JP2512893B2 - Fuel injector - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a fuel injection device for supplying fuel to a diesel engine or the like, and more particularly to a structure of a unit injector.

[Technical background of the invention]

In recent years, in order to improve the combustion characteristics of diesel engines, it has been required to increase the fuel injection pressure. For this reason, hydraulic pressure is generated by a pressure-feeding plunger that is operated in synchronization with the engine, the injection plunger is driven by this hydraulic pressure, and the fuel previously introduced into the injection pump chamber is pressurized to a high pressure by the injection plunger. A device for injecting pressurized fuel at high pressure from an injection nozzle has been considered.

In this case, the fuel injection amount and injection timing must be controlled according to the operating condition of the engine.

As a means for controlling the fuel injection amount and the injection timing, a device using a solenoid valve has already been developed as disclosed in Japanese Patent Application Laid-Open No. 58-217759. In this device, when the pulse signal to the solenoid valve is controlled, the amount of injected fuel can be adjusted according to the opening time of the solenoid valve, and the injection timing can be adjusted by the opening timing of the solenoid valve. There is an advantage that the injection amount and the injection timing can be easily controlled according to the operating condition.

[Problems of background technology]

However, in the above-mentioned conventional one, in order to improve the disconnection of the injection at the end of injection, the fuel in the injection pump chamber is returned to the metering passage having a predetermined volume at the end of injection (hereinafter referred to as spill), Depending on the stop position of the injection plunger, the total volume of the pumping system may differ between the case where it is in communication with the metering passage and the case where it is not in communication, and intermittent injection may occur when the injection amount is low.

Further, if the above spill is abolished as a countermeasure, the injection plunger vibrates at the end of injection, and not only the disconnection at the end of injection is bad but also noise is generated.

[Object of the Invention]

The present invention has been made based on such a situation, and its purpose is to improve the end of injection by providing a spill pressure absorbing piston, and there is no noise, and it is easy to control the injection timing using a solenoid valve. Therefore, it is an object of the present invention to provide a fuel injection device capable of high pressure injection.

[Outline of Invention]

That is, according to the present invention, the fuel in the pressure-feed pump chamber is pressurized by the pressure-feed plunger that is operated in synchronism with the engine, and the injection plunger is activated by the fuel pressure in the pressure-feed pump chamber to pressurize the fuel in the injection pump chamber and the injection nozzle In the case of more injection, a spill pressure absorbing piston that absorbs the pressure in the injection pump chamber at the end of injection is provided to improve the disconnection of injection and prevent noise.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

This embodiment is shown together with a distribution type fuel metering device, and FIG. 1 shows its configuration. In this figure, a distribution type fuel metering device 111 for distributing and supplying fuel to a plurality of cylinders provided in an internal combustion engine, and one of the unit injectors 1 provided for each of the above cylinders are taken out and shown. Therefore, a unit injector similar to that shown in the figure is provided for each cylinder of the engine.

In the case of a 4-cylinder 4-cycle engine, for example, the distributed fuel metering device 111 includes a rotary shaft 113 that makes one revolution by two revolutions of the engine. A feed pump 114 is integrally provided on the rotating shaft 113, and the fuel from the fuel tank 61 is pressure-fed to a fuel chamber 117 formed inside the housing 116 when the engine rotates. Also, this rotating shaft 113
The rotation information such as the rotation speed of the above is detected by the detector 118, and this rotation information is supplied to the control circuit 80 as a detection signal for calculating the fuel injection amount and the like.

Inside the fuel chamber 117, a cylinder 120 is provided at a position coaxial with the rotating shaft 113, and a distribution plunger 121 is set in a state of being inserted and set in the cylinder 120. The distribution plunger 121 is rotationally driven coaxially with the rotation shaft 113, and is reciprocated in the axial direction with the rotation of the rotation shaft 113 by the face cam 124 on which the roller 122 fixed to the housing 116 and the spring 123 act. It is set up to be exercised. Specifically, 4
When the fuel is distributed to the cylinders, the rotary shaft 113 is reciprocated four times with one rotation.

