JP2011185125A - Control device of accumulator fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an accumulator fuel injection device capable of determining the static leak amount of a fuel injection valve at high frequency and with accuracy, and increasing the accuracies of various control that utilizes fuel leak amounts. <P>SOLUTION: The control device for an accumulator fuel injection device is capable of feedback control of the pressure of a common rail by control of a flow control valve based on a deviation between the desired pressure of the common rail and actual pressure, and includes a fuel non-injection state detection means for detecting a fuel non-injection state in which fuel injection quantity is zero during operation of the internal combustion engine, a desired pressure changing means for changing the desired pressure to a predetermined learning value while the fuel non-injection state is detected, and a static leak amount learning means for learning a static leak amount based on a control parameter of the flow control valve under a state in which a deviation between desired pressure and the actual pressure is within a predetermined range and under a state in which actual pressure is stable, after the desired pressure has been changed to the learning value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a control device for an accumulator fuel injection device. In particular, the present invention relates to a control device for an accumulator fuel injection device configured to be able to learn the amount of fuel flowing out from a region where high-pressure fuel flows.

  Conventionally, as a device for injecting fuel into a cylinder of an internal combustion engine such as a vehicle, it is supplied from a low pressure pump that pumps fuel from a fuel tank and supplies it to a high pressure pump, a high pressure pump that pressurizes and pumps fuel, and a high pressure pump. There is a pressure accumulator type fuel injection device that includes a common rail that stores fuel and a plurality of fuel injection valves that are connected to the common rail. In this pressure accumulation fuel injection device, the injection pressure is adjusted by controlling the pressure of the common rail (hereinafter referred to as “rail pressure”) in accordance with the operating state of the internal combustion engine, the amount of operation by the driver, and the like.

  The rail pressure is controlled, for example, by adjusting the flow rate of fuel by a flow rate control valve provided in the fuel passage between the low pressure pump and the high pressure pump, and adjusting the flow rate of fuel supplied from the high pressure pump to the common rail. (This control is hereinafter referred to as “supply amount control”). As another method of controlling the rail pressure, there is a method of adjusting the flow rate of fuel discharged from the common rail by a pressure control valve connected to the common rail (hereinafter, this control is referred to as “discharge amount control”). .

  The rail pressure control based on the supply amount control or the discharge amount control is a feedback control that performs control so that the actual rail pressure detected by the rail pressure sensor or the like (hereinafter referred to as “actual rail pressure”) becomes the target pressure. Is due to. In the case of emission control, it is easy to obtain control responsiveness because the amount of fuel discharged from the common rail is adjusted. However, in the case of supply control, the change in flow rate due to the movement of the flow control valve becomes the rail pressure. Since it takes time to be reflected, control responsiveness tends to be low. Therefore, in the supply amount control, a combination of feedforward control that adjusts the reference flow rate based on the operating state of the internal combustion engine, the operation amount by the driver, and the like, and feedback control that is based on the deviation between the target pressure and the actual rail pressure. May be implemented.

  Here, in the fuel injection valve provided in the pressure accumulation type fuel injection device, the position of the needle valve that opens and closes the injection hole is configured to be controlled using the pressure of the fuel supplied from the common rail. Specifically, in the fuel injection valve, a back pressure chamber for applying pressure to the rear end side of the needle valve is formed. By introducing fuel into the back pressure chamber, the needle valve is seated on the valve seat surface. While closing the injection hole, a part of the fuel in the back pressure chamber is leaked by back pressure control means such as an electromagnetic solenoid so that the needle valve is lifted from the valve seat surface to open the injection hole.

  In this type of fuel injection valve, in addition to the fuel leak from the back pressure chamber (hereinafter, this fuel leak is referred to as “dynamic leak”), the gap is formed in the sliding portion of the needle valve or valve piston. There is a structure in which high-pressure fuel leaks to the low-pressure side (hereinafter, this fuel leak is referred to as “static leak”).

  Further, the high pressure pump used in the pressure accumulation type fuel injection device is configured to pressurize the fuel sent by the low pressure pump by the plunger in the pressurizing chamber and to feed it to the common rail. Even in this high-pressure pump, the fuel may leak to the low-pressure side through the gap in the sliding portion of the plunger (hereinafter, this fuel leak is referred to as “pump leak”).

  When the production of fuel injection valves and high-pressure pumps is carried out by mass production, it is inevitable that there will be variations in processing accuracy for each product and individual differences in these fuel leak characteristics. Further, these fuel leak characteristics may vary due to sliding wear or the like associated with the use of the pressure accumulation type fuel injection device. Usually, the rail pressure control program is constructed by using the median value or the like of various variation elements as a representative value. For this reason, variations in the fuel leak characteristics of the fuel injection valve and the high pressure pump greatly affect the rail pressure control.

  In consideration of such variations in fuel leak characteristics and the like, a fuel injection pressure control apparatus configured to acquire pressure characteristics for each target system has been proposed. Specifically, the fuel injection pressure control device feedback-controls the rail pressure to the target value through variable control of the drive current amount of the intake adjustment valve, and a predetermined stability condition indicating that the rail pressure is stable is established. In the meantime, a fuel injection pressure control device having a program for determining the fuel leak amount at that time based on the relational expression "fuel consumption = fuel injection amount by fuel injection valve + fuel leak amount" is disclosed. (See Patent Document 1).

JP 2008-215201 A (the whole sentence, all figures)

  However, the program provided in the fuel injection pressure control device of Patent Document 1 is based on the relational expression “fuel consumption = fuel injection amount by fuel injection valve + fuel leakage amount” in a state where fuel injection is being performed. The amount of fuel leak is obtained. Normally, when fuel injection is performed in the running state of the vehicle, the required torque constantly fluctuates, so it is rare that the rail pressure becomes stable, and control for actually obtaining the fuel leak amount is executed. The frequency is extremely low.

