GB2067663A

GB2067663A - Safety Device for a Diesel Engine Equipped with a Supercharger

Info

Publication number: GB2067663A
Application number: GB8100863A
Authority: GB
Original assignee: Diesel Kiki Co Ltd
Current assignee: Bosch Corp
Priority date: 1980-01-14
Filing date: 1981-01-13
Publication date: 1981-07-30
Also published as: DE3100711A1

Abstract

A safety device is fitted to a control device (1) which operates in dependence upon charging pressure and which, by means of a wall (8) movable by the charging pressure (pL), acts upon a delivery quantity adjusting member (6) of a fuel injection pump in a direction to increase the delivery quantity. In the event of an inadmissibly high charging pressure (pL), an electromagnetic control member (19) controlled by an electronic control device (20) directly or indirectly returns the movable wall (8) into a position in which the delivery quantity adjusting member (6) establishes a reduced delivery quantity. The member (19) may be a solenoid valve which modifies the pressure acting on the wall (8) or a lever operated by a solenoid. <IMAGE>

Description

SPECIFICATION Safety Device for an Injection-Type Internal Combustion Engine Equipped With a Supercharger The invention relates to safety devices for fuel injection pumps of injection-type internal combustion engines fitted with a supercharger, such as for supercharged diesel engines, in which the quantity of intake air delivered into the engine cylinders is increased by the supercharger.

It is known to provide a control device constituted by a so-called smoke limiter or supercharging-pressure-dependent full load stop (U.S.A. Patent Specification No. 2,767,700 or U.S.A. Patent Specification No. 4,057,044) which, by utilizing the charging pressure, automatically establishes an injection quantity adapted to the increased quantity of air in the cylinder or limits the maximum admissible injection quantity adapted to the increased air quantity.

If the charging pressure increases to an inadmissibly high value as a result of damage to the charging blower or as result of a fault in the pressure-regulating device for the charging blower, the quantity of fuel injected is increased and is held at this value, as is shown by a solid curve a in Fig. 2 of the drawings. The engine speed thereby increases and, as a result of the increase in the horse power output of the engine, an extremely high torque is produced which can result in damage to the engine or its transmission or in failure of the control device operating in dependence upon the charging pressure.

The present invention provides a safety device for a fuel injection pump of an injection-type internal combustion engine equipped with a supercharger, which safety device is fitted to a control device having a wall which is movable by the charging pressure against the force of at least one, return spring, said wall separating an atmospheric chamber from a charging-pressure chamber to which the charging pressure is fed during normal operation and, as the charging pressure rises, displacing a fuel delivery quantity adjusting member of the fuel injection pump by means of transmission members in a direction to increase the delivery quantity, and which safety device comprises an electromagnetic control member controlled by an electronic control unit whereby, in the event of an inadmissibly high charging pressure, the movable wall of the control device is returned at least indirectly into a position in which the delivery quantity adjusting member controllable by the movable wall establishes a reduced fuel delivery quantity.

In the event of the charging pressure assuming inadmissibly high values, the electromagnetic control member reduces the quantity of fuel delivered by the associated fuel injection pump to an extent that the associated internal combustion engine or the control device cannot be damaged.

Advantageously the electronic control unit is adapted to deliver to the electromagnetic control member responsively to fault signals from sensors which are mounted on the engine and are connected to the electronic control unit.

Thus, further fault signals can be processed in addition to the charging pressure. Preferably, the transmission member comprises a thrust rod connected to the movable wall and its stroke is limited in a direction to control this reduced delivery quantity by a stop bolt which is loaded by a spring and which serves as a yieldable stop. It is thereby possible to reduce the delivery quantity below the quantity of fuel which needs to be injected during intake operation of the engine and which is limited by the control device.

In one embodiment, the electromagnetic control member comprises a solenoid valve which is incorporated in a line supplying charging pressure to the charging-pressure chamber and which, when in a first switching position, that is to say, when in its normal operating position, maintains this line open and, when in a second switching position controlled by the electronic control unit, connects the charging-pressure chamberto a source of vacuum.

