WO1997019826A1

WO1997019826A1 - Motor vehicle electrical supply system and method

Info

Publication number: WO1997019826A1
Application number: PCT/US1996/019121
Authority: WO
Inventors: Thomas J. Dougherty
Original assignee: Globe-Union, Inc.
Priority date: 1995-12-01
Filing date: 1996-11-29
Publication date: 1997-06-05
Also published as: AU1143197A

Abstract

A hybrid alternator system (10) provides supplemental electrical energy to a motor vehicle at low engine speeds. A permanent magnet motor (22) is adapted to be driven by the vehicle engine (18) and is coupled into the vehicle electrical system for supplementing the electrical output of the primary alternator (12).

Description

MOTOR VEHICLE ELECTRICAL SUPPLY SYSTEM AND METHOD

Field of the Invention

The present invention relates generally to automotive electrical systems, and more particularly, to a hybrid electrical generation system for providing electrical energy to the automobile electrical system.

Background of the Invention

Modern automobiles are equipped with a myriad of electrical equipment. Most automobiles include windshield wiper systems, electrical window defogger systems, heater, ventilation and air conditioning (HVAC) systems, interior and exterior lighting systems, in addition to engine and transmission electrical control systems. Moreover, many modern luxury automobiles include power adjustable and heated seating systems, power mirror and window systems, automatic adjusting suspension systems, and more. Automobile electrical systems are designed to include a lead-acid type electric storage battery which operates in conjunction with the alternator system.

During operation of the automobile, electrical energy is provided by the alternator system, which is driven by the internal combustion engine, to the electrical systems and to charge the battery. For example, the electrical output of a typical 100 Ampere (Amp) alternator is shown in Figure 3. At engine speeds above approximately 2500 revolutions-per-minute (RPM) the alternator produces the rated 100 Amps of electrical energy at approximately 14.4 volts. However, below

2500 RPM, the output of the alternator drops off dramatically, and at a typical engine idle speed of about 800 RPM, the alternator provides only about 35 Amps.

To provide supplemental electrical power when the alternator cannot meet the electrical demands of the vehicle electrical system, power is provided from the battery causing it to discharge. As can be appreciated, the battery discharges during low alternator output and recharges during rated alternator output. This discharge/recharge cycling of the battery, however, greatly reduces the useful life of the battery particularly when coupled with the ever increasing underhood temperatures of modern automobiles. The condition is further exacerbated in high ambient temperature regions such as found in the southwestern United States. It is possible, by providing larger capacity alternators, to increase the electrical output at lower engine speeds. However, such efforts meet the practical limitations of overly increasing the physical size and weight of the alternator when there is little available room in the engine compartment for the device and adversely increasing the initial as well as replacement cost of the device. Others have increased alternator output by increasing engine idle speed when a sensed battery voltage drops below a preset threshold. This method suffers the disadvantages of increasing vehicle emissions and reducing fuel economy at idle. Yet another approach provides first and second stage windings within an alternator to provide enhanced output at lower engine speeds. Again, this solution suffers the disadvantage of increasing physical size and weight of the alternator as well as initial and replacement cost.

As a result, the problem of discharge/recharge cycling of the battery due to low alternator output at low engine speeds persists.

Summary of the Invention

The present invention provides a hybrid alternator system having a supplemental source of electrical energy at lower engine speeds. The system includes a permanent magnet direct current (DC) motor adapted to be driven by the vehicle internal combustion engine. In a preferred embodiment of the present invention, the permanent magnet motor is mounted to the engine with its rotor shaft perpendicular to the plane of the accessory drive belt system. A pulley engages the accessory drive belt and provides driving torque to the rotor shaft for turning the rotor. The motor is electrically coupled into the vehicle electrical system for providing supplemental electrical energy to that provided by the alternator. Another aspect of the present invention provides a control system for a hybrid alternator system including an alternator and a supplemental permanent magnet motor each adapted to be driven by the intemal combustion engine. The permanent magnet motor is adapted with a clutch for selectively coupling drive torque from the internal combustion engine to the permanent magnet motor. A controller is provided and monitors the engine speed and battery parameters for providing a control signal to the clutch.

