 side. If the electromagnetic valve 8 is opened during the compression stroke, the fuel is pushed back to the suction passage 10 side during that time, and the fuel in the pressurizing chamber 12 is not discharged to the common rail 53 side. Thus, the fuel discharge of the pump 1 is operated by opening and closing the electromagnetic valve 8. The opening and closing of the electromagnetic valve 8 is operated by the control unit 515.

The electromagnetic valve 8 includes a spring 92 that biases the valve body 5 in the valve closing direction, a solenoid 200, and an anchor 91 as components. When a current flows through the solenoid 200, an electromagnetic force is generated in the anchor 91 and is drawn to the right side in the figure, and the valve body 5 formed integrally with the anchor 91 is opened. When no current flows through the solenoid 200, the valve body 5 is closed by the spring 92 that biases the valve body 5 in the valve closing direction. The electromagnetic valve 8 is a valve having a structure that closes in a state where no driving current flows, and is therefore referred to as a normally closed electromagnetic valve.

  During the suction stroke, the pressure in the pressurizing chamber 12 becomes lower than the pressure in the suction passage 10, and the valve body 5 opens due to the pressure difference, and fuel is sucked into the pressurizing chamber 12. At this time, the spring 92 biases the valve body 5 in the valve closing direction, but the valve body 5 opens because the valve opening force due to the pressure difference is set to be larger. Here, if a drive current flows through the solenoid 200, the magnetic attractive force acts in the valve opening direction, and the valve body 5 is more easily opened.

  On the other hand, during the compression stroke, the pressure in the pressurizing chamber 12 is higher than that in the suction passage 10, so that no differential pressure for opening the valve body 5 is generated. Here, if the drive current does not flow through the solenoid 200, the valve body 5 is closed by a spring force or the like that biases the valve body 5 in the valve closing direction. On the other hand, if a driving current flows through the solenoid 200 and a sufficient magnetic attractive force is generated, the valve body 5 is biased in the valve opening direction by the magnetic attractive force.

  Therefore, when the drive current starts to be applied to the solenoid 200 of the electromagnetic valve 8 during the intake stroke and continues to be applied even during the compression stroke, the valve body 5 is held open. In the meantime, the fuel in the pressurizing chamber 12 flows back into the low-pressure passage 10, so that the fuel is not fed into the common rail. On the other hand, when the drive current is stopped at a certain timing during the compression stroke, the valve body 5 is closed and the fuel in the pressurizing chamber 12 is pressurized and discharged to the discharge passage 11 side. When the timing to stop applying the drive current is early, the volume of the pressurized fuel is large, and when the timing is late, the volume of the pressurized fuel is small. Therefore, the control unit 515 can control the discharge flow rate of the pump 1 by controlling the closing timing of the valve body 5.

  Further, the control unit 515 calculates an appropriate energization OFF timing based on the signal from the fuel pressure sensor 56, and controls the solenoid 200, so that the pressure of the common rail 53 can be feedback controlled to the target value.

  In the high pressure pump having such a structure, when it is first desired to control the fuel to the non-discharge state, the solenoid 200 is energized in the entire compression stroke, and the fuel in the pressurizing chamber 12 is caused to flow back to the low pressure passage 10 in the entire compression stroke. it can. Here, at the start and end of energization of the solenoid 200, there is a time lag between the response of the actual current value and the response of the mechanical solenoid valve from the switching of the electric signal, so that amount is ensured during the intake stroke. However, the energization start and end timings of the solenoid are controlled. However, when the engine speed is high and the suction and compression stroke times are short, it is impossible to ensure the response time of the actual current value and the delay time of the response of the mechanical solenoid valve during the suction stroke. Therefore, if it is desired to control the fuel to the non-discharge state during high engine rotation, the solenoid energization time ratio during the intake and compression strokes should be controlled to a high state so that the solenoid valve is mechanically held open. Good.

  However, particularly when it is desired to discharge a small amount of fuel at the time of high engine speed, as shown in FIG. 20, it is necessary to close the valve body displacement only during the actual discharge period. It is necessary to open the valve body displacement until the plunger displacement reaches the bottom dead center, and it is necessary to close the valve body displacement as close to the top dead center as possible after turning off the solenoid valve drive signal There are both. Since the valve body response delay is mainly determined by a time factor, the minimum amount of fuel that can be discharged is limited particularly under high engine speed conditions.

  Such a phenomenon will be described with reference to FIG. 8 which is an example of characteristics of the high pressure pump and the electromagnetic valve. In the figure, the pump drive frequency of the suction and compression strokes is shown on the horizontal axis, and the fuel discharge amount of the high-pressure pump per discharge is shown on the vertical axis. In the above-described high-pressure pump driving method, the pump driving frequency is determined by the rotational speed of the camshaft, and is therefore determined by the engine speed. The maximum value of the fuel discharge amount per discharge is determined by the plunger stroke, but the fuel seal performance of the plunger changes depending on the plunger speed. It has a characteristic that decreases with respect to the basic amount.

