GB2226893A - A distributor-type fuel injection pump having a mechanical speed governor - Google Patents

Description

DESCRIPTION Distributor-Type Fuel Injection Pump for Internal Combustion

Engines

This invention relates to distributor-type fuel injection pumps for internal combustion engines.

In some internal combustion engines such as, for example, directinjection engines having no precombustion chamber, the starting quantity must be limited in order to reduce emissions of smoke in the starting phase. To do this, it may be necessary for the termination of delivery on starting to be earlier than the termination of delivery for normal load operation. Problems are caused by the fact that, even if it is reduced, the starting quantity may have to be shut-off during the transition to the idling range. In a known distributor-type fuel injection pump of this type, an adjustable stop acts on the starting lever and, as the temperature increases, reduces the maximum excess starting quantity by a temperature- dependant member. In doing so, however, for example by making the starting spring bi-metal, a direct influence is exerted on the other governor functions, which is particularly disadvantageous if additional operating characteristics, such as, for example, the charging air pressure in super-charged engines, are to be superimposed on the governor -2characteristic and the devices provided therefor also have to be altered because of the adjustable stop arrangement.

The problematical nature of such interventions is known from another distributor-type fuel injection pump (DE-OS 28 44 911), in which the commencement of injection, the excess starting quantity and the idling speed can be controlled simultaneously by way of an adjusting device which is controllable in dependence upon engine temperature.

In another fuel injection pump of this type (P3721301.6), in order to set a starting quantity which can also be smaller than the full-load quantity, it has been proposed to adjust an adjusting lever stop of the starting lever by way of a drive unit in such a way that the control spool, which is also articulated through the starting lever, can no longer move into the normal excess starting quantity position. Since the adjusting lever stop is also the shut-off lever of the internal combustion engine and the drive unit would prevent adjustment into the shut-off position, the drive unit is put out of operation by the fuel in the intake chamber of this fuel injection pump and the pressure obtained during operation, so that the shut-off lever is once again freely pivotable. However, this device occupies a space which is k -3required for devices pertaining to other engine characteristics such as, for example, the changing charge-air pressure (see "Informationsblatt Bosch Verteilereinspritzpumpe VE... F..Lehrmittel VDT-U2/704 DE 197C), so that it would be necessary to completely redesign the governor for a device which would only be required occasionally. Since the fuel pressure in the pump intake chamber is also used for controlling injection timing, only very small pressures are available in the event of idling speed, which pressures hardly suffice to put the drive unit out of operation, wherein, however, in this speed range, it is necessary to carry out a load-pressuredependant intervention in the governor and the adjusting- lever stop would be in the way of this.

In accordance with the present invention there is provided a distributortype fuel injection pump for an internal combustion engine, having a pump piston which is driven by a cam drive in reciprocating and simultaneously rotating movement, an annular control sleeve which is axially displaceably disposed on the pump piston to control the quantity of fuel injected, a control lever system for load-and-speed dependant, displacement of the control sleeve, which system has a main lever which is subjected to the force of a governing-down spring whose pre-stress is adjustable 1 by means of an adjusting lever and a starting lever which is pivotable about the same axis as the main sleeve and which, together with the main lever, confines a starting spring and, following displacement by a speed sensor, forms a lever assembly with the main lever, and a shut-off lever which is pivotable from the outside of the pump housing by way of an adjusting lever on the starting lever in the direction of a smaller quantity of injected fuel, wherein the pivotal range of the shut-off lever is steplessly adjustable and the shut-off lever can be pivoted by an adjusting member from an alterable stop position of the starting lever, which determines the maximum excess starting fuel quantity, into a position in which it is out of engagement.

Such an injection pump has the advantage that the starting quantity can be reduced for certain engines without impeding the devices which are used to input other operating characteristics to the governor and without otherwise impairing the governor functions, and that, moreover, this intervention can be carried out simply by way of a unit assembly which acts on the shut-off lever of the distributor-type injection pump, which lever is a standard part.

In an advantageous embodiment of the invention, the adjusting member operating in dependance upon operating characteristics is a bellows box which is actuatable by control air which is under a particular operating pressure. The control air required for adjustment can usually be obtained at various points, for example in the brake region, exhaust region, or intake region of the engine.

According to another advantageous embodiment of the invention, a Bowden wire acts an adjustmenttransmission member between the adjusting member and the outer shut-off lever and can be used to adjust the basic adjustment to be effected relatively simply and can, if necessary, also be over-ridden.

