GB2064129A - Measuring rotational speed electrically - Google Patents

Measuring rotational speed electrically Download PDF

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Publication number
GB2064129A
GB2064129A GB8034585A GB8034585A GB2064129A GB 2064129 A GB2064129 A GB 2064129A GB 8034585 A GB8034585 A GB 8034585A GB 8034585 A GB8034585 A GB 8034585A GB 2064129 A GB2064129 A GB 2064129A
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GB
United Kingdom
Prior art keywords
signal
frequency
rotational speed
measuring
speed
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB8034585A
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GB2064129B (en
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Bosch Corp
Original Assignee
Diesel Kiki Co Ltd
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Filing date
Publication date
Application filed by Diesel Kiki Co Ltd filed Critical Diesel Kiki Co Ltd
Publication of GB2064129A publication Critical patent/GB2064129A/en
Application granted granted Critical
Publication of GB2064129B publication Critical patent/GB2064129B/en
Expired legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0097—Electrical control of supply of combustible mixture or its constituents using means for generating speed signals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/42—Devices characterised by the use of electric or magnetic means
    • G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
    • G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
    • G01P3/481—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals
    • G01P3/489—Digital circuits therefor
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/16—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop
    • H03L7/18—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using a frequency divider or counter in the loop
    • H03L7/183—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using a frequency divider or counter in the loop a time difference being used for locking the loop, the counter counting between fixed numbers or the frequency divider dividing by a fixed number

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Transmission And Conversion Of Sensor Element Output (AREA)
  • Linear Or Angular Velocity Measurement And Their Indicating Devices (AREA)

Abstract

A sensor output signal the frequency of which is determined by rotational speed is multiplied, and then the speed of rotation is computed on the basis of the frequency of the multiplied output signal thereby providing an accurate measure of the speed of rotation within a short time without need for generating a higher frequency signal in the sensor. To form the multiple of the frequency of a magnetic rotation sensor 3, the output of a V.C.O. 17 is fed via a variable divider 12 which divides the output by N, the desired multiple, and feeds it to a phase- detector 11 to which the sensor output is also applied, whereby the VCO output frequency is locked at N times the sensor output frequency. <IMAGE>