By providing a source of supplemental electrical energy smaller, lighter and less expensive primary alternators may be employed within the vehicle design. Moreover, by maintaining the battery at a higher state of charge and reducing discharge/recharge cycling, battery life may be substantially increased.

In another aspect of the present invention, the battery is eliminated from a vehicle equipped with the hybrid alternator system of the present invention. A charged capacitor is provided for providing electrical energy for starting the vehicle while the hybrid alternator system provides sufficient electrical energy to the vehicle over all engine speeds.

These and other advantages and features of the present invention will be ascertained from the following detailed description of a preferred embodiment and the accompanying drawings.

Brief Description of the Drawings

FIG. 1 generally illustrates an alternator system in accordance with a preferred embodiment of the present invention;

FIG. 2 is a flow chart illustrating a preferred control strategy associated with the alternator system; and

FIG. 3 illustrates electrical output of an alternator system in accordance with a preferred embodiment of the present invention.

Detailed Description of a Preferred Embodiment

With reference to Fig. 1 , a hybrid alternator system 10 in accordance with a preferred embodiment of the present invention includes a primary energy generation device 12, in the preferred embodiment a typical motor vehicle alternator, having an input shaft 14 and a drive pulley 16 is adapted to receive driving torque from internal combustion engine 18 via drive belt 20. Similarly a secondary energy generation device 22, in a preferred embodiment a DC permanent magnet motor, having an input shaft 24 and a drive pulley 26 is adapted to receive driving torque from internal combustion engine 18 via drive belt 20 and engine pulley 21.

Permanent magnet motor 22 may be a Geared Cobol 40 by Astro, Inc. and is adapted with an electrically actuatable clutch mechanism 28 such as a model CFC flange mounted clutch available from American Precision Industries selectively coupling and decoupling driving torque from engine 18 to motor 22.

Alternator 12 is typical and includes suitable voltage regulator circuitry (not shown), either internal or external to alternator 12, for regulating the voltage and current output of alternator 12 under normal operating conditions as is well known in the art. Electrical output of alternator 12 is coupled to the electrical load of the vehicle, schematically indicated as 30, and to electric storage battery 32. Under normal operating conditions, with internal combustion engine 19 operating in excess of approximately 1500 RPM, alternator 12 produces sufficient electrical energy to satisfy vehicle electrical load 30 as well as to provide electrical energy for charging battery 32. However, and as previously discussed, at engine speeds less than 1500 RPM the electrical output of alternator 12 drops off rapidly such that alternator 12 may produce an insufficient supply of electrical energy to satisfy vehicle load 30. In accordance with the present invention and with reference to Fig. 2, controller 34 senses two operating variables: engine RPM (step 200) and battery voltage (step 204). A RPM sensor 31 , preferably the existing RPM sensor providing RPM information to the engine controller, provides a signal indicative of engine RPM to controller 34 via signal line 36. Similarly, controller 34 senses battery voltage via signal line 38. If the engine RPM is below a threshold value, for example approximately 1500 RPM, (step 202), controller 34 checks if the battery voltage is below a preset threshold (step 206). If the battery voltage is below the threshold, for example approximately 13.1 volts, this is an indication that alternator 12 is not providing sufficient electrical energy to vehicle electrical load 30 and that battery 32 is in a state of discharge. In response, controller 34 sends a signal to clutch mechanism 28 via signal line 40 engaging clutch mechanism 28 (step 208) for transferring driving torque from engine 18 to motor 22. Otherwise, controller 34 provides a signal on signal line 40 disengaging clutch mechanism 28 (step 210) such that torque is not delivered to motor 22. it should be understood that a certain amount of hysteresis is such that the disengage signal is not sent until the battery voltage is above a threshold, for example 14.0 volts, and the engine RPM is above a threshold, for example 1750 RPM.