  Also, even if a stable rail pressure appears, the rail pressure cannot be changed freely in the fuel injection state. It takes a considerable period of time to learn the amount of fuel leak.

  On the other hand, among the fuel leaks in the accumulator fuel injector, static leaks and pump leaks in the fuel injectors are not only likely to cause errors due to individual differences during manufacturing and deterioration over time due to use, but also the degree of error Also, variations are likely to occur. Therefore, since the static leak of the fuel injection valve and the pump leak greatly affect the accuracy of the rail pressure control, it is possible to improve the accuracy of the rail pressure control only by accurately grasping the total amount of the static leak and the pump leak. .

  In addition to the rail pressure control, the amount of fuel leak is controlled not only for the rail pressure control but also for learning the relationship between the energization amount of the pressure control valve connected to the common rail and the passage flow rate, and for the abnormality diagnosis of the pressure control valve provided for the common rail. It is also used when performing control. Therefore, accurately grasping the total amount of the static leak and the pump leak of the fuel injection valve leads to increasing the accuracy of these controls.

  The inventor of the present invention pays attention to these points, and configures the control device for the accumulator fuel injection device so that the fuel leak amount can be learned by performing predetermined control in the fuel-free state of the internal combustion engine. The present inventors have found that the above-described problems can be solved and completed the present invention. That is, the present invention can accurately grasp the total amount of static leak and pump leak of the fuel injection valve with high frequency, and can improve the accuracy of various controls using the fuel leak amount. It is an object of the present invention to provide a control device for an accumulator fuel injection device.

  According to the present invention, a plurality of fuel injection valves capable of injecting fuel to be supplied into a cylinder of an internal combustion engine, a common rail connected to the plurality of fuel injection valves, and pressurizing and pressurizing fuel into the common rail. Used in a pressure-accumulation fuel injection device comprising a high-pressure pump for pressure feeding and a flow rate control valve capable of adjusting the flow rate of fuel supplied to the common rail by adjusting the flow rate of fuel introduced into the pressurizing chamber of the high-pressure pump. In a control device for an accumulator fuel injection system capable of feedback control of a common rail pressure by controlling a flow rate control valve based on a deviation between a common rail target pressure and an actual pressure, the fuel injection amount is zero during operation of the internal combustion engine. A fuel non-injection state detecting means for detecting a fuel non-injection state, and changing the target pressure to a predetermined learning value while the fuel non-injection state is detected After changing the target pressure to the learning value, the control parameter of the flow rate control valve in the state where the deviation between the target pressure and the actual pressure is within the predetermined range and the actual pressure is stable And a fuel leak amount learning means that learns the fuel leak amount based on the control device for the pressure accumulating fuel injection device.

  Further, in configuring the control device for the accumulator fuel injection device according to the present invention, the target pressure changing means changes the target pressure to a plurality of different learning values while the fuel non-injection state continues, and the fuel leak amount learning means It is preferable to learn the fuel leak amount corresponding to each learning value.

  Further, when configuring the control device for the pressure accumulator type fuel injection device of the present invention, the control device estimates the target injection amount of fuel to be injected from the fuel injection valve, and the estimated dynamic leak that occurs to realize the fuel injection of the target injection amount. The reference flow rate for calculating the reference flow rate of the fuel that passes through the flow control valve based on the estimated static leak amount corresponding to the target pressure obtained based on the amount and the relationship between the common rail pressure and the reference static leak amount And a control flow rate calculation means for calculating a control flow rate by adding and subtracting a reference flow rate using a control parameter obtained based on a deviation between the target pressure and the actual pressure. It is preferable to correct the reference flow rate based on the fuel leak amount learned by the leak amount learning means.

  Further, when configuring the control device for the pressure accumulator type fuel injection device of the present invention, the reference flow rate calculation means can correct the reference flow rate by using the deviation between the reference static leak amount and the learned fuel leak amount. preferable.

  In configuring the control device for the pressure accumulator type fuel injection device of the present invention, it is preferable that the reference flow rate calculating means corrects the reference flow rate when the target pressure changes by a predetermined threshold value or more.

  Since the control device of the accumulator fuel injection device according to the present invention is configured to execute the learning control of the fuel leak amount using the fuel non-injection state, the fuel injection amount and the dynamic leak amount of the fuel injection valve Is used to accurately determine the total amount of static and pump leaks. Further, since the learning control is executed in a fuel-free injection state that occurs at a relatively high frequency in the traveling state of the vehicle, the learning control of the fuel leak amount can be executed at a high frequency. Moreover, since the rail pressure is a learning control that is executed in a fuel-free injection state that does not affect the running performance of the vehicle, the rail pressure for learning the amount of fuel leakage can be set freely, and the desired rail can be set. The total amount of static and pump leaks at pressure can be learned. Therefore, it is possible to accurately learn the total amount of static leaks and pump leaks at various values of rail pressure in a relatively short period of time, and to improve the accuracy of various controls using the fuel leak amount. .

  Further, in the control device for an accumulator fuel injection device of the present invention, while the fuel non-injection state continues, the target pressure changing means changes the target pressure to a plurality of different learning values, and the fuel leak amount learning means By configuring to learn the amount of fuel leak at the learning value, the amount of fuel leakage at multiple rail pressures is learned during a single fuel-injection state, and learning at different values of rail pressure is possible. Be able to run in a short time.

  Further, in the control device for an accumulator fuel injection device according to the present invention, the reference flow rate calculation means is configured to correct the reference flow rate using the fuel leak amount learned by the fuel leak amount learning means, whereby the common rail The control responsiveness when the rail pressure is controlled by the feedback control of the flow rate of the fuel supplied to the fuel can be improved.

