JPH0663488B2 - Fuel injection system for multi-cylinder engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection device for a multi-cylinder engine used for a diesel engine or the like.

(Prior Art) Generally, in this type of fuel injection device, fuel is sent from a fuel pump to a fuel pressurizing device such as a face cam mechanism or an opposed plunger mechanism through a fuel passage, and the fuel pressurizing device passes through a delivery valve or the like. Fuel is supplied to the fuel injection valve.

(Problems to be Solved by the Invention) However, generally, the fuel oil pump is composed of a vane pump or the like, and a pulsating pressure is generated in the discharge pressure thereof. Further, the fuel pressurizing device is composed of a face cam mechanism, an opposed plunger mechanism, and the like. When the engine speed decreases, the cam speed also decreases and the pressurization efficiency may significantly decrease. Therefore, in the conventional structure, especially at low speed operation, the pressure at the fuel injection valve becomes insufficient, and as a result, the particle size of the fuel spray from the fuel injection valve becomes large and the combustion state deteriorates, resulting in bluish white smoke, black smoke, and exhaust gas. Emissions will increase.

Conventionally, a pressure regulating valve is also provided in the fuel passage so that the pressure in the fuel passage is maintained at a constant value. However, in the conventional structure, since the fuel pressure in the fuel passage is always maintained at a constant value by the pressure regulating valve, it is difficult to accurately set the fuel pressure by the fuel pressurizing device in response to various operating conditions. Is one of the causes of worsening the combustion state.

Further, in high-speed operation, it is often not necessary to raise the fuel pressure so much, and in that case, the fuel oil pump wastefully pressurizes the fuel and wastes power.

(Means for Solving the Problems) In order to solve the above problems, the present invention uses an accumulator to achieve an arbitrary injection pressure regardless of the number of revolutions. It is configured.

1st invention WHEREIN: In one case assembly 1, the discharge port of the fuel oil pump 2 is provided with the fuel passage 12 of the upstream side and the downstream side.
13, a check valve 14 provided in the middle of the downstream side fuel passage 13 and a fuel pressurizing mechanism to connect to one fuel distribution mechanism 8, and a pressure regulating valve 3 is provided in the upstream side fuel passage 12. The upstream fuel passage is provided in the upstream fuel passage 12 on the downstream side of the pressure regulating valve 3.
An accumulator 4 for equalizing the pulsating pressure of the fuel in 12 is provided, and the fuel pressurizing mechanism pressurizes the pressurizing chamber 73 communicating with the downstream end of the downstream fuel passage 13 and the pressurizing chamber 73. And a pressure-increasing piston mechanism 7 for
Small diameter plunger 71 facing pressure chamber 73 and small diameter plunger
A large-diameter piston 70 connected to 71 is provided
Hydraulic control passages 15, 16 communicating with the overflow passage 16b are connected to a working chamber 72 for driving the hydraulic control passage.
15. A fuel injection for a multi-cylinder engine, characterized in that a solenoid valve 6 is provided on each of 15 and 16 and the fuel injection amount and the fuel injection start and end timing are controlled by the energization time and the energization start and end timing of the solenoid valve 6. It is a device.

A second aspect of the present invention is that, in one case assembly 1, the discharge port of the fuel oil pump 2 is connected to the upstream and downstream fuel passages 12,
13, a pressure regulating valve 3 is provided in one fuel distribution mechanism 8 via a check valve 14 and a fuel pressurizing mechanism provided in the downstream side fuel passage 13, and an upstream side fuel downstream of the pressure regulating valve 3 is provided. aisle
An accumulator 4 for equalizing the pulsating pressure of the fuel in the upstream fuel passage 12 is provided at 12, and a relief passage 38 extending from the upstream fuel passage 12 to the inlet passage 11 of the fuel pump 2 is provided at the pressure regulating valve 3. And a valve element 31 for opening and closing the escape passage 38.
And a solenoid 34 having a variable duty ratio for driving the valve element 31 so that the control hydraulic pressure can be arbitrarily and variably adjusted to a predetermined pressure corresponding to an operating condition. Is.

