JP2005030340A - Fuel supply equipment of internal combustion engine, and method for controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent breakage of a heat transfer member of a heater caused by overheat of the electric heater, and to improve the combustion when the internal combustion engine is in a cold state by enhancing the evaporation performance by providing the electric heater to promote fuel evaporation of an internal combustion engine. <P>SOLUTION: A fuel supply equipment 5 comprises an auxiliary injection valve 4 for a fuel injection valve on an air-intake passage of an internal combustion engine, an electric heater 30 to heat and evaporate injected fuel from the auxiliary injection valve 4, and a heater relay 16 to control the heat generation of the electric heater. When a state that the heat radiation from a surface of the electric heater is reduced is determined, the heat generation of the electric heater is controlled and reduced by the heater relay during the injection of the fuel injection valve so that the temperature of the heat transfer member 6 of the heater does not exceed the heat-proof temperature thereof. As a result, the surface temperature of the heat transfer member of the heater can be set to be higher than the heat-proof temperature, and the fuel evaporation performance of the electric heater can be enhanced thereby. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel supply device for an internal combustion engine using an electric heater and a control method thereof, and more particularly to a fuel supply device capable of improving combustion and reducing unburned gas when the internal combustion engine is cold, and a control method thereof. .

  As conventional technology, the fuel injected by the fuel injection valve is heated by a heater provided in the intake passage and vaporized to reduce the fuel adhering to the intake passage and the intake valve. Methods have been proposed to reduce harmful hydrocarbon emissions. As an example, in Patent Document 1, in addition to a fuel injection valve (main injection valve) provided in the vicinity of the intake port of each cylinder, a fuel injection valve (auxiliary injection valve) and an electric valve are connected to an auxiliary air passage that bypasses the upstream throttle valve. With the arrangement of the heater, the fuel is injected from the auxiliary fuel injection valve to the heater at cold start or idling, and fuel vaporization is promoted by the heater, thereby improving combustion and unburned gas from the engine ( HC) emissions are reduced.

US Pat. No. 5,894,832

  In a fuel supply apparatus having an electrically heated heater that promotes fuel vaporization in the intake passage as described above, it is generally the case that the heater is energized and the auxiliary injection valve is injected due to the limitation of power consumption of the heater. It is between several tens of seconds after start-up, and after the above time has elapsed, the injection amount of the auxiliary injection valve is gradually decreased, and during that time, the injection amount of the main injection valve is gradually increased to switch the injection valve After that, energization to the heater is stopped.

  In the above prior art, when the injection valve is switched, the fuel injection of the auxiliary injection valve is stopped and then the energization to the heater is stopped. However, the auxiliary is not performed while the injection is switched from the auxiliary injection valve to the main injection valve. The injection amount of the injection valve is smaller than the normal injection amount.

  On the other hand, the temperature of the heater heat transfer portion varies depending on the amount of fuel adhering to the heater. When there is a lot of fuel adhering to the heater, the amount of heat taken away from the heater heat transfer surface increases and the temperature of the heater heat transfer portion decreases. When the amount of fuel adhering to the heater is small, the amount of heat taken away from the heater heat transfer surface is small, so that the temperature of the heater heat transfer portion rises. This characteristic is the same for a heater using a PTC (Positive Temperature Coefficient) thermistor whose resistance is self-controlled so that the temperature of the element is constant, as well as the heater heating element type. The surface temperature on the opposite side of the surface is controlled near the set temperature (Curie point temperature) of the PTC and becomes a constant temperature. However, the PTC surface temperature on the heat transfer surface side increases as the amount of fuel adhering to the heater increases and the heat dissipation increases. Decreases with respect to the set temperature. For this reason, the temperature of the heat transfer section varies depending on the amount of attached fuel.

  Here, the heat-resistant temperature of aluminum generally used as a heater heat transfer member is about 150 ° C., and if this temperature is exceeded, the heater heat transfer member may be deformed and corrosion-resistant plating on the surface of the heat transfer member may be peeled off. It may occur or the heat transfer member may be damaged.

  On the other hand, gasoline has the highest vaporization property in the temperature range of 150 to 180 ° C. From the viewpoint of vaporization property, it is desirable that the temperature of the heater heat transfer section be 150 ° C. when the maximum fuel amount is reached. In the above prior art, there is a temperature fluctuation of the heat transfer section due to the change in the amount of fuel adhering to the heater. Therefore, when the temperature fluctuation is taken into account, the heat transfer with respect to the optimum temperature (150 ° C.) at the maximum fuel quantity is achieved. Therefore, there is a problem that the vaporization of the heater is lowered when the amount of fuel is large.

  An object of the present invention is to provide a fuel supply device capable of improving the fuel vaporization performance without impairing the durability of the electric heater and the heater heat transfer member associated therewith, and a control method thereof. .

