JP2004045139A - Engine rotation meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine rotation meter for correctly detecting the rotation speed of an electronic injection type engine. <P>SOLUTION: The engine rotation meter is provided with a current sensor for measuring injector driving current and a rotation speed calculating unit for deriving engine rotation speed based on the injector driving current measured with the current sensor. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to an engine tachometer for detecting a rotation speed of an electronic injection engine, particularly an electronic injection diesel engine.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, engine speed measurement has been performed to analyze the behavior of an engine.
[0003]
Conventionally, a vibration sensor has been used to measure the rotational speed of a diesel engine, and the vibration sensor is attached to the engine cylinder head or injection pipe to detect the vibration of the engine cylinder head or injection pipe accompanying the rotation of the engine. The rotation speed of the engine is measured.
[0004]
[Problems to be solved by the invention]
However, in recent years, it has become difficult to detect vibrations due to the fact that the unitization of the engine has progressed and the number of parts that can be contacted from the outside has decreased, and the recent development of vibration reduction technology.
[0005]
In view of the above circumstances, an object of the present invention is to provide an engine tachometer capable of accurately detecting the rotation speed of an electronic injection engine.
[0006]
[Means for Solving the Problems]
An engine tachometer of the present invention that achieves the above object includes a current sensor that measures an injector drive current, and a rotation speed calculation unit that calculates an engine rotation speed based on the injector drive current measured by the current sensor. It is characterized by.
[0007]
The control unit that controls the injection timing of the fuel from the injector is located away from the engine unit even in the case of a unitized engine, and the injector drive current that controls the injection of the injector is transmitted from the control unit to the engine. It is transmitted by cable to the injectors of the unit.
[0008]
The present invention has been made by paying attention to this point, and it is possible to measure the rotation speed of the engine even with a unitized engine.
[0009]
Here, in the engine tachometer of the present invention, it is preferable that the current sensor measures the injector drive current by detecting a magnetic force generated by the injector drive current.
[0010]
By employing a current sensor that detects magnetic force, the injector drive current can be measured without any processing of the cable that transmits the injector drive current.
[0011]
Further, in the engine tachometer of the present invention, the rotation speed calculator detects a current pulse obtained by a current sensor, and obtains an engine rotation speed by measuring a period of the detected current pulse, It is preferable that the next current pulse is detected after a predetermined time or more has elapsed from the timing of detecting one current pulse.
[0012]
This makes it possible to accurately detect the rotational speed of a so-called multi-stage injection type engine that continuously injects fuel a plurality of times in one ignition cycle.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0014]
FIG. 1 is a diagram showing an outline of an electronic injection type diesel engine and an engine tachometer as one embodiment of the present invention.
[0015]
An injector drive current 22a is sent from the computer control unit 21 to the injector 23 via the cable 22. Diesel fuel is fed into the injector 23 from a fuel tank 24 via a high-pressure pump 25. The fuel sent to the injector 23 is injected into the cylinder 26 by the injector drive current 22a from the computer control unit 21.
[0016]
The ignition of the fuel injected into the cylinder 26 pushes down the piston 27 downward in the drawing, and the driving force is transmitted to the crankshaft 29 via the connecting rod 28, and the crankshaft 29 rotates. The rotation of the crankshaft 29 is detected by a rotation position sensor 30 and transmitted to the computer control unit 21. The computer control unit 21 sends out an injector drive current so as to match a predetermined phase angle of the rotation of the engine.
[0017]
Note that, for simplicity, the rotation position sensor 30 is illustrated to directly detect the rotation of the crankshaft 29, but a signal synchronized with the rotation of the engine may be obtained. It need not be deployed at this location.
[0018]
The diesel engine shown in FIG. 1 is a four-cycle engine, in which fuel injection is performed once or continuously at a predetermined phase angle when a period during which the piston 27 moves up and down twice is one cycle.
[0019]
Here, an injector drive current 22 a flowing through the cable 22 is measured by the current sensor 11 constituting the engine tachometer 10 as one embodiment of the present invention, and transmitted to the rotation speed calculation unit 12.
