JP5441999B2 - Common rail pressure control device and control method, and accumulator fuel injection device - Google Patents

Description

  The present invention relates to a control device and control method for a common rail pressure, and an accumulator fuel injection device, and controls the pressure in the common rail by adjusting the amount of low pressure fuel fed to the high pressure pump and the amount of high pressure fuel discharged from the common rail. The present invention relates to a control device and control method for a common rail pressure, and an accumulator fuel injection device.

  Conventionally, as a device for injecting fuel into an internal combustion engine such as a diesel engine, a state in which a plurality of fuel injection valves are connected and a common rail for storing high-pressure fuel is provided, and the high-pressure fuel is supplied to each fuel injection valve Thus, an accumulator fuel injection device that enables precise fuel injection control by performing energization control of the fuel injection valve is used.

  Such an accumulator fuel injection device includes a low-pressure pump, a high-pressure pump, a common rail, and a fuel injection valve as main elements, and the fuel in the fuel tank is pumped to the high-pressure pump by the low-pressure pump and the high-pressure pump. The fuel is pressurized by the pump and pumped to the common rail, and high pressure fuel is supplied to each fuel injection valve. In this state, various fuel injection patterns to the internal combustion engine can be realized by controlling the valve opening timing and the valve opening time of the fuel injection valve by turning on and off the energization of the fuel injection valve.

  In this accumulator fuel injection device, the flow rate of the low-pressure fuel supplied to the pressurizing chamber of the high-pressure pump is adjusted, or part of the high-pressure fuel pumped to the common rail is returned to the low-pressure system. The pressure in the common rail (hereinafter referred to as “rail pressure”) is adjusted by using the control together (for example, see Patent Document 1).

  For example, when the temperature of the fuel injection device is low, such as immediately after starting an internal combustion engine, a large amount of high pressure fuel is pumped to the common rail without adjusting the flow rate of the low pressure fuel, and connected to the common rail according to the target value of the rail pressure. A control is performed to open and close the pressure control valve and return a part of the high-pressure fuel to the fuel tank. In such a rail pressure control by the pressure control valve, the rail pressure can be directly adjusted, so that the responsiveness is good and the fuel temperature rises due to a large amount of high pressure fuel being pumped. However, since the high-pressure fuel returned to the fuel tank becomes relatively large, the fuel utilization efficiency is lowered.

  On the other hand, after the temperature of the fuel injection device rises, the pressure control valve is closed and the opening of the flow control valve that controls the flow rate of the low-pressure fuel sent to the pressurizing chamber is adjusted according to the target value of the rail pressure, Control is performed to pump the required amount of high-pressure fuel to the common rail. In such rail pressure control using a flow control valve, only the required amount of high-pressure fuel is pumped to the common rail, so that the fuel utilization efficiency is improved, while the control device outputs an instruction for the opening of the flow control valve. Therefore, since the time difference occurs until the rail pressure actually fluctuates, the responsiveness tends to decrease.

Japanese Patent Laying-Open No. 2005-36794 (FIG. 1)

  By the way, in the accumulator fuel injection device, when the rail pressure becomes larger than the target pressure by a predetermined value or more, it is necessary to control the rail pressure so that it quickly approaches the target pressure, but the rail pressure is controlled by the flow control valve. In this case, a time difference is likely to occur after the indication of the opening degree of the flow control valve is output until the rail pressure actually fluctuates. Therefore, when the rail pressure is controlled by the flow control valve, when the rail pressure becomes larger than the target pressure by a predetermined value or more, the pressure control valve may be opened to reduce the rail pressure. .

  In particular, in the state where the rail pressure is controlled by the flow control valve, when the control for temporarily reducing the fuel injection amount (hereinafter referred to as “fuel injection cut control”) is executed while the accelerator is depressed. Although the fuel injection amount has decreased, the decrease in the pumping amount of high pressure fuel to the common rail cannot be followed and the rail pressure may exceed the allowable pressure of the high pressure fuel system. The fuel injection cut control is performed, for example, for the purpose of reducing transmission torque at the time of gear shift up of an automatic transmission specification vehicle.

  Once the opening control of the pressure control valve is performed at the time of such fuel injection cut control, the rail pressure once decreases, but then the pressure control valve is gradually closed and the opening of the flow control valve increases. Then, the rail pressure will start to rise. Furthermore, since the fuel injection cut control is ended before and after the opening and closing of the pressure control valve and the flow rate control valve, the rail pressure continues to gradually increase.

  After that, the rail pressure decreases due to the opening of the pressure control valve when the rail pressure increases and the opening of the flow control valve is reduced, and the opening of the pressure control valve and the flow control valve when the rail pressure decreases The increase in the rail pressure due to the increase in the rail pressure is repeated, and the hunting phenomenon of the rail pressure occurs. Such a rail pressure hunting phenomenon occurs in the conventional accumulator type fuel injection device so that the pressure control valve is always opened when the rail pressure becomes higher than the target rail pressure by a predetermined value or more. It depends on. When the rail pressure hunting phenomenon occurs, it becomes difficult to control the fuel injection amount, and the pressure pulsation in the high pressure fuel system may reduce the durability of the high pressure fuel system.

