JPH11101168A - Common rail fuel injection system for multi-cylinder engine - Google Patents

Abstract

(57) [Summary] [PROBLEMS] During one cycle of fuel injection from injectors of all cylinders, during a single pressure-feeding stroke by a fuel pump, 2
By performing the fuel injection twice, it becomes possible to use a fuel pump having a smaller number of pumping strokes than the number of fuel injections. SOLUTION: In a V-type 8-cylinder engine, a group of four cylinders (an odd group of # 1 to # 7,
2 to # 8) are arranged, and the fuel injection (T
f1 to Tf8) are performed at regular intervals of 90 °, but the fuel injection for each bank is performed at irregular intervals including the intervals of 90 ° and 270 °. For each bank, the number of three pumping strokes (for example, T1a to T3a) by the fuel pump corresponds to four fuel injections (Tf2, Tf8, Tf4, Tf4).
6), but 2 in the pumping stroke T2a.
By performing the fuel injection (Tf8, Tf4) twice, all the fuel injections are performed during the pumping stroke.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-cylinder
The present invention relates to a common rail fuel injection system for a type 8 cylinder engine.

[0002]

2. Description of the Related Art Conventionally, for example, with respect to fuel injection control of an engine, a method for increasing the injection pressure and optimally controlling injection conditions such as fuel injection timing and injection amount according to the operating state of the engine has been proposed. A common rail type fuel injection system is known. The fuel injection system
This is a fuel injection system in which fuel pressurized to a predetermined pressure by a pump is stored in a common rail, and the fuel stored in the common rail is injected from an injector into a corresponding combustion chamber. A controller is provided for each injector in the common rail and the fuel pressure according to the operating condition of the engine so that the pressurized fuel is injected in each injector under the optimum injection condition for the operating condition of the engine. The operation of the control valve is controlled. As described above, the common rail injection system has been developed as an injection system capable of controlling the injection pressure in addition to the injection amount and the injection timing in accordance with the operation state of the engine (for example, Japanese Patent Application Laid-Open No. 3-185261). Gazette, JP-A-4-272472).

A conventional common rail type fuel injection system will be described with reference to FIG. FIG. 6 shows a common rail fuel injection system for a four-cylinder engine.
Fuel supply to the plurality of injectors 1 is performed on the common rail 2
Is supplied through a branch pipe 3 constituting a part of the fuel flow path. The fuel sucked up from the fuel tank 4 via the filter 5 by the feed pump 6 and pressurized to a predetermined suction pressure is sent to the fuel pump 8 through the fuel pipe 7. The fuel pump 8 is driven by, for example, an engine to increase the pressure of the fuel to a high pressure determined based on an operation state and the like, and supplies the fuel to the common rail 2 through a fuel pipe 9.
It is a fuel supply pump for plunger type supply. The supplied fuel is stored in the common rail 2 in a state where the pressure is raised to a predetermined pressure, and is supplied from the common rail 2 to each injector 1. A plurality of injectors 1 are provided according to the type of engine (the number of cylinders, in this case, four cylinders).
Is injected into the corresponding combustion chamber at the optimal injection timing with the optimal fuel injection amount. Since the injection pressure of the fuel injected from the injector 1 is substantially equal to the pressure of the fuel stored in the common rail 2, the pressure in the common rail 2 is controlled to control the injection pressure.

[0004] Of the fuel supplied from the branch pipe 3 to the injector 1, the fuel not consumed for injection into the combustion chamber is returned to the fuel tank 4 through the return pipe 11. The controller 12, which is an electronic control unit, includes an engine cylinder discrimination sensor and a crank angle sensor for detecting an engine speed, an accelerator depression amount sensor for detecting an accelerator depression amount, and a water temperature sensor for detecting a coolant temperature. , And signals from various sensors for detecting an operating state of the engine such as an intake pipe pressure sensor for detecting an intake pipe pressure. The controller 12 sets a target fuel injection condition (for example, a target fuel injection timing, a target fuel injection amount, a target common rail pressure) predetermined based on the engine operating state so that the engine output becomes an optimum output according to the operating state. A target fuel injection condition (that is, fuel injection timing and injection amount by the injector 1) is obtained in accordance with a signal indicating a current engine operating state detected by various sensors and stored as a map or a function. Controls the operation of the injector 1 and the common rail pressure so that the fuel injection is performed. The common rail 2 is provided with a pressure sensor 13, and a detection signal of the fuel pressure in the common rail 2 detected by the pressure sensor 13 is sent to the controller 12. Even if the fuel in the common rail 2 is consumed by the injection of the fuel from the injector 1, the controller 12 controls the discharge amount of the fuel pump 8, that is, the fuel pump 8 so that the fuel pressure in the common rail 2 becomes constant. Controls the flow control valve 10 attached to the controller.

