JP2017198096A - Fuel supply system for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel supply system for an engine that can effectively inhibit a rise of temperature of fuel for a high-pressure fuel system even when idle stop control is executed.SOLUTION: A fuel supply system for an engine includes a temperature sensor 50 for detecting fuel temperature of a first delivery pipe 26 and configured to execute forced circulation of fuel when the fuel temperature of the first delivery pipe 26 exceeds a first threshold while idle stop control is executed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an engine fuel supply device that supplies fuel to an engine fuel injection valve, and more particularly, to a fuel supply technique during execution of idle stop control.

  2. Description of the Related Art Conventionally, an engine (internal combustion engine) mounted on a vehicle such as an automobile includes, as a fuel injection valve, for example, an in-cylinder injection valve that directly injects fuel into a combustion chamber (in-cylinder). Some have an intake passage injection valve that injects fuel into the intake passage together with the inner injection valve, and some have only an intake passage injection valve. Since the in-cylinder injection valve directly injects fuel into the combustion chamber, the pressure of the fuel supplied to the in-cylinder injection valve needs to be relatively high depending on the injection timing. For this reason, an engine including an in-cylinder injection valve and an intake passage injection valve includes a high-pressure pump capable of supplying fuel at a pressure higher than the pressure (fuel pressure) of fuel supplied to the intake passage injection valve. The fuel whose pressure has been increased by the above is supplied to the in-cylinder injection valve. Even when the intake passage injection valve is disposed close to the cylinder, the fuel may be boosted by the high-pressure pump as in the case of the cylinder injection valve.

  For example, high-pressure fuel (hereinafter also referred to as “high-pressure fuel”) obtained by boosting fuel pumped from a fuel tank by a feed pump (low-pressure pump) by a high-pressure pump is supplied to an in-cylinder injection valve, while an intake passage injection valve In some cases, a high-pressure fuel is decompressed and supplied with a fuel having a lower pressure than the fuel supplied to the in-cylinder injection valve (hereinafter also referred to as “low-pressure fuel”) (see, for example, Patent Document 1).

JP2013-83184A

  Here, for example, when a fuel injection valve attached to the cylinder head is provided, such as an in-cylinder injection valve, the temperature of the fuel injection valve rises due to the heat of the cylinder head, and accordingly, the fuel injection valve There is a risk that the temperature of the supplied fuel will rise excessively.

  For example, the tip of the in-cylinder injection valve is located in the combustion chamber (cylinder) of the engine. For this reason, in a high pressure fuel system (including an in-cylinder injection valve) to which high pressure fuel is supplied, the temperature of the fuel may become high. Specifically, when the tip of the in-cylinder injection valve is heated in the combustion chamber, the heat is transferred to the high-pressure fuel system fuel (the fuel receives heat), and the fuel temperature of the high-pressure fuel system may become high. .

  In particular, in an engine including an in-cylinder injection valve and an intake passage injection valve, when the amount of fuel injected from the in-cylinder injection valve is small, such as when an operation state in which fuel is injected only from the intake passage injection valve continues, The fuel temperature of the high-pressure fuel system tends to be high.

  If the fuel temperature of the high-pressure fuel system rises excessively, deposits occur at the nozzle tip of the in-cylinder injection valve, and fluctuations in the performance of the solenoid cause variations in the injection amount. There is a risk of it. Further, bubbles may enter the high-pressure pump and the high-pressure pump may not operate normally.

  In the case where a return passage for returning surplus fuel to the fuel tank is provided as in the engine described in Patent Document 1, if the engine is operating, the surplus fuel is returned to the fuel tank via the return passage. An increase in the fuel temperature of the system can be suppressed.

  However, since the surplus fuel cannot be returned to the fuel tank while the engine is stopped when the high-pressure pump does not operate, it is difficult to suppress an increase in the fuel temperature of the high-pressure fuel system.

  For example, in recent years, so-called idle stop control has been put into practical use in which the engine is automatically stopped when the vehicle stops, such as when waiting for a signal, and is automatically restarted when the vehicle starts. If the engine is stopped by idle stop control while the engine is at a high temperature, the fuel temperature of the high-pressure fuel system may further increase.

  The present invention has been made in view of such circumstances, and even when idling stop control is being executed, an engine fuel supply device that can effectively suppress an increase in the temperature of fuel in a high-pressure fuel system. The purpose is to provide.

