JPH0514104B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a fuel injection pump for an internal combustion engine, in which each engine cylinder is provided with one fuel injection valve, and the valve needle of the fuel injection valve is , the fuel reservoir of the fuel injection valve is moved in the opening direction by the pressure of the supplied fuel against the force of the closing spring, and the fuel reservoir of the fuel injection valve is connected to the pumping operation of the fuel injection pump via the supply conduit. a fuel supply conduit connected to a chamber, the pump working chamber having a volume that allows accommodation of a maximum amount of injected fuel, and having a check valve that opens only in the direction of the pump working chamber; The fuel feed pump is always connected to the fuel feed pump via the fuel feed pump, and the discharge pressure of the fuel feed pump is constant and set lower than the opening pressure of the fuel injection valve, and the fuel is supplied from the pump working chamber of the fuel injection pump.
The fuel injection valve can be supplied with a pressure transmission piston operable by pressurized air in the cycle of the internal combustion engine, the pump working chamber being formed by the pump cylinder, and the pressure transmission piston being connected to the pump. A discharge piston is provided which slides within the cylinder and delimits the pump working chamber, the discharge piston having, on the side opposite the pump working chamber,
A large diameter servo-piston is provided that slides within the pressure cylinder, the servo-piston delimiting a pneumatic chamber located opposite the discharge piston, the pneumatic pressure chamber being actuated by an electromagnetic actuator. a pressure relief conduit connected to the outlet of a two-way switching control valve of the type and, via said two-way switching control valve, being connected to an air tank for actuating a pressure transmitting piston, or by switching a pressure relief conduit; Concerning a type of thing that has become connected to.

Prior Art In the above-mentioned fuel injection device known from German Patent Application No. 2012202, a switching valve is used to supply fuel discharged from a fuel supply pump to a pressure chamber via a servo piston. is being supplied in a controlled manner. A pump plunger cooperating with a servo piston provides fuel pressure during the injection operation, which is again controlled by the switching valve. Only after the injection start time controlled by the switching valve does this fuel pressure become sufficient to move the valve needle of the fuel injector in the opening direction against the force of the closing spring. rise until. However, in this case already immediately after the start of the opening movement of the valve needle, fuel can flow into the combustion chamber, so that
At this time, the opening pressure drops again, and the valve needle does not move quickly to the fully open position, and there is a risk that the valve needle may remain in a halfway position during the injection process.

Means to be Solved by the Invention Therefore, an object of the present invention is to improve the fuel injection device of the type mentioned at the beginning, to make the fuel injection start timing independent of the formation of the injection pressure, and to make the fuel injection start timing independent of the formation of the injection pressure. It is an object of the present invention to provide a fuel injection device that can supply a desired injection pressure to an injection valve and maintain this injection pressure until the end of an injection process.

Means for Solving the Problem In order to solve this problem, the configuration of the present invention includes:
In a fuel injection device of the type mentioned at the outset, an air tank is continuously supplied with pressurized air by an electromagnetically actuated compressor in order to supply the pressurized air chamber with pressurized air via a two-way control valve. is provided, and the supply conduit between the pump working chamber and the fuel injection valve is operated during the cycle of the internal combustion engine.
Opening and closing can be controlled using a front valve that can be switched arbitrarily during the pressure load time of the air pressure chamber controlled by a two-way switching control valve. With the aid of a pressure relief valve placed in the front end, pressure relief can be achieved after the front valve has been closed.

Effects of the Invention With the configuration of the present invention, the pressure already generated using the discharge piston before the start of injection can be continuously supplied to the fuel injection valve even after the pre-valve is opened. Moreover, since this pressure is maintained over the entire injection period, which ends with the closing of the pre-valve, it is necessary to open the fuel injector suddenly at the start of injection and to close the valve needle to its full extent during the entire injection period. It is possible to keep it in the open position.
Furthermore, instead of using a supply device actuated by fuel pressure as in the prior art to supply pressurized air to the pressurized air chamber, ie to actuate the pressure transfer piston, the invention uses an electromagnetically actuated compressor. By using an air tank that is continuously supplied with pressurized air by a pump, control can be carried out reliably and easily.

Example Next, embodiments of the present invention will be described with reference to the drawings.

In the drawings, conduits carrying fuel are shown as double lines with alternating black and white sections, while conduits carrying air are shown as double white lines and conductors carrying current are shown as single lines. has been done. Furthermore, the arrows drawn in the drawings indicate the direction of fuel flow or air pressure in the fuel and air conduits, and the direction of signal transmission in the case of electrical conductors.