As described above, the common rail fuel injection system accumulates the discharge fuel intermittently pumped from the fuel pump 8 in the common rail 2, and sets an appropriate fuel injection timing (fuel injection timing) according to the operation state of the engine. This is a system in which the injector 1 is driven by a fuel injection amount (common rail pressure and fuel injection period) to inject fuel. The common rail pressure is controlled by controlling the flow control valve 10 of the fuel pump 8 in accordance with the fuel injection from the injector 1 to pump the fuel, and by controlling the pumping amount so that the common rail pressure does not decrease. Not only can it be kept constant, but it can also be increased or decreased according to the operating state of the engine. Therefore, it is preferable that the fuel pump 8 also performs one pressure feed for each fuel injection from the injector 1. If the fuel injection is performed twice during the preceding and subsequent pumping strokes, the common rail pressure increases. descend. In such a state, the injection pressure is reduced, and the injection period is lengthened in order to secure a required injection amount, which causes inconveniences such as deterioration of fuel efficiency and increase in smoke in exhaust gas.

[0006] Japanese Patent Application Laid-Open No. Hei 3-185261 describes that
Each cylinder is provided with an injector that opens and closes by a solenoid valve and injects fuel into the cylinder, connects an accumulator between the injector and the fuel supply pump, and removes the entire cylinder from injectors that are not adjacent to each other in injection order. The fuel injection system for a multi-cylinder diesel engine is described, which has an accumulator for each group. In the same group, there are cylinders whose injection order is adjacent. Therefore, the pressure of the accumulator is prevented from continuously decreasing every time the fuel injection is performed, and the recovery time of the pressure of the accumulator is secured.

Japanese Patent Application Laid-Open No. 4-272472 discloses that the fuel pressure in a pressure accumulating means for temporarily storing fuel supplied to a diesel engine in a high pressure state is detected, and the detected pressure is compared with a target pressure. A pressure-accumulating fuel supply method and apparatus for driving and controlling a plurality of fuel pumping means so that a detected pressure becomes a target pressure, wherein it is determined whether or not all of the plurality of fuel pumping means are normally driven; When it is determined that not all the fuel pumping means are operating normally, the target value of the fuel pressure of the accumulator is reduced, and
It is intended to prevent an excessive load from being applied to the other fuel driving means in a normal driving state.

As one of the multi-cylinder engines, there is a V-type multi-cylinder engine as shown in FIGS. The components shown in FIGS. 4 and 5 and shown in FIG. 6 are denoted by the same reference numerals as those used in FIG. 6, and the description thereof will not be repeated. The V-type multi-cylinder engine has a cylinder block 24 and cylinder heads 25 and 26.
Are arranged in a V-shape when viewed from the front.
6 and 3 banks each with three cylinders in the left bank 17
It is a six-cylinder engine. The fuel pump 8 is disposed on the deck surface 30 between the left and right banks 16 and 17, and the common rail 2 is disposed on the deck surface 30 near the left bank 17. A branch pipe 3 extends from the common rail 2 to each injector 1. Note that the fuel pump 8 is
1 driven. The fuel pump 8 is fixed to a flange 32 formed integrally with the left and right banks 16 and 17 by fixing bolts 33. Each operating part of the fuel pump 8 is lubricated by lubricating oil supplied through a lubricating oil system 35 extending from an oil gallery 34.

