JPH0115803B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrical system that can be used, for example, in an internal combustion engine to generate an electrical signal representative of the rotational angular position of a crankshaft of the engine, thereby controlling the spark ignition of the engine. This invention relates to displacement transducers.

Traditionally, spark ignition in internal combustion engines is controlled by a mechanical interrupter point operated by a rotating cam driven from the engine's crankshaft. The timing of spark ignition is controlled by moving the angular position of the interrupter point relative to the axis of rotation of the cam depending on the level of partial vacuum in the engine's intake manifold.

Recently, electronic ignition systems for internal combustion engines have been developed. These electronics allow the timing of spark ignition to be controlled not only depending on the vacuum level as described above, but also on multiple other operating parameters of the engine, so that the engine becomes more efficient. Make it work. Additionally, while these electronic ignition systems do not require traditional interrupters or cam mechanisms, they do require some type of electronic ignition system to provide the system with an electrical signal representing the rotational angular position of the engine so that the timing of spark ignition can be controlled. Requires means. Furthermore, if the benefits of engine operating efficiency made possible by electronic ignition systems are to be maximized, the rotational angular position of the engine crankshaft is not possible with conventional cam and interrupter mechanisms. It needs to be monitored much more accurately than it is.

One prior proposal for monitoring engine rotation is to mount the engine flywheel with a series of precisely spaced permanent magnets arranged around it. The magnets fit into holes drilled in the flywheel. In that case, a pick-up coil is mounted on the engine in close proximity to the flywheel such that as the flywheel rotates, each magnet induces an electrical pulse in the coil as it passes. Ru. Each pulse thus represents the occurrence of a particular angular position of the engine. However, with such a configuration, it is difficult to obtain the sharp pulses required by electronic ignition systems to accurately represent when each magnet meets the coil. This is because relatively long rises and falls of the induced pulse occur when the magnet approaches and passes through the coil, so it is difficult to determine the peak of the pulse and hence the point of coincidence between the coil and the magnet. This is because it becomes difficult. To alleviate, if not overcome, such problems, the coils should be mounted as close as possible to the flywheel, typically with a spacing of less than 0.254 centimeters (0.1 inch), for example. However, as a practical matter, it is difficult to realize this without increasing the price of the engine. It will also be appreciated that the precision required in forming the holes in the flywheel for mounting the magnets also adds significantly to the cost of the engine. Such prior proposals include the accumulation of dirt on the pickup coil during use, which causes the peak amplitude of the induced pulse to decrease over time, which is why a threshold circuit is used to improve the waveform of the induced pulse. The problem is that it is difficult to use. If a threshold circuit is used with a fixed threshold, the decrease in pulse amplitude that occurs over time for the pulses induced by the magnet will In order to adapt, the amplitude of the threshold must be relatively low; a low threshold will give inaccurate results.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a simple and inexpensive displacement transducer which can be applied, for example, to generate electrical signals representative of the angular position of an internal combustion engine.

It is an object of the invention to provide a displacement transducer in which the assembly tolerances of the parts are substantially reduced compared to the prior art proposals mentioned above.

Another object of the present invention is to provide a displacement transducer that produces an output representative of the rotational angular position of the engine that can be easily installed in the engine.

Yet another object of the present invention is to provide a displacement transducer in which dirt accumulation is slow and such accumulation does not adversely affect accuracy.

According to a preferred embodiment of the invention, it comprises spaced apart transmitting and receiving means for transmitting and receiving energy, respectively, and a member moved between the transmitting and receiving means; An electrical displacement transducer is provided, the member of which is adapted to be moved between said transmitting means and receiving means. The receiving means generates an electrical output signal that assumes a first magnitude during repeated interruptions generated by the movable member and assumes a second, different magnitude during periods between those interruptions. It is made to be. Its output signal is connected to its first and second
and a comparator compares the magnitude of the output signal with the magnitude of the control signal to determine the magnitude of the interruption caused by the movable member. Gives signals to indicate the beginning and end.

The transducer according to the invention provides that the signal generated by the comparator is subject to interruptions caused by the movable member, even if dirt accumulates in the transmitting means or in the receiving means, thereby causing a change in the signal amplitude. has the advantage of giving an accurate indication of the beginning and end of. This advantage is obtained in that the output signal from the receiving means is compared in a comparator with a control signal representing the average value of said first and second magnitudes. Any change in signal amplitude caused by dirt accumulation will cause the first and second amplitudes of the output signal to change, and thus the value of the control signal. The control signal thus effectively defines a variable threshold that automatically changes to account for dirt accumulation or other factors that cause the magnitude of the output signal from the receiving means to change.