In the event of a fault, the solenoid valve connects the charging-pressure chamber to a source of vacuum which produces the required adjusting force in an advantageous manner. In another embodiment of the invention, the solenoid valve can connect the atmospheric chamber of the control device to a source of overpressure whose pressure must lie above the maximum charging pressure. In a further embodiment, the solenoid valve when in its normal operating position shuts off a line connecting the charging-pressure chamber to the atmospheric air, and opens the said line in the event of a fault, so that the action of the charging pressure on the movable wall is eliminated, and the return spring returns the device to a position in which the delivery quantity adjusting member of the injection pump only establishes the injected quantity of fuel required during intake operation.

In yet another embodiment a very simple construction is achieved by arranging for the solenoid valve, in the form of a four-port twoposition valve, to change over the lines leading to the chargingpressure chamber and to the atmospheric chamber, thus resulting in a reverse direction of operation. The movable wall can thereby be urged to a position to control an intake quantity, or to an even lower position.

In a further alternative embodiment, the electromagnetic control member comprises an actuating electromagnet which, in the event of a fault, actuates the thrust rod of the movable wall in a direction to reduce the fuel delivery quantity established by the delivery quantity adjusting member.

The invention is further described, by way of example, with reference to the drawings, in which Figure 1 is a sectional illustration of a first embodiment of a safety device constructed in accordance with the invention; Figure 2 is a graph in which the charging pressure is plotted against the regulating travel for all the embodiments, and Figures 3 to 6 show respectively second to fifth embodiments of safety device.

Figure 1 shows a control device 1 which operates in dependence upon supercharging pressure and whose right hand end (as viewed in the drawing) is secured to a fuel injection pump (not illustrated) for a diesel engine fitted with a supercharger. A two-armed lever 4 constituting a transmission member is pivotally mounted about a pivot pin 5 in a chamber 3, enclosed by a housing 2. The top end 4a of the lever 4 is in contact with the front end 6a of a regulating rod 6 serving as a fuel delivery quantity adjusting member. A spring 7 abuts against the end 6a of the regulating rod 6 and its force acts upon the top end 4a of the lever 4 to urge the lever 4 in an anti-clockwise direction. The bottom end 4b of the lever 4 thereby engages an actuating pin 14 of a thrust rod 12. The outer edge of an adjusting diaphragm 8, serving as a movable wall, is clamped between the housing 2 and a cover 9.A charging-pressure chamber 10 to which the charging pressure pal is fed, and an atmospheric chamber 10 are separated from one another by the diaphragm 8.

The thrust rod 12 also serves as a transmission member and is rigidly connected to the adjusting diaphragm 8. One end 1 2b of the thrust rod 12 extends into the chamber 3 through a bore 13 formed in the housing 2, and the actuating pin 14 is secured to the end 1 2b of the thrust rod 12. A return spring 15 is located and supported in the atmospheric chamber 11 and presses against the adjusting diaphragm 8 and its adjusting force maintains an end 1 2a, extending into the charging-pressure chamber 10, of the thrust rod 12 in contact with a stop bolt 16 which is fitted in the cover 9 and which serves to limit the stroke of the thrust rod 12. The stop bolt 16 is subjected to the force of a spring 17 and thus acts as a resilient stop.

The charging-pressure chamber 10 is sealed in an air-tight manner by the adjusting diaphragm 8 and the cover 9 and the pressure of the air change, subjected to the charging pressure PL is fed from the intake manifold of the engine to the chamber 10 by way of a line 18.

The line 18 incorporates a solenoid valve 19 which constitutes an electromagnetic control member and which operates as a three-port, twoposition changeover valve. The charging pressure p, is fed to the charging-pressure chamber 10 when the solenoid valve 19 is in its normal operating position, and a vacuum Pu produced by a vacuum source indicated at 38 is fed to the charging-pressure chamber 10 when the solenoid valve 19 is changed over.

