DE2909233A1 - FUEL INJECTION DEVICE FOR INTERNAL COMBUSTION ENGINES - Google Patents

Description

R . ^:.
February 23, 1979 Ks / Ht

ROBERT BOSCH GMBH, 7OOO Stuttgart Fuel injection device for internal combustion engines State of the art

The invention is based on a fuel injection device for internal combustion engines of the type
Main claim, as known from CH-PS 447 714
is. In this fuel injection device, the fuel in the pressure chamber of the injection valve is constantly under the constantly high pressure delivered by the fuel pump and the injection time is reduced by the
Duty cycle of at least one electromagnetic control valve is determined. One inserted in the pressure line and one from the injected with each injection
The free piston passing through the stroke depending on the fuel quantity serves as a safety device and blocks the force

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fuel supply to the injection valve, e.g. if there is a faulty switching of the electromagnetic control valve or, if the valve needle gets stuck, the injected one Fuel amount the maximum allowable amount by one exceeds a certain amount. This fuel injector with an electromagnetically operated control valve, like all others, also has, for example, mechanical-hydraulic controlled fuel injection devices, in which the injection duration of the under constant high pressure on the Nozzle needle pending fuel is determined by the duty cycle of the control valves, the disadvantage that Both the start of injection and the end of injection, i.e. the duration of the injection, depend on the one to be adhered to precisely and precisely Switching time of this control valve are dependent. This is particularly the case with high-speed internal combustion engines Difficulties and the object of the present invention is to control the start of injection separated from that of the end of injection and precisely metered the injection quantity on the high-pressure side. The one at the known fuel injector used. Free piston also limits the amount of fuel injected even when idling and at part load, only one by a certain amount above the maximum permissible fuel injection quantity Lying injection quantity, i.e. the engine can run uncontrolled despite the safety device run up.

Advantages of the invention

The fuel injection device according to the invention with the characterizing features of the main claim has dem-

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over the advantage that by the as a metering member serving free piston actuated switching element of the control device depending on the injected Fuel quantity only the closing movement of the valve needle is controlled while regardless of the start of injection can be triggered in a known manner by a start of injection transmitter.

The measures listed in the subclaims are advantageous developments and improvements of the Fuel injection device specified in the main claim possible. Thus, the invention is also a fuel injection device whose control device is a The electrical actuator that determines the injection duration of the injection valve and is controlled by a start of injection sender, preferably has an electromagnet ^, applicable in a particularly advantageous manner if according to the Characteristic part of claim 2 of the end of the spray causing the working stroke of the electric actuator by the Switching element is triggered. In this fuel injection device, preferably equipped with a solenoid injection valve Thus, according to the invention, the control of the start of injection and that of the end of injection are separated.

A particularly favorable and functionally reliable embodiment of the control device, regardless of whether it is electrical or is controlled mechanically-hydraulically, results in a generic fuel injection device with an auxiliary-controlled injection valve according to the generic preamble of claim 3 by the im Characteristic part of this claim 3 specified features;

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and in a fuel injection device according to claim 4, in which the under control pressure in the injection pauses standing control pressure chamber to initiate the injection start through a first control valve to the relief line and to terminate the injection through a The second control valve can be connected to the control pressure line j are the advantages sought according to the invention achieved in that only the second control valve is acted upon by the switching element which can be actuated by the free piston is. The features set out in claims 3 and 4 can be used in an advantageous manner both electrically controlled and mechanically-hydraulically controlled Use fuel injection devices ^

With electrically controlled or regulated fuel injection devices the switching element can preferably be connected to a non-contact displacement encoder or Limit switch according to claims 5 to 7 are equipped, and a safe and with a relatively slow working Control circuit-compliant device results from the features of claims 6 and 8.

In fuel injection systems of the generic type equipped with an auxiliary-controlled injection valve can also be a safe control device provided with low-frequency control elements be realized when the fuel injection device according to the characterizing features of claim 9 is trained. The control or regulatable stroke stop used there requires a relatively slow working one Position control and the tappet serving as a switching element

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active "las zv. ^r eite control valve purely mechanical way without additional support staff and resources, but making the whole circuit clear, simple and not prone to trouble viird. Bas first control valve must work quickly and finish before the second control valve. This is in another, Fuel injection device designed according to claim 10 is not necessary, because by using the second control point which closes the passage through the relief line from the control pressure chamber to a low pressure chamber at the end of the injection, the first control valve must close before the start of the next injection. In this case, up to an optionally electrically controllable stroke control of the stroke stop, all control elements can be designed mechanically-hydraulically, which results in an inexpensive and reliably operating fuel injection device Control valve can also be designed as a solenoid valve.

