GB2042067A

GB2042067A - Diesel engine cylinder fuel injection system

Info

Publication number: GB2042067A
Application number: GB8002548A
Authority: GB
Original assignee: Sulzer AG; Gebrueder Sulzer AG
Current assignee: Sulzer AG
Priority date: 1979-01-25
Filing date: 1980-01-25
Publication date: 1980-09-17
Also published as: IT8019329A0; DE2906297C2; AT367864B; DK147951C; JPS55101735A; CH635167A5; IT1129583B; GB2042067B; DK147951B; JPS6025611B2; DE2906297A1; SU900822A3; ATA122579A; DK17680A

Abstract

A diesel engine cylinder injection system, the valve-controlled fuel injection pump of which comprises a pump cylinder (1) with a reciprocable plunger (9), an inlet valve (3) and a by-pass valve (4). A control lever (15) for operating the inlet valve 3 is pivotable by the plunger 9 about an adjustable pivot 22. An actuator arrangement is provided which sets the pump operation to a start condition and, after expiry of a predetermined start condition time, changes it over to normal operation. The timing at which delivery begins depends on the position of the pivot 22 which is different for start and normal running conditions. A rocking lever (24) connected to a shaft (23) on which the pivot 22 is eccentrically carried is movable by an actuator device 25 between a normal operation position (24N), equivalent to a normal operation delivery beginning, and a start condition position (24S) equivalent to a start condition delivery beginning. A means (26) is also provided for adjustment of the start condition position (24S), together with means (27) for adjusting the normal operation position (24N) of the rocking lever (24). A control system (28) for the actuating device (25) delivers control signals (SA, SR) and a timing device (29) monitors the time of the start condition and triggers the return signal (SR) after expiry of such time are also provided. <IMAGE>

Description

SPECIFICATION Diesel engine cylinder fuel injection system This invention relates to an injection system for a diesel engine cylinder, the valve-controlled fuel pump of which comprises a pump cylinder with a plunger, an inlet valve which determines the beginning of the pump delivery period, and a by-pass valve, which determines the end of the pump delivery period, the plunger being driven via a drive mechanism from a control shaft, and the inlet valvemember being driven by the drive mechanism via a pivotable control lever.

A valve-controlled fuel pump of this kind is described in Swiss Patent No. 489,707. The valves are disposed in the pump body, in which a pump piston or plunger is guided in a bore. A pressure chamber is constructed in the pump body and is connected via a delivery valve to a delivery conduit leading to an injection valve. The inlet valve is in an inlet duct of the pump body connected to a feed conduit. The by-pass valve controls the flow of fuel to a by-pass duct in the pump body, the by-pass duct being connected to a by-pass pipe.

The plunger is driven via a cam on the control shaft and a drive piston which also drives the valve member of the inlet valve and of the bypass valve via a pivotable control lever in each case. In some cases the by-pass valve control lever is disposed pivotally on the eccentric of an eccentric shaft so that the pivot axis of the control lever is adjustable by turning the eccentric shaft about its major axis.

In this way it is possible to influence the stroke of the by-pass valve and hence the end of the delivery period and the amount delivered.

The eccentric shaft may be operatively connected to an engine speed governor so that the amount delivered is controlled in dependence on the load during the entire period of operation. The control lever driving the inlet valve is pivotable about a fixed pivot axis and is so disposed in relation to the drive piston that the beginning of the injection period takes place a predetermined interval of time before the top dead centre position of the piston of the engine.

Heavy duty diesel engines require large quantities of fuel even in the part-load range.

For thermodynamic reasons, these quantities of fuel are injected earlier (with respect to the top dead centre position of the engine piston) than was previously the case, in order to comply with the requirements in respect of improved consumption and exhaust content specifications. As a result of the injection and ignition time being advanced, the cold-start behaviour of the engine is unfavourably influenced by loud combustion nose, i.e. loud knocking, and the steep pressure gradients associated with knocking, and high peak pressures during combustion, also mean an increased load on the engine transmission.

The object of this invention is to provide a system of the type defined hereinbefore whereby the beginning of the delivery period can be temporarily delayed during an engine start condition period; and subsequently returned to an advanced position, which is the favourable setting for normal operation.

