JP2011052539A - Fuel injection device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such problems that abnormal fuel pressure results from impossibility to fully discharge fuel in a common rail and that excess fuel pressure drop and not intended engine stall result from excessive fuel discharge the other way around if an electric control relief valve and a mechanical relief valve are not cooperatively controlled well when a method compensating flow rate shortage by the mechanical relief valve is employed in a structure in which flow rate of the electric control relief valve is short with respect to whole delivery flow rate of a high pressure fuel pump. <P>SOLUTION: In a high pressure fuel system including the mechanical relief valve and the electric control relief valve, operation of the electric control relief valve is started after pressure reaches the value at which the mechanical relief valve starts operation or higher so as to make the mechanical relief valve sufficiently operate at full delivery of the high pressure fuel pump. Discharge is done by using both of the mechanical relief valve and the electric control relief valve thereby. Flow rate of the electric control relief valve is controlled based on pressure characteristics of a case that only the mechanical relief valve is operated in full delivery of the high pressure fuel pump during operation of the electric control relief valve. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel supply apparatus having a configuration in which an electrically controlled relief valve (for example, an electrically controlled pressure regulator) for controlling a fuel pressure in a piping system for stocking fuel of an internal combustion engine is disposed.

  A low-pressure pump is connected from the fuel tank via a low-pressure pipe (feed pipe). The fuel boosted by this low-pressure pump is further boosted by the high-pressure fuel pump and introduced into the livestock pressure pipe (hereinafter referred to as common rail). There is known an internal combustion engine (hereinafter referred to as an engine) that injects a cylinder from a connected injection device (hereinafter referred to as an injector).

  Such an engine is provided with a mechanical relief valve (A) that starts operation at a predetermined pressure and returns the fuel in the common rail to the feed pipe in case the fuel pressure of the common rail becomes abnormally high. Is common.

  Here, the relief characteristic of the mechanical relief valve (a) is set so as to prevent the mechanical relief valve (a) from malfunctioning due to the fuel pressure pulsation of the high-pressure fuel pump. If the mechanical relief valve (A) needs to be versatile because it is integrated with the mechanical relief valve (A), the high-pressure fuel pump fails and the full discharge state continues. In this case, the discharge of the entire discharge flow rate is not in time, the fuel pressure increases, and an abnormally high fuel pressure exceeding the allowable maximum fuel pressure can be obtained. Here, the allowable maximum fuel pressure is due to the operating limit pressure of the injector, the fuel gallery (pipe) pressure resistance, or the like. For the purpose of explaining the above-described contents, FIG. 1 shows a fuel pressure-engine rotation speed chart at the time of full discharge of the high-pressure fuel pump when a high-pressure fuel pump utilizing the rotational motion of the engine is adopted.

  In the situation of the abnormally high fuel pressure as described above, the fuel in the common rail must be discharged and the fuel pressure must be reduced by means other than the mechanical relief valve (A).

  Also, when the engine is stopped, if the fuel pressure in the common rail is equal to or higher than the pressure that compensates for the oil tightness of the injector, the oil tightness will not be maintained and the fuel in the common rail will flow into the cylinder through the injector. There is a risk that exhaust performance will deteriorate.

  Further, in the accelerator operation for controlling the fuel injection amount or the intake air amount of the engine, the fuel cut is performed when the accelerator is turned off, but the accelerator is turned on to return from the fuel cut state (so-called fuel consumption). From the viewpoint of exhaust performance, it is desirable that the fuel pressure is optimally controlled in accordance with the engine operating state such as the accelerator operation amount and the rotational speed at the time of return.

  As a configuration that can be used to eliminate the abnormally high fuel pressure and to optimize fuel pressure such as fuel cut recovery, it is an electric control relief valve (hereinafter referred to as “electric control relief valve”) that is separate from the mechanical relief valve (A). The structure provided with the control relief valve (b) is proposed in the following document 1.

JP-A-10-54318

  In the configuration described in Document 1, when the flow rate of the electric control relief valve (b) exceeds the total discharge amount of the high-pressure fuel pump, even if the high-pressure fuel pump fails to discharge completely, the mechanical relief valve (b) It is possible to reduce the pressure of the fuel in the common rail to a desired fuel pressure with only the electric control relief valve (B) while not operating.

