EP0235569B1 - Apparatus for selectively injecting diesel oil and igniting fuel into the combustion chamber of a reciprocating internal-combustion engine using as main fuel diesel oil or gas - Google Patents

Description

The invention relates to an injection device with the features of the preamble of claim 1.

A four-stroke type reciprocating internal combustion engine is known, which can be operated either with diesel oil or gas as the main fuel. In the case of this machine, in the case of gas operation, a quantity of pilot oil consisting of diesel fuel is injected into the combustion chamber through the same spray holes through which the diesel oil is also injected when the machine is operated with diesel oil as the main fuel. Since the quantity of pilot oil should be 5 to 10% of the quantity injected at full load in diesel operation, poor quality is achieved for the pilot oil injection in gas operation, because the entire cross-section of the spray hole is too large for such small quantities of injection, especially since today there is a tendency to the quantity of pilot oil to be injected to decrease to 1% and less. In addition, it is not possible to use the known device to inject such small injection quantities in a precisely controlled manner at the same pressure as is the case for the larger quantity when the machine is operated with diesel oil.

The invention has for its object to provide an injection device of the type mentioned, with which the very small quantities of pilot oil are injected in a precisely controlled manner when the machine is operated at high pressure under gas pressure, as is the case with the much larger injection quantities when the machine is operated with this oil as the main fuel.

According to the invention, this object is achieved by the features of the characterizing part of claim 1.

With this design of the device, the hole cross section for the ignition oil injection can be optimally dimensioned for the small amount of 1% or less, so that when the machine is operated with gas, the quality of the ignition oil injection is optimal, because then the larger overall cross section of the diesel oil injection holes which is injected during diesel operation is switched off. If the machine is operated with diesel oil as the main fuel, then the diesel oil injection holes also come into operation, the overall cross section of which is dimensioned for the then much larger amount of diesel oil injected.

An injection valve for a diesel internal combustion engine is known from US Pat. No. 2,398,834, which is operated exclusively with diesel oil. The injection valve has two rows of spray holes, each row being assigned a valve needle. The two valve needles are each held in the closed position by a spring; the spring force of one spring is larger than that of the other spring. The pressure of the fuel to be injected acts on the valve needles in the opening sense. When the machine is operating, the valve needle loaded by the weaker spring opens first and leaves a relatively large one at a lower pressure The amount of fuel gets into the combustion chamber (pre-injection), whereas the valve needle, which is loaded by the stronger spring, opens later and a smaller amount of fuel flows into the combustion chamber at a higher pressure (main injection).

This known valve is not time-controlled. Furthermore, since it is not set up to inject diesel oil through only one row of spray holes during operation of the machine, it is not suitable for achieving the object on which the invention is based.

Further advantageous refinements of the injection device are specified in the subclaims.

Fig. l

in schematischer Darstellung eine Einrichtung zum Einspritzen von Zündöl und Dieselöl bei einer Hubkolbenbrennkraftmaschine, die ausser mit Dieselöl auch mit Gas betrieben werden kann, und

Fig. 2

die Einspritzeinrichtung nach Fig. l in detaillierter Darstellung.

An embodiment of the invention is explained in more detail in the following description with reference to the drawing.
Show it:

Fig. L

a schematic representation of a device for injecting ignition oil and diesel oil in a reciprocating piston internal combustion engine, which can also be operated with gas in addition to diesel oil, and

Fig. 2

the injection device of FIG. 1 in a detailed representation.

According to FIG. 1, a time-controlled injection valve 10 is provided, which has an accumulator chamber 22 for the liquid fuel and projects into the combustion chamber 3 of a reciprocating piston internal combustion engine, not shown, with its lower end, which has a plurality of spray holes 18, 19. As will be described below, the liquid fuel consists of diesel oil, which is injected either in small quantities as pilot oil or in larger quantities as main fuel. In addition to the diesel oil, gas, possibly mixed with combustion air, is also supplied to the cylinder 4 (dashed line 6), which also serves as the main fuel and then through the pilot oil is ignited. The reciprocating piston internal combustion engine is a two-fuel machine that is operated either with diesel oil as the main fuel or with gas as the main fuel and can work according to the two- or four-stroke process.

