Patent GB-1433062-A (GB)
Title: Hydraulic power absorbing apparatus
IPC: G01M17/007
Filed: 1973-05-02
Abstract: 1433062 Automatic control of power absorption CLAYTON MFG CO 2 May 1973 [4 May 1972] Headings G3N and G3R [Also in Division G1] In hydraulic power absorbing apparatus, the actual rotational speed, and the torque absorbed by a rotary power absorber, in which the torque absorbed is proportional to the level of fill of working fluid, are measured, and the torque  absorption characteristics are adjusted either (a) to maintain a given torque absorption profile, or (b) to maintain a given rotational speed profile, or (c) to maintain torque absorption substantially proportional to the square of the rotational speed, thus simulating the characteristics of a vehicle being tested, on a level road. As shown, the housing 14 of the hydraulic torque absorber is connected via torque arm 34 to strain gauge 36 providing a torque signal to comparator 68 receiving also a signal from D.C. tacho 32 via squaring circuit 60 and torque select circuit 70, switches 71a-71f being set to provide a specific relation between programmed torque on lead 73 and the speed squared signal on lead 61 in accordance with the weight of the vehicle under test. Insertion of resistor 78 across the actual torque line 75 simulates the power loss due to auxiliaries (vehicle air conditioning). Also in accordance with vehicle weight, an inertia select circuit 80, selectively energizes electromagnet or pneumatic clutches 25, 27, 29, 31 causing rotation, with drive roll 16, of one or more flywheels 24, 26, 28, 30 simulating vehicle inertia. For testing in accordance with a given speed profile, the actual speed signal is fed directly to comparator 68, which receives a constant or variable speed reference voltage on its other input, see Fig. 9 (not shown). Alternatively a torque reference voltage from unit (132), Fig. 10 (not shown) is fed to the comparator receiving also the actual torque signal. The comparator output is fed to driver circuits 84, 86, 88, 90 controlling valves 40-43, themselves controlling the water level in housing 14, and hence torque absorption, in a sense to minimize the error between the comparator input signals. Driver circuits, Figs. 5, 6 (not shown). Should the absorption requirement increase, after a given dead-band, transistor (122, Fig. 5); when conducting enabling high frequency oscillator (129, 130), triggering semi-conductor switch 12 in an A.C. circuit energizing the coil of valve 41a, see also Fig. 4 (not shown); is switched on for a progressively larger portion of each sawtooth wave generated by adjustable rate pulser 92 (Fig. 6), periodically opening and closing valve 41, controlling water entry to housing 14, for a higher proportion of the sawtooth, until it is open always. For higher absorption requirements, valve 40, having a similar driver circuit without connection to the pulser, is opened. Valves 42 and 43, controlling water exit from the housing 14, are similarly controlled if required torque absorption decreases, to give a fluid-flow characteristic of the form displayed in Fig. 3 (not shown). Driver cutoff 94 provides a bias supply to the driver circuits, so that they function only when the actual speed is above a threshold value. Speed and torque signals are multipled in unit 64 to give a measure of power output. Torque absorber. The rotor 11 comprises vanes interacting with stator vanes to increase the water pressure between the inlet and the outlet. The absorbed torque is proportional to the water level in housing 14. There may be a heat exchanger, (not shown) in the housing, water circulating through coils, entering via valve 55 controlling the temperature. The stator and housing are mounted in bearings (not shown), torque reaction being taken by gauge 36. Instead of a heat exchanger, the water in the housing may be recirculated. The vehicle wheel rests between driver, and idler rollers 16, 20, and the speed tacho may be coupled to either of them. The crank-shaft of an engine under test when not mounted in a vehicle may be directly coupled to the stator. Vehicle tests simulating a given short journey during which exhaust, crank-case, and fuel tank emissions are monitored may be carried out.