  In order to solve the above-described problems, a fuel supply device for an internal combustion engine according to the present invention includes a fuel injection valve provided in an intake passage of the internal combustion engine, an electric heater that heats fuel injected from the fuel injection valve and promotes fuel vaporization. And a control device for the electric heater, wherein when determining a state in which the amount of heat released from the electric heater is reduced, the heat generation amount control means performs the heat generation amount control means during the injection of the fuel injection valve. The amount of heat generated by the electric heater was controlled based on the decrease in the amount of heat released. That is, the amount of heat generated is reduced by stopping or limiting the energization of the electric heater.

  In the fuel amount supply device of the present invention configured as described above, the fuel injected when the internal combustion engine is cold is promoted to vaporize by the electric heater, and the amount of unburned gas discharged from the internal combustion engine by the combustion improvement is reduced. Can be reduced. And, by switching the fuel injection valve, etc., it is possible to determine the state where the heat dissipation amount on the surface of the electric heater is reduced and reduce the heat generation amount of the heater, so that the set temperature of the electric heater can be increased and the fuel vaporization performance is improved. It is possible to prevent the electric heater and the heater heat transfer member from being deformed or damaged by overheating.

  With respect to the set temperature of the electric heater, the electric heater includes a heater heat transfer member, and the surface temperature of the heater heat transfer member in a state where the heat is not radiated when no fuel is attached to the heater heat transfer member It was set to be higher than the heat resistance temperature. The electric heater is preferably a heater using a PTC thermistor. The heater heat transfer member is preferably made of aluminum or an alloy containing aluminum as a main component, and the Curie point temperature of the PTC thermistor is preferably set to 150 ° C. or higher.

  Furthermore, as another aspect of the fuel supply device according to the present invention, a fuel injection valve provided in the intake passage of the internal combustion engine, and an electric heater that heats the fuel injected from the fuel injection valve to promote fuel vaporization, This fuel supply device is characterized by comprising a heat generation amount control means for controlling to reduce the heat generation amount of the electric heater in accordance with the control for decreasing the injection amount of the fuel injection valve. There may be a slight difference in time between the control for reducing the injection amount and the control for reducing the heat generation amount of the electric heater.

  With this configuration, the electric heater is prevented from overheating even when the injection amount of the fuel injection valve is reduced, and the electric heater and the heat transfer member associated therewith can be deformed beyond the heat resistance temperature. Is prevented and durability is improved. Further, the vaporization performance of the fuel when the internal combustion engine is cold is improved, combustion can be improved, and unburned gas can be reduced.

  As still another aspect of the fuel supply device according to the present invention, a main fuel injection valve and a sub fuel injection valve provided in an intake passage of an internal combustion engine, and an electric for heating the fuel injected from the sub injection valve to promote fuel vaporization. The fuel supply device includes a heating value control means for controlling the heating value of the electric heater to be reduced in accordance with the switching control of the main fuel injection valve and the auxiliary fuel injection valve. To do. There may be a slight difference in time between the switching control and the control for reducing the amount of heat generated by the electric heater. The heat generation amount control means preferably performs at least one of control for reducing the energization current, control for intermittently energizing time, and control for decreasing the energization voltage.

  With this configuration, even when the fuel injection amount fluctuates when switching from the auxiliary fuel injection valve to the main fuel injection valve at the start of the internal combustion engine, the electric heater, the heat transfer member associated therewith, and the like have a heat resistant temperature. It is prevented from being deformed beyond. Further, the vaporization performance of the fuel when the internal combustion engine is cold is improved, combustion can be improved, and unburned gas can be reduced.

  Further, a control method for a fuel supply device for an internal combustion engine according to the present invention includes a fuel injection valve and an air control valve provided in an intake passage, an electric heater for heating fuel injected from the fuel injection valve and promoting fuel vaporization, A control method for a fuel supply device for an internal combustion engine, comprising a heating value control means for the electric heater, comprising: a. When the fuel injection amount of the fuel injection valve decreases below a predetermined value; b. When the fuel injection amount of the fuel injection valve changes in a decreasing direction; c. When the intake air amount of the internal combustion engine decreases below a predetermined value; d. When the intake air amount of the internal combustion engine changes in a decreasing direction, e. When the ignition timing of the internal combustion engine is advanced with respect to a predetermined value, f. When the ignition timing of the internal combustion engine changes in the advance direction, g. When the rotation of the internal combustion engine decreases, h. When the current detection value of the electric heater becomes a predetermined value or less, i. In the case where the operation of reducing the injection amount of the fuel injection valve is performed by a time timer, when the time timer reaches a predetermined time, or immediately before or after the predetermined time, j. When detecting an abnormality of the air control valve and / or the fuel injection valve, detecting at least one of the states; k. When detecting a state in which the shift lever of the automatic transmission is switched from the neutral range to the drive range, when detecting at least one of the states, it is determined that the heat dissipation amount of the electric heater is reduced, During the injection of the fuel injection valve, the amount of heat generated by the electric heater is controlled based on a decrease in the amount of heat released.