  On the other hand, the minimum value of the fuel discharge amount per discharge becomes a larger value as the pump drive frequency becomes higher due to the response delay of the electromagnetic valve as described above.

  In contrast, the amount of fuel required by the engine varies depending on various operating conditions and is determined independently of the fuel supply capacity of the high-pressure pump. Therefore, a fuel amount smaller than the minimum fuel amount that can be supplied by the high-pressure pump may be the required fuel amount of the engine.

  In such a case, if the high-pressure pump is driven at the minimum discharge amount and the required fuel amount is injected from the fuel injection valve, the fuel flow in and out of the common rail will be excessively supplied, so that the fuel pressure in the common rail will be increased by the increased fuel amount due to the elasticity of the fuel. As a result, there is a possibility that a small amount of fuel cannot be injected due to an increase in the pressure difference between the upstream and downstream sides of the fuel injection valve, that the fuel injection valve cannot be opened, and that fuel leakage occurs due to the fuel pressure being exceeded.

FIG. 9 shows an example of the injection flow rate characteristic of the fuel injection valve. The horizontal axis represents the ON time width of the injection pulse output from the control unit and drives the fuel injection valve, and the vertical axis represents the fuel injection amount in one injection. A, B, and C in the figure show variations in the fuel pressure difference between the upstream and downstream sides of the fuel injection valve, and the pressures increase in the order of A, B, and C. Since the fuel injection valve injects fuel at a predetermined speed via the fuel flow rate metering unit, the fuel injection amount with the same injection pulse width increases as the upstream / downstream fuel pressure difference increases. In addition, the fuel injection valve has a minimum injectable fuel amount that substantially corresponds to the injection pulse width from the response limit of the opening / closing operation of the valve body in accordance with the drive signal. Accordingly, the larger the difference between the upstream and downstream fuel pressures, the greater the difference. Therefore, when the pressure difference between the upstream and downstream fuel injectors increases, a small amount of fuel cannot be injected, and the mainstream is a valve-opening drive system against the upstream and downstream pressure difference. When it exceeds a predetermined value, the valve opening operation becomes impossible.

  In order to avoid such a situation, first, the responsiveness of the electromagnetic valve of the high-pressure pump is improved. However, the mechanical performance is limited due to various restrictions. In addition, supplying more fuel than the required fuel amount is not preferable in terms of various engine performances because the supply air-fuel ratio of the engine deviates from the target value in a rich manner. Furthermore, if the high-pressure pump is in a non-discharge state, the fuel balance in the common rail becomes excessively discharged, the fuel pressure is lowered, and as a result, the atomization of the fuel injected from the fuel injection valve is insufficient and the fuel supply is disabled. Further, stopping the fuel injection means ignoring the required fuel amount, and the engine cannot be maintained in a desired operation state.

  Therefore, in this embodiment, the minimum amount of fuel that can be discharged by the pump 1 and the fuel supply amount (fuel injection amount) are compared, and the minimum amount of fuel that can be discharged by the pump 1 is approximately equal to or greater than the fuel supply amount. The fuel relief valve 55 is opened (the opening degree is increased). If such control is performed and the capacity of the electric control relief valve 55 is made sufficiently large so that the amount of fuel relieved from the electric control relief valve 55 is larger than the supply excess amount of the fuel flow in and out of the common rail 53, the common rail As a result, the fuel pressure in the common rail 53 is increased by the increased fuel amount due to the elasticity of the fuel, and as a result, a small amount of fuel cannot be injected due to a rise in the pressure difference between the upstream and downstream of the fuel injection valve 54. It is possible to prevent the occurrence of fuel leakage due to the inability to open the valve 54 and the fuel pressure to be exceeded.

  An example of the control is shown in FIG. The processing of this control example is executed at predetermined time intervals to achieve its function. First, in block 701, the minimum fuel discharge amount of the high-pressure pump is obtained by table search based on the pump driving frequency according to the characteristics described in FIG. In this characteristic, the performance obtained in advance based on the mechanical characteristics of the high-pressure pump and the electromagnetic valve is stored in advance in a control constant as a search table. In addition, the minimum fuel discharge amount of the high-pressure pump 1 may vary depending on individual performance differences, temperatures, power supply conditions, and other environments. In such a case, an upper limit value of the variation is set and It is preferable to set the control relief valve 55 so that it can be opened. Further, if it is possible to estimate directly or indirectly depending on the state during operation of the high-pressure pump, the estimated characteristic may be used. Further, the pump driving frequency may be determined as appropriate depending on the driving mode of the high-pressure pump, and it goes without saying that the engine speed may be used in place of the driving mode using the cam shaft described above. In other cases, the number of revolutions of the electric motor may be used as long as the high-pressure pump is driven by the electric motor.