  A first aspect of the present invention that solves the above problems includes an electric low-pressure pump that pumps fuel in a fuel tank, a high-pressure pump that is driven by an engine that boosts the fuel pumped by the low-pressure pump, A first delivery pipe to which fuel boosted by a high-pressure pump is supplied and a first fuel injection valve is attached, and a return pipe connected to the downstream side of the first delivery pipe to return surplus fuel to the fuel tank A fuel temperature detecting means for detecting the fuel temperature of the first delivery pipe, and automatically stopping the engine when a predetermined automatic stop condition is satisfied, The fuel of the first delivery pipe is being executed while the idle stop control for restarting the engine that is automatically stopped when the restart condition is satisfied. When degree is higher than the first threshold value, lying in the fuel supply system for an engine according to claim comprising: a forced circulation means for the forced circulation of the fuel, the.

  According to a second aspect of the present invention, in the engine fuel supply apparatus according to the first aspect, the engine fuel supply device further includes an operation time integration unit that integrates an operation time at a high load of the engine, and the forced circulation unit includes the operation time integration. In the engine fuel supply device, the forced circulation of the fuel is executed when the integration result by the means is longer than a predetermined time.

According to a third aspect of the present invention, there is provided the engine fuel supply apparatus according to the first or second aspect, further comprising an injection amount integrating unit that integrates an injection amount injected from the first fuel injection valve, and the forced circulation unit. Is a fuel supply device for an engine, which performs the forced circulation of the fuel when the result of integration by the injection amount integration means is smaller than a predetermined injection amount.

  According to a fourth aspect of the present invention, in the fuel supply device for an engine according to any one of the first to third aspects, the forced circulation means includes a fuel temperature of the first delivery pipe that is lower than the first threshold value. The fuel supply device for an engine is characterized in that the forced circulation of the fuel is terminated when it is lowered to a low second threshold value.

  According to a fifth aspect of the present invention, in the fuel supply apparatus for an engine according to any one of the first to fourth aspects, a bypass passage that bypasses the high-pressure pump and connects the upstream side and the downstream side of the high-pressure pump. And a bypass valve that opens and closes the bypass passage, wherein the forced circulation means opens the bypass valve and performs the forced circulation of the fuel by the low-pressure pump. is there.

  A sixth aspect of the present invention is the engine fuel supply apparatus according to any one of the first to fifth aspects, further comprising tank temperature detection means for detecting a fuel temperature in the fuel tank, wherein the forced circulation means The fuel supply device for an engine further includes forced restart means for forcibly restarting the engine when the fuel temperature in the fuel tank becomes a predetermined temperature or more during execution of forced fuel circulation.

  According to a seventh aspect of the present invention, in the fuel supply apparatus for an engine according to the sixth aspect, the fuel supply apparatus is connected to a downstream side of the first delivery pipe via a pressure reducing device, and is more than the first fuel injection valve. A second delivery pipe to which a second fuel injection valve disposed on the upstream side of the intake passage is attached; and the forced restarting means has a fuel temperature of the first delivery pipe that is higher than the first threshold value. Is less than the larger third threshold value, the fuel is injected from the first fuel injection valve to forcibly restart the engine, and the fuel temperature of the first delivery pipe reaches the third threshold value. When it exceeds, the fuel is supplied from the second fuel injection valve, and the engine is forcibly restarted.

According to an eighth aspect of the present invention, in the fuel supply apparatus for an engine according to any one of the first to seventh aspects, the in-cylinder injection valve in which the first fuel injection valve injects fuel into the cylinder of the engine. An engine fuel supply device is characterized by the above.

  According to the present invention, even when the engine is stopped, the high-pressure fuel can be returned to the fuel tank via the return fuel. In other words, high-pressure fuel-based fuel can be appropriately circulated. For this reason, even when the idling stop control is executed and the engine is stopped, the temperature rise of the fuel in the high-pressure fuel system can be effectively suppressed.

  Therefore, when the engine is restarted, the first fuel injection valve to which fuel is supplied via the high-pressure pump, for example, the in-cylinder injection valve operates well, and an abnormality caused by bubbles in the high-pressure pump occurs. Can also be suppressed. Therefore, the amount of fuel injected from the first fuel injection valve can be made uniform.

