GB2256012A

GB2256012A - A fuel injection device for diesel engines

Info

Publication number: GB2256012A
Application number: GB9210815A
Authority: GB
Inventors: Eckard Haas; Werner Lemme; Andreas Wichmann; Hans-Peter Mahlberg
Original assignee: Kloeckner Humboldt Deutz AG
Current assignee: Kloeckner Humboldt Deutz AG
Priority date: 1991-05-22
Filing date: 1992-05-21
Publication date: 1992-11-25
Also published as: DE4116644A1; GB9210815D0

Description

C- I-)o J 1 -, 1 - A fuel injection device for diesel engiues D E S C R I

P T 1 0 N The invention relates to a fuel injection device for diesel engines according to the preamble of claim 1.

Some known fuel injection devices for diesel engines comprise at least one pump element, consisting of a cylinder and a piston with a control edge. A movable spool valve is disposed coaxially around the pump piston and used for adjusting the beginning of delivery. The adjustment is e.g. hydraulic, ir-dependence on a pressurid proportional to the speed. Hydraulic injection adjustment means of this kind cannot provide the conditions for the beginning of delivery required in accordance with the strict environmental regulations. Alsoadditional complicated intervention in the injection adjustment process is expensive.

The aim of the invention is to provide a fuel injection device for diesel engines which is cheap and very reliable 0 and can be used to obtain a presettable characteristic curve for the adjustment of the beginning of delivery.

This problem is solved by the features in the characterising part of claim 1.

Advantageously the spool valve, disposed coaxially around the pump piston, is connected for power transmission purposes to the control shaft of a stepping motor. By this means, the beginning of delivery can be accurately adjusted by moving the control values of the stepping motor. The spool valve is connected to the stepping motor by at least one transmission means, so that the stepping motor can easily be adapted to the spool valve and easily replaced during maintenance work. If the transmission means is suitably con-tructed, conventional st-epping motors can be used without any structural alterations. The electrically controllable stepping motor, with suitable data processing, can be used at low expense to obtain a presettable characteristic curve for the adjustment of the beginning of delivery. If the steps of the stepping.-.,, potor are appropriately chosen, the beginning of delivery can be closely defined and the reliability is high compared with the prior-art known fuel injection devices in which the beginning of delivery is adjusted hydraulically.

According to another feature of the invention, the transmission means between the spool valve and the stepping motor is a shaft which rotates in dependence on the motion of the stepping motor. In order to convert the rotation of the motor into a stroke of the spool valve, the end face of the shaft facing the pump piston has an eccentric prolongation which engages in a recess in the spool valve. As a result of this arrangement, the rotation is advantageously converted into a stroke, which can be adjusted by varying the construction of the eccentric prolongation and the recess in the spool valve.

According to another feature of the invention, a powertransmitting device is disposed between the transmission means and th-stepping motor. The adva-ntage of the powertransmitting device, e.g. in the form of a lever or linkage, is that the motor can be disposed at a distance from the pump element, so that numerous variations can be made in the arrangement of the stepping motor and the construction of the pump element.

According to another feature of the invention, the transmission means of at least two pump elements are connected to the stepping motor by a common powertransmitting device. As an alternative to connecting each individual pump element to a separate stepping motor, it is now possible to connect two or more pump elements to a single stepping motor via the common power-transmitting device. This reduces the expense of construction, but on the other hand the beginning of delivery can be adjusted with respect to only one cylinder.

According to another feature of the invention, a control device and store are provided and are connected to at least one stepping motor. The control device has sensor inputs for recording operating parameters of the engine, and actuates each stepping motor in dependence on a characteristic curve stored in the store or in dependence on an operating parameter of the engine.- -The advantage of actuating the motor in dependence on a characteristic curve is that the motor can be rapidly and reliably actuated. The advantage of actuating the motor in dependence on at least one operating parameter of the engine is that the available operating parameters can be used to calculate the instantaneous adjustment of the beginning of delivery and set it via a stepping motor. Particularly advantageously, C the control device is associated with a separate unit for actuating the stepping motor, so that a single control device can be used for a number of stepping motors and associated actuating units. Advantageously also, the stepping motor is actuated in dependence on a characteristic curve and an operating parameter of the engine. By this means, a characteristic curve is selected in dependence on an instantaneous operating parameter and represents the beginning of adjustment of delivery in dependence on the detected parameter or another parameter, so that the stepping motor can be accurately positioned in addition to rapid and reliable adjustment. Since a stepping motor is associated with each individual pump element, irregularities in the pump elements can be compensated in addition to the main adjustment of the beginning of delivery. These irregularities are due e.g. to manufacturing tolerances or ageing. Particularly advantageously, the compensation can be made in dependence on operating parameters of the engine.