FIG. 5 is a timing chart showing the rail pressure hunting phenomenon when the conventional fuel injection cut control is executed. The fuel injection amount instruction value Qf, the pressure control valve set value Ppcv, the instruction flow rate Vmeun to the flow control valve, And the change of rail pressure Pr is shown.
In this chart, the set value Ppcv of the pressure control valve is larger than the target value Ptgt of the rail pressure during the period from t0 to t1 when the request for reducing the torque of the automatic transmission (hereinafter referred to as “torque reduction request”) is off. It is set to high P1. In this state, the pressure control valve is in a closed state. In addition, during the period from t0 to t1, the fuel injection amount instruction value Qf changes gently, and the instruction flow rate Vmeun to the flow control valve changes gently according to the change of the fuel injection amount instruction value Qf. . For this reason, the rail pressure Pr is maintained while being kept substantially at the rail pressure target value Ptgt.

  Here, when the torque reduction request is turned on at time t1 to shift the gear by the automatic transmission, the command value Qf of the fuel injection amount and the command flow rate Vmeun to the flow control valve are temporarily reduced. At this time, the amount of the high-pressure fuel discharged from the common rail to the outside due to the decrease in the high-pressure fuel injected from the fuel injection valve quickly decreases, while the output of the decrease instruction to the flow control valve provided on the inlet side of the high-pressure pump. There is a time difference between the timing and the timing until the flow rate of the high-pressure fuel actually pumped to the common rail decreases.

  Therefore, the rail pressure Pr starts to increase for a while after the time t1. Then, at time t2 when the deviation ΔP between the rail pressure Pr and the target value Ptgt of the rail pressure increases by a predetermined value ΔP0 or more, the set value Ppcv of the pressure control valve is reduced to the target value Ptgt of the rail pressure. Pr starts to decrease.

  Thereafter, when the difference ΔP between the rail pressure Pr and the target value Ptgt of the rail pressure becomes less than the predetermined value ΔP0 at time t3, the set value Ppcv of the pressure control valve is gradually returned to P1, but the rail pressure Pr further decreases. When the value falls below the target value Ptgt of the rail pressure, the instruction flow rate Vmeun to the flow control valve is increased at time t4. As a result, the rail pressure Pr starts to increase again, and thereafter, at time t5, the gear shift by the automatic transmission is completed, and the decrease in the fuel injection amount instruction value Qf is released, so that the rail pressure Pr temporarily stops increasing. Therefore, the instruction flow rate Vmeun to the flow control valve is further increased, and the rail pressure Pr increases again. Then, when the rail pressure Pr starts to increase again, the instruction flow rate Vmeun to the flow control valve is gradually reduced.

  Thereafter, the torque reduction request is turned off at time t6, and then the rail pressure Pr exceeds the target value Ptgt of the rail pressure. Further, at time t7, the deviation ΔP between the rail pressure Pr and the target value Ptgt of the rail pressure is a predetermined value. When ΔP0 or more is reached, the set value Ppcv of the pressure control valve is reduced again to the target value Ptgt of the rail pressure. As a result, since the rail pressure Pr starts to decrease at the time t8, when the rail pressure Pr falls below the rail pressure target value Ptgt at the time t9, the command flow rate Vmeun to the flow control valve is increased again. As a result, the rail pressure Pr begins to increase.

  Thereafter, the set value Ppcv of the pressure control valve is decreased every time the deviation ΔP between the rail pressure Pr and the target value Ptgt of the rail pressure exceeds a predetermined value ΔP0. The hunting phenomenon occurs due to repeated increase and decrease of the pressure Pr.

  In order to suppress the rail pressure hunting phenomenon that occurs for this reason, it is conceivable to set the opening and valve opening time appropriately when the pressure control valve is open. Since there are individual differences due to variations such as, the setting value changes individually. Therefore, even if the opening degree and valve opening time are set in accordance with a certain pressure control valve, it is difficult to prevent the hunting phenomenon of all common rail pressures.

  Therefore, the inventors of the present invention diligently tried to open the pressure control valve connected to the common rail during the fuel injection cut control during the rail pressure control by adjusting the flow rate of the low pressure fuel pumped to the high pressure pump. The inventors have found that the above-mentioned problems can be solved by limiting the number of valves, and have completed the present invention. That is, an object of the present invention is to provide a common rail pressure control device and control method, and an accumulator fuel injection device that can prevent rail pressure hunting caused by fuel injection cut control.

According to the present invention, the low pressure fuel in the fuel tank is pumped by the low pressure pump, the low pressure fuel is pressurized by the high pressure pump, and the high pressure fuel is pumped to the common rail connected to the plurality of fuel injection valves. In a common rail pressure control device for controlling the pressure in a common rail in an accumulator fuel injection device that injects high pressure fuel into a cylinder of an internal combustion engine, the flow rate of the low pressure fuel pumped to the high pressure pump according to the target pressure of the common rail During the adjustment, when the pressure in the common rail exceeds the target pressure by a predetermined value or more , the pressure in the common rail and the target are opened by opening the pressure control valve for discharging the high-pressure fuel in the common rail once. is configured to control to the difference in pressure below the predetermined value is performed, the fuel injection amount from the fuel injection valve is found to temporarily decrease Control of when the pressure in the common rail is greater than a predetermined value than the target pressure by that, the control device of common rail pressure, characterized in that so as to limit the number of control to be opened once the pressure control valve Provided and can solve the above-mentioned problems.

Further, in configuring the control unit of the common rail pressure of the present invention, as the number of the control to be opened once the pressure control valve is limited to one time, the opening degree at the time of a single opening, the fuel injection amount Preferably, it is set according to at least one of the position of the plunger of the high-pressure pump when the fuel pressure is temporarily reduced or the amount of decrease in the fuel injection amount.