Description

SPECIFICATION Apparatus for measuring rotational speed This invention relates to apparatus for measuring rotational speed.
One of the previously known rotational speed measuring devices widely used for measuring rotational speed of various rotary machines has a sensor composed of a gear and an electromagnetic pick up coil. This device is widely used for measuring the rotational speed of an internal combustion engine. In this type of device, a number of cogs are arranged on the periphery of a gear which is securely connected to the crankshaft of the engine so as to rotate in accordance with the rotational speed of the engine. The electromagnetic pick up coil is located close to the gear in such a way that each cog approaches then goes away from the coil in sequence with the rotation of the engine, and thus a pulse signal which changes in frequency in proportion to the rotational speed of the crankshaft can be derived from the coil.This pulse signal is put into a counter which counts the number of pulses in a predetermined period, and the rotational speed of the engine can be measured on the basis of the count. As is apparent from the above description, to measure the rotational speed with high accuracy within a short time, a large number of the cogs is required.
However, the number of the cogs is limited, by such factors as, for example, accuracy of machining of the gear and the mechanical size of the pick up coil, so it is impossible to freely increase the number of the cogs beyond a certain limit. Even if the number of cogs were to be increased to the mechanically allowable maximum, this may not be industrially practicable because of the increase in production cost.
Therefore, a reduction in the time required for measuring speed of rotation can not be effectively achieved by increasing the number of the cogs. On the other hand, the device for measuring the speed of rotation of an internal combustion engine can also be used for measuring the rotational angle of the engine at the same time, and accurate measurement of the angle of rotation directly depends upon the number of the cogs, so it is impossible to carry out precise measurement of the angle of rotation if the number of the cogs is too small.
One object of the present invention is, therefore, to provide an improved apparatus for measuring speed of rotation.
Preferred embodiments of the invention aim to provide an apparatus for accurately measuring the speed of rotation of various rotary mechines within a short time, without increasing the number of cogs in the gear of the sensor.
Other embodiments of the invention aim to provide an apparatus for accurately measuring speed of rotation in less time than is required by prior art devices, without requiring mechanical reconstruction of the sensor for producing a signal indicative of the rotational speed of a rotary machine, and also to provide apparatus suitable for measuring rotational angular information derived from an internal combustion engine.
More generally, according to the present invention, there is provided an apparatus for measuring rotational speed, comprising: means for generating a signal which changes in frequency in relation to the speed of rotation of an object to be measured; means for multiplying the signal frequency output from said generating means; and, means for computing a speed of rotation on the basis of the multiplied signal frequency.
Thus, even if the frequency of the original signal produced from the sensor is low, the rotational speed can be precisely measured. As a result, precise measurement of rotational speed can be acieved with a conventional sensor with a gear having relatively few cogs. In a preferred embodiment, a phase locked loop circuit is employed as the frequency multiplier, so the multiplied signal is synchronized in phase with the original signal from the sensor and moreover a desired multiplying rate can be easily and accurately selected to adjust to an original signal from within a wide frequency range.
For a better understanding of the invention and to show how the same may be carried into effect, reference will be made by way of example to the accompanying drawing, in which: Fig. 1 is a diagrammatic illustration of one embodiment of the present invention applied to the measurement of rotational speed of an internal combustion engine; and Fig. 2 is a block diagram of a measuring device shown in Fig. 1.
Fig. 1 illustrates a rotational speed measuring device 1, positioned to measure and display the rotational speed of an internal combustion engine 2. The rotational speed measuring device 1 comprises a sensor 3 for producing a sensor output signal which changes in frequency in proportion to the speed of rotation of the engine 2 and a circuit unit 4, to which the sensor output signal produced from the sensor 3 is applied, incorporating an electronic circuit which processes the sensor output signal to display the rotational speed of the engine 2. The sensor 3 is composed of a gear 5 secured to a crankshaft 6 of the engine 2 so as to rotate in accordance with the rotation of the engine 2 and an electromagnetic pick up coil 7 located close to the gear 5.A number of cogs are formed on the periphery of the gear 5 (as shown in Fig. 2 in more detail) and a variable a. c. sensor output signal is produced from the electromagnetic pick up coil 7 as these cogs approach the coil 7 and then go away from the coil 7 in sequence with the rotation of the engine 2.
Fig. 2 illustrates a circuit diagram of the rotational speed measuring device 1 shown in Fig.
1. The sensor output signal from the coil 7 of the sensor 3 is fed into a waveform processing circuit 8 to generate a square wave signal having the same frequency as that of the sensor output signal. Therefore, the square wave signal derived from the waveform processing circuit 8 also changes in frequency in proportion to the rotational speed of the engine 2 and this square wave signal is sent. through an output line 9 to a frequency multiplier 10.