According to another feature of the invention, the control device has a data interface and means for calculating the adjustment of the beginning of delivery. A computer is incorporated in the control device and calculates the adjustment of the beginning of delivery in dependence on recorded data. The data can be operating parameters of the engine or values contained in the store of the control device. The values input into the store of the control device can be permanently stored or can be input via the data interface. The advantage of inputting values via the data interface is that the values can be individually adapted and input depending on the kind of engine and the conditions of use. The inputtable values can constitute a complete characteristic curve, or alternatively supporting values of a curve can be input, so that the computer incorporated in the control device can independently calculate. the other required values between the supporting points (e.g. by linear interpolation). For the purpose of inputting values into the store the control device is advantageously connected to an input unit via the data interface. Accordingly, if the input device (e.g. an alphanumeric keyboard) is suitably constructed, new values can be rapidly input and previously input values can be rapidly altered.

Other features of the invention are disclosed in the subclaims and the drawings, in which:

Fig. 1 shows a pump element and stepping motor for adjusting the beginning of delivery; Fig. 2 shows actuation of the spool valve by a lever; Fig. 3 shows adjustment of the beginning of delivery by a pump element; Fig. 4 shows adjustment of the beginning of delivery by more than one pump element; Fig. 5 shows a control device and components thereof, and Fig. 6 shows characteristic curves for adjustment of the beginning of delivery.

Fig. 1 shows a pump element 1 comprising a cylinder 2 in which a pump piston 3 is movable by a cam. A movable spool valve 4 is disposed coaxially around the pump piston 3. In order to control the flow rate, the pump piston 3 has a recess, more-particularly with a conEr61 edge 5. According to the invention the spool valve 4 of the pump element is connected to a control shaft 8.1 of a stepping motor 8 via a transmission means 6.1 which has an eccentric prolongation 7 on one end face. The eccentric prolongation 7 engages in a recess in the spool valve 4, so that when the valve 6.1 rotates the spool valve 4 moves in the axial direction of the pump piston 3, so that the beginning of delivery is adjusted in accordance with the position of the spool valve 4 relative to the sloping edge recess 5.

Fig. 2 shows actuation of the spool valve by a lever. In addition to the components of the pump element 1 shown in Fig. 1 and given the same reference numbers, the shaft 6.1 has a lever 6.2. The advantage of attaching the lever 6.2 to the shaft 6.1 is that the stepping motor 8 can be disposed at any desired position, as shown in Figs. 3 and 4. As an alternative to using the lever 6.2, the spool valve 4 e.g. by attaching gearwheels or belt drives or the like for rotating the motor 8 on the shaft 6.1. In this manner the transmission between the control shaft 8.1 and the spool valve 4 or shaft 6.1 can be geared down for the purpose of high-precision adjustment.

can be actuated in other ways, Fig. 3 shows the adjustment of the beginning of delivery of a single pum7element 1, using a single7stepping motor 8. A partly-shown pump element 1 has a lever 6.2 prolonging the shaft 6.1 and connected to the stepping motor 8 via a forcetransmitting device, shown here in the form of a lever 9. If the power- transmitting device 9 is suitably constructed, the stepping motor 8 can be positioned wherever required.

2 Fig. 4 shows the adjustment of the beginning of delivery of more than one pump element 1, using a single stepping motor 8. The pump elements 1, likewise shown in part, have shafts 6.1 bearing levers 6.2 and are connected to the stepping motor 8 via the power-transmitting device 9. In this case, as in Fig. 3 the power-transmitting device 9 can be given any suitable construction. Alternatively the powertransmitting device 9 can be a belt drive or a gearwheel drive or the aforementioned means in combination with other power-transmitting devices.