  Further, in the control device for the accumulator fuel injection device of the present invention, the reference flow rate calculation means performs the correction of the reference flow rate using the deviation between the reference static leak amount and the learned fuel leak amount, thereby reducing the static flow rate. The reference flow rate in consideration of the variation in the static leak amount and the pump leak amount is accurately obtained.

  Further, in the control device for an accumulator fuel injection device according to the present invention, the reference flow rate calculation means executes the correction of the reference flow rate when the target pressure of the rail pressure control changes by a predetermined threshold value or more, so that the actual rail pressure and The correction is executed only in a situation where the deviation from the target pressure becomes large, and the load on the control device is reduced.

It is a figure for demonstrating the whole structure of the pressure accumulation type fuel-injection apparatus concerning embodiment of this invention. It is a block diagram for demonstrating the structure of the control apparatus of the pressure accumulation type fuel injection apparatus concerning embodiment of this invention. It is a figure for demonstrating the method of the calculation process of the control flow volume performed with a target flow volume calculating means. It is a time chart for demonstrating learning control of the amount of fuel leaks. It is a flowchart for demonstrating the learning control method of a fuel leak amount. It is a flowchart figure for demonstrating the rail pressure control method by supply amount control.

  Embodiments relating to a control device for an accumulator fuel injection device according to the present invention will be specifically described below with reference to the drawings as appropriate. However, the following embodiment shows one aspect of the present invention, and does not limit the present invention, and can be arbitrarily changed within the scope of the present invention.

In addition, what attached | subjected the same code | symbol in each figure has shown the same member, and description is abbreviate | omitted suitably. Further, in this specification, the term “flow rate” means an amount (mm ³ / unit time) circulated per unit time unless otherwise specified.

1. Accumulated Fuel Injection Device FIG. 1 is a schematic diagram showing a configuration example of an accumulator fuel injection device 50 that is controlled by the control device 70 according to the embodiment of the present invention. The accumulator fuel injection device 50 is a device for injecting fuel into a cylinder of an internal combustion engine (in this embodiment, a diesel engine) 40 mounted on a vehicle. The fuel tank 1, the low pressure pump 2, the high pressure A pump 5, a common rail 10, a fuel injection valve 13, a control device 70, and the like are provided.

  Among these, the low pressure pump 2 and the high pressure pump 5 are connected by a low pressure fuel passage 18, and the high pressure pump 5 and the common rail 10, and the common rail 10 and the fuel injection valve 13 are connected by high pressure fuel passages 37 and 39, respectively. Further, return pipes 30 a and 30 b for guiding leaked fuel to the fuel tank 1 are connected to the high-pressure pump 5 and the fuel injection valve 13. However, a part or all of the return pipes 30 a and 30 b connected to the high pressure pump 5 and the fuel injection valve 13 may be connected to the low pressure fuel passage 18 on the upstream side of the flow rate control valve 8.

  The low pressure pump 2 sucks up fuel in the fuel tank 1 and supplies low pressure fuel to the high pressure pump 5. As the low-pressure pump 2, an electric pump capable of controlling the applied voltage or a mechanical pump driven by an engine output is used.

  The high-pressure pump 5 pressurizes the low-pressure fuel sent by the low-pressure pump 2 by the plunger 7 in the pressurizing chamber 5 a and also feeds the pressurized high-pressure fuel to the common rail 10. The high-pressure pump 5 is configured to be driven by the output of the engine.

  A low-pressure fuel passage 18 between the low-pressure pump 2 and the high-pressure pump 5 is provided with a flow rate control valve 8 that controls the flow rate of fuel supplied to the pressurizing chamber 5 a of the high-pressure pump 5. As the flow control valve 8, for example, an electromagnetic proportional control valve is used in which the stroke amount of the valve body is adjusted according to the magnitude of the supplied current value, and the area of the port through which the fuel passes is variable. The flow control valve 8 is used for rail pressure control by supply amount control, and energization control is performed by the control device 70. The actual rail pressure is adjusted by adjusting the flow rate of the fuel supplied to the pressurizing chamber 5 a by the flow rate control valve 8 and adjusting the flow rate of the fuel supplied to the common rail 10. Specific contents of the rail pressure control will be described later.

  A pressure regulating valve 14 is connected upstream of the flow control valve 8. The pressure control valve 14 is connected to a return pipe 30 a that leads to the fuel tank 1. In the present embodiment, the pressure regulating valve 14 is an overflow valve that is opened when the difference between the front and rear pressures, that is, the difference between the pressure in the low pressure fuel passage 18 and the pressure on the return side exceeds a predetermined value. ing.

  The low-pressure fuel passage 18 is provided with a fuel temperature sensor 15 used for detecting the fuel temperature. The sensor signal of the fuel temperature sensor 15 is sent to the control device 70 and used for calculation of the fuel temperature.

  The common rail 10 temporarily accumulates high-pressure fuel pumped from the high-pressure pump 5 and supplies high-pressure fuel to the plurality of fuel injection valves 13. That is, the rail pressure becomes the fuel injection pressure. A rail pressure sensor 21 is attached to the common rail 10. The sensor signal of the rail pressure sensor 21 is sent to the control device 70 and used for the calculation of the actual rail pressure.

  The fuel injection valve 13 includes a nozzle body provided with an injection hole and a needle valve that closes the injection hole. The fuel injection valve 13 is applied to the back pressure control unit by the control device 70 to control the back end of the needle valve. When the pressure is released, the injection hole is opened and fuel is injected into the cylinder of the engine. As the fuel injection valve 13, for example, an electromagnetic control type fuel injection valve provided with a solenoid valve as a back pressure control unit, or an electrostrictive type fuel injection valve provided with a piezo element as a back pressure control unit is used. A return pipe 30b is connected to the fuel injection valve 13, and a dynamic leak caused by back pressure control of the needle valve and a static leak leaking from a sliding portion such as a needle valve are fueled via the return pipe 30b. Returned to tank 1.

