DE3146185C2 - Method for setting a specific angular position of the crankshaft of an internal combustion engine and device for carrying out this method - Google Patents

Abstract

Device for setting a specific angular position of the crankshaft of an internal combustion engine with respect to one of the two piston dead centers of a cylinder, in which a signal transmitter is provided which senses a specific piston position, and in which a geared motor connected to an angle transmitter which can be coupled to the crankshaft, and an electronic measuring control device are provided, which the desired angle can be entered, with half of the angle described by the crankshaft being measured when the crankshaft rotates from overrunning the specific piston position until reaching the same position again, and the piston dead center in between is automatically determined from its position the crankshaft is rotated further by the desired angle and then stopped automatically. The bearing clearances can be eliminated by measuring both crankshaft positions corresponding to the specific piston position under the same conditions, i.e. under tension or pressure by the connecting rod. The device can be used in general for measuring crankshafts, setting injection pumps and ignition devices, and setting specific positions of shafts.

Description

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is rotated further between the desired angle (γ) and half the swept angle (oil). J5

2. The method according to claim 1, characterized in that the first angular position (Pi) upon rotation of the crankshaft (1) from the direction of the relative dead center (UT) is set beyond this first angular position in the opposite direction to the rotation to during the measurement.

3. Apparatus for performing the method according to claim 1 or 2, characterized in that a on the engine block a ·, fsetzbaren digital signal generator (6) is provided, which a signal at piston ^ positions below or above the specified piston position (K) outputs that a gear motor (7) connected to an angle encoder (8) is provided, which can be coupled to the crankshaft (1), and that an electronic measuring control ^J u device (9) is provided which the angle corresponding to the desired angular position (γ) can be entered and which this and the signals of the angle sensor (8) and the signal generator (6) to control signals for the geared motor (7) in the way that it processes the crankshaft (!) in response to a start signal Movement sets and stops at the desired angular position.

The invention relates to a method for setting a specific angular position of the crankshaft the internal combustion engine and a device for performing this method.

In internal combustion engines with pistons, it is important to determine the top dead center. Of this The points in time for ignition, injection, inlet and outlet valves are set from the reference point. the Assignment of the angular position of the crankshaft and the position of the reciprocating piston is similar to a cosine Function given. In the vicinity of the dead centers, a certain angular movement corresponds to Crankshaft only has very little piston movement. Therefore adjustment is due to piston movement only inappropriately possible.

The simplest, but not very precise, method determines the top dead center position of a piston by means of a so-called "dial gauge" or a dipstick placed on the engine block (DE-PS 25 13 482, Sp. 7, Z. 13-28).

In a known method (DE-AS 25 13 482) is therefore at least one further piston for OT determination is also used. However, this method can only be used for multi-cylinder machines and only enables the adjustment of the dead center of a piston, i.e. no other angular position. This Dead center occurs when two other specific pivot pins or pistons are at the same height be brought, either by a lifting device or by being placed on the engine block Linear transformers happens. Any inaccuracies the crankshaft, bearings and pistons are not taken into account and falsify the measurement result.

However, the crankshaft is not always set to the top dead center OT . Sometimes it is desirable or necessary to set the crankshaft to a certain angular position, e.g. B. for setting the ignition point or for the start of injection of the injection pump or more generally for engine assembly. After determining the TDC, this desired angular position can be set using the cosine-like function based on a length measurement between the reciprocating piston and the upper edge of the engine block. The disadvantage of this method is that you have to convert from a length measurement to an angular position. This results in an inaccuracy that is at least as great as in the method described at the beginning.

It is therefore the object of the invention to provide a method which is capable of any desired Adjust the angular position of the crankshaft much more precisely than before, and this also for single-cylinder internal combustion engines can be used with the same accuracy.

The object is achieved according to the invention by the method specified in the characterizing part of claim 1 solved.