In the common rail pressure control device of the present invention, the restriction on the number of times of control for opening the pressure control valve once is that the pressure in the common rail when the fuel injection amount is temporarily reduced is equal to or higher than a predetermined threshold value. It is sometimes preferred to do so.

  In the common rail pressure control device of the present invention, the control for temporarily reducing the fuel injection amount is performed to reduce the torque of the automatic transmission during gear shifting of the vehicle on which the internal combustion engine is mounted. It is preferable that

In addition, the common rail pressure control device of the present invention includes a rail pressure detection unit that detects the pressure in the common rail, a flow rate control unit that adjusts the flow rate of the low-pressure fuel supplied to the high-pressure pump according to the target pressure, A high pressure discharge control unit that performs control so that the difference between the pressure in the common rail and the target pressure is less than a predetermined value by opening the pressure control valve once when the pressure of the pressure becomes greater than the target pressure by a predetermined value or more; A valve opening number limiting unit that limits the number of times the control is performed to open the pressure control valve once by the high-pressure discharge control unit during execution of control in which the fuel injection amount from the fuel injection valve is temporarily reduced. preferable.

In another aspect of the present invention, the low pressure fuel in the fuel tank is pumped by a low pressure pump, the high pressure pump pressurizes the low pressure fuel, and the high pressure fuel is pumped to a common rail connected to a plurality of fuel injection valves. Low pressure pumped to a high pressure pump according to a common rail target pressure in a common rail pressure control method for controlling pressure in a common rail in an accumulator fuel injection device that injects high pressure fuel into a cylinder of an internal combustion engine from a fuel injection valve While the fuel flow is being adjusted, if the pressure in the common rail exceeds the target pressure by a predetermined value or more, the pressure control valve for discharging the high-pressure fuel in the common rail is opened once to open the common rail. The pressure in the common rail is reduced by controlling the difference between the target pressure and the target pressure to be less than the predetermined value .
Limiting the number of times the pressure control valve is opened once when the pressure in the common rail exceeds the target pressure by a control that allows the fuel injection amount from the fuel injection valve to be temporarily reduced. This is a method for controlling the common rail pressure.

According to still another aspect of the present invention, low-pressure fuel in a fuel tank is pumped by a low-pressure pump, and the high-pressure pump pressurizes the low-pressure fuel to a common rail connected to a plurality of fuel injection valves. In the accumulator type fuel injection device for injecting high pressure fuel into the cylinder of the internal combustion engine from the fuel injection valve, a flow rate control valve for controlling the flow rate of the low pressure fuel pumped to the high pressure pump, and a common rail provided in the common rail The pressure in the common rail can be controlled by controlling the flow control valve for discharging the high-pressure fuel and the flow control valve in accordance with the target pressure of the common rail. During this control, the pressure in the common rail is lower than the target pressure. When the pressure exceeds a predetermined value, the pressure control valve is opened once so that the difference between the pressure in the common rail and the target pressure is less than the predetermined value. A rail pressure control device, the rail pressure control device when the pressure in the common rail exceeds the target pressure by a predetermined value or more by control that temporarily reduces the fuel injection amount from the fuel injection valve. The pressure accumulation type fuel injection device is characterized in that the number of times of control for opening the pressure control valve once is limited.

  According to the control device and control method for the common rail pressure of the present invention, the number of times the pressure control valve is opened when the rail pressure becomes greater than the target pressure by a predetermined value or more during the fuel injection cut control is limited. For this reason, the rail pressure varies depending on the time difference from when the flow rate of the low-pressure fuel pumped to the high-pressure pump changes until the rail pressure changes due to the change in the flow rate of the high-pressure fuel pumped to the common rail along with the change in the low-pressure fuel flow rate. It is possible to prevent the rail pressure hunting phenomenon from being repeatedly raised and lowered. Even if the number of times the pressure control valve is opened is limited, after the fuel injection cut control is completed, the fuel injection amount stabilizes and the rail pressure begins to stabilize. The rail pressure is stably maintained by controlling the flow rate of the low-pressure fuel pumped to the pump.

  Further, according to the pressure accumulation type fuel injection device of the present invention, the common rail pressure control device that limits the number of times the pressure control valve is opened when the rail pressure becomes larger than the target pressure by a predetermined value or more during the fuel injection cut control. Thus, the rail pressure hunting phenomenon due to the fuel injection cut control is suppressed, the subsequent fuel injection amount is controlled with high accuracy, and the durability of the high pressure fuel system is prevented from being lowered due to the pressure amplitude.

It is a figure for demonstrating the 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 common rail pressure concerning embodiment of this invention. It is a timing chart for demonstrating the control method of the common rail pressure concerning embodiment of this invention. It is a flowchart for demonstrating the control method of the common rail pressure concerning embodiment of this invention. It is a timing chart for demonstrating the control method of the conventional common rail pressure.

  DESCRIPTION OF EMBODIMENTS Embodiments relating to a common rail pressure control device and control method, and an accumulator fuel injection device according to the present invention will be specifically described below with reference to the drawings. However, this 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.

