JPH0415392B2 - - Google Patents

Description

control solenoid valve 57 and a unit injector.

2. A needle spindle bore 20 with a valve seat 21 and nozzles 22, 23, and a plunger bore 32, 33 open at one end and communicated at the other end with the fuel reservoir 24 of the needle spindle bore 20. a nozzle needle 12 fitted in its needle spindle bore 20 and seated on its valve seat 21 with a pressure spring 29; and the open side of its plunger bores 32, 33. a booster plunger 13 that is slidably fitted in a reciprocating manner and opens and closes a first-stage injection cut-off port 39 and a main injection cut-off port 40 that are opened in the plunger bores 32 and 33; The plunger bore 3 is fitted in the plunger bores 32 and 33 closed by the booster plunger 13 so as to be slidable back and forth.
An injection pumping chamber 45 is installed on the fuel reservoir 24 side of 2, 33, and the plunger bore 3
2 and 33 of the booster pumping chambers 38 on the side of the booster plunger 13, respectively.
The injection plunger 14 opens and closes the spill ports 46 opened in the plunger bores 32 and 33, and the injection pumping chamber 45 is provided with a check valve 48 on the side of the injection pumping chamber 45. A fuel feed canal 47 connecting to the feed pump 52 and a pressure canal 25 , 31 downstream of the check valve 48 of the fuel feed canal 47 connecting the injection pumping chamber 45 to the fuel sump 24 . and a fuel feed canal 5 connecting the first stage injection cut-off port 39 and the main injection cut-off port 40 to the feed pump 53.
0, a spill fuel communication channel 51 connecting the spill port 46 to the pressure spring 29 side of the needle spindle bore 20, and a spill fuel piping 56 connecting the spill port 46 to the fuel reservoir. ,and,
A solenoid valve 57 that controls the amount of high-pressure fuel released from the booster pumping chamber 38 to the fuel reservoir, and a current flowing through the solenoid valve 57 in response to signals from the engine speed sensor 61 and the load sensor 62. and a control unit 58 for controlling the unit injector.

[Detailed description of the invention]

The present invention relates to a unit injector used in a diesel engine, and particularly to a spillless type unit injector.

Conventional unit injectors include a fuel feed pump that connects the feed pump to an injection pumping chamber defined by a metering plunger.
A check valve is placed in the canal, and the spill port is connected to the fuel feed canal on the upstream side of the check valve, so that during the pressurization stroke of the booster plunger, there is no leakage from the injection pumping chamber. The pressure of the fuel returned to the fuel feed canal, that is, the spill pressure, opened the check valve, causing secondary injection of fuel, and resulting in poor fuel starvation. As a result, high-pressure fuel injection was difficult with this type of unit injector.

Furthermore, in Japanese Patent Laid-Open No. 57-83658, fuel is metered by a solenoid valve that is opened for a predetermined time depending on the pilot injection amount, and a check valve is pushed open through a balance orifice to open a fuel passage. A fuel injection device is disclosed in which the fuel is pumped into the pilot pump chamber, and the pilot plunger is pushed up by a stroke corresponding to the pilot injection amount and then stopped. The structure is such that the high-pressure fuel in the pilot pump chamber is released into the supply passage via the communication passage, so the spill pressure of the high-pressure fuel released in this way is The nozzle/needle closure is insufficient, causing unstable fuel shortage during pilot injection.

Furthermore, Japanese Patent Application Laid-Open No. 57-76258 discloses that the fuel injection amount is controlled by a solenoid valve, and the fuel pressure in at least one of the pressure pump chamber and the injection pump chamber is transferred to the pressure transfer plunger and the injection plunger. Although a fuel injection device is disclosed that includes a pressure reduction chamber that temporarily lowers the pressure during stroke,
Since the pressure reduction chamber has a constant volume structure, the pressure that is reduced is extremely small, and as a result, fuel depletion during pilot injection is insufficient.

The purpose and problem of this invention is to prevent secondary injection of fuel due to fuel spill pressure, enable high-pressure injection of fuel, improve sharpness at the end of fuel injection, improve engine performance, and simplify structure. The object of the present invention is to provide a unit injector used in a diesel engine that enables miniaturization.