The drawing shows a fuel injection valve assigned to an engine cylinder as part of the illustrated fuel injection system for an internal combustion engine. The valve needle 2 of this fuel injection valve is movable in the opening direction against the force of the closing spring 3 by the force of the fuel supplied to the fuel reservoir 4 via the supply conduit 5 . According to the invention, the fuel injection valve is provided with a pump working chamber 6 for accommodating the amount of fuel to be injected. The pump work chamber 6 is connected to a fuel feed pump 8, preferably driven by an electric motor 7, from which it is continuously supplied with fuel. The discharge pressure of the supplied fuel is set lower than the opening pressure of the fuel injection valve 1. Fuel is supplied from the pump work chamber 6 to the fuel injection valve 1 via a pressure-transmitting piston 9 which is actuated pneumatically in accordance with the engine cycle.
Conduit 10 between pump working chamber 6 and fuel injection valve 1
A front valve 11 is installed to control the opening and closing of the conduit 10 in accordance with the engine cycle. The line 10 is furthermore branched off from the line 10 by means of a pressure relief valve 12 which is downstream of the upstream valve 11 in the flow direction in each case after the closing of the upstream valve 11 and which returns the fuel to the fuel tank 13. The pressure is released through a pressure conduit 14.

The pump working chamber 6 is formed by a pump cylinder 15 in which the delivery piston 16 of the pressure-transmitting piston 9 operates. Behind the discharge piston 16 is a large-diameter servo piston 1 that works in a pressure cylinder 17.
8 is connected, and this servo piston 18 cooperates with the wall of the pressure cylinder 17 to open the air pressure chamber 19.
is restricted. A conduit 10 branches off from the pump cylinder 15 on the one hand, and a fuel supply conduit 20 opens into the pump cylinder 15 on the other hand. The fuel supply conduit 20 branches off from a fuel conveying conduit 21 which is connected to the outlet of the fuel feed pump 8 and serves to supply all fuel injection valves with fuel. The fuel conveying conduit 20 is allowed to pass only in the fuel supply direction, and therefore, the fuel conveying conduit 21 is allowed to pass from the pump working chamber 6 during the discharge stroke of the pressure transmitting piston 9.
A check valve 22 is provided to prevent backflow of fuel to. The fuel feed pump 8 sucks fuel from the fuel tank 13 via a filter 23 and a suction conduit 24 and transfers this fuel to the fuel delivery conduit 21 at a pressure approximately 10-20% lower than the opening pressure of the fuel injection valve 1.
Discharge into. A pressure regulating valve 25 is assigned to the fuel feed pump 8 in order to regulate and maintain the desired discharge pressure. This pressure regulating valve 25 is arranged in a pressure monitoring line which branches off from the fuel conveying line 21 downstream of the fuel feed pump 8 and again into the suction line 24 before the fuel feed pump 8 in the flow direction. It's open.

An air tank 26 is provided to supply pressurized air to each air pressure chamber 19, and this air tank 26 is supplied with pressurized air by a compressor 28 driven by an electric motor 27. It's summery. Compressor 28 sucks in the required air via air filter 29 and suction conduit 30 and pumps the compressed air via conveying conduit 31 to air tank 26 . The conveyance conduit 31 includes
Check valve 32 and pressure regulating valve 3 that open in the conveying direction
3 is provided, and the pressure regulating valve 33 is adapted to be adjusted in relation to certain operating factors of the internal combustion engine.

From the air tank 26, all air pressure chambers 1
Air main pipe 3 serving to supply pressurized air to 9
4 is extended. Each air pressure chamber 19 is supplied with pressurized air via an air supply conduit 35 branching from the main air conduit 34 . The air supply conduit 35 is provided with a two-way switching control valve 36 actuated by an electromagnet, the two-way switching control valve 36 having one inlet and two outlets;
In this case, an air supply conduit 35 is connected to the inlet, a pressurization/relief conduit 37 connected to the air pressure chamber 19 is connected to the first outlet, and a pressure relief conduit 38 is connected to the second outlet. . In order to avoid air losses, the air generated when the air pressure chamber 19 is relieved is transferred to the relief conduit 3.
8 and a main collecting conduit 40 to a common air collecting tank 39 , from which an outflow conduit 41 opens into the suction conduit 30 .
The air is sucked in by the compressor 28 through the air. Since the pressure in the air collection tank 39 is higher than atmospheric pressure, the suction conduit 30 is connected to the outflow conduit 41.
One check valve 42, 43, which opens in the suction direction, is provided before and after the opening location. It should be noted in this connection that it is also possible for the air pressure chamber 19 to be depressurized to the atmosphere. From the pump cylinder 15 , that is to say from the pump cylinder region which is not released by the delivery piston 16 of the pressure-transmitting piston 9 during the reciprocating movement of the pressure-transmitting piston 9 , a leakage fuel line 44 , which leads to the fuel tank 13 , branches off. . This leakage fuel conduit 44
is provided with a pressure regulating valve 45, which is adjusted so that the leakage fuel pressure is equal to or higher than the opening pressure of the fuel injection valve.

