EP0166931B1 - Speed governor for fuel injection pumps - Google Patents

Description

State of the art

The invention relates to a fuel injection pump according to the preamble of the main claim. A known speed controller of this type (used in the Bosch distributor injection pump type VE) has only one leaf spring as an intermediate spring in one version, which has the function of a so-called starting spring that generates a starting quantity, and in another version a combination of this starting spring with a coil spring, which regulates the idle speed. While the starting spring is as soft as possible and only has the task of pushing the second lever and thus the injection quantity control element into a position for additional starting quantity which is above the maximum full load injection quantity in the starting position, the idling spring has the task in the idling position of the controller the second lever and thus keeping the injection quantity control member in a position corresponding to the balance of the forces (spring, speed signal generator) as counterforce to the speed signal generator which develops only small forces at idling speeds.

Only when the idle speed is exceeded is the idle spring pushed together, so that in the upper idle speed range the two levers are frictionally engaged. However, the idle spring is pushed together at idle speeds and sufficient load via the first lever as far as a stop determining the initial position of the first lever allows this.

Of course, a single helical spring or leaf spring serving as a starting and idling spring can also serve as an intermediate spring, in which it is assigned a first area which serves to generate a starting additional quantity and then a somewhat harder area serving to regulate the idling speed.

In the case of a diesel engine, the actual consumption per engine cylinder is known to differ in contrast to the injection quantity metered by the injection pump per engine cylinder, which is the same for all engine cylinders when the speed controller is in a certain position. The spread of the amount that can be consumed by the engine cylinder can be 30% of the average injection amount when idling and is therefore particularly disadvantageous there. If, for example, the average idling quantity is 5 mm ³ , the scatter may well be 2 mm ³ . From a dynamic point of view, these differences have a correspondingly very short-term influence on the speed of the engine and, via the speed signal generator of the speed controller, in turn on the injection quantity, the change of which, depending on the engine cylinder for which it is effective, may result in an undesired amplification or deceleration of the average idle speed to be regulated . For this reason, the degree of non-uniformity (P-degree) should be as large as possible, which would require a stiffest possible idling spring. In order to cover a certain distance (control path) against a stiff spring, a relatively large change in force is required in contrast to a soft spring. The scattering of the braking and shocks that occur during combustion in the engine result in corresponding power surges from the speed signal transmitter to the second lever, which can be absorbed by a stiff spring in such a way that jerking or engine shaking during idling is prevented.

However, as stated above, a rigid idle spring has a high P-degree, which can be 40% when idle. At idle speeds of 600 rpm. this is already 240 rpm. This high P degree leads to an unstable running of the motors, the so-called sawing. This sawing can in turn be counteracted by a soft spring with a correspondingly low P-degree, namely a spring in which large distances (control paths) are covered even with relatively small changes in force of the speed signal transmitter. Due to the low P-grade of soft springs, adding or subtracting the small quantity changes caused by the scattering is largely absorbed as an influence on the speed, so that a low P-grade is achieved (low sawing, largely constant speed) but jerky or shaking the motor can take place. In the known speed controllers, a relatively high P-grade is therefore taken in order to avoid the unpleasant jerking, especially in the case of passenger car diesel engines.

In known speed controllers of the type mentioned, an attempt is therefore made to achieve a compromise between the lowest possible engine shaking and low sawing of the engine by the choice of the stiffness of the idle spring, without therefore having to increase the idle speed.

This problem does not only exist with the idling spring as an intermediate spring, but also applies equally to regulators of injection pumps for stationary engines or other runs to be controlled, in which the speed must be kept constant. Here too, sawing, that is to say deviation from the constant speed, must be avoided on the one hand, and motor jerking on the other hand, which could possibly lead to damage to the driven unit.

From GB-A-2 090 430 a fuel injection pump is known, in which an arbitrarily operated adjusting lever is provided which changes the regulating spring tension and which is used for Input of the speed or torque request via a drag link consisting of two mutually opposite springs, with which the fuel quantity adjusting element of the fuel injection pump is coupled. As a result, the volume adjustment element can be operated via a control lever, on which a speed-dependent force counter to the force of the control spring set by the adjustment lever and, if applicable, the adjustment spring used in series, as well as the idle spring which is fixed in parallel to the control spring, regardless of the position of the adjustment lever in the Regulating case can be adjusted. The adjustment of the fuel quantity adjusting member caused by the adjusting lever via the drag member in the event of non-regulation is delayed by an attenuator connected between the latter and the regulator lever. An intermediate lever can be provided between the control spring and the adjustment spring.

This device is very complex and, since the idle spring abuts stationary on the one hand and the towing element lies in series with a pre-tensioned control spring and the damping element is provided parallel to both, there is no possibility of selecting the spring stiffness in different operating situations in the sense of the relationships discussed above.

