KR0121319B1 - Method and device for sensing the direction of crankshaft rotation in a diesel engine - Google Patents

Abstract

A method and apparatus for detecting the direction of the crankshaft of a diesel engine is used to measure the differential angle α between the fuel injection start FB and the reference mark BM according to the crankshaft rotation. Since the normal trailing flank of the cam of the fuel injection pump becomes the leading flank in the reverse rotation, this differential angle becomes less or larger than the reference result of the reverse rotation. The signal generated by the reverse rotation can be used to immediately stop the engine.

Description

[Name of invention]

Fuel injectors for diesel engines

[Brief Description of Drawings]

1 is a block circuit diagram of a device for detecting a crankshaft rotational direction of a diesel engine according to the present invention.

2 is a side view showing one embodiment of a cam in a fuel injection pump of an engine.

FIG. 3 is a cam lift and pulse diagram for a fuel injection pump for a six cylinder diesel engine with reference to FIG. 2. FIG.

4 shows cam lift and pulse diagrams for an eight-cylinder engine.

5 is a side view of another embodiment of a cam.

6 is a pulse diagram of the cam of FIG.

FIG. 6A is a diagram in which the pulse diagram of FIG. 6 is modified.

Detailed description of the invention

[Technology Background]

The present invention relates to a method and apparatus for detecting a crankshaft rotational direction of a diesel engine which senses the rotational direction of the crankshaft of the diesel engine during starting and stops the engine immediately when the crankshaft rotates in the reverse direction. During start-up of the internal combustion engine, there is a possibility to rotate in the reverse direction after recoil. In addition to the risk of continued rotation in the reverse direction, there is also the potential for mechanical damage to the engine. It is an object of the present invention to detect rotation in the reverse direction by monitoring fuel injection initiation about the top dead center (TDC) of one cylinder of the engine.

DE-A-2653046 describes a method of controlling the injection timing (moment of injection start to top dead center) in which an actual ignition timing is determined and compared with a desired injection timing. The actual injection timing is determined by measuring the crank angle relationship between the reference mark generated by the pulse generator disk on the crankshaft and the injection initiation detected by the sensor near the injection nozzle.

Advantages of the Invention

The present invention provides, according to claims 1 and 2, respectively, a method and apparatus for sensing the crankshaft rotational direction of a diesel engine during startup. This has the advantage that a signal indicating the reverse direction can be used to immediately stop the engine, ie the signal is fed to the engine's governor so that the governor keeps the injection pump in zero feed.

It is desirable to detect the start of the injection stroke in the injection pump because the actual fuel injection cannot easily detect the injection valve at very low engine speeds below the starting speed, ie below 400 r.p.m. In any case, the minute time delay between the start of the injection stroke and the actual start of injection, which is not sharply limited at very low engine speeds, does not make much sense. Since the start of the injection stroke is directly related to the angular position of the cap shaft of the injection pump, the start of the injection stroke can be determined by measuring each remaining position of the camshaft.

[drawing]

The invention is explained in more detail by way of example with reference to the accompanying drawings.

Description of Example

The pulse generator 10 fits into the crankshaft of the diesel engine to generate one or more reference pulses BM at the correct time for crankshaft rotation. These reference pulses can be used to perform the operation of the electronic governor and the electronic ignition timing control operation as described in DE-A-2653046 or DE-A-3202614. According to the present invention, the reference pulse BM is used as a reference on which a signal indicative of fuel injection start is measured. The initiation of the injection signal can be either an actual injection initiation (SB) or an actual fuel transfer initiation (FBA) by the injection pump, but the injection stroke initiation (FB) is preferred, which is in response to the reciprocating motion of the pump piston 11. It may be a signal obtained from). The slight differences between SB, FBA and FB and the running time due to the compressibility of the fuel are not so important, especially at very low engine speeds.

The reference mark BM and the injection start signal FB are respectively applied to the start and stop inputs of the counter 12 supplied with the counted pulse train n representing the rotation of the crankshaft, which is an engine speed indication. The speed signal n is obtained from another pulse generator on the crankshaft and may be a pulse train suitable for generating one pulse rotation over an angle as described in DE-A-2653046. The speed signal n can also be derived from a reference mark BM, for example using a frequency multiplier.

The output coefficient of the counter 12 represents the actual injection angle α and is used in the comparator 14 to check whether the angle exceeds the value of the inlet α r provided by the reference value reservoir 16.

2 shows the cam 18 symmetrical to the camshaft. The point on the cam corresponding to the start of the pumping stroke is indicated by FB when the cam rotates in the normal direction shown by arrow 20. The corresponding point at which the pumping stroke is initiated by rotation in the reverse direction is shown as FB '. In FIG. 2 the working angle of the cam 18 is 60 degrees. That is, each range between the pump stroke start and the suction stroke complete is 60 degrees and this applies regardless of the direction of rotation. This angle corresponds to the 120 degree crank angle of the four-stroke engine.

The lower part of FIG. 2 shows the reduction of the reference pulse BM in the case of a six-cylinder four-stroke engine, and the upper part shows the crankshaft angle and the rise of the cam relative to the reference pulse BM. The cylinder TDC of a given engine is a crank angle of 20 degrees after the corresponding reference mark BM.