[0020]
FIG. 2 is a schematic diagram of the current sensor.
[0021]
When the injector drive current 22a flows through the cable 22, a magnetic force is generated in a direction surrounding the cable 22. The current sensor 11 is arranged so as to surround the cable 22 and directly detects a magnetic force generated around the cable 22, and the injector driving current 22 a flowing through the cable 22 is measured by detecting the magnetic force.
[0022]
FIG. 3 is a diagram showing a signal processing method in the rotation speed calculator 12 shown in FIG.
[0023]
3 (A) is a diagram showing an injector drive current measured by the current sensor 11, for each predetermined multiple injection period T _c, a pulse-like injector driving current, more continuously over a multistage injection time T _p And multi-stage injection of fuel is performed. The diesel engine described here is a four-cycle engine, and the multi-stage injection cycle _Tc shown in FIG. 3A corresponds to the time of two rotations of the engine (two vertical movements of the piston 27 shown in FIG. 1). I do.
[0024]
FIG. 3B is a diagram illustrating a time (same injection time T _g ) when the same injection is considered.
[0025]
In the case of multi-stage injection as shown in FIG. 3A, an incorrect measurement result will be obtained if a plurality of continuous current pulses are detected as one current pulse each to determine the rotational speed of the engine. Therefore, here, the first current pulse as shown in introducing the same injection time T _g, in the same injection time The T _g be generated current pulses repeatedly FIG 3 (C) shown in FIG. 3 (B) Only the current pulse is detected.
[0026]
The rotation speed calculator 12 shown in FIG. 1 detects the current pulse as shown in FIG. 3C as described above, measures the time interval between adjacent current pulses, and doubles the reciprocal thereof. Gives the engine speed.
[0027]
Here, the same injection time The T _g, the minimum period T shorter than _cmin obtained from the maximum rotational speed of the engine, and may be longer than the maximum multi-stage injection time T _pmax. That is, the same injection time _Tg is
T _pmax <T _g <T _cmin (1)
Needs to be satisfied.
[0028]
Here, when the same injection time The T _g satisfies the maximum over speed above (1) from the lowest rotational speed of the engine is present, the same injection time The T _g, fixed predetermined, thereby satisfying the expression (1) May be set to a reasonable time. _If there is no fixed identical injection time Tg that satisfies the above expression (1) in a wide range from the lowest rotation speed to the highest rotation speed of the engine, the same injection time _Tg is obtained as follows, for example. You may.
[0029]
FIG. 4 is a diagram showing an example of a method of _obtaining the same injection time Tg shown in FIG.
[0030]
In a rotating device such as an engine, since the rotation speed does not discontinuously and abruptly change between adjacent cycles, the rotation periods T _c1 , T _c2 , and T _c3 one rotation before as shown in FIG. , ...
T _gn = T _{c (n−1)} × a (2)
Where a is a constant n = 1, 2, 3,.
, The same injection times T _g1 , T _g2 , T _g3 ,... As shown in FIG.
[0031]
However, in this case, when there is no injection signal input in FIG. 4A, that is, when the engine is stopped, T _g = ∞, so the upper limit calculated from the minimum rotation speed of the engine and the like is set. It is desirable.
[0032]
【The invention's effect】
As described above, according to the engine tachometer of the present invention, it is possible to accurately measure the engine rotation speed even for a unitized engine.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of an electronic injection type diesel engine and an engine tachometer as one embodiment of the present invention. FIG. 2 is a schematic diagram of a current sensor.
FIG. 3 is a diagram showing a signal processing method in a rotation speed calculation unit 12 shown in FIG.
FIG. 4 is a diagram showing an example of a method of _obtaining the same injection time Tg shown in FIG. 3 (B).
[Explanation of symbols]
Reference Signs List 10 engine tachometer 11 current sensor 12 rotation speed calculation unit 21 computer control unit 22 cable 22a injector drive current 23 injector 24 fuel tank 25 high pressure pump 26 cylinder 27 piston 28 connecting rod 29 crankshaft 30 rotation position sensor

Claims (3)

A current sensor for measuring the injector drive current,
An engine tachometer, comprising: a rotation speed calculator for calculating an engine rotation speed based on the injector drive current measured by the current sensor. The engine tachometer according to claim 1, wherein the current sensor measures the injector drive current by detecting a magnetic force generated by the injector drive current. The rotation speed calculation unit detects an electric current pulse obtained by the electric current sensor, and calculates an engine rotation speed by measuring a period of the detected electric current pulse. 3. The engine tachometer according to claim 1, wherein a next current pulse is detected after a lapse of at least a predetermined time.

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