From GB-A-1 231 010 it is known, however, to provide two counter-rotating springs in a speed sensor of a fuel injection pump, which clamp a piston connected to the actuator of the speed sensor. The piston separates working areas from one another, which can be connected to one another via a throttle and on the other hand via pressure relief valves. This device dampens the adjustment movement of the speed sensor in such a way that when the speed changes slowly, a damped adjustment takes place and when the speed changes quickly, an undamped adjustment takes place when the pressure relief valves are open.

Advantages of the invention

The speed controller for fuel injection pumps according to the invention with the characterizing features of the main claim has the advantage that a controller with resilient feedback is created, in which the short shocks caused by the scattering of the engine cylinder combustion are absorbed by a stiff spring, which the desired high P- Degree corresponds and that a delayed action of a soft spring for a constant speed as possible a lower P-degree can be achieved. This creates a very flat control characteristic curve in the volume speed diagram, which changes into a correspondingly steep load absorption characteristic, for example when starting from idle to higher load conditions. The same applies to the characteristic curve for stationary drives.

According to an advantageous embodiment of the invention, the driving member works with two mutually counteracting damping springs, between which the point of attack of the second lever is clamped in a floating manner. Both damping springs are designed to be relatively stiff, at least stiffer than the intermediate spring. The advantage of this configuration is the simple arrangement of obtaining an adjustable actuating force for each of the two pivoting directions of the second lever, since the damping element naturally has a different effect depending on the actuating direction. While the enclosed quantity has to be pressed through a throttle in one direction, only a negative pressure can be effective in the other direction.

drawing

• Fig. 1 eine Kraftstoffeinspritzanlage mit dem erfindungsgemäßen Drehzahlregler;
• Fig. 2 das Reglerhebelpaket aus Fig. 1 in vergrößertem Maßstab im Längsschnitt gemäß, der Linie 11-11 in Fig. 3;
• Fig. 3 eine Ansicht des Pakets aus Fig. 2 gemäß dem Pfeil 111 in Fig. 2 und
• Fig. 4 ein Diagramm des Einspritzmengenverlaufs über der Drehzahl.

An embodiment of the object of the invention is shown in the drawing and explained in more detail in the following description. Show it:

• 1 shows a fuel injection system with the speed controller according to the invention;
• FIG. 2 shows the regulator lever assembly from FIG. 1 on an enlarged scale in longitudinal section according to line 11-11 in FIG. 3;
• Fig. 3 is a view of the package of Fig. 2 according to arrow 111 in Fig. 2 and
• Fig. 4 is a diagram of the injection quantity curve over the speed.

Description of the embodiment

In a fuel injection system according to FIG. 1, fuel is fed from a fuel tank 10 via a prefeed pump 11 and a fuel filter 12 to a distributor injection pump 13. The pump housing of this pump is broken open so far that the elements of the speed controller are visible.

The load input, which takes place arbitrarily in the motor vehicle, for example, is carried out via an adjusting lever 14, the pivoting movement of which is transmitted via an adjusting shaft 15 guided in the pump housing to a driving lever 16, on which a control spring 17 engages on the one hand, which on the other hand is connected to a regulator lever arrangement 18. Contrary to the force of this control spring 17, an adjusting sleeve 19 of a speed signal transmitter also acts on the control lever arrangement 18, which is articulated by flyweights 20 which are driven at a motor-synchronous speed. The force acting on the control lever arrangement 18 from the sleeve 19 thus changes the speed according to a quadratic function. The regulator lever arrangement 18 displaces a control slide 21 determining the injection quantity on a pump and distributor piston 22. The fuel is fed from the injection pump via a distributor groove 23 to injection nozzles 24, the pump piston 22 executing as many pressure and suction strokes per revolution as injection nozzles 24 or engine cylinders are available. For a certain position of the control slide 21, all engine cylinders receive the same injection quantity. As soon as the speed increases, the controller reduces the injection quantity per engine cylinder with the same load specification as soon as the speed drops.

Since the internal combustion engine can burn different amounts of these injected quantities per cylinder with the same injection quantities in each case, this causes a different torque curve on the engine crankshaft and thus, seen dynamically, a different torque curve on the crankshaft per engine cylinder. This causes corresponding changes in the speed of the speed signal generator, so that the force with which the regulator sleeve 19 acts on the regulator lever arrangement 18 changes briefly and continuously. This results in a corresponding, ongoing, minimal change in the injection quantity, which can lead to jerking or shaking of the engine, since the change in quantity cannot be assigned to the corresponding cylinder. This may result in an addition of the amount of cylinders that are already getting too much and a reduction in the amount of cylinders that are already getting too little. This increases the jerking and shaking.

2 and 3, a regulator lever arrangement 18 is shown with which this bucking can be largely avoided. This regulator lever arrangement 18 has an adjusting lever 28 which is pivotally mounted in the housing at 29 and carries an axis 30. Swiveling around point 29 causes the axis 30 to be correspondingly displaced. This adjusting lever 28 is set to adjust the position of the axis 30 and has no influence on the speed control.