The combustion chamber 3 is delimited by the cylinder 4 and the working piston 5 movable up and down therein. The diesel oil is fed via a fuel line 76 to a pump device l2, which pumps it under high pressure via a line 63 into the accumulator chamber 22 of the injection valve l0. A relief line 34 leads from this injection valve to a control device 11, by means of which the injection time is controlled.

2, the injection valve l0 has a valve body which consists of an upper part l3, a middle part l4 and a lower part l5, the three parts being held together by means which are not shown in detail. The valve body penetrates a cylinder head l6 and projects with the lower end of its lower part l5 into the combustion chamber 3 of the cylinder, not shown here. The end of part 15 projecting into combustion chamber 3 has a central spray hole 18 and, at a higher level, a series of spray holes 19, the axes of which are at an acute angle to the longitudinal axis of the valve body.

The lower part l5 of the valve body contains a valve needle 20 with a cylindrical cross section, which is guided in an axial bore 2l of the part l5. The end face of the valve needle 20 facing the combustion chamber 3 is conical and cooperates sealingly with a corresponding counter surface in part 15. The spray holes l9, which are connected on the inlet side via an annular groove, are arranged such that there is a distance "d" between the lower boundary of this annular groove and the transition from the cylindrical surface of the bore 2l to the conical counter surface.

The upper part l3 of the valve body contains the accumulator space 22, in which the fuel to be injected is stored under high pressure. Starting from the accumulator chamber 22, a fuel supply channel 23 extends through the central part 14 and opens into an annular groove 24 in the wall of the lower part 15. This annular groove extends approximately to the middle of the bore 2l leading the valve needle 20. The fuel supply channel 23 continues from the annular groove 24 in an oblique bore 23 ', which opens into the bore 2l. In the mouth region of the bore 23 ', the valve needle 20 has an annular groove into which a diametrical channel 25 opens. From this channel 25 a central channel 26 leads in the valve needle in the direction of its conical end face. Near this end face, the channel 26 bifurcates into two short channels, the axes of which are perpendicular to the conical surface. The mouths of the short channels are somewhat widened in such a way that sealing portions of the conical surface remain on both sides of each widening, which block the fuel flow to the spray holes 18 and 19 in the closed position of the valve needle 2l.

At the lower end of the middle part l4, a central leakage space 27 is provided, to which a leakage channel 28 is connected, which leads out of the component l4 above the cylinder head l6. A load piston 29, which presses on the valve needle 20, projects into the leakage space 27 from above, by means of a spring 30 and by means of the fuel pressure prevailing in the accumulator chamber 22, which acts on the upper end face of the loading piston. For this purpose, a connecting channel 3l is provided in part l4, which connects the accumulator space 22 to a space 32 above the loading piston 29 and which has a throttle point. The diameter of the loading piston 29 is dimensioned somewhat larger than the diameter of the valve needle 20. A relief channel 33 leads out of the space 32 out of the injection valve 10. The relief line 34, which leads to the control device 11, is connected to the relief channel 33.

The control device 11 has a housing 35, in which a slide sleeve 36 and a control slide 37 are arranged. The slide sleeve 36 has an annular groove 38 in the region of the connection of the relief line 34, from which a first control bore 39 leads to the inside of the slide sleeve. A second control bore 40 is provided axially below the first control bore 29 in the slide sleeve 36. The second control bore 40 is connected via an annular groove 4l to a further relief line 42 connected to the housing 35, which leads to a slide plate 44 which is arranged on a camshaft 43 and is fixed relative to this. The control bores 39 and 40 cooperate with two control edges 45 and 46 on the control slide 37, the upper control edge 45 being inclined to the longitudinal axis and the lower control edge 46 being perpendicular to the longitudinal axis of the slide.

The lower end of the control slide 37 rests on the free end 47 of a one-armed lever 48 which can be pivoted with its other forked end about a pivot point 49 and is supported on a cam 5l of the camshaft 43 via a roller 50 arranged between the two ends. The Cam 5l is a so-called drop cam and rotates in the direction of arrow 52 when the device is in operation. To prevent the control slide 37 from rotating about its longitudinal axis, the lower slide end is slotted, the lever end 47 engaging in the slot. The control slide 37 is pressed against the lever 48 by a conical spring 53 supported in the housing 35. The slide sleeve 36 is mounted immovably in the housing 35 in the axial direction, but can be pivoted about the longitudinal axis of the slide 37 via a lever 54.