  The control method of the fuel supply apparatus configured as described above determines that the amount of heat dissipated by the electric heater is reduced when detecting at least one of the states a to k, and during the injection of the fuel injection valve. In order to reduce the amount of heat generated by the electric heater, it is possible to reduce the amount of unburned gas discharged from the internal combustion engine by improving the combustion, and to increase the set temperature of the electric heater to increase the fuel vaporization performance. It is possible to prevent the electric heater and the heater heat transfer member from being deformed or damaged by overheating.

  As described above, in the present invention, a state in which the temperature of the heater heat transfer member rises is detected in a configuration including the fuel injection valve in the intake passage of the engine and the electric heater that heats and vaporizes the fuel injected from the fuel injection valve. That is, when it is determined that the amount of heat released from the surface of the electric heater is reduced, the amount of heat generated by the electric heater is reduced during the fuel injection valve injection, so the heater temperature is equal to or higher than the heat resistance temperature of the heater heat transfer member. It is possible to prevent the heater heat transfer member from being damaged.

  Further, as a result of reducing the fluctuation of the heater temperature and preventing overheating, the set temperature of the heater can be set higher than before, so that the fuel vaporization performance of the heater can be improved.

  Hereinafter, an internal combustion engine to which an embodiment of a fuel supply apparatus according to the present invention is applied will be described in detail. FIG. 1 is a main part configuration diagram of an internal combustion engine to which a fuel supply apparatus according to this embodiment is applied, and FIG. 2 is a cross-sectional view of the fuel supply apparatus of FIG.

  1 and 2, an air cleaner 2, an air amount sensor 18, and a throttle valve 10 are provided in the main air passage 1, and a main injection valve 3 is provided in the vicinity of the intake port of the cylinder 20. A bypass passage 7 is provided so as to bypass the throttle valve 10, and an air control valve 9 that controls the amount of air flowing into the engine via the fuel supply device 5 and the fuel supply device 5 is provided in the middle of the bypass passage 7. . The fuel supply device 5 includes a heater heat transfer member 6 and an auxiliary injection valve 4 provided along the inner surface of the passage. The vaporized fuel supplied from the fuel supply device 5 is supplied to the cylinder 20 through the vaporized fuel passage 8.

  The fuel supply device 5 includes an electric heater 30 and a heat transfer member 6 that transmits the heat of the heater. As a control means for controlling the in-vehicle battery 17 and the amount of heat generated by the electric heater to energize the electric heater. The heater relay 16 is connected. A resistance element 21 for detecting the current of the electric heater 30 is connected as necessary. In the vicinity of the crankshaft, a crank angle sensor 11 is installed for detecting the crank position and engine rotation. Reference numerals 12, 13, and 14 denote an ignition plug, an ignition coil, and a power switch, respectively. In addition, when an automobile equipped with this internal combustion engine has an automatic transmission, a shift lever position sensor 22 is provided.

  The air voltage sensor 18, the terminal voltage of the heater current detection resistance element 21, the signals of the crank angle sensor 11 and the shift lever position sensor 22 are input to the control unit 19, and the control unit 19 receives the main injection valve 3 and the auxiliary injection valve 4. Control signals are output to the air control valve 9, the heater relay 16, and the ignition power switch 14.

  Here, in this embodiment, the electric heater 30, the heater heat transfer member 6, and the auxiliary injection valve 4 are disposed in the bypass air passage, but the present invention is not limited to this, and the throttle valve 10 in the main air passage 1 is not limited to this. It may be arranged downstream or upstream. The main injection valve 3 is not limited to the one provided near the intake port of the cylinder 20, and may be a cylinder injection internal combustion engine in which the main injection valve 3 is disposed in the cylinder 20.

  Next, the fuel supply device 5 will be described in detail with reference to FIG. The fuel supply device 5 has a shape in which a cylindrical heating unit 35 and a housing 37 are connected. The heat transfer member 6 located on the inner circumference of the heating unit 35 is heated by the electric heater 30 to promote fuel vaporization, forms a cylindrical passage, is formed of a conductor, and is a negative electrode of the PTC thermistor. Also serves. As the electric heater 30, a PTC thermistor that generates heat when energized is used. A positive electrode 31 is positioned on the outer periphery of the electric heater 30, and a fixing member 33 for tightly fixing the positive electrode 31 to the electric heater 30 is positioned on the outer periphery. The fixing member 33 is an elastic rubber material or plate. A spring or the like is used. The heat transfer member 6 and the heating unit 35 are sealed by an O-ring 34. The housing 37 is for fixing the auxiliary injection valve 4, and an air introduction portion 36 for introducing air for promoting fuel vaporization is provided in a passage formed by the heat transfer member 6. Here, the electric heater 30 which is a heat generating member provided in the fuel supply device 5 may be a heating wire such as a nichrome wire in addition to the PTC thermistor.

  The relationship between the amount of fuel adhered to the heat transfer member and the temperature of the heat transfer member will be described below using a PTC thermistor as an example. FIG. 3 shows the relationship between the temperature and electrical resistance of the PTC thermistor. Since the PTC thermistor has a property that the electrical resistance is small below the Curie point temperature Tc and the electrical resistance rapidly increases due to the phase transition above the Curie point temperature Tc, the resistance (current) is set so that the element temperature becomes a constant temperature (Curie point). ) Is self-controlled. For this reason, the temperature of the PTC thermistor is kept constant even if the amount of heat radiation changes slightly. However, when the amount of heat radiation is large, the temperature of the PTC thermistor causes a temperature difference between a portion where heat radiation is large and a portion where heat radiation is small.