It is the schematic which shows the fuel supply apparatus of the engine which concerns on one Embodiment of this invention. It is a block diagram which shows schematic structure of the fuel supply apparatus of the engine which concerns on one Embodiment of this invention. It is a flowchart which shows an example of the forced circulation control of the fuel which concerns on one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
A fuel supply device according to the present invention is a device that supplies fuel in a fuel tank to an engine (internal combustion engine).

  As shown in FIG. 1, an engine 10 to which a fuel supply device is applied is, for example, an in-line four-cylinder engine (internal combustion engine) mounted on a vehicle such as an automobile, and four cylinders arranged in parallel in a row. (Combustion chamber) 11 is provided. Although not shown, each cylinder 11 is provided with an ignition plug and an intake port and an exhaust port. The engine 10 further includes an intake manifold 12 connected to the intake port and an exhaust manifold 13 connected to the exhaust port.

  The engine 10 includes, for example, a plurality of (four) in-cylinder injection valves (first fuel injection valves) 14 provided in a cylinder head and directly injecting fuel into each cylinder (combustion chamber) 11, an intake passage, For example, a plurality of (four) intake passage injection valves (second fuel injection valves) 15 that inject fuel near the intake port of the intake manifold 12 are provided. That is, the intake passage injection valve 15 that is the second fuel injection valve is provided upstream of the in-cylinder injection valve 14 that is the first fuel injection valve. For example, in the present embodiment, the intake passage injection valve 15 is provided in the intake manifold 12.

  The fuel supply device 20 passes the fuel in the fuel tank 21 through the in-cylinder injection valve 14 and the intake passage injection valve 15 into the engine 10 (in the cylinder 11 or the intake manifold 12 in this embodiment). Supply. The fuel supply apparatus 20 includes a feed pump 22 that is an electric low-pressure pump and a high-pressure pump 23 that is driven by the engine 10, and the in-cylinder injection valve 14 is provided by the feed pump 22 and the high-pressure pump 23. The fuel in the fuel tank 21 is pumped to the intake passage injection valve 15.

  The feed pump 22 is provided in the middle of a low-pressure fuel pipe (low-pressure fuel passage) 24 that connects the fuel tank 21 and the high-pressure pump 23. As described above, the feed pump 22 is an electric low pressure pump, and supplies low pressure fuel (low pressure fuel) pumped from the fuel tank 21 to the high pressure pump 23. In the present embodiment, the feed pump 22 is provided outside the fuel tank 21, but may be provided inside the fuel tank 21.

  The high-pressure pump 23 is connected via a high-pressure fuel pipe (high-pressure fuel passage) 25 to a first delivery pipe (common rail) 26 to which each in-cylinder injection valve 14 is attached. The low pressure fuel supplied to the high pressure pump 23 by the feed pump 22 is increased to a predetermined pressure by the high pressure pump 23. The pressurized high-pressure fuel (high-pressure fuel) is supplied to the first delivery pipe 26, and is distributed from the first delivery pipe 26 to each in-cylinder injection valve 14. Although not shown, the high-pressure pump 23 includes a plunger that reciprocates within the cylinder using the rotation of the camshaft of the engine 10, and is configured so that the fuel is boosted by the reciprocating motion of the plunger. .

  In the present embodiment, a bypass pipe (bypass passage) 27 is provided that bypasses the high-pressure pump 23 and connects the low-pressure fuel pipe 24 on the upstream side of the high-pressure pump 23 and the high-pressure fuel pipe 25 on the downstream side. . The bypass pipe 27 is provided with a bypass valve 28 that is an on-off valve that opens and closes the bypass pipe 27. Although not shown, the bypass pipe 27 is provided with a check valve together with the bypass valve 28, and the bypass pipe 27 allows fuel to flow only from the low pressure fuel pipe 24 side to the high pressure fuel pipe 25 side. ing.

  Further, a second delivery pipe (common rail) 29 to which a plurality of intake passage injection valves 15 are attached is connected to the downstream side of the first delivery pipe 26 via a connection pipe 30. The connection pipe 30 is provided with a flow rate adjusting valve 31 for adjusting the flow rate of the fuel supplied from the first delivery pipe 26.

  The flow rate adjusting valve 31 adjusts the flow rate of the fuel by adjusting the opening thereof, and the pressure of the fuel decreases as the flow rate of the passing fuel decreases. That is, the flow rate adjustment valve 31 functions as a pressure reducing device that reduces the fuel supplied from the first delivery pipe 26 to a predetermined pressure. In the present embodiment, the high-pressure fuel supplied from the first delivery pipe 26 to the connection pipe 30 is reduced to a predetermined pressure by the flow rate adjustment valve 31. The decompressed low-pressure fuel (low-pressure fuel) is supplied to the second delivery pipe 29, and is distributed from the second delivery pipe 29 to each intake passage injection valve 15.