The engine is fitted to a conventional facility for the adjustment of the actual injection start moment at the injection valve to the TDC of each cylinder, ie the progress of the injection. However, FIG. 3 shows the crankshaft angle associated with the signal SB. As the engine is started, the injection progress is zero (20 degrees after BM) as shown by the dashed line 24, but the injection is 10 before the TDC at idling speed as shown by the solid line 26. It proceeds in degrees (10 degrees after BM) and further as the speed increases as shown by the dashed line 28.

If the reference mark BM is generated 20 degrees prior to the TDC of the incorporated engine cylinder, the counter 12 starts to count the engine speed dependent pulse n. When the transducer 11 is incorporated into the cam 18 and associated with the cylinder of the engine, each injection pump position starts its upstroke and soon detects that the counter 12 stops counting. Normally, the coefficient α stored in the counter 12 during engine startup may coincide below 20 degrees as shown on the left side of FIG. However, when the crankshaft of the engine starts to rotate in the reverse direction, the coefficient α of the counter 12 coincides below 40 degrees as shown on the right side of FIG. A reference angle αr between 20 and 40 degrees is applied to the reference input of the comparator 40 by the reservoir 16 to fix the inlet to the response of the comparator. Thus, upon rotation of the crankshaft in the reverse direction, the comparator 14 reacts to deliver an engine stop signal that can set the injection pump to zero fuel delivery. A retaining circuit (not shown) is provided to prevent restart of fuel injection until after the engine has been completely stopped.

FIG. 4 is similar to FIG. 3 except for an eight-cylinder four-stroke diesel engine. When the maximum possible value α during start-up in the forward direction is 20 degrees again, the ampule is easily detected by rotating the crankshaft in the reverse direction to its maximum possible value of 40 degrees, as the value αr is not critical. There is a distinction.

5 shows the cam 22 whose operating area between FB and FB 'corresponding to a crankshaft angle of about 72 degrees is only 36 degrees. 6 shows that the maximum rotation α in the forward direction is 20 degrees or less and the minimum rotation α in the reverse direction is 28 degrees or more. Therefore, the selection area of the? Value between 20 degrees and 28 degrees is narrowed.

In order to avoid the task requiring this accuracy, the reference mark BM can be increased from 20 degrees to 40 degrees before the TDC as shown in FIG. 6A. The value a may then be at least 30 degrees to increase the idling speed for rotation in the forward direction 20 and 18 degrees in the reverse direction. Thus, the reference value αr is less than the threshold, but the counter 12 must be arranged to count down rather than count up, and the controlled gates prevent the counter output from reaching the comparator until the counter is stopped. Should be provided between.

Another possibility that in the case of an in-line injection pump, the difference a between the rotation in the forward and reverse directions will be widened is to deform the trailing flank of the cam. This is possible because the shape of the trajectory side does not affect the injection operation.

The injection pump, to which the device of the present invention is fitted, is fed from a separation sensor arranged adjacent to the injection nozzle which senses the actual injection initiation (SB control) as described in DE-A-320261. Injection timing controlled by the injection angle governor may be provided.

Since the method and apparatus of the present invention are no longer needed once the engine has been started once in the forward direction, the signal to stop the engine may be blocked when the startup process is complete. Thus, in the case of a malfunction of the detector 11, the normal operation of the device is prevented from being disturbed, or in the case of a malfunction of the SB or FB control at the time of injection, the operation of the device under the control of the spare system is prevented.

The detector 11 is used for the FB control and also for the detector and the method of the present invention for detecting the actual initiation of injection in the case of the SP control.

Claims (6)

Characterized in that the difference between the signal indicating the start of injection and the reference mark incorporated at a specific angular position of the engine's crankshaft is measured and compared with the reference value, where the direction of rotation is indicated if the actual value is not greater or less than the reference value. How to detect the direction of rotation of the crankshaft of the engine. A pulse generator 10 for generating a reference mark BM for the crankshaft rotation of the engine, a detector 11 for generating a signal FB, FBA or SB indicating fuel injection start, a reference mark and fuel injection start An element 12 for generating a signal α representing each difference therebetween, and a comparator 14 for generating an output signal when the differential signal α is not greater or less than the reference signal αr. Crankshaft rotation direction detection device of a diesel engine. 3. A crankshaft rotational direction sensing device according to claim 2, characterized in that the element (12) generating the differential signal (α) is a counter (12) supplied with a count pulse (n) representing an engine speed. 4. A crankshaft rotational direction sensing device according to claim 2 or 3, characterized in that the detector (11) responds to the start of pumping stroke (FB) of the incorporated injection pump piston. 4. The trailing flank of the cam 18 of the injection pump is modified to increase the difference between the value of signal α for the forward and reverse directions of the crankshaft. Characteristic crankshaft rotation direction detection device of the diesel engine. 4. A crankshaft rotational direction sensing device for a diesel engine according to claim 2 or 3, which is used to generate an engine stop signal when the engine starts rotating in the reverse direction.