JPH0214543B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The industrial field of application of the invention is fuel injection devices for internal combustion engines. That is, the present invention is as described in Swiss Patent No. 447714,
a fuel pump conveying fuel under constant high pressure to a pressure chamber adjacent to the valve seat of the injection valve via a pressure conduit; a free piston device inserted in the pressure conduit; and a closure means. A fuel injection device for an internal combustion engine, comprising a control device for producing an opening and closing movement of a valve needle pressed against a valve seat, the device moving in a cylinder bore of said free piston device against the force of a return spring. The possible free piston makes a stroke approximately proportional to the amount of fuel injected after each injection and is pushed back to its starting position by a return spring during injection pauses, and the free piston arrangement It has a throttle channel connecting the two piston faces, and the control device is designed to control an electrical adjustment member that determines the injection period of the injection valve.

In the conventional technology, in such a fuel injection device, the fuel in the pressure chamber of the injection valve is continuously maintained at a constant high pressure sent from the fuel pump, and the injection time is determined by the connection of at least one electromagnetic control valve. Determined by time. A free piston, which is inserted in the pressure line and which performs a stroke related to the injected fuel quantity each time an injection takes place, serves in this case as a safety device, for example in the event of a malfunction of the solenoid control valve or a jamming of the valve needle. If the amount of fuel injected exceeds the maximum allowable value by a certain limit,
It merely cuts off the supply of fuel to the injection valve.
This fuel injection device has an electromagnetically operated control valve.
This has the disadvantage that the start of the injection as well as the end of the injection, that is, the injection quantity, are dependent on the opening time of this control valve, which is controlled in relation to the internal combustion engine crankshaft. This causes a problem that the injection amount becomes inaccurate, especially in the case of an internal combustion engine that rotates at high speed. Furthermore, the free piston used in known fuel injection devices always limits the fuel injection amount to some extent above the maximum permissible amount, even during idling and part load conditions. In other words, the internal combustion engine may rotate at excessively high speeds despite the safety devices in place.

Therefore, the problem to be solved by the present invention is to separate the injection end control from the injection start control and accurately adjust the injection amount on the high pressure side.

The solution according to the invention provides a fuel injection device of the type described above, in which the control device includes an injection start signal generator, a free piston of the free piston device, an electrical distance signal generator, and a control device. an electrical distance signal generator for contactlessly measuring the metering stroke of a free piston serving as a metering member, which is approximately proportional to the amount of fuel injected; The output signal of the control device is supplied to the control circuit, and the output signal of the control device is
A switching element constituted by the electrical distance signal generator and an associated part of the control circuit is actuated, whereby a control signal is supplied from the control circuit to the electrical adjustment member for initiating a valve needle closing movement. The present invention is characterized in that, at the start of injection, the electrical adjustment member is controlled by an injection start signal generator.

According to an embodiment of the invention, the free piston is therefore the metering member of the control device and the closing movement of the valve needle is controlled by a switching element of the control device which is actuated by its stroke. , since the start of injection is carried out by an injection start signal generator in a known manner, independently of the end of injection.
Unlike the prior art, there is an effect that the control of the end of injection is separated from the control of the start of injection.

In the following, the structure of the present invention will be explained in detail with reference to the embodiment shown in the drawings. The first embodiment shown schematically in FIG. 1 has an auxiliary controlled injection valve 10. , this injection valve is supplied with fuel under constant high pressure from a fuel pump 13 via an accumulator 11 and a pressure line 12 . If the magnitude of the injection pressure and the dimensions of the conduit are set appropriately, the pressure conduit 12 can also perform the function of the accumulator 11.