  One end of a return pipe (return passage) 33 is connected to the downstream side of the second delivery pipe 29 via a fuel pressure adjustment valve (regulator) 32. The other end side of the return pipe 33 is connected to the fuel tank 21. The fuel pressure adjusting valve 32 is for keeping the fuel pressure in the second delivery pipe 29 substantially constant, and mechanically opens when the fuel pressure in the second delivery pipe 29 becomes higher than a predetermined pressure. It is configured as follows.

  Such a fuel supply apparatus 20 according to the present embodiment includes a low pressure fuel pipe 24 and a high pressure fuel pipe 25 (including a bypass pipe 27), a first delivery pipe 26, a connection pipe 30, and a second tank from the fuel tank 21. The delivery pipe 29 and the return pipe 33 form a fuel supply system. Among them, the high-pressure fuel pipe 25 and the first delivery pipe 26 form a high-pressure fuel system to which high-pressure fuel distributed to the plurality of in-cylinder injection valves 14 is supplied, and the connection pipe 30 and the second delivery pipe 29 are A low-pressure fuel system is formed in which low-pressure fuel distributed to the plurality of intake passage injection valves 15 is supplied. In the fuel supply device 20 having such a fuel supply system, surplus fuel after the fuel is injected from each in-cylinder injection valve 14 and the intake passage injection valve 15 is returned to the fuel tank 21 from the return pipe 33.

  Further, as shown in FIG. 2, the vehicle includes an electronic control unit (ECU) 40. The ECU 40 includes an input / output device, a storage device that stores a control program, a control map, and the like, a central processing unit, timers, and counters. The ECU 40 performs comprehensive control of the engine 10 based on information from various sensors.

  The ECU 40 appropriately controls, for example, the fuel injection amount injected from the in-cylinder injection valve 14 and the intake passage injection valve 15 based on information from various sensors. Further, the ECU 40 constitutes a part of the fuel supply device 20 according to the present embodiment, and when the fuel injection amount injected from the in-cylinder injection valve 14 and the intake passage injection valve 15 is controlled, the operating state of the engine 10 is determined. The fuel supply state (supply amount, supply pressure, etc.) from the fuel tank 21 to the engine 10 is controlled as appropriate.

  Furthermore, the fuel supply device 20 according to the present embodiment appropriately controls the fuel supply state from the fuel tank 21 to the fuel supply system (engine 10) even when the idle stop control is executed and the engine 10 is stopped. ing. For example, the fuel supply device 20 forcibly circulates the fuel in the fuel tank 21 in the fuel supply system when the fuel temperature of the high-pressure fuel system including the in-cylinder injection valve 14 becomes high while the idle stop control is being performed. Thus, an increase in the fuel temperature of the first delivery pipe 26 that is a high-pressure fuel system is suppressed.

Below, the forced circulation of the fuel by such a fuel supply apparatus 20 is demonstrated in detail.
The ECU 40 has various functions for performing overall control of the engine 10 as described above. As one example, the ECU 40 performs idle stop control for executing idle stop control of the engine 10 as shown in FIG. Means 41 are provided. The ECU 40 further includes a forced circulation means 42, an operation time integrating means 43, an injection amount integrating means 44, and a forced restarting means 45 that constitute the fuel supply device 20.

  The idle stop control means 41 appropriately executes idle stop control based on the traveling state of the vehicle. That is, the idle stop control means 41 automatically stops the engine 10 when a predetermined idle stop condition (automatic stop condition) is satisfied, and restarts the engine 10 under automatic stop when a predetermined restart condition is satisfied. . Note that the idling stop control itself based on the restart of the engine is a known technique. For this reason, the details of idle stop control, such as idle stop conditions and restart conditions, are omitted.

  In the forced circulation means 42, when the idle stop control is being executed by the idle stop control means 41, the fuel temperature of the first delivery pipe 26 to which the plurality of in-cylinder injection valves 14 are attached is higher than the first threshold value. As one condition, forced circulation of fuel is executed. That is, the forced circulation means 42 executes the forced circulation of fuel on the condition that the fuel temperature of the high-pressure fuel system is higher than the first threshold value.