  It is determined whether the determined minimum fuel discharge amount exceeds the required fuel injection amount in the determination means 702. In the case of exceeding, the fuel balance in the common rail 53 is excessively supplied even if the high-pressure pump 1 is driven to the minimum discharge amount.

  Here, the cycle of the suction and compression stroke of the high-pressure pump 1 and the cycle of fuel injection do not necessarily coincide with each other. For example, when a high-pressure pump is driven by a camshaft, suction and compression are repeated by the number of leaves of the pump drive cam by two rotations of the engine crankshaft, but fuel injection is usually performed several times by cylinders by two rotations of the engine crankshaft. , Jetting. Therefore, it is preferable that the minimum fuel discharge amount and the required fuel injection amount to be compared coincide with each other. For example, both are the amount per rotation of the crankshaft, the amount in one combustion cycle of one cylinder, and the like. The optimum dimension may be selected as appropriate for the engine control system to which the present invention is applied.

  The determination thus obtained is an operation request for the electric relief valve 55. In block 703, an operation command for the electric relief valve 55 is output in combination with other relief valve operation requests. When the engine control system is normal, the operation is commanded when there is another operation request or an operation request from the determination means 702. When it is detected that an undesired failure has occurred when an operation is commanded to the electric relief valve 55, for example, the signal terminal of the electric relief valve is short-circuited to the battery voltage, and the electric relief valve is connected to the electric relief valve. When an open command is issued, if the output circuit of the control unit burns out due to an overcurrent, it is preferable not to output the open command regardless of the aforementioned operation request.

  In block 704, a signal for specifically driving the electric relief valve is generated according to the operation command of the electric relief valve. For example, when an electronically controlled relief valve is a valve that opens and closes by an ONOFF signal, it outputs an ONOFF signal, and when it indicates the opening degree with a voltage signal or the like in an analog manner, it outputs a voltage signal at a desired opening degree. To do.

  When the required fuel amount (fuel injection amount) of the engine is smaller than the minimum fuel amount that can be discharged by the high-pressure pump 1 and the fuel balance of the common rail 53 may be excessively supplied by the processing described above, the relief valve The amount of fuel to be relieved from 55 can be made larger than the amount of fuel to be excessively supplied, so that the fuel pressure in the common rail 55 can be maintained within a desired pressure range without increasing the fuel pressure. Further, it is possible to effectively prevent the occurrence of a small amount of fuel injection due to an increase in the pressure difference between the upstream and downstream of the fuel injection valve, the inability to open the fuel injection valve, and fuel leakage due to exceeding the fuel pressure resistance.

  Here, in addition to the request for the fuel pressure in the common rail 53 to be less than the predetermined pressure described above, there is also a request for the fuel pressure to be greater than or equal to the predetermined pressure. For example, when the fuel pressure is lowered, the particle size of the injected fuel from the fuel injection valve 54 is increased, the fuel injection pulse width for supplying a desired amount of fuel is increased, which leads to defective combustion, and a desired fuel injection period. This is a fuel pressure request to avoid that fuel injection cannot be completed.

  Because of this requirement, there is a case where it is desired to keep the fuel pressure within a desired range even when the amount of fuel smaller than the minimum amount of fuel that can be supplied by the high-pressure pump is the amount of fuel required for the engine. A way of thinking in this case will be described with reference to FIG.

  FIG. 14 shows the supply amount and consumption amount of fuel with respect to the common rail on the vertical axis, and the state A is a case where the fuel amount smaller than the minimum fuel amount that can be supplied by the high-pressure pump is the fuel injection amount. In this case, as described above, since the fuel supply amount is excessive, the fuel pressure increases.

  In the state B, in the fuel consumption amount, the fuel amount as required is injected and the electric relief valve is opened. On the other hand, the fuel supply amount is a state in which the same amount as the fuel consumption amount is discharged and supplied from the high-pressure pump. In such a state, the fuel balance in the common rail is balanced, and the fuel pressure does not increase or decrease, and is an average value. Therefore, if the initial fuel pressure is within the desired range, it is possible to continue to achieve the desired fuel pressure by continuing to maintain this state, and if it is not the desired fuel pressure, from the high pressure pump until the desired pressure range is reached. By adjusting the fuel discharge amount, it is possible to lead to a desired fuel pressure range.

  In the state C, the minimum dischargeable amount of the high-pressure pump is supplied in the fuel supply amount, and in the fuel consumption amount, the fuel amount is injected as required, and the average flow rate is obtained by appropriately operating the electric relief valve. Is operated so that the fuel supply amount and the fuel consumption amount are equal to each other. Therefore, by adjusting the average flow rate of the electric control relief valve based on the same principle as in the state B, it is possible to lead to a desired fuel pressure range.

