GB2149595A

GB2149595A - Vehicle electrical power supply

Info

Publication number: GB2149595A
Application number: GB08329911A
Authority: GB
Inventors: Geoffery Frederick Berry
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1983-11-09
Filing date: 1983-11-09
Publication date: 1985-06-12
Also published as: GB8329911D0

Abstract

The power supply comprises an alternator having a stator 10 with first and second mutually isolated single phase windings 14, 16. The first winding 14 supplies alternating current to the A.C. or resistive loads 24 of the vehicle. The second winding 16 is connected to a rectifier 26 and voltage regulator 32 circuit to provide a DC supply for the ignition loads 34, other DC loads 35 being supplied from the winding 16 via a rectifier 28 which also changes the battery 36. The system reduces rectifier losses and improves fuel economy. In an "ON" position of an ignition switch 22, 40 the battery 36 is connected to the ignition circuits 34 for engine start up; in an "ACCESSORY" position of the ignition switch the A.C. loads 24 are connected to the battery 36, and esential A.C. loads such as side lights, may also be energised from the battery 36 in the "OFF" position of the ignition switch. <IMAGE>

Description

SPECIFICATION Vehicle electrical power supply This invention relates to vehicle electrical systems and in particular to a new electrical power supply system of improved efficiency.

Increases in the price of fossil fuels and concerns as to the limited natural resources of such fuels have led to a demand for more fuel efficient motor vehicles. Vehicle electrical systems have become more complex and comprehensive and use a significant percentage of the power developed by the vehicle engine. Useful improvements in fuel economy can be made by improving the efficiency of conversion of power output from the engine into electrical energy suitable for operating the vehicle electrical equipment.

The conventional vehicle electrical supply system comprises a three phase alternator, a bridge rectifier and a voltage regulator. This supplies all vehicle loads, except when the engine is inoperative.

Essential electrical systems, required when the engine is stopped, are connected to a battery which is recharged from the alternator when the engine is running.

According to a first aspect of the invention, there is provided an electrical power supply system for a vehicle comprising an alternator having two separate stator windings, the first stator winding being connected to an alternating current output %3 and a rectifier and voltage regulator circuit connected to the second stator winding to provide a supply of direct current at a direct current output.

Preferably the alternator is a single phase alternator. According to a second aspect of the invention, there is provided a vehicle electrical system having an alternating current supply and a direct current supply from a common alternator, the direct current supply being connected to the direct current loads of the vehicle and the alternating current supply being connected to the resistive loads.

The improvement in efficiency compared to the conventional vehicle electrical system devised above arises partly from the reduced losses in the rectifier circuit, since only about half the current consumed at peak loadings has to pass through the rectifier, and partly from the improved efficiency of a single phase alternator as compared with a three phase alternator.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which Figure 1 is a schematic diagram of a vehicle electrical power supply system embodying the present invention; and Figure 2 is a circuit diagram of a vehicle electrical system using the power supply system shown in Figure 1.

Referring to Figure 1, an alternator has a single phase stator shown schematically at 10. The stator has twelve poles 12 compared to the 36 poles found in many currently used vehicle alternators. A first stator winding 14 and a second stator winding 16, mutually insulated, are wound on all twelve poles.

The first stator winding 14 (shown only by dotted lines on the poles at the extreme left hand and right hand sides of Figure 1) is connected at one end 18 to earth and at the other end 20 to the vehicle ignition switch 22. When the ignition switch 22 is in its "on" position the first stator winding is connected to the vehicle resistive, or AC, loads 24 and supplies alternating current to those loads when the alternator is rotated by the vehicle engine.

The second stator winding is connected across two bridge rectifiers 26 and 28 having a common earth side 30. The first rectifier 26 is connected to a conventional voltage regulator 32 and to the vehicle ignition loads 34.

The unregulated direct current output from the second rectifier 28 is connected directly to the positive terminal of a 12 volt battery 36. The negative terminal of the battery is connected to earth.

The positive terminal of the battery 36 is also connected to the direct current loads 38 of the vehicle and to a second pole 40 of the ignition switch 22.

When the ignition switch is in its "off" position, shown in Figure 1, the ignition circuits are insulated from the battery so that the vehicle engine cannot run, the DC loads are connected to the battery, but the AC loads are isolated. Provision, not shown, may be made for energising essential AC loads such as side lights from the battery when the ignition switch is in its "off" position.

Movement of the ignition switch to its "on" position (anti-clockwise rotation in Figure 1), connects the battery to the ignition circuits for engine start up. As soon as the engine is running and the alternator rotating, the AC loads are energised from the first stator winding and direct current from the rectifier supplies the DC loads and re-charges the battery.

An accessory position of the ignition switch is also provided (clockwise rotation in Figure 1), in which the ignition circuits 34 are isolated so that the engine cannot run but the AC loads 24 are connected to the battery through line 42.

Figure 2 shows how the electrical equipment of the vehicle is grouped into AC loads connected to the AC output 20 and DC loads connected to the DC output 44.

The ignition circuit has its own on/off switch 22 and the other loads also have their respective control switches.

The ignition circuit 34 requires about 45 watts, the heater motor 46 about 190 watts, the windscreen wiper motor 40 about 80 watts, the rear wiper motor 50 about 40 watts, and the instruments and gauges 52 about 6 watts making a maximum of 355 watts consumed by the DC loads.

The AC loads include instrument and interior illumination ST requiring about 30 watts, the tailgate heater 56 requiring about 175 watts, and the exterior lamps 58 requiring about 150 watts. Thus the maximum power consumed by the AC loads is about 361 watts.

In the embodiment described about half the maximum electrical energy requirements are supplied from the AC supply making for a useful improvement in efficiency, mainly due to the reduction of rectifier losses.

Claims

1. An electrical power supply system for a vehicle comprising a) an alternator having two separate stator windings, the first stator winding being connected to an alternating current output; and b) a rectifier and voltage regulator circuit connected to the second winding to provide a supply of direct current at a direct current output.

2. A power supply system substantially as herinbefore described with reference to and as illustrated in the accompanying drawings.

3. A motor vehicle electrical system comprising a power supply system as claimed in Claim 1 or Claim 2, a plurality of direct current loads connected to the direct current supply and a plurality of resistive loads connected to the alternating current output.

4. A motor vehicle electrical system as claimed in Claim 3 including a battery connected to the direct current supply for providing a source of direct current when the alternator is not driven.

5. A motor vehicle electrical system as claimed in Claim 4, including an ignition switch having an "off" position, an "on" position in which it connects the resitive loads to the alternating current output, and an "accessory" position in which it connects at least some of the resisitive loads to the battery to enable energisation of those loads when the alternator is not driven.

6. A vehicle electrical system having an alternating current supply and a direct current supply from a common alternator, the direct current supply being connected to the direct current loads of the vehicle and the alternating current supply being connected to the resistive loads.

7. A motor vehicle electrical system substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.