(Operation) According to the first aspect of the invention, in one case assembly 1, the fuel discharged from the fuel feed pump 2 is pressurized through the fuel passages 12 and 13 on the upstream side and the downstream side. Sent to the mechanism,
After being pressurized by the pressurization mechanism, it is sent from one fuel distribution mechanism 8 to the fuel injection valve of each cylinder. Then, the fuel discharged from the oil feed pump 2 is in a pulsating state, but the pulsating fuel is pressure-equalized by the accumulator 4 in the middle of the upstream fuel passage 12 and becomes fuel of uniform pressure and is fed to the fuel pressurizing mechanism. To be Further, according to the first aspect of the invention, since the solenoid valve 6 is used in the fuel pressurizing mechanism, the fuel injection amount and the fuel injection start / end timing can be controlled by the energization time and the energization start / end timing of the solenoid valve 6.

Further, when the solenoid valve type pressure regulating valve 3 is provided as in the second invention,
By changing the duty ratio (or the frequency of the control signal) by the control device 106, the pressure adjusted by the pressure regulating valve 3, that is, the pressure in the fuel passers 12, 13 can be adjusted to a predetermined pressure corresponding to the operating condition. Therefore, when the required pressure at the fuel injection valve is low, the pressure of the fuel in the fuel passages 12 and 13 can be reduced by the pressure regulating valve 3, and the fuel feed pump 2 can be prevented from unnecessarily pressurizing the fuel.

(Embodiment) FIG. 1 is a schematic vertical sectional view of an embodiment, and FIG. 2 is II- of FIG.
2 is a schematic sectional view showing a II section in a reduced scale. In FIG. 1, a fuel oil supply pump 2 is provided inside a case assembly 1. The pump 2 has a structure in which a rotor 21 to which a vane 20 is attached is connected to a rotary pump shaft 22 via a spline. The pump shaft 22 projects from the case assembly 1 in the horizontal direction, for example, and is connected to the crankshaft of the engine via a gear mechanism (not shown).

As shown in FIG. 2, a joint 10 is attached to an upper end portion of the case assembly 1, and an external fuel pump (not shown) to an external fuel pipe (not shown), the joint 10, and the inside of the case assembly 1 are attached. The fuel is sucked into the suction portion of the pump 2 via the inlet passage 11. The sucked fuel is compressed as the vane 20 and the rotor 21 rotate in the direction of arrow A, and is discharged from the discharge port to the passage 12. Is ejected.

The passage 12 extends obliquely upward in the case assembly 1, passes through the pressure regulating valve 3 and the accumulator 4, and extends to the conical slide valve 5 in FIG.

As shown in FIG. 2, the pressure regulating valve 3 is constituted by an electromagnetic needle valve, and is constituted by incorporating a valve body 31, a spring 32, a solenoid 34, etc. in a substantially cylindrical body assembly 30. The body assembly 30 is incorporated in the upper part of the case assembly 1, and a small diameter inlet hole 35 at the tip (lower end) communicates with the passage 12. The outer periphery of the upper end portion of the inlet hole 35 constitutes an annular valve seat 36, and the valve body 31 is seated on the valve seat 36.
An escape hole 33 is provided in the lower portion of the body assembly 30 in the radial direction. The escape hole 33 communicates with the fuel inlet passage 11 through an escape passage 38 inside the body assembly 30.

The solenoid 34 is incorporated in the upper portion of the body assembly 30 and biases the core 37 upward when it is excited. The spring 32 is arranged to bias the core 37 downward. The valve element 31 has an upward extension of the base end portion connected to the core 37.

According to the above structure, when the solenoid 34 is excited, the valve body 31
Moves away from the valve seat 36, whereby the inlet hole 35 communicates with the escape hole 33 through the gap around the valve body 31, and the pressure in the passage 12 escapes to the escape passage 38. When the solenoid 34 is de-energized,
The valve body 31 is seated on the valve seat 36 by being biased by the spring 32, and the inlet hole 35 is closed. Therefore, the pressure in the passage 12 does not escape.