  An example of control for realizing state B is shown in FIG. This control calculates the control angle of the solenoid closing timing of the high-pressure pump, injects a fuel amount smaller than the minimum fuel amount that can be supplied by the high-pressure pump, and gives an open command to the electric relief valve, It starts in the state where the fuel amount corresponding to the upstream / downstream differential pressure of the valve is continuously relieved from the electric control relief valve.

  As described with reference to FIG. 5, the fuel discharge amount of the high-pressure pump is determined by the solenoid closing control angle, and there is a relationship that the discharging amount is large when the closing control angle is early and the discharging amount is small when the closing control angle is slow. First, in the block 1004, the relationship between the pump driving frequency, the required discharge amount and the solenoid closing operation angle, which is the performance characteristic of the applied high-pressure pump as shown in FIG. 8, is preset on the map.

  Here, in the above-described state, the required discharge amount to be discharged by the high-pressure pump in order to maintain the fuel pressure is the required fuel injection amount and the relief fuel amount. Therefore, the values are obtained in block 1003 and supplied to block 1004. I am doing so.

  Here, the amount of relief fuel is relieved in accordance with the upstream / downstream differential pressure while the relief valve 55 is being driven open, and the characteristic is a general characteristic of the fluid orifice as shown in FIG. Therefore, the relief amount is preferably obtained by appropriately measuring the upstream / downstream differential pressure by actual measurement or estimation, and the relief fuel amount is obtained by the characteristics shown in FIG.

  Therefore, the solenoid closing control angle obtained by map search in block 1004 calculates a value that balances the fuel balance of the common rail in a predetermined ideal state.

  Further, the function for correcting and adjusting the solenoid closing control angle is set in the block 1001 and the block 1002 in order to make the fuel pressure within a desired range as described above. Block 1001 calculates the difference between the target fuel pressure and the detected value of fuel pressure sensor 56 that actually detects the fuel pressure in the common rail, and block 1002 performs PI-type feedback control based on the difference, and solenoid The correction value for the closed control angle is calculated.

  The solenoid closing control angles obtained in block 1002 and block 1003 are summed in block 1005.

  Further, as explained in FIGS. 5 and 20, the solenoid closing response has a time-dependent response delay mainly. On the other hand, since this control calculates the control value in the control angle dimension, The solenoid response delay must be added to the control value. Therefore, the solenoid response delay correction value in the control angle dimension is obtained in block 1006 and added to the control value in block 1007 to obtain the final solenoid closing control angle.

  With this process, the fuel balance in the common rail is balanced, but even when the fuel pressure is not within the desired range, the pump discharge fuel amount can be adjusted up or down until the fuel pressure falls within the desired fuel pressure range by the feedback function using the fuel pressure. In addition, even if there is a deviation in high pressure pump characteristics between the predetermined ideal state and the actual environment set in the block 1003, a solenoid closed control angle that balances the fuel balance in the common rail can be provided by the feedback function.

  Therefore, the fuel pressure in the common rail 53 can be maintained within a desired range in a state where a fuel amount smaller than the minimum fuel amount that can be discharged by the high-pressure pump 1 is supplied by injection.

  As understood from the overall configuration, the present embodiment is configured based on the approximation that the solenoid closing control angle and the fuel discharge amount are linear as shown in FIG. An example of control that eliminates this approximation and can absorb the nonlinear characteristics of the pump drive cam is shown in FIG.

  The control example is the same as the control described in FIG. 10 in that it has a feedback function based on fuel pressure and a feedforward function corresponding thereto, but in block 1105, the feedback control request amount and the feedforward control request amount are converted into fuel. The main difference is that it is obtained in the quantity dimension.

  First, similarly to the block 1001, the difference between the target fuel pressure and the actual fuel pressure is obtained in a block 1101, and then converted into a fuel amount difference in a process 1102. The fuel pressure difference is caused by excess or deficiency of the amount of fuel in the common rail 53, and the relationship between the two is quantitatively related by the elastic coefficient of fuel and the fuel volume in the common rail 53. Therefore, the fuel pressure difference is multiplied by a predetermined gain. Thus, the excess or deficiency of fuel can be obtained. Further, when the elastic coefficient differs depending on the fuel property, it can be dealt with by separately detecting the fuel property and multiplying by a predetermined gain corresponding to the elastic property corresponding to the fuel property. Thus, the feedback control requirement amount can be obtained in the fuel amount dimension.

  On the other hand, in block 1104, as in block 1003, the fuel discharge request amount as the feedforward control request amount can be calculated.

  Therefore, as described above, in block 1105, the feedback control request amount and the feedforward control request amount can be summed in the fuel amount dimension to obtain the total required fuel discharge amount.

  In block 1106, the solenoid closing control angle corresponding to the total required fuel discharge amount can be obtained from the required fuel discharge amount and the pump drive frequency from the high-pressure pump characteristics similar to those in block 1004.

  The block 1107 and the block 1108 have the same function as the block 1006 and the block 1007, and as a result, the final solenoid closing control angle is obtained.