  However, for example, when parts are shared and the injector is diverted as an electric control relief valve (b), the flow rate of the injector basically has a relationship of “total discharge amount of high-pressure fuel pump> flow rate per injector”. Therefore, the injector cannot be used as it is, and it is necessary to change the base injector, and there is a concern that the sharing advantage as expected cannot be obtained.

  In view of this, it is conceivable to compensate for the insufficient flow rate of the electric control relief valve (b) with a mechanical relief valve (b) or a mechanical relief valve (c) provided separately.

  However, if the electrical control relief valve (b) and the mechanical relief valve (b) (c) do not cooperate well, the fuel in the common rail cannot be discharged, resulting in abnormal fuel pressure, or conversely, too much fuel is discharged. As a result, the fuel pressure may drop too much, leading to an unintended engine stop (so-called engine stall).

  In a high-pressure fuel system equipped with a mechanical relief valve (b) and an electric control relief (b), the mechanical relief valve (a) is fully activated during full discharge of the high-pressure fuel pump. Discharge using both the mechanical relief valve (b) and the electric control relief valve (b) by starting the operation of the electric control relief valve (b) after (b) exceeds the starting pressure. To do.

  During operation of the electric control relief valve, by controlling the flow rate of the electric control relief valve (b) based on the pressure characteristics when only the mechanical relief valve is operated during full discharge of the high-pressure fuel pump, abnormally high fuel pressure, It is possible to prevent the fuel pressure from excessively decreasing and to quickly control the fuel pressure near the target fuel pressure.

  It is possible to share parts, and as a result, it is possible to provide a component structure with low system cost.

It is a pressure characteristic figure at the time of combining a high pressure fuel pump and a mechanical relief valve, and fully discharging a high pressure fuel pump. It is a 1st block diagram of the fuel supply apparatus by embodiment of this invention. It is a 2nd block diagram of the fuel supply apparatus by embodiment of this invention. It is a flowchart which shows the main routine of the fuel pressure control by embodiment of this invention. It is a flowchart which shows the subroutine of the fuel pressure control by embodiment of this invention. It is a flowchart which shows the subroutine of the fuel pressure control by embodiment of this invention. It is a chart which shows the table constant tb1 setting value referred in the subroutine of fuel pressure control by embodiment of this invention. It is a flowchart which shows the subroutine of the fuel pressure control by embodiment of this invention. It is a chart which shows the table constant tb2 setting value referred in the subroutine of fuel pressure control by embodiment of this invention. It is a flowchart which shows the subroutine of the fuel pressure control by embodiment of this invention. It is a time chart showing the operation state of the fuel pressure behavior in the common rail and the mechanical relief valve and the electric control relief valve according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

A first embodiment of the present invention will be described. FIG. 2 is a system configuration diagram in which the fuel supply device of the present invention is applied to a direct injection gasoline engine fuel supply device.
The fuel in the fuel tank 100 is pumped up from the low-pressure fuel pump 101 and supplied to the high-pressure fuel pump 103 via the low-pressure pipe 102 via the fuel filter (not shown). The pressure of the fuel supplied to the high-pressure fuel pump 103 is regulated to 0.3 to 0.5 Mpa by a low-pressure pressure regulator (not shown). The fuel supplied to the high-pressure fuel pump 103 is boosted to about 3 Mpa to 20 Mpa and accumulated in the common rail 105.

  The fuel accumulated in the common rail is supplied and burned by an injector 106 installed in each cylinder of the engine. The pressure of the fuel accumulated in the common rail is detected by the fuel pressure sensor 104, and a fuel pressure sensor signal is sent to the ECU 110. The common rail is further provided with an electrically controlled relief valve 107 that adjusts the fuel pressure, and opens or closes the valve based on a control signal from the ECU 110. When the valve is opened, the fuel in the common rail is relieved at low pressure. The fuel is discharged into the pipe 108 and the fuel pressure in the common rail is reduced. A plurality of relief valves 107 may be provided.

  Furthermore, a mechanical relief valve (hereinafter, mechanical relief valve) (not shown) for automatically adjusting the fuel pressure in the common rail is installed. When the mechanical relief valve is opened, the fuel in the common rail is discharged to the same low pressure relief pipe as in the case of the electrically controlled relief valve 107, and the fuel pressure in the common rail is reduced. The mechanical relief valve may be built in the high-pressure fuel pump 103 or may be installed on a common rail. Further, a plurality of mechanical relief valves may be provided.