According to yet another advantageous embodiment of the invention, a solenoid valve is disposed in the line for supplying control air to the bellows box. As a result, it is relatively simple to put the-device into operation in dependance upon any conditions, for example the position of the ignition key.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in which:- Fig.1 is a longitudinal sectional view through a distributor-type fuel injection pump constructed 1 -6in accordance with one embodiment of the present invention; Fig. 2 is a detail relating to the invention on an enlarged scale; Fig. 3 is a functional graph illustrating the invention; and Fig. 4 is a corresponding control device for compressed air.

In the distributor-type injection pump shown in Fig. 1, a pump piston 1, which also acts as a distributor, is set into reciprocating and simultaneously rotating motion by a drive shaft 2 by means of a cam drive 3. During each compression stroke of the pump piston 1, fuel is delivered from a pump working chamber 4 through a longitudinal distributor groove 5 to one of a plurality of pressure passages 6, which are disposed at uniform angular intervals around the pump piston 1, leading to a combustion chamber (not shown) of an internal combustion engine.

Fuel is supplied to the pump working chamber 4 through an intake passage 7 from a fuel filled intake chamber 9 disposed in a pump housing 8 of the injection pump. During the intake stroke of the pump piston 1, the intake passage 7 is opened up by longitudinal control grooves 11 provided in the pump -7piston 1. The number of longitudinal control grooves 11 corresponds to the number of pressure passages 6 and hence to the number of compression strokes executed per revolution of the pump piston 1. A solenoid valve 12 in the intake passage 7 is adapted to close off the intake passage 7 at the termination of injection, such that no fuel can pass from the intake chamber 9 into the pump working chamber 4 during the intake stroke of the pump piston 1.

The quantity to be injected, which is delivered per stroke into each of the pressure passages 6, is determined by the axial position of a control sleeve 13 disposed about the pump piston 1. This axial position is determined by a governor 14 and an arbitrarily actuatable adjusting lever 15, with evaluation of the engine characteristics of speed and load.

The intake chamber 9 is supplied with fuel by a feed pump 16, which is driven by the drive shaft 2. A pressure-control valve 17 controls the output pressure of feed pump 16 and hence the pressure in the intake chamber 9 such that the said pressure increases with increasing speed.

The governor 14 is driven by way of a toothed gear 18, which is connected to the drive shaft 2. The toothed gear 18 drives a speed sensor 19 with 1 1 -8flyweights 21, which acts on one end of a governor sleeve 22, which is axially displaceably mounted on a spindle 23 and, on its other end, acts on a control lever system 25, which is subjected to the force of a governor spring 24, which system adjusts the control sleeve 13 as to its stroke position. The control lever system 25 is pivotally mounted on a spindle 26. The pre-stress of the governor spring 24 can be altered by the adjusting lever 15 in such a way that, when the adjusting lever 15 is adjusted in the direction of increasing load, the pre-stress of the governor spring 24 increases so that the control sleeve 13 is displaced further upwards, which, due to the resulting later opening of a spill passage 27 of the pump working chamber 4 during the compression stroke of the pump piston 1, results in an increase in the quantity of fuel to be injected. The quantity of fuel still in the pump working chamber 4 is then always discharged if the mouths of the spill passage 27 emerge from the control sleeve 13 during the compression stroke of the pump piston 1, and thus further delivery of fuel by the pump piston 1 takes place into the intake chamber 9. in the control lever system 25, two governor levers are mounted on the spindle 26, namely a main lever 28. on which the governor spring 24 and an idling spring 31 act, and a starting lever 29. A starting spring 32 is provided between these two levers and presses them apart, and, when the engine is stationary, displaces the control sleeve 13 as far upwards as possible, which corresponds to a maximum fuel delivery quantity, a so- called excess starting quantity. As soon as the internal combustion engine is started, the governor sleeve 22 is displaced against the starting lever 29 by the flyweights 21 and pivots it against the force of the starting spring 32 into the position illustrated, in which the starting lever 29 and the main lever 28 are in abutment. The starting spring 32 is thus rendered inoperative. During the subsequent displacement in dependance upon speed and load, the control sleeve 13 no longer reaches its previously occupied extreme position for excess starting quantity.

During starting speeds, the idling spring 31 is not operative and does not become operative until idling speed is reached, before the governor spring 24 then becomes effective for the actual governing-down operation (speed regulation) above idling speed and once the two levers have moved into abutment. In the variable-speed governor, the governor spring 24 regulates the desired speed, whereas in an idling speed governor, it effects governing-down in a manner which is known for such mechanical governors.

