JP2586566B2 - Fuel injection device - Google Patents

Description

The present invention relates to a fuel injection device having a pressure accumulating pipe used for a diesel engine or the like.

2. Description of the Related Art Conventionally, as a fuel injection device for injecting high-pressure fuel used for a diesel engine or the like, for example, Japanese Unexamined Patent Application Publication No.
A fuel injection device having a pressure accumulation pipe (common rail) as disclosed in JP-165858A has been proposed.

In this fuel injection device, high-pressure fuel is accumulated in a kind of surge tank called a common rail by a high-pressure supply pump, and this fuel pressure is used as control for opening / closing a fuel injection valve and injection pressure.

[Problems to be Solved by the Invention] However, in such conventional devices, generation, maintenance, and control of a common rail pressure equivalent to an injection pressure (100 to 150 MPa) for a diesel engine or the like are the most important technical problems. It is necessary to generate a stable and accurate common rail pressure under a wide range of operating conditions such as a diesel engine. By the fuel injection from the fuel injection valve, the seventh
As shown in FIG. 7A, the injection rate of the fuel injection valve at a certain rotation speed becomes as shown by a broken line, and as the rotation speed increases, the interval between injections becomes narrower as shown by a solid line. Further, the pressure of high-pressure fuel pumped from a high-pressure supply pump driven according to the rotation of the internal combustion engine, for example, driven at 1/2 rotation per rotation of the internal combustion engine, is shown in FIG. 7 (B). As described above, at a certain rotation speed, it becomes as shown by a broken line, and as the rotation speed increases, as shown by a solid line, the pumping period becomes shorter and the pumping interval becomes narrower. At this time, the pressure in the common rail indicates only the pressure change by the high-pressure supply pump and the pressure change by the fuel injection valve. When the fuel is supplied from the high-pressure supply pump as shown in FIG. Is high and decreases when fuel is being injected from the fuel injection valve. However, when the fuel injection from the fuel injection valve ends, a water hammer due to the sudden closing of the fuel injection valve occurs,
The pressure pulsation in the common rail due to the water hammer is as shown in FIG. FIG. 7 (D) shows a case where two fuel injections have been performed. As shown, when the fuel injection valve is closed, a so-called pressure wave due to water hammer is generated. Before the pressure wave attenuates and disappears, a pressure wave is generated due to water hammer when the other fuel injection valve is closed, and overlaps with the pulsation due to the immediately preceding valve closing. The pulsation component of FIG. 7 (D) and FIG. 7 (C)
The pressure waveform in FIG. 7 (E) obtained by superimposing the common rail pressure is the actual common rail pressure. However, the reflected wave of the pipe between the high-pressure supply pump and the common rail usually overlaps this pressure, but this level is small and is omitted.

Here, when the internal combustion engine is operating at a certain rotation speed, each pressure waveform is as shown by a broken line in FIG. 7, but if it becomes faster than this rotation speed, it is shown by a solid line in FIG. It changes like this. That is, the pumping period of the high-pressure supply pump is shortened, and the pumping interval is also shortened. At this time, the injection interval of the fuel injection valve also becomes shorter at the same time.

However, the propagation speed of the pressure wave in the pipe of the fuel supply system is substantially constant if the shape of the pipe or the like of the fuel supply system is determined, and the interval (period) of the reflected waves in the pipe is also constant. Therefore, at a certain rotational speed of the internal combustion engine, the common rail pressure based on the fuel injection from the fuel injection valve and the pumping pressure from the high pressure supply pump shown by the solid line in FIG. 7 (C) and the solid line in FIG. 7 (D) When the phase with the pulsation component due to the water hammer indicated by is superimposed, the pressure fluctuation may be strengthened. That is, as shown by the solid line in FIG. 7 (E), there was a case where the pressure fluctuated greatly and the superimposed pressure fluctuation gradually increased.

