GB1279130A - Improved apparatus for testing automobiles - Google Patents

Abstract

1279130 Vehicle testing stations for carrying out multiple tests in sequence on vehicles SCANIA-VABIS AB 26 Nov 1969 57857/69 Heading B7J [Also in Division G1] Automobile testing apparatus comprises a recording measuring unit 4 which has one or more recording instruments one of which provides a permanent record of test results the unit being controlled by a program unit 1 having several data inputs 16, 17, 18 connected to measuring points A, D, E of an automobile and arranged to make measurement connections 25 one after another between the data inputs and a measuring system in the instrument unit 4 and to maintain each measurement connection during a measuring operation, the arrangement being such that successive making of the measuring connections and interrupting of the preceding connections are caused by a timing transmitter 2 in dependence upon the angular position of the automobile crank-shaft. During a cycle controlled by the transmitter 2, the program unit 1 connects the measuring points A, E, D to the instrument 4 successively through pairs of leads 22, 25; 23, 25; 24, 25; of which the leads 22, 23, 24 carry signals determining respective paper feed rates and the leads 25 carry measurement signals. The program unit 1 has another input 15 connected to a measuring point C and is provided with a control circuit 3 to make further measuring connections 31, 32 and a simultaneous paper-feed connection 29, the duration and sequence of the measuring connections being independent of the transmitter 2. The instrument 4 may have more than one measuring system to allow several measurements to be recorded simultaneously. Where the vehicle has an I.C. engine with electric spark ignition the timing transmitter 2 may be a capacitive impulse transmitter comprising a large metal surface clamped against the ignition cable of the last sparking plug 9 in the firing order to form a capacitor with the core of 16 cable. When the plug 9 receives ignition voltage an impulse is produced and converted by a monostable trigger 12 into a standard impulse of 5 volts for application to the program unit 1. The transmitter 2 could be operated in other ways-mechanically, inductively or photoelectrically by using any part of the drive, e.g. the flywheel. The program unit 1 includes switching stages forming a counting chain controlled by the transmitter 2. Since compression in a cylinder of an I.C. engine is inversely proportional to the starter motor current, the cylinders may be compared for compression by recording the amplitude of the starter motor current for a complete firing cycle. Accordingly a program is initiated manually by inserting the ignition key and pressing the test starter button which causes the measuring point A at the positive terminal of the battery to be connected to the instrument 4 which then records the amplitude of the starter motor current until the last sparking plug 9 has fired. The resulting pulse from the transmitter 2 disconnects the instrument 4 from the point A and connects it to the output E of the primary side of the ignition coil 8 and the gaps between the peaks of the resulting record of voltage during the next firing cycle allows the contact closure angles (Q) to be estimated. The next pulse from the transmitter 2 causes recording of the current between the input terminal D os the primary winding of the ignition coil 8 and earth B through resistor 20, which provides information about voltage loss in various parts. After the next pulse from transmitter 2 control passes to the circuit 3 and simultaneous records are made at the terminals A, C of the battery to provide information about the state of the battery, with the engine held in check, by engaging top gear and applying the hand brake. Non-electrical variables relating to acceleration, power and braking may be recorded by providing pick-ups or transducers. The vehicle testing apparatus may also be used as a central instrument serving several testing locations. The instrument 4 is an oscillograph and may record by pen and ink, or magnetically for subsequent automatic transcription or, with a suitable coded input, by punching a tape. The record medium may be stationary and the recording element (e.g. pen, stylus or jet nozzle, light beam &c.) may be movable in two coordinate directions.