Multi-cylinder engine and outboard motor

A multi-cylinder engine includes a plurality of cylinders that are fired at uneven intervals. A controller is configured or programmed to overlap a time period that a plunger increases a pressure in a pressurizing chamber and a time period that an electromagnetic valve remains opened in at least the longest one of the intervals at which the firing is conducted in the plurality of cylinders.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multi-cylinder engine and an outboard motor including the multi-cylinder engine.

2. Description of the Related Art

In some multi-cylinder engines, firing is conducted at uneven intervals. For example, in the V8 engine (eight-cylinder V-shaped engine) described in Japan Laid-open Patent Application Publication No. 2008-031897, firing is conducted eight times at even intervals within a crank angle of 720 degrees. However, focusing on only one of two banks, firing is conducted at uneven intervals.

In recent years, a plunger high pressure fuel pump has been used in direct fuel injection engines. The plunger fuel pump drives a plunger with a cam and causes the plunger to compress fuel so that the fuel is discharged at a high pressure. The cam is provided with a plurality of cam lobes, and the cam lobes press the plunger in conjunction with rotation of the cam. Thus, the plunger is driven.

Considering the strength of the cam, the cam lobes are preferably arranged at even intervals. When the cam lobes are arranged at even intervals, the pump discharges fuel at even intervals.

On the other hand, when firing is conducted at uneven intervals as with the above-described engine, fuel is also injected into the combustion chambers at uneven timings. When fuel is injected into the combustion chambers at uneven intervals while fuel is discharged from the pump at even intervals, a difference in fuel pressure among the cylinders is inevitably caused when injecting fuel into the cylinders. For example, the fuel pressure increases when firing is conducted at a long interval, whereas the fuel pressure decreases when firing is conducted at a short interval. This difference in fuel pressure among the cylinders is not preferable because it results in a difference in performance among the cylinders and further leads to an increase in labor to adapt the engine, or it degrades the efficiency of the engine.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention significantly reduce or prevent a difference in fuel pressure among the cylinders, which is caused by firing being conducted at uneven intervals, in a direct fuel injection multi-cylinder engine.

A multi-cylinder engine according to a preferred embodiment of the present invention includes a plurality of cylinders, a plurality of fuel injectors, a fuel supply pipe, a fuel pump, and a controller. The fuel injectors are respectively mounted to the cylinders, and directly inject fuel into the combustion chambers of the cylinders. The fuel supply pipe is connected to the fuel injectors so as to supply the fuel thereto. The fuel pump supplies the fuel to the fuel supply pipe. The controller is configured or programmed to control the fuel pump.

The fuel pump includes a pump body, a plunger, an electromagnetic valve, a one-way valve, and a cam. The pump body includes a suction port, a pressurizing chamber, and a discharge port. The plunger varies the pressure in the pressurizing chamber. The electromagnetic valve opens and closes a pathway between the suction port and the pressurizing chamber. The one-way valve allows the fuel to flow out therethrough in a direction from the pressurizing chamber to the discharge port. The cam includes a plurality of cam lobes that drive the plunger. The cam lobes are circumferentially disposed at even intervals.

Firing is conducted in the cylinders at uneven intervals. The controller is configured or programmed to overlap a time period that the plunger increases the pressure in the pressurizing chamber and a time period that the electromagnetic valve remains opened in at least the longest one of the intervals at which the firing is conducted in the cylinders.

An outboard motor according to another preferred embodiment of the present invention includes the above-described multi-cylinder engine, a driveshaft, and a propeller shaft. The driveshaft is driven by the engine and extends in a vertical direction. The propeller shaft is connected to the driveshaft and extends in a direction perpendicular or substantially perpendicular to the driveshaft.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments will be hereinafter explained with reference to the attached drawings.FIG. 1is a side view of an outboard motor1according to a preferred embodiment of the present invention. The outboard motor1includes an engine cover2, an engine3, a power transmission mechanism4, an upper case5, and a lower case6. The engine cover2covers the engine3. The engine3includes a crankshaft11. The crankshaft11extends in the vertical direction.

