EP0742357A2 - Injection regulating device for injection nozzles and method of adjustment - Google Patents

Abstract

The setting device consists of an injection setting mechanism, a setting drive (20) and a control unit. The setting drive consists of a translational element (19), an electrical setting member (21) and a position sensor. The setting member has an electric motor (40) which pushes the translational element along a thread (44,45) on which it is self-locking. The position sensor (55) produces a pulse when a shoulder (53) connected to the translational element passes it. There is also a pulse sensor (58) producing counting pulses. The sensors and the motor are connected to the control unit. From the pulses produced, this produces the actual position of the mechanism, compares this with a required position, and from this, produces control signals for the motor.

Description

The invention relates to an injection adjustment device for injection pump nozzles, consisting of an injection adjustment mechanism, an adjustment drive acting thereon and a control unit for the adjustment drive, the adjustment drive consisting of a translatory element, an electrical actuator and a position sensor.

There are different ways to adjust the start of injection, with pump nozzles are known: rotatable eccentric rocker arm shaft or displaceable control rod for each individual or for all pump nozzles. All such mechanisms use a translatory element driven by an electrical actuator.

A generic adjustment device is known from DE-A 29 03 875. This uses an eccentrically mounted rocker arm shaft, which is actuated by an electrical actuator via a power amplifier and a lever. A position sensor, which emits a signal corresponding to the lever position, also acts on this. First of all, the direct attack of the power amplifier on the lever is problematic, since the position of the rocker arm forces changes its position can adjust during the injection stroke. Because of the short travel of the lever, neither the setting nor the position signal can be exact, the device is therefore not suitable for the precise spray adjustment required for reasons of emission minimization.

A particularly large problem that is not addressed at all in this prior art is the adjustment of the spray adjustment device when the unit is being assembled and when it is installed in the internal combustion engine. Adjustments may also be necessary over the course of the service life due to wear.

According to the state of the art, when assembling the internal combustion engine, the camshaft and rocker arm axis must first be positioned precisely with respect to fixed reference surfaces on the cylinder head by means of gauges and staked out in a specific angular position. Only then can the assigned nominal pre-stroke (this is the stroke at which the injection begins if it is not set to early or late) of the pump nozzle. This requires further manipulation with calibres or the like because the rocker arm axis must be brought into the position corresponding to the nominal forward stroke. After adjusting the adjusting screw between the pump element and the rocker arm, the position sensor must also be calibrated. To do this, it is placed in two defined positions and the two measured values are stored in the control unit. These manipulations are very time-consuming and cause high costs in series production and when exchanging them later.

In addition, the accuracy of the sensors and the accuracy of the assignment are slowly lost due to wear. A later re-calibration or replacement of the pump nozzle is only possible with a similar amount of work.

The invention is therefore based on the object of designing a spray adjustment device in such a way that it is easy to install and adjust with high accuracy, and to provide a method by which this adjustment can be achieved with the greatest accuracy and with the shortest possible time throughout its entire service life.

For this purpose, the device according to the invention has the features specified in the characterizing part of claim 1. Because the electrical actuator is a motor that moves the translatory element via a gear, the adjustment is very accurate. The friction occurring in the transmission counteracts an adjustment of the mechanism during the pressure peaks of the injection stroke. Because of this and because of the special control, it can also be found with a normal electric motor, an expensive stepper motor is no longer necessary.

The pulse sensor, which responds to the rotation of the motor, supplies a large number of high-resolution counting pulses for a short stroke due to the gearbox, so that the very fine adjustment of the translatory element required to minimize emissions can be achieved. Play in the transmission and any other games on the way to the injection-adjusting mechanism could adversely affect the accuracy of the setting, which is why, in the case of known constructions, one tries to arrange the position sensor at the end of the action chain and thus the play chain, i.e. on the adjustment mechanism itself. Due to the short path on this, however, only imprecise signals of low resolution are obtained. However, by using a barrier sensor and thanks to the adjustment method according to the invention, the games cannot affect the accuracy of the adjustment. also the barrier sensor responds precisely when it passes the shoulder, which gives it a very precise impulse that is suitable as a calibration impulse.