Since, according to the invention, the end of the injection or the closing movement of the valve needle is caused by the switching element actuated by the pre-piston is triggered, the concept of the invention can be applied to any known type of fuel injection devices in which the fuel injection devices are controlled with a constant high or setpoint value and work is carried out in the pressure chamber at the system pressure present at the valve needle.

drawing

Five embodiments of the invention with additional

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Design variants of the piston assembly are shown in the drawing and explained in more detail in the description below. FIG. 1 shows a simplified representation of the first exemplary embodiment of a fuel injection device with an auxiliary-controlled injection valve, and FIG. 2 shows a second exemplary embodiment ₅ in which at least two injection valves are provided with a single free piston arrangement. Figure 3 shows the third embodiment with a double nozzle , Figure h shows a variant of the free piston assembly with a controllable stroke stop; Figure 5 shows a further embodiment of the free piston assembly; Figure β shows the fourth embodiment with a mechanically operated second control valve; and Figure 7 shows the fifth embodiment, also with a mechanically operated second control valve and a also mechanically operated first control valve.

Description of the exemplary embodiments

The first exemplary embodiment, shown in simplified form in FIG. 1, has an auxiliary-controlled injection valve 10 on which the fuel which is under constant high pressure is supplied from a fuel pump 13 via a reservoir 11 and a pressure line 12. With the appropriate Size of the injection pressure and layout of the lines the pressure line 12 can also take over the function of the memory 11.

The fuel delivered by the fuel pump 13 under injection pressure passes from the pressure line 12 into a pressure chamber 15 adjacent to a valve seat lh , into the one

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Pressure shoulder 16 designed as a differential piston Valve needle 17 protrudes, which in a known manner by the fuel pressure acting on the pressure shoulder 16 in the sense of an opening movement of the valve needle 17 is applied. In the drawn closed position of the valve needle 17, this is pressurized and here serving as a closing means intermediate piston 18 with a larger outer diameter compared to the valve needle 17 loaded in the closing direction on the valve seat 14. The required closing pressure is provided by the injection pressure standing fuel generated, which in the present case in a control pressure chamber 19 above the also intermediate piston 18, which is to be regarded as a control piston, is supplied. This control pressure chamber 19 is via a control pressure line 21 connected to the pressure line 12, which is under injection pressure, but it can also pass through one a pressure reducing valve not shown here have reduced pressure if the intermediate piston 18 accordingly is made large. Of course, a separate fuel or oil pressure source can also be connected to the Control pressure line 21 be connected in a known manner.

In the head 22a of the housing, denoted by 22, of the injection valve 10 is a part belonging to a control device 23 Control valve 24 inserted into the control pressure line 21 and connects in the drawn, by a return spring 25 brought about the initial position serving here as a closing pressure source pressure line 12 with the control pressure chamber 19. The Control valve 24 is designed as an electromagnetic 3/2-way valve, provided with an electromagnet 26 and

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binds the control pressure chamber 19 in its second switching position assumed when the electromagnet 26 is excited a relief line 27, which leads to a fuel tank 28 to be regarded as a space low, ren pressure, from the the fuel pump 13, which is designed as a high-pressure feed pump, also draws in the required fuel.

A free piston arrangement 31 is located in the pressure line 12 used, in the cylinder bore 32 a free piston 33 is guided. This one in the breaks by a return spring 3 ^ in the initial position shown The held piston 33 passes through one of the injected fuel quantities with each injection dependent stroke H and is pushed back into the starting position by the return spring 3 ^ during the injection pauses. This is made possible by a throttle line 35 connecting both end faces of the free piston 33, wherein the throttle line 35 can be made very narrow, since the injection pause is opposite, especially in the case of diesel engines the injection time is at least 35: 1 longer. As a result, the influence of the throttle line 35 so small that the following text speaks of a stroke of the free piston 33 proportional to the amount of fuel can.