In a V-type eight-cylinder engine in which one cylinder is added to each of the right bank 16 and the left bank 17 of the V6 cylinder engine, the fuel injection interval in each cylinder is set to be equal (4
As a cycle engine, 9 in crank angle
(0 °), the injection intervals in the banks 16 and 17 become unequal. In other words, referring to the graph shown in FIG. 3 (see also FIG. 1 for only the arrangement order of each cylinder), the first bank (# 1),
The third cylinder (# 3), the fifth cylinder (# 5), and the seventh cylinder (#
7) are arranged in this order, and the second bank (#
2), the fourth cylinder (# 4), the sixth cylinder (# 6), and the eighth cylinder (# 8) are arranged in this order. From the mechanical and thermal viewpoint of the engine, the ignition order is as follows: the first cylinder (# 1) → the second cylinder (# 2) → the seventh cylinder (# 7) → the eighth cylinder
Cylinder (# 8) → fourth cylinder (# 4) → fifth cylinder (# 5) →
Sixth cylinder (# 6) → third cylinder (# 3) → first cylinder (#
They are set in the order of 1). This ignition sequence is, as viewed in the right bank, the first cylinder (# 1) → (at 180 ° intervals)
Seventh cylinder (# 7) → (at an interval of 270 °) Fifth cylinder (# 5) → (at an interval of 180 °) Third cylinder (#
3) → In order of the first cylinder (# 1) (at intervals of 90 °), when viewed from the left bank, the second cylinder (# 2) → (18
Cylinder # 8 (# 8) → (at an interval of 270 °) Cylinder # 4 (# 4) → (at an interval of 180 °) Cylinder (# 6) → (At 90 ° intervals)
The order is the second cylinder (# 2).

[0010]

Therefore, when a common rail type fuel injection system is applied to a V8 type engine, the pumping is performed eight times in two rotations of the crank angle (the pump shaft is reduced to one half and reduced by one half). Ideally, the common rail pressure should not be reduced for each injection. However, if one pumping means (for example, a plunger) performs eight pumping operations per one rotation of the pump shaft, if one cam is used, eight cam ridges are formed on the cam peripheral surface. However, the cam operating mechanism of such a pump is difficult to machine the cam ridge, and the plunger cannot follow the cam hill when the pump shaft rotates at a high speed. Is not feasible.

Therefore, it is conceivable to dispose a pair of pump mechanisms each composed of two plungers and two four-mounting cams in parallel on a common pump shaft with their pump operation phases shifted from each other. However, machining is still extremely difficult even with a four-cam cam, and if the plunger lift (pumping amount) is to be increased, the plunger lift speed becomes too high, causing the plunger to jump on the cam mountain. Causes a jump phenomenon. If the lift speed is suppressed in order to suppress the occurrence of this phenomenon, the lift amount of the plunger decreases, causing a large delay in increasing the pressure of the common rail.

It is also conceivable to combine four pump mechanisms having one plunger and a double cam with their pump operation phases shifted from each other. However, such a structure inevitably increases the size of the fuel pump itself. Difficulty in securing the engine installation pace, deterioration of fuel efficiency due to increased engine weight, number of parts (particularly the number of flow control valves)
However, there is a problem that the cost is increased due to the increase in the number.

On the other hand, when a common rail type fuel injection system is applied to a V-type engine, the fuel pump and the common rail are mounted on both banks 16, 1 as shown in FIGS.
It is considered that a reasonable layout is arranged between the seven. When one common rail 2 is arranged between the V banks 16 and 17, both banks 16 and 17 from the common rail 2 are arranged.
In some cases, the distance to the injectors 1 arranged at a distance is long, and the length of the branch pipe 3 connecting the common rail 2 and each injector 1 may be long. If the length of the branch pipe 3 is increased, the durability of the branch pipe 3 is reduced, and the fuel capacity remaining in the branch pipe 3 at the time of starting the engine becomes a dead volume, so that the startability of the engine is deteriorated. When the distance between the nozzle hole 1 and the pressure sensor 13 provided on the common rail 2 is increased, inconvenience such as a delay in detecting a decrease in the common rail pressure occurs. Further, when the common rail 2 is arranged between the banks 16 and 17, the space between the V banks becomes common rail 2
And the fuel pump 8 occupies almost all of the space, which may make it difficult to dispose other devices.

