JP4120624B2 - Fuel supply device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel supply device for an internal combustion engine.

  In a fuel supply device for an internal combustion engine, conventionally, a check valve is provided on the discharge port side of the fuel pump, and by maintaining a high pressure without reducing the residual fuel pressure in the fuel pipe even when the internal combustion engine is stopped, It has been attempted to improve the high temperature restartability by preventing vapor (fuel evaporative gas) from being generated in the fuel in the fuel pipe.

  However, if the fuel residual pressure in the fuel pipe is kept at a high level while the internal combustion engine is stopped, the fuel may slightly leak from the minute gap in the valve of the injector. This fuel leakage increases as the residual fuel pressure increases, and this causes an increase in the amount of unburned gas components (HC) that are being discharged when the internal combustion engine is started, thereby deteriorating emissions. Further, when the internal combustion engine is stopped, the fuel leaked from the injector evaporates, and the fuel evaporative gas emission while the internal combustion engine is stopped may be deteriorated. Conventionally, a high residual fuel pressure was set in order to ensure high-temperature restartability, so there was a case where deterioration of fuel evaporative gas emission at the start and stop of the internal combustion engine due to the fuel leakage described above may be a problem. .

  In contrast, when the temperature of the fuel when the internal combustion engine is stopped is higher than a predetermined temperature, the fuel pressure suitable for that temperature is calculated, and the relief valve is opened until the fuel pressure reaches the fuel pressure. A technique for reducing the residual pressure and suppressing fuel leakage has been proposed (see, for example, Patent Document 1).

However, in the above prior art, it is necessary to detect the residual fuel pressure in the fuel pipe, and the configuration and control are complicated. Further, since the pressure in the fuel pipe after the stop of the internal combustion engine is maintained at a positive pressure, the fuel evaporative emission may be deteriorated due to fuel leakage depending on the aging of the valve of the injector.
JP-A-9-42109 JP-A-6-280804 Japanese Utility Model Publication No. 3-112173

  An object of the present invention is to provide a technique capable of more reliably suppressing fuel leakage from an injector while the internal combustion engine is stopped with a simple configuration and control.

  In order to achieve the above object, the present invention provides a fuel pressure that is the temperature of a fuel when the pressure of the fuel (hereinafter referred to as “fuel pressure”) becomes zero when the relief valve is continuously closed after the internal combustion engine is stopped. The reference temperature is estimated from the temperature of the fuel when the internal combustion engine is stopped, and when the fuel temperature is higher than the fuel pressure reference temperature while the internal combustion engine is stopped, the relief valve is opened.

More specifically, a fuel injection valve that supplies fuel to a cylinder of the internal combustion engine,
A delivery pipe for directing fuel to the fuel injection valve;
A pressure regulator that regulates the fuel pressure of the fuel pumped from the fuel tank of the internal combustion engine to the delivery pipe to a set pressure ;
A fuel return passage for returning fuel in the delivery pipe to the fuel tank;
A relief valve that is provided in the fuel return passage and opens fuel in the delivery pipe to the fuel return passage;
An internal combustion engine fuel supply apparatus comprising:
It further comprises a fuel temperature detecting means for detecting the temperature of the fuel,
When the internal combustion engine is stopped, the relief valve continues to be closed after the internal combustion engine is stopped based on the fuel temperature detected by the fuel temperature detecting means and the set pressure of the pressure regulator. Estimate the fuel pressure reference temperature, which is the temperature of the fuel when the fuel pressure becomes zero,
The relief valve is opened when the temperature of the fuel is higher than the fuel pressure reference temperature while the internal combustion engine is stopped.

  Here, when the relief valve or injector is closed and the inside of the delivery pipe, injector, or fuel supply pipe (hereinafter referred to as “delivery pipe”) is sealed, the fuel temperature and fuel pressure It is known that there is a substantially one-to-one relationship. Further, the fuel pressure in a delivery pipe or the like during operation of the internal combustion engine is maintained at a known constant pressure by a pressure regulator. Therefore, if the temperature of the fuel in the delivery pipe or the like is detected when the internal combustion engine is stopped, then the fuel when the fuel pressure becomes zero by cooling the fuel when the delivery pipe or the like is kept in a sealed state. Can be estimated.

  Therefore, in the present invention, the temperature of the fuel inside the delivery pipe or the like when the internal combustion engine is stopped is detected by the fuel temperature detecting means, and the fuel pressure reference temperature when the fuel pressure becomes zero from the detected fuel temperature. When the internal combustion engine is stopped and the fuel temperature is higher than the fuel pressure reference temperature, the relief valve is opened. By doing so, it is possible to suppress an increase in the internal fuel pressure of the delivery pipe, etc., and because the fuel pressure in the delivery pipe etc. is high, fuel leakage occurs from the injector etc., and the fuel evaporative gas while the internal combustion engine is stopped Deterioration of emissions can be suppressed.

