JP4947026B2 - Fuel injection control device - Google Patents

Description

  The present invention relates to a fuel injection control device that controls fuel injection of an engine.

  Conventionally, a fuel injection control device for an engine that supplies fuel stored in a common rail in a high pressure state to a combustion chamber of each cylinder has been used. An improved version of such a fuel injection control device is disclosed in Patent Document 1. The fuel injection control device of Patent Document 1 restricts the discharge amount of a supply pump that pumps fuel when a common rail pressure reduction is requested, and suppresses the follow-up delay of the fuel pressure.

JP 2007-278169 A

  However, in the invention of Patent Document 1, the followability at the time of starting the engine has not been studied. The delay in boosting in the common rail may hinder appropriate fuel injection at the time of starting the engine, which may lead to deterioration of fuel consumption. Such a problem is conspicuous in an engine employing a stop-and-start system that frequently starts and stops.

  Therefore, an object of the present invention is to improve the startability of an engine incorporating a fuel injection control device having a common rail.

A fuel injection control device of the present invention that solves such a problem includes a fuel injection valve that injects fuel into a cylinder, a common rail that stores fuel supplied to the fuel injection valve in a pressurized state, and a connection to the common rail through a communication path. A pressure accumulating chamber, a supply pump for supplying high-pressure fuel to the common rail, a metering valve for metering the pumping amount of the supply pump, and the communication passage are switched between opening and closing of the communication passage. Switching means, first pressure detecting means for detecting the pressure of the fuel in the common rail, second pressure detecting means for detecting the pressure of the fuel in the pressure accumulating chamber, the first pressure detecting means and the second pressure detecting means based on the pressure information detected by the means, the metering valve, and and control means for controlling said switching means, said control means, the pressure of the fuel in the common rail target value When the pressure in the pressure accumulating chamber is higher than the pressure of the fuel in the common rail, the switching means is controlled to open the communication path, and the fuel pumping by the supply pump is stopped. The metering valve is controlled .

  With such a configuration, the rail pressure of the common rail at the time of start rises early, and as a result, the startability of the engine is improved. When the rail pressure of the common rail exceeds the target pressure, the fuel injection control device discharges the fuel into the accumulator and stores the fuel in the accumulator. On the other hand, the fuel injection control device supplies the fuel stored in the pressure accumulating chamber to the common rail when the rail pressure of the common rail is increased, such as at the time of starting. Thereby, the rail pressure of a common rail can be raised early. Thus, the fuel injection control device of the present invention improves the startability of the engine. In addition, fuel efficiency is improved by reducing friction when starting the engine and shortening the starting time.

  The present invention can improve the engine startability by increasing the rail pressure of the common rail at the time of starting at an early stage.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing an engine 100 incorporating a fuel injection control device 1 of the present invention. The engine 100 is a four-cylinder diesel engine and is mounted on a vehicle.

  The fuel injection control device 1 includes a fuel injection valve 2 that injects fuel into an engine cylinder (not shown), a common rail 3 that stores fuel supplied to the fuel injection valve 2 in a pressurized state, a common rail 3, and a communication path 5. And a pressure accumulating chamber 4 connected to each other.

  The fuel injection control device 1 further includes a supply pump 6 that supplies fuel in the fuel tank 7 to the common rail 3. The supply pump 6 is a pump that pumps fuel from the fuel tank 7 and supplies the fuel to the common rail 3 by rotating a pump drive shaft with rotation of a crankshaft provided in the engine 100. The supply pump 6 is provided with an intake metering valve (hereinafter referred to as “SCV”) 6 a that adjusts the amount of fuel pumped from the supply pump 6 to the common rail 3 by adjusting the degree of opening of the fuel flow path. It has been. The SCV 6 a is an intake metering type electromagnetic valve, and is controlled by an ECU (Electronic Control Unit) 8. When the SCV 6a is closed (OFF), the fuel pumped up from the fuel tank 7 by the supply pump 6 circulates in the supply pump 6 and the fuel pumping is interrupted.