Thus, the pressure fluctuation due to fuel injection and fuel pumping,
When the water hammer by the fuel injection valve is superimposed, as shown in FIG. 8, at a certain rotational speed, a pressure wave is superimposed for each fuel injection, the pressure fluctuation gradually increases, and the pressure fluctuation increases. A phenomenon occurs. This phenomenon leads to damage to the high-pressure supply pump itself if the peak of the pressure fluctuation does not exceed the pressure resistance of the high-pressure supply pump, and also changes the fuel pressure injected from the fuel injection valve, and the fuel injection amount changes. However, there is a problem that proper fuel injection may not be performed.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fuel injection device that solves the above-mentioned problem and that prevents the phenomenon of pressure fluctuation from expanding.

Configuration of the Invention [Means for Solving the Problems] In order to achieve the object, the present invention has the following configurations as means for solving the problems. That is, high-pressure fuel supplied from a high-pressure supply pump that pressurizes and feeds fuel by a reciprocating plunger is accumulated in a pressure accumulation pipe, and a fuel injection valve provided for each cylinder of the internal combustion engine via the pressure accumulation pipe The high-pressure supply pump is driven in accordance with the rotation of the internal combustion engine, and the number of discharges per unit rotation according to the cycle of the internal combustion engine is controlled by the internal combustion engine. This is the configuration of the fuel injection device characterized in that the number of cylinders of the engine is a non-integer multiple or a non-integral fraction.

[Operation] In the fuel injection device having the above configuration, the high-pressure supply pump driven in accordance with the rotation of the internal combustion engine is configured such that the number of cylinders of the internal combustion engine is non-integer times or non-integer per unit rotation according to the cycle of the internal combustion engine. The plunger pressurizes and pumps high-pressure fuel into the pressure accumulator pipe at one-half the number of discharges, and fuel injection valves provided for each cylinder of the internal combustion engine inject high-pressure fuel supplied through the pressure accumulator pipe. I do. Therefore, it is possible to prevent an increase in the pressure fluctuation due to the superposition of the water pressure and the pressure fluctuation due to the fuel injection / fuel pumping.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a fuel injection device according to one embodiment of the present invention. As shown, the fuel injection device includes a four-cycle eight-cylinder diesel engine 1 as an internal combustion engine,
Each fuel injection valve 2a-2h for injecting fuel provided for each cylinder 1a-1h of the diesel engine 1, and each fuel injection valve 2a-2h
Pressure-accumulation pipe for accumulating high-pressure fuel to be supplied to the tank, a so-called common rail 4, and pressure feeding of high-pressure fuel to the common rail 4 3
The high pressure supply pumps 6a to 6c and an electronic control unit (hereinafter, simply referred to as an ECU) 8 for controlling them are provided.

The high-pressure supply pumps 6 a to 6 c pressurize the fuel sucked from the fuel tank 10 via the low-pressure supply pump 12 to a high pressure, and then feed the fuel to the common rail 4. These three high pressure supply pumps 6a
1 to 6c have the same structure, and their functions are schematically shown in FIG. 1. One of the high-pressure supply pumps 6a will hereinafter be represented as a high-pressure supply pump 6, and the detailed structure thereof will be described. This will be described with reference to FIGS.

The high-pressure supply pump 6 communicates with a cam chamber 31 provided at the lower end of the pump housing 30, a cylinder 32 fitted to the pump housing 30, and a cylinder 32.
It is composed of an inlet pipe 33 for receiving the high-grade fuel of low pressure from 12, and an electromagnetic valve 34 screwed to the cylinder 32.

A cam shaft 35 that rotates at half the rotational speed of the diesel engine 1 is inserted into the cam chamber 31. The cam shaft 35 has a contour 36x in which each corner of a substantially equilateral triangle is rounded. A cam 36 is provided. Therefore, the camshaft 35 is driven so as to make one rotation per unit rotation according to the cycle of the diesel engine 1, that is, two rotations of the diesel engine 1 ending one cycle. The camshaft 35 has three cams according to the high-pressure supply pumps 6a to 6c.
36a to 36c have their contours 36x to 36z provided with a phase difference of 40 degrees, respectively.