The control unit can then clearly determine the actual position from the counting pulses and the calibration pulse and, from this and from the target position, generate a steep signal for the electric motor, which is unaffected by games and dead times, because the counting pulses also come directly from him. Finally, because the control unit always has the calibration pulse available, the count is automatically verified each time the barrier sensor is passed, so that counting errors or faults in the electric motor are corrected.

This also results in a considerable simplification of the assembly, because the assignment between the nominal advance stroke and the adjustment mechanism no longer requires the precise assembly of the camshaft and the rocker arm axis, but occurs automatically.

In a further development of the invention, the barrier sensor is a HALL sensor which is inserted in the housing of the adjustment drive with exact dimensions (claim 2). By using a HALL sensor, an undiminished accurate and strong calibration impulse is delivered even at a minimal passing speed of the shoulder. Due to the dimensionally accurate installation in the housing according to the nominal stroke, all tolerances influencing the spray adjustment are combined on a single easy-to-machine component - the housing - which further simplifies and reduces the cost of manufacture and assembly.

In a particularly simple and inexpensive embodiment, the HALL sensor is a fork barrier and the shoulder is formed by a sheet metal plate which is immersed in the fork (claim 3).

In a preferred embodiment of the invention, the electric motor interacts with the translatory element via a pinion and a friction brake is provided for the latter (claim 4). This only requires a very simple gear. Because of the good guidance of the translational element required for other reasons, the toothing can be selected to be very fine and sufficient reduction can thus be achieved. The friction brake provides a certain resistance to the displacement of the translatory element due to the peak forces during the injection.

In another embodiment of the invention, the motor drives a spindle nut via a worm gear, which nut cooperates with a threaded spindle of the translational element (claim 5). In this way, a high reduction ratio can be achieved in the simplest way, which allows the choice of a high-speed and therefore very small electric motor. The relatively larger play of a worm gear is not significant thanks to the calibration method according to the invention. The self-locking that occurs with a worm gear and with a threaded spindle is a particularly strong effect of the friction that occurs, which may be desirable to absorb the peak load during the injection stroke.

In a preferred embodiment for a pump nozzle driven by a camshaft via rocker arms, the injection-adjusting mechanism is an eccentric rocker arm axis which is rotated by the translational element via an eccentric lever (claim 6). Although the invention is suitable for all types of pump nozzles, the advantages of a pump nozzle having such an adjustment mechanism are particularly evident since they also help to assemble the valve train its complicated kinematics, which would otherwise have to be taken into account, was decisively simplified.

The invention also relates to a method for adjusting a spray adjustment device according to one of the preceding claims, which permits simple and precise adjustment of the injection pump after it has been installed in an internal combustion engine and also later. It consists in that the translatory element is driven by the motor of the adjustment drive until the shoulder has reached the barrier sensor and the motor is switched off when the barrier is passed and then the count of the pulse counter in the control unit is set to zero in this position (claim 7 ). This automatically, quickly and simultaneously achieves two things: The control unit knows which counting pulse corresponds to the nominal advance stroke and the injection adjustment mechanism is in the position corresponding to the nominal advance stroke.

In a particularly advantageous development of the method, the barrier sensor for adjustment is only ever passed in a defined direction (claim 8). As a result, all games in the adjustment mechanism are switched off and the adjustment is invariably accurate, even if the games increase over the course of their service life.

In order to automatically ensure that this passage always takes place in the same direction regardless of the current position, the status of the barrier sensor is used to decide in which direction the translational element is to be moved first in order to pass the barrier sensor in the specified direction, in which case the barrier sensor has already been passed, the shoulder is first moved past it in the opposite direction and only then is it passed through in the specified direction (claim 9).