1. Basic Configuration of Accumulation Type Fuel Injection Device FIG. 1 shows a schematic configuration of an accumulation type fuel injection device 50 according to an embodiment of the present invention.
An accumulator fuel injector 50 shown in FIG. 1 is an accumulator fuel injector that injects fuel into a cylinder of an automatic transmission internal combustion engine mounted on a vehicle. The accumulator fuel injector 50 includes a fuel tank 1, a low-pressure pump 2, and the like. The high-pressure pump 5, the common rail 10, the fuel injection valve 13, and the like are provided as main elements.

  The low pressure pump 2 and the high pressure pump 5 are connected by a low pressure fuel passage 18a, 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 37a and 37b, respectively. In addition, fuel leak passages 30 a to 30 c for returning discharged fuel to the fuel tank 1 are connected to the high-pressure pump 5, the common rail 10, the fuel injection valve 13, and the like.

  In the present specification, the “high pressure fuel system” means a region where the high pressure fuel spreads in the accumulator fuel injection device 50 and its constituent members. In the example of this embodiment, the high pressure fuel passages 37a, 37b, A common rail 10 and a fuel injection valve 13 are included.

  A flow rate control valve 8 for adjusting the flow rate of the low pressure fuel supplied to the high pressure pump 5 is provided in the middle of the low pressure fuel passage 18a. The overflow valve 14 is connected to the low pressure fuel passage 18a upstream of the flow control valve 8, and the pressure of the low pressure fuel is maintained at a predetermined value.

  The low pressure pump 2 pumps the low pressure fuel in the fuel tank 1 and pumps it, and supplies the low pressure fuel to the pressurizing chamber 5a of the high pressure pump 5 through the low pressure fuel passage 18a. A low-pressure pump 2 shown in FIG. 1 is an in-tank electric low-pressure pump provided in a fuel tank 1 in which low-pressure fuel is stored. The low-pressure pump 2 is driven by a voltage supplied from a battery and has a constant output and a constant flow rate. Pump fuel.

  However, the low-pressure pump 2 is not limited to the in-tank low-pressure pump, and may be provided outside the fuel tank 1. Further, the driving means of the low-pressure pump 2 may be a gear pump connected to the camshaft of the high-pressure pump 5 in addition to the electric pump.

  As the flow rate control valve 8 provided in the low pressure fuel passage 18b, for example, an electromagnetic proportional flow rate control valve whose passage area can be adjusted by controlling the energization amount by the control device 40 is used. By adjusting the flow rate of the low-pressure fuel supplied to the pressurizing chamber 5a of the high-pressure pump 5 by the flow control valve 8, the pumping amount of the high-pressure fuel from the high-pressure pump 5 to the common rail 10 is adjusted to control the rail pressure. can do.

  For example, immediately after the internal combustion engine is started, the opening degree of the flow control valve 8 is maintained large in order to quickly increase the temperature of the high-pressure fuel system. On the other hand, in the normal operation state of the internal combustion engine, in order to increase the fuel use efficiency with respect to the load of the accumulator fuel injection device 50, the flow control valve 8 depends on the required rail pressure, the required injection amount of the internal combustion engine, and the like. And the flow rate of the low-pressure fuel supplied to the pressurizing chamber 5a is adjusted. However, as compared with the rail pressure control by the pressure control valve 12 provided in the common rail 10, the time difference from the output of the instruction until the rail pressure changes becomes larger.

  The overflow valve 14 connected to the low-pressure fuel flow path 18 a upstream of the flow control valve 8 is connected to a fuel leak passage 30 a communicating with the fuel tank 1. The overflow valve 14 used in the present embodiment is an overflow that opens when a difference between the front and rear pressures, that is, the pressure in the low-pressure fuel passage 18a and the pressure in the fuel leak passage 30a exceeds a predetermined value. A valve is used. Therefore, in a state where the low-pressure fuel is being pumped by the low-pressure pump 2, the pressure in the low-pressure fuel flow path 18a is maintained so as to be larger than the pressure in the fuel leak path 30a by a predetermined differential pressure.

  The high-pressure pump 5 is pumped by the low-pressure pump 2 and pressurizes the low-pressure fuel introduced into the pressurizing chamber 5a via the fuel intake valve 6 by the plunger 7, and the common rail 10 via the fuel discharge valve 9 and the high-pressure fuel passage 37a. High pressure fuel is pumped to The high-pressure pump 5 is driven by a cam 15 fixed to a camshaft connected to a drive shaft of an internal combustion engine via a gear. Further, in the high pressure pump 5 of the pressure accumulating fuel injection device 50 shown in FIG. 1, the two plungers 7 are pushed up by the cams 15, and the low pressure fuel is pressurized in the two pressurizing chambers 5a. High-pressure fuel is pumped from 5 a toward the common rail 10.

  The common rail 10 accumulates high-pressure fuel pumped from the high-pressure pump 5 and supplies high-pressure fuel to the plurality of fuel injection valves 13 via the high-pressure fuel passage 37b. A pressure sensor 21 and a pressure control valve 12 are attached to the common rail 10. Among these, the sensor value of the pressure sensor 21 is transmitted to the control device 40 and used for rail pressure control by the pressure control valve 12 provided in the common rail 10 or the flow rate control valve 8 provided in the high-pressure pump 5.

