ENGINE THERMODYNAMIC CYCLE ANALYSER

• US 3,815,410 A
• Filed: 12/07/1972
• Issued: 06/11/1974
• Est. Priority Date: 12/07/1972
• Status: Expired due to Term

• Current Assignee: Caterpillar Incorporated
• Original Assignee: John L. Hoffman, Maurice E. Schaefer, William L. Brown Jr
• Inventors: Brown, William L. Jr., Hoffman, John L., Schaefer, Maurice E.
• Primary Examiner(s): Myracle, Jerry W.
• Application Number:
  US05/313,115
• Time in Patent Office: 551 Days
• Field of Search: 73/117.2,116,115,117.3
• US Class Current: 73/114.13
• CPC Class Codes: F02B 2075/025 two
• CPC Class Codes: G01L 23/08 operated electrically G01L23/22 takes precedence

Abstract

Instumentation attachable to an engine provides for a rapid and highly accurate measurement of power produced at the face of a piston in terms of Indicated Mean Effective Pressure or other indicated power units and may also provide a thermodynamic cycle diagram display and other data of interest in analyzing engine performance. A pressure transducer at the combustion chamber provides an electrical signal indicative of instantaneous pressure while a volume signal generator coupled to the engine crank shaft provides a voltage proportional to instantaneous combustion chamber volume. A circuit differentiates the volume signal to obtain a piston velocity signal which is multiplied by the instantaneous pressure signal and averaged for readout at a digital volt meter in terms of Indicated Mean Effective Pressure or the like. The volume signal generator also produces accurate top dead center and bottom dead center pulses to control gating means for obtaining information applicable to selected portions of the total engine cycle and for facilitating calibration.

Claims

1. Apparatus for determining indicated power in an engine wherein the volume of a combustion chamber and the pressure therein each vary cyclically in the course of engine operation, comprising;

pressure transducer mEans attachable to said engine for producing a pressure signal voltage which varies in accordance with said pressure variation in said combustion chamber, volume signal generating means attachable to said engine for producing a volume signal voltage which varies in accordance with said volume variation of said combustion chamber, multiplier means of the form having first and second inputs and an output having a product voltage which varies in accordance with the product of variable voltages applied to said inputs, pressure signal channel means connected between said pressure transducer means and said first input of said multiplier means, volume signal channel means connected between said volume signal generating means and said second input of said multiplier means, voltmeter means for indicating a value proportional to the magnitude of a voltage applied to an input thereof, an integrating circuit connected between said output of said multiplier means and said input of said voltmeter means for applying a voltage to said voltmeter means input which is an averaged value of said variable output voltage of said multiplier means, and amplifier means for selectively adjusting the gain of at least one of said pressure signal channel means and said volume signal channel means.

2. Apparatus for determining indicated power in an engine wherein the volume of a combustion chamber and the pressure therein each vary cyclically in the course of engine operation, comprising:

pressure transducer means attachable to said engine for producing a pressure signal voltage which varies in accordance with said pressure variation in said combustion chamber, volume signal generating means attachable to said engine for producing a volume signal voltage which varies in accordance with said volume variation of said combustion chamber, multiplier means of the form having first and second inputs and an output having a product voltage which varies in accordance with the product of variable voltages applied to said inputs, pressure signal channel means connected between said pressure transducer means and said first input of said multiplier means, volume signal channel means connected between said volume signal generating means and said second input of said multiplier means, voltmeter means for indicating a value proportional to the magnitude of a voltage applied to an input thereof, an integrating circuit connected between said output of said multiplier means and said input of said voltmeter means for applying a voltage to said voltmeter means input means is an averaged value of said variable output voltage of said multiplier means, and means for adjusting signal phase shift in said pressure signal channel means and said volume signal channel means.