Fig. 5 shows a control device and components thereof. A control device 10 associated with the individual stepping motors 8 has a store 11, preferably a performance-graph store, an actuating unit 12 and a computer unit 13. The control device 10 has sensor inputs 14 for detecting operating parameters of the engine. Depending on the operating paimeters detected by the -sen-sor inputs 14, adjustment of the beginning of delivery is calculated computer unit 13, or stored characteristic curves are selected from store 11. In order to input values into the store 11, the control device 10 is connected to a data i.nterface 15 to which an input unit 16 can be connected. Unit 16 can be used for inputting values for at least one aforementioned characteristic curve, or values (supporting the in the points) for calculating a characteristic curve in the store 11.

In an alternative embodiment of the invention, individual actuating units 12 are associated with individual stepping motors 8, so that the actuating device 10 actuates the individual actuating units 12, which in turn operate the stepping motors 8. Irregularities in the pump elements due e.g. to manufacturing tolerances or ageing, are compensated in that each individual pump element is associated with an individual stepping motor. The compensation can be brought about e.g. by the stepping motor 8 moving the spool valve 4 into the end positions (the largest or smallest beginning of delivery) and storing the same positions in the control device 10. This new storing of end positions can be carried out at certain time intervals or whenever the diesel engine is started up. If the end positions of the spool valve 4 are detected and stored whenever the engine is started up, ageing of the pump element 1 can advantageously be detected and compensated immediately.

Fig. 6(a) and (b) by way of example show a characteristic curve 17, 18 respectively, representing the adjustment (the angle) of the beginning of delivery in dependence on the engine speed. The characteristic curve in Fig. 6(a) represents e.g. the adjustment of the beginning of delivery in dependence on the speed of a cold engine, whereas the second characteristic 18 is e. g. for an engine heated up by operation. The two characteristics 17 and 18 are advantageously stored in the store 11 and are selected in dependence on an engine operating variable detected via a sensor input 14 of the control device 10. Alternatively, more than two characteristic curves can be called up in store 11, depending on one or more operating parameters of the engine so that, depending on the called-up characteristic, the actuating unit 12 actuates the stepping motor 8 so as to set the beginning (the angle) of delivery required by the called-up characteristic. In an alternative embodiment of the invention, the input unit 16, using the data interface 15, can input values 17.1 to 17.4 or 18. 1 to 18.4 into the store 11, enabling the computer unit 13 to calculate the required characteristic. The number and position of fh-e supporting points for-calculating a characteristic can vary within wide limits, so that special characteristic curves can be set depending on the kind of engine and the use made thereof.

c L A I M S 1. A fuel injection device for diesel engines comprising at least one pump element (1) consisting of a cylinder (2) and a piston (3) movable by a cam and having a sloping edge (5), a movable spool valve (4) for adjusting the beginning of delivery being disposed coaxially around the pump piston (3), characterised in that the spool valve (4) of the pump element (1) is connected for power transmission purposes to a control shaft (8.1) of a stepping motor (8).

2. A fuel injection device according to claim 1, characterised in that at least one transmission means is disposed between the spool valve (4) and the control shaft (8.1).

3. A fuel injection device according to claim 2, characterisei-in that the transmission-means is a shaft (6.1) disposed in the pump cylinder and, on the end face facing the pump piston (3), is provided with an eccentric prolongation (7) engaging in a recess in the spool valve (4).

4. A fuel injection device according to claim 2 or 3, characterised in that the transmission means comprises a power -transmit ting device (9) disposed between the shaft (6.1) and the control shaft (8.1).

5. A fuel injection device according to any of claims 2 to 4, characterised in that the transmission means of at least two pump elements (1) are connected to the control shaft (8.1) by a common powertransmitting device (9).

6. A fuel injection device according to any of the preceding claims, characterised in that a control device (10) is provided with a store (11), more particularly a performance graph store, and is connected to at least one stepping motor (8), the control device (10) having sensor inputs (13) for detecting operating parameters of the engine and an actuating unit (12) which actuates a stepping motor (8) in dependence on a characteristic curve and/or at least one operating parameter of the engine.

7. A fuel injection device according to any of the preceding claims, characterised in that the control device (10) has a data interface (14) and means for calculating the adjustment of the beginning of delivery, more particularly in dependence on values inputtable into the store (11).

8. A fuel injection device according to any of the preceding claims, characterised in that an input unit (15) can be connected to the control device (10) via the data interface (14).

9. A fuel injection device according to any of the preceding claims, characterised in that the inputtable values are stored in the store (11).

10. A fuel injection device according to any of the preceding claims, characterised in that each stepping motor (8) associated with an individual pump element (1) compensates irregularities in the pump elements.

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