JP2006299947A - Fuel supply device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device capable of quickly raising common rail fuel pressure at a time of engine start with providing a motor generator as a motor on an output side of the engine without connecting to a crank shaft. <P>SOLUTION: In a fuel supply device for an engine provided with an actuator 12 driven by the crankshaft, a high pressure fuel pump 14 of which delivery stroke gets earlier as phase of the actuator 12 gets earlier, and fuel injection valves 31A-31D supplying high pressure fuel from the high pressure fuel pump 14 to the engine, an actuator phase advancing means 35, 41 keeping the crankshaft as it is and advancing phase of only the actuator 12 with synchronizing with operation of a starter motor at a time of engine start is provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel supply device for an engine, and more particularly, to a fuel injection valve that supplies fuel discharged from a high-pressure fuel pump driven by the engine.

  An in-cylinder injection type engine has been put to practical use and proposed, in which fuel that has been boosted to a predetermined pressure by a high-pressure fuel pump is stored in a common rail and then directly supplied to the combustion chamber via a fuel injection valve. A fuel injection valve in an engine is designed to realize an optimum fuel injection shape under a predetermined pressure. For this reason, when the common rail fuel pressure at the time of starting is lower than a predetermined pressure, an optimal fuel injection shape cannot be obtained and ignition becomes difficult.

Therefore, in the technique of Patent Document 1, instead of the starter motor, a motor generator as an electric motor is disposed on the output side of the engine and connected to the crankshaft, and the common rail fuel pressure reaches a predetermined pressure when the engine is started. If not, the motor generator is operated at a high speed to rotate the crankshaft at a high speed, whereby the high pressure pump is driven at a high speed to quickly increase the actual common rail fuel pressure to a predetermined pressure.
Japanese Patent Laid-Open No. 9-7266

  By the way, in an engine having a high-pressure fuel pump whose discharge stroke becomes faster as the phase of an actuator (for example, a pump drive cam) driven by the engine becomes earlier, the crankshaft is cranked by a starter motor when the engine is started. Therefore, the characteristics of the high-pressure fuel pump are greatly affected by the starter motor. In other words, the start time of the pump drive cam rotation speed at the start of the engine is determined by the specifications (characteristics) of the starter motor, so that depending on the phase of the pump drive cam at the low cranking initial stage, the fuel discharge of the high pressure fuel pump It may take some time to reach timing. At this time, if the common rail fuel pressure is not sufficient, fuel injection cannot be performed, and the time until the first explosion is prolonged.

  Further, in a low rotation speed state where cranking is very initial, the discharge efficiency of the high-pressure fuel pump is poor and the common rail fuel pressure may not be increased.

  In this case, if the description in Patent Document 1 is applied as it is and a motor generator as an electric motor is arranged on the output side of the engine and connected to the crankshaft, the cost increases and the apparatus becomes large.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a device that can quickly increase the common rail fuel pressure at the time of engine startup without disposing a motor generator as an electric motor on the output side of the engine and connecting it to a crankshaft.

  The present invention relates to a starter motor, an actuator driven by a crankshaft, a high-pressure fuel pump whose discharge stroke is accelerated as the phase of the actuator is earlier, and a fuel injection valve for supplying high-pressure fuel from the high-pressure fuel pump to an engine In accordance with the operation of the starter motor at the start of the engine, the crankshaft is left as it is, and the phase of only the actuator is advanced.

  According to the present invention, the phase of only the actuator driven by the crankshaft is advanced while keeping the crankshaft in accordance with the operation of the starter motor at the start of the engine, so that the discharge stroke of the high-pressure fuel pump is made much faster. As a result, the fuel discharge efficiency of the high-pressure fuel pump is improved, and the time until the first explosion is shortened compared to the case of the conventional device that does not advance the phase of the actuator driven by the crankshaft.

  Further, since it is sufficient to rotate only the actuator without changing the crankshaft, it is possible to increase the fuel pressure more responsively than when the crankshaft is rotated at a high speed as in Patent Document 1, and as in Patent Document 1. This is more efficient than rotating the crankshaft at high speed.