The control spring 17 shown in FIG. 2 only by an arrow indicating the direction of force acts on a tensioning lever 31 which is pivotably mounted on the axis 30. Also on the axis 30, a start lever 32 is pivotally mounted, on which a head 33 is provided for articulating the control slide 21 and on which the speed signal transmitter 19 engages in the direction of force represented by the arrow.

An intermediate spring assembly 35 is arranged between the tensioning lever 31 (1st lever) and the starting lever 32 (2nd lever), by means of which the relative pivot position of the two levers relative to one another as a function of the forces 17 and 19 and thereby the fuel injection quantity are determined in a certain speed range becomes.

This intermediate spring assembly 35 consists of three springs of a first softer spring 36 and two harder stiffer springs 37. The intermediate spring 36 is arranged in a cylinder 38 which is closed on one side and is supported on the one hand on the closing end wall and on the other hand on a piston 39 which is axially displaceable in the cylinder 38 . The interior of the cylinder 36 is connected to the outside by a throttle bore 40 provided in the end wall. A pin 41 is provided on the piston 39, on which the two stiffer intermediate springs 37 are guided, one of which is supported on the piston 39 and the other on a locking ring 42 which is arranged on the pin 41. Between the springs 37, the end 43 of the start lever 32 is provided in a floating manner by the springs 37.

In the case of short, hard bursts of force from the speed signal transmitter, one of the stiff springs 37 absorbs these forces, the stiff spring causing a high P-degree. For these short impacts, the driving element consisting of cylinder 38, piston 39 with pin 41 acts like a rigid system, or spring 36 acts as an infinitely stiff spring, since the volume enclosed in the cylinder acts inelastic due to the throttling action of throttle 40 and only with a throttle cross section according to the time available, the spring 36 can come into effect. As a result, the entire spring assembly 35 acts like a flexible return. The spring 37 acts in the short-term behavior, the spring 36 acts in the long-term behavior. This results in a high P-degree due to the stiff springs 37 for the short pressure changes and a low P-degree due to the then in the event of a relatively long-term change in the force 19 (or 17) acting softer spring 36. The same applies to rapid load changes, for which a change in the injection quantity is effected relatively quickly, until the required injection quantity is then delayed (short-term excess quantity in the event of a sudden increase in load).

4, the injection quantity Q is plotted on the ordinate and the rotational speed n on the abscissa in an injection quantity / speed diagram. The characteristic curve indicates the full load, with b being the starting additional quantity. c is the regulation process when the maximum speed is reached. This diagram also shows the transition from idle volume to larger quantities when the load is taken up. It is significant that the controller has a very flat idling characteristic d, since the actual idling spring 36 is relatively soft and causes a low P-degree. This avoids sawing the engine, ie the engine runs at a largely constant idling speed. As soon as a load change is made, the relatively stiff retaining springs 37 cause a rapid increase in the injection quantity with a slight change in speed, in accordance with the characteristic curves e.

Although, according to the example, the problem with idling speed control, namely motor jerking and sawing, can be solved in this way, the invention can accordingly be transferred to speed controllers for pumps of stationary motors or to corresponding problems in intermediate speed ranges. It is important that the speed controller according to the invention cause short-term changes in the force of parameters such as load or speed to cause a high P-degree, whereas longer-term parameter changes cause a low P-degree of the controller.

Claims (4)

1. Speed governor for fuel injection pumps of internal combustion engines, having a first lever (31) which is pivotable about a spindle (30) and on which a control spring (17), which can be changed in force in particular as a function of load, acts against a restoring force which, produced by a speed signal transmitter (19), can be transmitted to the first lever (31) via a second lever (32) articulating the injection-quantity control element and pivotable about a spindle (30), and having at least two intermediate springs (36, 37) arranged between the levers, characterized in that two intermediate springs (36, 37) connected in series are provided: a first weaker spring (36) and a second more rigid spring (37), of which the first spring (36), between a piston (39), enclosing an inner space in a cylinder (38), and the cylinder (38), is arranged inside the inner space which can be connected to the outside via a throttle opening (40), and the first spring (36), during changes in force of short duration in the speed signal transmitter (19), acts in a considerably more rigid manner than the second spring (37).

2. Speed governor according to Claim 1, characterized in that the second intermediate spring (37) acts on the piston (39, 41 ) outside the inner space and couples the latter to a lever (32).

3. Speed governor according to Claim 1 or 2, characterized in that two springs acting against one another serve as the second intermediate spring (37), between which the application point (43) of the second lever (32) is clamped in a floating manner.

4. Speed governor according to Claim 3, characterized in that a blind bore, partly accommodating the first spring (36) is provided in the piston (39).

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