The stroke H of the free piston 33 is detected by a position sensor designed as an inductive displacement sensor 36, which here is only indicated by an external transmitter coil 37. In "connection with this position transmitter 36 is used the free piston 33 as a metering element of the control device 23, because when it reaches one designated here by IL, one

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predetermined fuel injection quantity proportional metering stroke the detected by the position transmitter 36 path signal S ,, is input into a control circuit 38, which is a Closing movement of valve needle 17 emits control signal S-j- to electromagnet 26. The inductive Displacement transducer 36 and the corresponding part of the control circuit 23 act as a determinant of the end of injection Switching element 39 of the control device 23.

To control the end of the injection, the electromagnet 26 is de-energized in the arrangement shown and the Control pressure chamber 19 is set under the fuel pressure causing the closing movement of valve needle 17. The start of injection is triggered in a clocked manner by a start-of-injection sender that is driven as a function of the engine crank angle, whereby the associated, the electromagnet 26 energizing control signal S ^ of the control circuit 38 as a function of further operating data B .., Bp, e.g. speed and / or load dependent is correctable.

The designed in Figure 1 as an electromagnetically driven 3/2-way valve and as an electrical actuator Serving control valve can alternatively be replaced by two 2/2-way valves (not shown) - of which then the first control valve, the connection between the control pressure chamber 19 and causing the start of injection the relief system 27 controls and the second control valve only, actuated by the switching element 39, by connection of the control pressure chamber 19 with the control pressure extention 21 determines the end of injection. The piston assembly according to the invention 31 with the associated switching element 39 can also be used for

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Control of a solenoid injection valve is used, the valve needle of which comes directly from the coil of an electromagnet is operated against the force of a closing spring, as is the case with gasoline injection systems. At a such a solenoid injector can be the inventive Control device contribute to a simplification of the electronic regulation (not shown).

Figure 2 shows the fuel injection device according to Figure 1 differentiating part of the second embodiment, in which as well as in the following For example, the parts that are the same as in FIG. 1 have the same designations and are functionally identical, but differ in design Parts are provided with an index line.

As the for the return stroke of the metering piston 33 is available standing time is substantially, about 35 times greater than the injection time, it is possible to have at least two injection valves 10 'and 10 "to be connected to a common pressure line 12, control pressure line 21 and relief line 27, with only one free piston arrangement for both injection valves 10 'and 10 " 31 'is necessary to control the end of the injection. The free piston assembly 31 'is here with a Equipped free piston 33 ', which carries an encoder pin 46 screwed into a central threaded bore 45. This Sensor pin 46 protrudes within a cylinder space that receives the return spring and is formed by cylinder bore 32 47 into a transmitter coil 37 'arranged in the same cylinder space 47 and forms together with this coil 37' an inductive displacement transducer 36 'which, together with the control circuit 38, is part of a switching element 39'. the

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_{Control circuit 38 generates both a first control signal S T1} , which determines the end of injection of injection valve 10 ', _{and a second control signal S T} p, which actuates electromagnet 26 of control valve 24 of second injection valve 10 " of the first exemplary embodiment shown in FIG. 1, the first injection valve 10 'differs from the injection valve 10 shown in FIG. 1 only in the absence of the intermediate piston 18 serving as a closing means and in FIG in this space acted upon part 17a 'of the valve valve 17' as a control piston applying the closing force and thus as a closing means Pressure line 12, a flow throttle 48 inserted , which is designed so that it generates the pressure drop required for a sufficiently rapid closing movement of the valve needle 17 'towards the pressure chamber 15'. As an alternative to this, a closing spring 49 serving as a closing means is used in the second injection valve 10 ″ within the control pressure chamber 19, so that a flow throttle in the pressure line 12 is unnecessary.

The start of injection of both injection valves 10 ′ and 10 ″ is triggered by the slightly modified injection start sensor 41 via the control circuit 38, with a corresponding angular offset and the associated end of the injection controlled by the metering piston 33 'responsible for both valves, of which the Throttle line 35 'enabling return stroke off-center

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orderly and in accordance with the faster return time the throttle line 35 in Figure 1 is tuned differently. The position of the Encoder pin 47 can be changed within the free piston 33 'and fixed by a lock nut 51.