The power transmission mechanism4transmits a driving force from the engine3to a propeller12. The power transmission mechanism4includes a driveshaft13, a propeller shaft14, and a shift mechanism15. The driveshaft13extends in the vertical direction. The driveshaft13is coupled to the crankshaft11and is rotated by the engine3.

The propeller shaft14is coupled to a lower portion of the driveshaft13through the shift mechanism15. The propeller shaft14extends in the back-and-forth direction. The propeller shaft14extends in a direction perpendicular or substantially perpendicular to the driveshaft13. The propeller12is attached to the rear end of the propeller shaft14. The propeller shaft14transmits a driving force from the driveshaft13to the propeller12.

The propeller12is disposed in a lower portion of the outboard motor1. The propeller12is rotationally driven by the driving force from the engine3. The shift mechanism15switches the rotational direction of a power transmitted from the driveshaft13to the propeller shaft14.

The upper case5is disposed under the engine cover2. The upper case5covers the driveshaft13. The lower case6is disposed under the upper case5. The lower case6covers the propeller shaft14.

Next, the engine3will be explained in detail.FIG. 2is a plan view of the engine3.FIG. 3is a schematic diagram of a construction of the engine3. The engine3is a multi-cylinder engine including a plurality of cylinders C1to C8. The engine3includes a first bank21of cylinders and a second bank22of cylinders. As shown inFIG. 3, the first bank21preferably includes four cylinders C1, C3, C5and C7. The second bank22preferably includes four cylinders C2, C4, C6and C8, and preferably is disposed in a V-shaped alignment with the first bank21. In other words, the engine3preferably is a V8 engine (eight-cylinder V engine).

The first bank21includes the first cylinder C1, the third cylinder C3, the fifth cylinder C5, and the seventh cylinder C7. The first cylinder C1, the third cylinder C3, the fifth cylinder C5, and the seventh cylinder C7are disposed in this order in the first bank21. The second bank22includes the second cylinder C2, the fourth cylinder C4, the sixth cylinder C6, and the eighth cylinder C8. The second cylinder C2, the fourth cylinder C4, the sixth cylinder C6and the eighth cylinder C8are disposed in this order in the second bank22.

Firing is conducted in these eight cylinders C1to C8at intervals respectively corresponding to a crank angle of 90 degrees. Therefore, the crankshaft11is preferably a cross-plane crankshaft shown inFIG. 4, and four crankpins111to114are disposed at 90 degrees apart from each other.

As shown inFIG. 2, each of the cylinders C1to C8includes a combustion chamber23, an intake port24, and an exhaust port25. The intake port24and the exhaust port25are connected to the combustion chamber23. The intake port24is opened and closed by an intake valve18. The exhaust port25is opened and closed by an exhaust valve19.

As shown inFIG. 3, the engine3includes an exhaust pathway26. The exhaust pathway26includes a first aggregated portion27and a second aggregated portion28. The first aggregated portion27is connected to the exhaust ports25of the four cylinders C1, C3, C5, and C7of the first bank21. The first aggregated portion27causes exhaust gases from the four cylinders C1, C3, C5, and C7of the first bank21to be joined therein. The second aggregated portion28is connected to the exhaust ports25of the four cylinders C2, C4, C6, and C8of the second bank22. The second aggregated portion28causes exhaust gases from the four cylinders C2, C4, C6, and C8of the second bank22to be joined therein. The first aggregated portion27and the second aggregated portion28are disposed between the first bank21and the second bank22.

The exhaust pathway26includes a third aggregated portion29. The third aggregated portion29is connected to the first aggregated portion27and the second aggregated portion28. The third aggregated portion29causes the first aggregated portion27and the second aggregated portion28to be joined. The third aggregated portion29is disposed between the first bank21and the second bank22. A catalyst31is disposed within the third aggregated portion29. The catalyst31purifies exhaust gas passing through the exhaust pathway26.