After being pivoted accordingly, an inner shut-off lever 33, which is disposed on one front end of a torque shaft 34 mounted in the pump housing, acts on the starting lever 29, while a further adjusting lever 35 is disposed on its end lying outside the pump housing 8. As is known, the shut-off lever 33 can be pivoted by way of the starting lever 29 to displace the control sleeve 13 downwards to such an extent that the spill passage 27 is permanently open, so that no pressure can arise in the pump working chamber 4 for injection and the internal combustion engine is turned off.

Fig. 2 shows the range of operation of the starting lever 29 on an enlarged scale. According to the invention, the shut-off lever 33 can be turned steplessly by way of the adjusting lever 35 so that it acts as a stop for the starting lever 29 in the position shown by way of example, as a result of which the position of the control sleeve 13 relative to the pump piston 1 is limited upwardly by way of the spindle 26. As described above however, this uppermost position of the control sleeve 13 defines the maximum possible injection quantity in each case. This of course always applies when the governor sleeve 22, driven by way of the flyweights 21, has not yet engaged with the starting lever 29 for the starting range. When the shut-off lever 33 is pivoted fully upwards, the control sleeve 13 is displaced, asdescribed above, an extremely long way downwards, so that the mouth of the spill passage 27 no longer enters the control sleeve 13. The further the control sleeve 13 is displaced upwards, the greater the maximum possible injection quantity on starting, wherein, in accordance with the invention, this respective position can be determined by means of the shut-off lever 33. In the extreme case, which is shown by the dotted line, the shut-off lever 33 is pivoted downwards to such an extent that it no longer intervenes with respect to the starting lever 29. In accordance with the invention, the shut-off lever 33 is steplessly pivotable from a position for a very small starting quantity to said extreme position, which a starting quantity can be delivered which is greater than the full-load quantity, because'the starting lever 29 can be pivoted away from the main lever 28 by way of the starting spring 32, which results in an additional upward displacement of the control sleeve 13. In the position shown, the starting lever 29 is spaced only slightly from the main lever 28, by an amount a, with the result that the excess starting quantity is in this case only slightly greater than the normal full-load quantity.

-12In accordance with the invention, however, it should also be possible for the starting quantity to be smaller than the full-load quantity, that is, that the shut-off lever 33 can be pivoted even further upwards in such a case., so that the main lever 28 can be displaced slightly upwards by way of the starting lever 29 from the initial position determined by a stop 36, with corresponding downward displacement of the control sleeve 13. This applies to the starting 0 phase only. As soon as the engine has started, the shut-off lever 33 is pivoted downwards out of engagement.

The invention is further described with reference to the graph in Fig. 3 In this graph, the control sleeve travel s (ordinate) is plotted against the speed n (abscissa). The curves shown thus correspond to the respective quantity of fuel injected, wherein curve b corresponds to the starting quantity, curve c to the idling quantity, curve d to the full- load quantity and curve e to full-load speed regulation that is to a greater reduction in quantity with increasing speed. Speeds up to speed n, are referred to as starting speeds, that is speeds which are so low that the governor sleeve 22 has yet to press the starting lever 29 against the main lever 28. From there to speed n2 is the idling speed range, in which -13curve c runs, that is, a very limited speed range for maintaining a minimum speed, the idling speed. In the intermediatespeed range, that is between the idling speed n2 and the maximum speed n3, the speed is determined by way of the adjusting lever 15 in an idling maximum-speed governor, in that a quantity of fuel to be injected corresponding to the load and to the speed respectively is fed to the internal combustion engine. Of these curves, the full-load curve d is shown, that is the curve which corresponds, during normal operation, to the maximum quantity of fuel injected. As soon as the maximum speed n3 is reached, governing- down takes place, as shown by the curve e, so that, at speed n4, no more fuel is delivered.

It is intended that the invention should only be effective in the starting speed range, that is up to speed nj, and namely in the form of a varying starting quantity. The maximum possible starting quantity is determined by the control sleeve travel sl, that is, a travel which corresponds to the highest possible position of the control sleeve 13 in Fig. 2. In some engines, however, it is desirable for this starting quantity to be at s2, that is, a quantity which is smaller than the full- load quantity s3, as shown by curve d. It is intended that an infinite adjustment -14should take place between these two control sleeve positions sl and s2 in order to adapt to the requirements. For the position of the shut-off lever 33 shown in Fig. 2, the point s4 may, for example,be assumed for an injection quantity which is greater than the injection quantity at full load. As soon as the shut-off lever 33 is further up in the starting position, the point corresponding to the starting quantity moves correspondingly downwards. If, however, the shut-off lever 33 is moved into the position shown by the dotted line (Fig. 2), the point moves in the graph right up to the top to sl.