The solenoid valve 19 is changed over by the output of an electronic control unit 20 and, when the charging pressure p, assumes inadmissibly high values, such as 700 mmHg and in excess thereof in the practical embodiments to which the graph of Figure 2 applies, the pressure signals SD coming from a charging-pressure sensor 21 are fed as input signals to the control unit 20 in which they are amplified and then fed as change-over signals Su to the solenoid valve 19. An indicator 22 indicates when faults have occurred as a result of, for example, the inadmissibly high charging pressure. The maximum position of the regulating rod 6 at full load is determined by a stop screw 25 (for example, at the regulating travel RW=12 mm in the graph of Figure 2).

When, in the construction of the control device 1 described hitherto, the associated diesel engine equipped with a supercharger, such as an exhaust gas turbocharger, is running, the charging pressure PL is conducted to the charging-pressure chamber 10 through the line 18, and the rise in the charging pressure p, actuates the adjusting diaphragm 8 against the resistance of the return spring 15, and thus the thrust rod 12 is urged to the right into the chamber 3.

Consequently, the actuating pin 14 is correspondingly displaced. The lever 4 is thereby pivoted in an anti-clockwise direction about the pivot pin 5 and, as a result of this pivotal movement, the top end 4a of the lever 4 is moved to the left. In conformity with this change of position, the regulating rod 6 is displaced to the left by the spring 7 to increase the quantity of fuel, that is to say, in a direction indicated by an arrow 6b shown in the regulating rod 6 (see plus direction of the arrow), and a quantity of fuel associated with the air charge fed tithe engine is metered and injected.

If the charging blower then develops a fault for some reason or other, particularly if its pressure regulator fails and the charging pressure p, rises and assumes inadmissibly high values, the pressure signals SD coming from the chargingpressure sensor 21 are fed as an input to the control unit 20. The control unit 20 then feeds the solenoid valve 19 with change-over signals Su which change over the solenoid valve 19.

Consequently, vacuum Pu is fed to the chargingpressure chamber 10 by way of the line 18, and the adjusting diaphragm 8 and the thrust rod 12 are displaced to the left towards the stop bolt 1 6 with the assistance of the adjusting force of the return spring 1 5. With a corresponding adjusting force, the force of the spring 17 acting on the stop bolt 16 is overcome, so that the lever 4 moves the regulating rod 6 of the fuel injection pump further to the right, that is to say, in a direction to reduce the quantity of fuel (see minus direction of the arrow 6b). The position then assumed by the regulating rod 6 is indicated by a broken line b contiguous with a curve a in the graph of Figure 2 in which the regulating travel Rw of the regulating rod 6 is plotted against the charging pressure PL The quantity of fuel injected is thereby reduced to approximately half the maximum quantity of fuel injected and the engine speed is also reduced, with an adequate margin of safety, to an extent that will prevent damage to the engine or destruction of the engine or the adjusting diaphragm 8. The indicator 22 indicates that a fault exists. The driver or the operator of the engine is thereby alerted, and it can be seen that the performance of the engine has dropped or it can be established why the performance of the engine has dropped.

If required, the temperature signals STW coming from a water temperature sensor 23 for detecting the water temperature or from an oil temperature sensor 23 for detecting the oil temperature can also be fed to the control unit 20, so that the output of the engine can also be reduced by taking into account these signals detecting over-heating of the engine.

Figure 3 shows a control device 1', constituting a second embodiment of the present invention, in which an elevated pressure is introduced into the atmospheric chamber 11 from, for example, a source 39 of compressed air when the charging pressure PL has risen to an inadmissible extent. For this purpose, the atmospheric chamber 11 is sealed in an air-tight manner, that is to say, a bore is not provided between the chambers 11 and 3 in the housing 2.