  The fuel discharged by the relief valve 107 and the mechanical relief valve is supplied again to the high-pressure fuel pump via the low-pressure pipe 102 and is supplied to the common rail by the high-pressure fuel pump. In addition to the fuel pressure sensor signal, ECU 110 takes in engine state signals such as engine speed, engine intake air amount, accelerator position signal, and engine water temperature, and calculates the fuel injection amount and target fuel pressure.

  FIG. 3 is a system configuration diagram showing the second embodiment. 2 is different from the first system configuration in that the fuel discharged by the relief valve 107 is returned to the fuel tank. The first system configuration in FIG. 2 is advantageous over the second system configuration in that it is not necessary to install a return pipe for returning the fuel discharged from the relief valve to the fuel tank.

  Next, the control flow of the fuel pressure control of the fuel supply apparatus according to the present invention will be described with reference to FIGS.

FIG. 4 is a main flow of fuel pressure control. In step 401, an engine state signal such as an engine speed (NE), an engine intake air amount, an accelerator position signal, an engine water temperature, and a fuel pressure is taken in, and the process proceeds to step 402.
In step 402, the fuel injection amount supplied to each cylinder of the engine is calculated from the engine state taken in in step 401, and the process proceeds to step 403.
If it is not determined in step 403 that the abnormal fuel pressure will be described later, the target pressure of the accumulated pressure fuel in the common rail is calculated from the engine state taken in in step 402, and the process proceeds to step 404. If it is determined that the fuel pressure is abnormal, the target fuel pressure is calculated based on not only the engine state but also the operating state of the high-pressure pump, and the process proceeds to step 404.
Here, the target fuel pressure is common to the high pressure fuel pump and the electric control relief valve, but different target fuel pressures may be calculated.

  In step 404, a high-pressure pump control amount for controlling the fuel pressure in the common rail through the high-pressure pipe is calculated by the high-pressure fuel pump in accordance with the fuel pressure calculated in step 403, and the process proceeds to step 405.

  In step 405, the abnormal fuel pressure is determined from the actual fuel pressure. If it is determined that the fuel pressure is abnormal, the process proceeds to step 405. If it is not determined that the fuel pressure is abnormal, the fuel pressure control is terminated. Here, the abnormal fuel pressure is determined from the actual fuel pressure, but may be determined based on the rate of change of the actual fuel pressure, based on the determination result of the high-pressure fuel pump failure diagnosis, or any other method may be used. However, it is desirable that a fuel pressure abnormality can be detected quickly.

FIG. 5 shows a detailed flow of electric control relief valve control at the time of abnormal fuel pressure determination shown in step 406 of FIG.
In step 505, the actual fuel pressure is compared with the operation start determination fuel pressure (rp_erac0), and if the actual fuel pressure is larger, the process proceeds to step 508. If the actual fuel pressure is smaller, the process proceeds to step 506.
In step 506, after experiencing “actual fuel pressure> operation start determination fuel pressure (rp_erac0)”, it is determined whether or not “actual fuel pressure <operation determination fuel pressure (rp_erac1)” is experienced. If not established, the process is terminated.
In step 507, the actual fuel pressure is compared with the operation determination fuel pressure (rp_erac2). If the actual fuel pressure is larger, the process proceeds to step 508. If the actual fuel pressure is smaller, the process ends.
In step 508, electric control relief valve control is executed.

FIG. 6 shows a detailed flow of electric control relief valve control shown in step 506 of FIG.
In step 601, the effective pulse width for the feedforward is calculated, and the process proceeds to step 602.
In step 602, the effective pulse width for the feedback is calculated, and the process proceeds to step 603.
In step 603, the effective pulse width is calculated based on the calculation results of step 602 and step 603, and the process proceeds to step 604.
In step 604, an invalid pulse width is obtained based on the actual fuel pressure, and the process proceeds to step 605. Although the ineffective pulse width is obtained based on the actual fuel pressure here, it may be obtained based on the voltage or the like, or may be obtained by other methods.
In step 605, the final pulse width is calculated based on the calculation results of steps 603 and 604, and the process ends.