  In FIG. 4, the cross-sectional enlarged view of the heater part of the fuel supply apparatus 5 is shown. The heat transfer member 6 is attached to one side of the PTC thermistor 30, and the heat transfer member 6 also serves as a negative electrode of the PTC thermistor. A positive electrode 31 is attached to the other surface of the PTC thermistor 30, and the PTC thermistor generates heat when a current flows through the PTC thermistor sandwiched between the two electrodes. The heat generated by the PTC thermistor is transmitted to the fuel adhering to the surface of the heat transfer member via the heat transfer member 6, thereby promoting the vaporization of the fuel.

  Here, the temperature distribution of each part is shown in the lower part of FIG. When the amount of fuel adhering to the heat transfer member 6 is large, the amount of heat released from the heat transfer member 6 increases as the fuel is vaporized. Since the PTC thermistor 30 is a ceramic material, its thermal conductivity is not high, and when the amount of heat released increases, the amount of heat released increases with respect to the amount of heat supplied. Therefore, the temperature of the surface of the PTC thermistor 30 that contacts the heat transfer member 6 The temperature of the surface not in contact with the temperature is lower. Here, since the temperature of the surface of the PTC thermistor 30 that is not in contact with the heat transfer member 6 is substantially the Curie point temperature Tc, the current flowing through the PTC thermistor 30 does not increase any more. The temperature of the surface of the thermistor 30 in contact with the heat transfer member 6 is necessarily lower than Tc. When the surface temperature of the heat transfer member 6 is Ts and the temperature drop including the temperature drop at the PTC thermistor 30 and the temperature drop at the heat transfer member 6 is ΔT, Ts = Tc−ΔT.

  FIG. 5 shows the relationship between the surface temperature of the heat transfer member 6 and the maximum amount of fuel vaporized. The optimum temperature for the vaporization of the fuel is in the range of 150 to 180 ° C., and the maximum vaporization amount decreases at a temperature lower than that. Since the heat-resistant temperature of aluminum generally used for the heat transfer member 6 is about 150 ° C., if the set temperature (Curie point temperature Tc) of the PTC thermistor 30 is set to 150 ° C., the adhered fuel on the heat transfer member 6 The surface temperature of the heat transfer member 6 when the amount is large is 150 ° C.−ΔT, and the maximum vaporization amount is reduced by ΔF due to the temperature drop.

  In order to prevent the vaporization ability from being lowered due to the temperature drop of the PTC thermistor 30 or the heat transfer member 6, a method in which the Curie point temperature Tc of the PTC thermistor 30 is set higher in consideration of the temperature drop can be considered. Since the amount of fuel adhering to the heat transfer member 6 varies as described below, when the amount of adhering fuel decreases, the amount of heat release decreases and the temperature of the heat transfer member 6 rises above the heat resistance temperature. There was a problem that. Here, the Curie point temperature of the PTC thermistor can be generally set to any temperature by changing the composition of the PTC thermistor.

  FIG. 6 shows changes in the operation of the auxiliary injection valve 4 and the electric heater and the surface temperature of the heater (heat transfer member 6) when the conventional fuel supply device is started. In the engine cold state, when the main injection valve 3 performs the injection, a large amount of fuel adheres to the intake port wall surface and the intake valve, and the fuel supplied to the cylinder in the gas phase decreases, so that the combustion state deteriorates. On the other hand, when fuel vaporization is promoted by the electric heater 30, the amount of gas-phase fuel supplied to the cylinder increases, so that the combustion state is improved and the amount of harmful unburned gas discharged can be greatly reduced. Therefore, the auxiliary injection valve 4 and the heater 6 of the fuel supply device are operated by cold start.

  At (a), start cranking is started and energization of the electric heater 30 and injection of the auxiliary injection valve 4 are started as shown in (d) and (c). At this time, as shown in (b), when the injection of the main injection valve 3 is stopped or when the amount of fuel that can be vaporized by the heat transfer member 6 of the heater is insufficient, the shortage is injected by the main injection valve 3. . Here, if the electric heater 30 is always energized, the power consumption increases and the battery may deteriorate or the fuel consumption may deteriorate. In general, the energization of the electric heater 30 and the injection of the auxiliary injection valve 4 are generally performed from the start of the catalyst. It is carried out only for about several tens of seconds until the exhaust gas purification performance of the catalyst is obtained.

  Therefore, when the above-mentioned time has elapsed after starting, the injection amount of the auxiliary injection valve 4 that injects fuel toward the heat transfer member 6 of the heater is gradually decreased, and the injection amount of the main injection valve 3 is gradually increased during that time. Therefore, control for switching from the auxiliary injection valve 4 to the main injection valve 3 is required.