  Furthermore, a switching valve 9 that switches between an open state and a shut-off state of the communication path 5 is provided on the communication path 5 that connects the common rail 3 and the pressure accumulation chamber 4. The switching valve 9 is an electromagnetic valve. One end of a fuel return path 10 is connected to the switching valve 9, and the other end of the return path 10 is connected to the fuel tank 7. The switching valve 9 switches between a state in which the common rail 3 and the pressure storage chamber 4 are communicated, a state in which the common rail 3 and the fuel tank 7 are communicated, and a state in which the common rail 3, the pressure accumulation chamber 4, and the fuel tank 7 are disconnected.

  The supply pump 6 and the common rail 3 are connected by a fuel supply path 11. The fuel pumped by the supply pump 6 passes through the fuel supply path 11 and is supplied to the common rail 3.

  The common rail 3 is provided with a first pressure sensor 13 that detects the pressure of the fuel in the common rail 3. The pressure accumulation chamber 4 is provided with a second pressure sensor 14 that detects the pressure of fuel in the pressure accumulation chamber 4. The first pressure sensor 13 and the second pressure sensor 14 are electrically connected to the ECU 8, and the ECU 8 acquires the pressure detected by each sensor.

  The ECU 8 is electrically connected to the switching valve 9, and opens and closes the switching valve 9 based on pressure information in the common rail 3 and the pressure accumulation chamber 4 acquired from the first pressure sensor 13 and the second pressure sensor 14. The state is determined, and a control signal related to the state of the valve is transmitted to the switching valve 9. In addition to the pressure information in the common rail 3 and the pressure accumulating chamber 4 acquired from the first pressure sensor 13 and the second pressure sensor 14, the ECU 8 uses the fuel from the supply pump 6 based on the information on the operating state of the engine 100. Determine the amount of pumping. And a control signal is transmitted to SCV6a so that it may be in the state of a valve corresponding to the amount of pumping of fuel.

  Next, the operation of the fuel injection control device 1 according to the operating state of the engine 100 will be described with reference to FIGS. FIG. 2 is an explanatory diagram showing changes in the rail pressure of the common rail 3 and changes in the internal pressure of the pressure accumulating chamber 4 accompanying changes in the operating state of the engine 100. FIG. 3 is a list of the operation of the SCV 6a, the state of the switching valve 9, and the operation of the fuel injection valve 2 in each time zone a to m in FIG.

  The vertical axis in FIG. 2 indicates pressure, and the horizontal axis indicates time. The solid line in FIG. 2 indicates the rail pressure of the common rail 3, and the broken line indicates the fuel pressure in the pressure accumulating chamber 4. A one-dot chain line indicates a target pressure of the common rail 3 controlled by the ECU 8. The left end of the graph of FIG. 2 shows the idling state. In FIG. 2, a is a time zone in which the engine 100 accelerates from an idle state, and b, c, and d are time zones in which the engine 100 is operated at the maximum rail pressure Ma. In FIG. 2, e and f are time periods when the engine 100 is decelerated, and g is a time period when the engine 100 is operating at a low load. In FIG. 2, h is a time zone in which the engine 100 is stopped, and i, j, k, and l are time zones from the start of the engine to the arrival of the idling state. M in FIG. 2 is a time zone when the engine 100 is idling.

  As shown in the graph in FIG. 2, the rail pressure of the common rail 3 and the fuel pressure in the pressure accumulating chamber 4 are a predetermined value A that is a common rail pressure at the time of idling. This specified value A is set as a pressure at which the fuel in the pressure accumulating chamber 4 can be supplied to the common rail 3 and fuel injection can be continued even when the rail pressure of the common rail 3 falls below the rail pressure during idling due to some failure.

  In the time zone a, that is, during acceleration from the idle state, the ECU 8 opens the SCV 6a. Further, the communication valve 5 is shut off and the flow to the fuel tank 7, that is, the return path 10 is shut off by the switching valve 9. In this state, a large amount of fuel is supplied to the common rail 3 and the rail pressure of the common rail 3 increases. By performing fuel injection with the rail pressure thus increased, the number of revolutions of engine 100 is increased, and the vehicle equipped with engine 100 is accelerated.