Fuel sent from the fuel pump 13 at injection pressure is sent from the pressure conduit 12 to the pressure chamber 1 adjacent to the valve seat 14.
Reach within 5. A pressure receiving shoulder surface 16 of a valve needle 17 configured as a differential piston protrudes into this pressure chamber.
The valve needle 17 is loaded in the opening direction by the fuel pressure acting on the valve 6 . . When the valve needle 17 is in the closed position as shown, it is pressed against the valve seat 14 by the control piston 18, which has a larger outer diameter. The required closing pressure is determined by the control piston 18
This is produced by the fuel at the injection pressure supplied into the control pressure chamber 19 above the control pressure chamber 19. This control pressure chamber 19 is connected via a control pressure line 21 to the pressure line 12 under the injection pressure; if the control piston 18 is correspondingly enlarged, it can absorb the pressure reduced by the pressure reducing valve. It can also be supplied. Of course, a separate fuel pressure or hydraulic pressure source can also be connected to the control pressure line 21. Injection valve 1
In the head 22a of the housing 22 of 0, a control valve 24 belonging to the control device 23 is inserted into the control pressure line 21 and in the starting position shown, which is produced by the return spring 25, is closed in this case. A pressure line 12 serving as a pressure source is connected to a control pressure chamber 19 . The control valve 24 is an electromagnetic 3-port 2
It is designed as a position valve and is equipped with an electromagnet 26 which, when energized, assumes a second switching position and which opens the control pressure chamber 19 into a relief conduit 28 as a low-pressure chamber. 27
Connect to. The fuel pump 13, which is designed as a high-pressure conveying pump, draws fuel from a fuel tank 28.

A free piston arrangement 31 is inserted into the pressure conduit 12, in whose cylinder bore 32 a free piston 33 is slidably guided. This free piston 33, which is returned to the illustrated starting position by means of a return spring 34 during the injection pause period, performs a stroke H that is dependent on the amount of fuel injected for each injection. In this case, the two piston faces of the free piston 33 are connected to each other by a throttle channel 35. This throttle passage 35 can be kept extremely narrow. This is because, inter alia, in the case of diesel engines the ratio of the injection pause period to the injection time is at least 35:1. Thereby, it is possible to assume that the stroke H of the throttle passage 35 is proportional to the amount of injected fuel.

The stroke H of the free piston 33 is measured by an inductive distance signal generator 36 . The distance signal generator 36 is schematically indicated by an outer transmitter coil 37. The free piston 33 is connected to the control device 23
It constitutes a metering member. That is, when a metering stroke H1 proportional to a predetermined fuel injection amount is performed, a distance signal SW is supplied from the distance signal generator 36 to the control circuit 38, and the control circuit 38 performs control to cause the valve needle 17 to perform a closing movement. A signal SI is supplied to the electromagnet 26. In this case, the inductive distance signal generator 36 and the associated parts of the control circuit 38 are connected to the switching element 39 of the control device 23, which determines the end of injection.
It consists of

To control the end of the injection, the excitation of the electromagnet 26 is interrupted in the illustrated embodiment and the control pressure chamber 19 is supplied with fuel pressure which causes a closing movement of the valve needle 17. The initiation of the injection takes place periodically by an injection signal generator 41 driven in conjunction with the internal combustion engine crankshaft, in which case the control signal SI of the control circuit 38 supplying the electromagnet 26 with a separate It is also possible to modify the motion data B1, B2.

Instead of the control valve configured as a 3-port 2-position valve in the embodiment of FIG. 1 serving as the electrical regulating element, it is also possible to use two 2-port 2-position valves (not shown), in which case The first control valve controls the connection between the control pressure chamber 19 for starting the injection and the relief conduit 27, and the second control valve, operated by a switching element 39, controls the control pressure chamber 19 at the control pressure. It merely connects to the conduit 21 to terminate the injection. Switching element 39 according to the invention
The free-piston device 31 with a 2-pin is suitable for controlling magnetic injection valves in which the valve needle is actuated directly by an electromagnetic coil against the force of a closing spring, as in the case of gasoline injection devices. can also be used. In such magnetic injection valves, the control device according to the invention serves to simplify the electronic control device (not shown).

FIG. 2 shows parts of a second embodiment that are different from the fuel injection system shown in FIG. 1. In this FIG. 2 and FIG. , and parts with the same function but different structures are indicated by the same reference numerals with a dash.