  (E) shows the change in the surface temperature of the heater (heat transfer member 6) from the start to the idle state after the start. Assuming that the set temperature (Curie point temperature) of the PTC thermistor is Tc, the amount of fuel adhering to the heat transfer member 6 is large in the idle state, so that the heater surface temperature drops by ΔT with respect to Tc due to heat radiation accompanying fuel vaporization. Here, as described above, when a predetermined time elapses from the start of the power consumption limitation, the injection amount of the auxiliary injection valve 4 gradually decreases until the injection amount becomes zero because the injection valve is switched. At this time, since the heat radiation amount of the heat transfer member 6 decreases, the temperature drop ΔT in the PTC thermistor 30 and the heat transfer member 6 decreases, and the heater surface temperature Ts increases to near the Curie point temperature Tc. Therefore, conventionally, in consideration of this temperature change, the set temperature of the PTC thermistor 30 is limited to about 150 ° C. which is the heat resistance temperature of the heater heat transfer member 6. For this reason, when the amount of fuel adhering to the heater is increased, the heater surface temperature is lowered, so that the fuel vaporization ability of the heat transfer member 6 is lowered, and sufficient vaporized fuel cannot be supplied to the cylinder, and the combustion state is deteriorated. There was a problem that the amount of unburned gas emissions increased.

  Further, if the set temperature of the electric heater 30 is set to be high in order to prevent the fuel vaporization ability of the heat transfer member 6 from being lowered, the temperature of the heat transfer member 6 becomes the heat resistant temperature when the amount of fuel adhering to the heater is reduced as described above. It will exceed. As a result, the heat transfer member 6 may be deformed and the corrosion resistant plating of the heat transfer member may be peeled off to cause corrosion or the heat transfer member may be damaged. At this time, the fuel enters the electric system and the electrode is corroded or fouled. If there is a contact failure due to or if there is an electrical failure, the fuel may ignite and a backfire may occur if the fuel enters.

  A first embodiment of the present invention for solving the above conventional problems will be described with reference to FIG. As in the above example, the electric heater (PTC thermistor) 30 is energized and the auxiliary injection valve 4 is injected after the start cranking is started, and the injection valve is switched after a predetermined time has elapsed after the start. In the prior art, as indicated by the dotted line (d), the injection of the auxiliary injection valve 4 was stopped and then the energization to the electric heater 30 was stopped. In the first embodiment, the solid line (d1) As shown, before the injection of the auxiliary injection valve 4 is stopped when the injection valve is switched, the energization to the electric heater 30 is stopped.

  As a result, the heater surface temperature does not rise any further even if the injection amount of the auxiliary injection valve 4 decreases or disappears as indicated by Ts2 in (e). As a result, the Curie point temperature of the PTC thermistor can be set as high as Tc2 with respect to the conventional Curie point temperature Tc1. This makes it possible to set the temperature of the heater heat transfer member 6 from the conventional Ts1 to Ts2 to a temperature optimum for fuel vaporization in a state where the amount of fuel adhering to the heater is large. The vaporization ability of the heater can be improved without impairing the durability.

  Here, as described above, even if the state in which the amount of heat release is reduced is determined and the energization stop timing of the electric heater 30 is advanced, the heater surface temperature does not decrease immediately due to the residual heat of the heater heat transfer member 6, and the heater Since the amount of fuel injection from when the energization is stopped to when the injection is stopped is small, all of the injected fuel is vaporized.

  Here, in the first embodiment, as shown in (d1), before stopping the injection of the auxiliary injection valve 4, that is, by determining the state in which the heat radiation amount is reduced, the energization to the heater is completely stopped. However, as shown in (d2), before the injection of the auxiliary injection valve 4 is stopped, the electric heater 30 is switched to reduce the ratio of the energization time of one cycle so as to suppress the temperature rise. May be.

  FIG. 8 shows the relationship between the amount of fuel adhering to the heater (heat transfer member 6), the PTC thermistor 30, the temperature drop ΔT in the heat transfer member 6, and the surface temperature of the heater (heat transfer member 6). When the amount of fuel adhering to the heater decreases, the amount of heat radiation on the heater surface decreases, and the temperature drop ΔT decreases, and the heater surface temperature increases to near the Curie point temperature of the PTC thermistor.

  FIG. 9 shows the relationship between the amount of air introduced into the heater (heat transfer member 6), the PTC thermistor, the temperature drop ΔT in the heat transfer member, and the surface temperature of the heater (heat transfer member 6). When the amount of air introduced into the heater is reduced, the amount of heat released from the heater surface is reduced, so that the temperature drop ΔT is reduced and the heater surface temperature is increased. As shown in FIGS. 8 and 9, the heater surface temperature varies depending on the amount of fuel adhering to the heater and the amount of air introduced into the heater.

  In the first embodiment, when the injection is switched from the auxiliary injection valve 4 to the main injection valve 3 after the cold start, the energization to the heater is stopped at the timing when the injection amount of the auxiliary injection valve 4 decreases. In the second embodiment described below, the state where the amount of heat dissipated on the heater surface decreases and the heater heat transfer surface temperature rises is detected in a state other than when the injection valve is switched, and the electric heater 30 is energized. Is to stop.