  A time zone b indicates a state in which the rail pressure of the common rail 3 has reached the maximum rail pressure Ma. At this time, the ECU 8 closes the SCV 6a and interrupts the fuel supply to the common rail 3. Even when the ECU 8 detects that the rail pressure of the common rail 3 has reached the maximum rail pressure Ma by the first pressure sensor 13 in the time zone b, even if the SCV 6a is closed, fuel is not supplied to the common rail 3 due to the time lag. Supplied can cause overshoot. Therefore, the ECU 8 brings the common rail 3 and the pressure accumulating chamber 4 into communication with each other by the switching valve 9 during the time period c. Thus, when the rail pressure in the common rail 3 is equal to or higher than the target pressure and the fuel pressure in the pressure accumulating chamber 4 is lower than the rail pressure in the common rail 3, the ECU 8 switches the switching valve 9 so as to open the communication passage 5. To control. Thereby, the excess fuel in the common rail 3 is sent into the pressure accumulating chamber 4, and the rail pressure of the common rail 3 is reduced, while the pressure in the pressure accumulating chamber 4 is increased. At this time, the ECU 8 opens the SCV 6a. As a result, fuel is supplied into the common rail 3, and the rail pressure in the common rail 3 is maintained at the maximum rail pressure Ma. When the pressure in the pressure accumulating chamber 4 acquired by the second pressure sensor 14 reaches the specified value B, the ECU 8 brings the common rail 3 and the fuel tank 7 into communication with each other by the switching valve 9 (d in FIG. 2). Time zone). Thereby, the pressure in the pressure accumulation chamber 4 is maintained at the specified value B. At this time, the ECU 8 controls the opening state of the SCV 6a and maintains the rail pressure of the common rail 3 at the maximum rail pressure Ma.

  Next, the time of deceleration will be described. The time zone e indicates the time of deceleration. At this time, the ECU 8 switches the switching valve 9 so that the common rail 3 and the pressure accumulating chamber 4 communicate with each other, that is, the communication path 5 is opened. Thus, when the rail pressure in the common rail 3 is equal to or higher than the target value and the fuel pressure in the pressure accumulating chamber 4 is lower than the rail pressure in the common rail 3, the ECU 8 switches the switching valve 9 so as to open the communication passage 5. To control. Thereby, the fuel in the common rail 3 is sent into the pressure accumulation chamber 4, the rail pressure of the common rail 3 decreases, and the pressure in the pressure accumulation chamber 4 increases. Thus, conventionally, the fuel in the common rail 3 that has been returned to the fuel tank 7 during deceleration is stored in the pressure accumulating chamber 4. Moreover, since the rail pressure of the common rail 3 falls at this time, generation | occurrence | production of abnormal noise is suppressed. The value of the prescribed value B is set to such a pressure that the fuel in the common rail 3 can be received into the pressure accumulating chamber 4 in this way. Here, the specified value B is set to a value that is half of the maximum rail pressure Ma of the common rail 3. At this time, the ECU 8 closes the SCV 6a.

  When the fuel moves from the common rail 3 to the pressure accumulating chamber 4 during deceleration, the rail pressure of the common rail 3 and the pressure in the pressure accumulating chamber 4 approach each other and then become equal. When the ECU 8 detects that the rail pressure of the common rail 3 is equal to the pressure in the pressure accumulating chamber 4 based on the values acquired from the first pressure sensor 13 and the second pressure sensor 14, the ECU 8 switches the switching valve 9. The common rail 3 and the fuel tank 7 are in communication with each other (time zone f in FIG. 2). Thereby, since the fuel of the common rail 3 is returned to the fuel tank 7, the rail pressure of the common rail 3 decreases. On the other hand, since the communication passage 5 on the pressure accumulating chamber 4 side is blocked, the fuel in the pressure accumulating chamber 4 is maintained at a pressure equal to or higher than the specified value B.