Next, a fuel supply system of the engine3will be explained.FIG. 5is a schematic diagram of the fuel supply system of the engine3. As shown inFIG. 5, the engine3includes a plurality of fuel injectors41to48, a fuel supply pipe32, and a fuel pump33.

The fuel injectors41to48are respectively mounted to the cylinders C1to C8. The fuel injectors41to48directly inject fuel into the combustion chambers23of the cylinders C1to C8, respectively. In other words, the engine3is of a direct fuel injection type. The fuel injectors41to48include first to eighth fuel injectors41to48. The first to eighth fuel injectors41to48are respectively mounted to the first to eighth cylinders C1to C8.

The fuel supply pipe32supplies fuel to the first to eighth fuel injectors41to48. The fuel supply pipe32includes a first supply pipe34and a second supply pipe35. The first supply pipe34is connected to the four cylinders C1, C3, C5, and C7of the first bank21, whereas the second supply pipe35is connected to the four cylinders C2, C4, C6, and C8of the second bank22. The first supply pipe34and the second supply pipe35are disposed between the first bank21and the second bank22.

The first supply pipe34and the second supply pipe35are not connected to each other. This construction enhances the flexibility in the positional arrangement of the first supply pipe34and the second supply pipe35. For example, when the first supply pipe34and the second supply pipe35are disposed apart from each other, the third aggregated portion29containing the catalyst31is able to be disposed therebetween.

The fuel supply pump33supplies fuel to the fuel supply pipe32. The fuel supply pump33includes a first pump36connected to the first supply pipe34and a second pump37connected to the second supply pipe35. The first pump36increases the pressure of the fuel and discharges the pressure-increased fuel to the first supply pipe34. The second pump37increases the pressure of the fuel and discharges the pressure-increased fuel to the second supply pipe35. Thus, compared to a construction including only one pump, the construction including two pumps enables a reduction in size of the respective pumps36and37.

The first pump36and the second pump37are connected to a fuel tank (not shown in the drawings) through a vapor separator tank38and a fuel filter39. Fuel in the fuel tank is sucked into the first pump36and the second pump37through the fuel filter39and the vapor separator tank38. The fuel sucked into the first pump36is increased in pressure by the first pump36, and is then supplied to the first supply pipe34. The fuel sucked into the second pump37is increased in pressure by the second pump37, and is then supplied to the second supply pipe35.

The first pump36and the second pump37are return-less pumps. In other words, all of the fuel discharged from the first pump36is supplied to the first supply pipe34. All of the fuel discharged from the second pump37is supplied to the second supply pipe35. The amount of work to discharge a necessary amount of fuel is only required to be done by each of the first and second pumps36and37because these pumps are return-less pumps. Hence, this enhances the engine efficiency.

Next, a construction of the fuel supply pump33will be explained.FIG. 6is a schematic diagram of a construction of the first pump36. The first pump36includes a pump body51, a plunger52, an electromagnetic valve53, a one-way valve54, and a cam55. The pump body51includes a suction port56, a pressurizing chamber57, and a discharge port58.

When driven by the cam55, the plunger52varies the pressure of the fuel within the pressurizing chamber57. The electromagnetic valve53opens and closes a pathway between the suction port56and the pressurizing chamber57. When drive current is inputted to the electromagnetic valve53, the electromagnetic valve53closes the pathway between the suction port56and the pressurizing chamber57. The one-way valve54allows the fuel to flow out therethrough in a direction from the pressurizing chamber57to the discharge port58. The one-way valve54prevents the fuel from flowing in a direction from the discharge port58to the pressurizing chamber57.

The cam55includes a plurality of cam lobes59to drive the plunger52. The cam lobes59are circumferentially disposed at even intervals. When pressed by any of the cam lobes59, the plunger52is moved to a pressurizing position (seeFIG. 7C). When the plunger52is moved to the pressurizing position, the fuel within the pressurizing chamber57is compressed. Accordingly, the fuel is increased in pressure. When not being pressed by any of the cam lobes59, the plunger52is moved to a standby position by the elastic force of an elastic member60(seeFIG. 7A).