The connection point of the further relief line 42 on the slide plate 44 is connected via a channel 55 to a groove 56 which is arranged in the lateral surface of the camshaft 43 and extends only over part of the circumference of the camshaft. The groove 56 is in turn connected via a radial bore 57 to a central bore 58 in the camshaft. When the camshaft is rotated, there is therefore only a brief connection between the channel 55 and the groove 56.

Above the control device 11 there is the pump device 12, whose housing common to the control device contains a pump head 60 with a spring-loaded pressure valve 6l at the upper end. A fuel pressure line 63 is connected to the pump cover 62 and opens out into the accumulator chamber 22 of the injection valve 10 on the one hand and into a pressure compensation vessel 85 via a throttle valve 84 on the other hand. To deliver the fuel, an axially movable piston 64 is provided in the lower region of the pumping device, which is supported with its lower end on the control slide 37 and, because of the conical spring 53, follows the movements of the slide. The piston 64 protrudes axially movable cylinder liner 65 which is guided in a cylindrical fixed housing part 66. The cylinder liner 65 has a flange 67 at its upper end, with which it bears against a shoulder 68 of the cylinder-like part 66 in the position shown. A spring 69 is provided underneath the flange 67 and tends to lift the flange 67 off the shoulder 68. A centrally drilled, axially immovable force compensation piston 70 projects into the upper end of the cylinder liner 65. The central bore of the piston 70 leads to the pressure valve 6l in the pump head 60. The piston 70 has a round base 7l at its upper end, with which it Radially movable within limited limits - is supported on the pump head 60 in a sealing manner. This sealing support is provided on the one hand by means of a conical spring washer 72 and on the other hand hydraulically by providing a relief ring groove 73, the inside diameter of which is smaller than the outside diameter of the piston 70. The ring groove 73 is connected via a radial groove to the space 88 surrounding the piston 70 .

The cylinder liner 65 has an annular groove 74 on the inside approximately in the middle, which is connected via radial bores to a recess 75 in the outer surface of the liner 65. In the area of the recess 75, a line 76 is connected to the pump housing 35, which leads from a fuel reservoir 77 and contains a low-pressure feed pump 78. The feed pump 78 supplies via parallel lines 76 'identically constructed devices of other cylinders of the reciprocating piston internal combustion engine. A line 79 branches off from the line 76 and is connected to the pump housing via a pressure regulator 80 and a line 81, in the region close to the foot 71 of the piston 70. In this way, the ones rotation 75, the space 87 between the pistons 64 and 70, the central bore and the space 88 above the flange 67 filled with fuel.

An overflow line 82 with a pressure relief valve 83 is connected to the line 79 and leads back to the fuel tank 77. Corresponding to the lines 76 '80 lines 8l' are connected to the pressure regulator, which lead to the other devices. In addition, the fuel pressure line 63 corresponding fuel pressure lines 63 'of the other devices are each connected via a throttle valve 84' to the pressure compensation vessel 85, from which a measuring line 86 leads to the pressure regulator 80.

The injector described works as follows, assuming gas operation. In the position of the cam 5l shown in FIG. 2, the control slide 37 was moved downwards at a very high speed by means of the strong conical spring 53, since the straight section of the cam 5l, over which the roller 50 of the lever 48 had previously been moved downward, was opposite the radial is only slightly inclined. The dimensioning of the lever lengths of the lever 48 results in a large axial path during the movement of the control slide 37, which makes it possible to provide the sealing gap between the control slide and the surrounding slide sleeve 36 to a relatively small diameter, so that the inevitable leakage quantities are kept relatively small can.