  Next, the case of low load will be described. The time zone of g shows the operation at a low load. At this time, the ECU 8 switches the switching valve 9 so that the common rail 3 and the pressure accumulating chamber 4 communicate with each other, that is, the communication path 5 is opened. At this time, the ECU 8 closes the SCV 6a. As described above, when the rail pressure in the common rail 3 is equal to or lower than the target value and the fuel pressure in the pressure accumulating chamber 4 is higher than the rail pressure in the common rail 3, the ECU 8 switches the switching valve 9 to open the communication path 5. And the SCV 6a is controlled so that the fuel pumping by the supply pump 6 is stopped. Thereby, the fuel stored in the pressure accumulating chamber 4 is supplied to the common rail 3.

  The time zone h is when the engine is stopped. At this time, the ECU 8 switches the switching valve 9 to shut off the communication path 5 so that the common rail 3 and the fuel tank 7 are in communication with each other. On the other hand, the ECU 8 closes the SCV 6a. For this reason, the fuel in the common rail 3 is returned to the fuel tank 7 and the rail pressure becomes zero. As a result, problems such as fuel being injected for some reason can be avoided, and system safety can be maintained.

  Next, a time period from when the engine 100 is started until it reaches the idling state will be described. The time zone i is an initial stage of engine start. Since this time zone is a start from the engine stop, the rail pressure of the common rail 3 starts from zero. The ECU 8 switches the switching valve 9 to make the common rail 3 and the pressure accumulating chamber 4 communicate with each other. As described above, when the rail pressure in the common rail 3 is equal to or lower than the target value and the fuel pressure in the pressure accumulating chamber 4 is higher than the rail pressure in the common rail 3, the ECU 8 switches the switching valve 9 to open the communication path 5. To control. Thereby, the fuel stored in the pressure accumulating chamber 4 is supplied to the common rail 3, and the rail pressure rises. By supplying fuel from the pressure accumulating chamber 4 to the common rail 3, the rail pressure of the common rail 3 rises early, and the startability of the engine 100 is improved. The fuel stored in the pressure accumulating chamber 4 is originally supplied from the supply pump 6 and kept at a high pressure. For this reason, the work amount by the supply pump 6 is effectively used by returning the fuel once stored in the pressure accumulating chamber 4 to the common rail 3 and using it for injection.

  When the fuel in the pressure accumulating chamber 4 is supplied to the common rail 3 and the pressure of the fuel in the pressure accumulating chamber 4 decreases to the specified value A in the time period i, the ECU 8 switches the switching valve 9 and shuts off the communication path 5. And a state where the flow to the fuel tank 7 is blocked. Further, the ECU 8 opens the SCV 6a (time zone j in FIG. 2). Thereby, fuel is supplied to the common rail 3, and the rail pressure of the common rail 3 rises. In the time zone i, the rail pressure of the common rail 3 reaches the specified value A at an early stage by supplying fuel from the pressure accumulating chamber 4. Thus, the startability of engine 100 can be improved.

  When the rail pressure of the common rail 3 acquired from the first pressure sensor 13 exceeds a certain value, the ECU 8 closes the SCV 6a (time zone k in FIG. 2). Further, the ECU 8 switches the switching valve 9 to bring the common rail 3 and the fuel tank 7 into communication with each other (time period l). When the rail pressure of the common rail 3 acquired from the first pressure sensor 13 decreases to the specified value A, the ECU 8 switches the switching valve 9 to shut off the communication path 5 and shut off the flow to the fuel tank 7. State. At this time, the ECU 8 opens the SCV 6a and enters an idling state (time zone m in FIG. 2).