As is clear from the above description, when the excitation time of the solenoid becomes long, the pressure in the passage 12 decreases, and when the excitation time of the solenoid 34 becomes short, the pressure in the passage 12 increases. The solenoid 34 is a control device (10
The excitation state is controlled by (6: FIG. 3). Specifically, the excitation state and the non-excitation state are periodically switched. By this switching, the valve body 31 moves in a substantially vibrating state, and the inlet hole 35 is opened and closed periodically. The control device changes the duty ratio (excitation time per unit time) according to operating conditions, thereby adjusting the temporal opening / closing rate of the inlet hole 35 of the valve body 31 to adjust the pressure of the passage 12. .

In order to control the fuel pressure in passage 12 as described above, passage 12
A pressure sensor 39 is attached to the. The sensor 39 is mounted at the end of the perforation forming the passage 12 and is connected to the control device via a signal line.

The accumulator 4 is arranged on the downstream side of the pressure regulating valve 3 and is fixed to the upper part of the case assembly 1. Although not clearly shown, the accumulator 4 has a pressure accumulating chamber communicating with the passage 12, and makes the pulsating pressure generated in the pump 2 uniform. Therefore, a uniform hydraulic pressure is supplied to the conical slide valve 5 in FIG.

In FIG. 1, the conical slide valve 5 is constructed by incorporating a valve body 51 and a compression coil spring 52 inside a tubular body 50. The body 50 is incorporated in the upper part of the case assembly 1 in a vertical posture, for example. A passage 54 connecting the passage 12 and the internal cavity 53 of the body 50 is provided in the lower portion of the body 50 in the radial direction of the body 50. A passage hole 55 is provided at the lower end of the body 50. Body surrounding passage hole 55
The inner periphery of the upper end of the annular portion of 50 forms a valve seat 56. In the illustrated state, the valve body 51 has a taper surface on the outer periphery of the lower end on which the valve seat 56 is seated, and the cavity 53 is formed around the lower portion of the valve body 51. At the bottom of the body 50, another radial passage 54a is provided, for example, on an extension of the passage 54. The passage 54a connects the passage 13 inside the case assembly 1 and the cavity 53.

The valve body 51 is a bottomed tubular member having an open upper end, and has a small hole 57 extending in the radial direction at the lower part thereof. Small hole 57 is valve body 51
The internal cavity 58 and the cavity 53 are connected to each other. The spring 52 is arranged in the inner cavity 58, and the lower end is the valve body 51.
Of the solenoid valve 6 is seated on the bottom and the upper part is seated on the lower surface of the body assembly 60 of the solenoid valve 6.

The body assembly 60 has a substantially cylindrical shape and is fitted and fixed to the inner circumference of the upward extension of the body 50. A valve body 61, a solenoid 62, a spring 63, etc. are incorporated in the body assembly 60. A communication hole 64 communicating with the upper end of the internal cavity 58 is provided at the center of the lower end of the body assembly 60.

The booster piston mechanism 7 includes a large-diameter piston 70 and a small-diameter plunger 71 on the same center line as the valve body 51 and the valve body 61.
And are slidably incorporated in the holes of the case assembly 1. The piston 70 is provided with a circular end wall and a skirt portion extending downward from the outer periphery thereof, and a flat circular upper end surface faces the lower end surface of the body 50. A working chamber 72 is formed between the upper end of the piston 70 and the lower end of the body 50. The upper end of the plunger 71 abuts on the center of the end wall of the piston 70,
The lower half portion is fitted into a small diameter hole (a hole forming the fuel pressurizing chamber 73) of the case assembly 1. A pressurizing chamber 73 is formed by the portion of the small diameter hole below the plunger 71. The passage 13 extends to the pressurizing chamber 73 via the check valve 14.

The area ratio between the upper end surface of the piston 70 and the lower end surface of the plunger 71 is, for example, 10: 1. Therefore, as will be described later, the working chamber 72
When, for example, a hydraulic pressure of 50 kg / cm ² is supplied, the plunger 71 pressurizes the fuel in the pressurizing chamber 73 to 500 kg / cm ² .