  FIG. 7 shows a table setting example used for invalid pulse calculation shown in step 604 of FIG. The set value is desirably set based on the unit test result of the electric control relief. Although FIG. 7 shows an injector-based electrical control relief, it is raised to the right, but it may also be a characteristic that is lowered to the right or other characteristics.

FIG. 8 shows a detailed flow of the feedforward effective pulse width calculation shown in step 601 of FIG.
In step 801, the maximum fuel pressure when the mechanical relief valve is operated is calculated from the engine speed, and the flow proceeds to step 802.
In step 802, the target pressure reduction amount for the electric control relief is calculated, and the process proceeds to step 803.
In step 803, the target flow rate for the electric control relief is calculated, and the process proceeds to step 804. Here, the target pressure reduction amount (TDPFF_ERV) for the electric control relief and the common rail volume (v
ol_cmn) and elastic modulus (coe_ela), but other methods may be used.
In step 804, the feed-forward pulse width is calculated and the process ends.
In addition, although it was set as the structure calculated from the target flow volume (TFFF_ERV) for electric control relief, flow volume-pulse width conversion coefficient (coe_erpw), and adjustment coefficient (coe_adj) here, the other method may be used.

  FIG. 9 shows table setting values for obtaining the maximum fuel pressure when the mechanical relief valve is operated, which is shown in Step 801 of FIG. In addition, although the fuel pressure at the time of full discharge of the high-pressure fuel pump when the one using the rotational motion of the engine as the high-pressure fuel pump is adopted is shown here, it matches the type of the high-pressure fuel pump. Other formats may be used.

FIG. 10 shows a detailed flow of the effective pulse width calculation for feedback shown in step 602 of FIG.
In step 1001, the fuel pressure deviation is obtained, and the process proceeds to step 1002.
In step 1002, the target flow rate for the electric control relief is obtained, and the process proceeds to step 1003. In step 1003, the feedback pulse width is obtained and the process ends.

  FIG. 11 is a time chart when the control flow described in FIGS. 4 to 10 is executed. At a certain fuel pressure, the flow rate of each of the mechanical relief valve and the electric control relief valve is less than the total discharge flow rate of the high pressure fuel pump. The fuel supply device that is combined so as to have a flow rate or higher is described assuming that the high-pressure fuel pump completely discharges immediately before time t1 under certain operating conditions.

  It should be noted that the flow rate of the mechanical relief valve is less than or equal to the full discharge of the high-pressure fuel pump if the rated flow rate of the mechanical relief valve itself is less than or equal to the high-pressure fuel pump. The general mechanical relief has a characteristic that there is a differential pressure between the pressure at which the mechanical relief starts to operate (cracking pressure) and the pressure at which the mechanical relief reaches the rated flow rate. Although the rated flow rate of the relief valve is higher than that of the high-pressure fuel pump, this also applies to the case where fuel is discharged at a pressure lower than the rated flow rate.

Immediately before time t1, the fuel pressure rises because the high-pressure fuel pump has completely discharged.
At time t1, the fuel pressure at which the abnormal fuel pressure is determined. Furthermore, the fuel pressure rises.
At time t2, the fuel pressure at which the mechanical relief valve operates is reached. When the mechanical relief operates, the rate of increase in fuel pressure slows down, but the fuel pressure rises because the flow rate of the mechanical relief valve alone cannot cover the flow rate of the entire discharge of the high-pressure pump.
At time t3, the electric control relief operation start determination pressure (rp_erac0) is reached. Since the electric control relief is activated at time t3, the fuel pressure decreases.
At time t4, the electric control relief valve becomes less than the electric control relief operation determination pressure (rp_erac1), so the electric control relief valve is closed. The fuel pressure starts to rise by closing the electric control relief valve.
At time t5, since it becomes larger than the electric control relief operation determination pressure (rp_erac2), the electric control relief valve is opened and the fuel pressure starts to decrease.
At time t6, since the electric control relief operation determination pressure (rp_erac1) becomes lower, the electric control relief valve is closed. The fuel pressure starts to rise by closing the electric control relief valve.
After time t7, the operation and behavior from time t4 to time t6 are the same.