  According to the present invention, the fuel pressure in the delivery pipe or the like when the internal combustion engine is stopped can be maintained at substantially zero, so that the fuel evaporative gas emission while the internal combustion engine is stopped can be more reliably suppressed. In the present invention, since it is not necessary to directly detect the fuel pressure, the fuel pressure in the delivery pipe or the like can be controlled with a simple configuration and control.

  In the present invention, the relief valve may not be opened before the temperature of the fuel after the internal combustion engine is stopped first decreases to a predetermined temperature equal to or higher than the fuel pressure reference temperature.

  By doing so, the relief valve is opened in a state where the fuel pressure immediately after the stop of the internal combustion engine is high, so that the internal fuel pressure of the delivery pipe or the like can be prevented from suddenly decreasing and the occurrence of vapor can be suppressed. The restartability can be improved.

  Here, if the temperature of the fuel in the delivery pipe or the like is lower than this, the predetermined temperature is a threshold that is considered to suppress the generation of vapor even if the fuel pressure is sharply lowered by opening the relief valve. It may be the temperature of the fuel. Alternatively, the predetermined temperature and the fuel pressure reference temperature may be the same temperature.

  In the present invention, the fuel recirculation passage may be provided with a resistor having a minute flow path through which fuel in the fuel recirculation passage passes.

Then, even if the relief valve is opened in a state where the fuel pressure immediately after the stop of the internal combustion engine is high, the internal fuel pressure of the delivery pipe or the like rapidly decreases due to the resistor having the minute flow path. Can be suppressed. As a result, the generation of vapor inside the delivery pipe or the like can be suppressed, and the restartability of the internal combustion engine can be improved.

  Examples of the resistor having the minute channel include an orifice, a capillary, a porous material, and the like.

  The means for solving the problems in the present invention can be used in combination as much as possible.

  In the present invention, fuel leakage from the injector can be more reliably suppressed with a simple configuration and control while the internal combustion engine is stopped.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of a fuel supply device for an internal combustion engine according to the present embodiment. In the figure, the fuel tank 2 is filled with fuel. Further, a fuel pump 3 is disposed inside the fuel tank 2, and the fuel is pumped toward the delivery pipe 5 through the fuel supply pipe 4 by driving the fuel pump 3.

  Further, the fuel supply pipe 4 is branched into a branch pipe 6. The branch pipe 6 is provided with a pressure regulator 7. When the fuel pressure in the fuel supply pipe 4 and the delivery pipe 5 exceeds a set value, the fuel is opened to the branch pipe 6. That is, the fuel pressure in the fuel supply pipe 4 and the delivery pipe 5 is maintained at the set pressure by the pressure regulator 7. In this embodiment, this set value is about 330 KPa.

  A total of six injectors 8 are connected to the delivery pipe 5, three on each side. The injector 8 is disposed in an intake port (not shown) of the internal combustion engine 1 and opens and closes according to a fuel injection signal supplied from an engine control unit (ECU) 20 described later. Then, the fuel supplied through the fuel supply pipe 4 and the delivery pipe 5 is injected toward the combustion chamber of the internal combustion engine 1.

  Connected to the delivery pipe 5 is a fuel return pipe 9 for returning the fuel to the fuel tank 2 when the fuel pressure inside the delivery pipe 5 rises. The fuel return pipe 9 is provided with a relief valve 10 for opening or closing between the delivery pipe 5 and the fuel return pipe 9. The relief valve 10 is opened and closed by a command from the ECU 20 described later. The delivery pipe 5 is provided with a fuel temperature sensor 11 that detects the temperature of the fuel in the delivery pipe 5. The fuel recirculation pipe 9 corresponds to the fuel recirculation passage in this embodiment, and the fuel temperature sensor 11 corresponds to the fuel temperature detecting means.

  The internal combustion engine 1 configured as described above and its fuel supply device are provided with an electronic control unit (ECU) 20. This ECU 20 is a unit that controls the fuel supply device of the internal combustion engine 1 in addition to controlling the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

The ECU 20 is connected to a fuel temperature sensor 11 in the present embodiment in addition to sensors related to the control of the operating state of the internal combustion engine 1 such as a crank position sensor and an accelerator position sensor (not shown) via electric wiring. An output signal is input to the ECU 20. On the other hand, in addition to the injector 8, the relief valve 10 in this embodiment is connected to the ECU 20 via electric wiring, and is controlled by the ECU 20.