In connection with the above-mentioned objects and problems, the unit injector of the present invention has a needle spindle bore having a valve seat and a nozzle, and a fuel reservoir of the needle spindle bore that is open at one end and has a fuel reservoir at the other end. a pump body having a plunger bore in communication with the pump body; a nozzle needle fitted in the needle spindle bore and seated in the valve seat by a pressure spring; A booster plunger that opens and closes a first-stage injection cut-off port and a main injection cut-off port that are slidably fitted together in a reciprocating manner and that are opened in the plunger bore; and a booster plunger that is closed by the booster plunger. reciprocally slidably fitted into the plunger bore and forming an injection pumping chamber on the fuel reservoir side of the plunger bore and a booster pumping chamber on the booster plunger side of the plunger bore. and in that booster pumping chamber,
The spill that is opened in the plunger bore.
An injection plunger for opening and closing a port, and a check valve on the injection pumping chamber side thereof, and
a fuel feed canal connecting the injection pumping chamber to the feed pump; a pressure canal connecting the injection pumping chamber to the fuel sump downstream of the check valve of the fuel feed canal; First stage injection cut-off port and main injection cut-off port
a fuel feed canal connecting the port to the feed pump; a spill fuel communication channel connecting the spill port to the pressure spring side of the needle spindle bore; and a spill connecting the spill port to the fuel reservoir. a solenoid valve disposed in the fuel line and controlling the amount of high pressure fuel vented from the booster pumping chamber to the fuel reservoir, and further responsive to signals from the engine speed sensor and the load sensor. a control unit that controls the current flowing through the solenoid valve;
At the end of fuel injection, high pressure fuel is applied to the nozzle needle as a back pressure and the nozzle needle back pressure is controlled to increase the cut-off speed of the nozzle needle.

Specific examples of the unit injector of the present invention will be described below with reference to the drawings.

The figure shows a specific example 1 of the unit injector of this invention used in a diesel engine (not shown).
It shows 0.

The unit injector 10 is a valve
A needle spindle bore 20 having a seat 21 and a plurality of nozzles 22, 23, one end of which is open and the other end of which is open.
Pump body 11 with plunger bores 32, 33 communicated with fuel reservoir 24 of bore 20
The nozzle needle 12 is fitted into the needle spindle bore 20 and is seated on the valve seat 21 by a pressure spring 29, and is reciprocally slidable on the opening side of the plunger bores 32 and 33. fitted into, and
A booster plunger 13 that opens and closes the first-stage injection cut-off port 39 and the main injection cut-off port 40 that are opened in the plunger bores 32 and 33, and the plunger bore that is closed by the booster plunger 13. 32,
33, and the fuel reservoir 24 of the plunger bore 32, 33.
an injection pumping chamber 45 on the side thereof, and a booster pumping chamber 3 on the side of its booster plunger 13 of its plunger bores 32, 33.
a spill port 4 formed in the booster pumping chamber 38 and opening into the plunger bore 32, 33, respectively;
6, and a check valve 48 on the side of the injection pumping chamber 45,
and a fuel feed connecting the injection pumping chamber 45 to the feed pump 52.
Canal 47 and its fuel feed Canal 4
Downstream of the check valve 48 of 7, the pressure canals 25, 31 connecting the injection pumping chamber 45 with the fuel reservoir 24 and the primary injection cut-off port 39 and the main injection cut-off port. 40 to the feed pump 53; a spill fuel communication channel 51 connecting the spill port 46 to the pressure spring 29 side of the needle spindle bore 20;
located in the spill fuel line 56 connecting the port 46 to the fuel reservoir and its booster
A solenoid valve 5 for controlling the amount of high pressure fuel released from the pumping chamber 38 into its fuel reservoir.
7, engine speed sensor 61 and load sensor 6
a control unit 58 which controls the current flowing through its solenoid valve 57 in response to signals from its booster pumping chamber 38 as a back pressure at the end of the main fuel injection.
The high-pressure fuel inside is applied to the nozzle needle 12, and the back pressure of the nozzle needle 12 is controlled to increase the cut-off speed of the nozzle needle 12.