Preferably, the transmitting means and the receiving means comprise spaced apart coils for creating an inductive coupling between them, and the movable member comprises a rotating disk having a zigzag circumference, said coils being arranged in a circular motion of said rotating disk. The zigzag portion of it is arranged to interrupt the inductive coupling between the coils when rotated. In this preferred configuration, the rotating disk can be mounted for rotation with the crankshaft of the internal combustion engine. the edges of said zigzag portion define predetermined positions prior to top dead center for each piston of the engine, and in use, the signals generated by the comparators give an indication of those positions; The indication can be used in an electronic ignition timing system as a reference value for use in calculating the proper timing for the ignition spark.

The disk is an inexpensive component that can be formed, for example, by stamping out an aluminum plate, and can be easily integrated into the engine or bolted to a component that rotates with the engine, such as a cooling fan. It will be appreciated that such a preferred form of transducer according to the present invention can be constructed inexpensively and yet provide an accurate indication of the angular rotation of the engine. Furthermore, a relatively wide spacing, typically on the order of 5 mm, can be maintained between the transmitting means and the receiving means without changing the accuracy of the transducer.

Embodiments of the present invention will be described below with reference to the drawings.

Referring first to FIG. 1, a six cylinder motor vehicle internal combustion engine 1 is shown equipped with an electrical displacement transducer according to the present invention. The transducer comprises a member to be rotated by the engine, which member consists of a metal disc 2 mounted on the crankshaft of the engine and having a zigzag-shaped circumference. Mounted on the engine casing is an electrical sensing mechanism 3 which generates an electrical signal representative of the rotational angular position of the disc 2. This mechanism 3 is driven by electrical signals from a control circuit, indicated schematically by the numeral 4, and the output signal of this mechanism 3 is supplied to a circuit 4.

Circuit 4 provides signals on line 5 that accurately represent the rotational angular position of disk 2, and these signals are fed to calculation circuit 6 which calculates the appropriate timing of the ignition spark for the engine. These signals are used as reference values during the engine operation, where the timing is calculated in response to sensed operating parameters of the engine. Such calculation circuits are known, an example of which is described in British Patent No. 1481683.

The output of the calculation circuit is applied to a spark generation and distribution mechanism 7, but since the mechanism 7 itself is well known, a detailed explanation thereof will be omitted. Mechanism 7 supplies a high voltage electrical spark to a conventional spark plug 8 installed in engine 1 .

The transducer disk 2 and sensing mechanism 3 are shown in more detail in FIG. The disk 2 has three zigzag sections 9 which define six radially projecting edges 10, each of which has a predetermined position in the angular rotation cycle of the engine. The purpose of this is to define the location of the In more detail,
The edges are such that, as they pass through the sensing mechanism, the relevant edges define a predetermined angle prior to top dead center for the six pistons of the engine. The sensing mechanism 3 is adapted to detect the passage of the edge 10 and consists of transmitting means and receiving means arranged on both sides of the disc 2. The transmitting means includes a pole piece 1 on a line extending in the radial direction of the disk.
In this embodiment, the receiving means consists of a coil 11 wound around a U-shaped ferrite core 12 on which wires 2a and 12b are arranged. It has a coil 13 attached to it.

As will be explained in more detail below, coil 11 is energized by an oscillating electrical signal to induce an electrical output signal in coil 13. When disk 2 rotates,
The zigzag portion 9 repeatedly interrupts the passage of the magnetic flux from the coil 11 to the coil 13, thus causing the disc 2
As the coil 13 rotates, the output signal induced in the coil 13 changes between two peak amplitudes. Those 2
The first of the two peak amplitudes is relatively small and occurs during the period when the zigzag portion 9 interrupts the inductive coupling between the coils 11, 13; the second of the two peak amplitudes is are relatively large and occur during the period between the zigzag portions. It will thus be understood that the transition between said two peak amplitudes in the signal induced in the coil 13 is representative of the passage of the edge 10 of the disk 2 through the sensing mechanism 3. The control circuit 4 is adapted to detect these transitions between the two peak signal amplitudes.