  As the pressure control valve 12, for example, an electromagnetic proportional control valve whose passage area can be adjusted by controlling the energization amount is used. For example, immediately after the internal combustion engine is started, the opening of the pressure control valve 12 is adjusted according to the required rail pressure, the required injection amount of the internal combustion engine, and the like, and the high pressure discharged from the common rail 10 to the fuel leak passage 30b. The amount of fuel leakage is adjusted. On the other hand, in the normal operation state of the engine, the pressure control valve 12 is basically closed, and the rail pressure is larger than the target pressure by a predetermined value (hereinafter referred to as “valve opening threshold”) or more. Sometimes the pressure control valve 12 is opened.

  The fuel injection valve 13 connected to the common rail 10 injects high-pressure fuel by controlling the opening / closing timing of the injection hole by energization control in a state where high-pressure fuel is supplied. 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.

2. Control device (common rail pressure control device)
FIG. 2 is a functional block diagram showing a portion related to rail pressure control in the configuration of the control device 40 that controls the accumulator fuel injection device 50 of the present embodiment.
The control device 40 is configured around a microcomputer having a known configuration, and includes a rail pressure detection unit 71, a target pressure calculation unit 72, a control means selection unit 73, a flow rate control unit 74, and a high-pressure discharge. A control unit 75 and a valve opening number limiting unit 76 are provided. Specifically, each of these units is realized by executing a program by a microcomputer. In addition, the control device 40 includes a RAM (Random Access Memory) (not shown), and stores calculation results and detection results at each unit.

  The rail pressure detector 71 reads the sensor value S1 of the pressure sensor 21 provided on the common rail 10 at regular time intervals and calculates the rail pressure Pr based on the sensor value S1. The target pressure calculation unit 72 calculates the target pressure Ptgt of the common rail based on the accelerator operation amount Acc, the internal combustion engine speed Ne, the fuel injection amount instruction value Qf, and the like. The calculated rail pressure Pr and target pressure Ptgt are transmitted to the flow rate control unit 74 and the high pressure discharge control unit 75 and used for rail pressure control. In the present embodiment, the calculated rail pressure Pr is also transmitted to the valve opening number limiting unit 76.

  The control means selector 73 determines whether to use the flow control valve 8 or the pressure control valve 12 to perform the feedback control of the rail pressure Pr using the rail pressure Pr and the target pressure Ptgt. In the feedback control of the rail pressure Pr using the flow control valve 8, the rail pressure Pr is adjusted by adjusting the supply amount of high-pressure fuel to the common rail 10, whereas the rail using the pressure control valve 12 is controlled. In the feedback control of the pressure Pr, the rail pressure Pr is adjusted by adjusting the discharge amount of the high-pressure fuel from the common rail 10.

  In the example of the pressure accumulation type fuel injection device 50 of the present embodiment, when the temperature Tf detected by the temperature sensor provided in the high pressure fuel system does not reach the predetermined value, the rail pressure control using the pressure control valve 12 is performed. Otherwise, rail pressure control using the flow control valve 8 is selected. That is, rail pressure control using the pressure control valve 12 is selected in situations where it is desired to quickly increase the temperature of the high-pressure fuel system, such as immediately after the start of the internal combustion engine, and rail pressure control using the flow control valve 8 during normal operation. Control is selected. The control means selection unit 73 transmits the selection result to the flow rate control unit 74 and the high pressure discharge control unit 75.

  The flow rate control unit 74 mainly uses the rail pressure Pr and the target pressure Ptgt transmitted from the rail pressure detection unit 71 and the target pressure calculation unit 72 in the normal operation state of the internal combustion engine. Is adjusted to control the rail pressure Pr by adjusting the flow rate of the low-pressure fuel. On the other hand, the flow rate control unit 74 performs control so that the flow rate control valve 8 is maintained at a predetermined opening degree when the internal combustion engine is started.

  More specifically, since the rail pressure feedback control is performed by the pressure control valve 12 at the time of starting the internal combustion engine, etc., the high pressure fuel exceeding the maximum fuel injection amount assumed in all operating states is common rail 10. The opening degree of the flow control valve 8 is set so as to be supplied.

  Further, in the normal operation state of the internal combustion engine, the flow control unit 74 determines the movement amount of the piston of the flow control valve 8 according to the deviation ΔP between the rail pressure Pr and the target pressure Ptgt, and the actuator of the flow control valve 8 A control signal S2 is output to (not shown). As a result, the supply amount of the low pressure fuel to the high pressure pump 5 is adjusted, and the flow rate of the high pressure fuel supplied to the common rail 10 is changed.

  The high pressure discharge control unit 75 mainly opens the pressure control valve 12 using the rail pressure Pr and the target pressure Ptgt transmitted from the rail pressure detection unit 71 and the target pressure calculation unit 72 at the time of starting the internal combustion engine. The rail pressure Pr is feedback controlled by adjusting the degree. On the other hand, the high-pressure exhaust control unit 75 basically performs control to fully close the pressure control valve 12 in the normal operation state of the internal combustion engine. In order to increase the opening degree of the pressure control valve 12, the set value Ppcv of the target pressure is relatively increased, and in order to decrease the opening degree, the set value Ppcv of the target pressure is relatively decreased.

  Specifically, at the time of starting the internal combustion engine or the like, the high pressure discharge control unit 75 determines the amount of movement of the piston of the pressure control valve 12 according to the deviation ΔP between the rail pressure Pr and the target pressure Ptgt, and pressure control A control signal S3 is output to an actuator (not shown) of the valve 12. As a result, the flow rate of the high pressure fuel discharged from the common rail 10 is changed.