Therefore, it is conceivable to increase the size of the common rail so that the branch pipe connecting portion of the common rail approaches the bank to shorten the length of the branch pipe connected between the injector and the common rail. An appropriate range for the partial volume is determined according to the specifications of the engine, such as the displacement and the engine speed, and the volume of the pressure accumulating unit cannot be excessively increased beyond this range.
Further, when the outer wall of the common rail is made thicker with the increase in the size of the common rail, the weight of the engine is increased, and the space between the banks is further narrowed.

Next, it is conceivable to shorten the length of the branch pipe by arranging the common rails and the injectors of the banks that are independent of each other on the left and right banks, as described above. In each bank, the injection timing is not necessarily at every 180 °, but includes the case of an interval of 90 ° and 270 °. As described above, since the injection timing is unequal in each bank, it is impossible to match the timing of the pumping and the injection in each bank by using any of the above-described fuel pumps.

[0016]

SUMMARY OF THE INVENTION It is an object of the present invention to utilize the fact that fuel injection is performed at irregular intervals in a common rail type fuel injection system in a multi-cylinder engine. It is an object of the present invention to provide a common rail type fuel injection system for a multi-cylinder engine, which makes it possible to use a fuel pump with a small pumping stroke by appropriately setting the fuel injection timing. In addition, the common rail can be installed independently for each bank, and the common rail and the injector are arranged close to each other, so that the space occupied by the common rail in the engine is made as small as possible, and the cam ridge of the cam driven by the pump shaft is reduced. An object of the present invention is to provide a common rail type fuel injection system in a multi-cylinder engine that can be easily processed and can reliably operate a cam and a plunger.

The present invention has been made in order to solve the above-mentioned object.
It is configured as follows. That is, the present invention provides a common rail fuel injection system in a multi-cylinder engine in which fuel pumped by a fuel pump is stored in a common rail, and fuel supplied from the common rail is injected from injectors provided in a plurality of cylinders into a combustion chamber. In this case, the fuel injection from the injectors of all the cylinders is performed within one cycle, and the fuel pump is performed during the full-pressure pumping stroke. Wherein the number of times of the full-pressure feed stroke in (1) is made smaller than the number of times of the fuel injection performed during the pressure feed stroke within the period, in a common-rail fuel injection system for a multi-cylinder engine.

In the common rail fuel injection system for a multi-cylinder engine, the multi-cylinder engine has a pair of banks arranged in a V-shape and each having a plurality of the cylinders. The injection intervals of the fuel injection performed in a single cycle are equal intervals, but the injection intervals of the fuel injection performed for a plurality of cylinders arranged in each bank are set at unequal intervals in a V-type multi-cylinder engine. is there. In a V-type multi-cylinder engine, the order in which fuel injection is cycled is determined from a mechanical and thermal point of view. For example, fuel injection is performed at regular intervals in all cylinders.
The injection intervals of the fuel injection are set at unequal intervals.

In the common rail fuel injection system for the multi-cylinder engine, the common rail is constituted by a pair of common rail portions arranged close to a pair of banks. Since the pair of common rail portions are close to the pair of banks, respectively.
The length of the branch pipe from each common rail section to the injector provided in the cylinder arranged in the corresponding bank is shortened, the durability of the branch pipe is improved, the startability of the engine is improved, and the common rail pressure is reduced. The detection delay is improved.

In the common rail fuel injection system for the multi-cylinder engine, the pair of common rail portions are connected to each other by a communication pipe. By communicating the pair of common rails with each other by a communication pipe, a deviation in pressure between the two common rails is eliminated, and a pressure sensor for detecting the pressure in the common rail is used.
It only needs one.

[0021] In the common rail fuel injection system for the multi-cylinder engine, the fuel pump has two fuel pumping means whose pump phases for performing the pumping stroke are shifted from each other. Although the pump operation phases of the two fuel pumping means are shifted so that the pumping strokes arrive alternately, the V-type multi-cylinder engine has a cycle in which a plurality of fuel injections from the injectors of all cylinders make one cycle. The pumping process is performed at equal intervals as a whole. By making use of the fact that the injection interval of the fuel injection from the injector of each cylinder for each bank is unequal, two fuel injections are performed in any one of the pumping strokes, so that all the fuel injections are performed in the pumping stroke. Done during.