The advantage of this method is that no previously established reference points are required, since the two positions Pi and P2 of the crankshaft are symmetrical to the axis going through the two dead centers and the reference point is automatically determined by measuring half the angle. No absolute length measurement needs to be carried out, but only the crankshaft angle ole to be determined incrementally. The resolution of the angle encoder ultimately determines the accuracy of the position of the crankshaft to be set.

The accuracy can be further increased by taking the connecting rod bearing play into account can. This is achieved by expanding the method according to claim 2.

A device for carrying out the method according to the invention is specified in claim 3.

Details of the invention can be found in the description and drawing of an exemplary embodiment.

In the drawing shows

Fig. 1 is a schematic sketch to explain the Procedure and and

2 shows a schematic representation of a device to carry out this procedure.

Fig. 1 shows schematically a cross section through a cylinder of an internal combustion engine with the Turning circle of the connecting rod bearing axis of the crankshaft 1, the

Connecting rod 2 and a piston 3. The piston 3 is in position K, which corresponds to the crankshaft positions P 1 and P2. TDC and BDC as well as a specific crankshaft position P3 correspond. The position P3 is a desired camshaft position to be set of z. B. 20 ° before TDC, with a clockwise crankshaft (indicated by the solid arrow). Also indicated is a digital signal generator 6, described in more detail later in FIG. 3, which changes its signal exactly at a certain piston pitch, in the example piston position K , ie emits an O signal above position K and a 1 signal below or vice versa. The position K and the crankshaft position P 1 assigned to it can vary in wide G -.- enzen, in the example about Pi between 40 ° and 140 ° after TDC.

If the crankshaft is now slowly rotated, for example from an initial position around TDC, then from the beginning of the signal change at point Pi until the further signal change at point P 2, when the piston 3 reaches the same piston position K again, the angle P \ -M-R2 = tx measured in such a way that it is only half counted, i.e. a / 2. Since Pi and P2 are symmetrical with respect to the axis, which goes through OT and UT, this means that rotated back from point P 2 by - / 2, exactly the bottom dead center f / T is reached. And this in turn means that this point can be fixed without having previously fixed any fixed point. If you now relate the desired crankshaft pitch P3 (= 07-20) to the UT, this means: P3 = UT + γ, where y = 160 °, (180-20 °) and also γ = * / 2 + β, dg : β = γ-α / 2 is So you have to turn the crankshaft from ji point P2 by the angle β in order to reach exactly the desired position of the crankshaft.

This means that any desired crankshaft position can be set, with positions that are closer to TDC than BDC to BDC as the reference point for the calculation, as in the example just described, in the other case to TDC.

F i g. 2 shows a schematic representation of a four-cylinder internal combustion engine BKM with a crankshaft 1, the connecting rods 2 and the piston 3, but without a cylinder head. A digital displacement sensor 6, which is mounted on your frame 5, is placed as a signal transmitter with this frame on the plane surface of the engine block as a reference plane so that its sensor touches the piston surface - in this case the first cylinder. It has the properties already described in connection with FIG. 1. The crankshaft 1 is coupled via a coupling 4 to an electric geared motor 7, the other end of the drive shaft of which is connected to an incremental angle encoder 8. The output signals 5 and <$ of the signal generator 6 and the angle sensor 87 are input to a measuring control device 9, which also the angle! γ can be stored by hand.

This measurement control circuit 9 is an electronic to Device, preferably equipped with a microprocessor, which converts the input data into control signals processed for the gear motor 7.

In preparation for the setting process, the piston 3 of the first cylinder of the internal combustion engine BKM is brought close to top dead center, the signal generator 6 is then placed and the geared motor 7, which is arranged in a stable manner, is coupled to the crankshaft 1. The desired angle γ is saved.

With a start signal, the geared motor 7 begins to rotate the crankshaft. When the crankshaft 1 reaches the position Pi , the signal generator gives a 1-signal until the position P2 is reached. During this time, the pulses of the incremental angle sensor are counted in a counter, i.e. the angle α is measured, but only for each pulse half the angle value is saved as long as the signal generator gives a 1-signal. When the point P 2 is reached , the signal jumps to a 0-signal. At this moment the angle a / 2 is saved. The signal voltage serves as the trigger signal for calculating the angle β and for starting a new angle measurement. The calculated angle β is stored and compared in a comparator with the angle now measured with the full value. If the two values match, the measuring control circuit 9 issues the command to stop the geared motor 7. The crankshaft then stoii exactly in the desired position.