  1 is a schematic configuration diagram of a fuel supply device for an engine according to an embodiment of the present invention, FIG. 2 is a plan view of a pump drive cam 12 (plate cam), and FIG. is there.

  In FIG. 1, the fuel supply device of the engine mainly includes a fuel tank 1, a feed pump 2, a high-pressure fuel pump 11, a common rail (fuel gallery) 21, and a fuel injection valve.

  The feed pump 2 is driven by the electric motor 3 and pumps the fuel in the fuel tank 1 to the fuel supply passage 8. Fuel filters 4 and 5 are provided on the upstream side and the downstream side of the feed pump 2, respectively. In order to prevent the discharge pressure of the feed pump 2 from exceeding a certain pressure, a low-pressure pressure regulator 6 is provided in a return passage 9 that branches from the fuel supply passage 8 and returns to the fuel tank 1.

  The fuel discharged from the feed pump 2 is supplied to the high-pressure fuel pump 11 through the fuel supply passage 8. The fuel supply passage 8 is provided with a damper 10 for suppressing fuel pressure pulsation.

  The configuration (not known) of the high-pressure fuel pump 11 will be described. The high-pressure fuel pump 11 includes a pump drive cam 12 (plate cam) as an actuator driven by a crankshaft, and a plunger pump 14 driven by the pump drive cam 12. And a normally closed suction check valve 15, a normally closed discharge check valve 16, and a control solenoid 17. The plunger pump 14 further includes a cylinder 14a, a plunger 14b that is driven by the peripheral surface of the pump drive cam 12 and reciprocated in the vertical direction in the figure, and a high-pressure chamber defined by the plunger 14b and the cylinder 14a. 14c, a spring 14d for urging the plunger 14b toward the peripheral surface of the cam 12, and a spill passage 18 for returning the fuel in the high pressure chamber 14c to the fuel tank 1.

  As shown in FIG. 2, the pump drive cam 12 has lift portions that rise from the base circle at left and right opposing positions that are 180 degrees apart, and the pump drive cam 12 rotates clockwise in FIG. As a result, the spring 14d biases the plunger 14b in the direction of the cam 12 when descending from the left or right maximum lift position shown in FIG. 2 to the base circle, so that the plunger 14b moves downward in FIG. . When the pump drive cam 12 further rotates and this time rises toward the other maximum lift position on the opposite side 180 degrees away from the base circle, the plunger 14b resists the biasing force of the spring 14d in FIG. Move upward.

  FIG. 3 shows the operation of the high-pressure fuel pump 11 as a model. Now, when the suction check valve 15 is opened at the timing t1 when the plunger 14b is at the highest lift position, and when the plunger 14b is lowered from the highest lift position to the timing t2 when the lowest lift position is reached, the feed pump 2 is supplied to the high pressure chamber 14c. Of low pressure fuel. That is, the section from t1 to t2 is the intake stroke of the high-pressure fuel pump 11.

  The plunger 14b rises toward the maximum lift position from t2, but at this time, since the control solenoid 17 opens the spill passage 18, the fuel in the high pressure chamber 14c is returned to the fuel tank 1 through the spill passage 18. However, the fuel in the high-pressure chamber 14 c is not pumped to the common rail 21.

  When the plunger 14b rises and the control solenoid 17 closes the spill passage 18 at the timing t3, the fuel pressure in the high-pressure chamber 14c is increased during the period from the timing t3 to the timing t4 when the plunger 14b reaches the maximum lift position. Ascending, the discharge check valve 16 is opened, and high-pressure fuel is supplied to the common rail 21 through the orifice 19. That is, the section from t2 to t3 is the spill stroke of the high-pressure fuel pump 11, and the section from t3 to t4 is the discharge stroke of the high-pressure fuel pump 11. A series of operations in a section from t1 to t4 is a group, and after the timing of t4, this group of operations is repeated.