In the common rail fuel injection system for the multi-cylinder engine, the two fuel pumping means pump fuel to each common rail. That is, each fuel pumping means performs fuel pumping in a form that shares one common rail portion and the injector of each cylinder arranged in the bank corresponding to the common rail portion.

In the common rail fuel injection system for a multi-cylinder engine, each bank is provided with four cylinders, and each fuel pumping means is provided during a period in which fuel injection from injectors of all cylinders makes one cycle. 3 times of the pressure feeding process. That is, regarding each bank, fuel injection is performed at irregular intervals from the injectors of the four cylinders during a period in which the fuel injection from the injectors of all the cylinders makes one cycle, during which the fuel pumping means performs three pumping operations. Perform the process. Since the fuel injections are unequally spaced, it is possible to set a pumping stroke that allows two fuel injections during any one of the pumping strokes even if three pumping strokes are performed at equal intervals. It is possible and all fuel injection can be performed during any pumping stroke, without causing an extreme drop in common rail pressure.

In the common rail fuel injection system of this multi-cylinder engine, the fuel pumping stroke of the fuel pump is performed after the injection of two cylinders that are continuously injected at the same interval and at the same interval in the same bank. The cylinder is set to end within 30 ° of the crank angle from the top dead center of the cylinder to be operated. For a V8 engine, 4
The shortest fuel injection interval is 9 for a cycle engine.
0 °. On the other hand, since each fuel pumping means performs three pumping strokes at regular intervals during a period in which fuel injection from the injectors of all cylinders makes one cycle, the duration of the pumping stroke is 120 ° in crank angle. Therefore, in the pumping stroke in which two fuel injections are performed during one pumping stroke, the crank angle, which is a margin in the pumping stroke, is 30 °, and the pumping stroke in the same bank is continuously injected at the same interval as the same interval. By ending within 30 ° from the top dead center of the cylinder to be injected later of the two cylinders, two fuel injections are surely performed during the pumping stroke.

In the common rail type fuel injection system for the multi-cylinder engine, the common rail type fuel injection system stores a fuel pumped by a fuel pump, and a fuel injection system for injecting fuel supplied from the common rail into a combustion chamber. An injector having a hole formed therein, an operating condition detecting means for detecting an operating condition of the engine, and a response to a current engine operating condition detected by the operating condition detecting device from a predetermined target fuel injection condition based on the engine operating condition. A controller is provided for determining the current target fuel injection condition and injecting fuel supplied from the common rail from injectors provided in a plurality of cylinders into the combustion chamber based on the current target fuel injection condition.

Further, in the common rail fuel injection system for the multi-cylinder engine, the target fuel injection conditions are a basic fuel injection amount, a basic fuel injection timing and a target pressure of the common rail, and the pressure of the common rail is detected by a pressure sensor. The controller controls the fuel pump so that the pressure of the common rail detected by the pressure sensor matches the target pressure of the common rail.

Since the multi-cylinder engine according to the present invention is configured as described above, at least one fuel injection is performed during each pumping stroke of the fuel pump performed during a period in which the fuel injection from the injectors of all cylinders makes one cycle. Although the fuel injection is performed, since the pumping stroke in which two fuel injections are set is included, the number of the total pumping strokes during the cycle in which the fuel injection completes is determined by the fuel injection performed during the pumping stroke in that period. Less than the number of times. Therefore, since the operation of the fuel pump has a longer cycle than the cycle of fuel injection from the injectors of all cylinders, even if the number of cylinders of the engine increases, it is possible to use a fuel pump with a small pumping stroke. The pump can be reliably operated without making the pump difficult to manufacture.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a common rail fuel injection system for a multi-cylinder engine according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a plan view of a multi-cylinder engine used in the present invention, and FIG. 2 is a side view of the multi-cylinder engine shown in FIG. The air-fueled engine shown in FIGS. 1 and 2 has a right bank 16 and a left bank 1
7 is a V-type eight-cylinder engine 15. In this embodiment, the same reference numerals are given to components having the same functions as the components or parts of the multi-cylinder engine shown in FIGS. Is omitted. In the V-type eight-cylinder engine 15, the common rail 2 is a pair of common rail parts, that is,
It is composed of a right common rail 18 for the right bank 16 and a left common rail 19 for the left bank 17, and the common rails 18, 19 on both sides are provided in parallel in the longitudinal direction of each bank. The right common rail 18 and the right common rail 19 may be provided completely separately from each other. In this case, a pressure sensor (not shown in FIGS.
9 required. As shown, when the right common rail 18 and the right common rail 19 are communicated by the communication pipe 20, the pressure sensor can be shared. V type 8
The cylinder engine 15 includes a cylinder block 24 and cylinder heads 25 and 26 in both banks 16 and 17, and the injector 1 corresponding to a cylinder disposed in the cylinder block 24 is sealed in a state where the injector 1 penetrates the cylinder heads 25 and 26. Fixed.