A line 26 is additionally connected to the atmospheric chamber 11 and incorporates a solenoid valve, designated 19' in the present instance, which serves as the electromagnetic control member. When the valve 19' is in its illustrated normal operating position, the atmospheric chamber 11 is open to the atmospheric air under atmospheric pressure PA However, when the solenoid valve 19' is changed over, a positive pressure, that is to say, a pressure p, lying above the maximum possible charging pressure, is fed to the atmospheric chamber 11 by way of the line 26. This positive pressure p, is fed from a pressure pump located on the engine or in the motor vehicle, such as the air pump of the brake system.The other features of this second embodiment are otherwise the same as those of the first embodiment of Figure 1. For this reason, the same reference symbols have also been used in Figure 3.

In the control device 1' described with reference to Figure 3, if the charging pressure p, rises to an unusually high value as a result of damage to the charging blower, pressure signals SD coming from the charging-pressure sensor 21 are fed to the control unit 20 and the control unit 20 applies change-over signals Su to the solenoid valve 19' to change over the solenoid valve 19'.

Consequently, the elevated pressure p, is fed to the atmospheric chamber 11, so that the thrust rod 12 is displaced to the left against the charging pressure PL and against the resistance of the spring 7, but with the assistance of the spring 1 5, so that the regulating rod 6 is moved in a direction to reduce the quantity of fuel injected, and thus the quantity of fuel injected is reduced to approximately half the quantity in accordance with the broken line b of Figure 2. In this manner, the same effect as in the first embodiment described is achieved.

Figure 4 shows a third embodiment of a control device 1" in which the interior of the charging-pressure chamber 10 is opened to the outside air (atmosphere) in the event of the charging pressure p, attaining inadmissibly high values. For this purpose, a line 27 is connected to the charging-pressure chamber 10 and incorporates a solenoid valve 28 which acts as the electromagnetic control member and which is constituted by a two-port, two-position valve.

When in its illustrated normal operating position, the solenoid valve 28 closes in line 27, so that the charging-pressure chamber 10 does not communicate with the atmosphere. However, when the valve 28 is changed over, the chargingpressure chamber 10 is opened to the atmosphere. All the other features of this third embodiment are the same as those of the first embodiment and of the second embodiment of Figure 3, so that, here also, the same reference numerals have otherwise been used.

If the charging pressure p, rises to an inadmissibly high value when using the control device 1" described with reference to Figure 4, pressure signals SD coming from the chargingpressure sensor 21 are fed to the control unit 20 and are transmitted as change-over signals Su to the solenoid valve 28, so that the solenoid valve 28 is changed over. Consequently, the chargingpressure chamber 10 is opened to the atmosphere, so that the state established is the same as that which would be established if a charging pressure p, were not fed. The adjusting diaphragm 8 is therefore moved to the left by the return spring 15, that is to say, until the end 1 2a of the thrust rod 1 2 abuts against the stop bolt 1 6.The lever 4 is thereby pivoted in a clockwise direction, and the regulating rod 6 is moved in a direction to reduce the quantity of fuel. In this case, the quantity of fuel injected is only reduced to the full load quantity required during normal intake operation of the engine. This operation is shown in Figure 2 by a dash-dot line c on a level with the position RW:1 0 mm of the regulating rod shown at the start of curve a. However, approximately the same effect as that in the previously described embodiments can thus be obtained.

In the fourth embodiment of a control device 1 n illustrated in Figure 5, a solenoid 29a of an actuating electromagnet 29, serving as the electromagnetic control member, is provided at the bottom end of the housing 2, an armature 30 being held in position in the solenoid by springs 31 and 32. A lever 33 is articulated to the armature 30 and is pivotable about a bearing pin 34.

That end 33a of the lever 22 which is remote from the actuating electromagnet 29 is located opposite that end 1 2b of the thrust rod 12 which extends into the chamber 3. The other components illustrated in Figure 5 are the same as those of the first embodiment described with reference to Figure 1, so that they will not be described again.