The control circuit 4 will now be described in detail with reference to FIG. This circuit is driven by a system clock (not shown) which provides clock pulses at terminal 15. These clock pulses typically have a frequency of 100 KHz or more and are supplied to a drive circuit 16 which generates a square or sinusoidal waveform at that frequency, which waveform is used to energize the coil 11. The waveform of the signal applied to coil 11 is shown in Figure 4a. The waveform of the signal induced in the coil 13 as the disk 2 is rotated is shown in FIG. The first signal shown in Figure 4a is
repeating amplitude modulation to the peak signal amplitude of and a second signal higher than said first during the period between the interruptions caused by the zigzag portion 9.
It can be seen that the signal is amplitude modulated to the peak signal amplitude of . It will also be appreciated that during the transition between two peak signal levels, there is a finite rise or fall time as a result of the time it takes for edge 10 to pass through coils 11,13.

The modulated signal induced in the center-tapped coil 13 is transmitted to the full-wave demodulator 19 on line 1.
7 and 18 to remove the carrier frequency of the clock waveform and thereby derive a signal representative of the amplitude modulation caused by the rotation of disk 2.

The demodulator includes two CMOS transmission gates 20, 21 connected to lines 17, 18, respectively;
It consists of one inverter 22. The gate electrodes of the MOS transistors of gates 20 and 21 are driven by the clock waveform or its inverse to recover the amplitude modulation envelope generated by disk 2. The output of the demodulator 19 is connected to a resistor R1 adapted to wave the harmonics generated by the demodulator.
and a filter consisting of capacitor C1.

The wavered output signal of the demodulator 19 is shown in FIG. 4c, and the waveformed output signal has a magnitude of V ₁ each time one of the edges 10 of the disk passes between the coils 11, 13. and a second signal level of magnitude _V2 , and that signal has finite rise and fall times as edge 10 passes between the coils. It will be seen that we have t _r , t _s .

To accurately detect the timing of transitions in the waveform shown in Figure 4c, the waveformed output of demodulator 19 is applied to one input of differential amplifier 24, which operates as a square comparator. The other input of amplifier 24 receives the DC level Va produced from the output of the demodulator by means of a filter circuit consisting of resistor R2 and capacitor _C2 . This DC level Va is preferably set to be the average of the magnitudes of the signal levels V ₁ and V ₂ and is preferably related to each other as follows.

Va=1/2(V ₁ +V ₂ ) Thus, differential amplifier 24 produces an output on line 23 only when the signal level shown in FIG. 4c is greater than or equal to Va, and As a result, a rectangular waveform as shown in FIG. 4d is produced on line 23. The leading and trailing edges of the rectangular waveform accurately represent the passage of the edge 10 of the disc 2 between the coils 11,13. This is because the magnitude of the modulated output of demodulator 19 becomes equal to Va after half the rise and fall times t _r , t _s . If the differential amplifier 24 and the averaging filter circuit are configured as described above, the waveformed output from the demodulator 19 becomes V ₁
and the leading and trailing edges of the waveform shown in FIG. 4d, constantly compared with the average value of V ₂ and whose average value is equally influenced by long-term drifts in V ₁ and/or V ₂ always occurs in the middle of the transition between V ₁ and V ₂ , so the leading and trailing edges of the pulse with the waveform shown in Figure 4d are caused by long-term drifts in V ₁ and/or V ₂ . The real benefit is that there are no negative effects.

It will also be seen that variations in the frequency of the clock waveform applied to terminal 15 do not substantially affect the accuracy of the output on line 23.

Additionally, the design of filter circuits C ₂ , R ₂ can be such that the transducer operates accurately over the normal range of engine speeds associated with internal combustion engines.

The circuit 4 also has the advantage that it can be simply formed by CMOS integrated circuit technology and can be integrated into the circuit components of the calculation circuit 6.

Referring to FIG. 5, main parts of another embodiment of the present invention are shown, in which the comparator is switched when the signal of FIG. 4c passes through the average value Va. but in this case it is a separate control signal obtained from the output of the demodulator 19.
It is not done using Va. The circuit in Figure 5 is
The comparator consists of a pair of CMOS inverters 24a and 24b in the same thermal environment, and a demodulator 19 at one end.
and the other end is connected to the output of one inverter 2.
Connected directly to the input side of 4a and resistor R ₃
and a capacitor _C3 connected to the input side of the other inverter 24b via the inverter 24b. To understand this circuit, it is best to first consider that the input to inverter 24a is at ground potential. In this case, capacitor C ₃ receives the waveform of FIG. 4c (switching between V ₁ and V ₂ ) on the left side as seen in the drawing, and so that its waveform and shape are the same but at V ₁ and V ₂ . A waveform is provided on the right side of the drawing in which the voltage level has been shifted so that the portion of the waveform shown is arranged symmetrically with respect to ground potential. Since the level at which inverter 24a switches can be thought of as ground potential, inverter 24a produces an output each time the output of capacitor _C3 passes through zero to produce the same output as shown in FIG. 4d. Inverter 24a thus produces a voltage level Va that is the average of V ₁ and V ₂
A control signal representative of Va is generated separately.