As shown in Fig. 4, this pivotal range of the shut-off lever may be limited by an upper stop 37, that is the location for the minimum admissible starting quantity. This stop can be adjusted accordingly by way of adjusting screws 38. The stop is a stop which is fixed to the housing, as used for otherwise conventional shut-off levers. The further adjusting lever 35 is acted upon on the one hand by a Bowden wire 39, against the force of a torsion spring 41 which acts on the adjusting lever 35 in the direction of increasing injection quantity, wherein said Bowden wire 39 is controlled on the other hand by a bellows box 42 which, when a corresponding vacuum is reached., adjusts the adjusting lever by way of the 1 1 -15Bowden wire 39 into the position shown by the dotted line. As a result, the shut-off lever 33 is also pivoted into the position shown by the dotted line in Fig. 2. The bellows box is actuated by the control air of a vacuum region of the internal combustion engine, which can be taken by way of a supply line 43 from the vacuum region of the internal combustion engine, for example the brake region. This air supply line 43 includes a 3-port, 2-position solenoid valve 44 so as to be able to deliberately control the change-over to be dependent upon any engine characteristics, in particular the rotational speed. A travel sensor may replace the speed, and other restoring means can be disposed on the adjusting lever in place of, for example, the torsion spring as well as in the bellows box 42 itself. It is thus of course conceivable for the adjustment of the stop 37 to be automatic. The decisive factor is that the starting quantity is substantially infinitely adjustable, even to below the full- load quantity. Rendering the influence of the shut-off lever 33 inoperative during normal operation does not otherwise impair the governor function, so that other engine characteristics can be input to influence regulation without any disadvantage, such as, for example, as shown in Fig. I in the form of a lever 45, which may -16displace the main lever 28 in a direction away from the stop 36 independently of the position of the governor sleeve 22, for example for additive fuel enrichment in a super charged engine in the full-load range, which may be effected by way of bellows box (not shown), which displaces a 3-dimensional cam 46 to achieve a particular characteristic.

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Claims (5)

-17CLAIMS

1. A distributor-type fuel injection pump for an internal combustion engine, having a pump piston which is driven by a cam drive in reciprocating and simultaneously rotating movement, an annular control sleeve which is axially displaceably disposed on the pump piston to control the quantity of fuel injected, a control lever system for loadand-speed dependant, displacement of the control sleeve, which system has a main lever which is subjected to the force of a governing-down spring whose pre-stress is adjustable by means of an adjusting lever and a starting lever which is pivotable about the same axis as the main sleeve and which, together with the main lever, confines a starting spring and, following displacement bya speed sensor, forms a lever assembly with the main lever, and a shut-off lever which is pivotable from the outside of the pump housing by way of an adjusting lever on the starting lever in the direction of a smaller quantity of injected fuel, wherein the pivotal range of the shut-off lever is steplessly adjustable and the shut-off lever can be pivoted by an adjusting member from an alterable stop position of the starting lever, which determines the maximum excess starting fuel quantity, into a position in which it is out of engagement.

4 k

2. A fuel injection pump as claimed in claim 1, wherein the adjusting member is a bellows box which is actuatable by control air which is under a particular operating pressure.

3. A fuel injection pump as claimed in claim 2, wherein a Bowden wire acts as the adjustmenttransmission member between the adjusting member and the adjusting lever or the stopping lever and, when the bellows box is actuated, the shut-off lever is adjustable against the force of a restoring spring in the direction of a reduced quantity of injected fuel.

4. A fuel injection pump as claimed in claim 2 or 3, wherein the control air is fed in a control line to the bellows box and a solenoid valve is disposed in the supply line.

5. A distributor-type fuel injection pump substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Published 1990at The Patent Office. State House. 66 71 I-ligl-.Ho2born. Londc)nWCIR4TP.F-urther copies maybe obtained frcn The Patent Officc Sales Branch, St Mary Cray. Orpington. Kent BR5 3RL Printed by Multiplex techniques It4. St Mary Cray. Kent. Ccn 1 87 1