  As the timing at which the control solenoid 17 closes the spill passage 18 (timing at t3) is advanced, the discharge amount of the high pressure fuel pump 11 increases, and conversely, as the timing at which the control solenoid 17 closes the spill passage 18 is delayed, the high pressure fuel pump 11 is increased. The discharge amount of the high-pressure fuel pump 11 can be controlled by controlling the timing at which the control solenoid 17 closes the spill passage 18 to the advance side or the retard side.

  Returning to FIG. 1, the pump drive cam 12 is provided integrally with the intake valve camshaft 13. The cam sprocket fixed to the front end of the intake valve camshaft 13 and the front end of a crankshaft (not shown). A chain or belt is wound around a fixed crank sprocket, and the intake valve camshaft 13 is indirectly driven by the crankshaft.

  Further, a valve timing control mechanism (hereinafter referred to as “VTC mechanism”) 35 capable of continuously controlling the phase of the intake valve to an arbitrary position while keeping the operating angle constant is provided at the front portion of the camshaft 13 for the intake valve. It has been.

  Since the configuration of the VTC mechanism 35 is known, detailed description thereof will be omitted. However, in the case of an electromagnetic type, for example, when a voltage is applied to the electromagnetic retarder to generate a magnetic force, the torsion spring is overcome and the drum rotates. The brake is applied, and the intake valve camshaft 13 is advanced through this action. The state where no voltage is applied to the electromagnetic retarder is the initial state, and the intake valve camshaft 13 (intake valve) is at the most retarded position. In the engine controller 41, the intake valve opening timing is continuously controlled via the VTC mechanism 35 in accordance with the operating conditions, so that both improvement in output / torque and fuel consumption / exhaust performance can be achieved.

  A safety valve 22 is provided at the rear end of the common rail 21. When the actual common rail fuel pressure exceeds the allowable pressure, the safety valve 22 is opened and a part of the high-pressure fuel in the common rail 21 is returned to the fuel tank 1.

  The high-pressure fuel stored in the common rail 21 is distributed to the high-pressure fuel injection valve of each cylinder. FIG. 1 shows a case of a four-cylinder engine, and high-pressure fuel stored in the common rail 21 acts on the four high-pressure fuel injection valves 31A, 31B, 31C, and 31D. In this case, the high pressure fuel injection valves 31A to 31D are provided facing the combustion chambers of the respective cylinders, and the stratified combustion can be performed from the time of starting the engine by setting the fuel injection timing of each cylinder to the compression stroke. .

  When the fuel injection valves 31A to 31D are opened at a predetermined timing according to the ignition timing of each cylinder, fuel is supplied to the combustion chamber of the cylinder having the opened fuel injection valve. In addition, the fuel pressure in the common rail 21 decreases due to the disappearance of a predetermined amount of fuel from the fuel injection valve.

  For this reason, the engine controller 41 has in advance a target fuel pressure of the common rail 21 corresponding to the engine load and the rotational speed as a map, and the actual fuel pressure of the common rail 21 detected by the fuel pressure sensor 42 is determined at that time. The discharge amount of the high-pressure fuel pump 11 is controlled via the control solenoid 17 so as to coincide with the target fuel pressure corresponding to the engine load and the rotational speed. For example, when the actual common rail fuel pressure is lower than the target fuel pressure, the timing at which the control solenoid 17 closes the spill passage 18 is advanced to increase the discharge amount of the high-pressure fuel pump 11 to increase the actual common rail fuel pressure to the target fuel pressure. Move closer. On the other hand, when the actual common rail fuel pressure is higher than the target fuel pressure, the timing at which the control solenoid 17 closes the spill passage 18 is delayed to reduce the discharge amount of the high-pressure fuel pump 11 and to decrease the actual common rail fuel pressure. Approach the fuel pressure.