In order to drive automation even further, it can be provided that the control unit triggers the adjustment automatically when the quantity-determining element has assumed the position for adjusting the quantity allocation (claim 10). If a pump unit is replaced or reinstalled after repair, the assignment between a certain control rod position and the position of a quantity-determining element of the pump must be set, for which purpose the control rod is usually unplugged. The control unit recognizes from this position that it is a readjustment and thereby automatically starts the adjustment of the spray adjustment.

Finally, the method can also compensate for signs of wear and other adjustments during the entire life cycle in that the control unit automatically triggers a readjustment at defined intervals (claim 11). The easiest way to define these distances is by the number of starts, every or every hundredth.

Fig.1:

einen Querschnitt durch die Kopfregion eines Dieselmotors,

Fig.2:

vergrößert das Detail A der Fig.1 als erfindungsgemäßer Teil der Verstelleinrichtung in einer Stellung,

Fig.3:

Ansicht B zu Fig.2,

Fig.4:

wie Fig.2, jedoch in einer anderen Stellung,

Fig.5:

Wie Fig.4, jedoch einer anderen Ausführungsform,

Fig.6:

Schnitt nach VI-VI in Fig.5,

Fig.7:

Schaltschema der erfindungsgemäßen Einrichtung,

Fig.8:

Ablaufdiagramm zum erfindungsgemäßen Verfahren.

The invention is described and explained below with the aid of figures. They represent:

Fig.1:

a cross section through the head region of a diesel engine,

Fig. 2:

1 enlarges detail A of FIG. 1 as part of the adjusting device according to the invention in one position,

Fig. 3:

View B to Fig. 2,

Fig. 4:

like Fig. 2, but in a different position,

Fig. 5:

As in FIG. 4, but with a different embodiment,

Fig. 6:

Section according to VI-VI in Fig. 5,

Fig. 7:

Circuit diagram of the device according to the invention,

Fig. 8:

Flow chart for the method according to the invention.

Of a diesel engine, only the uppermost part of the cylinder head 1 can be seen in FIG. 1, onto which a camshaft housing 2 is screwed and closed with a valve cover 3. Inside is a camshaft 4, which drives a pump nozzle 5 in addition to the valves (not shown). For this purpose, a rocker arm 6 is provided, which acts on the piston foot 8 of the pump nozzle 5 via an adjusting screw 7. The pump nozzle also has a quantity-determining element 9, here a control rod. The rocker arm 6 is mounted on a rocker arm axis 10, the geometric axis 11 of which is eccentric to the bearing means 12 in the camshaft housing 2. For each pump nozzle, a clamp 13 is screwed onto the rocker arm axis 10 by means of a bolt 14, the eccentric lever 15 of which acts via a first pin 16 on a push rod 17, which is again connected to a translatory element 19 via a second pin 18. This is part of the adjustment drive 20.

Fig. 2 and 3 shows the adjustment drive in more detail. A lug 30 is formed on the camshaft housing 2 and is provided with a bore 38 in which the translatory element 19 is guided. A base plate 31 is fastened to the projection 30 and positioned relative to it by means of a centering 32. A housing 33, in which the adjustment drive 20 is accommodated, rests on the base plate 31. It has three bores 34 through which it is screwed together with the base plate 31 onto the attachment 30. It is provided on one side with a motor flange 35 and at its end remote from the camshaft housing 2 with a cover flange 36 on which a cover 37 is fastened (removed in FIG. 3).

An electric motor 40 is screwed onto the motor flange 35; its controlled power supply is not shown. Its shaft protrudes into the housing 33 and carries there is a worm 41 which meshes with a worm wheel 42. This is supported by means of the bearings 43 in the base plate 31 and in the housing 33, its hub is a spindle nut 44. The internal thread of this cooperates with a threaded spindle 45 which is fixedly connected to the translatory element 19 or is part of it. The threaded spindle 45 is limited by a stop collar 46 which limits the stroke of the spindle nut 44 in an end position. The threaded spindle 45 continues at its end facing away from the camshaft housing in a threaded extension 47, onto which a sleeve 48 is clamped by means of a nut 49.

