US3908614A - Throttle angle transducers - Google Patents

Abstract

A throttle angle transducer having a non-linear output which changes more rapidly at small throttle angles than at large throttle angles, comprises a linear potentiometer operated by the throttle pedal, and an oscillator having a period which is determined by the potentiometer output and which varies linearly from the throttle angle. The frequency of the oscillator is employed to provide the required output from a transducer.

Description

United States Patent Ironside et a].

THROTTLE ANGLE TRANSDUCERS Inventors:

Assignee:

Filed:

Appl. No.:

John Michael lronside, Birmingham; Michael Herbert Cops, Solihull, both of England Lucas Electrical Company Limited, Birmingham, England Feb. 13, 1973 Foreign Application Priority Data Feb. 25. 1972 US. CL... int. CL

United Kingdom 8937/72 123/32 EA; 123/119 R Field of Search 123/119 R, 132 EA References Cited UNITED STATES PATENTS TRANSDUCER Aono et al 123/32 EA MEMORY i i DEl/ICE 51 Sept. 30, 1975 3,703,162 11/1972 Aono 123/32 EA 3.719.176 3/1973 Shinoda et al. 123/32 EA 1765.380 10/1973 Rachel et al. 123/32 EA 3,786,788 1/1974 Suda et al 123/32 EA Primary E.\'aminer-Charles J. Myhre Assistant Examiner-Joseph A. C angelosi Attorney, Agent, or Firm-Holman & Stern [57] ABSTRACT 1 Claim, 4 Drawing Figures FUEL INJECTION CO NTROL w '5 OSCILLATORS ,is ,e

idem NETWORK LATCHING COUNTER -COUNTER LOGIC =:?TNETW0RK F? El US. Patent Sept. 30,1975 3,908,614

MEMORY FUEL \NJECTION TRANSDUCER DEVICE CONTROL IE IS T LATGHING COUNTER COUNTER mm W QWETWoRK 0SClLLAT0RS I7 g /l 9 E NETWORK PERIOD Flea.

THROTTLE ANGLE EFFECTIVE FREQUENCY FREQUENCY THEGTTLE ANGLE- THEOTTLE ANGLE FTC-3.3. FIGA.

THROTTLE ANGLE TRANSDUCERS This invention relates to throttle angle transducers for use in fuel injection systems.

In order to attain satisfactory accuracy in a fuel injection system, it is desirable to employ a throttle angle transducer having a non-linear output which changes more rapidly at small throttle angles than at large throttle angles, because at small throttle angles the rate of change of flow of air when the pedal is moved is substantially higher than at large throttle angles. The desired output can be obtained by employing a nonlinear potentiometer, but such potentiometers are expensive and difficult to manufacture to the required degree of accuracy.

The invention resides in a throttle angle transducer having a non-linear output which changes more rapidly at small throttle angles than at large throttle angles, comprising a linear potentiometer operated by the throttle pedal, and an oscillator having a period which is determined by the potentiometer output and varies linearly with the position of the throttle pedal, and the frequency of the oscillator being employed to provide the required output from the transducer.

Preferably, the frequency is measured digitally by using a counting device to count to a value representing the frequency at any given instant, and in this case the shape of the frequency against throttle angle curve can be changed to suit any particular application by subtracting a fixed digital number from each digital count.

The invention further resides in a fuel injection system for a vehicle, including a throttle angle transducer as specified above, a second transducer for measuring a further engine parameter, and a memory device to which the outputs from the transducers are fed, the memory device determining the quantity of fuel injected in accordance with the values of the two parameters.

An example of the invention is illustrated in the accompanying drawings, in which:

FIG. 1 is a block diagram, and

FIGS. 2 to 4 are graphs illustrating roughly wave forms pertinent to the example.

Referring first to FIG. 1, there is provided a memory device 11 which receives an electrical input from a transducer 12 representing either engine speed or manifold depression, and receives a further electrical input from a latching counter 13 in a manner to be described, the input from the counter 13 to the memory device 11 representing throttle angle. The memory device 1 1 produces an output, the value of which is dependent on the values of the two input signals it receives, and this output is used to operate means 14 for controlling the injection of fuel to the engine ofa road vehicle. The exact nature of the memory device 11 is not important for an understanding of the present invention.