Conduit 1 between pump working chamber 6 and fuel injection valve 1
0, a pressure monitoring device 46 is connected behind the upstream valve 11 in the flow direction. This pressure monitoring device 46 has an alarm device 47 to signal possible irregularities in the injection process and/or can trigger an emergency shutdown procedure and has a microprocessor to control the fuel injection. It may also be connected to an electronic regulation and control device 48 specific to the device.

The front valve 11, the pressure relief valve 12 and the two-way control valve 36 are each actuated by an overexcited lifting magnet, which lifts the pressure regulating valve 33 and, if necessary, the fuel. Another two pressure regulating valves 2 of the injector
Similar to 5 and 45, electronic adjustment and control device 48
Control commands are given by. The pressure regulating valve 33 is adjusted in this case in relation to operating factors of the engine, such as rotational speed, intake pressure or the like, so that each air pressure chamber 19 is supplied with air depending on the current or desired operating conditions of the engine. Air is supplied at the appropriate pressure each time. This variable air pressure ensures a suitable influence on the injection process on the fuel side and thus adaptation of the injection process to the current or desired operating conditions of the engine.

The mode of operation of the fuel injection device according to the invention will now be described on the basis of a complete injection cycle. The starting position is assumed as follows. The pump work chamber 6 is already filled with fuel, the prevalve 11 is in the closed position, the pressure relief valve 12 is in the open position, and the two-way control valve 36 is switched for pressure relief. occupying a position. As a result, the air pressure chamber 19 is depressurized and, furthermore, air at the desired pressure is present at the inlet of the two-way control valve 36.

When it is desired to carry out an injection process, a pulse signal is sent from the regulator and control device 48 via a control line 49 to the two-way control valve 36;
A lifting magnet connected to pulls the two-way switching control valve 36 into the flow-through position shown in the drawings. Thereby, the pressurized air present in the air supply conduit 35 at the inlet of the two-way control valve 36 is supplied to the air pressure chamber 19 via the pressurization and pressure relief conduit 37. At the appropriate time, a pulse signal is sent from the regulator and control device 48 via the control line 50 to the lifting magnet of the front valve 11, so that the front valve 11 is opened and the fuel line is opened to the pump work chamber 6.
The fuel injection valve 1 is opened from the fuel injection valve 1 via a conduit 10. At the same time, via the control line 51, the pressure relief valve 1 is
A pulse signal is sent to the lifting magnet No. 2, the pressure relief valve 12 is closed and the pressure relief conduit 14 is cut off.
The pressure transmission piston 9 is moved downward in the drawing by the pressurized air in the air pressure chamber 19, and the discharge piston 16 of the pressure transmission piston 9 is moved downward.
pushes the fuel in the pump working chamber 6 out of the pump working chamber 6 and forcefully feeds it to the fuel injection valve 1. As soon as the fuel pressure in the fuel storage chamber 4 of the fuel injection valve 1 exceeds the opening pressure of the fuel injection valve 1, the fuel injection valve 1 opens and the injection process is completed. In this case, the maximum amount of fuel previously stored in the pump working chamber 6 can be injected. At the end of the injection process, the prevalve 11 is closed again and at the same time the regulating and control device 4 is closed.
8 sends a pulse signal via a control line 51 to the lifting magnet of the pressure relief valve 12, so that the pressure relief valve 12 opens and the pressure in the fuel line downstream of the front valve 11 is reduced via the pressure relief line 14. Descend. At the same time, the regulating and controlling device 48 is commanded via a control line 52 to the other lifting magnet of the two-way control valve 36 .
is moved to the pressure release position. In this pressure relief position, the pressurization and pressure relief line 37 is connected to the pressure relief line 38, and the air pressure in the air pressure chamber 19 is reduced via the connected line. The pump working chamber 6 is then refilled with fuel via the fuel supply line 20 and the pressure-transmitting piston 9 is returned to its starting position again. This prepares the fuel injection system for a new injection process.

[Brief explanation of the drawing]

The drawing is a circuit diagram schematically showing the basic structure of a fuel injection device according to the present invention. DESCRIPTION OF SYMBOLS 1... Fuel injection valve, 2... Valve needle, 3... Closing spring, 4... Fuel storage chamber, 5... Supply conduit, 6... Pump working chamber, 7, 27... Electric motor, 8... Fuel feed pump, 9... Pressure transmission piston, 10... conduit, 11
... Front valve, 12 ... Pressure relief valve, 13 ... Fuel tank, 1
4...Pressure conduit, 15...Pump cylinder, 16...Discharge piston, 17...Pressure cylinder, 18...Servo piston, 19...Air pressure chamber, 20...Air supply conduit, 21...Fuel transfer conduit, 22, 32, 42, 4
3... Check valve, 23... Filter, 24... Suction conduit, 25... Pressure regulating valve, 26... Air tank, 28
... Compressor, 29... Air filter, 30... Suction conduit, 31... Conveyance conduit, 33... Pressure regulating valve,
34...Air main conduit, 35...Air supply conduit, 36...
Two-way switching control valve, 37... Pressurization and pressure relief conduit, 3
8... Pressure relief pipe, 39... Air collecting tank, 40... Main collecting pipe, 41... Outflow pipe, 44... Leakage fuel pipe, 45... Pressure regulating valve, 46... Pressure monitoring device, 4
7...Alarm device, 48...Adjustment and control device, 4
9, 50, 51, 52...control conductor.