Since the time available for the return stroke of the metering member free piston is approximately 35 times greater than the injection time, at least two injection valves 10' and 1
0'' to a common pressure conduit 12, control pressure conduit 21 and relief conduit 27,
In this case for both injection valves 10' and 10'',
Only one free piston device 31' for controlling the end of injection needs to be provided. Free piston device 3
1' free piston 33' has its central threaded hole 45
It has a transmitting pin 46 screwed into the transmitter pin 46 . This sending pin 46 is connected to the return spring 3 in the cylinder hole 32.
It protrudes into the transmitter coil 37' in the cylinder chamber 47 containing the transmitter coil 3.
In cooperation with 7', an inductive distance signal generator 36' is constructed. Distance signal generator 36' and control circuit 3
The related portion of 8 constitutes a switching element 39'. The control circuit 38 generates a first control signal SI1 which determines the end of injection for the injection valve 10' and a second control signal SI2 which operates the electromagnet 26 of the control valve 24 of the second injection valve 10''. In other respects, the function and mode of operation of the fuel injection device are the same as in the first embodiment shown in FIG. 1.The first injection valve 10' is different from the injection valve 10 shown in FIG. The only difference is that there is no control piston 18 serving as a closing means, and in FIG. and, by extension, as a means of closure.
In order to ensure that the valve needle 17' can be closed reliably and quickly from the open state, the section 12 of the pressure conduit 12 inside the valve casing 22 is
A throttle 48 is inserted in a, thereby creating the pressure drop towards the pressure chamber 15 necessary for a sufficiently rapid closing movement of the valve needle 17'. Instead of this, in the second injection valve 10'' a closing spring 49 is inserted inside the control pressure chamber 19, which serves as a closing means, so that the restriction in the pressure line 12 is omitted. ing.

The start of injection for both injection valves 10' and 10'' takes place via the control circuit 38 from a slightly varied injection start signal generator 41 with a corresponding angle offset, and the end of injection for both is controlled by a free piston 33' common to the injection valves.
The throttle passage 35', which allows the return stroke of the free piston 33', is formed off-center, and the first
The dimensions are different from the throttle passage 35 shown in the figure. In order to adjust the distance signal SW taken out by the transmitter coil 37' of the distance signal generator 36', the position of the transmitting pin 46 in the free piston 33' is changed and fixed by the locking nut 51. be able to.

The control device with the switching element 39' and the control valve 24, as shown by extending the pressure conduit 12, the control pressure conduit 21 and the relief conduit 27 with chain lines, has the following characteristics in the case of an internal combustion engine with a low rotational speed: At least one further injection valve can also be operated.

In the third exemplary embodiment shown in FIG. 3, an injection valve 60 configured as a double nozzle is auxiliary controlled in the same way as the injection valve already described, so that the two valve needles 61 and 62 are each It is controlled by two control valves 24. These two valve needles 61 and 62 control the injection of fuel from a common pressure chamber 15 which is supplied via the pressure conduit 12, in this case only one free piston for both valve needles 61 and 62. Device 31 comes into play. As a result, when the valve needles 61 and 62 are sequentially controlled in the opening direction, no sudden changes in the injection quantity occur. This is because the injection quantity is dependent on the stroke speed of the free piston and the end of injection is dependent on the end of injection signal generated by switching element 39. The two valve needles 61 and 62 can be operated in a known manner one after the other for shaping the desired injection curve, alternately or together for controlling the injection cross section.

The free piston arrangement, which is not shown in detail in FIG. 3, can be constructed like the free piston arrangement 31 or 31' shown in FIGS. 1 and 2.