  When the engine load and the rotational speed are determined, the required fuel amount per cylinder is uniquely determined. When the required fuel amount per cylinder and the target fuel pressure are determined, the valve opening pulse width of the fuel injection valve is determined. Therefore, in the engine controller 41, a map of the required fuel amount per cylinder according to the engine load and the rotational speed, and a map of the fuel injector valve opening pulse width according to the required fuel amount per cylinder and the target fuel pressure, respectively. And search the map for the required fuel amount per cylinder and the target fuel pressure map from the engine load and the rotational speed at that time to obtain the required fuel amount per cylinder and the target fuel pressure. A map of the injection pulse width is searched to obtain the valve opening pulse width of the fuel injection valve. When the predetermined injection timing is reached, the fuel injection valve is opened at this valve opening pulse width and fuel is supplied to each cylinder.

  Now, when the engine is started, the crankshaft is cranked and started by a starter motor (not shown). Therefore, the characteristics of the high-pressure fuel pump 11 are greatly influenced by the starter motor. That is, when the engine is started, the rise time of the rotational speed of the pump drive cam 12 is determined by the specifications (characteristics) of the starter motor. Therefore, depending on the phase of the pump drive cam 12 at the low speed in the initial stage of cranking, the high pressure fuel pump 11 It may take time to reach the fuel discharge timing. At this time, if the common rail fuel pressure is not sufficient, fuel injection cannot be performed, and the time until the first explosion is prolonged. Further, in a low rotation speed state where cranking is very initial, the discharge efficiency of the high-pressure fuel pump 11 is poor and pressure increase may not be possible.

  Accordingly, the present invention operates the VTC mechanism 35 as a phase control mechanism in accordance with the operation of the starter motor when the engine is started, and advances the phase of only the pump drive cam 12 without changing the crankshaft. Increase the rising speed of cam rotation.

  This will be further described with reference to FIG. 4. FIG. 4 is a waveform diagram showing changes in several signals from engine start. In FIG. 4, the ignition switch, the starter switch 45, the rotational speed of the pump drive cam 12 in the case of the conventional device, the rotational speed of the pump drive cam 12 in the case of the present invention, the cam lift of the pump drive cam 12 in the case of the conventional device, Each state of the cam lift of the pump drive cam 12, the high-pressure fuel pump 11, and the VTC mechanism 35 in the case of the present invention is shown. Here, the waveform of the cam lift amount of the pump drive cam 12 is shown as a saw blade, but this is a simplification and is actually the same as the plunger lift shown in the uppermost part of FIG. The horizontal axis is time.

  When the starter switch is turned ON from OFF at the timing t11 and the starter motor is operated, in the conventional apparatus, the rotation speed of the pump drive cam 12 is slightly delayed from t11 as shown in the third stage of FIG. The first explosion was started at t15. At this time, the rise time of the rotational speed of the pump drive cam 12 is A as shown in the third row of FIG.

  On the other hand, according to the present invention, the VTC mechanism 35 is operated at the timing t12 after the starter switch 45 is turned on, and the intake valve (that is, the intake valve camshaft 13) is moved from the most retarded position which is the initial position. Advance to the most advanced position. Since the pump drive cam 12 is integral with the intake valve camshaft 13, the phase of the pump drive cam 12 is advanced by the advance angle of the intake valve. When the phase of the pump drive cam 12 is advanced, the rising speed of the rotation of the pump drive cam is increased by that amount. The rise time of the rotational speed of the pump drive cam 12 at this time is B as shown in the fourth stage of FIG. 4, and the rise time of the rotational speed of the pump drive cam 12 is shorter than that of the conventional device. Further, advancing the phase of the pump drive cam 11 corresponds to moving the plunger lift waveform to the left as it is in the uppermost stage in FIG. 3, and therefore the discharge stroke of the high pressure fuel pump 11 also moves to the left (high pressure fuel pump). 11 is faster).

  By shortening the rise time of the pump drive cam rotation speed immediately after the start, that is, by increasing the rise speed of the pump drive cam rotation immediately after the start, the plunger speed of the high-pressure fuel pump 11 driven by the pump drive cam 12 is increased and the fuel is increased. As the discharge efficiency is improved and the common rail fuel pressure rises early, the timing at which compression stroke injection (that is, stratified combustion) can be started is earlier, and the first explosion is obtained at the timing t14. The time until the first explosion is shorter than in the case of the conventional device.