Claims (1)

[Scope of Claims] 1. A fuel injection device for an internal combustion engine, in which each engine cylinder is provided with one fuel injection valve 1, and a valve needle 2 of the fuel injection valve 1 is configured to inject fuel to be supplied. The fuel storage chamber 4 of the fuel injection valve 1 is moved in the opening direction by pressure against the force of the closing spring, and the fuel storage chamber 4 of the fuel injection valve 1 is connected to the supply conduit 5,
10 to the pump working chamber 6 of the fuel injection device, which pump working chamber 6 has a volume that makes it possible to accommodate the maximum amount of injected fuel, and which has a volume in the direction of the pump working chamber 6. It is always connected to a fuel feed pump 8 via a fuel supply conduit 20 having a check valve 22 that opens only when it is in the opposite direction, and the discharge pressure of the fuel feed pump 8 is constant and lower than the opening pressure of the fuel injection valve 1. and fuel can be supplied from the pump working chamber 6 of the fuel injector to the fuel injection valve 1 by means of a pressure transmission piston 9 actuatable by pressurized air in the cycle of the internal combustion engine, and the pump working A chamber 6 is formed by a pump cylinder 15 , and the pressure-transmitting piston 9 is provided with a delivery piston 16 that slides in the pump cylinder 15 and delimits the pump working space 6 . is provided with a large-diameter servo piston 18 sliding in the pressure cylinder 17 on the side opposite the pump working chamber 6, the servo piston 18 being located on the side opposite the discharge piston 16. The air pressure chamber 19 is connected to the outlet of an electromagnetically actuated two-way switching control valve 36, and via the two-way switching control valve 36, a pressure transmitting piston is connected. 9
A two-way switching control valve 36 is provided in the air pressure chamber 19, in the version that is adapted to be connected to the air tank 26 or, by switching, to the pressure relief conduit 38 for actuating the air pressure chamber 19. An air tank 26 is provided which is continuously supplied with pressurized air by an electromagnetically actuated compressor 28 in order to supply pressurized air between the pump working chamber 6 and the fuel injection valve 1. The supply conduit 10 can be controlled to open and close during the cycle of the internal combustion engine using a front valve 11 which can be switched at will during the pressure load time of the air pressure chamber 19 controlled by the two-way control valve 36. A fuel injection device for an internal combustion engine, characterized in that the pressure can be released after the front valve 11 is closed, using a pressure relief valve 12 located after the front valve 11 when viewed in the fuel flow direction. . 2 A check valve 3 that opens in the conveying direction is installed in the conveying conduit 31 leading from the compressor 28 to the air tank 26.
2 and a pressure regulating valve 33 which is adjustable in relation to the defined operating factors of the internal combustion engine,
A fuel injection device according to claim 1. 3. The pressure relief line 38 of the two-way control valve 36 is connected to a second air tank 39, from which the pressurized air returned via the pressure relief line 38 can be sucked in by the compressor 28. The fuel injection device according to claim 1 or 2, which can be newly introduced into the air tank 26 connected to the two-way switching control valve 36. 4. The front valve 11, the pressure relief valve 12, and the two-way switching control valve 36 are operated by a lifting magnet that is overexcited, and the lifting magnet and the pressure regulating valve 33 are operated by a microprocessor. 4. The fuel injection device according to claim 2, wherein the fuel injection device is controllable by a control signal of an electronic adjustment and control device 48 having a control signal. 5 A pressure monitoring device 46 is connected to the supply conduit 10 between the pump working chamber 6 and the fuel injection valve 1 behind the upstream valve 11 and the pressure relief conduit 14, viewed in the flow direction, and which pressure monitoring device 46 It is claimed that the device 46 is connected to a regulating and controlling device 48 and/or an alarm device 47 to signal irregularities that may occur during the injection process, triggering an emergency shutdown procedure. The fuel injection device according to any one of the ranges 1 to 4. 6. The fuel feed pump 8 is adapted to be driven by an electric motor, and a pressure regulating valve 25 is assigned to the fuel feed pump 8 in order to keep the adjusted discharge pressure constant. 5. The fuel injection device according to any one of items 1 to 5.