The sleeve 48 carries a sensor plate 51, on which a friction brake 50 acts in order to prevent damage to the plate 51 during assembly. A guide rod 52 can also be provided for the same purpose. The sensor plate 51 is folded (FIG. 2) at its end and forms a shoulder 53 which interacts with a position sensor 55. In the present exemplary embodiment, it is a HALL sensor that is fastened in the housing 33 with precise dimensions and forms a very precise response barrier, which is indicated by the dashed line 56. A sensor line 57 leads away from the sensor. Furthermore, a pulse sensor 58 is provided, which is connected via line 59. This pulse sensor 58 interacts with the shaft of the electric motor 40. The motor 40 is a very simple, controllable, high-speed electric motor, which is why it is sufficient to attach a single brand to the shaft for the pulse generation. In this FIG. 2, the adjustment drive 20 is in an extreme position, corresponding to the latest possible start of injection.

4 shows the same adjustment drive 20 in its other extreme position, corresponding to the largest possible pre-injection. It can be observed that the Shoulder 53 of sensor plate 51 is very far away from barrier 56 in this position, whereas in FIG. 2 shoulder 53 has passed barrier 56 and the bent part of sensor plate 51 also interrupts the barrier.

The variant shown in FIGS. 5 and 6 differs from the previous one in that, instead of worm and screw spindle, the motor - with or without an intermediate reduction gear - drives a pinion 80 which engages in a toothing 81 of the translatory element 19, which is damped in its movement by a brake shoe 82 serving as a friction brake. The force exerted by plate springs 83 on the element 19 is preferably adjustable by means of a screw 84. Means can also be provided which cause the friction shoe to lift when the electric motor is actuated.

7 shows a circuit diagram of the spray adjustment device according to the invention. The adjustment drive 20 is drawn as a box that contains the electric motor 40. The control device is designated 65, it contains an adjustment control 66 and a setpoint determination 67. The adjustment control 66 is supplied with a position signal from the position sensor 55 via line 57 and with counting pulses generated by the pulse sensor via line 59. The setpoint calculator 67 determines from various input signals 68, e.g. Speed, accelerator pedal position, engine temperature, a setpoint for the start of injection. This is also fed to the adjustment control unit 66 via a line 69. From this, the motor is operated in a controlled manner via lines 70.

The adjustment method will now be described with reference to FIG. 8: when the internal combustion engine is being assembled, the camshaft 4, the pump nozzle 5, and the Rocker arm axis 10 with the rocker arms 6, the clamp 13 with the eccentric lever 15, the push rod 17 with the entire adjustment drive 20, see FIG. 1. With this assembly, no special adjustment procedures or gauges need to be used, since, thanks to the method according to the invention, these adjustments are made automatically afterwards. The quantity assignment, which is not part of the invention, is then carried out in a known or any other way. In any case, the control rod 9 (Fig.1) must be unplugged, that is, fixed in a certain position relative to the camshaft housing 2.

The engine assembly is symbolized in FIG. 8 by box 80, the control rod is unplugged by box 81. If the control unit is now switched on (box 82), which means turning an ignition key when the engine is installed in the vehicle, the control unit recognizes that yes cooperates with the control device for the quantity control, which is not the subject of the invention, that the control rod is unplugged and triggers the adjustment process.

When the control unit is switched on, the sensors are also activated. Since the spray adjustment device was somehow installed, it must first be determined in which position it is. For this purpose, it is first queried whether the position sensor 55 is in the "EARLY" position, see diamond 83. This is the case when the shoulder 53 of the sheet 51 does not dip into the barrier. If it is immersed, the adjustment device is therefore "LATE", the electric motor is started in the direction of "EARLY" (box 85) and in the meantime it is continuously queried whether the "EARLY" position has already been reached, diamond 86 and loop 87 As soon as the shoulder 53 has left the barrier, the nominal advance stroke (this is the basic position in which the start of spraying is neither "EARLY" nor "LATE"), so the electric motor turned a few more turns (e.g. 10) and then stopped. If it has already been established in diamond 83 that the "EARLY" position is present, then one is already in the position now reached, which is indicated by arrow 84.