  Further, in the normal operation state of the internal combustion engine, the high pressure discharge control unit 75 basically closes the pressure control valve 12 completely, but the rail pressure Pr becomes greater than the target pressure Ptgt by a predetermined valve opening threshold ΔP0 or more. Sometimes the control signal S3 for opening the valve is output to the pressure control valve 12. As a result, part of the high-pressure fuel is discharged from the common rail 10 in accordance with the opening degree or valve opening time of the pressure control valve 12, and the rail pressure Pr is reduced. However, as will be described later, when the fuel injection cut control is performed, the number Nv of opening of the pressure control valve 12 is limited. Therefore, the rail pressure Pr exceeds the target pressure Ptgt several times after the fuel injection cut control. Even in such a case, the number of outputs of the control signal S3 for instructing opening of the pressure control valve 12 is limited to the set number of opening times Nv0.

  When the valve opening number limiting unit 76 receives a signal S4 indicating that a fuel injection cut control execution instruction for temporarily reducing the fuel injection amount by the fuel injection valve 13 is transmitted to a fuel injection control unit (not shown). Then, the instruction signal S5 is transmitted to the high pressure discharge control unit 75 so as to limit the number of opening times Nv of the pressure control valve 12.

  The valve opening number limiting unit 76 of the control device 40 of the present embodiment is the pressure control valve 12 only when the rail pressure Pr transmitted from the rail pressure detection unit 71 during rail pressure fuel injection cut control is equal to or greater than a predetermined threshold value P0. Is set so as to limit the number of opening times Nv. This is because the hunting phenomenon is prevented only when the rail pressure Pr is estimated to exceed the allowable pressure of the high-pressure fuel system when the rail pressure Pr hunting phenomenon occurs. When Pr hunting occurs, the rail pressure Pr is set to a value estimated to exceed the allowable pressure of the high-pressure fuel system.

In the accumulator fuel device 50 of the present embodiment, the instruction value Qf of the fuel injection amount is temporarily reduced in response to a torque reduction request at the time of gear shift of the internal combustion engine. The valve opening number limiting unit 76 of the present embodiment is a high pressure so that the pressure control valve 12 is opened only once when the fuel injection cut control is executed and the rail pressure Pr is equal to or higher than the threshold value P0. An instruction signal S5 is transmitted to the discharge controller 75. At the same time, the valve opening number limiting unit 76 is configured to set an opening when the valve is opened only once and to instruct the high pressure discharge control unit 75.
However, the number of opening times Nv0 may be set twice or more, but in order to reduce the damage of the high-pressure fuel system due to the increase / decrease in the rail pressure Pr, it should be set to at most three times. It is preferable.

  The opening degree that is set when the valve is opened is calculated based on, for example, the stroke position of the plunger that pressurizes the fuel with the high-pressure pump 5 when the fuel injection cut control is executed, or the amount of decrease in the fuel injection amount. These elements for determining the opening degree, that is, the time until the flow rate of the high-pressure fuel actually supplied to the common rail 10 decreases after the instruction from the flow rate control unit 74 to the flow rate control valve 8 is output. It has an influence and is not limited to the example described above. The processing capability of the control device 40 can also be an element.

  Based on these factors, the longer the time from when the instruction to the flow control valve 8 is output from the flow control unit 74 until the flow of the high-pressure fuel actually supplied to the common rail 10 decreases, the longer the pressure The opening degree of the control valve 12, that is, the set value Ppcv of the target value of the rail pressure used for the control instruction to the pressure control valve 12 is increased.

3. Timing Chart FIG. 3 shows the fuel injection amount instruction value Qf, the pressure control valve 12 set value Ppcv, when the control device 40 of the present embodiment performs control to limit the number of opening times Nv of the pressure control valve 12. 6 is a timing chart showing changes in an instruction flow rate Vmeun to the flow control valve 8 and a rail pressure Pr.
During the period from t0 to t1 when the torque reduction request is OFF, the set value Ppcv of the pressure control valve 12 is set to P1, which is higher than the target value Ptgt of the rail pressure. In this state, the pressure control valve 12 is closed. Also, during the period from t0 to t1, the fuel injection amount instruction value Qf changes smoothly, and the instruction flow rate Vmeun to the flow control valve 8 changes gently according to the change of the fuel injection amount instruction value Qf. To do. For this reason, the rail pressure Pr is maintained while being kept substantially at the rail pressure target value Ptgt. This rail pressure target value Ptgt is larger than the threshold value P0, and the rail pressure Pr is also equal to or higher than the threshold value P0.

  Here, when the torque reduction request is turned on at time t1 to shift the gear by the automatic transmission, the command value Qf of the fuel injection amount and the command flow rate Vmeun to the flow control valve 8 are temporarily reduced. At this time, the amount of high-pressure fuel discharged from the common rail 10 rapidly decreases due to a decrease in high-pressure fuel injected from the fuel injection valve 13, while a decrease to the flow control valve 8 provided on the inlet side of the high-pressure pump 5. There will be a time difference between the output timing of the instruction and the timing until the flow rate of the high-pressure fuel actually pumped to the common rail 10 decreases.

  Therefore, the rail pressure Pr starts to increase for a while after the time t1. As a result, the set value Ppcv of the pressure control valve 12 is reduced to the rail pressure target value Ptgt at the time t2 when the deviation ΔP between the rail pressure Pr and the rail pressure target value Ptgt becomes greater than the valve opening threshold ΔP0. The rail pressure Pr starts to decrease.