The pump body 11 is composed of a nozzle 15, a pressure spring guide 16, an injection plunger guide 17, and a booster plunger guide 18, and a nut 19 connects the nozzle 15 and the pressure spring guide 16 to the injection plunger guide 17. There is.

The nozzle 15 includes a needle spindle bore 20 having a valve seat 21, a plurality of orifices 22, 23, a fuel reservoir 24, and a pressure canal 25 in communication with the fuel reservoir 24.

The pressure spring guide 16 is substantially coaxially aligned with its needle spindle bore 20 so as to form a pressure spring chamber 27 when assembled with its nozzle 15 into the injection plunger guide 17 with a nut 19. A pin hole 28 is formed at the lower end of the spring chamber bore 26, and the upper end of the spring chamber bore 26 is open. The pressure spring chamber 27 includes a pressure spring 2
9 and a spring seat 30 are arranged.

Furthermore, when the pressure spring guide 16 is connected with the nozzle 15 to the injection plunger guide 17 by the nut 19, the nozzle 1
Pressure canal 3 communicating with pressure canal 25 of 5
1.

The injection plunger guide 17 sequentially connects the pressure spring guide 16 and the nozzle 15 at the lower end with a nut 19, and also connects the booster plunger guide 1 at the upper end.
8, and includes an injection plunger bore 32 forming a lower portion of the plunger bores 32, 33 thereof. Of course, the injection plunger bore 32 is open at the top.

The booster plunger guide 18 has an axis that is offset from the axis of its injection plunger bore 32 when the injection plunger guide 17 is threadedly connected to its lower end.
2,33 with a booster plunger bore 33 forming the upper part of the booster plunger bore 33. Of course, the booster plunger bore 33 is formed in the booster plunger guide 18 with both ends open, and when the booster plunger guide 18 is threadedly connected to the injection plunger guide 17,
The injection plunger bore 3 is offset
2.

In addition, the booster plunger guide 18 is
A follower guide sleeve portion 34 is formed at the upper end thereof and is coaxial with the booster plunger bore 33.
Pumping spring 36
The spring seat is 35.

The nozzle needle 12 is seated on the valve seat 21 of the nozzle 15 and is slidably disposed in the needle spindle bore 20 thereof.

The nozzle needle 12 also has a pin 37
The pin 37 protrudes coaxially from the upper end, passes through the pin hole 28 of the pressure spring guide 16, and the tip of the pin contacts the spring seat 30 disposed within the pressure spring chamber 27, so that the pressure spring It is pressed against its valve seat 21 by a pressure spring 29 located within the chamber 27.

The booster plunger 13 has a booster plunger bore 3 on the side of the injection plunger bore 32 communicating with the injection plunger bore 32.
a first stage injection cut-off port reciprocally slidably disposed within and open to the booster plunger bore 33 to form a booster pumping chamber 38 within the booster plunger bore 33; 39 and main injection cut
Open and close off port 40.

The booster plunger 13 has an annular injection cut-off groove 41 formed on its outer peripheral surface at a predetermined position on the lower end side, and has one end opened at the lower end and the other end in the injection cut-off groove 41. A communication channel 42 is provided to communicate the booster pumping chamber 38 with the first stage injection cut-off port 39 and the main injection cut-off port 40 during pumping operations.

The booster plunger 13 is also connected at its upper end to a follower 59 which is reciprocatably slidably fitted into the follower guide sleeve portion 34. Of course, the follower 59 is extended outside the guide sleeve portion 34 and forms a flange at its extended end for the pumping spring 36.

The injection plunger 14 forms an injection pumping chamber 45 in its injection plunger bore 32 on the side of its fuel reservoir 24 and also communicates with its injection plunger bore 32 in cooperation with its booster plunger 13 . is reciprocally slidably disposed within the injection plunger bore 32 to form a booster pumping chamber 38 within the booster plunger bore 33 and responsive to pumping action of the booster plunger 13. , reciprocates within the injection plunger bore 32 to open and close a spill port 46 opened to the injection plunger bore 32.