  In addition, the structure of the pressure accumulation type fuel-injection apparatus 50 concerning this embodiment is a conventionally well-known thing.

2. Control Device FIG. 2 is a functional block diagram showing portions related to rail pressure control, fuel injection control, and fuel leak amount learning control in the configuration of the control device 70 of the accumulator fuel injection device of this embodiment. A block diagram is shown.

  The control device 70 is configured around a microcomputer (not shown) having a known configuration, and includes rail pressure detection means 71, target fuel injection amount calculation means 72, fuel injection valve control means 73, Target rail pressure calculation means 74, target flow rate calculation means 75, flow rate control valve control means 76, fuel non-injection state detection means 77, target pressure change means 78, pressure stable state detection means 79, fuel leak amount Learning means 80 is provided. Each of these means is realized by executing a program by a microcomputer.

  Although not shown, the control device 70 is output from the fuel temperature sensor 15 provided in the accumulator fuel injection device 50, the accelerator sensor provided in the vehicle, the rotational speed sensor or the crank angle sensor provided in the engine, and the like. It is possible to detect the fuel temperature Tf, the accelerator operation amount Acc, the engine speed Ne, the crank angle θc, etc. Further, the control device 70 is provided with storage means such as a RAM (Random Access Memory) (not shown), and stores various information to be read and the calculation results of each means.

  Among these, the rail pressure detecting means 71 is configured to read the sensor signal S1 of the rail pressure sensor 21 and detect the actual rail pressure Pact. Further, the target fuel injection amount calculation means 72 is configured to read the engine speed Ne and the accelerator operation amount Acc and obtain the target fuel injection amount Qtgt to be injected into the engine cylinder based on the map information. .

  The fuel injection valve control means 73 reads the actual rail pressure Pact detected by the rail pressure detection means 71 and the target fuel injection amount Qtgt obtained by the target fuel injection amount calculation means 72, and based on the map information, the fuel injection valve The energization amount and the energization time of 13 are obtained, and the energization control of the fuel injection valve 13 is executed in accordance with the injection timing according to the crank angle θc.

  The target rail pressure calculating means 74 is configured to read the engine speed Ne and the accelerator operation amount Acc and obtain the target rail pressure Ptgt based on the map information.

  The target flow rate calculation means 75 is configured to read the target rail pressure Ptgt and the actual rail pressure Pact and perform feedback control so that the actual rail pressure Pact becomes the target rail pressure Ptgt. In the control device 70 of the present embodiment, the target flow rate calculation means 75 includes a reference flow rate calculation means 75A for obtaining a reference flow rate Fpre-cont of fuel that passes through the flow rate control valve 8, a target rail pressure Ptgt, and an actual rail pressure Pact. And a control flow rate calculation means 75B that calculates a control flow rate Fcurrent of fuel that passes through the flow rate control valve 8 by adding or subtracting the reference flow rate Fpre-cont based on the difference ΔP.

  The reference flow rate calculation means 75A estimates the flow rate of the fuel flowing out from the high pressure region communicating with the common rail 10 based on the information on the engine operating state and the driver's travel request, and the flow rate of fuel corresponding to the flow rate is determined. It has a function of adjusting the passage flow rate of the flow rate control valve 8 in advance so as to be supplemented to the common rail 10. In the case of the configuration of the accumulator fuel injection device 50 of the present embodiment, the fuel flowing out from the high pressure region communicating with the common rail 10 is fuel injected from the fuel injection valve 13, dynamic leak and static leak of the fuel injection valve 13. Consists of.

Therefore, in the present embodiment, the reference flow rate calculation means 75A reads the engine speed Ne and the target fuel injection amount Qtgt (mm ³ ), and based on the map information, the fuel injection flow rate Finj (mm ³ / sec) and the dynamic leak Obtain the flow rate Fdynamicleak (mm ³ / sec). The reference flow rate calculation means 75A reads the fuel temperature Tf and the target rail pressure Ptgt, and estimates static leak based on map information indicating the relationship between these information and the reference static leak flow rate FMstaticleak (mm ³ / sec). Obtain the flow rate Fstaticleak (mm ³ / sec).

  Further, between the passage flow rate of the flow rate control valve 8 and the flow rate of the fuel supplied to the common rail 10, a pump leak flow rate Fpumpleak that leaks from the pressurizing chamber 5 a of the high pressure pump 5 through the sliding portion of the plunger 7. Differences in minutes occur. Therefore, in the control device 70 of the present embodiment, the calculated fuel injection flow rate Finj, the dynamic leak flow rate Fdynamicleak, and the estimated static leak flow rate Fstaticleak are added, and the fuel leak learned by the fuel leak amount learning means 80 described later. Correction is performed using the flow rate Fleak (total flow rate of static leak and pump leak), and the reference flow rate Fpre-cont is obtained. Specifically, the reference flow rate Fpre-cont is corrected by adding or subtracting the difference ΔFleak between the learned fuel leak flow rate Fleak and the estimated static leak flow rate Fstaticleak.

  The control flow rate calculation means 75B is a flow rate of fuel corresponding to the difference ΔP between the target rail pressure Ptgt and the current actual rail pressure Pact with respect to the reference flow rate Fpre-cont obtained by the reference flow rate calculation means 75A. Are added and subtracted to obtain a control flow rate Fcurrent that is a target value when the flow rate control valve 8 is actually controlled. That is, the control flow rate calculation means 75B has a function of feedback controlling the flow rate of the fuel passing through the flow rate control valve 8 based on the difference ΔP, and the feedback control is configured to be executed by PID control. .