Accordingly the present invention provides an injection system for a diesel engine cylinder, the valve-controlled fuel pump of which comprises a pump cylinder with a plunger, an inlet valve which determines the beginning of the pump delivery period, and a by-pass valve, which determines the end of the pump delivery time, the plunger being arranged to be driven via a drive mechanism from a control shaft and the inlet valve-member being driven by the drive mechanism via a pivotable control lever, comprising an actuator means which sets the pump to a start condition and, after expiry of a predetermined start condition time, re-sets it to normal operation, the timing at which delivery begins under the start condition differing from the timing at which delivery begins under normal operation, including an eccentric shaft, the eccentric axis of which serves as a pivot axis for the pivotable control lever, and and a rocking lever rigidly connected to the eccentric shaft and pivotable about its major axis between a normal operation position equivalent to an angular position of the eccentric shaft in which the inlet valve stroke produces the normal operation timing and as second position equivalent to an angular position of the eccentric in which the inlet valve stroke produces the start condition timing, and including an actuating device arranged to move the rocking lever into its start condition position in a working stroke and into its normal operation position in a return stroke, the actuating device having means for adjusting the normal operation position of the rocking lever and means for adjusting the start condition position of the rocking lever, and means arranged to control the actuating device which is operatively connected to a timing device arranged to determine the length of the start condition o,sra- tion.

The invention offers the advantageous possibility of operating under starting conditions in which the timing of the beginning of the delivery period and hence the ignition timing is retarded during the engine warm up period.

The high peak pressures during combustion and the steep pressure gradients otherwise occurring at high powers, together with the associated knocking and increased transmission stressing, are thus avoided. Nevertheless, the early ignition timing with its advantages is retained during normal operation. The system is also simple, cheap and reliable and allows various embodiments and hence substantially easy adaptation to various design and application criteria.

According to one preferred embodiment of the invention, the actuating device comprises a piston and cylinder unit actuated by a fluid pressure medium, and the means for adjusting the start condition position of the rocking lever comprises a stop limiting the working stroke of a piston of the unit, and the means for adjusting the normal operation position of the rocking lever comprises a stop limiting the return movement of the piston. The piston and cylinder unit may be of the pneumatic or hydraulic type. In high-power diesel engines such as marine diesel engines and stationary diesel power plants, a pneumatic unit is preferable because it can be satisfactorily incorporated in the pneumatic remote-control system normally used in such an engine.Adjustment of the end position of the rocking lever can readily be effected by means of the stops, which are advantageously made to be adjustable over relatively wide limits. In this.way adjustments of the end position of the rocking lever, and hence of the timing of the beginning of the delivery period, can be readily carried out both for the start condition and for normal operation.

The timing device is preferably a chamber emptying system, which may comprise a throttle, a valve, a slide or a restrictor, by means of which a working medium can be emptied from a pressure chamber during the start condition period. Emptying of the chamber is arranged to begin with the beginning of the start condition or start-up of the engine and proceeds during this state of operation at a speed such that when the predetermined start condition time has expired the pressure in the pressure chamber of the unit has dropped to a given value. In this way if the piston of the actuating device experiences the pressure in the chamber, the pressure force on the piston will reach a value which is less than the force of a return spring provided to act on the other side of the piston.Consequently, the piston will then perform its return stroke and return the rocking lever to its normal operation position.

A device acting on the timing device may also be provided for adjusting the period of the start condition. This device may also be arranged to determine the start condition period in accordance with instantaneous operational parameters, such as the engine temperature, engine loading, fuel quality, and so on. In this way the start condition can be adapted to existing conditions and be optimized in relation thereto.

Preferably, the actuating device has a control valve which can be moved by a start signal out of a normal position into a start position in which it establishes connection between the pressure chamber of the actuating device and a source of fluid under pressure, in order abruptly to pressurize the pressure chamber; and the control valve automatically returns to its normal position by interruption of the start signal, and in its normal position it establishes connection between the then pressurized pressure chamber and the emptying system and initiates the emptying operation, and remains in its normal position until the next start signal. The start signal may act on the control valve automatically simultaneously with'the starting of the engine or be independent of the engine starting, in which case it is produced by manual actuation of a starting means.The control valve may be of the electromagnetic or pneumatically actuated type.

In order to promote a fuller understanding of the above and other aspects of the invention, some embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a section of a valve-controlled fuel pump with a control system which is shown partly as a block diagram, Figure 2 is an embodiment of the actuator device in its normal operation position, and Figure 3 shows the actuator device of Fig.

2 in the start condition position.

In Fig. 1, there is shown a fuel pump which comprises a pump body 1, a pressure chamber 2 formed therein, an inlet valve 3, a bypass valve 4 and a delivery valve 5. The inlet valve 3 is disposed in an inlet duct 6 connected to a fuel feed pipe (not shown).