The designated 23 'and essentially from the switching element 39 'and the control valves 24 existing control device can as indicated by dash-dotted extensions the pressure line 12, the control pressure line and the relief line 27 indicated, when running slowly Engines also actuate at least one other injection valve.

In the third exemplary embodiment according to FIG. 3, the injection valve 60, which is designed as a double nozzle, is also like the injection valves described above are auxiliary controlled j including the two valve needles 6l and 62 by one each Control valve 24 can be controlled. Both valve needles 6l and 62 control the fuel to be injected from the common pressure chamber fed via the pressure line 12 15, with only one free piston arrangement 31 being effective for both valve needles 6l and 62. This occurs in advantageously, with valve needles 6l and 62 controlled one after the other in the sense of an opening movement sudden jump in quantity, since the injection quantity of the stroke speed of the free piston and the end of injection from the injection end signal generated by the switching element 39 is dependent. In a known manner, both valve needles 61 and 62 can be used one after the other to shape the course of injection or alternatively or jointly to control the cross-section.

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The free piston arrangement only indicated in FIG of the free piston arrangement 31 or 31 'from Figures 1 and 2 or, alternatively, how in the. Figures 4 and 5 shown, be formed.

The free piston arrangement 63 shown in FIG. 6 contains a free piston 64 which, in the drawn initial position caused by the return spring 34, is fixed by a controllable or regulatable stroke stop 65. Its end face 6ha facing away from the return spring 34 rests during the injection pauses the stroke stop 65, shown here only hinted at, which can be adjusted in the direction of the free piston 64 according to the amount to be injected by means of an adjusting device indicated by an arrow 66. The stroke end of the free piston 64 is detected by a transmitter coil 67a of an inductive position transmitter 67 serving as an electrical limit switch and entered into a control circuit 38. In this arrangement, the metering stroke H 'which determines the fuel injection quantity is determined by the controllable and regulatable starting position of the stroke stop 65 and the respectively constant end position of the free piston 64 detected by the limit switch 67 End switch 67 and the control circuit 38 'existing switching element 68 can be used at any time instead of one of the switching elements 39 ₃ 39' shown in Figures 1 to 3. Nothing changes in the design of the associated injection valves.

FIG. 5 shows an embodiment variant, denoted by 71, of the free piston arrangement 63 shown in FIG

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the starting position of the free piston 64 is controlled or regulated by an adjusting pin 72 serving as a stroke stop. The adjusting pin 72 is inserted in a slightly displaceable but sealed manner in a guide bore 73 which is incorporated in a wall of a housing 77 of the free piston arrangement 71 which separates a cylinder space 74 receiving the free piston 64 from a pressure chamber 75. The position of the adjusting pin 72, which defines the starting position of the free piston 64 and thus the amount of fuel to be injected, is determined by the adjustable biasing force of an adjusting spring 78 made with a precisely defined spring stiffness and by the hydraulic pressure in the pressure chamber 75 controlled or regulated by a pressure control valve 79. In the present example, the pressure chamber 75 is connected ^to the pressure line 12 of the fuel injection device via the pressure regulating valve 79. Of course, another pressure source can also be used here. An inductive displacement transmitter 82 equipped with a transmitter coil 81 serves in the present arrangement at the same time to return the starting position of the free piston 64 determined by the stroke stop 72 and at the same time as an electrical limit switch for the end position of the free piston 64 that triggers the end of injection thus part of a switching element 83, not shown here. To avoid impermissible vibrations in the injection system and on the free piston 64, a backflow throttle valve 85 is inserted into the part of the pressure line 12 leading to the injection valve, and a line 86 connecting the pressure control valve 79 to the pressure chamber 75 contains a damping throttle 87-