The lower end of the hydraulic control passage 15 (hydraulic release passage) communicates with the working chamber 72. The upper end of the passage 15 extends to the inner circumference of the body 50 and communicates with the annular groove 59 on the outer circumference of the upper portion of the valve body 51 in the illustrated state. The body 50 is provided with another hydraulic control passage 16 (hydraulic release passage) communicating with the annular groove 59. The passage 16 extends from the inside of the body 50 to the lower outer periphery of the body assembly 60, and further extends diametrically through the body assembly 60 from the inside of the body 50 to the inside of the body assembly 60.
The tip is connected to an external overflow passage 16b via a joint 16a attached to the case assembly 1.

The distribution shaft 8 is rotatably incorporated in the case assembly 1 on an extension line of the pump shaft 22. One end of the distribution shaft 8 and the large diameter tip 25 of the pump shaft 22 are connected to the Oldham coupling 80.
Are connected via. Delivery valve 9 is distribution shaft 8
Is incorporated inside the. Inlet passage for delivery valve 9
90 is connected to the pressurizing chamber 73. The outlet passage 91 of the delivery valve 9 is provided in the radial direction of the distribution shaft 8. The case assembly 1 has, for example, four passages 92 that can be connected to the outlet passages 91.
(Only one is shown) are provided around the distribution shaft 8 at equal angular intervals. The outlet of each passage 92 is connected to the fuel injection valve 101 of each cylinder through a joint 93 attached to the case assembly 1 and a high pressure fuel pipe 109 shown in FIG.

The large diameter tip portion 25 of the pump shaft 22 is supported by the case assembly 1 via a bearing 26. A pulse generating gear 27 is attached to the tip portion 25 near the bearing 26. A magnetic sensor 28 is attached to the case assembly 1 near the outer periphery of the gear 27. The sensor 28 sends a pulse signal corresponding to the rotation speed of the gear 27 to the control device 106 (FIG. 3). The control device 106 controls the solenoid valve 6 and other devices (not shown) based on signals from the sensor 28 and other operating state detection sensors (not shown) as follows.

As shown in FIG. 3, a pulse generation gear 104 is also attached to the crankshaft 103 of the engine, and a sensor 105 for detecting the rotation of the gear 104 is provided in the vicinity thereof. Reference numeral 106 is a CPU of a microcomputer constituting the control device, 107 is an accelerator pedal, and 108 is a fuel tank.

As described above, the fuel discharged from the pump 2 is supplied to the pressure regulating valve 3
After being pressure-regulated by the accumulator 4 and equalized by the accumulator 4, for example, 50 kg from the passage 12 to the pressurizing chamber 73 via the passage 13 and the check valve 14.
Supplied with a hydraulic pressure of / cm ² .

Then, as shown in the figure, when the solenoid 62 is not excited, the valve body 61 is moved downward by being urged by the spring 63,
The tapered surface of the outer periphery of the lower end of the valve body 61 is seated on the valve seat of the outer periphery of the upper end of the communication hole 64. Therefore, the inner cavity 58 is sealed. In this state, there is no passage to the sealed inner cavity 58.
Since the hydraulic pressure is supplied from 12 through the passage 54 and the small hole 57, the cavity 58 is in a pressurized state. Therefore, the valve body 51 closes the passage hole 55 by receiving the hydraulic pressure inside the cavity 58. Further, the annular groove 59 of the valve body 51 connects the passage 15 and the passage 16.

In this state, the plunger 71 does not compress the fuel in the pressurizing chamber 73. The opening pressure of the delivery valve 9 is set higher than the supply pressure from the passage 13. Therefore, delivery valve 9
No fuel is discharged from the outlet passage 91.