  The first delivery pipe 26 is provided with a temperature sensor (fuel temperature detection means) 50 for detecting the internal fuel temperature. When the idle stop control is executed and the engine 10 is stopped, the forced circulation means 42 first sets the fuel temperature of the first delivery pipe 26 based on the detection result of the temperature sensor 50 to a first threshold value set in advance. It is judged whether it is higher than.

  The forced circulation means 42 performs forced circulation of the fuel when the fuel temperature of the first delivery pipe 26 is higher than the first threshold while the idle stop control is being performed. In the present embodiment, Further, based on the calculation results of the operating time integrating means 43 and the injection amount integrating means 44, it is determined whether or not the forced circulation of the fuel is necessary.

  Here, the operation time integration means 43 calculates the high load operation time by integrating the operation time of the engine 10 at a high load when the engine 10 is operating (before the idle stop control is executed). . For example, the operation time integration means 43 is based on the operation region map set based on the rotation speed and the load of the engine 10 and the time when the operation state of the engine 10 is a predetermined high load operation region. To calculate the high load operation integration time. The operation time integration means 43 stores, for example, a high load operation integration time obtained by integrating the high load operation time in the past several minutes, and sequentially updates the high load operation integration time as time elapses. Of course, the period during which the operation time integration means 43 calculates the high load operation integration time is not particularly limited and may be set as appropriate.

  The injection amount integration means 44 calculates the injection amount integration value by integrating the injection amounts injected from the in-cylinder injection valves 14. The calculation method of the injection amount integration value by the injection amount integration means 44 is not particularly limited, but can be obtained based on, for example, the valve opening period (pulse width) of each in-cylinder injection valve 14. The injection amount integration means 44 also stores the injection amount integration value obtained by integrating the injection amounts in the past several minutes, and sequentially updates the stored injection amount integration value as time elapses, similarly to the operation time integration means 43. To do.

  When the high load operation integration time is relatively long, the temperature of the engine 10 is considerably increased, and it can be determined that the fuel temperature of the first delivery pipe 26 is likely to increase during the execution of the idle stop control. When the injection amount integrated value is small, for example, the fuel temperature of the entire fuel supply system (including the fuel tank) is expected to rise, and as a result, the first delivery is performed during the execution of the idle stop control. It can be determined that the fuel temperature of the pipe 26 is likely to rise.

  Therefore, the forced circulation means 42 is the first time when the fuel temperature of the first delivery pipe 26 is higher than the first threshold and the high load operation integration time is set in advance while the idle stop control is being executed. If the injection amount integrated value is longer than the first injection amount set in advance, the fuel is forcedly circulated in the fuel supply system.

  Here, the forced circulation means 42 specifically opens the flow rate adjustment valve 31 provided in the bypass valve 28 and the connection pipe 30 provided in the bypass pipe 27, and in this state, the feed that is a low-pressure pump. The forced circulation of fuel is executed by operating the pump 22. The flow rate adjustment valve 31 is always opened at a predetermined opening, and the opening of the flow rate adjustment valve 31 here is to increase the opening (preferably the maximum opening).

  Since the high-pressure pump 23 does not operate when the engine 10 is stopped, the fuel is not normally supplied to the first delivery pipe 26. However, by operating the feed pump 22 with the bypass valve 28 and the flow rate adjustment valve 31 opened, the low pressure fuel pumped from the fuel tank 21 is transferred from the low pressure fuel pipe 24 to the bypass pipe 27 and the high pressure fuel. It is supplied to the first delivery pipe 26 via the pipe 25. That is, the low pressure fuel bypasses the high pressure pump 23 and is supplied to the first delivery pipe 26. As a result, the fuel in the first delivery pipe 26 is returned to the fuel tank 21 via the connection pipe 30, the second delivery pipe 29 and the return pipe 33. That is, the fuel is forcibly circulated in the fuel supply system, and the fuel in the first delivery pipe 26 that is a high-pressure fuel system is replaced.

  Thus, while the idle stop control is being executed, the forced circulation of the fuel is appropriately executed, so that the temperature rise of the fuel in the first delivery pipe 26 that is a high-pressure fuel system is suppressed. Or the fuel temperature in the 1st delivery pipe 26 falls. Thereby, for example, the deposit at the nozzle tip of the in-cylinder injection valve 14 can be suppressed, and fluctuations in the performance of the solenoid can be suppressed. Furthermore, the entry of bubbles into the high-pressure pump 23 can be suppressed. Therefore, when the idle stop control ends and the engine 10 is restarted, it is possible to suppress variations in the amount of fuel injected from the in-cylinder injection valve 14.