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The fourth embodiment shown in Figure 6 shows a likewise auxiliary controlled, to the pressure line 12, the control pressure line 21 and relief line 27 connected injection valve 90. This injection valve 90 operates like the injection valve 10 'in Figure 2 and takes in its housing 91 also a free piston arrangement 92, whose free piston 93 serving as a metering element in its vcn the return spring 34 caused the initial position shown how the free piston 64 in FIGS. 4 and 5 is fixed by the controllable or regulatable stroke stop 72. A first control valve 94 inserted into the relief line 27 is designed as a 2/2-way valve and opens in the actuated state, the connection from the control pressure chamber to the relief line 27 and thus directs the injection a. This valve 94 can be electromagnetic or also mechanical are controlled by an actuator 95 and must be connected to the relief line shortly before the end of the injection 27 lock again. A slide valve serving as a second control valve is used to control the end of the injection 96 is provided, the valve slide .100 at the end of the metering stroke traversed by the free piston 93 via a Serving as a switching element plunger 97 against the force of a return spring 98 from the drawn into a switching position is displaced, in which a control point 99 of the valve slide 100 designed as an annular groove, the control pressure line 21 connects to the control pressure chamber 19, whereby the full fuel pressure in the control pressure chamber 19 arrives and the valve needle 17 ′ on its valve seat 14 presses and thus terminates the injection. The stroke control device for the stroke stop 72 is indicated by 101 and not detailed here. Despite the closed

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Suen control valve 9 ^ and in the drawn locked position When the valve slide 100 has returned, the control point 99 has a throttle cross-section which allows a low leakage current to pass through 99a, by means of which the required closing pressure is maintained until the start of the subsequent injection remain.

The injection valve 110 shown in FIG. 7 has similar components and almost the same function as the injection valve 90 in FIG. In addition to the coaxial arrangement of the valve needle 17 , reciprocating piston arrangement 92 and the second control valve designated here as 111, the injection valve 110 differs in particular through a second control point 112, also designed as an annular groove, on the valve slide 113 _S, which in the initial position of the valve slide 113 is a connection from the control pressure chamber 19 to the relief line 27 holds open, but this closes in the shifted switching position assumed at the end of injection. At the end of the injection, the valve slide 113 is moved by the free piston 93 via the tappet 97, which serves as a switching element, into its other end position, in which the annular groove 99, which serves as the first control point here, opens the connection from the control pressure line 21 to the control pressure chamber 19. As a result, the injection is ended by actuating the valve needle 17 via the intermediate piston 18. In contrast to the exemplary embodiment shown in FIG. 6, the first control valve 9h can maintain its open position (not shown), which triggers the start of injection, until the valve slide opens the connection to the relief line 27 again through the control point 112 during its return stroke. Through this

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the control valve 94 can work more slowly than that described in FIG. 6 and _3, as indicated in the drawing, can be driven mechanically. The control valve 94, shown only by a circuit symbol, can be formed by a lifting slide provided with sloping edges or a piston slide provided with control grooves or by a rotary slide which has an adjustable control sleeve and thus enables a change in the injection start to achieve precise control. Of course, the control valve 94 can also be actuated electromagnetically. The fifth embodiment shown in Figure ^{7 works;} but only with mechanical-hydraulic switching means ur.d made possible by the. Components according to the invention and the use of the free piston 93 serving as a metering element provide an exact control of the amount of fuel to be injected. ₍ .

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Claims (1)