Next, when the solenoid 62 is excited, the valve body 61 is pulled up to open the upper end of the communication hole 64, and the hydraulic pressure of the internal cavity 58 is changed to the communication hole 64.
Escape to passage 16 via. Therefore, the valve body 51 is pushed up by the hydraulic pressure in the cavity 53 at its lower part, the valve body 51 separates from the valve seat 56, and the annular groove 59 moves with respect to the passages 15 and 16 to move the passage 15 to the passage 16. Shut off against. This prevents the hydraulic pressure in the working chamber 72 from escaping from the passage 15. Further, hydraulic pressure is supplied from the cavity 53 to the working chamber 72 through the communication hole 55.
Therefore, the working chamber 72 is pressurized, the piston 70 moves downward, and the plunger 71 pressurizes the fuel in the pressurizing chamber 73.

The pressurized fuel is sent from the inlet passage 90 through the delivery valve 9 to the outlet passage 91, and from the outlet passage 91 to the passage 92 and the joint 93.
And so on to the fuel injection valve. Further, the fuel is supplied from the outlet passage 91 to the passage 92 only when the outlet of the outlet passage 91 communicates with the inlet of the passage 92 as the distribution shaft 8 rotates.

The above-described fuel pressurization / injection operation ends when the energization of the solenoid 62 is stopped. Fuel injection quantity is solenoid
Corresponding to the energization time to 62, the start timing and end timing of the fuel injection correspond to the energization start timing and energization end timing to the solenoid 62. The control device controls the timing and duration of energization of the solenoid 62.

In the above operation, the fuel discharged from the oil feed pump 2 is in a pulsating state, but the pulsating fuel is pressure-equalized by the accumulator 4 as described above, and becomes fuel of uniform pressure and is sent to the pressurizing chamber 73. To be Therefore, the pressure of the fuel sent from the pressurizing chamber 73 to the delivery valve 9 is set irrespective of the pulsating pressure and does not temporarily decrease significantly.

Further, in the above operation, when the engine is operated at a high speed, the required discharge pressure from the delivery valve 9 (required injection pressure at the fuel injection valve) may be relatively low. In that case, the duty ratio of the pressure regulating valve 3 is changed as described above, and the set pressure of the pressure regulating valve 3 is lowered. As a result, the pressure in the passage 12 is reduced and the supply pressure to the delivery valve 9 is reduced. Further, when the pressure in the passage 12 is reduced in this way, the load on the pump 2 is reduced, so that the required power of the pump 2 is also reduced.

(Effects of the Invention) According to the first and second inventions, the pressure regulating valve 3, the fuel pressurizing mechanism, and the fuel distributing mechanism 8 are built in one case assembly 1, and pressure feeding and control are performed at one location. Since the case assembly 1 can be distributed to each cylinder (because it is a so-called booster type and solenoid valve controlled distribution type injection device), it can be manufactured at low cost, and the fuel injection valve is the same as the conventional one. Since it can be used, it can be easily attached to the cylinder head and can be used in small engines. Further, since the supply pressure to the fuel pressurizing device is made uniform by the accumulator 4, it is possible to prevent the fuel injection pressure from becoming insufficient even during low-speed operation and to miniaturize the fuel spray. Therefore, a good combustion state can always be maintained.

In particular, according to the first aspect of the invention, since the booster piston mechanism 7 is adopted as the final fuel pressurizing means, and the solenoid valve mechanism including the solenoid valve 6 is used as the means for controlling the operation of the booster piston mechanism 7. It is possible to adjust and set the pressurization characteristics (fuel injection amount and fuel injection start / end timing) more accurately with a device with a relatively simple structure, and even if an electronic control system is adopted, it is relatively easy and Control can be performed with an inexpensive device.

Further, according to the second aspect of the present invention, the solenoid valve type pressure regulating valve 3 whose duty ratio is changeable is provided to adjust the pressure in the passage 12, so that the fuel feeding pump 2 wastefully pressurizes fuel during high speed operation or the like. This can be prevented, and power consumption in the oil feed pump 2 can be prevented. Moreover, the fuel passage 12 is formed by the pressure regulating valve 3.
Since the fuel pressure can be maintained at a predetermined optimum value corresponding to the operating condition, the discharge pressure from the delivery valve 9 can be accurately set in this respect as well, and the combustion state can be further improved. Further, since the duty ratio changing type solenoid valve is adopted as the pressure regulating valve 3, it becomes easy to control the pressure regulating valve 3 by the electronic control unit.