The number of the cam lobes59is preferably the same as the number of the fuel injectors41,43,45, and47connected to the first pump36. Therefore, in the present preferred embodiment, the number of the cam lobes59preferably is four, and the four cam lobes59are disposed at angular intervals of 90 degrees, for example. It should be noted that the number of the cam lobes59is not limited to four. In other words, the number of the cam lobes59may be different from the number of the fuel injectors41,43,45, and47connected to the first pump36.

The cam55is connected to the crankshaft11through a transmission mechanism (not shown in the drawings), and is rotationally driven by the rotation of the crankshaft11. Therefore, the rotational speed of the cam55varies in accordance with the engine rotational speed.

Next, a series of motions of the first pump36will be explained. InFIG. 7A, the plunger52is not being pressed by any of the cam lobes59, and is moved from the pressurizing position to the standby position. Additionally, in this condition, drive current is not inputted to the electromagnetic valve53. Therefore, the electromagnetic valve53is opened by a difference in pressure between the fuel flowing in through the suction port56and the fuel existing within the pressurizing chamber57, and the fuel flows into the pressurizing chamber57.

Next, as shown inFIG. 7B, when drive current is inputted to the electromagnetic valve53, the electromagnetic valve53closes the pathway between the suction port56and the pressurizing chamber57. Then, as shown inFIG. 7C, any of the cam lobes59presses the plunger52, and the plunger52is moved to the pressurizing position. Accordingly, the fuel within the pressurizing chamber57is compressed by the plunger52, and is thus increased in pressure. When increased in pressure to a predetermined level, the fuel is discharged from the first pump36through the one-way valve54and the discharge port58, and is supplied to the first supply pipe34.

The construction of the second pump37is preferably similar to that of the first pump36, and hence, a detailed explanation thereof will not be hereinafter explained.

Next, a control of the engine3will be explained. As shown inFIG. 5, the engine3includes a controller61. The controller61is configured or programmed to control timings of injecting fuel by the fuel injectors41to48and timings of driving the fuel supply pump33. When described in detail, the controller61includes an ECU (Engine Control Unit)62, a first EDU (Electric Driver Unit)63, and a second EDU64.

The first EDU63and the second EDU64output drive current to the fuel injectors41to48of the respective cylinders C1to C8. The ECU62outputs drive timing signals for the fuel injectors41to48to the first EDU63and the second EDU64. When receiving the drive timing signals from the ECU62, the first EDU63and the second EDU64output a drive current to the fuel injectors41to48. Accordingly, the timings of injecting fuel by the fuel injectors41to48are controlled.

FIG. 8is a timing chart of drive timing signals (INJ drive pulses) for the fuel injectors41to48to be outputted from the ECU62. The fuel injectors41to48inject fuel in accordance with timings of firing in the respective cylinders C1to C8. Therefore,FIG. 8shows the timings of firing in the respective cylinders C1to C8.

As shown inFIG. 8, in the present preferred embodiment, firing in the engine3is conducted sequentially in the first cylinder C1, the eighth cylinder C8, the fourth cylinder C4, the third cylinder C3, the sixth cylinder C6, the fifth cylinder C5, the seventh cylinder C7, and then the second cylinder C2.

Therefore, in the first bank21, firing is conducted in the first cylinder C1and the third cylinder C3at an interval corresponding to a crank angle of 270 degrees. Firing is conducted in the third cylinder C3and the fifth cylinder C5at an interval corresponding to a crank angle of 180 degrees. Firing is conducted in the fifth cylinder C5and the seventh cylinder C7at an interval corresponding to a crank angle of 90 degrees. Firing is conducted in the seventh cylinder C7and the first cylinder C1at an interval corresponding to a crank angle of 180 degrees. Thus, in the first bank21, when firing in the first cylinder C1is considered as a reference, firing is conducted sequentially in the four cylinders C1, C3, C5, and then C7at uneven intervals, i.e., at intervals corresponding to crank angles of 270 degrees, 180 degrees, 90 degrees, and 180 degrees.