A fuel feed canal 47 extends from its injection plunger guide 17 to its booster plunger guide 18 and has one end connected to its injection pumping guide 18.
It is opened in the chamber 45, and the other end is connected to the connection port 43 of the booster plunger guide 18, so that it spans the injection plunger guide 17 and the booster plunger guide 18.

The fuel feed canal 47 also includes a check valve 48 on the injection pumping chamber 45 side of the injection plunger guide 17.
A fuel feed canal branch 49 is branched downstream of the check valve 48.
Of course, this fuel feed canal branch 4
9 is connected to its pressure canal 31 formed in its pressure spring guide 16.

The fuel feed canal 47 so formed has its connection port 43 connected to the feed pump 52 via a fuel line 54 so that it can be connected to the fuel reservoir, i.e. from the fuel tank (not shown). The injection pumping chamber 45 can be supplied with fuel.

A fuel feed canal 50 is formed in the booster plunger guide 18 and is connected to the first stage injection cut.
Off port 39 and main injection cut-off port 40 are connected to connection port 44 . Of course, the connection port 44 is connected to the feed pump 53 via a fuel line 55, allowing fuel to be supplied to the booster pumping chamber 38 from a fuel tank (not shown).

A spill fuel communication channel 51 is formed in the injection plunger guide 17 and connects one end to the spill port 46 and the other end to the pressure spring chamber 27, and at the end of fuel injection, the high pressure in the booster pumping chamber 38 is connected. Fuel, ie, relief fuel pressure oil, is directed into the pressure spring chamber 27 to improve the shutoff of its nozzle needle 12. That is, as such, the spill fuel communication channel 51 directs high relief oil pressure into the pressure spring chamber 27 to improve fuel depletion.

The spill fuel communication channel 51 is connected to a fuel tank (not shown) via a spill fuel pipe 56.
The spill fuel pipe 56 is connected to the return port of the fuel tank, and the spill fuel pipe 56 has a solenoid valve 57 arranged therein.

The solenoid valve 56 is opened and closed by an electrically connected control unit 58.

The control unit 58 is electrically connected to an engine speed sensor 61, an accelerator position sensor 62, etc. arranged in the diesel engine, and in other words, the engine The output current for opening and closing the solenoid valve 57 is controlled according to the rotation speed, load, etc. In order to prevent excessive back pressure from being applied to the nozzle needle 12, the solenoid valve 57 is opened and high-pressure fuel is pumped into the booster. The system controls the amount of high-pressure fuel released from the pumping chamber 38 to the fuel tank via the spill fuel pipe 56, and thus controls the amount of high-pressure fuel released.
It consists of an arithmetic circuit and a control circuit.

Follower 59 is booster plunger guide 1
8, the lower end is connected to the booster plunger 13, and the extended end extends outwardly of the follower guide sleeve portion 34, i.e. A flange 60 is formed at the upper end.

The follower 59 so formed receives a rocker arm (not shown) at its upper end and also receives one spring end of the pumping spring 36 at its flange 60.

The pumping spring 36 is a coil spring and is attached to the flange 60 of the follower 59.
and booster plunger guide 18 spring.
The spring end is positioned between the seat 35 and the follower guide sleeve portion 34 and around the follower extension end so that the locker
It cooperates with the arm to provide a reciprocating or pumping motion to its booster plunger.

Next, to explain the operation of the above-mentioned unit injector 10, when the diesel engine is currently operating, fuel is pumped through the feed pump 52,
53, the booster plunger 13 is guided from the fuel tank to the fuel feed canals 47, 50 via fuel pipes 54, 55, and is connected to the follower 59. The rocker is swung through the push rod.
The arm and pumping spring 36 slide reciprocally within the booster plunger bore 33, and the control unit 58
is electrically connected to the electromagnetic coil of the electromagnetic valve 57, so the output current for opening and closing the electromagnetic valve 57 is changed according to signals from the rotation speed sensor 61, accelerator position sensor 62, etc.
Since the solenoid valve 57 is controlled to open and close, when the booster plunger 13 is moved upward,
The fuel is directed from the fuel feed canal 50 into the booster pumping chamber 38, and the upward movement of the booster plunger 13 causes the injection plunger 14 to move upward, so that the fuel is A fuel feed canal 47 is directed into the injection pumping chamber 45 .