  With this process, the function described with reference to FIG. 10 can be realized, the non-linear characteristics of the pump drive cam can be absorbed, and the fuel pressure can be controlled with higher accuracy.

  The control operation described with reference to FIG. 10 or FIG. 11 will be described with reference to FIG. FIG. 15 shows a predetermined state from time 1503 to time 1506 in which the required fuel injection amount sequentially decreases from the change of the operating state such as the accelerator return over time, and becomes a required fuel injection amount smaller than the minimum fuel amount that can be supplied by the high-pressure pump. This shows the fuel injection amount, the fuel discharge amount, the electric relief valve opening, and the common rail pressure (fuel pressure) in the operating state where the required fuel injection amount sequentially increases again due to the change in the operating state after holding for a time. is there. The behavior of the fuel injection amount is indicated by a solid line, the behavior of the fuel discharge amount is indicated by a broken line, and the solid line and the broken line indicate the same behavior before a time point 1503 and after a short time after the time point 1506. Yes.

First, at time 1503, the fuel injection amount falls below a predetermined value Va . The predetermined value Va is a threshold value for determining whether the required fuel injection amount is smaller than the minimum fuel amount that can be supplied by the high-pressure pump as the control, as described in block 701 of FIG. At time 1506, it is determined that the required fuel injection amount is larger than the minimum fuel amount that can be supplied by the high-pressure pump. Here, a predetermined hysteresis is given to the threshold value Va , and the required fuel injection amount The frequent switching of the determination due to minute fluctuations is prevented.

  After time 1503, in response to the determination, the electric relief valve 55 is driven to open by the processing described with reference to FIG. At the same time, by the processing described with reference to FIG. 10 or FIG. 11, the fuel discharge amount is increased stepwise so that the fuel balance is commensurate with the amount of relief fuel from the electric control relief valve. The case shown in the figure shows a case where the stepwise increase in the fuel discharge amount is insufficient with respect to the relief fuel amount of the electric control relief valve, and thus a behavior in which the pressure in the common rail decreases immediately after time 1503 appears. . Due to the pressure drop, the feedback function in the processing described with reference to FIG. 10 or FIG. 11 acts, and the fuel discharge amount is increased in accordance with the difference between the target fuel pressure and the actual fuel pressure, thereby reaching the target fuel pressure after a predetermined required time. It shows the behavior that the pressure in the common rail rises.

  Next, a case where the target fuel pressure decreases by a predetermined value from a predetermined request (not shown) from the time point 1504 to a time point 1505 is shown. Accordingly, the feedback function similarly operates for a predetermined time from the time point 1504, and operates to reduce the common rail internal pressure to the target value by reducing the fuel discharge amount. Furthermore, after the predetermined time has elapsed, the target fuel pressure is maintained by maintaining a state in which the fuel balance is balanced. Next, at the time point 1505, the target fuel pressure increases by a predetermined value in the same manner as described above. Similarly, the feedback function is activated for a predetermined time from the time point 1505, and the fuel discharge amount is increased to increase the common rail internal pressure to the target value. It works to raise to the value. Furthermore, after a predetermined time has elapsed, the target fuel pressure is maintained by maintaining a state where the balance of fuel balance is maintained.

  Next, immediately before the time point 1506, the required fuel injection amount sequentially increases again due to the change in the operating state, and the feedforward function and the feedback function act so as to decrease the fuel discharge amount corresponding to the increase amount accordingly. At the time point 1506, the required fuel injection amount is larger than the minimum fuel amount that can be supplied by the high-pressure pump, and when the determination 702 in FIG. 7 is not established, the relief valve opening is closed and at the same time the processing described in FIG. 10 or FIG. Thus, the fuel discharge amount is decreased stepwise so that the fuel balance is commensurate with the relief fuel amount cancellation from the electric control relief valve 55. The case shown in the figure shows a case where the stepwise decrease in the fuel discharge amount is insufficient for the elimination of the relief fuel amount of the electric relief valve, so that the behavior in the common rail pressure increases immediately after the time point 1506 appears. Yes. Due to the pressure increase, the feedback function in the processing described in FIG. 10 or FIG. 11 works even when the electric control relief valve is closed, and the fuel discharge amount increase corresponding to the fuel injection amount increase is realized by the feedforward function. In addition, by decreasing the fuel discharge amount in accordance with the difference between the target fuel pressure and the actual fuel pressure, the common rail internal pressure is reduced to the target fuel pressure after a predetermined required time.

  The control content and operation for realizing the state B in FIG. 14 have been described above. Next, the control content for realizing the state C in FIG. 14 will be described.