  In the second embodiment shown in FIG. 10, in general, when starting from a cold state, the ignition timing is set to a normal idling state for a predetermined period after the start until the exhaust pipe catalyst is activated as shown in (e). The engine temperature is promoted by retarding the timing, but when the ignition timing is retarded, the engine torque per injection amount decreases, so the idle rotation is maintained. In contrast, the fuel injection amount of the auxiliary injection valve 4 increases as compared with the case where the retardation is not performed, and the heat dissipation amount of the heater also increases. On the other hand, since the retard amount of the ignition timing decreases after the predetermined period from the start, the engine torque increases, the injection amount of the auxiliary injection valve 4 for maintaining idle rotation decreases, and the heater Since the amount of heat release decreases, the heater surface temperature rises.

  When the heater surface temperature is set near the heat-resistant temperature of the heater heat transfer member with the ignition timing retarded as described above, when the ignition timing retard amount is reduced as shown in (g), that is, a predetermined value. When the lead angle is advanced or changed in the lead angle direction, the heater heat transfer surface temperature rises as shown by the broken line and breaks the heater. Heater energization is stopped at the timing when the amount decreases (advances), so that the heat resistant temperature of the heater heat transfer member is not exceeded. Here, after the heater energization is stopped, the injection of the auxiliary injection valve 4 is stopped and the injection is switched to the main injection valve 3. At this time, since the catalyst has almost reached the activation temperature, the influence on the exhaust performance by switching the injection to the main injection valve 3 is small.

  Further, as described above, as the ignition timing retard amount decreases, the injection amount of the auxiliary injection valve 4 decreases as shown in (d), so that the injection amount of the auxiliary injection valve 4 starts or decreases in the middle. The heater energization may be stopped, and the injection of the auxiliary injection valve 4 may be stopped after the heater energization is stopped, and the injection may be switched to the main injection valve 3 in the same manner as in the above example.

  In addition, as the retard amount of the ignition timing decreases, the engine torque per engine intake air amount increases, so the amount of air introduced into the heater decreases as shown in (b). If the amount of air introduced into the heater decreases, the amount of heat released from the heater surface decreases, and the heater surface temperature rises and the heater may be damaged. The auxiliary injection valve 4 may be stopped after the heater energization is stopped, and the injection may be switched to the main injection valve 3.

  A third embodiment of the present invention will be described with reference to FIG. This embodiment is an example of an internal combustion engine of an AT vehicle having an automatic transmission. When the shift lever is switched from the neutral (N) range to the drive range (D) at the time of first idle as shown in (a), to prevent runaway. Usually, the engine speed is reduced. At this time, as shown in (c) and (e), the intake air amount of the engine and the injection amount of the auxiliary injection valve 4 are reduced and the heat dissipation amount of the heater is reduced. There is a risk that the temperature will rise above the heat resistance temperature of the heat transfer member and the heater will be damaged.

  Therefore, when the shift lever position is detected by a general shift lever position sensor 22 and the drive range is detected as shown in (f), the heater energization is stopped and the fuel amount of the auxiliary injection valve 4 is reduced before injection. It has stopped. Note that the injection of the auxiliary injection valve 4 may be stopped after the heater energization is stopped, and the injection may be switched to the main injection valve 3. At this time, as in the above-described embodiment, the heater energization may be stopped when a decrease in the intake air amount (heater introduction air amount) of the engine or the injection amount of the auxiliary injection valve 4 is detected. In the above first to third embodiments, since the heater temperature and current are not detected, a heater temperature sensor and a current detector are unnecessary, and can be implemented with a simple configuration.

  In the fourth embodiment described below with reference to FIG. 12, the heater surface temperature rise is increased when the heater current can be detected in a configuration provided with a resistance element 21 (see FIG. 1) for detecting current. It is detected by electric current and heater energization is stopped. That is, when the detected current value of the heater is equal to or less than a predetermined value, the amount of heat generated by the electric heater 30 is reduced. As described with reference to FIG. 4, since the electric resistance of the electric heater (PTC thermistor) 30 changes depending on the temperature of the PTC thermistor, by detecting the current flowing through the electric heater (PTC thermistor) 30 and the voltage of the battery 17, The electrical resistance of the PTC thermistor can be obtained and the heater temperature can be estimated.

  Assuming that the electrical resistance at the heat resistant temperature of the heater heat transfer member 6 is Rs, R <Rs is sufficient to keep the heater temperature below the heat resistant temperature, so the heater current is Ih and the battery voltage is Vb. Then, for Ih, it is necessary that the condition shown in the following formula (1) is satisfied.

Ih ≧ Vb / Rs (1)
Therefore, if the heater energization is stopped when the above condition is not satisfied from the detected values of the heater current and the battery voltage, the heater heat transfer member 6 can be prevented from exceeding the heat resistance temperature. Can be prevented from being damaged.