For convenience, the description has been made so that the fuel pressure change occurs simultaneously with the start / stop of the operation of the mechanical relief valve / electrically controlled relief valve, but in reality, there is some response delay.
In FIG. 11, the valve closing pressure of the mechanical relief valve is shown lower than the valve opening pressure of the mechanical relief valve, but this represents a so-called hysteresis.
In FIG. 11, the target fuel pressure is set between the opening pressure of the mechanical relief valve and the closing pressure of the mechanical relief valve. However, if the fuel pressure is controlled within this range, the mechanical relief valve is opened. Along with the flow rate of the electric control relief valve, the flow rate discharge is higher than the total discharge of the high-pressure fuel pump and aims to stably control the fuel pressure. However, a target fuel pressure other than this value may be used.
In FIG. 11, it is assumed that the target fuel pressure is commonly used by the high-pressure fuel pump and the electric control relief valve. However, different target fuel pressures are used for the high-pressure fuel pump and the electric control relief valve. It is also good.

DESCRIPTION OF SYMBOLS 100 Fuel tank 101 Low pressure fuel pump 102 Low pressure fuel piping 103 High pressure fuel pump 104 Fuel pressure sensor 105 Common rail 106 Injector 107 Electric control relief valve 108 Relief piping 109 to low pressure piping Relief piping 110 to fuel tank 110 ECU

Claims (5)

A high-pressure pump for pumping high-pressure fuel of the internal combustion engine; a common rail for accumulating the pumped fuel; an injection valve for injecting the accumulated fuel into the cylinder; a means for detecting the pressure of the pressure-accumulated fuel; In a fuel injection control device comprising means for calculating a target value, an electrically controlled relief valve that discharges common rail pressure-accumulated fuel, and a mechanical relief valve that discharges common rail stock pressure fuel,
The maximum relief amount of the electrically controlled relief valve is smaller than the maximum discharge amount of the high-pressure pump,
2. The fuel injection device for an internal combustion engine, wherein the operation start of the electric control type relief valve is set to be equal to or higher than a pressure at which the mechanical relief valve starts to operate. A high-pressure pump for pumping high-pressure fuel of the internal combustion engine; a common rail for accumulating the pumped fuel; an injection valve for injecting the accumulated fuel into the cylinder; a means for detecting the pressure of the pressure-accumulated fuel; In a fuel injection control device comprising means for calculating a target value, an electrically controlled relief valve that discharges common rail pressure-accumulated fuel, and a mechanical relief valve that discharges common rail stock pressure fuel,
The maximum relief amount of the electrically controlled relief valve is smaller than the maximum discharge amount of the high-pressure pump,
Parameters such as target pressure reduction amount, target relief amount, pulse width, etc. for controlling the electric control type relief valve based on the pressure characteristics of the animal pressure fuel when only the mechanical relief valve is operated during full discharge of the high-pressure fuel pump The electric control type relief valve is controlled to compensate for the relief amount by the mechanical relief valve by changing the above, and to achieve the total relief amount necessary to achieve the target fuel pressure. Engine fuel injection device.   2. The fuel injection device according to claim 1, wherein a target pressure reduction amount and a target for the electric control type relief valve control based on the pressure of the livestock pressure fuel when only the mechanical relief valve is operated at the time of full discharge of the high pressure fuel pump. By changing parameters such as the relief amount and pulse width, the electrical relief valve is controlled so that the relief amount by the mechanical relief valve is supplemented and the total relief amount necessary to achieve the target fuel pressure is achieved. A fuel injection device for an internal combustion engine.   3. The fuel injection device according to claim 2, wherein the electric control type relief valve is controlled based on the pressure of the stock pressure fuel when only the mechanical relief valve is operated at the time of full discharge of the high pressure fuel pump when the high pressure fuel pump fails. By changing parameters such as the target pressure reduction amount, target relief amount, and pulse width, the electrical relief amount by the mechanical relief valve is supplemented to achieve the total relief amount necessary to achieve the target fuel pressure. A fuel injection device for an internal combustion engine, characterized by controlling a controlled relief valve.   4. The fuel injection device according to claim 3, for controlling the electrically controlled relief valve based on the pressure of the stock pressure fuel when only the mechanical relief valve is operated at the time of full discharge of the high pressure fuel pump when the high pressure fuel pump fails. By changing parameters such as the target pressure reduction amount, target relief amount, and pulse width, the electrical relief amount by the mechanical relief valve is supplemented to achieve the total relief amount necessary to achieve the target fuel pressure. A fuel injection device for an internal combustion engine, characterized by controlling a controlled relief valve.

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