  Here, the basic calculation logic of the calculation process performed by the target flow rate calculation means 75 will be described in more detail based on FIG. This arithmetic logic is repeatedly executed every fixed cycle.

In this calculation logic, first, based on the engine speed Ne and the target fuel injection amount Qtgt (mm ³ ), the fuel injection flow rate Finj (mm ³ / sec) and the dynamic leak flow rate Fdynamicleak (mm ³ generated in the fuel injection valve 13). / sec) and an estimated static leak flow Fstaticleak (mm ³ / sec) from the fuel injection valve 13 based on the fuel temperature Tf and the target rail pressure Ptgt.

  The fuel injection flow rate Finj, dynamic leak flow rate Fdynamicleak, and estimated static leak flow rate Fstaticleak are added, and the learned fuel leak flow rate Fleak (the total flow rate of static leak and pump leak) and the estimated static The reference flow rate Fpre-cont is obtained by adding or subtracting the difference ΔFleak from the static leak flow rate Fstaticleak.

  Further, the deviation ΔP between the target rail pressure Ptgt and the current actual rail pressure Pact is obtained, and the flow rate Fpid of the fuel for eliminating the deviation ΔP is obtained by PID control, and the flow rate Fpid that is the output result of this PID control is obtained. The control flow rate Fcurrent is obtained by adding / subtracting to the reference flow rate Fpre-cont.

  When the target rail pressure Ptgt is set to a certain value, the reference flow rate Fpre-cont is maintained at a constant value by feedforward control, while the control flow rate Fcurrent is controlled by the feedback control so that the actual rail pressure Pact becomes the target rail pressure Ptgt. It gradually becomes more stable as it approaches.

  Returning to FIG. 2, the flow rate control valve control means 76 is configured to obtain the energization amount Ameun based on the control flow rate Fcurrent obtained by the target flow rate calculation means 75 and execute the energization control of the flow rate control valve 8. Yes.

  Each means described so far is a means used for executing control of the fuel injection valve 13 and control of the flow rate control valve 8 in the operating state of the engine. On the other hand, the fuel non-injection state detecting unit 77, the target pressure changing unit 78, the pressure stable state detecting unit 79, and the fuel leak amount learning unit 80 mainly have a fuel leak flow rate Fleak (total flow rate of static leak and pump leak). It is used to execute learning control.

  The fuel non-injection state detection unit 77 reads the target fuel injection amount Qtgt calculated by the target fuel injection amount calculation unit 72 and detects the fuel non-injection state of the engine. The fuel non-injection state mainly occurs when the accelerator is released.

  The target pressure changing means 78 is a rail pressure at which the actual rail pressure Pact learns the fuel leak flow rate Fleak when the non-fuel injection state is detected (hereinafter, this rail pressure is referred to as “learning rail pressure”) Pstudy. In this way, an instruction is sent to the target rail pressure calculation means 74 so as to change the target rail pressure Ptgt to the learned rail pressure Pstudy. The change of the target rail pressure Ptgt by the target pressure changing means 78 is executed in order to change the passage flow rate of the flow rate control valve 8.

  As the value of the learning rail pressure Pstudy to be set, a value different from the target rail pressure Ptgt set before the change is selected from among the rail pressure values that can be actually controlled in the running state of the vehicle, and in a predetermined order. Or, it is set repeatedly at random. Further, the target rail pressure Ptgt may be changed once for each no-injection state of fuel, or learning of the fuel leak flow rate Fleak is completed every predetermined time or while the no-injection state of fuel continues. You may make it change in multiple times whenever it does. In the control device 70 of the present embodiment, the target pressure changing means 78 is configured to continuously change the target rail pressure Ptgt by raising or lowering it stepwise while the non-fuel injection state continues.

  After the target rail pressure Ptgt is changed by the target pressure changing means 78, the pressure stable state detecting means 79 has a deviation ΔP between the actual rail pressure Pact and the target rail pressure Pact within a predetermined range, and PID control. By detecting that the output result is stable, the stable state of the actual rail pressure Pact is detected. By detecting the stable state of the actual rail pressure Pact, the fuel leak flow rate Fleak at a certain learning rail pressure Pstudy can be accurately learned. The threshold value ΔP0 within the range for measuring the stable state of the actual rail pressure Pact can be appropriately set in consideration of the balance between the accuracy of the correction result and the time required for learning control. As an example, the threshold value ΔP0 of the deviation ΔP can be set to 0.5 MPa.

  However, if the time from when the target rail pressure Ptgt is changed to when the deviation ΔP between the actual rail pressure Pact and the target rail pressure Ptgt is within a predetermined range and the actual rail pressure Pact is stabilized can be assumed in advance. The stable pressure state detecting means 79 may be omitted. In this case, the timing for learning the fuel leak amount Fleak is set in advance.

  When the stable state of the actual rail pressure Pact is detected by the pressure stable state detecting means 79, the fuel leak amount learning means 80 is an I term (PID control) executed by the control flow rate calculating means 75B of the target flow rate calculating means 75. The integral term) is read and the value is learned as the difference ΔFleak between the fuel leak flow rate (the total flow rate of static leak and pump leak) Fleak and the estimated static leak flow rate Fstaticleak at the set learning rail pressure Pstudy It has become. In the present embodiment, the fuel leak amount learning means 80 simultaneously reads the fuel temperature Tf at the time of learning, and learns the difference ΔFleak of the leak flow rate at a predetermined fuel temperature Tf and a predetermined learning rail pressure Pstudy. Yes.