  The forced circulation means 42 ends the forced circulation of the fuel when the fuel temperature of the first delivery pipe 26 has decreased to a second threshold value that is lower than the first threshold value. By stopping the forced circulation of the fuel at such timing, it is possible to effectively suppress an increase in the fuel temperature of the first delivery pipe 26 without operating the feed pump 22 wastefully. Of course, the timing for terminating the forced circulation of the fuel is not particularly limited, and may be always performed while the idle stop control is being executed, for example.

  The forced restart means 45 forcibly restarts the engine 10 when the fuel temperature in the fuel tank 21 becomes equal to or higher than a predetermined first temperature during the forced circulation of fuel by the forced circulation means 42. Specifically, after the bypass valve 28 and the flow rate adjustment valve 31 are closed, the engine 10 is forcibly restarted. In the present embodiment, a temperature sensor 51 that is a tank temperature detecting means for detecting the fuel temperature is provided in the fuel tank 21, and the forced restart means 45 is based on the detection result of the temperature sensor 51. It is determined whether or not the fuel temperature inside is equal to or higher than the first temperature.

  When the forced circulation of the fuel is performed as described above, the high-temperature fuel is returned to the fuel tank 21, so that the fuel temperature in the fuel tank 21 may be greatly increased. In this case, even if the fuel is forcibly circulated, the fuel temperature in the first delivery pipe 26 may not be sufficiently suppressed. Therefore, when the fuel temperature in the fuel tank 21 exceeds a predetermined temperature, the engine 10 is temporarily forcibly restarted to inject high temperature fuel from the in-cylinder injection valve 14 or the intake passage injection valve 15. Thereby, the rise in the fuel temperature in the first delivery pipe 26 which is a high pressure supply system can be more effectively suppressed.

  Here, in the present embodiment, the forced restarting means 45 supplies fuel from the in-cylinder injection valve 14 when the fuel temperature of the first delivery pipe 26 is equal to or lower than the third threshold value (> first threshold value). The engine 10 is forcibly restarted by injecting. In the state where the fuel temperature of the first delivery pipe 26 is relatively low, since the variation in the fuel injection amount of the in-cylinder injection valve 14 is considered to be small, the fuel is injected from the in-cylinder injection valve 14. Thereby, the engine 10 can be restarted appropriately and the rise in the fuel temperature of the first delivery pipe 26 can be effectively suppressed.

  On the other hand, when the fuel temperature of the first delivery pipe 26 exceeds the third threshold value, the forced restart means 45 injects fuel from the intake passage injection valve 15 to forcibly restart the engine 10. In the state where the fuel temperature of the first delivery pipe 26 is relatively high, since the fuel injection amount by the in-cylinder injection valve 14 is likely to vary as described above, the fuel is injected from the intake passage injection valve 15. Thereby, the engine 10 can be restarted appropriately. Also in this case, since the fuel in the first delivery pipe 26 moves to the downstream side thereof, an increase in the fuel temperature in the first delivery pipe 26 can be suppressed.

  The restart of the engine 10 by the forced restart means 45 is different from the restart of the engine 10 accompanying the end of the idling stop control, and is a temporary restart of the engine 10 that is performed while the idling stop control is being executed. is there. Therefore, for example, when the forced restart means 45 stops the engine 10 when the fuel temperature in the fuel tank 21 becomes lower than the predetermined temperature, if the idle stop condition is satisfied, the idling stop control is continued thereafter. Is done.

Next, an example of the forced circulation control of the fuel according to the present embodiment will be further described with reference to the flowchart of FIG.
As shown in FIG. 3, it is determined in step S1 whether or not the idle stop control is executed and the engine 10 is stopped. If the idle stop control is not executed (step S1: No), the process is terminated without executing the forced circulation of fuel.

  If the idle stop control is being executed (step S1: Yes), then in step S2, it is determined whether or not the fuel temperature of the first delivery pipe 26 exceeds a preset first threshold value. To do. When the fuel temperature of the first delivery pipe 26 exceeds the first threshold (step S2: Yes), in step S3, the high load operation integration time before the idle stop control is executed is determined in advance. It is determined whether it is longer than the set first time. When the high load operation integration time is longer than the first time (step S3: Yes), the injection amount integration value before the idle stop control is executed in step S4 is greater than the predetermined first injection amount. It is determined whether or not there are few. When the injection amount integrated value is smaller than the first injection amount (step S4: Yes), the process proceeds to step S5 to execute forced fuel circulation. That is, the bypass valve 28 and the flow rate adjustment valve 31 are opened, and the feed pump 22 is operated.