When the camshaft 43 rotates further in the direction of arrow 52, the lever 48 is pivoted counterclockwise and thereby moves the control slide 37 upward. Simultaneously with this upward movement, the piston 64 is also moved upward, whereby - if the upper end face of the piston 64 has passed the upper limit of the annular groove 74 - the delivery of the fuel enclosed in the space 87 begins, which then passes through the bore of the piston 70, the opening pressure valve 6l and the line 63 to the accumulator chamber 22 of the injection valve l0. The valve needle 20 remains in the closed position since the fuel pressure acts on the valve needle via the loading piston 29. In the further course of the upward movement of the control slide 37, the oblique control edge 45 first passes the second control bore 40 and then the first control bore 39, which - although there is now a connection between the relief lines 34 and 42 - has no consequences for the injection valve l0 because the connection the line 42 on the slide plate 44 is still blocked, because the groove 56 in the camshaft 43 is now not connected to the channel 55. With further upward movement of the control slide 37, the second control bore 40 is closed by the control edge 46, which corresponds to a position of the roller 50 of the lever 48 shortly before the tip of the cam 5l.

After the roller 50 of the lever 48 has passed the cam tip, the control slide 37 moves downward at high speed. As soon as the lower control edge 46 clears the second control bore 40, the connection of the relief lines 34 and 42 is created, this connection having the effect of pressure relief, because the relief line 42 now has a space via the channel 55, the groove 56 and the bores 57 and 58 communicates deeper pressure. A massive pressure drop thus occurs in the lines 42 and 34, which also has an effect on the load piston 29 in the injection valve 10 via the relief channel 33. As a result, the Pressure of the diesel oil located in the accumulator chamber 22, which acts via the channels 23, 23 ', 25 and 26 on the valve needle 20 in a lifting sense, briefly move the valve needle upwards, so that fuel is injected into the combustion chamber 3 via the central spray hole l8 . The stroke of the valve needle 20 remains smaller than the distance "d", so that no diesel oil can escape through the spray holes l9. The amount escaping through the spray hole 18 is therefore very small and serves as ignition oil for the gas contained in the combustion chamber 3.

The described relief of the loading piston 29 is only brief, since in the position of the slide sleeve 36 shown in FIG. 2, the axial distance of the control edges 45 and 46 lying in the area of the control bores 39 and 40 is the smallest and the oblique control edge 45 - shortly after Release of the second control bore 40 through the control edge 46 - the first control bore 39 shuts off, whereby the connection of the relief lines 34 and 42 is interrupted again.

If the internal combustion engine is to be switched from gas operation to operation with diesel oil as the main fuel, the gas supply via line 6 is interrupted and the slide sleeve 36 is pivoted in the control device 11 with the aid of the lever 54. As a result, there is a greater axial distance between the control edges 45 and 46 in the region of the control bores 39 and 40. This means that with a downward movement of the control slide 37, the connection of the relief lines 34 and 42, and thus the pressure drop across the loading piston 29, is maintained for a longer time than in the gas operation described above. Accordingly, the valve needle 20 also makes a larger one Opening stroke so that the diesel oil is also injected into the combustion chamber via spray holes l9. In diesel operation, a significantly larger amount of diesel oil is injected than in gas operation. Otherwise, the device described functions in the same way as in gas operation, that is to say that when the control slide 37 moves upward, the connection of the relief lines 34 and 42 has no consequences, because then the channel 55 does not communicate with the groove 56 in the camshaft 43.

The delivery rate can also be changed with the pump device 12, which is done in the following manner with the aid of the controller 80. The fuel pressure in the accumulator chamber 22 is registered via the throttle valve 84, the pressure compensation vessel 85 and the measuring line 86 in the pressure regulator 80. As long as the selected pressure in the accumulator space has not yet been reached, the pressure regulator allows the full pressure of the feed pump 78 to act via the lines 79 and 81 in the space 88, as a result of which the cylinder liner 65 is pressed onto the shoulder 68 with its flange 67. This happens because no hydraulic forces act on the bush 65 from the high pressure side because of the force compensation piston 70. For their axial positioning, therefore, only the balance between the force of the spring 69 and the force of the hydraulic pressure in the space 88 is decisive. The quantity delivered by the piston 64 then corresponds to the largest possible delivery quantity. If the fuel pressure in the accumulator space 22 exceeds the selected pressure, the feed pressure is reduced by the pressure regulator 80, so that this reduced pressure also takes effect in the space 88. As a result, the cylinder liner 65, supported by the spring 69, can move upward, so that the delivery stroke of the piston 64 starts later. The maximum stroke of the cylinder liner 65 is reached when this rests with its upper end face on the foot 7l of the piston 70. In this position of the cylinder liner, the piston 64 makes an idle stroke, ie the delivery rate is zero. During the downward movement of the piston 64, vacuum is generated in the delivery chamber 87, which is filled with diesel oil from the feed pressure when the upper end face of the piston 64 has reached the annular groove 74 in the cylinder liner.