In this fourth embodiment, if an inadmissibly high charging pressure p, occurs, such as a charging pressure of 700 mm Hg and in excess thereof for the case of operation on which the graph of Figure 2 is based, the pressure signals SD coming from the charging pressure sensor 21 are fed as an input to the control unit 20 where they are amplified and then fed as change-over signals 8u to the solenoid 29a. The armature 30 of the actuating electromagnet 29 is thereby pulled in, and the lever 33 pivots in an anti-clockwise direction and its front end 33a strikes against the end 1 2b of the thrust rod 12, so that the thrust rod 12 is urged to the left.The stop bolt 1 6 is thereby subjected to excess force against the force of the spring 17, and the lever 4 moves the regulating rod 6 of the fuel injection pump to the right in the minus direction of the arrow 6b, that is to say, in a direction to reduce the quantity of fuel injected. This operation is indicated by the broken line b of Figure 2 and has already been described in detail with reference to the first embodiment.

Although the lever 33, which acts upon the thrust rod 12 in the return direction against the charging pressure p,, strikes directly against the thrust rod 12, it is also sufficient for the lever 33 to be in contact with the actuating pin 14, or it would also be possible to attach the thrust rod 12 to a member corresponding to the lever 33 and for such member then to be in contact with the armature 30 of the actuating electromagnet.

A fifth embodiment of the safety device in accordance with the invention, which, with respect to its function, is the simplest embodiment, is shown in Figure 6 and is constituted by a control device 1 tote which operates in dependence upon charging pressure and which, with respect to its components, line arrangements and function, comes nearest to the second embodiment which is illustrated in Figure 3 and which has been described with reference to Figure 3. The same parts have therefore been provided with the same reference numerals and, in the main, only the differing features will be discussed in the following description.

In the same manner as in the embodiments described hitherto, the charging-pressure chamber 10 is sealed in an air-tight manner by the adjusting diaphragm 8 and the cover 9 and communicates with the passage 18 through which the charging pressure p, if fed.

The atmospheric chamber 11 is formed by the adjusting diaphragm 8 and the housing 2 and differs from the conventional atmospheric chamber and, in the same manner as in the device 1' of Figure 3, is sealed in an air-tight manner relative to the outside and the chamber 3. When in the normal operating position illustrated, atmospheric air is introduced into the atmospheric air chamber 11 through a line 26 connected thereto.

A solenoid valve 36 operating as a changeover valve, and constituted by a two-position, four-port valve, is incorporated as an electromagnetic control member in the two lines 18 and 26. When the solenoid valve 36 is in its illustrated normal operating position designated 36a in the switching symbol, the charging pressure p, is fed to the charging-pressure chamber 10, and the atmospheric air is fed to the atmospheric chamber 11. When the solenoid valve 36 is in its second change-over position designated 36b, the charging pressure p, is fed to the atmospheric chamber 11, and the atmospheric air pressure PA is fed to the chargingpressure chamber 10.For this purpose, the solenoid valve 36 is changed over by the changeover signal Su coming from the control unit 20 if the charging pressure p, is extremely high (700 mmHg and in excess thereof in the graph of Figure 2) as already described with reference to the other embodiments, and/or if the engine is over-heated, that is to say, if the temperature of the cooling water is 950C and in excess thereof.

The signals SD, STW, 5TO coming from the charging-pressure sensor 21 and from the water temperature sensor 23 and from the oil temperature sensor 24 are then fed as an input to the control unit 20 in which they are amplified and then fed as change-over signals Su to the solenoid valve 36.

If the solenoid valve 36 is then in its second change-over position 36b, the charging pressure p, is introduced into the atmospheric chamber 11, and the pressure PA of the atmospheric air is introduced into the charging-pressure chamber 10, so that the adjusting diaphragm 8 urges the thrust rod 12 to the left against the force of the spring 17 beyond the position limited by the stop bolt 1 6. The regulating rod 6 is thereby displaced by the lever 4 in the minus direction of the arrow 6b against the force of the spring 7 to reduce the quantity of fuel injected, and the quantity of fuel injected is reduced to approximately half the maximum quantity of fuel injection (see broken line b of Figure 2). Thus, the speed of the engine is thereby reliably reduced to an extent that will suppress the development of an extremely high .

torque and thus protect the engine from damage or the like. In this embodiment also, a fault occurring in the charging blower or over-heating of the engine is indicated by the indicator 22.