Now the electric motor is switched on in the "LATE" direction (box 89) until the shoulder 53 reaches the barrier again. For this purpose, the position sensor is repeatedly questioned, diamond 90 loop 91. When the position of the nominal advance stroke (in the always constant direction) has been reached, the electric motor is stopped and the pulse counter in the control unit, which counts the signals from the pulse sensor 58, is set to zero (Box 92). The position of the adjusting device is now uniquely assigned to the nominal advance stroke (dashed box 93). Then the piston foot 8 is brought up to the adjusting screw 7 by means of the adjusting screw 7 and possibly a gauge and the adjustment is finished.

A similar procedure is carried out for re-verification during the operating life, but only boxes 82 to 92 are run through.

Claims (11)

Injection adjustment device for injection pump nozzles, comprising an injection adjustment mechanism (10, 13, 17), an adjustment drive (20) acting thereon and a control unit (65) for the adjustment drive, the adjustment drive consisting of a translatory element (19), an electrical actuator ( 21) and a position sensor, characterized in that a) the electric actuator (21) has an electric motor (40) which displaces the translatory element (19) via a gear (41, 42, 44, 45; 80, 81), b) the position sensor (55) is a barrier sensor which emits a calibration pulse when passing through a shoulder (53) connected to the translational element (19), c) a pulse sensor (58) which responds to the rotation of the motor and which emits counting pulses is also provided, d) the barrier sensor (55), the pulse sensor (58) and the electric motor (40) are connected to the control unit (65), which uses the calibration pulses and the counting pulses to determine the actual position of the injection-adjusting mechanism (10, 13, 17) determined, compares this with a target position and generates control signals for the electric motor (40). Spray adjustment device according to claim 1, characterized in that the barrier sensor (55) is a HALL sensor and is installed in the housing (33) of the adjustment drive with exact dimensions. Spray adjustment device according to claim 2, characterized in that the barrier sensor (55) is a fork barrier and the shoulder (53) is formed by a sheet metal plate (51) which is immersed in the barrier sensor (55). Spray adjustment device according to claim 1, characterized in that the electric motor (40) interacts with the translatory element (19) via a pinion (81) for which a friction brake (82) is provided. Spray adjustment device according to Claim 1, characterized in that the electric motor (40) drives a spindle nut (44) via a worm (41) which interacts with a threaded spindle (45) of the translatory element (19). Spray adjustment device according to claim 1 for a pump nozzle (5) driven by a camshaft (4) via rocker arm (6), characterized in that the spray-adjusting mechanism is an eccentric rocker arm axis (10) which is separated from the translatory element (19) via an eccentric lever (15 ) is twisted. Method for adjusting a spray adjustment device according to one of the preceding claims after installation of the pump nozzles (5) in an internal combustion engine, characterized in that the translatory element (19) driven by the electric motor (40) of the adjustment drive (20) is moved and stopped when the shoulder (53) passes through the barrier sensor (55) and the count of the pulse counter in the control unit (65) is set to zero in this position. Method according to claim 7, characterized in that the shoulder (53) only ever passes the barrier sensor (55) for adjustment in a defined direction. A method according to claim 7, characterized in that it is decided from the status of the barrier sensor (55) in which direction the translational element (19) is to be moved first in order to pass the barrier sensor in the specified direction, in the case of the barrier sensor has already been passed, the shoulder moves past it in the opposite direction and only then is it driven through in the specified direction. Method according to one of claims 7 to 9, characterized in that the adjustment is triggered automatically by the control device when the quantity-determining element (9) is blocked in the position assumed for setting the quantity assignment. Method according to one of claims 7 to 9, characterized in that the control device (65) automatically triggers a readjustment even after the initial adjustment during assembly at defined intervals.

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