  First, a control example of the control method for setting the pump discharge amount to the minimum dischargeable amount will be described with reference to FIG. A block 1705 calculates the solenoid closing control angle calculated by the feedback function and the feed forward function as described in FIG. 10 or FIG. Here, in the determination unit 1703, when the result output from the determination unit 1702 is 1, the calculation result of the block 1705 is not adopted, but the calculation result of the block 1704 is adopted, and the final solenoid closing control angle is adopted. Is output. Here, the block 1704 calculates the solenoid closing control angle at which the pump discharge amount is the minimum dischargeable amount from the pump drive frequency by table search.

  Further, the blocks 1701 and 1702 have the same functions as the blocks 701 and 702 in FIG. 7, and represent a case where the fuel amount smaller than the minimum fuel amount that can be discharged by the high-pressure pump becomes the required fuel amount of the engine.

  Therefore, in the control shown in FIG. 17, when the amount of fuel smaller than the minimum amount of fuel that can be discharged by the high-pressure pump becomes the required fuel amount of the engine, the solenoid close control angle of the high-pressure pump is set to the minimum that can be supplied by the high-pressure pump. The fuel amount can be fixed at a value.

  Next, a control example of a method for controlling the average flow rate of the electric control relief valve so that the fuel supply amount and the fuel consumption amount are equal will be described with reference to FIG. This control example is applied to a method of repeatedly driving the opening / closing drive by giving an ON / OFF command to the electric control relief valve. In such a case, the fuel flow rate characteristic of the electric control relief valve shows the characteristic as shown in FIG. 9 similar to the fuel injection valve, and the fuel relief amount in one open drive can be realized by the open drive pulse time. is there.

  First, in block 1601 and block 1602, as in block 1101 and block 1102 of FIG. 11, the difference between the target fuel pressure and the actual fuel pressure is obtained, and then the difference is converted into a fuel amount difference. The principle is the same as described above, and the amount of fuel to be removed from the common rail is obtained in order to set the fuel pressure to the target pressure.

  Although this control has an operation direction only in the fuel pressure decreasing direction, it is a feedback control with respect to the fuel pressure. Next, in block 1603, the control gain similar to the control gain of the PI control is multiplied and the convergence and stability of the feedback system are increased. To adjust. The control amount thus obtained is the fuel amount dimension and is multiplied by the flow coefficient in the standard upstream / downstream pressure difference state of the electric relief valve in processing 1604. The flow coefficient is the drive pulse time of the electric relief valve per unit fuel amount, and thereby converts the control amount from the fuel amount to the drive pulse time. Furthermore, since the upstream / downstream pressure difference of the electric control relief valve takes various values depending on the operating state, in step 1605, the fuel pressure correction coefficient corresponding to the upstream / downstream pressure difference is multiplied.

  On the other hand, as is known from the fuel injection amount characteristic of a general fuel injection valve, the electric control relief valve 55 has a drive pulse ON time that does not contribute to the passage of fuel due to a delay in the response of the valve body when the valve is open or closed. There is. The time means the X-axis intercept when the linear portion of the characteristic in FIG. 9 is extended, and is called an invalid pulse width. In block 1606, such a correction value is obtained. By summing up in processing 1607, a drive pulse width necessary for finally relieving a desired fuel amount can be obtained.

  The control operation described above will be described with reference to FIG. FIG. 18 shows a case where the target fuel pressure is realized only by the electric relief valve when the target fuel pressure is lowered, and can be applied to, for example, lowering the target fuel pressure during fuel cut. At time points 1801 to 1804 indicated by broken lines in the drawing, the processing described in FIG. 17 is executed at predetermined time intervals.

  First, at the time point 1801, since the target fuel pressure and the actual fuel pressure substantially coincide with each other, the drive pulse width of the electric control relief valve 55 is calculated as 0, and the drive pulse signal of the electric control relief valve 55 starts from the time point 1801. It remains OFF for the time 1802.

  Next, between the time point 1802 and the time point 1802, although not shown, the target fuel pressure decreases by a predetermined value from a predetermined request. Then, at time 1802, the control described with reference to FIG. 17 calculates the electric relief valve drive pulse width T1 so that the actual fuel pressure approaches the target fuel pressure, and the drive pulse signal is turned ON from time 1802 to T1. Accordingly, the actual fuel pressure decreases to the mechanical closure of the electric relief valve at a speed corresponding to the fuel relief flow rate with a predetermined delay time from the time point 1802.

  At the time point 1803, the actual fuel pressure has not reached the target fuel pressure in the drive pulse at T1, so the electric relief valve drive pulse width T2 is calculated in the same manner as at the time point 1802, and the drive pulse signal is output between the time point 1803 and T3. ON. Therefore, the actual fuel pressure shows the same behavior as described above.

  At time 1804, processing similar to that at time 1802 and time 1803 is performed, and as a result, the actual fuel pressure approaches the target fuel pressure with a predetermined fuel pressure control dead zone. Therefore, in the processing after the time point 1804, the same processing as that at the time point 1801 is performed, and thereafter, the electric control relief valve is not driven unless a difference between the target fuel pressure and the actual pressure occurs.