(Another embodiment) Although not shown, one or a plurality of (for example, two) other pressure boosting piston mechanisms are arranged in the vicinity of the pressure boosting piston mechanism 7, and the working chamber of the pressure boosting piston mechanism 7 is illustrated. It is also possible to connect 72 to the working chamber of the added booster piston mechanism by a communication passage. With this structure, it is possible to increase the capacity of the entire pressurizing chamber 73.

A gear pump may be used as the oil feed pump 2.

A pulse motor can also be used as a drive means dedicated to the distribution shaft 8.

[Brief description of drawings]

1 is a schematic vertical sectional view of an embodiment of the present invention, FIG. 2 is a schematic sectional view showing the II-II section of FIG. 1 in a reduced scale, and FIG. 3 is a side view of an engine adopting the fuel injection device of FIG. It is a schematic diagram.
2 ... Fuel oil pump, 3 ... Pressure regulating valve, 4 ... Accumulator, 5 ... Conical slide valve, 6 ... Electromagnetic valve, 7 ... Pressure increasing piston mechanism, 8 ... Distribution shaft (fuel distribution mechanism) , 12, 13 …… Fuel passage, 15, 16 …… Hydraulic control passage, 31 …… Valve body, 33 …… Relief hole, 34 …… Solenoid, 38
…… Escape passage, 70 …… Large piston, 71 …… Small plunger, 72 …… Working chamber, 73 …… Fuel pressurizing chamber

Claims (2)

[Claims] 1. In one case assembly (1), a fuel oil supply pump (2) is provided with a fuel discharge port (2) at an upstream side and a downstream side of fuel passages (12, 1).
3. Connected to one fuel distribution mechanism 8 via a check valve 14 and a fuel pressurizing mechanism provided in the downstream side fuel passage 13, and the pressure regulating valve 3 is provided in the upstream side fuel passage 12. The upstream fuel passage is provided in the upstream fuel passage 12 on the downstream side of the pressure regulating valve 3.
An accumulator 4 for equalizing the pulsating pressure of the fuel in 12 is provided, and the fuel pressurizing mechanism pressurizes the pressurizing chamber 73 communicating with the downstream end of the downstream fuel passage 13 and the pressurizing chamber 73. And a pressure-increasing piston mechanism 7 for
Small diameter plunger 71 facing pressure chamber 73 and small diameter plunger
A large-diameter piston 70 connected to 71 is provided
Hydraulic control passages 15, 16 communicating with the overflow passage 16b are connected to a working chamber 72 for driving the hydraulic control passage.
A solenoid valve 6 that connects or disconnects the hydraulic control passages 15 and 16 is provided in the valves 15 and 16, and the fuel injection amount and the fuel injection start / end timing are controlled by the energization time and the energization start / end timing of the solenoid valve 6. A fuel injection device for a multi-cylinder engine characterized by the above. 2. In one case assembly (1), the discharge port of the fuel oil feed pump (2) is connected to the upstream and downstream fuel passages (12, 1).
3. Connected to one fuel distribution mechanism 8 via a check valve 14 and a fuel pressurizing mechanism provided in the downstream side fuel passage 13, and the pressure regulating valve 3 is provided in the upstream side fuel passage 12. The upstream fuel passage is provided in the upstream fuel passage 12 on the downstream side of the pressure regulating valve 3.
An accumulator 4 for equalizing the pulsating pressure of the fuel in 12 is provided, and a relief passage 38 extending from the upstream fuel passage 12 to the inlet passage 11 of the fuel pump 2 and a relief passage 38 are provided in the pressure regulating valve 3. A valve body 31 for opening and closing the valve, and a solenoid 34 with a variable duty ratio for driving the valve body 31 are provided so that the control hydraulic pressure can be arbitrarily and variably adjusted to a predetermined pressure corresponding to operating conditions. Fuel injector for multi-cylinder engine.