Next, when the booster plunger 13 is moved downward, the fuel in the booster pumping chamber 38 is compressed, and as the fuel is compressed, the injection plunger 14 is moved downward, and the fuel in the booster pumping chamber 38 is compressed. The fuel in the injection pumping chamber 45 is compressed by its injection plunger 14 and is compressed by the fuel feed canal branch 49, the fuel feed canal 4 downstream of the check valve 48.
7, and pressure canals 31 and 25, to the fuel reservoir 24. When the pressure in the fuel reservoir 24 reaches a predetermined pressure, the nozzle needle 12 is lifted against the pressure spring 29, and the fuel flows into the nozzle. The fuel is injected in the form of mist from 22 and 23, and so-called first-stage injection is performed.

Further, when the booster plunger 13 is moved downward and the injection cut-off groove 41 is connected to the first stage injection cut-off port 39, the pressurized fuel in the booster pumping chamber 38 is transferred to the communication channel. 42, and injection cut
As the fuel escapes through the off groove 41 to the fuel foot canal 50 side, the pressure inside the booster pumping chamber 38 decreases, and as a result,
The pressure in the fuel reservoir 24 is also reduced, and the first-stage injection ends.

Further, when the booster plunger 13 is moved downward, the communication between the injection cut-off groove 41 and the first stage injection cut-off port 39 is cut off, and the fuel in the booster pumping chamber 38 is compressed again. , as the fuel is compressed, the injection plunger 14 is moved downward again,
The fuel in the injection pumping chamber 45 is
The fuel is compressed again by the injection plunger 14, flows into the fuel reservoir 24, lifts the nozzle needle 12 against the pressure spring 29, and is injected in the form of mist from the injection ports 22 and 23, thus performing the so-called main injection. It will be done.

Furthermore, when the booster plunger 13 is moved downward, the injection cut-off groove 41 is connected to the main injection cut-off port 40, and
The injection plunger 14 is then moved further downwardly, opening the spill port 46 so that the high pressure fuel in its booster pumping chamber 38 is transferred to the communication channel 42 and the injection cut.
A portion of the high pressure fuel escapes to the fuel feed canal 50 side through the off groove 41, and a portion of the high pressure fuel passes through the spill fuel communication channel 51 to the pressure spring.
The high-pressure fuel, i.e. spill fuel pressure, is introduced into the chamber 27 and acts as a back pressure on the nozzle needle 12.
Increase the cut-off speed to improve fuel exhaustion. Of course, the spill fuel pressure is detected by the engine speed sensor 61 and the accelerator position sensor 62.
The control unit 58 drives the solenoid valve 57 to open and close it in response to signals from the solenoid valve 57, and so on. In other words, the cut-off speed of the nozzle needle 12 is
It is optimally controlled by spill fuel pressure, that is, back pressure, which is controlled according to engine speed, load, etc.

In that way, the high pressure fuel in the booster pumping chamber 38 is vented, so that the nozzle needle 12 is pressed against the valve seat 21 and its orifices 22, 23 are closed, terminating the main injection.

The unit injector 10 periodically repeats the above-described operation by means of the rocker arm and the pumping spring 36, which are swung as the cam shaft rotates.