3. Apparatus for determining indicated power in an engine wherein the volume of a combustion chamber and the pressure therein each vary cyclically in the course of engine operation, and wherein said engine includes a rotary element which rotates in synchronism with said variations of the volume of said combustion chamber, comprising:

pressure transducer means attachable to said engine for producing a pressure signal voltage which varies in accordance with said pressure variation in said combustion chamber, volume signal generating means attachable to said engine for producing a volume signal voltage which varies in accordance with said volume variation of said combustion chamber, said volume signal generating means having a rotatable shaft coupled to said rotary element for rotation therewith, photosensitive electrical means for producing a voltage proportional to the amount of light falling on said device, opaque means having a slot therein directed radially with respect to the axis of rotation of said shaft, a circular disk mounted on said shaft in eccentric relation thereto for rotation therewith, and having an edge which moves radially inwardly and outwardly along said sLot as said shaft rotates to cyclically vary the effective length of said slot, a housing enclosing said opaque means and said disk, a remote light source situated apart from said engine and said housing, and light transmitting means extending from said light source into said housing and toward said shaft and having a light emitting end which directs light from said source toward said photosensitive element through said slot, multiplier means of the form having first and second inputs and an output having a product voltage which varies in accordance with the product of variable voltages applied to said inputs, pressure signal channel means connected between said pressure transducer means and said first input of said multiplier means, volume signal channel means connected between said volume signal generating means and said second input of said multiplier means, voltmeter means for indicating a value proportional to the magnitude of a voltage applied to an input thereof, and an integrating circuit connected between said output of said multiplier means and said input of said voltmeter means for applying a voltage to said voltmeter means input which is an averaged value of said variable output voltage of said multiplier means.

4. Apparatus for determining indicated power in an engine wherein the volume of a combustion chamber and the pressure therein each vary cyclically in the course of engine operation, comprising;

pressure transducer means attachable to said engine for producing a pressure signal voltage which varies in accordance with said pressure variation in said combustion chamber, volume signal generating means attachable to said engine for producing a volume signal voltage which varies in accordance with said volume variation of said combustion chamber, multiplier means of the form having first and second inputs and an output having a product voltage which varies in accordance with the product of variable voltages applied to said inputs, pressure signal channel means connected between said pressure transducer means and said first input of said multiplier means, volume signal channel means connected between said volume signal generating means and said second input of said multiplier means, voltmeter means for indicating a value proportional to the magnitude of a voltage applied to an input thereof, an integrating circuit connected between said output of said multiplier means and said input of said voltmeter means for applying a voltage to said voltmeter means input which is an averaged value of said variable output voltage of said multiplier means, calibration means including a calibration voltage source for producing a predetermined known voltage corresponding to the voltage produced by said pressure transducer means by a known pressure within said combustion chamber, and calibration switch means for selectively and temporarily decoupling said pressure signal channel means from said pressure transducer means while coupling said calibration voltage source to said pressure signal channel means, electrical signal controlled switch means connected between said calibration voltage source and said pressure signal transmitting means, and gating means for producing electrical gating signals for opening and closing said electrical signal controlled switch means during a predetermined portion of each successive full cycle of said engine.

5. Apparatus for determining indicated power in an engine wherein the volume of a combustion chamber and the pressure therein each vary cyclically in the course of engine operation, comprising;

pressure transducer means attachable to said engine for producing a pressure signal voltage which varies in accordance with said pressure variation in said combustion chamber, volume signal generating means attachable to said engine for producing a volume signal voltage which varies in accordance with said volume variation of said combustion chamber, multiplier meaNs of the form having first and second inputs and an output having a product voltage which varies in accordance with the product of variable voltages applied to said inputs, pressure signal channel means connected between said pressure transducer means and said first input of said multiplier means, volume signal channel means connected between said volume signal generating means and said second input of said multiplier means, voltmeter means for indicating a value proportional to the magnitude of a voltage applied to an input thereof, an integrating circuit connected between said output of said multiplier means and said input of said voltmeter means for applying a voltage to said voltmeter means input which is an averaged value of said variable output voltage of said multiplier means, timing pulse generating means attachable to said engine for producing a discrete timing pulse at a predetermined point in each successive cycle of said engine, electronic switch means for transmitting said product voltage of said multiplier means to said integrating circuit, and gating circuit means responsive to said timing pulses for closing said electronic switch means during a predetermined portion of each successive cycle of said engine and for opening said electronic switch means during other portions of each cycle whereby said voltmeter means indicates power for said predetermined portion of the cycle of said engine.

6. The combination defined in claim 5 further comprising manually operable switch means having a first position at which said output of said multiplier means is coupled to said integrating circuit independently of said electronic switch means and having a second position at which said output of said multiplier means is coupled to said integrating circuit through said electronic switch means.