In the second bank22, firing is conducted in the sixth cylinder C6and the second cylinder C2at an interval corresponding to a crank angle of 270 degrees. Firing is conducted in the second cylinder C2and the eighth cylinder C8at an interval corresponding to a crank angle of 180 degrees. Firing is conducted in the eighth cylinder C8and the fourth cylinder C4at an interval corresponding to a crank angle of 90 degrees. Firing is conducted in the fourth cylinder C4and the sixth cylinder C6at an interval corresponding to a crank angle of 180 degrees. Thus, in the second bank22, when firing in the sixth cylinder C6is considered as a reference, firing is sequentially conducted in the four cylinders C6, C2, C8, and then C4at uneven intervals, i.e., at intervals corresponding to crank angles of 270 degrees, 180 degrees, 90 degrees, and 180 degrees.

It should be noted that, as shown inFIG. 5, the first EDU63outputs a drive current to the fuel injectors41,44,46, and47of the first, fourth, sixth, and seventh cylinders C1, C4, C6, and C7. Accordingly, in the firing order, the first EDU63constantly outputs a drive current at intervals respectively corresponding to a crank angle of 180 degrees. On the other hand, the second EDU64outputs a drive current to the fuel injectors42,43,45, and48of the second, third, fifth, and eighth cylinders C2, C3, C5, and C8. Accordingly, in the firing order, the second EDU64constantly outputs a drive current at intervals respectively corresponding to a crank angle of 180 degrees.

Next, a control of timings of driving the fuel supply pump33will be explained. The first EDU63outputs a drive current to the electromagnetic valve53of the first pump36. The second EDU64outputs a drive current to an electromagnetic valve of the second pump37. The ECU62outputs drive timing signals for the fuel supply pump33to the first EDU63and the second EDU64. When receiving the drive timing signal for the fuel supply pump33from the ECU62, the first EDU63outputs a drive current to the electromagnetic valve53of the first pump36. Accordingly, the timing of discharging fuel from the first pump36is controlled. When receiving the drive timing signal for the fuel supply pump33from the ECU62, the second EDU64outputs a drive current to the electromagnetic valve of the second pump37. Accordingly, the timing of discharging fuel from the second pump37is controlled.

FIG. 9is a timing chart showing the drive timing signal (INJ drive pulses) for the fuel injectors41,43,45, and47of the first bank21to be outputted from the ECU62, a drive timing signal (pump drive pulses) outputted to the first pump36, a cam profile, and the variation in fuel pressure. The cam profile corresponds to the position of the plunger52, and shows the suction state and the pressurized state of the first pump36. The fuel pressure is the pressure of fuel in the first supply pipe34. The fuel pressure is obtained based on the value of an output from a pressure sensor mounted to the first supply pipe34.

InFIG. 9, Si1, Si3, Si5, and Si7indicate pulses of a drive timing signal for the fuel injectors41,43,45, and47in the present preferred embodiment. The first fuel injector41of the first cylinder C1is driven by the pulse Si1of the drive timing signal. The third fuel injector43of the third cylinder C3is driven by the pulse Si3of the drive timing signal. The fifth fuel injector45of the fifth cylinder C5is driven by the pulse Si5of the drive timing signal. The seventh fuel injector47of the seventh cylinder C7is driven by the pulse Si7of the drive timing signal.

InFIG. 9, on the other hand, Sp1, Sp2, Sp3, and Sp4indicate pulses of a drive timing signal for the first pump36in the present preferred embodiment. In other words, the electromagnetic valve53is closed at a point of time that each pulse Sp1, Sp2, Sp3, Sp4is outputted. Sp2′ and Sp3′ indicate pulses of a drive timing signal for the first pump36in a comparative example. In the comparative example, the pulses Sp1, Sp2′, Sp3′, and Sp4of the drive timing signal are outputted at even intervals respectively corresponding to a crank angle of 180 degrees.