When driven, motor 22 produces an electrical output. An electrical output characteristic of a preferred motor 22 is illustrated in Fig. 3 as curve "M". This electrical energy, when summed with the then current output of alternator 12, produces the hybrid system electrical output illustrated in Fig. 3 as curve "Hll. Hence, it can be seen from Fig. 3 that the electrical output is greatly enhanced at low engine RPM. The additional electrical energy being made available to load 30 thereby reducing discharge/recharge cycling of battery 32. As will be appreciated, motor 22 is intended only to be driven at low engine RPM and hence is adapted for proportional rotation with engine 18 such that optimum electrical output occurs between about 500 and 1500 engine RPM. However, it is not desirable to drive motor 22 at higher engine RPM as this places unnecessary stress on motor 22 since alternator 12 is capable of providing sufficient electrical energy above 1500 engine RPM. Similarly, if battery voltage is not below the threshold at low engine RPM, i.e. vehicle load 30 is low, there is no requirement to provide supplemental electrical energy and clutch 28 remains disengaged.

Motor 12 is small and lightweight as compared to known larger capacity alternators. In addition, separating the primary and secondary electrical generation sources provide enhanced adaptability and allows for easier and more cost effective service.

The present invention has been described in terms of a preferred embodiment for a hybrid energy system having an alternator and a permanent magnet motor, one will appreciate that the permanent magnet motor may be replaced with a secondary, lower capacity alternator without departing from the scope of the present invention. In addition, because the present invention provides an electrical system capable of providing sufficient electrical energy at low engine RPM, there is no longer a need for battery 32 to provide supplemental electrical energy. Hence, battery 32 may be made smaller or eliminated altogether by providing an alternate source of starting energy to engine 18 such as a capacitance electrical energy source or in-cylinder charge ignition.

In view of the foregoing discussion of a preferred embodiment, one of ordinary skill in the art will readily appreciate the broad scope of the present invention set forth in the subjoined claims.

Claims

1. A system for providing electrical energy in a motor vehicle having an internal combustion engine, comprising: a primary energy generation device drivingly coupled for proportional rotation to the internal combustion engine for supplying electrical power to vehicle electrical loads; a secondary energy generation device selectively coupled in response to a speed of the intemal combustion engine for proportional rotation to the internal combustion engine for providing supplemental electrical power to the vehicle electrical loads.

2. The system of claim 1 wherein the secondary energy generation device comprises a permanent magnet motor.

3. The system of claim 1 wherein the secondary energy generation device includes a electrically actuatable clutch for selectively coupling and decoupling driving torque from the internal combustion engine.

4. The system of claim 3 further comprising a controller adapted to receive a signal indicative of the speed of the internal combustion engine, the controller operable for generating a control signal and wherein the eclectically actuatable clutch is responsive to the control signal for selectively coupling and decoupling driving torque from the internal combustion engine.

5. The system of claim 1 wherein the motor vehicle further comprises an electric storage battery, and wherein the secondary energy generation device is further selectively coupled in response to a battery parameter for proportional rotation to the internal combustion engine for providing supplemental electrical power to the vehicle electrical loads.

6. The system of claim 5 wherein the battery parameter comprises battery voltage.

7. The system of claim 5 wherein the primary and secondary energy generation devices provide electrical energy for charging the electric storage battery.

8. A method of providing electrical energy to a motor vehicle electrical system, the motor vehicle electrical system having a battery, the motor vehicle having an internal combustion engine and a first and a second source electrical energy adapted to be driven from the internal combustion engine, and the method comprising the steps of: engaging the first source of electrical energy at all engine speeds; sensing engine speed; engaging the second source of electrical energy when the engine speed is below an engine speed threshold.

9. The method of claim 8 further comprising the step of sensing at least one battery parameter; and the step of engaging the second source of electrical energy comprises engaging the second source of electrical energy when the battery parameter is below a battery parameter threshold.

10. The method of claim 9 wherein the step of sensing at the least one battery parameter comprises sensing battery voltage.