Such a distribution plunger 121 is provided with a fuel passage 126 along an axis communicating with a distribution pump chamber 125 formed between the tip of the distribution plunger 121 and the bottom portion of the cylinder 120, and the passage 126 is a side wall of the cylinder 120. Distribution port 12
7, spill boat 12 that opens further behind the cylinder 120
Connect to 8. The distribution port 127 is communicated with the discharge valve 130 via the fuel passage 129 corresponding to each cylinder formed in the cylinder 120 portion according to the rotation angle of the distribution plunger 121,
The fuel is distributed and supplied as the metered fuel to the corresponding unit injector 1. The fuel metering will be described later.

Also, on the outer circumference of the distribution plunger 121, the spill port 1
A spill ring 131 is provided at a position corresponding to 28. The spill ring 131 is an electromagnetic plunger mechanism 13 controlled by a command from a control circuit 80 to which signals of an engine operating condition such as an accelerator position, that is, engine load and rotation speed are supplied.
The axial position is controlled by 2 and the fuel overflow timing from the spill port 128 is controlled in accordance with the axial movement of the distribution plunger 121, and the distribution port 127 to the unit injector 1 of each cylinder is controlled. The amount of fuel distributed and supplied is adjusted. The operating state of the electromagnetic plunger mechanism 132 that performs the above-mentioned metering control is detected by the detector 133, and the detection signal is supplied to the control circuit 30. Note that the distribution pump 125 is supplied with fuel from the fuel chamber 117 via the introduction port 134 and the feed port 135. The electromagnetic valve 136 provided in the feed port 135 is closed, for example, when the engine is stopped, so that the fuel is supplied to the fuel chamber 11.
It is prevented from being sent to the distribution pump chamber 125 by the device 7.
Therefore, when the solenoid valve 136 is closed, the amount of fuel sent to the unit injector 1 is naturally zero.

The unit injector 1 is inserted and set in the engine head 140, and the fuel galleries 142a and 142b are set by the O-rings 141a to 141c.
The fuel gallery 142a is a distribution type fuel metering device.
Fuel of a specified pressure is supplied from the fuel chamber 117 of 111 through the filter 143, the check valve 144, and the feed passage 145.

In addition, to the fuel gallery 142a, although not shown in the figure, a feed pump driven by an engine may take out fuel from the fuel tank and regulate the maximum pressure with a safety valve or the like to supply the fuel.

In FIG. 2, reference numeral 1 denotes a unit injector, and this unit injector 1 is provided with a pressure feeding cylinder 2, an injection cylinder 3, a nozzle holder 4 and a holder nut 5. The lower surface of the pressure feeding cylinder 2 is in pressure contact with the upper surface of the injection cylinder 3, and the lower surface of the injection cylinder 3 is in pressure contact with the upper surface of the nozzle holder 4. The pressure feeding cylinder 2, the injection cylinder 3 and the nozzle holder 4 are integrally connected by the holder nut 5.

A pressure-feeding plunger 6 is slidably fitted in the pressure-feeding cylinder 2 to form a pressure-feeding pump chamber 7. The pressure-feeding plunger 6 is connected to a cam follower 8, and the cam follower 8 is driven downward by a cam that rotates in synchronization with an engine (not shown) directly or indirectly via a rocker arm or the like. A follower spring 9 is bridged between the pressure-feeding cylinder 2 and the cam follower 8, and the spring 9 allows the cam follower 8 and the pressure-feeding plunger 6 to return upward in the drawing. Reference numeral 10 is an open hole formed in the pressure feeding cylinder 2, which serves to supply lubricating oil to the amfollower 8 and to remove air.

A feed port 11 is opened at the lower end of the pressure feed pump chamber 7, and the feed port 11 communicates with a solenoid valve mechanism 13 mounted on the pressure feed cylinder 2 via a feed passage 12. The solenoid valve mechanism 13 operates the poppet valve 15 with the sonoid coil 14.
The spring 15 is constantly urged by the spring 16 to the left in the drawing. When the poppet valve 15 is actuated in the axial direction (left and right direction in the drawing) by the electromagnetic force of the solenoid coil 14 and the pressing force of the spring 16, the poppet valve 15 opens and closes the communication passage between the passages 18 and 19. One passage 18 is the feed passage 12 described above.
, And the other port 19 communicates with the inlet passage 20.