February 23, 1979 Ks / Ht ROBERT BOSCH GMBH, 7OOO Stuttgart 1 Expectations ! ./ Fuel injection device for internal combustion engines with a fuel pump that delivers fuel under constant high pressure via a pressure line to a Drua>: rauiTi of an injection valve that is adjacent to the valve seat, and a pre-piston arrangement inserted into the pressure line, its in a cylinder bore against the force of a return spring displaceable Preikolben passes through a stroke approximately proportional to the injected fuel quantity with each injection and is pushed back into its starting position by the return spring during the injection pauses and which has a throttle line connecting both end faces of the free piston, and with one the opening and closing movement of a closing means on the Valve needle pressing the valve seat causing control device, characterized in that the pre-piston (33, 33 ' , 64, 93), as a metering member of the control • einrichtung (23, 23 ') is used and when one of depending on the amount of fuel to be injected and below 030038/0214 BATH ORIGINAL - 2 - row 5 Consideration of the leakage losses in the throttle line (35) approximately proportional metering stroke (EL ₃ EL ·) a switching element (39, 39 ', 68, 83, 97) that triggers the closing movement of the valve needle <17 _{3 17', 17 ", 61, 62)} actuated by the control device. 2. Fuel injection devicej its control device a determining the injection duration of the injection valve and electrical controlled by a start of injection sender An actuator, preferably an electromagnet, according to claim 1, characterized in that the end of the injection effecting working stroke of the electric actuator (24) can be triggered by the switching element (39, 39 '). 3. Fuel injection device with a pilot operated Injection valve, the valve needle of which is arranged in the pressure chamber and directed by the fuel pressure in the opening direction applied pressure shoulder and at its end facing away from the valve seat has a control piston, the control pressure chamber of which to actuate the valve needle by at least one control valve of the control device alternately below a control pressure supplied via a control pressure line can be set or via a relief line with a room 030038 / 02U - 3 -. R. 5 3 2 low pressure can be connected, according to claim I _9, characterized in that the control valve (2 ¹ I ₅ 96, 111) can be switched into its switching position which triggers the splashing by the switching element (39, 39 ', 68, 83, 97). H. Fuel injection device according to Claim 3, in which the control pressure chamber, which is under control pressure during the injection pauses, can be connected to the relief line through a first control valve to initiate the start of injection and to the control pressure line through a second control valve to terminate the injection, characterized in that only the second control valve (96, 111) can be acted upon by the switching element (97) actuatable by the free piston (93) (Figures 6, 7) 5. Fuel injection device according to one of claims 2 to 4, characterized in that the switching element (39, 39 ', 83) a metering stroke (H ₁ ) of the free piston (33, 33% 64) detecting, preferably designed as an inductive displacement encoder electrical position transmitter (36, 36 '. 82) (Figures 1, 2 and 5). 6. Fuel injection device according to one of the claims -J ₄ - 030038/0214 2 to 4, characterized in that the switching element (68, 83) one from the pre-piston (64) when the metering stroke (Hp) is reached has actuatable electrical, preferably inductive, limit switch (67, 82) and the position of the pre-piston (64) is set at the start of the Eubbing by a controllable or adjustable stroke stop (65, 72), which is in the stroke direction of the Pre-piston (64) adjustably interacts with the end face (64a) of the pre-piston (64) facing away from the return spring (34) (Figure 4, 5) 7 · fuel injection device according to claim 5 or 6, characterized in that the electrical position transmitter (36 ') or limit switch (67) of the switching element (39', 68) has a transmitter coil (37'5 67a) arranged in the cylinder space (47) receiving the return spring (34), in the one at the metering stroke (H., Hp) of the free piston (33 ', 64) The transducer pin (46), which is adjustable in the free piston (33 '), is immersed (FIGS. 2, 4). 8. Fuel injection device according to claim 6, characterized characterized in that the position of the stroke stop (72) by an adjustable adjusting spring (78) and a means a pressure control valve (79) controllable hydraulic 030038/0214 Pressure in one of the cylinder space (74) of the free piston (64) separate pressure chamber (75) can be determined (Figure 5). 9. Fuel injection device according to claim 4, characterized in that the position of the free piston (93) at the start of the stroke is determined by a controllable or adjustable stroke stop (72) which is adjustable in the stroke direction of the free piston (33) with that of the return spring (34) remote end face of the free piston (93) cooperates and that the free piston. (93) when the metering stroke is reached, the second control valve (96j 111) is actuated via a tappet (97) serving as a switching element, which, when inserted into the control pressure line (21), closes it in its initial position except for a throttle cross-section (99a) that allows a small leakage flow and that in the end position actuated by the free piston (93), the full passage cross-section of the control pressure line (21) is kept open (FIGS . 6, 1). 10. Fuel injection device according to claim 9, characterized in that the second control valve (111) is designed as a slide valve ₅ whose valve slide (113) apart from a first control point (99) controlling the inflow from the control pressure line (21) to the control pressure chamber (19) 030038/0214 BATH ORIGINAL - 6 - R- 5 3 one of the. Passage through the relief line (27) from Control pressure chamber (19) has a second control point (112) that closes off a chamber of low pressure at the end of the injection, and that the first control valve (9 * 0 in the second Control valve (111) with the low pressure chamber connecting relief line (27) in "series to the second control point (112) is inserted (Figure 7). 030038/0214 ORIGINAL