The frequency multiplier 10 is arranged as a phase locked loop (PLL) circuit and the square wave signal appearing on the line 9 is applied to a phase detector 11 of the PLL circuit. The phase detector 11 also receives a divided signal from a variable divider 12 through a line 13 so that the resulting phase difference signal which changes in magnitude in proportion to the difference in phase between these two input signals appears on an output line 14. The resulting phase difference signal is then passed through a low pass filter 1 5 to eliminate the high frequency components from the phase difference signal and the signal derived from the low pass filter 1 5 is sent through an amplifier 1 6 to a voltage controlled oscillator 1 7 as a frequency control signal.The output signal from the voltage controlled oscillator 17, which changes in frequency in accordance with the magnitude of the signal derived from the amplifier 15, is applied to the variable divider 12.
The variable divider 12 is a circuit for dividing the frequency of the output signal from the voltage controlled oscillator 17 in accordance with the dividing ratio determined by a selector 18.
Four bit digital data from the selector 18, indicative of a selected dividing ratio N, are applied to the variable divider 12 through lines 19, 20, 21 and 22 and the signal input applied through a line 23 to the variable divider 12 is divided by the ratio N determined by the content of the four bit digital data from the selector 1 8.
The divided signal from the variable divider 12 is applied to the phase detector 11, and then, the frequency of the output signal from the voltage controlled oscillator 17 is controlled in such a way that the phase of the signal from the variable divider 12 is coincident with that of the signal from the waveform processing circuit 8. As a result, if the dividing ratio set in the variable divider 12 is represented by N, the frequency of the signal derived from the voltage controlled oscillator 1 7 becomes exactly N times that on line 9. That is, the frequency of signal output from the waveform processing circuit 8 is multiplied in accordance with the data selected by the selector 18, and the resulting multiplied signal can be derived from voltage controlled oscillator 1 7 as a signal output of the frequency multiplier 10.
The signal output from the voltage controlled oscillator 1 7 is also applied to a pulse shaping circuit 24 to shape the waveform thereof and the resulting pulse signal from the pulse shaping circuit 24 is applied through a line 25 to a counter 26 as count pulses. In order to count the number of count pulses produced during a predetermined time by the use of the counter 26, count gate pulses, which are repetitively generated in a gate pulse generator 27 and have a predetermined pulse width, are applied through a line 28 to the counter 26, and then the counter 26 counts the number of pulses applied thereto in a time which corresponds to the pulse width of the count gate pulse.A count data D, is applied to a latch circuit 29 also receiving latch pulses P1, which are generated in a latch pulse generator 30 on the basis of the gate pulses derived from the gate pulse generator 27, through a line 31. Since the time when the latch pulse is generated is determined just after the counting operation of the counter 26 is inhibited by the count gate pulse, the resulting count data D1, which is obtained by counting the produced pulses in a time determined by each count gate pulse, is stored in the latch circuit 29 by the application of the latch pulse, and then the latched data D2 is applied to a data cor;verter 32 while the next data from the counter 26 is being latched in the latch circuit 29.
The data converter 32 also receives a data D3 indicative of the dividing ratio from the selector 1 8 and the latched data D2 is converted into the rotational speed data at that instant on the basis of these two input data. The resulting data D4 indicative of the rotational speed of the engine 2 is displayed by display device 33 to indicate the resulting rotative speed.
The latch pulses from the latch pulse generator 30 are also applied through a delay circuit 34 to the counter 26 as a reset pulses. Therefore, the counter 26 is reset by the reset pulses after every latching of the D, in the latch circuit 29 so that the counter 26 data can be ready to carry out the next counting operation.
According to the rotational speed measuring device 1, since the frequency multiplier 10 can generate any frequency multiple of the sensor output signal from the waveform processing circuit 8, the characteristics of the device 1 may be improved without increasing the number of cogs in the gear 5. Therefore, measurement of the rotational speed of various rotary machines can be achieved to a desired high accuracy within a short time by increasing the dividing rate set in the variable divider 12. For example, assuming that the gear 2 has 120 cogs and rotates at 6000 r.p.m., since the frequency of the sensor ouptut signal from the waveform processing circuit 8 is 12 kHz, 0.5 seconds count gate time is required to attain the accuracy of 1 r.p.m. in the measuring operation when the multiplier 10 is not employed.
However, if the 12 kHz signal is multiplied by the multiplier 10 to produce a signal with a frequency ten times the 12 kHz, it follows that an 0.05 seconds count gate time is required for attaining the accuracy of 1 r.p.m.
Consequently, the accuracy of measurement can be maintained at greater than a predetermined accuracy by increasing the dividing rate when the rotational speed is relatively low, and unnecessary increase in frequency of the signal derived from the multiplier 10 can be effectively avoided by reducing the dividing rate of the variable divider 12 when the rotational speed is relatively high. As understood from the foregoing description, regardless of the number of the cogs in the gear 5, the accuracy of measurement and the gate time can be determined at will by selecting the dividing rate of the variable divider 12.
Although the present invention has been described using as an example a rotational speed measuring device for measuring the rotational speed of an internal combustion engine, the present invention is not limited to such and is also applicable to the measurement of rotational speed of any other rotary machine.