For example, the electromagnetic valve53of the first pump36is closed in conjunction with the output of the pulse Sp1of the drive timing signal for the first pump36. Accordingly, pressurized fuel is discharged from the first pump36. At this time, fuel is injected from the first fuel injector41of the first cylinder C1in response to the pulse Si1of the drive timing signal for the first fuel injector41. Subsequently, when the plunger52is moved toward the standby position (suction state inFIG. 9), negative pressure is produced within the pressurizing chamber57. Accordingly, the electromagnetic valve53is moved in a valve opening direction.

It should be noted that, as shown inFIG. 9, the pulses Si1, Si3, Si5, and Si7of the drive timing signal for the fuel injectors41,43,45, and47are outputted at uneven intervals. Therefore, at a point of time that the pulse Sp2′ of the drive timing signal for the first pump36according to the comparative example is outputted, the pulse Si3of the drive timing signal for the third fuel injector43of the third cylinder C3is not outputted. In other words, despite that the first pump36is in a pressurized state and the electromagnetic valve53of the first pump36remains closed, fuel injection is not conducted in the third cylinder C3. This results in a large spike of the fuel pressure in the first supply pipe34as shown inFIG. 9with Pf1′. Therefore, the fuel pressure in the first supply pipe34is high when the pulse Si3of the drive timing signal for the third fuel injector43of the third cylinder C3is outputted. Because of this, the fuel injection pressure in the third cylinder C3inevitably becomes higher than that in the first cylinder C1.

Likewise, at a point of time that the pulse Sp3′ of the drive timing signal for the first pump36according to the comparative example is outputted, the pulse Si5of the drive timing signal for the fifth fuel injector45of the fifth cylinder C5is not outputted. In other words, despite that the first pump36is in the pressurized state and the electromagnetic valve53of the first pump36remains closed, fuel injection is not conducted in the fifth cylinder C5. This results in a large spike of the fuel pressure in the first supply pipe34as shown inFIG. 9with Pf2′. Therefore, the fuel pressure in the first supply pipe34is high when the pulse Si5of the drive timing signal for the fifth fuel injector45of the fifth cylinder C5is outputted. Because of this, the fuel injection pressure in the fifth cylinder C5inevitably becomes higher than that in the first cylinder C1.

By contrast, in the present preferred embodiment, the pulse Sp2of the drive timing signal for the first pump36is retarded compared to the pulse Sp2′ of the drive timing signal for the first pump36according to the comparative example. Put differently, in the comparative example, a point of time that the pulse SP2′ of the drive timing signal for the first pump36is generated is approximately matched with a point of time that the cam lift amount is minimized, whereas in the present preferred embodiment, a point of time that the pulse Sp2of the drive timing signal for the first pump36is generated is retarded relative to the point of time that the cam lift amount is minimized. In other words, the interval of generating the pulses Sp1and Sp2of the drive timing signal for the first pump36is set longer than the interval of the points of time that the cam lift amount is minimized.

Accordingly, in the present preferred embodiment, the timing of closing the electromagnetic valve53is delayed. Hence, as shown inFIG. 9with Ov1, an overlap occurs between a time period that the first pump36is in the pressurized state and a time period that the electromagnetic valve53of the first pump36remains opened. Therefore, a portion of the fuel existing in the pressurizing chamber57returns to the suction port56, and accordingly, the discharge amount of fuel from the first pump36is reduced.

Thus, in the present preferred embodiment, the discharge amount of fuel from the first pump36is controlled by controlling the timing of closing the electromagnetic valve53of the first pump36. Accordingly, an increase in fuel pressure is inhibited as shown inFIG. 9with Pf1, and the fuel injection pressure in the third cylinder C3is inhibited from becoming higher than that in the first cylinder C1.