  In addition, when the fuel temperature of the 1st delivery pipe 26 is below a 1st threshold value (step S2: No), when a high load driving | running integration time is below the 1st time (step S3: No), or injection quantity integration value Is equal to or greater than the first injection amount (step S4: No), the series of processes is terminated without executing the forced circulation of fuel.

  When the forced circulation of fuel is started in step S5, it is then determined in step S6 whether or not the fuel temperature of the first delivery pipe 26 is equal to or lower than a second threshold (<first threshold). When the fuel temperature in the first delivery pipe 26 has decreased to the second threshold value or lower (step S6: Yes), the process proceeds to step S7, and the forced circulation of fuel is terminated. That is, the feed pump 22 is stopped and the bypass valve 28 and the flow rate adjustment valve 31 are closed.

  On the other hand, when the fuel temperature of the first delivery pipe 26 is higher than the second threshold value in step S6 (step S6: No), the process proceeds to step S8, and the fuel temperature in the fuel tank 21 is equal to or higher than the first temperature. It is determined whether or not. If the fuel temperature in the fuel tank 21 is lower than the first temperature (step S8: No), the process returns to step S6. If the fuel temperature in the fuel tank 21 is equal to or higher than the first temperature (step S8: Yes), the process proceeds to step S9, the bypass valve 28 and the flow rate adjustment valve 31 are closed, and then the engine 10 is forcibly restarted. Run.

  Specifically, in step S10, it is determined whether or not the fuel temperature of the first delivery pipe 26 exceeds a third threshold value (> first threshold value). When the fuel temperature of the first delivery pipe 26 exceeds the third threshold value (step 10: Yes), the process proceeds to step S11, fuel is injected from the intake passage injection valve 15 and the engine 10 is forcibly restarted. (MPI start). If the fuel temperature in the first delivery pipe 26 is equal to or lower than the third threshold (step S10: No), the process proceeds to step S12, in which fuel is injected from the in-cylinder injection valve 14 and the engine 10 is forcibly restarted. (DI start)

  As described above, since the fuel supply device 20 according to the present invention appropriately executes the forced circulation of the fuel during the period when the idle stop control is being executed, the fuel of the first delivery pipe 26 that is a high-pressure fuel system is used. An increase in temperature can be suppressed. Therefore, when the idle stop control is finished and the engine 10 is restarted, the variation in the fuel injection amount of the in-cylinder injection valve 14 can be suppressed.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment.
For example, in the above-described embodiment, by providing the bypass pipe and the bypass valve, the fuel is supplied to the first delivery pipe by the feed pump. However, the piping structure that connects the fuel tank and the first delivery pipe is not particularly limited. For example, an electromagnetic valve may be provided at the outlet of the high pressure pump instead of the bypass pipe and the bypass valve. In this case, when the fuel is forcedly circulated by the feed pump, the low pressure fuel is supplied to the first delivery pipe via the high pressure pump by opening the solenoid valve at the outlet of the high pressure pump. That is, the piping structure is not limited as long as the fuel can be supplied to the first delivery pipe by the feed pump to perform forced circulation of the fuel.

  In the above-described embodiment, while the idle stop control is being performed, the fuel temperature of the first delivery pipe is higher than the first threshold, the operating time integrated value is longer than the first time, and the injection amount When the integrated value is smaller than the first injection amount, forced circulation of fuel is performed. That is, when three conditions are satisfied, the forced circulation of fuel is executed. However, the forced circulation of the fuel may be performed at least when the fuel temperature of the first delivery pipe is higher than the first threshold, and may be performed when, for example, two conditions are satisfied.

  Further, in the above-described embodiment, the present invention has been described by exemplifying an engine including a first fuel injection valve to which high-pressure fuel is supplied and a second fuel injection valve to which low-pressure fuel is supplied. The invention can also be applied to an engine including only the first fuel injection valve.