  When the vehicle equipped with the engine 100 accelerates from the time zone m in FIG. 2, it is the same as the time zone a in FIG. Therefore, when the vehicle on which the engine 100 is mounted performs a normal operation, the change in the rail pressure of the common rail 3 and the change in the pressure of the fuel in the pressure accumulating chamber 4 are repeated as shown in the graph of FIG. In the fuel injection device 1 of the present invention, the rail pressure of the common rail 3 is insufficient by connecting the common rail 3 and the pressure accumulating chamber 4 and switching the communication state between the common rail 3 and the pressure accumulating chamber 4 with the switching valve 9. In the case where the fuel is stored, the fuel in the pressure accumulating chamber 4 is supplied to the common rail 3. When the rail pressure of the common rail 3 is excessive, the fuel can be stored in the pressure accumulating chamber 4. Thereby, the rail pressure suitable for the driving state can be maintained in the common rail 3. In particular, when starting the engine, the rail pressure can be increased at an early stage, so that the startability is good. In an engine employing such a start-and-stop system in which the fuel injection control device 1 is frequently started and stopped, the effect of good startability appears remarkably.

  Next, a second embodiment of the present invention will be described. FIG. 4 is an explanatory view showing an engine 200 in which the fuel injection control device 21 of this embodiment is incorporated. The fuel injection control device 21 has substantially the same configuration as the fuel injection control device 1 of the first embodiment. However, the fuel injection control device 21 is different from the fuel injection control device 1 in that a fuel supply path 22 is provided instead of the fuel supply path 11.

  The fuel supply path 22 is connected to the supply pump 6. The fuel supply path 22 branches at a branch point 22a, and the ends of the branched paths are connected to the common rail 3 and the pressure accumulating chamber 4, respectively. That is, the fuel supply path 22 is a path for supplying high-pressure fuel from the supply pump 6 to each of the common rail 3 and the pressure accumulation chamber 4. Furthermore, an electromagnetic flow rate adjusting valve 23 is disposed at the branch point 22a. The flow rate adjusting valve 23 can also be adjusted to supply fuel only to one of the common rail 3 side and the pressure accumulating chamber 4 side. For example, the flow path to the common rail 3 side can be opened and only the flow path to the pressure accumulation chamber 4 side can be blocked, or the flow path to the common rail 3 side can be blocked and only the flow path to the pressure accumulation chamber 4 side Can be opened. The flow rate adjusting valve 23 is electrically connected to the ECU 8. The ECU 8 determines the state of the flow rate adjusting valve 23 based on the pressure information in the common rail 3 and the pressure accumulating chamber 4 acquired from the first pressure sensor 13 and the second pressure sensor 14, and sends it to the flow rate adjusting valve 23. Send control signal for valve status. The ECU 8 controls the SCV 6a to adjust the amount of fuel pumped by the supply pump 6. The ECU 8 can adjust the amount of fuel supplied to the common rail 3 and the amount of fuel supplied to the pressure accumulating chamber 4 by controlling the SCV 6 a and the flow rate adjusting valve 23 in combination. In addition, since the other structure is the same as Example 1, about the component same as Example 1, the same reference number is attached | subjected in drawing and the detailed description is abbreviate | omitted.

  By providing the fuel supply path 22 and the flow rate adjusting valve 23 as described above, the fuel is supplied to the pressure accumulating chamber 4 side in the time period when the fuel is not supplied into the common rail 3 in the first embodiment. Can be accumulated. Specifically, the ECU 8 opens the SCV 6 a and opens the passage on the pressure accumulation chamber 4 side while blocking the passage on the common rail 3 side of the flow rate adjusting valve 23. With such a configuration, the supply of fuel to the pressure accumulating chamber 4 only supplies the fuel circulated in the supply pump 6 to the outside, so that it is not necessary to newly use a power source.

  When the fuel is accumulated in the pressure accumulating chamber 4 and the fuel pressure in the pressure accumulating chamber 4 is higher than the rail pressure of the common rail 3, the ECU 8 controls the control valve 9 to The pressure accumulating chamber 4 is communicated. Thereby, the fuel in the pressure accumulation chamber 4 can be supplied to the common rail 3, and the rail pressure of the common rail 3 can be raised. In particular, when the amount of fuel pumped from the supply pump 6 is small, such as when the engine is started, the rail pressure of the common rail 3 can be increased at an early stage, so that the engine startability can be improved. In this embodiment, when the engine decelerates, the fuel in the common rail 3 can be stored in the pressure storage chamber 4 as in the first embodiment.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention. It is apparent from the above description that various other embodiments are possible within the scope.