  FIG. 12 shows changes in the heater current when the engine is started. Immediately after the heater is energized at the time of starting, since the heater temperature is low as shown in the first half of (f), the electrical resistance of the PTC thermistor 30 is small, and the heater current is high as shown in the first half of (e). When the injection amount of the auxiliary injection valve 4 starts to decrease as shown in the latter half of (c) due to a decrease in friction or a decrease in the ignition timing retardation amount, the heat dissipation amount of the heater decreases and the heater temperature rises. Therefore, the heater current decreases as shown in the second half of (e).

  At this time, the detected value of the heater current is compared with a predetermined threshold value ISL (= Vb / Rs) obtained from the electric resistance corresponding to the heat resistant temperature of the heater expressed by the equation (1) and the battery voltage. If the heater energization is stopped when the value becomes lower than the threshold value ISL, the temperature of the heater heat transfer member 6 can be kept below the heat resistant temperature, and the heater heat transfer member 6 can be prevented from being destroyed.

  Here, generally, the resistance of the PTC thermistor 30 has the property that it becomes the minimum at a predetermined temperature lower than the Curie point. Therefore, when the heater is energized from the cold state (the state where the heater is cooled to near room temperature) as shown in (e). If the peak value Ip of the heater current is first detected and the threshold value ISL is set as a relative value (Ip × predetermined coefficient) with respect to Ip, the accuracy of heater temperature detection based on the current value can be improved. it can.

  Next, the program operation of the control unit 19 in the above-described embodiment will be described with reference to the flowchart of FIG.

  In step 100, it is determined whether the engine temperature is suitable for operating the fuel supply device 5. The fuel supply device 5 is operated in a temperature range of, for example, −10 to 30 ° C. as a temperature range in which a current required for cranking rotation of the starter can be supplied even when the heater of the fuel supply device is driven in a cold state.

  In step 110, it is checked whether the battery voltage is equal to or higher than a predetermined value in order to determine that the battery has not deteriorated.

  In step 120, in order to determine whether or not it is in an operating state in which the heater of the fuel supply device 5 is energized and the auxiliary injection valve 4 is injected, it is checked whether it is within the predetermined time TON at the time of start cranking or after start To do. If the above condition is satisfied, it is checked in step 130 whether the heater energization time THON is within a predetermined value in order to determine whether the heater temperature is low during the heating of the heater. If the heater energization time is within a predetermined value, the heater is energized in step 150, and if the engine is rotating in step 160, the auxiliary injection valve 4 is injected in step 170.

  If the heater energizing time THON is longer than the predetermined value in step 130, the heater temperature has risen to some extent, so it is determined in step 140 whether the heater heat dissipation is reduced and the heater temperature is increased. As an example, when the injection amount TINJ2 of the auxiliary injection valve 4 is smaller than a predetermined value (state a) or when the injection amount changes in a decreasing direction (state b), the intake air amount (heater introduction air amount) of the engine is predetermined. When the amount is smaller than the value (state c) or when the intake air amount changes in the decreasing direction (state d), when the ignition timing retard amount is advanced less than the predetermined value (state e) or when the ignition timing is advanced When the engine speed is lower than a predetermined value (state g), when the heater current is lower than a predetermined value (state h), when the engine speed is lower than a predetermined value (state h), the operation of reducing the injection amount of the auxiliary injection valve is performed by a time timer Then, when the time timer reaches a predetermined time or immediately before or after the predetermined time (state i), when there is a failure in the air control valve 9 or the auxiliary injection valve 4 (state j), In the AT car that has Trevor position like when a drive position (k).

  If it is determined in step 140 that the amount of heat dissipated on the heater surface is reduced, that is, the heater temperature is rising, and if the elapsed time after starting is equal to or greater than the predetermined value TON in step 120, in step 180 The energization of the heater is stopped, and in step 190, the injection amount of the auxiliary injection valve 4 is gradually reduced. At this time, the injection amount TINJ1 of the main injection valve 3 is gradually increased until all necessary supply fuel is injected by the main injection valve 3, and the injection valve is switched. Here, the timing for stopping the energization of the heater may be immediately before starting the reduction of the injection amount of the auxiliary injection valve 4 in addition to the timing of starting the reduction of the injection amount of the auxiliary injection valve 4. There is a slight delay until the heater temperature actually increases after starting the reduction of the injection amount of the valve 4, so the injection is completely stopped after the reduction of the injection amount of the auxiliary injection valve 4 is started. Until the heater is turned off.

  Furthermore, in the above-described embodiment, the state in which the amount of heat released from the heater surface decreases, that is, the state in which the heater temperature rises is determined, and the heater energization is stopped. By controlling, the heater energization ratio per switching cycle may be decreased to suppress the heater temperature rise. In this case, since the heater temperature does not decrease immediately, the injection of the auxiliary injection valve 4 is performed. There is no need to immediately reduce or stop, and the injection of the auxiliary injection valve 4 can be continued.