  Furthermore, in the above-described embodiment, the present invention has been described by exemplifying an engine including an in-cylinder injection valve as the first fuel injection valve. However, the present invention is disposed near the combustion chamber of the engine as the first injection valve. The present invention can also be applied to an engine having an intake manifold injection valve. That is, even when the intake passage injection valve is provided as the first fuel injection valve, the temperature increase of the fuel in the high-pressure fuel system can be suppressed as in the above-described embodiment.

10 Engine 11 Cylinder 12 Intake Manifold 13 Exhaust Manifold 14 In-Cylinder Injection Valve (First Fuel Injection Valve)
15 Intake channel injection valve (second fuel injection valve)
20 Fuel supply device 21 Fuel tank 22 Feed pump (low pressure pump)
DESCRIPTION OF SYMBOLS 23 High pressure pump 24 Low pressure fuel piping 25 High pressure fuel piping 26 1st delivery pipe 27 Bypass piping 28 Bypass valve 29 2nd delivery pipe 30 Connection piping 31 Flow control valve 32 Fuel pressure adjustment valve 33 Return piping 40 Electronic control unit (ECU)
41 Idle stop control means 42 Forced circulation means 43 Operating time integration means 44 Injection amount integration means 45 Forced restart means 50, 51 Temperature sensor (temperature detection means)

Claims (8)

An electric low-pressure pump that pumps fuel in the fuel tank, a high-pressure pump that is driven by an engine that boosts the pressure of the fuel pumped by the low-pressure pump, and a fuel that is boosted by the high-pressure pump and supplied with the first fuel A fuel supply device for an engine, comprising: a first delivery pipe to which an injection valve is attached; and a return pipe connected to a downstream side of the first delivery pipe to return surplus fuel to the fuel tank,
Fuel temperature detection means for detecting the fuel temperature of the first delivery pipe;
While the idle stop control is executed, the engine is automatically stopped when a predetermined automatic stop condition is satisfied, and the engine that is being automatically stopped is restarted when the predetermined restart condition is satisfied. A fuel supply device for an engine, comprising: a forced circulation means for performing a forced circulation of fuel when the fuel temperature of one delivery pipe becomes higher than a first threshold value. The fuel supply apparatus for an engine according to claim 1,
Comprising an operation time integration means for integrating the operation time of the engine at a high load;
The engine fuel supply device according to claim 1, wherein the forced circulation means performs the forced circulation of the fuel when an accumulation result by the operation time accumulation means is longer than a predetermined time. The fuel supply device for an engine according to claim 1 or 2,
An injection amount integrating means for integrating the injection amount injected from the first fuel injection valve;
The engine fuel supply device, wherein the forced circulation means performs the forced circulation of the fuel when an integration result by the injection amount integration means is smaller than a predetermined injection amount. The engine fuel supply device according to any one of claims 1 to 3,
The engine fuel supply device, wherein the forced circulation means ends the forced circulation of the fuel when the fuel temperature of the first delivery pipe decreases to a second threshold value lower than the first threshold value. . The engine fuel supply device according to any one of claims 1 to 4,
A bypass passage that bypasses the high-pressure pump and connects the upstream side and the downstream side of the high-pressure pump, and a bypass valve that opens and closes the bypass passage,
The engine fuel supply device according to claim 1, wherein the forced circulation means opens the bypass valve to execute the forced circulation of the fuel by the low pressure pump. The engine fuel supply device according to any one of claims 1 to 5,
Tank temperature detecting means for detecting the fuel temperature in the fuel tank,
The engine further comprises forced restart means for forcibly restarting the engine when the fuel temperature in the fuel tank becomes equal to or higher than a predetermined temperature during the forced circulation of the fuel by the forced circulation means. Fuel supply device. The engine fuel supply device according to claim 6,
A second fuel injection valve is connected to the downstream side of the first delivery pipe via a pressure reducing device, and a second fuel injection valve disposed on the upstream side of the intake passage relative to the first fuel injection valve is attached. With a delivery pipe of
The forced restarting means causes the fuel to be injected from the first fuel injection valve when the fuel temperature of the first delivery pipe is equal to or lower than a third threshold value that is greater than the first threshold value. The engine is forcibly restarted, and when the fuel temperature of the first delivery pipe exceeds the third threshold value, the engine is forcibly restarted by injecting fuel from the second fuel injection valve. A fuel supply device for an engine. The engine fuel supply device according to any one of claims 1 to 7,
The engine fuel supply apparatus, wherein the first fuel injection valve is an in-cylinder injection valve that injects fuel into the cylinder of the engine.

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