  Further, the operation of the VTC mechanism 35 is finished at the timing t13 when the discharge characteristic of the high-pressure fuel pump 11 is stabilized.

  For such control, a signal from the crankshaft position sensor 43 and a signal from the camshaft position sensor 44 are input to the engine controller 41 together with a signal from the starter switch 45.

  This control executed by the engine controller 41 will be described in detail according to the flowchart of FIG.

  FIG. 5 is for controlling the phase of the pump drive cam 12 and is executed at regular intervals (for example, every 10 msec).

  In step 1, the signal from the starter switch 45 is observed. When the signal from the starter switch 45 is OFF, the current process is terminated as it is.

  When the signal from the starter switch 45 is ON, the process proceeds to step 2 to check whether the engine is rotating. When it is determined that the engine is not rotating, the current process is terminated, and when it is determined that the engine is rotating, the process proceeds to step 3.

  The reason for proceeding to step 3 and later only when the engine is rotating is that it is not desired to operate the VTC mechanism 35 before the engine rotates.

  Whether or not the engine is rotating may be based on a signal from a crank angle sensor. That is, the crankshaft position sensor 43 is provided on the crankshaft for detecting the crank angle, and the camshaft position sensor 44 is provided on the camshaft 13 for the intake valve for cylinder discrimination. It may be determined whether or not the engine is rotating. Further, in the flow not shown, the engine speed Ne is calculated based on these two signals.

  In step 3, the phase control end flag (initially set to zero when the ignition switch is turned on) is checked. Since the phase control end flag = 0 at the beginning when the signal from the starter switch 45 is turned ON, the routine proceeds to step 4 where the VTC mechanism 35 is operated and the intake valve camshaft 13 is the most retarded angle that is the initial position. Advance from the position to the most advanced position. As a result, the phase of the pump drive cam 12 integral with the intake valve camshaft 13 advances.

  In step 5, a timer is started (timer value = 0). This timer is for measuring the elapsed time since the VTC mechanism 35 was operated.

  In step 6, the engine rotational speed Ne calculated by a flow (not shown) is compared with the specified rotational speed. Here, the specified rotational speed is a determination value for ending the operation of the VTC mechanism 35, and a value of, for example, about 100 rpm is set. When the engine rotational speed Ne is equal to or lower than the specified rotational speed, it is determined that the high-pressure fuel pump 11 is not yet operating stably, and the routine proceeds to step 7 where the timer value is compared with the specified time. As the specified time, the time that the VTC mechanism 35 operates and the intake valve camshaft 13 moves from the most retarded position, which is the initial position, to the most advanced position becomes a standard. If the timer value is less than the specified time, the current process is terminated.

  Steps 6 and 7 are executed from the next time. At the beginning of cranking, the engine speed Ne does not reach the specified speed, and the timer value does not reach the specified time. .

  Eventually, when the engine speed Ne increases and exceeds the specified speed, the speed of the plunger 14b becomes equal to or higher than the specified speed, and it is determined that fuel does not leak and the high-pressure fuel pump 11 operates stably, and the VTC mechanism 35 operates. Therefore, the process proceeds from step 6 to step 8 to set the phase control end flag = 1.

  Further, when the timer value exceeds the specified time while the engine rotation speed Ne is equal to or less than the specified rotation speed, the process proceeds from step 7 to step 8 to set the phase control end flag = 1 in order to end the operation of the VTC mechanism 35. This is because even if the engine rotational speed Ne does not reach the specified rotational speed, the intake valve camshaft 13 (pump drive cam 12) cannot be advanced beyond the most advanced position, so that the pump drive cam This is to end the phase control of 12 and move to the next stage.

  On the other hand, when the phase control end flag = 1, the current processing is terminated as it is from step 3 from the next time. That is, after the phase control end flag = 1, it is not possible to proceed from step 3 to step 4. As a result, the phase control of the pump drive cam 12 is performed during the period from when the starter switch 45 is switched from OFF to ON until the engine rotational speed Ne increases and reaches the specified rotational speed.