The setting of the crankshaft can be refined by eliminating the bearing clearances between the piston and the crankshaft (connecting rod bearings, piston pin bearings). This is possible if the signal from the signal generator 6 is only evaluated when the bearings at points Pi and ί'2 are only subjected to tension or compression. This means, for example, that after the start before point P 1, the signal from the signal generator 6 is not evaluated for measurement when it is turned to the right. First, the crankshaft is driven counterclockwise from an initial position between UT and Pi. Here the bearings are subjected to pressure. When Pi is reached, the angle <x is set to zero. The crankshaft is then driven clockwise and the angle λ / 2 measured from the point at which the stored starting position is passed. The bearings now have tensile load up to BDC and then pressure load, also when reaching point P2. The start and end of measurement are therefore under pressure, which eliminates the bearing clearances. The rest of the process takes place as already described.

The device can also be used for measurements on several cylinders. It can be determined whether there is an angle error between the dead centers of the individual pistons. For a multi-cylinder measurement, it is best to use a signal transmitter for each piston. This ensures that the respective measuring points Pi and P2 of the individual pistons are recorded by one revolution of the crankshaft.

Di? Device can be used for precise adjustment of Injection pumps are used in engine production. The Crankshaft set to a certain angle. So there is an exact assignment between the angular position the crankshaft and the angular position of the injection pump.

In the future, a pulse generator will increasingly be required to control the motors. This driving force must emit its signal at a defined crankshaft angle graduation. Should this pulse generator be exact are set, so i ° t precondition that the crankshaft is previously set exactly.

In gasoline engines, a basic setting of the ignition point is based on the crankshaft position possible. Because the procedure for multiple cylinders

can be applied, it is possible even after Set the ignition timing, pulse generator, injection pump, etc. to a mean value. The future framework with regard to exhaust gas and consumption require greater accuracy with regard to the ignition point depending on speed. Burden etc. To this too electronic components are increasingly being used. The effectiveness of electronic building blocks depends crucially on it. how exactly the sensors used are set. With the above device, combined with the use of electronic components, the basic setting of the Ignition timing an optimum can be achieved. So it is conceivable that with the device described OT's of all pistons are determined, d. h “The angular errors of the crankshaft are also known. These Angular errors in the crankshaft can be entered in the electronics and thus corrected.

The device can also be used to test crankshafts or other shafts. Instead of connecting rods, pistons and cylinders, a device can then be used, which the Lifting movement detected. The advantage here is that the relationship between stroke movement and Angular movement does not have to be known and that the length tolerances of the piston, connecting rod and cylinder do not become noticeable as an angular error.

A measured crankshaft could be classified in terms of its angle errors. This classified crankshaft can then be adjusted in the manner described during installation in the engine, for example after the first piston. But since the crankshaft has been classified, it is known how much the other pistons deviate from their nominal value. The setting can now be refined if the setting after the 1st piston is corrected by the amount of the deviation from the mean value. An engine set in this way then no longer has the TDC of a piston as a reference point, but the mean value of all OI's.

If the crankshaft is not measured before installation, but the TDCs of all pistons determined individually, an average value can then also be used for setting.

For this purpose 2 sheets of drawings

Claims (1)

Patent claims: 1. A method for setting a desired angular position of the crankshaft with respect to one of the two piston dead points of a cylinder of an internal combustion engine, characterized in that from a fixed piston position (K) corresponding first angular position (Pi) between the one leg (P3) one desired angle (γ) and the related dead center (UT), ι ο as the other leg of the desired angle (γ) , the crankshaft beyond the related dead center (BDC) up to an angular position (P 2) is rotated, the swept angle (oil) is measured and the crankshaft (1) from the second angular position (P 2) by a difference