As understood from the above, the unit injector of the present invention includes a booster plunger fitted in a reciprocally slidable manner on the open side of the plunger bore, and a first stage injection cut opened in the plunger bore. an injection plunger is reciprocatingly slidably fitted into its plunger bore which opens and closes the off port and the main injection cut-off port, and which is closed by the booster plunger; Chamber and booster pumping
The booster, pumping,
The chamber opens and closes a spill port opening into the plunger bore, a spill fuel communication channel connects the spill port to the pressure spring side of the needle spindle bore, and a solenoid valve opens and closes the spill port opening into the plunger bore. The control unit is located in the spill fuel line connecting the port to the fuel reservoir and controls the amount of high-pressure fuel that escapes from the booster pumping chamber to the fuel reservoir; Since the current flowing through the solenoid valve is controlled according to the signals from the sensor and the load sensor, the unit injector of the present invention uses the booster pumping pressure as the back pressure of the nozzle needle at the end of fuel injection. The pressure of high-pressure fuel spilled from the chamber is controlled by opening and closing the solenoid valve, and the back pressure from the spilled fuel increases the closing speed of the nozzle/needle, and the spill pressure of the fuel increases the secondary fuel injection is prevented, high-pressure injection of fuel is possible, fuel starvation at the end of fuel injection is improved, desired fuel injection quantity and injection timing is obtained, engine performance of diesel engines is improved, and in addition, the structure is improved. It is simplified and miniaturized, and can be easily attached to the cylinder head of a diesel engine, and the structure around the cylinder head is simplified.

As mentioned above, from the specific examples of the present invention explained with reference to the drawings, those who have ordinary knowledge in the technical field to which this invention pertains will understand the following:
Various design modifications and changes can be easily made, and furthermore, the content of this invention is essential to the realization of the invention that accomplishes the task of the invention,
It is derived from the technical essence of the invention, which is the nature of the invention, and can be easily replaced by an embodiment that is objectively recognized as incorporating it.

[Brief explanation of drawings]

The figure is a longitudinal sectional view showing a specific example of the unit injector of the present invention used in a diesel engine. DESCRIPTION OF SYMBOLS 10... Unit injector, 11... Pump body, 12... Nozzle needle, 13... Booster plunger, 14... Injection plunger, 15...
Nozzle, 16...Pressure spring guide, 17...Injection plunger guide, 18...Booster plunger guide, 24...Fuel reservoir, 25, 31...Pressure canal, 29...Pressure spring, 36...Pumping
Spring, 38... Booster pumping chamber, 39... First stage injection cut-off port, 4
0... Main injection cut-off port, 41... Injection cut-off groove, 42... Communication channel, 45... Injection pumping chamber, 46... Spill port, 47, 50... Fuel feed canal, 51
...Spill fuel communication channel, 52, 53...Feed pump, 57...Solenoid valve, 58...Control unit.

Claims (1)

Claims: 1. A needle spindle bore 20 having a valve seat 21 and nozzles 22, 23, with one end open and the other end communicating with a fuel reservoir 24 of the needle spindle bore 20. a pump body 11 with plunger bores 32, 33; a nozzle needle 12 fitted in its needle spindle bore 20 and seated in its valve seat 21 with a pressure spring 29; 32, 33 so as to be reciprocatingly slidable, and opens and closes the first stage injection cut-off port 39 and the main injection cut-off port 40, which are opened in the plunger bores 32, 33. A booster plunger 13 and a plunger bore 3 which is reciprocally slidably fitted into the plunger bores 32 and 33 closed by the booster plunger 13;
An injection pumping chamber 45 is installed on the fuel reservoir 24 side of 2, 33, and the plunger bore 3
A booster pumping chamber 38 is formed on the side of the booster plunger 13 of Nos. 2 and 33, respectively.
The injection plunger 14 opens and closes the spill ports 46 opened in the plunger bores 32 and 33, and the injection pumping chamber 45 is provided with a check valve 48 on the side of the injection pumping chamber 45. A fuel feed canal 47 connecting to the feed pump 52 and a pressure canal 25 , 31 downstream of the check valve 48 of the fuel feed canal 47 connecting the injection pumping chamber 45 to the fuel sump 24 . and a fuel feed canal 5 connecting the first stage injection cut-off port 39 and the main injection cut-off port 40 to the feed pump 53.
0, a spill fuel communication channel 51 connecting the spill port 46 to the pressure spring 29 side of the needle spindle bore 20, and a spill fuel piping 56 connecting the spill port 46 to the fuel reservoir. ,and,
Controls the amount of high pressure fuel that escapes from the booster pumping chamber 38 to the fuel reservoir.