REGENERATIVE SYSTEM FOR TESTING TORQUE CONVERTERS

AND OTHER TRANSMISSION COUPLING DEVICES RELATED PATENT APPLICATION

This application claims the benefit of U.S. Provisional Application No. 60/753,073 filed December 12, 2005, and entitled "Regenerative System for Testing Torque Converters and Other Transmission Coupling Devices . " TECHNICAL FIELD OF THE INVENTION This invention relates to the testing of mechanical devices, and in particular, testing automotive torque converters and other transmission-related components. BACKGROUND OF THE INVENTION

All vehicles need some means for allowing the engine to continue turning if the vehicle comes to a stop. Manual transmission vehicles use a clutch, which disconnects the engine from the transmission. Automatic transmission vehicles use a torque converter, a type of fluid coupling that allows the engine to turn somewhat independently of the transmission.

Engineers who design automatic transmissions and their components have devised various methods for testing and evaluating them, including torque converters. Evaluating the performance of a torque converter requires that power be supplied to, as well as absorbed from, the torque converter. The use of actual engines as the driving power for such testing is usually considered impractical because of the cost of fuel and maintenance and the problem of controlling emissions. As a result, electric motors are often used as the driving device, but these motors are required to be large and expensive for proper testing and the high accelerations during testing

can be damaging to the motor. The absorbing devices are typically dynamometers, which dissipate energy in the form of heat or electricity, and can also be costly. BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein: FIGURE 1 illustrates a test system for testing a torque converter or other transmission coupling device in accordance with the invention. DETAILED DESCRIPTION OF THE INVENTION

The invention described herein is directed to a "regenerative test stand" and an associated method for evaluating torque converters and similar devices . As explained below, the test stand absorbs power from the torque converter, regenerates the power and supplies it to the input of the torque converter. More specifically, hydraulic pumps and motors are used to recover energy at the output of the torque converter and to use the energy to assist in powering the input to the torque converter. Make-up power is provided by an electric motor.

FIGURE 1 illustrates a regenerative test system 100 in accordance with the invention. In the example of FIGURE 1, system 100 is being used to test a torque converter 104. Although this description is mostly in terms of testing a torque converter such as the type used for today's vehicles, the same concepts apply to other "fluid couplers" . Such devices may be found in applications other than automotive, such as for use with industrial type variable speed engines. Furthermore, the

regenerative test stand has application to gear type transmissions, rather than fluid couplers. Thus, in a most general sense, any type of transmission device that couples the mechanical power of an engine or motor to mechanical power for a driveline may be tested using system 100, and the test device is generally referred to herein as an "transmission coupling device"

An electric motor 101, which may be a constant speed motor, is used to make up for system losses. The required output power of motor 101 is determined by the test conditions and the system losses.

A variable displacement hydraulic pump 102 is driven by the motor shaft of motor 101. An example of a suitable type of pump is a variable displacement pump having a capacity of 130 cc . Pump 102 may be an axial piston pump, that is, . a pump that uses an axial reciprocating piston motion principle to rotate the output shaft, but other types of pumps are possible.

Pump 102 delivers high-pressure hydraulic fluid to a variable displacement hydraulic motor 103, i.e., a motor that transforms fluid energy into rotary mechanical power, which typically is applied to a load via shaft. In system 100, motor 103 delivers its mechanical power to the torque converter 104. In the example of FIGURE 1, motor 103 is a bent-axis piston motor having a capacity of 110 cc . Bent-axis piston motors develop torque through a reaction to pressure on reciprocating pistons, such as by mounting the cylinders and drive shaft at an angle to each other with the reaction being against a drive-shaft flange. In general, bent-axis motors are capable of higher speeds

than other hydraulic motors. However, other piston and non piston type hydraulic motors could be used.

Torque converter 104, which is driven by motor 103, is shown mounted on a headstand 104a. Torque meters 104b at the input and output of torque converter 104 provide torque values to the control system 101a.

Mechanical power is absorbed from the torque converter 104 by a variable displacement hydraulic pump 105, which converts this mechanical power into hydraulic power. In the example of FIGURE 1, pump 105 is a bent- axis piston pump, which is capable of achieving higher speeds than other types of pumps, but other types of pumps may be used.

High-pressure fluid from pump 105 is delivered to motor 106, which is mounted on a common shaft with pump

102 and motor 101. This permits both motor 106 and motor 101 to drive pump 102. An example of a suitable motor 106 is an axial piston motor having a capacity of 130 cc .

It should be understood that the pumps and motors described herein may be the same device. In other words, the same device may be used as a pump or motor depending on whether its input is hydraulic and output mechanical, or vice versa. In general, these pumps and motors can be various types of positive variable displacement devices, which may be controlled electronically by software associated with system 100.

In operation, motor 101 provides power to input pump 102. The high pressure side of input pump 102 provides hydraulic fluid to input motor 103, which provides power to torque converter 104.

Output pump 105 absorbs mechanical energy from the torque converter 104. The high pressure side of pump 105

provides hydraulic fluid to motor 106, which assists motor 101 in driving input pump 102.

FIGURE 1 illustrates the high and low pressure lines associated with system 100 in bold. The dotted lines represent drain lines, which are typical of a hydraulic system, and carry excess fluid to reservoir 111. Various pumps, coolers, and filters that may be used at the input and output to the reservoir 111 are not shown. Various gauges and sensors 113 on the hydraulic lines deliver values representing parameters such as oil pressure and oil temperature to control system 110.

System 100 may be controlled in any suitable manner, using appropriate hardware and programming, designated as control system 110. Typically, system 100 is electronically controlled using a computer and a realtime control system that delivers operating commands and receives sensor inputs . A control loop may be used to control input and output torque of torque converter 104, based on readings from sensors 104a. Control system 110 also receives input from other sensors, such as sensors 113, and delivers control signals to the hydraulic pumps and motors .

System 100 may be used to test both transient and steady state torque and speed conditions. For example, in transient testing, system 100 may be used to simulate a wide open throttle condition, where a driver accelerates hard from a stop .