The fuel pump 8 is a plunger pump in which a pair of pump mechanisms as a pair of fuel pumping means provided with a three-lobe cam are arranged in parallel on the same pump shaft. Since the pump shaft is driven at a reduced speed by half with respect to the crankshaft, the pump shaft makes one rotation when the crankshaft makes two rotations. The common rails 18 and 19 on each side are connected to respective pump mechanisms of the fuel pump 8 via fuel pipes 22 and 23, respectively. The pressure of the common rails 18 and 19 on each side is compensated so as not to be reduced by the fuel pumped from the fuel pump 8 through the fuel pipes 22 and 23, respectively. Although not shown in detail, each pump mechanism is arranged in parallel with a common pump shaft so that the pump operation is reversed. That is, the cam ridges or plungers are arranged out of phase about the common pump shaft so that the pumping strokes of the fuel by the respective pump mechanisms arrive alternately.

The right common rail 18 and the left common rail 19 are arranged along and close to the right bank 16 and the left bank 17, respectively. Therefore, the branch pipe 3 extending from the right common rail 18 and the left common rail 19 to the injector 1 provided in each cylinder.
Is shorter than the branch pipe of a conventional multi-cylinder engine. As a result, the durability of the branch pipe 3 is improved,
When the engine is started, the fuel capacity remaining as a dead volume in the branch pipe 3 is reduced, so that the startability of the engine is improved, and the distance between the injection hole of the injector 1 and the pressure sensor 13 provided on the common rail 2 is also reduced. As a result, there is no delay in detecting a decrease in the common rail pressure. Further, since the common rails 18 and 19 and the V-banks are arranged on the sides, the space between the banks 16 and 17 is reduced by the common rails 18 and 19 and the fuel pump 8.
In addition, other devices such as an intake / exhaust system of the engine such as the turbocharger 21 and a valve operating mechanism can be provided.

FIG. 3 shows one cycle of the V-type eight-cylinder engine shown in FIG. 1 and FIG.
FIG. 10 is a graph showing the fuel injection timing from the injector and the operating state of the fuel pump in each cylinder with respect to (20 °). The horizontal axis is the rotation angle of the crankshaft,
The vertical axis is the stroke of the plunger of the fuel pump 8.
The lower graph in FIG. 3 is a graph for the right bank 16, and the upper graph is a graph for the left bank 17. Looking at the graph for the left bank 17 shown above, in the second cylinder (# 2), the crank angle 9
Fuel is injected from the injector corresponding to the timing of 0 °, and thereafter, the crank angles are 270 °, 360 °, and 540 °.
°, the eighth cylinder (# 8) and the fourth cylinder
Fuel injection is performed in the order of the cylinder (# 4) and the sixth cylinder (# 6). The operation of the pump mechanism for the left bank 17 of the fuel pump 8 can take an operation between an operation A indicated by a dotted line and an operation B indicated by a solid line which are separated by a width of about 30 °. . Since the pump mechanism operates with a three-mount cam,
In the operation A and the operation B, the pump mechanism is in the pumping period in the upwardly sloping operation state which continues over the range of 120 ° in the crank angle, and the pump mechanism is in the pumping period in the downwardly sloping operation state which also continues over the range of 120 ° in the crank angle. It is in the suction period.