  The ECU 20 includes a CPU, a ROM, a RAM, and the like. The ROM stores a program for performing various controls of the internal combustion engine 1 and a map storing data. A relief valve control routine described later is also one of programs stored in the ROM of the ECU 20.

  Next, opening / closing control of the relief valve 10 in the present embodiment will be described. This control is for suppressing the deterioration of the fuel evaporative gas emission while the internal combustion engine 1 is stopped due to the fuel pressure in the delivery pipe 5 rising after the internal combustion engine 1 is stopped and the fuel leaking from the injector 8. Control.

  Here, during operation of the internal combustion engine 1, the internal fuel pressure of the delivery pipe 5 or the like is maintained at approximately 330 KPa by the pressure regulator 7. Therefore, immediately after the internal combustion engine 1 is stopped, the internal fuel pressure of the delivery pipe 5 and the like is approximately 330 KPa. Further, the temperature of the fuel in the delivery pipe 5 or the like is a high temperature state reflecting the operation state before the internal combustion engine 1 is stopped.

  Then, after the internal combustion engine 1 is stopped, the temperature of the fuel inside the delivery pipe 5 and the like also decreases as the temperature of the internal combustion engine 1 decreases. Then, after the internal combustion engine 1 is stopped, the relief valve 10, the injector 8, and the like are closed, so that the fuel pressure in the delivery pipe 5 decreases. And when predetermined time passes, the time of a fuel pressure becoming zero will be reached. Hereinafter, the temperature of the fuel when the fuel pressure in the delivery pipe 5 becomes zero is referred to as “fuel pressure reference temperature”.

  Thereafter, if the internal combustion engine 1 is further stopped and left to stand, the temperature of the fuel in the delivery pipe 5 or the like may increase due to an increase in the outside air temperature or the like. As a result, the fuel pressure in the delivery pipe 5 and the like increases as the temperature of the fuel increases. Thus, when the temperature of the fuel becomes higher than the fuel pressure reference temperature, the fuel pressure in the delivery pipe 5 or the like becomes a positive pressure, and if this state continues for a long time, fuel leakage from the injector 8 may occur. . As a result, the fuel evaporative gas emission may be deteriorated while the internal combustion engine 1 is stopped.

  That is, after the internal combustion engine 1 is stopped, the state where the temperature of the fuel is higher than the fuel pressure reference temperature continues, so that the fuel evaporative emission may be deteriorated while the internal combustion engine 1 is stopped.

  Therefore, in this embodiment, the temperature of the fuel in the delivery pipe 5 or the like when the internal combustion engine 1 is stopped is detected using the fuel temperature sensor 11, and the fuel pressure reference temperature is derived from the detected temperature of the fuel. When the temperature of the fuel is higher than the fuel pressure reference temperature while the internal combustion engine 1 is stopped, the relief valve 9 is opened to suppress an increase in fuel pressure in the delivery pipe 5 or the like.

  Here, FIG. 2 shows a graph showing the relationship between the fuel temperature and the fuel pressure in the delivery pipe 5 of the internal combustion engine 1 or the like.

  In FIG. 2, L1 indicates a case where the internal combustion engine 1 is stopped in an operation state with a relatively high load and a high rotational speed, that is, in a state where the temperature of the fuel is relatively high. On the other hand, L2 indicated by a broken line indicates a case where the internal combustion engine 1 is stopped in an operation state at a relatively low load and a low rotational speed, that is, in a state where the temperature of the fuel is relatively low.

  In L1, the temperature of the fuel when the internal combustion engine 1 is stopped is TS. At L2, the temperature of the fuel when the internal combustion engine 1 is stopped is TS '. However, since the fuel pressure in the delivery pipe 5 and the like is maintained by the pressure regulator 7, it is the same value P1 for both L1 and L2, and is approximately 330 KPa in this embodiment.

  Here, the fuel temperature and the fuel pressure in the delivery pipe 5 and the like are in a substantially one-to-one relationship. That is, if the fuel temperature TS when the internal combustion engine 1 is stopped is known in L1, the value of the fuel pressure reference temperature T0 when the fuel pressure becomes 0 KPa can be derived. This is because the relationship between the values of P1 (330 KPa) and TS and T0 is experimentally obtained in advance, and the value of T0 corresponding to TS, P1 (330 KPa) is read from the map storing these data. Can be derived by: Similarly, the value of T0 ′ at L2 can be derived.