The by-pass valve 4 is disposed in a by-pass duct 7 connected to a by-pass pipe (not shown), and the delivery valve 5 is disposed in an outlet duct 8 to which a delivery pipe (not shown) is connected and leads to a fuel injection valve (not shown) associated with a diesel engine cylinder. A plunger 9 is disposed for displacement against the force of a coil spring in a bore arranged axially with respect to the delivery valve 5 in the pump body 1.It is driven via a control shaft 10 having a cam 10', a roller 11, and a drive tappet 1 2. The tappet 1 2 also drives the valve member 1 3 of the intake valve 3 via a pivotable control lever 1 5 and a push rod 16, and the valve member 14 of the by-pass valve 4 via a pivotable control lever 1 7 and a pushrod 1 8. The control lever 1 7 is disposed pivotally in manner known per se on an eccentric 1 9 of an eccentric shaft 20 which is connected for control purposes to a speed governor (not shown) via a linkage 21. Rotation of the eccentric shaft 20 about is major axis adjusts the eccentric axis, i.e. the pivot axis of the control lever 17, so that the stroke position of the by-pass valve 4, and hence the timing of the end of delivery and the quantity delivered by the fuel pump are influenced. In this way, the amount delivered is controlled in dependence on the load during the entire period of operation.

The control lever 1 5 is mounted pivotally on the eccentric 22 of an eccentric shaft 23, so that turning about its major axis causes the pivot axis of the control lever 1 5 to be adjusted together with the position of the inlet valve 3 and hence the start of delivery. A rocking lever 24 rigidly connected to the eccentric shaft 23 is pivotable between two end positions 24N and 24S about the major axis of the eccentric shaft 23.The end position 24N is the normal operating position and is equivalent to an angular setting of the eccentric 22 such that the movement of the inlet valve times the start of delivery under normal operating conditions, while position 24S is the starting position and corresponds to an angular position of the eccentric 22 in which the inlet valve movement times the start of delivery under starting conditions.

The rocking lever 24 is connected to an actuating device 25 which, in a working stroke, moves it out of its normal operating position 24N into its starting condition 24S and, in a return stroke, moves it out of that position 24S into its normal operating position 24N Adjustment of the device 25 to the rocking lever end positions 24N and 24S determined by calculation, is provided by two devices 26 and 27, of which the former serves for adjustment of the starting condition position 24S while devide 27 is used for adjustment of the normal operation position 24N The devices 26 and 27 are adjustable between certain limits.

The device 25 is also connected to a control system 28 which delivers the control signals SA and SR for the working and return strokes respectively of the device 25. A timing device 29 is operatively connected to the control system 28 and, after a required starting operation time has elapsed, it delivers a signal SD which triggers the reset signal 5R On application of a signal S to the control system 28 (the signal may be automatically generated on starting of the engine or be produced by manual actuation of a signal source), the working stroke of the control device 25 is triggered and the rocking lever 24 is brought into its starting condition position 24S. The signal S is also fed to the timing device 29, which initiates measurement of the period of the starting condition and, after expiry of the required period, delivers the signal SD to the control system 28, so that the latter feeds the reset signal SR to the adjusting device 25 and triggers the return movement so that the rocking lever 24 is moved back into its normal position 24N A device 30 operatively connected to the timing device 29 may also be provided in order to adjust the duration of the starting condition. This device 30 may also have the function of receiving operating parameters indicative of instantaneous state of the engine, e.g. the engine temperature, the instantaneous engine loading, the fuel quality, and so on, calculating a start condition time from these parameters, and feed them as a signal SD1 to the timing device 29.

Referring to Figs. 2 and 3, the actuating device 25 may be in the form of a piston and cylinder unit 31 operating with air as the working medium, while the control system 28 is in the form of a pneumatic control valve 35, and the timing device 29 is in the form of a pressure chamber emptying system having an outlet 41 the flow cross-section of which is adjustable. A linkage comprising two articulated elements 33, 34 transmits the movement of a piston rod of unit 31 to the rocking lever 24 (not shown in Figs. 2 and 3). A stop 36 consisting of two nuts and adjustable on the piston rod 32 limits the working stroke of a piston 37 to the right in the drawing and is thus used to adjust the start condition position 24S of the rocking lever 24.An externally screwthreaded second stop 38 adjustable in the axial direction of the unit 31 is held fast by the nut 39 in relation to the unit 31; it limits the return movement to the left in the drawing and is thus used to adjust the normal operation position 24N of the rocking lever 24.

Fig. 2 shows the normal position and Fig. 3 the start position of the control valve 35 provided as the control system 28. In its normal position, it connects the pressurized chamber 40 of the uit 31 to the emptying system outlet 41 via a conduit 48, while in the start position it connects the chamber 40 to a source of fluid under pressure, which is connected to the valve 35 via a conduit 42.