Claims (9)

1. An apparatus for measuring rotational speed, comprising: means for generating a signal which changes in frequency in relation to the speed of rotation of an object to be measured; means for multiplying the signal frequency output from said generating means; and, means for computing a speed of rotation on the basis of the multiplied signal frequency.
2. An apparatus for measuring rotational speed as claimed in claim 1, wherein said generating means comprises a coil for detecting a change in magnetic field and a rotating member which is arranged to rotate in relation to rotation of the object so as to create a change in the magnetic field of said coil in accordance with the speed of rotation.
3. An apparatus for measuring rotational speed as claimed in claim 1 or 2, wherein said multiplying means is a phase locked loop circuit having a voltage controlled oscillator, a frequency divider for dividing an output signal from said voltage controlled oscillator, and a phase detector for producing a phase signal indicative of a difference in phase between the signal from the generating means and the signal from said frequency divider, the phase signal being applied to said voltage controlled oscillator as a frequency control signal.
4. An apparatus for measuring rotational speed as claimed in claim 3, wherein said frequency divider is a variable divider.
5. An apparatus for measuring rotational speed as claimed in any preceding claim, wherein said computing means has a frequency counter for measuring the frequency of the signal multiplied by said multiplying means, and a data converter for converting the result from said frequency counter into corresponding rotational speed data.
6. An apparatus for measuring rotatonal speed as claimed in any preceding claim, further comprising a display means for displaying a resulting rotational speed in response to a data derived from said computing means.
7. An apparatus for measuring rotational speed, substantially as hereinbefore described with reference to the accompanying drawing.
8. A rotary device provided with an apparatus according to any preceding claim.
9. An internal combustion engine provided with an apparatus according to any one of claims 1 to 7.
GB8034585A 1979-11-29 1980-10-28 Measuring rotational speed electrically Expired GB2064129B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP15470179A JPS5677759A (en) 1979-11-29 1979-11-29 Detecting device of rotational frequency

Publications (2)

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GB2064129A true GB2064129A (en) 1981-06-10
GB2064129B GB2064129B (en) 1983-07-06

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DE (1) DE3044924A1 (en)
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0113455A1 (en) * 1982-12-15 1984-07-18 Honeywell Inc. Apparatus for counting the number of fringe changes of a varying interference fringe pattern
EP0130762A2 (en) * 1983-07-02 1985-01-09 LUCAS INDUSTRIES public limited company Angular position detector
FR2558619A1 (en) * 1984-01-24 1985-07-26 Ramses Method and electronic device for simulation of at least one position sensor, for at least one moving member
US4742297A (en) * 1985-07-08 1988-05-03 Teleflex Incorporated Programmable cycle meter
FR2645648A1 (en) * 1989-04-07 1990-10-12 Lorraine Laminage Device for measuring the speed of rotation, in particular of a mill stand motor

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61137219U (en) * 1985-02-15 1986-08-26
JP3503593B2 (en) * 2000-01-20 2004-03-08 株式会社デンソー Engine control device

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0113455A1 (en) * 1982-12-15 1984-07-18 Honeywell Inc. Apparatus for counting the number of fringe changes of a varying interference fringe pattern
EP0130762A2 (en) * 1983-07-02 1985-01-09 LUCAS INDUSTRIES public limited company Angular position detector
EP0130762A3 (en) * 1983-07-02 1986-02-12 Lucas Industries Public Limited Company Angular position detector
FR2558619A1 (en) * 1984-01-24 1985-07-26 Ramses Method and electronic device for simulation of at least one position sensor, for at least one moving member
US4742297A (en) * 1985-07-08 1988-05-03 Teleflex Incorporated Programmable cycle meter
FR2645648A1 (en) * 1989-04-07 1990-10-12 Lorraine Laminage Device for measuring the speed of rotation, in particular of a mill stand motor

Also Published As

Publication number Publication date
JPS5677759A (en) 1981-06-26
DE3044924A1 (en) 1982-05-27
GB2064129B (en) 1983-07-06

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PCNP Patent ceased through non-payment of renewal fee