  As a result of the above flow, the heater temperature can be prevented from rising above the heat resistance temperature of the heater heat transfer member 6 and the heater temperature fluctuation can be reduced. As a result, the set temperature of the heater can be set higher than the conventional temperature. Can be improved.

  Further, in the above embodiments, the example of the heater using the PTC thermistor has been shown. However, the heater may be of the heating wire type, and the heater of the type that attaches the heating wire to the heat transfer member is similar to the heater of the PTC thermistor. Since the temperature of the heat transfer member varies depending on the amount of heat released from the surface, the heater energization may be stopped by determining a state in which the amount of heat released from the heater decreases and the heater temperature rises.

The principal part block diagram of the internal combustion engine to which one Embodiment of the fuel supply apparatus of this invention is applied. Sectional drawing of the fuel supply apparatus of FIG. The figure which shows the relationship between the temperature of a PTC thermistor, and electrical resistance. The figure which shows the cross-sectional enlarged view and temperature distribution of a heater. The figure which shows the relationship between heater temperature and the vaporization performance of a fuel. The figure which shows the change of the heater surface temperature in the starting operation by a conventional system. The figure which shows operation | movement of 1st Example of this invention. The figure which shows the relationship between a heater adhesion fuel amount and a heater surface temperature. The figure which shows the relationship between heater introduction air amount and heater surface temperature. The figure which shows operation | movement of 2nd Example of this invention. The figure which shows operation | movement of 3rd Example of this invention. The figure which shows operation | movement of 4th Example of this invention. The figure which shows the program operation | movement of the control unit of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Main air passage, 3 ... Main injection valve (fuel injection valve), 4 ... Auxiliary injection valve (fuel injection valve), 5 ... Fuel supply device, 6 ... Heater heat transfer member, 8 ... Vaporized fuel passage, 16 ... Heater Relay (heat generation amount control means), 17 ... vehicle-mounted battery, 18 ... air amount sensor, 19 ... control unit, 21 ... resistance element (determination means), 22 ... shift lever position sensor, 30 ... PTC thermistor (electric heater)

Claims (5)

A fuel supply apparatus comprising: a fuel injection valve provided in an intake passage of an internal combustion engine; an electric heater that heats fuel injected from the fuel injection valve to promote fuel vaporization; and a calorific value control means for the electric heater. ,
The fuel supply device reduces the heat dissipation amount of the electric heater by the heat generation amount control means during the injection of the fuel injection valve when it is determined that the heat dissipation amount on the surface of the electric heater decreases. The fuel supply device for an internal combustion engine is controlled based on   The electric heater includes a heater heat transfer member, and the surface temperature of the heater heat transfer member is set higher than the heat-resistant temperature of the heater heat transfer member in a state where there is no fuel adhering to the heater heat transfer member and heat radiation is low. The fuel supply device for an internal combustion engine according to claim 1, wherein A fuel supply device comprising: a fuel injection valve provided in an intake passage of an internal combustion engine; and an electric heater for heating fuel injected from the fuel injection valve to promote fuel vaporization,
The fuel supply apparatus includes a heat generation amount control unit that controls to decrease the heat generation amount of the electric heater in accordance with the control to decrease the injection amount of the fuel injection valve. Fuel supply device. A fuel supply device comprising a main fuel injection valve and a sub fuel injection valve provided in an intake passage of an internal combustion engine, and an electric heater for heating the fuel injected from the sub injection valve to promote fuel vaporization,
The internal combustion engine is characterized in that the fuel supply device includes a calorific value control means for controlling the calorific value of the electric heater in accordance with the switching control of the main fuel injection valve and the sub fuel injection valve. Engine fuel supply. Fuel supply for an internal combustion engine provided with a fuel injection valve and an air control valve provided in the intake passage, an electric heater for heating the fuel injected from the fuel injection valve to promote fuel vaporization, and a heating value control means for the electric heater A method for controlling an apparatus, comprising:
The following a to k states:
a. When the fuel injection amount of the fuel injection valve decreases below a predetermined value,
b. When the fuel injection amount of the fuel injection valve changes in a decreasing direction,
c. When the intake air amount of the internal combustion engine decreases below a predetermined value,
d. When the intake air amount of the internal combustion engine changes in a decreasing direction,
e. When the ignition timing of the internal combustion engine is advanced with respect to a predetermined value,
f. When the ignition timing of the internal combustion engine changes in the advance direction,
g. When the rotation of the internal combustion engine decreases,
h. When the current detection value of the electric heater becomes a predetermined value or less,
i. In the case where the operation of reducing the injection amount of the fuel injection valve is performed by a time timer, when the time timer reaches a predetermined time, or immediately before or after the predetermined time,
j. When detecting an abnormality of the air control valve and / or the fuel injection valve,
k. When detecting that the shift lever of the automatic transmission has switched from the neutral range to the drive range,
When at least one of the states is detected, it is determined that the amount of heat released from the electric heater is reduced,
A method for controlling a fuel supply device for an internal combustion engine, wherein the amount of heat generated by the electric heater is controlled based on a decrease in the amount of heat released during injection of the fuel injection valve.

Images