  In the present embodiment, the fuel leak amount learning means 80 reads the I term of PID control a plurality of times and learns the average of the read values as the difference ΔFleak while the actual rail pressure Pact is in a stable state. It is configured. Hereinafter, the point that the I term in the PID control of the flow rate of the fuel passing through the flow rate control valve 8 can be learned as the difference ΔFleak in the leak flow rate will be described with reference to FIG.

  FIG. 4 shows the target rail pressure Ptgt, the actual rail pressure Pact, the reference static leak flow rate FMstaticleak stored in advance in the control device 70, and the flow rate when the target rail pressure Ptgt is changed stepwise in the no fuel injection state. The transition of the control flow rate Fcurrent of the control valve 8, the P term Fmeun-p of PID control, and the I term Fmeun-i of PID control is shown.

  In the fuel non-injection state, the fuel injection flow rate Finj and the dynamic leak flow rate Fdynamicleak are zero. Therefore, of the fuel that has passed through the flow control valve 8, the fuel that flows out to the low pressure side without being held by the common rail 10 is It is only due to the pump leak and the static leak of the fuel injection valve 13. Therefore, in the no fuel injection state, the control flow rate Fcurrent of the flow rate control valve 8 coincides with the fuel leak flow rate (the total flow rate of pump leak and static leak) Fleak. In addition, in the state where the difference ΔP between the target rail pressure Ptgt and the actual rail pressure Pact is close to zero, the P term Fmeun-p is almost zero. Therefore, the I term Fmeun-i is stored as the control flow rate Fcurrent. The difference ΔFleak from the static leak flow rate FMstaticleak is expressed.

  In FIG. 4, the actual rail pressure Pact is in a stable state during a period surrounded by a square indicated by a dotted line. The fuel leak amount learning means 80 reads the I-term Fmeun-i of PID control within this period, and learns the value as the differences ΔFleak1 to ΔFleak5 in the respective learning rail pressures Pstudy1 to Pstudy5. In the example of FIG. 4, learning of the fuel leak flow rate Fleak and the difference ΔFleak at a certain learning rail pressure Pstudy is performed in about 3 to 5 seconds, and the target rail pressure Ptgt is changed 6 times in about 30 seconds. It is understood that learning with a plurality of learning rail pressures Pstudy is possible during a single fuel non-injection state.

  The difference ΔFleak between the fuel leak flow rate Fleak and the reference static leak flow rate FMstaticleak learned in this way is used as a correction value for the reference flow rate Fpre-cont in the reference flow rate calculation means 75A, thereby changing the target rail pressure Ptgt. Immediately after, the flow rate of the fuel supplemented to the common rail 10 is adjusted with high accuracy. As a result, the time for approximating the actual rail pressure Pact to the target rail pressure Ptgt can be shortened by feedback control based on the difference ΔP between the target rail pressure Ptgt and the actual rail pressure Pact. Further, by accurately adjusting the flow rate of the fuel supplemented to the common rail 10, even when the target rail pressure Ptgt changes, the difference ΔP between the actual rail pressure Pact and the target rail pressure Ptgt becomes remarkably large. Thus, overshoot and undershoot are reduced, and rail pressure control can be performed with high accuracy.

3. Control Flow Next, the learning control of the fuel leak amount (total amount of static leak and pump leak) and the rail pressure control by the flow control valve, which are executed by the control device 70 of the accumulator fuel injection device of the present embodiment, are shown in FIG. This will be described in detail with reference to FIGS.

(1) Fuel Leak Amount Learning Control Method First, fuel leak amount learning control will be described based on the flowchart of FIG. Note that this learning control may be executed all the time during the operation of the engine, or may be executed by interruption every predetermined period.

  In step S1 after the start, it is determined whether or not the engine is in a non-fuel injection state. If it is not in the no fuel injection state, the process proceeds to step S14, and it is determined whether or not a learning completion flag is set. If the learning completion flag is set, the routine is terminated and the routine returns to the start. On the other hand, if the learning completion flag is not set, the routine is ended after setting the learning completion flag in step S15. Return to the start.

  On the other hand, if it is determined in step S1 that there is no fuel injection, the process proceeds to step S2 where it is determined whether a learning completion flag is set. When the learning completion flag is set, after resetting the learning completion flag in step S3, the learning rail pressure Pstudy for learning the fuel leak flow rate Fleak is selected in step S4, and in step S5, the target rail pressure Ptgt is selected. Is set to the learning rail pressure Pstudy, and the process proceeds to step S6. On the other hand, if the learning completion flag is not set in step S2, the process proceeds directly to step S6.

  In step S6, the actual rail pressure Pact is detected, and it is determined whether or not the difference ΔP between the actual rail pressure Pact and the target rail pressure Ptgt is within a predetermined range. If the difference ΔP is not within the predetermined range, the routine is terminated and the process returns to the start. On the other hand, if the difference ΔP is within the predetermined range, the process proceeds to step S7 and is executed by the flow rate control means 75. It is determined whether or not the leak amount difference ΔFleak, which is the output result of the PID control being performed, is in a stable state.

  If the leak amount difference Fleak is not in a stable state, the routine is terminated and the process returns to the start. On the other hand, if the leak amount difference ΔFleak is in a stable state, the process proceeds to step S8, and the flow control valve 8 is actually operated. It is determined whether or not the current value Acurrent that is energized is close to the energization amount Ameun calculated by the flow control valve control means 76.

  When the energized current value Acurrent is not close to the calculated energization amount Ameun, this routine is terminated and the process returns to the start, while the current value Acurrent is approximated to the calculated energization amount Ameun. The process proceeds to step S9. Steps S6 to S8 are steps for determining whether or not the actual rail pressure Pact is in a stable state.