  By the operation described above, the actual fuel pressure can be reduced to the target fuel pressure by controlling the fuel relief amount from the electric control relief valve 55 by the control described in FIG. Here, the above-described method has been described for the electric relief valve that is used by intermittently driving ON / OFF. However, the electric relief valve that can control the opening area in an analog stepless manner, the fuel system different from the response characteristics described above Needless to say, the application form of the present invention is different from that of the present embodiment.

  The operation of the electric control relief valve control method described above in the same operating state as described in FIG. 15 will be described with reference to FIG. In FIG. 19, the valve opening average value is shown as an operation state of the electric control relief valve.

First, at time 1903, the fuel injection amount falls below the predetermined value V c. Predetermined value V c were described at block 1701 in FIG. 17, the threshold determining whether a small required fuel injection amount than the minimum fuel quantity that can be supplied in the high-pressure pump as a control.

  After the time point 1903, in response to the determination, the high-pressure pump is controlled to be the minimum discharge amount by the processing described in FIG. At the same time, the control described in FIG. 16 is driven. Since the fuel balance in the common rail becomes excessively supplied, the fuel pressure starts to increase gradually, but the relief valve average opening increases so as to decrease the fuel pressure by the control action described in FIG. Balance in degrees.

  In this state, the excess of the discharge amount of the high-pressure pump with respect to the fuel injection amount is equal to the fuel amount relieved from the electric control relief valve 55, and the fuel balance in the common rail 53 is balanced, so the fuel pressure is This is a state where a predetermined value is maintained. Further, it is understood that the predetermined value is within a target fuel pressure predetermined range by the control described in FIG.

  Next, from time 1904 to time 1905, a case where the target fuel pressure decreases by a predetermined value from a predetermined request is shown, as in FIG. Therefore, the feedback function is similarly activated for a predetermined time from the time 1904, and the common rail pressure is reduced to the target value by increasing the fuel relief amount. Further, after a predetermined time has elapsed, the target fuel pressure is maintained by maintaining a state where the balance of fuel balance is maintained. Next, at the time point 1905, the target fuel pressure increases by a predetermined value as described above. As a result, the target fuel pressure exceeds the actual fuel pressure. Therefore, the feedback function is activated until the target fuel pressure and the actual fuel pressure become equal immediately after the time point 1905, and the electric control relief valve 55 is kept closed. Immediately after that, since the actual fuel pressure exceeds the target fuel pressure, a feedback function is activated, and the common rail pressure is reduced to the target value by increasing the fuel relief amount. After the actual fuel pressure becomes substantially equal to the target fuel pressure, the target fuel pressure is maintained by maintaining a state where the fuel balance is balanced as described above.

  Next, immediately before the time point 1906, the required fuel injection amount sequentially increases again due to the change in the operating state, and the feedback function operates so as to maintain the actual fuel pressure that is going to decrease accordingly. At time 1906, the required fuel injection amount is larger than the minimum amount of fuel that can be supplied by the high-pressure pump, and the judgment 1702 in FIG. 17 is not satisfied, so that the high-pressure pump solenoid close control angle is set so that the target fuel pressure and the actual fuel pressure match. At the same time as switching to calculation, the electric relief valve control shown in FIG. 16 is stopped and the electric relief valve 55 is closed. The case shown in the figure shows a case where the minimum fuel discharge amount determination threshold is smaller than the actual value, and therefore, a behavior in which the pressure in the common rail increases immediately after the time 1906 appears. Due to the pressure increase, the feedback function in the processing described in FIG. 10 or FIG. 11 works even when the electric control relief valve is closed, and the fuel discharge amount increase corresponding to the fuel injection amount increase is realized by the feedforward function. In addition, by decreasing the fuel discharge amount in accordance with the difference between the target fuel pressure and the actual fuel pressure, the common rail internal pressure is reduced to the target fuel pressure after a predetermined required time.

  From the above description, according to the present embodiment, it is understood that the fuel pressure in the common rail 53 can be maintained within a desired range in a state in which a fuel amount smaller than the minimum fuel amount that can be discharged by the high-pressure pump 1 is being injected. I can do it.

  In the above description, it is assumed that the solenoid drive signal is turned off in the second half of the compression stroke of the pump drive cam and the valve body is closed, thereby enabling fuel discharge from the high pressure pump. However, in addition to this, the relationship between ON / OFF of the solenoid drive signal and the opening / closing of the valve body is opposite to the above, and the solenoid drive signal is turned ON in the latter half of the compression stroke of the pump drive cam, thereby closing the valve body. There is also a high-pressure pump having a structure that enables fuel discharge from the high-pressure pump.

  Further, as shown in FIG. 13, a predetermined engine solenoid drive signal during the suction stroke of the pump drive cam is turned ON, and the valve body is opened, so that fuel can be sucked into the high-pressure pump and sucked in the compression stroke. There is also a high-pressure pump having a structure for discharging discharged fuel.