It is explanatory drawing which showed the engine incorporating the fuel-injection control apparatus of Example 1. FIG. It is explanatory drawing which showed the change of the rail pressure of a common rail accompanying the change of the driving | running state of an engine, and the change of the internal pressure of a pressure accumulation chamber. It is the list | wrist shown about the operation | movement of SCV, the state of a switching valve, and the operation | movement of a fuel injection valve in each time slot | zone of FIG. It is explanatory drawing which showed the engine incorporating the fuel-injection control apparatus of Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,21 Fuel injection control apparatus 2 Fuel injection valve 3 Common rail 4 Accumulation chamber 5 Communication path 6 Supply pump 6a Suction metering valve (SCV)
7 Fuel tank 8 ECU
9 Switching valve 13 First pressure sensor 14 Second pressure sensor 23 Flow rate adjusting valve 100, 200 Engine

Claims (5)

A fuel injection valve for injecting fuel into the cylinder;
A common rail that stores fuel supplied to the fuel injection valve in a pressurized state;
A pressure accumulating chamber connected to the common rail through a communication path;
A supply pump for supplying high pressure fuel to the common rail;
A metering valve for metering the pumping amount of the supply pump;
Switching means disposed on the communication path, for switching between opening and closing of the communication path;
First pressure detecting means for detecting the pressure of the fuel in the common rail;
Second pressure detecting means for detecting the pressure of the fuel in the pressure accumulating chamber;
Control means for controlling the metering valve and the switching means based on pressure information detected by the first pressure detection means and the second pressure detection means;
Equipped with a,
The control means controls the switching means to open the communication passage when the pressure of the fuel in the common rail is equal to or lower than a target value and the pressure in the pressure accumulating chamber is higher than the pressure of the fuel in the common rail. In addition, the fuel injection control device is characterized in that the metering valve is controlled so that the fuel pumping by the supply pump is stopped . The fuel injection control device according to claim 1,
A path for supplying high-pressure fuel from the supply pump to each of the common rail and the accumulator;
Adjusting means for adjusting the amount of fuel supplied to the common rail and the amount of fuel supplied to the pressure accumulation chamber;
A fuel injection control device comprising: A fuel injection valve for injecting fuel into the cylinder;
A common rail that stores fuel supplied to the fuel injection valve in a pressurized state;
A pressure accumulating chamber connected to the common rail through a communication path;
A supply pump for supplying high pressure fuel to the common rail;
A metering valve for metering the pumping amount of the supply pump;
Switching means disposed on the communication path, for switching between opening and closing of the communication path;
First pressure detecting means for detecting the pressure of the fuel in the common rail;
Second pressure detecting means for detecting the pressure of the fuel in the pressure accumulating chamber;
Control means for controlling the metering valve and the switching means based on pressure information detected by the first pressure detection means and the second pressure detection means;
A path for supplying high-pressure fuel from the supply pump to each of the common rail and the accumulator;
Adjusting means for adjusting the amount of fuel supplied to the common rail and the amount of fuel supplied to the pressure accumulation chamber;
A fuel injection control device comprising: The fuel injection control device according to claim 3 , wherein
When the fuel pressure in the common rail is equal to or higher than a target value and the fuel pressure in the pressure accumulating chamber is lower than the fuel pressure in the common rail, the control means is configured to open the communication path. The fuel injection control device characterized by controlling. The fuel injection control device according to claim 3 , wherein
The control means controls the switching means to open the communication passage when the pressure of the fuel in the common rail is equal to or lower than a target value and the pressure in the pressure accumulating chamber is higher than the pressure of the fuel in the common rail. A fuel injection control device.

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