Likewise, in the present preferred embodiment, the pulse Sp3of the drive timing signal for the first pump36is retarded compared to the drive timing signal Sp3′ for the first pump36according to the comparative example. Hence, the timing of closing the electromagnetic valve53is retarded, and as shown inFIG. 9with Ov2, an overlap occurs between a time period that the first pump36is in the pressurized state and a time period that the electromagnetic valve53of the first pump36remains opened. Accordingly, the discharge amount of fuel from the first pump36is reduced, and thus, an increase in fuel pressure is inhibited as shown inFIG. 9with Pf2. As a result, the fuel injection pressure in the fifth cylinder C5is inhibited from becoming higher than that in the first cylinder C1.

As described above, in the multi-cylinder engine3according to the present preferred embodiment, the pulse Sp2of the drive timing signal for the first pump36is retarded in the firing interval (between Si1and Si3) corresponding to a crank angle of 270 degrees. Additionally, the pulse Sp3of the drive timing signal for the first pump36is retarded in the firing interval (between Si3and Si5) corresponding to a crank angle of 180 degrees. Thus, an increase in fuel injection pressure is inhibited in the firing intervals corresponding to crank angles of 270 degrees and 180 degrees, in which a large spike of the fuel pressure is likely to occur. Accordingly, it is possible to reduce a difference in fuel pressure among the cylinders, which is attributed to firing being conducted at uneven intervals.

It should be noted that in the above description, control of the first pump36and the fuel injectors41,43,45, and47of the first bank21has been explained. However, the second pump37and the fuel injectors42,44,46, and48of the second bank22may be similarly controlled. Specifically, a pulse of a drive timing signal for the second pump37may be retarded in the firing interval corresponding to a crank angle of 270 degrees (interval between firing in the sixth cylinder C6and that in the second cylinder C2). Additionally, a pulse of the drive timing signal for the second pump37may be retarded in the firing interval corresponding to a crank angle of 180 degrees (interval between firing in the second cylinder C2and that in the eighth cylinder C8).

Preferred embodiments of the present invention have been explained above. However, the present invention is not limited to the above-described preferred embodiments, and a variety of changes may be made without departing from the scope of the present invention.

The engine3is not limited to a V8 engine. The engine3may be an inline engine, a horizontally opposed cylinder engine or so forth. The number of cylinders of the engine3may be seven or less, or alternatively, may be nine or more. The sequential order and the intervals of firing in cylinders are not limited to the above and may be changed.

Any method other than the method of retarding pulses of a drive timing signal may be used for overlapping the time period that the plunger52increases the pressure in the pressurizing chamber57and the time period that the electromagnetic valve53remains opened.

The time period that the plunger52increases the pressure in the pressurizing chamber57and the time period that the electromagnetic valve53remains opened may not be necessarily overlapped in the above firing intervals corresponding to crank angles of 270 degrees and 180 degrees, and may be overlapped in other firing intervals.

The controller61may be configured or programmed to change the time period that the electromagnetic valve53remains opened in accordance with the engine rotational speed. In other words, the controller61may be configured or programmed to change the retard amount of a pulse of the drive timing signal for the first pump36in accordance with the rotational speed of the engine3. For example, the controller61may be configured or programmed to increase the retard amount with increase in rotational speed of the engine3. The controller61may be configured or programmed to store information such as a map defining a relationship between the retard amount and the rotational speed of the engine3. The controller61may be configured or programmed to determine the retard amount of a pulse of the drive timing signal based on this information.

Alternatively, the controller61may be configured or programmed to change the retard amount of a pulse of the drive timing signal for the first pump36in accordance with the fuel pressure. For example, the controller61may be configured or programmed to increase the retard amount with increase in fuel pressure. The controller61may be configured or programmed to store information such as a map defining a relationship between the retard amount and the fuel pressure. The controller61may be configured or programmed to determine the retard amount of a pulse of the drive timing signal based on this information.