The solenoid coil 14 of the solenoid valve mechanism 13 is adapted to be operated by a control circuit 80 such as a computer, which will be described later.

An injection plunger 24 is slidably fitted in the injection cylinder 3 to form an injection pump chamber 25. The injection plunger 24 is formed to have a smaller diameter than the pressure-feeding plunger 6, and a pressure receiving chamber 26 communicating with the pressure-feeding pump chamber 7 is formed on the upper surface side of the injection plunger 24. A spill port 27 and a drain port 28 are formed in the injection cylinder 3, and the spill port 27 communicates with the spill absorption chamber 102 via a passage 29.

A spill pressure absorbing piston 101 is slidably fitted in the spill pressure absorbing cylinder 300. The spill pressure absorbing piston 101 is shown in the upper absorption spring 1 in the figure.
Always urged downward by 03.

The space containing the spring 103 communicates with the fuel gallery 30 via a passage 104. Also drain port
The 28 also communicates with the fuel gallery 30.

An annular groove 34 is formed in the injection plunger 24, and one surface of this annular groove 34 forms a spill lead 35. The annular groove 34 communicates with the injection pump chamber 25 via a horizontal hole 36 and a vertical hole 37. The upper surface of the injection plunger 24 forms a drain lead 38.

The injection pump chamber 25 communicates with the metering check valve chamber 41 via the metering port 40. The metering check valve chamber 41 communicates with the fuel gallery 30 via the check valve 42 and the second metering passage 22. The metering check valve chamber 41 communicates with a fuel passage 43 formed in the nozzle holder 4.

An injection nozzle 45 is attached to the nozzle holder 4, and the fuel passage 43 communicates with the injection nozzle 45. The injection nozzle 45 is a known one, and when fuel having a pressure equal to or higher than a predetermined pressure is sent from the fuel passage 43, the needle valve 46 is pushed up against the nozzle spring 47, and the valve hole 48 is opened to discharge this fuel to the engine. Inject into the cylinder. The nozzle spring 47 is housed in a nozzle spring chamber 49 formed in the nozzle holder 4. The nozzle spring chamber 49 communicates with the fuel gallery 30 via a passage (not shown).

The solenoid valve mechanism 13 is opened and closed by receiving a command signal according to the operating condition of the engine from the control circuit 80 described above. The injection timing is determined by the valve closing timing of the solenoid valve mechanism 13.

The control circuit 80 receives signals from sensors 81a to 81n that detect engine speed, accelerator pedal depression amount, engine temperature, and other engine operating conditions, and calculates the opening / closing timing of the solenoid valve mechanism 13 based on these signals. Then, a command signal is given to the solenoid valve mechanism 13 so that a predetermined injection timing is obtained.

 Next, the operation of this embodiment will be described.

In the unit injector 1 configured as described above, first, when the pressure-feeding plunger 6 rises from the bottom dead center, the solenoid coil 14 is energized and the poppet valve is operated.
When the valve 15 is opened, the passages 12 and 18 are communicated with the passages 19 and 20, and the low pressure fuel in the fuel chamber 117 of the distribution type fuel metering device 111 is regulated into the pumping pump chamber 7 by the filter 143 and the reverse. Stop valve
144, feed passage 145, fuel gallery 142a, 30, passage 2
0, the electromagnetic valve mechanism 13, the passage 12, and the feed boat 11 are fed to fill the space.

Next, the fuel pressurized in the distribution pump chamber 125 of the distribution type fuel metering device 111 when the pressure-feeding plunger 6 is stopped at the ascending point passes through the passage 126, the distribution port 127, the passage 129, and the discharge valve 130. Is sent to the metering passage 181 via the gallery 142b, the gallery 23, and the second metering passage 22, and the check valve 42 is opened to be sent to the metering check valve chamber 41. Is supplied to the injection pump chamber 25 via. The injection plunger 24 is moved upward to a position corresponding to this supply amount. At this time, the poppet valve 15 remains open. Where the injection pump chamber
The amount of fuel supplied to 25 is adjusted by the distributed fuel metering device 111 and corresponds to the operating state of the engine. That is, a large amount of fuel is supplied to the injection pump chamber 25 when the engine is in a high load state, and the fuel amount is reduced when the engine is in a low load state.