A plunger 37 is reciprocally fitted in the sliding hole 32a of the cylinder 32. The plunger 37 has a cylindrical shape without any leads, and has a plunger.
A pump chamber 38 is formed by 37 and the sliding hole 32a of the cylinder 32. In the cylinder 32, a feed hole 39 communicating with the pump chamber 38 and a communication hole 40 communicating with the pump chamber 38 above the feed hole 39 are formed.
This feed hole 39 is provided between the cylinder 32 and the pump housing.
30 and a fuel reservoir 41 formed between the fuel reservoir 41 and the fuel reservoir 41.
The low pressure fuel from the low pressure supply pump 12 is supplied to the 41 via the introduction pipe 33.

Further, a check valve 42 is provided in the cylinder 32, and the check valve 42 is connected to the pump chamber 38 through a communication hole 40. The check valve 42 is pushed open by the fuel pressurized inside the pump chamber 38 against the combined force of the return spring 44 and the hydraulic pressure of the return valve 44, and the discharge hole 45. It is configured to discharge fuel. The pump chambers 38a to 38c of the high-pressure supply pumps 6a to 6c are connected to the supply pipe 14 through communication holes 40a to 40c, discharge holes 45a to 45c, and check valves 42a to 42c, respectively. This supply pipe 14 is connected to the common rail 4.

The lower part of the plunger 37 is connected to a valve seat 46,
Is pressed against a tappet 48 by a plunger spring 47. A cam roller 49 is rotatably provided on the tappet 48, and the cam roller 49 is pressed against the cam 36 in the cam chamber 31 by the urging force of the plunger spring 47. Therefore, the contour 36 of the cam 36 is
The plunger 37 reciprocates via the cam roller 49 and the valve seat 46 which move up and down in accordance with x. The displacement and speed of the reciprocation of the plunger 37 with respect to the predetermined rotation angle of the cam 36 are determined according to the contour 36x of the cam 36. Therefore, when the plunger 37 reciprocates in the sliding hole 32a of the cylinder 32,
The plunger 37 opens and closes the feed hole 39, and the plunger
When the feed hole 39 is not closed, the low-pressure fuel is supplied to the pump chamber 38 through the feed hole 39.

An electromagnetic valve 34 is screwed to the cylinder 32 so as to face the plunger 37. As shown in FIG. 3, the solenoid valve 34 has a body 51 in which a low-pressure passage 50 having one end opened to the pump chamber 38 is formed, and a spring 53 which is energized by a solenoid 53 when energized through a lead 52. An armature 55 sucked in the direction shown by the arrow A in the figure against the urging force (acting in the direction shown by the arrow B in the figure), and the armature
The low-pressure passage 50 communicates by moving integrally with 55 and separating from a seat 56 formed at the opening to the pump chamber 38.
And a mushroom-shaped valve body 57 that is an externally opened valve that shuts off. The valve body 57 receives the fuel pressure inside the pump chamber 38 as a pressing force in the valve closing direction (the direction indicated by the arrow A in the figure). When the solenoid valve 34 is energized at a predetermined time after the plunger 37 closes the field hole 39, the valve body 57 is seated on the seat portion 56 and the pre-stroke control for setting the pressurization start timing of the plunger 37 is performed. It is a solenoid valve of the type. As shown in FIG. 2, the other end of the low-pressure passage 50 communicates with the above-described fuel reservoir 41 via a gallery 58 and a passage 59.

On the other hand, as shown in FIG.
The number corresponding to the contours 36x to 36z of a to 36c (9 in this embodiment)
) Is fixed, and a cam angle sensor 70 composed of an electromagnetic pickup is provided so as to approach and face the pulse gear 61. Pulse gear 61
A cam angle signal is transmitted to the ECU 8 each time the projection 61a of the. Here, the pulse gear 61
The mounting phase of the projection 61a with respect to the contour of the cam 36 is determined by the rotation of each of the cams 36a to 36c described later.
Corresponds to the phase at which the high pressure fuel is discharged and the cam angle sensor 70 outputs a high-level signal to the ECU 8 at this time.