  In the present embodiment, the high-pressure pump is driven by the camshaft. However, the high-pressure pump may be driven by another power source, for example, an electric motor.

The high pressure pump of any structure is the same in that the opening / closing operation of the valve body is synchronized with the up / down operation of the plunger of the pump by the electric drive of the solenoid to control the discharged fuel amount. Therefore, a phenomenon in which a delay occurs between the drive signal state and the mechanical opening / closing operation of the valve body is unavoidable, and therefore there is a minimum amount of fuel that can be discharged.
Therefore, the present invention can be applied to all high-pressure pumps having such characteristics.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various changes in design can be made without departing from the spirit of the present invention described in the claims. It can be done.

1 is a system configuration diagram showing an embodiment of an engine high-pressure fuel pump control device according to the present invention, together with an engine to which the engine is applied. The internal block diagram of the control unit shown by FIG. The whole block diagram of the fuel supply system provided with the high pressure fuel pump shown by FIG. FIG. 2 is a detailed enlarged cross-sectional view of the high-pressure fuel pump shown in FIG. 1. FIG. 4 is a timing chart for explaining the operation of the high-pressure fuel pump shown in FIG. 3. FIG. 6 is a supplementary explanatory diagram of the timing chart shown in FIG. 5. The block diagram with which it uses for description of the example of 1 control by the control apparatus shown by FIG. FIG. 4 is a graph for explaining characteristics of the high-pressure pump shown in FIG. 3. The figure used for description of the injection flow characteristic of a fuel injection valve. The block diagram with which it uses for description of the example of 1 control by the control apparatus shown by FIG. The block diagram with which it uses for description of the example of 1 control by the control apparatus shown by FIG. The graph used for description of the characteristics of the electric relief valve. The timing chart used for operation | movement description of a high pressure fuel pump. The figure used for description of the fuel balance of a common rail. The timing chart with which it uses for operation | movement description of the example of control by the control apparatus shown by FIG. The block diagram with which it uses for description of the example of 1 control by the control apparatus shown by FIG. The block diagram with which it uses for description of the example of 1 control by the control apparatus shown by FIG. The timing chart with which it uses for operation | movement description of the example of control by the control apparatus shown by FIG. The timing chart with which it uses for operation | movement description of the example of control by the control apparatus shown by FIG. FIG. 4 is a timing chart for explaining the operation of the high-pressure fuel pump shown in FIG. 3.

Explanation of symbols

1 High Pressure Fuel Pump 3 Lifter 4 Lowering Spring 8 Solenoid Valve 51 Low Pressure Fuel Pump 53 Common Rail 54 Fuel Injection Valve 55 Electric Relief Valve (Fuel Relief Valve)
56 Fuel pressure sensor 200 Solenoid 507 In-cylinder injection engine 515 Control unit

Claims (5)

Discharge amount control means for controlling the discharge amount of the high pressure fuel pump by supplying an electric signal to a solenoid for adjusting the fuel discharge amount of the high pressure fuel pump, and a common rail for accumulating and holding the fuel discharged by the high pressure fuel pump A fuel deriving unit that guides fuel in the common rail to a fuel injection valve, a fuel relief valve that relieves fuel from the common rail, and a relief valve opening degree control unit that controls the opening degree of the fuel relief valve. A high pressure fuel pump control device comprising:
The relief valve opening control means compares a minimum fuel amount that can be discharged by the high-pressure fuel pump with a fuel supply amount injected and supplied from the fuel injection valve, and the minimum fuel amount that can be discharged is the fuel supply amount. The high-pressure fuel pump control device for an engine is characterized in that the fuel relief valve is opened or its opening degree is increased when the fuel relief valve is approximately equal to or greater than. The discharge amount control means controls the discharge amount of the high-pressure fuel pump to be the minimum dischargeable fuel amount, and the relief valve opening control means controls the discharge amount of the high-pressure fuel pump and the fuel supply amount. The high-pressure fuel pump control device for an engine according to claim 1, wherein the opening degree is controlled so that a difference from the fuel relief valve is relieved from the fuel relief valve. It has means for detecting the fuel pressure in the common rail, and the relief valve opening control means controls the opening of the fuel relief valve so that the fuel pressure in the common rail becomes a target value. The high-pressure fuel pump control device for an engine according to claim 2. The relief valve opening control means holds the fuel relief valve at a predetermined opening, and the discharge amount control means determines that the sum of the fuel amount relieved from the fuel relief valve and the fuel supply amount is the high pressure fuel. The high-pressure fuel pump control device for an engine according to claim 1, wherein the discharge amount is controlled so as to be discharged from the pump. The fuel pressure in the common rail is detected, and the discharge amount control means controls the discharge amount of the high-pressure fuel pump so that the fuel pressure in the common rail becomes a target value. 4. A high-pressure fuel pump control device for an engine according to 4.

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