Inverter 24b is connected in a closed loop to compensate for long-term drift in the switching threshold of inverter 24a. It is known that a CMOS inverter connected in a closed loop generates a voltage representative of its switching threshold. Since inverters 24a and 24b share the same thermal environment, their switching thresholds are approximately the same, so inverter 24b applies an appropriate compensating bias voltage to the input of the other inverter 24a. act to always bias its input close to its switching level regardless of long-term drift.

In the embodiments described above, the transmitting means and the receiving means are constituted by a coil wound around a ferrite core, but other devices such as a light emitting diode or a photodetector may be used instead. . However, the coil configuration described above allows for a wide spacing between the cores, usually about 5 mm, and is not substantially affected by dirt etc. that accumulates thereon. It is particularly preferred because it can withstand vibrations, shocks, temperature changes, etc. that occur.

In the above description, the present invention is applied to a spark ignition device for an engine, but the present invention is not limited thereto, and can be similarly applied to, for example, fuel injection, exhaust gas recirculation, and other engine management systems. applicable.

[Brief explanation of drawings]

1 is a schematic perspective view showing an electrical displacement transducer of the present invention installed in an internal combustion engine; FIG. 2 is a perspective view showing a portion of the transducer shown in FIG. 1 in more detail; 3 is a schematic circuit diagram of this transducer, FIG. 4 is a diagram showing some electrical waveforms generated when the circuit of FIG. 3 is used, and FIG. 5 is a diagram of another embodiment of the present invention. FIG. 3 is a circuit diagram showing main parts. 2... Metal disc, 3... Electric sensing mechanism, 4...
...Control circuit, 6...Calculation circuit, 9...Zigzag portion, 10...Edge, 11...Coil, 13...
...Coil, 14...Ferrite core, 16...
Drive circuit, 19... Demodulator, 20... CMOS gate, 21... CMOS gate, 24... Differential amplifier (comparator).

Claims (1)

[Claims] 1. For transmitting energy and receiving this energy, a transmitting means and a receiving means are arranged at a distance from each other, and a transmitting means and a receiving means are arranged at a distance between the transmitting means and the receiving means. a moving member adapted to repeatedly interrupt the passage of energy from the transmitting means to the receiving means in connection with the movement thereof, and the receiving means is adapted to repeatedly interrupt the passage of energy from the transmitting means to the receiving means, and the receiving means is the first
and is configured to generate an output signal having a second magnitude different from the first magnitude during a period between the interruption periods, and further responsive to the output signal. means for generating a control signal having a magnitude representative of the average value of the first and second magnitudes; and comparing the magnitude of the output signal with the magnitude of the control signal to determine the beginning and end of the interruption. an electrical displacement transducer, comprising: a comparator that generates a signal representing . 2. The moving member comprises a rotating disk having a zigzag peripheral edge, and the transmitting means and the receiving means are arranged such that rotation of the disk causes the zigzag portion of the disk to cause the repetitive interruptions. A displacement transducer as claimed in claim 1. 3. A displacement transducer according to claim 2, wherein said transmitting means and said receiving means comprise two coils spaced apart from each other such that inductive coupling occurs between them. 4. The transmitting means includes a drive circuit adapted to supply an oscillatory electrical signal to one of the two coils, and the receiving means receives a signal induced in the other of the two coils. a demodulator connected to receive, the demodulator being adapted to generate a demodulated signal representative of the amplitude modulation of the signal generated in the second coil by movement of the moving member; A displacement transducer according to claim 3. 5. said drive circuit has an input terminal for receiving clock pulses and is adapted to generate said oscillatory electrical signal having a frequency controlled by the frequency of said clock pulses; 5. A displacement transducer as claimed in claim 4, wherein the displacement transducer is connected to receive. 6. The demodulator is composed of a CMOS transmission gate,
6. A displacement transducer according to claim 5, wherein the gate electrode of the transistor is connected to receive the clock pulse or the inverse of the clock pulse. 7. A displacement transformer according to one of claims 4 to 6, wherein the means for generating the control signal comprises a filter circuit connected to a demodulator and adapted to generate the control signal. Duusa. 8. The comparator has a first input terminal connected to receive the control signal from the filter circuit and a second input terminal connected to receive the demodulated signal from the demodulator. 8. A displacement transducer according to claim 7, comprising a differential amplifier.