ELECTRONIC CONTROL FOR A HYDRAULICALLY DRIVEN GENERATOR

• US 20090134848A1
• Filed: 11/26/2008
• Published: 05/28/2009
• Est. Priority Date: 01/17/2006
• Status: Active Grant

• Current Assignee: Uusi LLC (Nartron Corporation)
• Original Assignee: Nartron Corporation
• Inventors: Washeleski, John M., Boisvert, Mario P., Kienitz, Thomas
• Granted Patent: US 7,759,811 B2
• Time in Patent Office: Days
• US Class Current: 322/38
• CPC Class Codes: F15B 21/08 Servomotor systems incorporating electrically operated control means F15B21/02, F15B21/065 take precedence
• CPC Class Codes: F15B 2211/20523 Internal combustion engine
• CPC Class Codes: F15B 2211/20538 constant capacity
• CPC Class Codes: F15B 2211/40515 with variable throttles or orifices
• CPC Class Codes: F15B 2211/413 the positions being continuously variable, e.g. as realised by proportional valves
• CPC Class Codes: F15B 2211/427 with signal modulation, e.g. using pulse width modulation [PWM]
• CPC Class Codes: F15B 2211/45 Control of bleed-off flow, e.g. control of bypass flow to the return line
• CPC Class Codes: F15B 2211/6333 representing a state of the pressure source, e.g. swash plate angle
• CPC Class Codes: F15B 2211/6336 representing a state of the output member, e.g. position, speed or acceleration
• CPC Class Codes: F15B 2211/6343 representing a temperature
• CPC Class Codes: F15B 2211/6656 Closed loop control, i.e. control using feedback
• CPC Class Codes: F15B 2211/7058 Rotary output members
• CPC Class Codes: F15B 7/008 with rotary output
• CPC Class Codes: F16H 61/4035 Control of circuit flow
• CPC Class Codes: F16H 61/4043 Control of a bypass valve
• CPC Class Codes: F16H 61/431 Pump capacity control by electro-hydraulic control means, e.g. using solenoid valves
• CPC Class Codes: F16H 61/46 Automatic regulation in accordance with output requirements
• CPC Class Codes: F16H 61/47 for achieving a target output speed
• CPC Class Codes: H02P 2101/30 for aircraft
• CPC Class Codes: H02P 9/009 Circuit arrangements for detecting rotor position
• CPC Class Codes: H02P 9/48 : Arrangements for obtaining a constant output value at varying speed of the generator, e.g. on vehicle H02P9/04 - H02P9/46 take precedence

Abstract

Hydraulic system for driving an auxiliary power source is provided, which is specifically adapted for use with a system for controlling hydraulically driven AC generator. The system includes a hydraulic pump and hydraulic motor that are connected by a fluid circuit. The hydraulic motor drivably connected to an AC generator and is operated in a manner to generate a stable AC power output. The system may include a valve which bypasses fluid around the motor or a variable displacement pump so that the fluid flow rate through the hydraulic motor is controlled in a manner to maintain the desired AC generator output level. Sensors are further provided measuring operating parameters of the system so that the controller can maintain desired operating condition limits

Claims

1. A hydraulic system for driving an auxiliary power source, located aboard a motor vehicle having a primary power source, at a substantially constant speed despite fluctuations in rotational speed of the primary power source, the system comprising:

a variable displacement hydraulic pump drivably connectable to the primary power source, the hydraulic pump having an inlet for receiving fluid, an outlet for discharging fluid under pressure and a pump displacement input;

a hydraulic motor drivably connectable to an auxiliary power source, the hydraulic motor having an inlet for receiving fluid under pressure and an outlet for discharging fluid;

a fluid circuit including a supply conduit for conducting fluid discharged by the pump to the motor, a return conduit for returning fluid discharged by the motor to the pump;

a pump displacement control cooperating with the pump displacement input in order to vary the displacement of the pump; and

a control circuit in communication with the pump displacement control for controlling the pump output so that a desired hydraulic motor and associated auxiliary power source speed can be maintained.

2. The system of claim 1, wherein the control circuit further comprises:

an electrical output sensor electrically coupled to the auxiliary power source for determining output frequency of the auxiliary power source; and

a reference signal generator for generating a reference signal indicative of a desired output frequency wherein the control circuit compares the sensed output frequency and/or voltage with the referenced signal to vary the pump displacement so that the supply of fluid to the motor is sufficient to maintain the desired output frequency and/or voltage.

3. The system of claim 1 wherein the control circuit further comprises:

a speed sensor for determining rotational speed of the hydraulic motor; and

a reference signal generator for generating a reference signal indicative of a desired hydraulic motor speed, wherein the control circuit compares sensed rotational speed of the motor with the reference signal to generate an output signal to the pump displacement control so that the supply of fluid to the motor is sufficient to maintain the desired rotational speed of the motor and associated auxiliary power source.

4. The system according to claim 1, wherein the control circuit further comprises a temperature sensor disposed in the fluid circuit for sensing hydraulic fluid temperature wherein the control circuit limits the pump displacement to limit pump output hydraulic motor until a desired safe fluid temperature is obtained.

5. The system according to claim 4, wherein the control circuit ramps up the speed of the motor as a function of fluid temperature on system startup.

6. The system of claim 4, wherein the control circuit further provides an overtemperature shutdown to restrict pump output in order to shut down the motor and associated auxiliary power source when the fluid temperature becomes too hot for safe operation.

7. The system of claim 6, wherein the control circuit further comprises:

an emergency override accessible by the operator to continue system operation in spite of an overtemperature condition.

8. The system of claim 1 further comprising:

a control valve interposed in the fluid circuit between the variable displacement pump and the hydraulic motor, the control valve having an outlet in communication with the hydraulic motor and a bypass outlet in communication with the fluid circuit downstream of the hydraulic motor;

wherein the control circuit communications with the control valve to bypass fluid around the hydraulic motor in order to further limit the rotation of the hydraulic motor.

9. The system of claim 1 wherein the pump displacement control is hydraulically powered and has a mechanical output cooperating with the variable displacement pump.

10. The system of claim 1 further comprising an AC generator providing an auxiliary power source operatively driven by the hydraulic motor.

11. The system of claim 10 further comprising:

a modular frame adapted to be affixed to the exterior of a motor vehicle;

wherein the hydraulic motor and the AC generator which is driven thereby is mounted to the modular frame.

12. The method for operating a hydraulic system for driving auxiliary power source located aboard a motor vehicle having a primary power source driving a pump which in turn drives a hydraulic motor coupled to the auxiliary power source and a control circuit for controlling the flow of hydraulic fluid in a motor enabling the auxiliary power source to be maintained at a desired rotational speed independent of primary power source speed fluctuations, the method comprising:

sensing the hydraulic fluid temperature in the fluid circuit;

when the hydraulic fluid is below a desired operating temperature minimizing the pump displacement and in turn minimizing pump output to gradually warm the hydraulic fluid by circulating fluid internally within the hydraulic pump while limiting flow to the hydraulic motor; and

gradually increasing the pump displacement and the hydraulic pump fluid output which is supplied to the hydraulic motor as a function of hydraulic fluid temperature in order to gradually increase the speed and temperature of the hydraulic motor.