With the help of the throttle valves 84 and 84 ', a pressure application of the regulator 80 which is as constant as possible is achieved because the pressure from all adjacent pumping devices is brought to the pressure equalization vessel 85 after corresponding throttling and the pressure is thus almost constant over time. The interposition of the throttle valves and the pressure compensation vessel also has the advantage that if one pump device fails, the remaining injection devices still remain reasonably functional.

Claims (9)

1. A device for selectively injecting diesel oil as main fuel and diesel oil as igniting oil into the combustion chamber of a reciprocating internal combustion engine which operates with injected igniting oil when running on gas as main fuel, characterised in that the combustion chamber (3) has a timed fuel injector (10) which has an accumulator chamber (22) for high-pressure diesel oil and which is formed with at least one injection aperture (18) for injecting diesel oil as igniting oil and is also formed with injection apertures (19) for injecting diesel oil as main fuel, the last-mentioned injection apertures (1g) being inoperative during the injection of igniting oil, the fuel injector (10) has a valve needle (20) common to the igniting oil injection aperture (18) and to the diesel oil injection apertures (19) and energized in the sense of a closure by the pressure in the accumulator chamber (22), and a control facility (11) is provided which opens in timed fashion only the igniting hole injection aperture (18) in the fuel injector (10) when the engine runs on gas as main fuel and the igniting oil injection aperture (18) and the diesel oil injection apertures (19) when the engine runs on diesel oil as main fuel, the igniting oil injection aperture (18) and the diesel oil injection apertures (19) opening in response to a decrease in the pressure acting on the injector needle (20).
2. A device according to claim 1, characterised in that the control facility (11) has a valve spool (37) which has two lands (45, 46) and which is reciprocated vertically by way of a drop cam (51) - the same rotating at crankshaft speed in the case of two-stroke engines and at half the crankshaft speed in the case of four-stroke engines - and which is mounted in a sleeve (36) formed with two axially spaced-apart ports (39, 40) which cooperate with the lands (45, 46) and to which a relief line (34) connected to the fuel injector (10) and a relief line (42) connected to a control element (44, 55 to 58) is connected, the control element (44, 55 to 58) rendering ineffective the communication between the two relief lines which is produced by the valve spool (37) during its rising movement.
3. A device according to claim 2, characterised in that the control element has a duct (55) disposed in a component (44) which is stationary relatively to the cam shaft (43) and the control element is formed with a groove (56) which extends over some of the peripheral surface of the cam shaft (43) and which does not communicate with the duct (55) during the rising movement of the valve spool (37).
4. A device according to claim 3, characterised in that the sleeve (36) is pivotable around the longitudinal axis of the spool (37).
5. A device according to claims 2 to 4, characterised in that the cam drive for the control facility (11) is also effective as the drive for a pump device (12) for the diesel oil to be injected.
6. A device according to claim 5, characterised in that a delivery piston (64) of the pump device bears on the spool (37) and slides in one end of an axially movable cylinder liner (65) which extends slidingly at its other end around an axially pierced piston (70), the bore thereof extending, by way of a pressure valve (61) in the pump device (12), to the fuel delivery line (63) extending to the fuel injector (10).
7. A device according to claim 6, characterised in that the cylinder liner (65) is formed substantially at the centre of its length with apertures through which the diesel oil to be delivered enters the delivery chamber (87).
8. A device according to claim 6, characterised in that the pierced piston (70) has at its end near the delivery valve (61) a foot (71) by means of which the piston (70) is pressed sealingly on to the pump casing with provision for reduced radial movement.
9. A device according to claims 6 to 8, characterised in that the cylinder liner (65) has at its end near the pierced piston (70) a flange (67) which, when the cylinder liner (65) is in its lowest position, rests on a shoulder (68) of the casing extending around the cylinder liner (65), the casing co-operating with the flange to bound a chamber (88) which extends around the pierced piston (70) and which is filled with diesel oil at a variable pressure.

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