  Considering L1, when the fuel temperature is higher than T0, the relief valve 10 is opened, and when the fuel temperature is T0 or less, the relief valve 10 is closed. If it does so, it can suppress that a fuel pressure raises inside the delivery pipe 5 grade | etc., And can maintain it at substantially zero.

  Next, specific control will be described with reference to FIG. FIG. 3 shows a relief valve control routine in this embodiment. This routine is a program stored in the ROM of the ECU 20 and is executed by the ECU 20 when the internal combustion engine 1 is stopped. In addition, the code | symbol in the following description uses the thing regarding the curve of L1 in FIG.

  When this routine is executed, first, in S101, a TS that is the engine stop fuel temperature is acquired. Specifically, it is acquired by taking the output of the fuel temperature sensor 11 into the ECU 20.

  Next, the process proceeds to S102. In S102, a fuel pressure reference temperature T0 is derived. Specifically, it is derived by reading out the TS acquired in S101 and the value of T0 corresponding to P1 (330 KPa) from the above-described map.

  Next, it progresses to S103 and the relief valve opening permission temperature T1 is derived | led-out. This T1 suppresses the occurrence of vapor due to a sudden drop in the internal fuel pressure of the delivery pipe 5 or the like by opening the relief valve 10 from a state in which the temperature of the fuel immediately after the stop of the internal combustion engine 1 is high. Therefore, when the temperature of the fuel is lower than this, the temperature is a threshold value that is considered to prevent vapor from being generated even when the relief valve 10 is opened.

  This T1 may also be derived by experimentally obtaining the relationship between TS and P1, mapping it in advance, and reading the values corresponding to TS and P1 from the map.

  Next, in S104, the temperature of the fuel is acquired from the output of the fuel temperature sensor 11 again. Then, the process proceeds to S105, where it is determined whether or not the fuel temperature acquired in S104 is equal to or lower than the relief valve opening permission temperature T1. And if fuel temperature is higher than T1, it will return before S104 and fuel temperature will be acquired in S104 again. The above process is repeated until it is determined in S105 that the fuel temperature is equal to or lower than T1.

After the internal combustion engine 1 is stopped, the temperature of the fuel decreases while the processes of S104 and S105 are repeated. After the internal combustion engine 1 is stopped, the relief valve 10 is maintained in the closed state until the fuel temperature first becomes equal to or lower than T1. In this way, after the internal combustion engine 1 is stopped, the relief valve 10 is opened with the fuel temperature being high, and the fuel pressure is suddenly reduced to zero, so that vapor is generated inside the delivery pipe 5 and the like. It can suppress and it can suppress that restartability deteriorates.

  If it is determined in S105 that the fuel temperature is equal to or lower than T1, that is, if the fuel temperature first becomes equal to or lower than T1 after the internal combustion engine 1 is stopped, the process proceeds to S106.

  In S106, the fuel temperature is acquired from the output of the fuel temperature sensor 11 again. Then, in S107, it is determined whether or not the fuel temperature is equal to or lower than the fuel pressure reference temperature T0. Here, when it is determined that the temperature of the fuel is equal to or lower than T0, it is determined that the fuel pressure in the delivery pipe 5 or the like is equal to or lower than zero. Therefore, the process proceeds to S108, the relief valve 9 is closed, or the closed state is Maintained.

  On the other hand, if it is determined in S107 that the fuel temperature is higher than T0, the fuel pressure in the delivery pipe 5 or the like is positive, and fuel leakage from the injector 8 or the like occurs, resulting in the stop of the internal combustion engine 1. Since it is determined that the fuel evaporative gas emission may be deteriorated, the process proceeds to S109. Then, the relief valve 10 is opened, or the open state is maintained.

  By doing so, surplus fuel can be opened from the relief valve 10 to the fuel recirculation pipe 9, and an increase in fuel pressure in the delivery pipe 5 and the like can be suppressed.

  Next, in S110, it is determined whether the ignition SW is turned on. Here, if it is determined that the ignition SW is not ON, the process returns to S106, and the above-described control for opening and closing the relief valve 10 is continued depending on whether the fuel temperature is T0 or less. On the other hand, if it is determined that the ignition SW is ON, it is determined that the internal combustion engine 1 has started, and thus the process proceeds to S111, the relief valve 10 is closed, and this routine is terminated.