  In the flow not shown, when the phase control end flag = 1, the intake valve closing timing is controlled according to the operating conditions using the VTC mechanism 35 as is done by the conventional device. Since this intake valve closing timing control is not related to the present invention, a description thereof will be omitted.

  Here, the operation of the present embodiment will be described.

  According to this embodiment (the invention described in claim 1), a starter motor that operates when the engine is started to crank the crankshaft of the engine, a pump drive cam 12 (actuator) that is driven by the crankshaft, The pump drive cam 12 includes a high-pressure fuel pump 14 whose discharge stroke is accelerated as the phase of the pump-drive cam 12 is advanced, and fuel injection valves 31A to 31D that supply high-pressure fuel from the high-pressure fuel pump 14 to the engine. In accordance with the operation of the starter motor, the phase of only the pump drive cam 12 is advanced while the crankshaft remains unchanged (steps 1 and 4 in FIG. 5), so that the discharge stroke of the high-pressure fuel pump 11 becomes that much faster. As shown in the 4th and 5th tiers of FIG. 4, the time until the first explosion is improved. Shortened to the A of the conventional device to B.

  Further, since only the pump drive cam 12 needs to be rotated while the crankshaft remains as it is, the fuel pressure can be increased more responsively than when the crankshaft is rotated at a high speed as in Patent Document 1, and Patent Document This is more efficient than the case where the crankshaft is rotated at a high speed as in FIG.

  In the embodiment, the VTC mechanism is provided at the front end portion of the intake valve camshaft, the pump drive cam 12 is provided on the intake valve camshaft, and the high pressure fuel pump is driven by the pump drive cam. The configuration is not limited. For example, the high-pressure fuel pump may be of a swash plate type, or the exhaust valve camshaft may be provided with a VTC mechanism, and the pump drive cam 12 may be provided on the intake valve camshaft. Furthermore, the pump drive cam can be provided on a shaft other than the camshaft.

  In the embodiment, the case where the fuel injection valve is provided directly facing the fuel chamber has been described. However, the present invention can be applied to the case where the fuel injection valve is provided facing the intake port. It is not essential to provide a common rail.

  The function of the actuator phase advance means of claim 1 is performed by the VTC mechanism 35 and steps 1 and 4 of FIG.

1 is a schematic configuration diagram of a fuel supply device according to a first embodiment of the present invention. The top view of a pump drive cam. The wave form diagram for demonstrating the action | operation of a high pressure fuel pump. The wave form diagram for demonstrating the effect | action of this invention. The flowchart for demonstrating the phase control of a pump drive cam.

Explanation of symbols

12 Pump drive cam (plate cam)
13 Intake valve camshaft 31A to 31D Fuel injection valve 35 VTC mechanism (phase control mechanism)
41 Engine controller

Claims (4)

A starter motor that operates at engine startup and cranks the crankshaft of the engine;
An actuator driven by a crankshaft;
A high-pressure fuel pump in which the discharge stroke becomes faster as the phase of this actuator becomes earlier,
In a fuel supply device for an engine comprising a fuel injection valve for supplying high-pressure fuel from the high-pressure fuel pump to the engine,
An engine fuel supply device comprising actuator phase advance means for advancing the phase of only the actuator without changing the crankshaft in accordance with the operation of the starter motor when the engine is started.   The actuator is a plate cam that moves integrally with a shaft driven by a crankshaft, and the actuator phase advance means includes a phase control mechanism that can advance and retard the phase of the shaft relative to the crankshaft; 2. The fuel supply apparatus for an engine according to claim 1, further comprising control means for controlling the phase control mechanism so that the phase of the plate cam is advanced in accordance with the operation of the starter motor at the time of starting.   The engine fuel supply device according to claim 2, wherein the shaft is a camshaft that moves integrally with an intake valve or an exhaust valve.    2. The fuel supply apparatus for an engine according to claim 1, wherein the fuel injection valve is provided directly facing a combustion chamber of the engine, and the fuel injection valve is opened only for a predetermined period in a compression stroke.

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