The control valve 35 can be moved from its normal position into its start position by means of a start signal S applied automatically via a conduit 43 or manually via a press button 44. In the start position of the valve 35, the pressure chamber 40 is abruptly pressurized, the piston 37 performing its working stroke limited by the stop 36 and at the same time rocking the lever 24 into its start condition position 245. In these conditions air escapes on the other side of the piston 37 via the bleed bore 47 of the unit 31. As soon as the start signal S is interrupted, the control valve 35 is returned to its normal position by its return spring 46, and in this position the pressure chamber 40 is gradually emptied through the emptying system outlet 41 so that there is a gradual pressure drop in the pressure chamber 40.

The flow cross-section of the outlet 41 is so adjusted that when the required period of the start condition has expired the pressure in the pressure chamber just drops to a value at which the force acting on the piston 37 on the pressure chamber side is less than the force exerted on the other side of the piston by a return spring 45. The piston 37 thus performs its return stroke and returns to the normal operation position shown in Fig. 2, the rocking lever 24 at the same time returning to its normal operation position 24N In other embodiments of the invention, the actuating device 25 for pivoting the lever 24 may be an electromagnet with a rectilinearly displaceable core or an electric servomotor.

The control system 28 and the devices 29 and 30 would then be electrical and/or electronic systems in which a number of mechani cai inputs, e.g. the position of the drive tappet 12 per unit if time, would have to be input in the form of electrical signals.

Claims

1. An injection system for a diesel engine cylinder, the valve-controlled fuel pump of which comprises a pump cylinder with a plunger, an inlet valve which determines the beginning of the pump delivery period, and a by-pass valve, which determines the end of the pump delivery time, the plunger being arranged to be driven via a drive mechanism from a control shaft and the inlet valve-member being driven by the drive mechanism via a pivotable control lever, comprising an actuator means which sets the pump to a start condition and, after expiry of a predetermined start condition time, re-sets it to normal operation, the timing at which delivery begins under the start condition differing from the timing at which delivery begins under normal operation, including an eccentric shaft, the eccentric axis of which serves as a pivot axis for the pivotable control lever and a rocking lever rigidly connected to the eccentric shaft and pivotable about its major axis between a normal operation position equivalent to an angular position of the eccentric shaft in which the inlet valve stroke produces the normal operation timing and a second position equivalent to an angular position of the eccentric in which the inlet valve stroke produces the start condition timing, and including an actuating device arranged to move the rocking lever into its start condition position in a working stroke and into its normal operation position in a return stroke, the actuating device having means for adjusting the normal operation position of the rocking lever and means for adjusting the start condition position of the rocking lever and means arranged to control the actuating device which is operatively connected to a timing device arranged to determine the length of the start condition operation.

2. A system according to Claim 1, in which the means for adjusting the start condition position of the rocking lever and the means for adjusting the normal operation position of the rocking lever are adjustable.

3. A system according to Claim 1 or 2, in which the actuating device comprises a fluid pressure operable piston and cylinder unit, and the means for adjusting the start condition position of the rocking lever comprises a stop limiting the working stroke of a piston of the unit and the means for adjusting the normal operation position of the rocking lever comprises a stop limiting the return movement of the piston.

4. A system according to Claim 3, in which the timing devices comprise means for releasing pressure medium arranged to be connected to the piston and cylinder unit.

5. A system according to Claim 4 in which the control means comprises a control valve which may be moved by a start signal out of a normal position into a start position in which it establishes connection between a working pressure chamber of the piston and cylinder unit and a source of fluid under pressure, in order abruptly to pressurize that pressure chamber, the control valve being arranged to automatically return to its normal position on interruption of the start signal, and which in its normal position establishes connection between the so pressurized chamber and the means for releasing pressure medium to release the pressure in the chamber, the valve being further arranged to remain in its normal position until the next start signal.

6. A system according to Claim 5, in which the start signal is a pressure signal which is transmitted automatically to the control valve simultaneously with the starting of the engine.

7. A system according to Claim 5, in which the start signal may be applied to the control valve by manual operation of a starting means.

8. A system according to any one of Claims 4 to 7 in which the flow outlet crosssection of the pressure release means is adjustable to adjust the start condition time.

9. A system according to any preceding Claim, comprising a device acting on the timing device for adjustment of the start condition time.

10. A system according to Claim 9, in which the device acting on the timing device is arranged for calculation of the start condition time in accordance with instantaneous operation parameters of the engine, and for delivery of a corresponding signal to the timing device.

11. An injection system for a diesel engine substantially as herein described with reference to the accompanying drawings.