  Thereafter, at time t3, when the deviation ΔP between the rail pressure Pr and the target value Ptgt of the rail pressure becomes less than the valve opening threshold ΔP0 and the set value Ppcv of the pressure control valve 12 begins to gradually return to P1, this time the flow rate The command flow rate Vmeun to the control valve 8 is increased. Further, the rail pressure Pr decreases and once falls below the target value Ptgt of the rail pressure, but at the time t4, the rail pressure Pr starts increasing again following the increase in the instruction flow rate Vmeun to the flow control valve 8. Thereafter, at time t5, the gear shift by the automatic transmission is completed and the decrease in the fuel injection amount command value Qf is released, so that the rise of the rail pressure Pr is temporarily stopped, but the command flow rate Vmeun to the flow control valve 8 is stopped. Following the increase, the rail pressure Pr rises again.

  Then, the torque reduction request is turned off at time t6, the rail pressure Pr exceeds the rail pressure target value Ptgt at time t7, and the difference ΔP between the rail pressure Pr and the rail pressure target value Ptgt at time t8. Is equal to or greater than the valve opening threshold value ΔP0, but the set value Ppcv of the pressure control valve 12 is reduced because the number of opening times Nv0 of the pressure control valve 12 when the fuel injection cut control is executed is limited to one. There is nothing. However, the command value Qf of the fuel injection amount after the torque reduction request is turned off gradually changes, and the command flow rate Vmeun of the flow control valve is adjusted accordingly. The hunting phenomenon does not occur, and the rail pressure Pr is substantially maintained at the target value Ptgt of the rail pressure.

4). Rail Pressure Control Method Next, a rail pressure control method performed by the control device 40 of the present embodiment shown in FIG. 2 will be described based on the control flow of FIG. 4.
In this control flow example, first, in step S1, it is determined which of the flow control valve 8 or the pressure control valve 12 is used to perform the rail pressure control. In the example of this embodiment, the fuel temperature Tf calculated based on the sensor value of the fuel temperature sensor provided in any part of the accumulator fuel injection device 50 is compared with a predetermined threshold value Tf0, and the fuel temperature Tf is When the fuel temperature Tf is lower than the threshold value Tf0, rail pressure control is performed using the pressure control valve 12 in order to quickly increase the fuel temperature Tf. On the other hand, when the fuel temperature Tf is equal to or higher than the threshold value Tf0, the flow control valve 8 is used. Rail pressure control is performed. However, the selection method of the control means is not limited to the above example.

  When the control means is selected, it is determined in step S2 whether or not the rail pressure control mode is based on the flow rate control valve 8. If the rail pressure control mode is based on the flow rate control valve 8, the process proceeds to step S3. On the other hand, in the case of the rail pressure control mode by the pressure control valve 12, the process proceeds to step S17. After the rail pressure Pr is detected based on the sensor value of the pressure sensor 21 provided on the common rail 10, the target of the common rail 10 is detected in step S18. The pressure Ptgt is calculated, and in step S19, the control signal S3 of the pressure control valve 12 is output based on the deviation ΔP between the target pressure Ptgt and the rail pressure Pr, and this routine ends.

  In step S3, in which the rail pressure control mode by the flow control valve 8 is selected and advanced, the rail pressure Pr is detected based on the sensor value of the pressure sensor 21 provided on the common rail 10, and the target of the common rail 10 is further detected in step S4. Calculate the pressure Ptgt. Next, in step S5, it is determined whether or not the rail pressure Pr is equal to or greater than a predetermined threshold value P0. If the rail pressure Pr is less than the threshold value P0, the process proceeds to step S16, while the rail pressure Pr is equal to or greater than the threshold value P0. If so, the process proceeds to step S6.

  In step S6, a deviation ΔP between the target pressure Ptgt and the rail pressure Pr is obtained, and then in step S7, it is determined whether or not the obtained deviation ΔP is greater than or equal to the valve opening threshold value ΔP0. If the deviation ΔP is less than the valve opening threshold ΔP0, the process proceeds to step S16 as it is, whereas if the deviation ΔP is greater than or equal to the valve opening threshold ΔP0, the process proceeds to step S8.

  In step S8, it is determined whether the torque reduction request is on. If the torque reduction request is off, the process proceeds directly to step S12. If the torque reduction request is on, the process proceeds to step S9, and whether or not the number Nv of opening of the pressure control valve 12 stored in the RAM is 0 is determined. Determined. If the valve opening number Nv is not zero, the process proceeds to step S11 as it is. On the other hand, if the valve opening number Nv is zero, an instruction signal S5 for limiting the valve opening number Nv of the pressure control valve 12 is output in step S10. Proceed to step S11.

  In step S11, it is determined whether or not the number of opening times Nv of the pressure control valve 12 stored in the RAM is less than a set value Nv0. When the valve opening number Nv is equal to or greater than the set value Nv0, the process proceeds to step S16 as it is, while when the valve opening number Nv is less than the set value Nv0, the process proceeds to step S12 and the opening degree of the pressure control valve 12 is determined. Then, the process proceeds to step S13, and after the control signal S3 for instructing opening of the valve is output to the pressure control valve 12, the process proceeds to step S14.

  In step S14, it is determined whether or not the torque reduction request is off. If the torque reduction request is on, the process proceeds directly to step S16. If the torque reduction request is off, the opening stored in the RAM in step S15. After resetting the valve number Nv, the process proceeds to step S16. In step S16, the control signal S2 of the flow control valve 8 is output based on the deviation ΔP obtained in step S6, and this routine is terminated.