In the second cylinder (# 2), during the fuel injection period Tf2 performed corresponding to the crank angle of 90 °, in both the operation A and the operation B, the pump mechanism operates in the first pumping period (operation A and the operation T1a, T for B
1b), it is possible to prevent a decrease in the pressure of the common rail 19 due to the fuel injection. Next, the crank angle 27
The eighth cylinder (# 8) and the fourth cylinder (# 4), in which fuel injection is performed corresponding to 0 ° and 360 °, have the same minimum interval (crank angle) as the injection (ignition) interval when viewed as a whole cylinder. At 9
0 °), fuel injection is performed. The fuel injection period Tf8 for the eighth cylinder (# 8) is the second pumping period of the pump mechanism (T2a and T2b for operation A and operation B, respectively).
And the fuel injection period Tf4 for the fourth cylinder (# 4) is at the end of the second pumping period (T2a and T2b for the operation A and the operation B, respectively) of the pump mechanism. The pressure drop of the common rail 19 can be prevented. The reason that there is a width of 30 ° in the range of the crank angle between the operation A and the operation B is as follows.
This is due to the difference between the minimum interval (90 ° in crank angle) and the pumping period of the pump mechanism (120 ° in crank angle). Next, for the sixth cylinder (# 6), a fuel injection period Tf6 corresponding to the crank angle of 540 ° is performed.
The pump mechanism operates during the third pumping period (T for operation A and operation B, respectively) in both operation A and operation B.
3a, T3b), common rail 1 associated with fuel injection
9 can be prevented from dropping. It should be noted that the operation A and the operation B are better operations in the operation A indicated by the dotted line.

For the right bank 16, the first cylinder (#
1), fuel injection timings Tf1, Tf7, Tf in the seventh cylinder (# 7), the fifth cylinder (# 5), and the third cylinder (# 3)
5, Tf3 and the pumping periods T1c, T1d of the pump mechanism;
The correspondence with T2c, T2d; T3c, T3d is the same as described above for the left bank, and the fuel injection timing can be made to correspond to the pumping period of the pump mechanism. The details of the correspondence are the same as those described above for the left bank, and a description thereof will not be repeated. The operation A
And the operation B correspond to the operation A and the operation B for the left bank.

As described above, since there are four cylinders provided in each of the right and left banks, it is normally necessary to perform fuel pumping four times before the combustion cycle of all cylinders ends. According to the above embodiment according to the present invention, it is possible to perform the fuel pumping three times by utilizing the fact that the fuel injection timings of the four cylinders in each bank are not at equal intervals of 180 °. As a result, the relationship between the fuel pump pumping and the fuel injection from the injector is infinitely "one injection per pumping".
And the operation of the fuel pump provided for each bank is longer than the cycle of fuel injection from the injector of the cylinder, that is, the fuel pump is operated slowly. It can be used, and since the cam for operating the plunger of each pump mechanism of the fuel pump can be a three-mount cam, not only can the cam be processed, but also the followability of the plunger to the cam peak can be ensured. The operation of the fuel pump can be ensured.

[0035]

Since the present invention is configured as described above, it has the following effects. That is, in the common rail type fuel injection system for the multi-cylinder engine according to the present invention, during the full-pressure feeding stroke of the fuel pump performed during the period in which the fuel injection from the injectors of all the cylinders makes one cycle,
Since the pumping stroke in which two fuel injections are set is included, the number of full pumping strokes during the cycle of the fuel injection should be smaller than the number of fuel injections performed during the pumping stroke during the period. Can be. Therefore, since the operation of the fuel pump has a longer cycle than the cycle of fuel injection from the injectors of all cylinders, a fuel pump with a small number of times of pumping can be used even if the number of cylinders of the engine increases. In addition, there is no need to use a cam that is difficult to machine as a cam for operating the pump, particularly for operating the plunger, and the plunger jumping phenomenon does not occur in the operation of the plunger and the cam, so that the plunger can follow the cam. A reliable pump operation can be performed. In addition, since the common rail can be divided and attached to the engine in a state of being juxtaposed to each bank, the branch pipe is shortened, the starting characteristics are improved, and the delay in pressure detection is improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a multi-cylinder engine used in a common rail fuel injection system in a multi-cylinder engine according to the present invention.