In order to obtain a signal representing a throttle angle, there is provided a potentiometer 15 which produces a linear output, that is to say a voltage which varies linearly with throttle angle. The signal obtained from the slider of the potentionmeter 15 is fed to a freerunning square wave oscillator 16 of any convenient form, the arrangement being such that the signal received by the oscillator 16 from the potentiometer l5 varies the period of the oscillator, so that the period of the oscillator varies with throttle angle in a linear manner as indicated in FIG. 2. It will be appreciated that since the frequency of an oscillator is inversely proportional to its period, then the frequency of the oscillator 16 will vary with throttle angle in the manner shown in FIG. 3.

The output from the oscillator 16 is fed to a counter 17 which passes a signal to the counter 13 from time to time in a manner to be explained. The circuit also includes a fixed frequency oscillator 18 which has a period substantially in excess of the period of the oscillator 16. In one particular example, the period of the oscillator 18 is equal to the time taken for the oscillator 16 to produce 32 pulses, even when the oscillator 16 is operating at its minimum frequency. The output from the oscillator 18 is fed to a logic network 19, and at the commencement of a period of oscillation of the oscillator 18, the logic network produces one output pulse which is applied to the counter 13 so that the counter 13 is fed with the information which at that moment is present in the counter 17. The counter 13 then retains this information until the beginning of the next period of the oscillator 18. Moreover, at the commencement of the period of the oscillator 18, the logic network 19 produces a further pulse which clears the counter 17, which then starts to receive a count from the oscillator 16. After the counter 17 has received 32 pulses, a further logic network 21 clears the counter 17 again, but the counter 17 then starts filling again by virtue of further pulses received from the counter 16. Thus, it will be seen that at the end of a period of the oscillator 18, when the reading of the counter 17 will be passed onto the counter 13, the reading in the counter 17 will represent the number of pulses received from the oscillator 16 during the fixed period of the oscillator 18, less 32 pulses by virtue of the logic network 21. The effect of subtracting these 32 pulses from the reading of the counter 17 is that the graph shown in FIG. 3 effectively becomes of the form shown in FIG. 4. It will be seen that this graph is of the form required, in that the effective frequency shown in FIG. 4, that is to say the frequency after allowance is made for the 32 subtracted pulses, varies with throttle angle in such a manner that at small throttle angles the signal received by the counter 13 will change more rapidly than at large throttle angles.

We claim:

1. A throttle angle transducer which can be used in a fuel injection system for a vehicle having a throttle pedal, and which has a nonlinear output which changes more rapidly at small throttle angles than at large throttle angles, said transducer comprising in combination a linear potentiometer having movable thereon a slider which is driven by the throttle pedal which determines said throttle angle, an oscillator, means coupling said oscillator to said slider, said potentiometer determining the period of said oscillator, whereby said period varies linearly with the position of said slider, and an output stage coupled to said oscillator, said output stage providing an output signal which varies linearly with the frequency of the oscillator, the frequency of said oscillator being determined solely by its period, said output stage effecting digital measurement of said oscillator frequency and including means comprising a digital counting device for counting to a value representing the oscillator frequency at any given instance, the shape of the frequency against the throttle angle curve being determined by the output of means for subtracting a fixed digital number from each digital count.

. UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,908,614

' DATE I September 30, 1975 INVENT0R(5) I John M. Ironside, et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[30] Forelgn PIlOIltY Data:

Great Britain No. 8925/72 filed February 25, 1972 Signed and Scaled this thir Day Of January 1976 [SEAL] Attest:

RUTH c. MASON C. MARSHALL DANN Arresting ffic Commissioner ufPatenls and Trademarks

Claims (1)

1. A throttle angle transducer which can be used in a fuel injection system for a vehicle having a throttle pedal, and which has a nonlinear output which changes more rapidly at small throttle angles than at large throttle angles, said transducer comprising in combination a linear potentiometer having movable thereon a slider which is driven by the throttle pedal which determines said throttle angle, an oscillator, means coupling said oscillator to said slider, said potentiometer determining the period of said oscillator, whereby said period varies linearly with the position of said slider, and an output stage coupled to said oscillator, said output stage providing an output signal which varies linearly with the frequency of the oscillator, the frequency of said oscillator being determined solely by its period, said output stage effecting digital measurement of said oscillator frequency and including means comprising a digital counting device for counting to a value representing the oscillator frequency at any given instance, the shape of the frequency against the throttle angle curve being determined by the output of means for subtracting a fixed digital number from Each digital count.

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