7. The combination defined in claim 5 wherein the element which moves to cyclically vary the volume of said combustion chamber of said engine is a reciprocating piston therein and wherein said timing pulse generating means comprises means for generating a top dead center pulse each time said piston reduces said combustion chamber to the minimum volume thereof and for producing a bottom dead center pulse each time said piston expands said combustion chamber volume to the maximum volume thereof, and wherein said gating circuit means comprises a bi-stable circuit element having a trigger input receiving said timing pulses and having an output coupled to said electronic switch means to control said electronic switch means and having means for changing the state of said output to close said electronic switch in response to alternate ones of said bottom dead center pulses and for opening said electronic switch in response to the others of said bottom dead center pulses and for holding said bistable circuit element output unchanged when said top dead center pulses are applied to said trigger input thereof.

8. Apparatus for determining indicated power in an engine having a combustion chamber with a reciprocal piston therein and having a rotary element which turns in synchronism with the reciprocal motion of said piston, comprising;

a pressure transducer mountable on said engine and having a surface exposable to pressure within said combustion chamber and producing a pressure signal voltage proportional to instantaneous pressure within said combustion chamber, a volume signal generator attachable to said engine and having a rotatable shaft connectable to said rotary element of said engine and having a photosensitive electrical circuit element for producing a voltage proportional to ambient light reaching said element and having a light source for directing light towards said element and means driven by said shaft and extending into the light path between said source and said photosensitive element for varying the amount of light which reaches said element in accordance with the instantaneous position of said piston in said combustion chAmber whereby said photosensitive element produces a volume signal voltage proportional to the instantaneous volume of said combustion chamber, said volume signal generator further having electro-optical means for producing a timing pulse each time said piston reaches top dead center position and bottom dead center position, an analog multiplier of the form having first and second inputs for receiving variable voltages and having an output at which voltage is proportional to the instantaneous product of voltages present at said inputs at any given time, pressure signal channel means connected between said pressure transducer and said first input of said analog multiplier and having means for adjusting the gain through said pressure signal channel and means for suppressing cyclical components of said pressure signal voltage above a predetermined frequency which is higher than the cycling rate of said engine and having means for selectively adjusting the phase shift of signals transmitted through said pressure signal channel, means defining a volume signal channel connected between said photosensitive element of volume signal generator and said second input of said analog multiplier and having means for differentiating said volume signal voltage to produce a piston velocity signal voltage and means for suppressing signals above a predetermined frequency and means for selectively adjusting the gain through said volume signal channel, a voltmeter for indicating a numerical value proportional to a voltage applied to said voltmeter, an integrating circuit having an input and having an output coupled to said voltmeter, an electronic switch having a control terminal to which a signal may be applied to close said switch, manually operable cycle selector switch means for selectively connecting said output of said analog multiplier to said input of said integrating circuit independently of said electronic switch at one setting of said selector switch and for connecting said output of said analog multiplier to said input of said integrating circuit through said electronic switch at another setting of said selector switch, a first bi-stable circuit element having a trigger input and having an inverted output and a noninverted output, manual switch means for selectively connecting said control terminal of said analog switch to a selected one of said outputs of said first bi-stable circuit element, means for transmitting said timing pulses from said volume signal generator to said trigger input of said first bi-stable circuit element, means connected between said volume signal generator and said first bi-stable circuit element for inhibiting a change of state of said outputs of said first bi-stable circuit element in response to timing pulses received at said trigger input thereof when said volume signal is above a predetermined level whereby said first bi-stable circuit element and said electronic switch respond only to said bottom dead center pulses and not to said top dead center pulses.

9. The combination defined in claim 8 further comprising means for displaying the amplitude of signals transmitted to said integrating circuit through said electronic switch whereby it may be ascertained if said voltmeter is indicating power for a working cycle or pumping cycle of said engine and whereby said switch means may be operated to connect said control terminal of said electronic switch to the other of said outputs of said first bi-stable circuit element to determine indicated power for the other cycle of said engine.

10. The combination defined in claim 8 having calibration means comprising a calibration voltage source of known magnitude electrically controlled switching means for transmitting a fixed known calibration voltage from said source to said pressure signal channel means in response to a gating signal applied to said electrically controlled switching means, a second bi-stable circuit element having a trigger Input and having a non-inverted output and an inverted output, switch means for selectively connecting said electrical circuit element to a selected one of said outputs of said second bi-stable circuit element, and means for transmitting said timing pulses to said trigger input of said second bi-stable circuit element whereby said calibration voltage is transmitted to said pressure signal channel means only during alternate intervals between the top dead center and bottom dead center position of said piston.