  In step S9, which is determined as YES in all steps from step S6 to step S8, the I term calculated by the fuel temperature Tf and the PID control of the flow rate control means 75 is read. The I term at this time coincides with the leak amount difference ΔFleak. Next, after the counter is advanced by 1 in step S10, it is determined in step S11 whether or not the counter value has reached a predetermined threshold value N0.

If the counter value has not reached the threshold value N0, the routine ends and the process returns to the start. On the other hand, if the counter value has reached the threshold value N0, the process proceeds to step S12, and the N0 I terms ( The average value of ΔFleak) is calculated, and the information stored as the learning rail pressure Pstudy set this time and the difference ΔFleak _{(Pstudy, Tf)} of the fuel leak flow rate at the detected fuel temperature Tf is updated. . Thereafter, in step S13, the counter is reset and a learning completion flag is set to end the present routine and return to the start.

  While changing the learning rail pressure Pstudy every time no fuel injection is detected, or changing the learning rail pressure Pstudy multiple times during one fuel injection, the fuel leak flow rate Fleak at various rail pressures Alternatively, by learning the leak flow difference ΔFleak, it is possible to learn the fuel leak flow rate Fleak at each rail pressure or the leak flow difference ΔFleak in a short period of time.

  Further, in the present embodiment, the learning rail pressure Pstudy and the fuel leak flow rate Fleak or the difference ΔFleak between the leak flow rates are learned for each fuel temperature Tf. Therefore, due to the viscosity variation due to the difference in the fuel temperature Tf. Learning including variations in flow rate. Therefore, the fuel leak flow rate Fleak or the difference ΔFleak of the leak flow rate at various rail pressures can be always accurately grasped.

(2) Rail Pressure Control Method by Supply Amount Control Next, rail pressure control by the flow control valve 8 will be described based on the flowchart of FIG. This learning control is always executed every predetermined cycle during engine operation.

  In step S21 after the start, the engine speed Ne, the accelerator operation amount Acc, the fuel temperature Tf, and the actual rail pressure Pact are detected. Next, in step S22, a target fuel injection amount Qtgt is calculated based on the engine speed Ne and the accelerator operation amount Acc. Next, in step S23, a target rail pressure Ptgt is calculated based on the target fuel injection amount Qtgt and the accelerator operation amount Acc.

  Next, in step S24, the fuel injection flow rate Finj and the dynamic leak flow rate Fdynamicleak are calculated based on the engine speed Ne and the target fuel injection amount Qtgt. In step S25, the fuel temperature Tf and the target rail pressure Ptgt are calculated. Calculate the estimated static leak flow rate Fstaticleak. In step S26, the fuel leak flow rate difference ΔFleak corresponding to the target rail pressure Ptgt is read. In step S27, the fuel injection flow rate Finj, dynamic leak flow rate Fdynamicleak, estimated static leak Fstaticleak, and fuel leak flow rate are calculated. The difference ΔFleak is added to calculate the reference flow rate ΔFpre-cont.

  Next, after calculating the difference ΔP between the target rail pressure Ptgt and the actual rail pressure Pact in step S28, in step S29, the flow rate feedback control value (the amount of fuel corresponding to the difference ΔP is eliminated) by PID control based on the difference ΔP. Flow rate) Calculate ΔFpid. In step S30, the control value ΔFpid obtained in step S29 is added to or subtracted from the reference flow rate Fpre-cont obtained in step S27 to calculate a control flow rate Fcurrent that is a target value for the passage flow rate of the flow rate control valve 8.

  Next, in step S31, an energization amount Ameun to the flow control valve 8 is calculated based on the control flow rate Fcurrent, and in step S32, an energization instruction is given to the actuator that energizes the flow control valve 8. End routine and return to start.

  By repeating this control flow, after the target rail pressure Ptgt is changed, the actual rail pressure Pact is gradually brought closer to the target rail pressure Ptgt. However, in the control device 70 of the present embodiment, the static The difference between the target rail pressure Ptgt and the actual rail pressure Pact even if the target rail pressure Ptgt is changed because the reference flow rate Fpre-cont is corrected in consideration of the static leak and the pump leak. Is avoided from becoming significantly large.

  Accordingly, the possibility of occurrence of overshoot or undershoot is reduced, and the actual rail pressure Pact can be brought close to the target rail pressure Ptgt in a short time by feedback control.

  Further, if the correction of the reference flow rate Fpre-cont at the time of obtaining the passage flow rate of the flow rate control valve 8 is accurately performed, even if only the feedforward control of the flow rate control valve 8 is performed, The accuracy of rail pressure control can be improved.

4). Application Example When feedback control based on the difference ΔP between the target rail pressure Ptgt and the actual rail pressure Pact is performed, the difference ΔP increases when the target rail pressure Ptgt is changed. Further, the larger the change amount of the target rail pressure Ptgt, the greater the difference ΔP that occurs. Therefore, the correction of the reference flow rate Fpre-cont using the difference ΔFleak obtained by the learning control of the fuel leak flow rate Fleak described above may be performed only when the target rail pressure Ptgt changes by a predetermined threshold value or more. .

  In the accumulator fuel injection device 50 described in the above embodiment, the common rail 10 includes a check valve that discharges a part of the fuel in the common rail 10 when the rail pressure exceeds a predetermined valve opening pressure. A pressure control valve that adjusts the rail pressure by adjusting the flow rate of the fuel discharged from the common rail 10 by controlling the energization amount may be provided. Even when the check valve is provided, the learning control of the fuel leak amount and the rail pressure control by the supply amount control can be performed in the same manner as already described. In the case where a pressure control valve is provided, in the case where the learning control of the fuel leak amount and the rail pressure control by the supply amount control are performed, the description has already been given except that the pressure control valve is kept closed. It can be implemented in the same manner as described above.