Further, as a detection system, a rotation speed sensor 71 for detecting a rotation speed of the diesel engine 1 and an accelerator operation amount sensor 72 for detecting an accelerator pedal operation amount corresponding to a load.
And a pressure sensor 73 for detecting a common rail pressure inside the common rail 4.

The ECU 8 is configured as a logical operation circuit centering on the CPU 8a, ROM 8b, and RAM 8c, is connected to the input / output unit 8e via the common bus 8d, and performs input / output with the outside. The detection signals of the above sensors are input from the input / output unit 8e to the CPU 8a.

On the other hand, the CPU 8a controls the fuel injection valve 2 via the input / output unit 8e.
a to 2h and each solenoid valve 34a to 34c of each high-pressure supply pump 6a to 6c
To output a control signal.

Next, the basic operation of the high-pressure supply pump 6 having the above configuration will be described with reference to FIG.

As shown in the figure, when the plunger 37 that reciprocates with the rotation of the camshaft 35 opens the feed hole 39 when descending, fuel is sucked into the pump chamber 38 through the feed hole 39, When the feed hole 39 is closed at the time of ascent, the pressing force is exerted on the fuel sucked into the pump chamber 38. However, at this time, if the solenoid valve 34 is not energized, the valve body 57 of the solenoid valve 34 is open, so the pump chamber
The fuel inside 38 is supplied to low pressure passage 50, gallery 58 and passage
It overflows into the fuel reservoir 41 via the 59 sequentially and is not pressurized.

As described above, when the solenoid valve 34 is energized while the fuel in the pump chamber 38 overflows, the valve body 57 is seated on the seat portion 56 and the low-pressure passage 50 is closed. For this reason, the fuel in the pump chamber 38 starts to be pressurized by the rise of the plunger 37,
When the internal fuel pressure exceeds the combined force of the urging force of the return spring 44 of the discharge valve 42, the pressure of the common rail 4 and the force determined by the pressure receiving area of the valve element 43, the fuel pumped through the discharge hole 40 is discharged. Push open the valve 42 and discharge to the common rail 4
Discharged through 45. Further, for one rotation of the cam shaft 35, the plunger 37 reciprocates three times and discharges three times.

Next, the operation of the fuel injection control device of the present embodiment will be described based on the flowchart shown in FIG. The high-pressure supply pump control process is executed when the ECU 8 is started. First, in step 100, the accelerator operation amount sensor 7
2. Processing for reading the load α, the rotation speed Ne, and the common rail pressure PC detected by the rotation speed sensor 71 and the pressure sensor 73 is performed. In the following step 110, a process of calculating the target common rail pressure PC0 from the load α and the rotational speed Ne read in step 100 using an arithmetic expression or a map is performed. Next, proceeding to step 120, the target common rail pressure PC0 calculated in step 110, the common rail pressure PC read in step 100, the rotation speed N
e, a process of calculating the discharge amount Q of the high-pressure fuel from each of the high-pressure supply pumps 6a to 6c using an arithmetic expression or a map based on the load α. In the following step 130,
The ejection amount Q calculated in the step 120 and the step 1
Processing for calculating the control time TN from the rotational speed Ne read in 00 based on an arithmetic expression or a map is performed. Next, proceeding to step 140, it is determined whether or not a cam angle signal detected by the cam angle sensor 70 has been detected. If the determination is affirmative, the process proceeds to step 150, while if the determination is negative, the cam angle signal is detected. Wait until you repeat the same steps. In step 150, a process for resetting and starting the timer T is performed. Next step 16
In the case of 0, it is determined whether or not the time value of the timer T, which has started the time measurement in the step 150, is equal to or longer than the control time TN calculated in the step 130. When it is determined, the process waits while repeating the same steps until the control time has elapsed. Step 17
At 0, a process of outputting a control signal for closing the solenoid valve 34 is performed. By the process of step 170, pressurization and pressure feed of the fuel are started. In the following step 180, it is determined whether or not a cam angle signal has been detected. If an affirmative determination is made, the process proceeds to step 190, while if a negative determination is made, the process stands by while repeating the same steps until a cam angle signal is detected. In step 190, a process for resetting and starting the timer T is performed. In the following step 200, it is determined whether or not the time value of the timer T, which has started time counting in the step 190, is equal to or longer than a predetermined standby time T0, and if an affirmative determination is made, the process proceeds to step 210; Then, it waits while repeating the same steps until the waiting time T0 elapses. In step 210, the solenoid valve 3
Processing for outputting a control signal for opening valve 4 is performed. By the processing of step 210, the next discharge fuel can be sucked. After executing the step 210, the variable discharge amount high pressure pump control process is temporarily terminated. Thereafter, the variable discharge amount high-pressure pump control process is executed at predetermined time intervals by the aforementioned step.
Repeat steps 100 to 210.