FIG. 2 is a front view of the multi-cylinder engine shown in FIG.

FIG. 3 is a graph showing the relationship between the fuel injection timing of a common rail fuel injection system and the operation of a fuel pump in a multi-cylinder engine according to the present invention.

FIG. 4 is a plan view showing an example of a conventional multi-cylinder engine.

FIG. 5 is a front view of the multi-cylinder engine shown in FIG.

FIG. 6 is a schematic diagram of a common rail fuel injection system in a multi-cylinder engine.

[Explanation of symbols]

 Reference Signs List 1 injector 2 common rail 8 fuel pump 10 fuel control valve 12 controller 13 pressure sensor 15 multi-cylinder engine 16 right bank 17 left bank 18 right common rail 19 left common rail 20 communication pipe 21 turbocharger 22, 23 fuel pipe

Claims (10)

[Claims] 1. A common rail type fuel injection system for a multi-cylinder engine, in which fuel pumped by a fuel pump is stored in a common rail and fuel supplied from the common rail is injected into a combustion chamber from injectors provided in a plurality of cylinders. , By including the pumping stroke in which the fuel injection is set twice during the full pumping stroke of the fuel pump performed during the period in which the fuel injection from the injectors of all the cylinders makes one cycle, A common rail type fuel injection system for a multi-cylinder engine, wherein the number of times of the full pressure feeding stroke is smaller than the number of times of the fuel injection performed during the pressure feeding stroke within the period. 2. The multi-cylinder engine has a pair of banks arranged in a V-shape and each having a plurality of cylinders, and the fuel injection is performed in a cycle from the injectors of all the cylinders. 2. The V-type multi-cylinder engine according to claim 1, wherein the intervals of the fuel injection performed on the plurality of cylinders arranged in the respective banks are unequal, although the intervals are equal. A common rail type fuel injection system for a multi-cylinder engine according to the above. 3. The fuel injection system according to claim 2, wherein the common rail is constituted by a pair of common rail portions arranged close to the pair of banks. system. 4. The communication device according to claim 3, wherein said pair of common rail portions are connected to each other by a communication pipe.
A common rail type fuel injection system for a multi-cylinder engine according to the above. 5. The fuel pump according to claim 1, wherein the fuel pump has two fuel pumping means whose pump phases for performing the pumping stroke are shifted from each other. Common rail fuel injection system for multi-cylinder engines. 6. The fuel injection system according to claim 5, wherein said two fuel pumping means respectively feed fuel to said common rail sections separately. 7. Each of the banks is provided with four cylinders, and each of the fuel pumping means performs the pumping stroke three times during the period in which fuel injection from the injectors of all the cylinders makes a cycle. 7. The fuel injection system according to claim 6, wherein the fuel injection system is a multi-cylinder engine. 8. The compression stroke of the fuel by the fuel pump is performed at the top dead center of the cylinder that is injected later of the two cylinders that are continuously injected at the same interval in the same bank. The common-rail fuel injection system for a multi-cylinder engine according to claim 7, wherein the fuel injection system is set so as to end within 30 ° of a crank angle from the crank angle. 9. The common rail fuel injection system includes: the common rail for storing fuel pumped by the fuel pump; the injector having an injection hole for injecting fuel supplied from the common rail into the combustion chamber; Operating state detecting means for detecting an operating state of the engine; and a current operating state detecting means which responds to a current engine operating state detected by the operating state detecting means from a target fuel injection condition predetermined based on the engine operating state. A controller for determining a target fuel injection condition and injecting fuel supplied from the common rail from injectors provided in a plurality of cylinders to a combustion chamber based on the current target fuel injection condition. Item 1
A common rail fuel injection system for a multi-cylinder engine according to any one of claims 1 to 8. 10. The target fuel injection condition is a basic fuel injection amount, a basic fuel injection timing, and a target pressure of the common rail. The common rail pressure is detected by a pressure sensor, and the controller detects the common rail pressure by the pressure sensor. The common rail fuel injection system according to claim 9, wherein the fuel pump is controlled so that a common rail pressure matches the target pressure of the common rail.