  Furthermore, in the present embodiment, the fuel leak flow rate Fleak learned by the fuel leak amount learning means 80 or the difference ΔFleak is used to correct the reference flow rate Fpre-cont in the supply amount control. The target to be corrected using the difference ΔFleak is not limited to this, and can be applied to other controls and diagnoses that are performed in consideration of fuel leakage from a region where high-pressure fuel flows.

  For example, the passage flow rate of the pressure control valve when energization of a predetermined value is performed on the electromagnetic control type pressure control valve connected to the common rail 10 under a certain rail pressure is “passage flow rate of the flow rate control valve 8 = It can be obtained from the relational expression of “pump leak flow rate Fpumpleak + fuel injection flow rate Finj + dynamic leak flow rate Fdynamicleak + static leak flow rate Fstaticleak”. Therefore, learning accuracy can be improved by performing learning control of the flow rate through the pressure control valve while performing correction using the learned fuel leak flow rate Fleak or the difference ΔFleak. As a result, the rail pressure can be accurately controlled even when the rail pressure control by the discharge amount control is performed.

  As another example, the learned fuel leak amount Fleak and the difference ΔFleak are not reflected in the control of the operation amount of the flow control valve 8 or the pressure control valve, but are reflected in the discharge efficiency of the high-pressure pump 5. Good. That is, by calculating the discharge efficiency of the high-pressure pump 5 based on the fuel leak amount Fleak and the difference ΔFleak, the flow rate of the fuel supplied to the common rail 10 can be obtained with high accuracy, and the rail pressure can be controlled with high accuracy. It becomes like this.

  As another example, based on the detected value of the rail pressure sensor 21 when the energization amount to the flow control valve 8 and the pressure control valve, the fuel injection amount, the discharge amount of the high-pressure pump 5 and the like are predetermined values. Even when the abnormality diagnosis of the rail pressure sensor 21 is performed, the accuracy of the abnormality diagnosis result of the rail pressure sensor 21 can be improved by performing correction using the fuel leak amount Fleak or the difference ΔFleak.

  Note that the correction method is not limited to the method of adding or subtracting the correction value, and may be a method of multiplying or dividing the correction coefficient.

1: fuel tank, 2: low pressure pump, 5: high pressure pump, 5a: pressurizing chamber, 7: plunger, 8: flow control valve, 10: common rail, 12: pressure control valve, 13: fuel injection valve, 14: pressure Adjustment valve, 15: fuel temperature sensor, 18: low pressure fuel passage, 21: rail pressure sensor, 30a, 30b: return piping, 37, 39: high pressure fuel passage, 50: pressure accumulation type fuel injection device, 70: control device, 71 : Rail pressure detection means, 72: target fuel injection amount calculation means, 73: fuel injection valve control means, 74: target rail pressure calculation means, 75: target flow rate calculation means, 75A: reference flow rate calculation means, 75B: control flow rate calculation Means 76: Flow control valve control means 77: No fuel injection state detection means 78: Target pressure changing means 79: Pressure stable state detection means 80: Fuel leak amount learning means

Claims (5)

A plurality of fuel injection valves capable of injecting fuel to be supplied into a cylinder of the internal combustion engine; a common rail to which the plurality of fuel injection valves are connected; and a high pressure for pressurizing the fuel and feeding the pressurized fuel to the common rail Used in an accumulator fuel injection apparatus comprising: a pump; and a flow rate control valve capable of adjusting a flow rate of the fuel supplied to the common rail by adjusting a flow rate of the fuel introduced into a pressurizing chamber of the high pressure pump. In the control device for the accumulator type fuel injection device capable of feedback control of the pressure of the common rail by controlling the flow rate control valve based on the deviation between the target pressure of the common rail and the actual pressure,
Fuel non-injection state detecting means for detecting a fuel non-injection state in which the fuel injection amount becomes zero during operation of the internal combustion engine;
Target pressure changing means for changing the target pressure to a predetermined learning value while the fuel non-injection state is detected;
After changing the target pressure to the learning value, the control parameter of the flow control valve in a state where the deviation between the target pressure and the actual pressure is within a predetermined range and the actual pressure is stable Fuel leak amount learning means for learning the fuel leak amount based on
A control apparatus for an accumulator fuel injection apparatus, comprising:   The target pressure changing means changes the target pressure to a plurality of different learning values while the fuel non-injection state continues, and the fuel leak amount learning means is configured to change the fuel leak amount corresponding to each of the learning values. The control device for an accumulator fuel injection device according to claim 1, wherein The control device is
Based on a target injection amount of the fuel to be injected from the fuel injection valve, an estimated dynamic leak amount generated to realize fuel injection of the target injection amount, and a relationship between the pressure of the common rail and a reference static leak amount A reference flow rate calculation means for calculating a reference flow rate of the fuel that passes through the flow rate control valve based on an estimated static leak amount corresponding to the target pressure required for
Control flow rate calculation means for calculating a control flow rate by adding and subtracting the reference flow rate using a control parameter obtained based on a deviation between the target pressure and the actual pressure, and
The pressure-accumulation fuel injection device according to claim 1 or 2, wherein the reference flow rate calculation unit corrects the reference flow rate based on the fuel leak amount learned by the fuel leak amount learning unit. Control device.   4. The accumulator fuel injection apparatus according to claim 3, wherein the reference flow rate calculation means corrects the reference flow rate using a deviation between the reference static leak amount and the learned fuel leak amount. Control device.   5. The control device for an accumulator fuel injection device according to claim 3, wherein the reference flow rate calculation unit corrects the reference flow rate when the target pressure changes by a predetermined threshold value or more.

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