Next, an example of the above control will be described with reference to the timing chart of FIG. As shown by the solid line in FIG.
If the pressurization / pumping start time is early, at time t2 after a short control time T1 has elapsed from the time t1 at which the cam angle signal is detected, a control signal to close the solenoid valve 34 is output, and pressurization / pumping of the fuel is started. Be started. At time t2, since the lift amount S of the plunger 37 is a small value, the pumping stroke amount becomes a large value S1, and the discharge amount Q also becomes large. Eventually, at time t5 after the elapse of standby time TO from time t4 when the next cam angle signal is detected, a control signal for opening solenoid valve 34 is output. On the other hand, as shown by a broken line in the figure, when the pressurization / pressure feed start time is late, at time t3 after a long control time T2 elapses from the time t1 when the cam angle signal is detected, the control signal to close the solenoid valve 34. Is output, and pressurization / pressure feed of the fuel is started. At the time t3, since the lift amount S of the plunger 37 is a large value, the pumping stroke amount becomes a small value S2, and the discharge amount Q also becomes small. Thus, when the time limit TN is shortened, the pumping stroke amount increases, while the control time
Extending TN reduces the pumping stroke. Therefore,
The discharge amount Q can be controlled to a desired value by adjusting the control time TN.

As described above, the discharge amount Q of the high-pressure supply pump 6 is controlled by the solenoid valve 34. This control is executed for each of the solenoid valves 34a to 34c of each of the high-pressure supply pumps 6a to 6c. Therefore, in the present embodiment, as shown in FIG. 6 (B), each of the high-pressure supply pumps 6a to 6c outputs a unit during one rotation of the camshaft 35, that is, a unit corresponding to the cycle of the diesel engine 1. Three discharges are performed during each rotation, and a total of nine discharges are performed at regular intervals if the rotation speed is constant during the unit rotation.

On the other hand, each of the fuel injection valves 2a to 2h is
The fuel injection timing control, the fuel injection amount control, and the like are executed based on the rotation speed, load, and the like, and fuel injection is performed. As a result, as shown in FIG. 6 (A), during one rotation of the camshaft 35, that is, during a unit rotation according to the cycle of the diesel engine 1, the injection interval and the like vary depending on the rotation speed and the like. Are executed once each. In the present embodiment, since the diesel engine 1 has eight cylinders, a total of eight fuel injections equal to the number of cylinders are executed.