Here, regarding the amount of fuel supplied from the discharge valve 130 to the injection pump chamber 25 via the metering passage 181 and the like, the suction lead formed as the end face of the distribution plunger 121 has a field port 13
After closing 5, close the spill ring 131 to the spill port.
It is a value obtained by multiplying the pressure feeding stroke of the distribution plunger 121 and the sectional area of the distribution plunger 121 until the opening of 128. This fuel amount changes depending on the position of the spill ring 131, that is, the accelerator position, the engine speed, and the like. For example, when the load is low, move the position of the spill ring 131 to the left in FIG. Thus, the pressure feeding stroke is shortened to reduce the amount of fuel to be metered. In this way, the adjusted fuel amount is controlled to an optimum value according to the operating state of the engine.

In this state, when the cam follower 8 is driven against the spring 9 by the cam corresponding to the rotation of the engine and the pressure feed plunger 6 is driven, the fuel in the pressure feed pump chamber 7 remains in the open state because the poppet valve 15 remains open. Passage from Ford Port 11
It is discharged to the tank 61 side through the electromagnetic valve mechanism 13, the passage 20, the fuel gallery 30, 142a.

In this state, when the control circuit 80 shuts off the energization of the solenoid coil 14 of the solenoid valve mechanism 13 to close the poppet valve 15 by the force of the spring 16, the passage 12 and the passage 20 are shut off. In this case, the command to the solenoid coil 14 is calculated and given by the control circuit 80 in accordance with the engine speed, the load, etc. so that the optimum fuel injection timing is reached.

When the solenoid valve mechanism 13 is closed, the pressure in the pressure-feeding pump chamber 7 rises, the fuel in the pressure-feeding pump chamber 7 becomes high pressure as the pressure-feeding plunger 6 moves, and the pressure acts on the injection plunger 24. The fuel pressure in the pump chamber 25 will increase. When this high-pressure fuel is transmitted to the nozzle 45 via the injection fuel passage 43 and reaches the valve opening pressure,
The needle valve 46 is pushed up against the nozzle spring 47, and fuel injection from the nozzle injection hole 48 is started. This electromagnetic valve closing timing is the fuel injection timing.

In this case, the poppet valve of the solenoid valve mechanism 13
High-pressure fuel acts on 15, but this high-pressure fuel acts as back pressure in the valve closing direction of the poppet valve 15, which leads to an improvement in the sealing performance of the poppet valve 15.

Then, the pressure-feeding plunger 6 is continuously driven against the spring 9 by a cam (not shown), and this fuel injection state is continued.

Continued lowering of the pressure feed plunger 6 causes the injection plunger
When the spill reed 35 of 24 opens the spill port 27, the high-pressure fuel in the injection pump chamber 25 receives the vertical hole 37, the horizontal hole 36, the annular groove 34,
Spill absorption chamber 102 via spill port 27 and passage 29
Flow into.

Then, the pressure of the spilled fuel that has flowed in causes the spill pressure absorption piston 101 to move upward in the figure against the absorption spring 103. As a result, the fuel pressure in the injection pump chamber 25 decreases and the injection plunger 24 further descends.

Next, when the drain lead 38 of the injection plunger 24 opens the drain port 28, the fuel in the pressure feed pump chamber 7 is returned to the fuel gallery 30 through the pressure receiving chamber 26 and the drain port 28, so that the pressure feed pump chamber 7 inside. Fuel pressure drops.
At this point, the movement of the injection plunger 24 is temporarily stopped.
FIG. 3 shows the state.

The pressure-feeding plunger 6 is pushed by a cam (not shown) and continues to descend, but the fuel pressure in the pressure-feeding pump chamber 7 does not increase, so the injection plunger 24 remains stopped.