It will be appreciated that, for reasons of durability for example, the adjusting diaphragm 8 used in the embodiments described with reference to Figures 1, 3 and 4 to 6 can be replaced by some other pressure/position transducer, such as a piston, which can be used as a movable wall.

Claims

1. A safety device for a fuel injection pump of an injection-type internal combustion engine equipped with a supercharger which safety device is fitted to a control device having a wall which is movable by the charging pressure against the force of at least one return spring, said wall separating an atmospheric chamber from a charging pressure chamber to which the charging pressure is fed during normal operation and, as the charging pressure rises, displacing a fuel delivery quantity adjusting member of the fuel injection pump by means of transmission members in a direction to increase the delivery quantity, and which safety device comprises an electromagnetic control member controlled by an electronic control unit whereby, in the event of an inadmissibly high charging pressure, the movable wall of the control device is returned at least indirectly into a position in which the delivery quantity adjusting member controllable by the movable wall establishes a reduced fuel delivery quantity.

2. A safety device as claimed in claim 1, in which the electronic control unit is adapted to deliver a change-over signal to the electromagnetic control member responsively to fault signals from sensors which are mounted on the engine and are connected to the electronic control unit.

3. A safety device as claimed in claim 1 or 2, in which the transmission member comprises a thrust rod connected to the movable wall and its stroke is limited in a direction to control this reduced delivery quantity by a stop bolt which is loaded by a spring and which serves as a yieldable stop.

4. A safety device as claimed in any of claims 1 to 3, in which the electromagnetic control member comprises a solenoid valve which is incorporated in a line supplying charging pressure to the charging-pressure chamber and which, when in a first switching position, that is to say, when in its normal operating position, maintains this line open and, when in a second switching position controlled by the electronic control unit, connects the charging-pressure chamber to a source of vacuum.

5. A safety device as claimed in any of claims 1 to 3, in which the electromagnetic control member comprises a solenoid valve which is incorporated in a line connecting the atmospheric chamber to the atmospheric air and which, when in a first switching position, that is to say, when in its normal operating position, maintains this line open and, when in a second switching position controlled by the electronic control unit, connects the atmospheric chamber to a source of overpressure.

6. A safety device as claimed in any of claims 1 to 3, in which the electromagnetic control member comprises a solenoid valve which is incorporated in a line connecting the chargingpressure chamber to the atmospheric air and, when in a first switching position, that is to say when in its normal operating position, shuts off this line and, when in a second switching position controlled by the electronic control unit, opens the charging-pressure chamber to the atmospheric air and thus reduces the pressure prevailing in the charging-pressure chamber to approximately atmospheric pressure.

7. A safety device as claimed in any of claims 1 to 3, in which the electromagnetic control member comprises a solenoid valve in the form of a four-port, two-position change-over valve which is incorporated in a line supplying the chargingpressure chamber with charging pressure and in a line connecting the atmospheric chamber to the atmospheric air and which, when in its first switching position, that is to say, when in its normal operating position, maintains the two lines open and, when in its second switching position, transposes the lines to connect the chargingpressure chamber to the atmospheric air under atmospheric pressure and to connect the atmospheric chamber to a line portion, permanently under charging pressure from the charging-pressure chamber during operation.

8. A safety device as claimed in any of claims 1 to 3, in which the electromagnetic control member comprises an actuating electromagnet adapted, upon the appearance of a fault signal and controlled by a change-over signal from the electronic control unit, to act upon a thrust rod connected to the movable wall in a direction to reduce the fuel delivery quantity established by the delivery quantity adjusting member.

9. A safety device as claimed in claim 8, in which the armature of the actuating electromagnet is articulated to a lever one end of which, when the actuating electromagnet is actuated, presses in the direction of the force of the return spring against an end of the thrust rod remote from the charging-pressure chamber.

1 0. A safety device for a fuel injection pump of an injection-type internal combustion engine equipped with a supercharger, constructed, arranged and adapted to operate substantially as herein described with reference to and as illustrated in the drawings.