Therefore, at a certain rotational speed, the high-pressure fuel supplied from each of the above-described high-pressure supply pumps 6a to 6c and the fuel injection valve 2a
Since the waveforms of the pressure change in the common rail 4 due to the fuel injected from ~ 2h do not coincide with each other,
As shown in FIG. 6 (C). That is, as in the past,
Unlike the pressure waveform close to a sine wave of a certain frequency, as shown in FIG. 7 (C), in which the number of fuel injections during the unit rotation of the diesel engine 1 and the number of discharges from the high-pressure supply pump 6 match. , A complex pressure waveform as if waveforms of many frequencies are superimposed. Therefore, when this complicated pressure waveform and the pressure waveform due to the water hammer component shown in FIG. 6D are superimposed, a pressure waveform having a large swell component, for example, as shown in FIG. There is no overlap and enlargement. That is, as shown in FIG. 6 (D), the pressure waveform due to the water hammer is a pressure waveform that is repeated at a constant cycle when the rotation speed is constant, and the complicated pressure waveform is superimposed thereon. Because.

In the present embodiment, the number of fuel injections, that is, the number of cylinders, is set to 8, and the number of discharges per unit rotation is set to 9 times, which is a non-integer multiple of the number of cylinders. Alternatively, when the number of cylinders is 5, the number of discharges per unit rotation is set to 9 The number of discharges may be six, or when the number of cylinders is ten, the number of discharges may be nine, which is a non-integral fraction smaller than this.

Therefore, according to the fuel injection device of the present embodiment, the number of discharges from the high-pressure supply pump 6 per unit rotation according to the cycle of the diesel engine 1 is a non-integer multiple of the number of cylinders or a fraction of the non-integer. Therefore, the pressure fluctuation due to the fuel supply and the fuel pumping and the water hammer by the fuel injection valve 2 are not superimposed, so that the pressure waveform does not expand, and the expansion phenomenon of the pressure fluctuation is prevented. Further, since the pressure fluctuation does not increase, the pressure fluctuation in the common rail 4 also decreases, and therefore, the fluctuation of the fuel pressure injected from the fuel injection valve 2 also decreases, and the change in the fuel injection amount due to the pressure fluctuation decreases. Fuel injection is also properly performed.

Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments at all, and it goes without saying that the present invention can be implemented in various modes without departing from the gist of the present invention.

Effect of the Invention As described in detail above, in the fuel injection device of the present invention, the number of discharges by the high-pressure supply pump per unit rotation according to the cycle of the internal combustion engine is a non-integer multiple or a non-integer number of cylinders of the internal combustion engine. As a result, the pressure fluctuation due to the fuel supply / fuel feed and the water hammer by the fuel injection valve are superimposed, so that the pressure waveform does not expand, preventing the phenomenon of the pressure fluctuation from expanding and the pressure fluctuation in the pressure accumulating pipe. Is small, and an appropriate fuel injection can be executed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a fuel injection device as one embodiment of the present invention, FIG. 2 is a cross-sectional view of a high-pressure supply pump of this embodiment,
FIG. 3 is a cross-sectional view of the solenoid valve of the present embodiment, FIG. 4 is a flowchart showing an example of a control routine performed in the electronic control unit of the present embodiment, and FIG. FIG. 6 is a graph illustrating the pressure fluctuation in the common rail of this embodiment, FIG. 7 is a graph illustrating the pressure fluctuation in the conventional device, and FIG. 8 is a pressure fluctuation in the conventional common rail. It is a graph explaining. 1 Diesel engine 2,2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h ... Fuel injection valve 4 ... Common rail 6,6a, 6b, 6c ... High pressure supply pump 8 ... Electronic control device 37 , 37a, 37b, 37c …… plunger

Claims (1)

(57) [Claims] The fuel is pressurized by a reciprocating plunger.
A fuel injection device for accumulating high-pressure fuel supplied from a high-pressure supply pump for pressure feeding in a pressure accumulating pipe and distributing and supplying fuel to a fuel injection valve provided for each cylinder of the internal combustion engine via the pressure accumulating pipe. In the above, the high-pressure supply pump is driven according to the rotation of the internal combustion engine, and the number of discharges per unit rotation according to the cycle of the internal combustion engine is a non-integer multiple or a non-integer number of the number of cylinders of the internal combustion engine. A fuel injection device characterized in that the fuel injection device has the configuration described in (1).