  As described above, according to the relief valve control routine in the present embodiment, the fuel pressure is determined by the fuel temperature when the internal combustion engine 1 is stopped and the known fuel pressure value maintained by the action of the pressure regulator 7. The fuel pressure reference temperature T0 when the value becomes zero is derived. When the fuel temperature is higher than T0, the relief valve 10 is opened, and when the fuel temperature is equal to or lower than T0, the valve is closed. As a result, the fuel pressure can be maintained at substantially zero by a simple configuration and control in which only the temperature of the fuel is acquired, and an increase in the fuel pressure or fuel leakage from the injector 8 or the like can be suppressed. . As a result, it is possible to more reliably suppress the deterioration of the fuel evaporative gas emission while the internal combustion engine 1 is stopped.

  Further, according to the relief valve control routine in the present embodiment, the relief valve 10 is kept closed until the temperature of the fuel becomes equal to or lower than T1 for the first time after the internal combustion engine 1 is stopped. Therefore, after the internal combustion engine 1 is stopped, it is possible to suppress the fuel pressure in the delivery pipe 5 and the like from being generated due to the rapid drop in the fuel pressure, and it is possible to suppress the restartability from deteriorating.

  In this embodiment, the opening / closing of the relief valve 10 is controlled in S107 depending on whether or not the fuel temperature is higher than T0. However, instead of obtaining the absolute value of the temperature of the fuel, after the temperature of the fuel is once cooled to T0, the temperature change is obtained, and whether the temperature change is positive or negative, that is, the fuel changes with respect to T0. The control may be performed such that the relief valve 10 is opened when the temperature is rising, and the relief valve 10 is closed when the temperature of the fuel is lower than T0.

  In the present embodiment, as described above, after the internal combustion engine 1 is stopped, the relief valve 10 is not opened until the fuel temperature first becomes equal to or lower than T1. However, instead of this, a resistor having a minute flow path may be provided in the fuel return pipe 9.

  Examples of the minute flow path in this resistor include an orifice, a capillary, and a porous material.

  In this way, even if the relief valve 10 is opened with the fuel pressure and the fuel temperature being high immediately after the internal combustion engine 1 is stopped, the fuel pressure can be prevented from dropping sharply, and vapor is generated in the delivery pipe 5 and the like. Can be suppressed.

  A relief valve control routine in this case is shown in FIG. In FIG. 4, compared to the flow shown in FIG. 3, the processing of S103 to S105 can be omitted, and the relief valve 10 can be controlled by a simple flow.

  In the above embodiment, the fuel temperature is detected by the fuel temperature sensor 11, but may be estimated from the cooling water temperature of the internal combustion engine 1 or the like.

It is a figure which shows schematic structure of the internal combustion engine and fuel supply apparatus which concern on the Example of this invention. It is a figure which shows the relationship between the temperature of the fuel which concerns on the Example of this invention, and fuel pressure. It is a flowchart which shows the relief valve control routine which concerns on the Example of this invention. It is a flowchart shown about another example of the relief valve control routine which concerns on the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Fuel tank 3 ... Fuel pump 4 ... Fuel supply pipe 5 ... Delivery pipe 6 ... Branch pipe 7 ... Pressure regulator 8 ... Injector 9. ..Fuel return pipe 10 ... Relief valve 11 ... Fuel temperature sensor 20 ... ECU

Claims (3)

A fuel injection valve for supplying fuel to a cylinder of the internal combustion engine;
A delivery pipe for directing fuel to the fuel injection valve;
A pressure regulator that regulates the fuel pressure of the fuel pumped from the fuel tank of the internal combustion engine to the delivery pipe to a set pressure ;
A fuel return passage for returning fuel in the delivery pipe to the fuel tank;
A relief valve that is provided in the fuel return passage and opens fuel in the delivery pipe to the fuel return passage;
An internal combustion engine fuel supply apparatus comprising:
It further comprises a fuel temperature detecting means for detecting the temperature of the fuel,
When the internal combustion engine is stopped, the relief valve continues to be closed after the internal combustion engine is stopped based on the fuel temperature detected by the fuel temperature detecting means and the set pressure of the pressure regulator. Estimate the fuel pressure reference temperature, which is the temperature of the fuel when the fuel pressure becomes zero,
The fuel supply device for an internal combustion engine, wherein the relief valve is opened when the temperature of the fuel is higher than the fuel pressure reference temperature while the internal combustion engine is stopped. 2. The internal combustion engine according to claim 1, wherein the relief valve is not opened before the temperature of the fuel after the internal combustion engine is stopped first decreases to a predetermined temperature equal to or higher than the fuel pressure reference temperature. Fuel supply device. 2. The fuel supply apparatus for an internal combustion engine according to claim 1, wherein the fuel recirculation passage is provided with a resistor having a micro flow path through which fuel in the fuel recirculation passage passes.

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