  According to the rail pressure control method performed as described above, the torque reduction request is independent of the accelerator operation amount while the rail pressure control is being performed by adjusting the flow rate of the low-pressure fuel by the flow rate control valve 8. When the fluctuation of the rail pressure due to the above occurs, the rail pressure is repeatedly increased and decreased to prevent the rail pressure hunting phenomenon from occurring. In particular, by preventing the rail pressure hunting phenomenon, the number of overshoots in which the rail pressure exceeds the allowable pressure of the high-pressure fuel system is reduced, so that the possibility of damage to the high-pressure fuel system is also reduced.

  In addition, since the rail pressure hunting phenomenon is controlled by limiting the number of times the pressure control valve is opened, the rail pressure hunting phenomenon can be reliably ensured even if there are variations in processing accuracy during manufacturing of the pressure control valve. Is prevented.

Claims (7)

The low pressure fuel in the fuel tank is pumped by a low pressure pump, and the high pressure pump is pressurized by a high pressure pump to pump the high pressure fuel to a common rail connected to a plurality of fuel injection valves. In a common rail pressure control device for controlling the pressure in the common rail in an accumulator fuel injection device that injects the high pressure fuel into
While the flow rate of the low-pressure fuel pumped to the high-pressure pump is adjusted according to the target pressure of the common rail, when the pressure in the common rail becomes greater than the target pressure by a predetermined value or more, the The pressure control valve for discharging the high-pressure fuel is opened once to control the difference between the pressure in the common rail and the target pressure to be less than the predetermined value,
Control for opening the pressure control valve once when the pressure in the common rail becomes larger than the target pressure by a control in which the fuel injection amount from the fuel injection valve is temporarily reduced. A control device for common rail pressure, wherein the number of times is limited.   The number of times of control for opening the pressure control valve once is limited to one time, and the opening at the time of the one valve opening is the high pressure when the fuel injection amount is temporarily reduced. 2. The common rail pressure control device according to claim 1, wherein the common rail pressure control device is set according to at least one of a position of a plunger of a pump or a decrease amount of the fuel injection amount.   Limiting the number of times of control for opening the pressure control valve once is performed when the pressure in the common rail when the fuel injection amount is temporarily reduced is equal to or higher than a predetermined threshold value. The control apparatus of the common rail pressure of Claim 1 or 2.   The control in which the fuel injection amount is temporarily reduced is control performed to reduce the torque of an automatic transmission at the time of gear shifting of a vehicle in which the internal combustion engine is mounted. The common rail pressure control device according to any one of claims 3 to 4. The control device for the common rail pressure is:
A rail pressure detector for detecting the pressure in the common rail;
A flow rate controller that adjusts the flow rate of the low-pressure fuel supplied to the high-pressure pump in accordance with the target pressure;
Control that makes the difference between the pressure in the common rail and the target pressure less than the predetermined value by opening the pressure control valve once when the pressure in the common rail becomes larger than the target pressure by a predetermined value or more. A high pressure discharge control unit that performs
A valve opening number limiting unit that limits the number of times the control is performed to open the pressure control valve once by the high-pressure discharge control unit during execution of control in which the fuel injection amount from the fuel injection valve is temporarily reduced;
The common rail pressure control device according to claim 1, further comprising: The low pressure fuel in the fuel tank is pumped by a low pressure pump, and the high pressure pump is pressurized by a high pressure pump to pump the high pressure fuel to a common rail connected to a plurality of fuel injection valves. In the control method of the common rail pressure for controlling the pressure in the common rail in the accumulator fuel injection device that injects the high pressure fuel into the inside,
While the flow rate of the low-pressure fuel pumped to the high-pressure pump is adjusted in accordance with the target pressure of the common rail, when the pressure in the common rail becomes greater than the target pressure by a predetermined value or more, the The pressure in the common rail is reduced by controlling the difference between the pressure in the common rail and the target pressure to be less than the predetermined value by opening a pressure control valve for discharging high-pressure fuel once.
The number of times of control for opening the pressure control valve once when the pressure in the common rail becomes larger than the target pressure by a control in which the fuel injection amount from the fuel injection valve is temporarily reduced. The control method of the common rail pressure characterized by restricting. The low pressure fuel in the fuel tank is pumped by a low pressure pump, and the high pressure pump is pressurized by a high pressure pump to pump the high pressure fuel to a common rail connected to a plurality of fuel injection valves. In the accumulator fuel injection device for injecting the high-pressure fuel into the inside,
A flow rate control valve for controlling the flow rate of the low pressure fuel pumped to the high pressure pump;
A pressure control valve provided on the common rail for discharging the high-pressure fuel in the common rail;
When the pressure in the common rail can be controlled by controlling the flow control valve according to the target pressure of the common rail, and the pressure in the common rail becomes larger than the target pressure by a predetermined value or more during this control. A rail pressure control device that controls the difference between the pressure in the common rail and the target pressure to be less than the predetermined value by opening the pressure control valve once, and
The rail pressure control device controls the pressure control valve when the pressure in the common rail becomes larger than the target pressure by a control in which the fuel injection amount from the fuel injection valve is temporarily reduced. accumulator fuel injection apparatus characterized by limiting the number of times of control for rotating the valve opening.

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