Since the present invention is constructed as described above, the control of the end of injection is separated from the control of the start of injection by the crankshaft of the internal combustion engine, and the free piston device is inserted in a pressure conduit for conveying fuel. This is achieved by means of a free piston, and has the remarkable effect that the injection quantity is metered very accurately on the high-pressure side even when the internal combustion engine rotates at high speeds.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the first embodiment, FIG. 2 is a schematic diagram of the second embodiment, and FIG. 3 is a schematic diagram of the third embodiment. 10, 10', 10''...Injection valve, 11...Accumulator, 12...Pressure conduit, 12a...Part, 13...Fuel pump, 14...Valve seat, 15...
...Pressure chamber, 16...Pressure shoulder surface, 17, 17', 1
7″...Valve needle, 17a′...part, 18...
Control piston, 19... Control pressure chamber, 21... Control pressure conduit, 22... Casing, 22a... Head, 23 and 23'... Control device, 24... Control valve, 25... Return spring, 26 ......Electromagnet, 27
... relief conduit, 28 ... fuel tank, 31 and 31' ... free piston device, 32 ... cylinder bore, 33 and 33' ... free piston, 34 ...
Return spring, 35, 35'... Throttle passage, 36, 3
6'... Distance signal generator, 37, 37'... Transmitter coil, 38, 38'... Control circuit, 39, 3
9'...Switching element, 41...Injection start signal generator, 45...Screw hole, 46...Sending pin, 47
... Cylinder chamber, 48 ... Throttle, 49 ... Closing spring, 51 ... Stopping nut, 60 ... Injection valve, 61
and 62... Valve needle, B1 and B2... Operating data, H... Stroke, H1... Metering stroke, SW... Distance signal, SI, SI1, SI2... Control signal.

Claims (1)

[Claims] 1. Valve seat 14 of injection valve 10, 10', 10'', 60
a fuel pump 13 conveying fuel under constant high pressure to a pressure chamber 15 adjacent to the pressure chamber 15 via a pressure line 12; a free piston arrangement 31, 31' inserted in said pressure line; Valve needles 17, 17', which are thus pressed against the valve seat;
17'', 61, 62, and a control device 23, 23' for producing the opening and closing movements of the piston device 17'', 61, 62, the force of the return spring 34 in the cylinder bore 32 of said free piston device. The free pistons 33, 33', which are movable against the pressure, perform a stroke H approximately proportional to the amount of fuel injected each time an injection is performed, and are pushed back to the starting position by a return spring during the injection pause period. and the free piston device has a throttle passage 35, 35' connecting the two piston faces of the free piston, and the control device determines the injection period of the injection valve 10, 10', 10'', 60. In the type that controls the electrical adjustment member 24, the control device 23, 23'
However, the injection start signal generator 41, the free piston devices 31, 31', the free pistons 33, 33', the electrical distance signal generators 36, 36', and the control circuit 3
8, 38', and when the free piston 33, 33' serving as a metering member performs a metering stroke H1 approximately proportional to the amount of fuel injected, this metering stroke is carried out without contact. The output signals of the electrical distance signal generators 36, 36' to be measured are supplied to the control circuits 38, 38', and the control device 2
3, 23', said electrical distance signal generator 36, 3
6' and the associated parts of the control circuits 38, 38' are actuated, whereby the valve needles 17, 17', 1
A control signal SI for starting the closing movement of 7'', 61, 62 is supplied from the control circuit to the electrical regulating member 24, which is controlled by the injection start signal generator 41 at the start of injection. A fuel injection device for an internal combustion engine, characterized in that: 2. Auxiliary controlled injection valves 10, 10', 10'',
60 valve needles 17, 17', 17'', 61, 6
2 is a pressure-receiving shoulder surface 16 disposed in the pressure chamber 15 and loaded in the opening direction by fuel pressure, and a control piston 17a provided at the end of the valve needle on the side opposite to the valve seat 14. ', 18,
The control pressure chamber 19 of the control piston is connected to the control pressure conduit 2 by means of at least one electrical regulating member, the control valve 24, for actuating the valve needle.
1 or connected to a chamber of low pressure via a relief conduit 27.
The fuel injection device described in Section 1. 3. The electrical distance signal generator 36' of the switching element 39' has a transmitter coil 37' arranged in a cylinder chamber 47 containing a return spring 34, in which 3. The fuel injection device according to claim 1, wherein during the metering stroke H1 of the free piston 33', a transmitting pin 46, which is adjustable and fixed in the free piston 33', projects.