Then, when the pressure-feeding plunger 6 reaches the bottom dead center and stops, the spill pressure absorbing piston 101 descends by the absorbing spring 103, and the fuel absorbed in the spill absorbing chamber 102 passes through the passage 29, the spill port 27, and the annular groove 34. After passing through the horizontal hole 36 and the vertical hole 37, it is returned to the injection pump chamber 25. This causes the injection plunger 24 to rise to the position where the spill port 27 is closed.

Next, when the pressure-feeding plunger 6 rises from the bottom dead center, the above-described operation is repeated.

In the embodiment having such a configuration, the distributed fuel metering device 111 controls the amount of fuel to be injected.

Further, in the process of lowering the pressure-feeding plunger 6, the solenoid valve mechanism 13
When is closed, the pressure in the pumping pump chamber 7 rises to push the injection plunger 24 and start the injection of fuel, so that the fuel injection timing can be adjusted by controlling the closing timing of the solenoid valve mechanism 13.

In the unit injector 1 shown in FIG. 2 as described above, the injection cylinder 3 and the pressure feeding cylinder 2 are formed separately, so that each fuel passage 1 formed in the pressure feeding cylinder 2 is formed.
2, 20 and solenoid valve mechanism 13 mounting holes, and when forming the drain port 28, spill port 27, spill passage 29, metering passage 22, etc. formed in the injection cylinder 3, for drilling each passage and hole Handling such as correcting the attitude of the cylinder toward the processing direction becomes easy.

〔The invention's effect〕

As described above, according to the present invention, at the end of injection, the pressure in the volume of the injection system is temporarily absorbed by the spill pressure absorbing piston to eliminate vibration of the injection plunger, thereby preventing secondary injection and ending injection. In addition to improving fuel injection, the fuel is returned to the injection pump chamber during metering to raise the injection plunger until the spill port is closed to prevent asymmetric and intermittent injection, and to reduce noise generated by vibration of the injection plunger. The excellent effect of being able to do is exhibited.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating a fuel injection device for an internal combustion engine according to an embodiment of the present invention, FIG. 2 is a sectional configuration diagram particularly showing a unit injector portion of the device, and FIG. 3 is a state of the unit injector. It is sectional drawing which showed. 1 ... Unit injector, 2 ... Pressure feed cylinder, 3
…… Injection cylinder, 4 …… Nozzle holder, 6 …… Injection plunger, 7 …… Pressure pump chamber, 13 …… Solenoid valve mechanism, 14
...... Solenoid coil, 15 …… Poppet valve, 24 …… Injection plunger, 25 …… Injection pump chamber, 27 …… Spill port, 28 …… Drain port, 45 …… Injection nozzle, 101…
… Spill pressure absorbing piston, 102… Spill absorbing chamber, 111
...... Distribution type fuel metering device, 113 …… Rotary shaft, 117 …… Fuel chamber, 80 …… Control circuit, 121 …… Distribution plunger, 125 ……
Distribution pump chamber, 131 …… spill ring, 300 …… spill pressure absorption cylinder.

Claims (1)

(57) [Claims] 1. A fuel in a pressure feed pump chamber (7) is pressurized by a pressure feed plunger (6) driven in synchronism with an engine,
The injection plunger (24) is operated by the hydraulic pressure generated in the pressure pump chamber (7), and the fuel in the injection pump chamber (25) is pressurized by the injection plunger (24) and injected from the injection nozzle (45). A solenoid valve (13) is provided in the middle of a passage (12) that connects the pressure pump chamber (7) and the low pressure side, and the solenoid valve is closed to boost the pressure of the fuel in the pressure pump chamber (7) to inject fuel. A fuel injection device for controlling timing, comprising: a spill pressure absorbing cylinder (300) communicating with the injection plunger (24) when the injection plunger (24) reaches a position where it almost reaches the lowest point in the injection pump chamber (25); And a spill pressure absorbing piston (101) slidably fitted in the absorption cylinder (300). When the fuel injection is completed, the spill pressure absorbing piston (101) causes the spill pressure absorbing piston (101) inside the injection pump chamber (25). Pressure A fuel injection device characterized by absorption.