GB2239704A

GB2239704A - Power absorption device

Info

Publication number: GB2239704A
Application number: GB9000281A
Authority: GB
Inventors: Thomas Tsoi-Hei Ma
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1990-01-05
Filing date: 1990-01-05
Publication date: 1991-07-10
Also published as: GB9000281D0

Abstract

A power absorption device for mounting in the coolant circuit of an engine to generate heat for directly increasing the temperature of the engine coolant during warm-up comprises a rotor 32 and a stator 34 operative to convert power into heat when rotated relative to one another and arranged in a common housing 10 which sealingly engages an opening in the engine coolant circuit. The rotor 32 is fixedly mounted on a shaft 16 which is driven from the engine crankshaft and the stator 34 is associated with a brake band 38 for preventing the stator 34 from turning when engine power is to be absorbed, the rotor and stator rotating in unison when the brake band 38 are released. The power absorption device may be mounted in the same housing as the coolant pump 18 and shares the same drive train. <IMAGE>

Description

Power Absorption Device The present invention relates to fast warm up of engines.

It is well recognised that is desirable to bring an engine up to its operating temperature as rapidly as possible.

There are a variety of reasons for this including reducing overall fuel consumption and emissions, and improving passenger comfort and drivability.

Prior art suggestions for improving warm-up times have included storing heat from previous operation, exhaust gas heat exchangers and placing power absorption devices in the coolant circuit. The present invention adopts the last of these approaches.

In prior art proposals, the power absorption device is located outside the engine and has its own drive train which includes an electro-magnetic clutch capable of transmitting sufficient force to drive the energy absorption device. During warm-up, the clutch is engaged and the heat generated by the power absorption device is used to heat the coolant. Increased load is applied to the engine, which increases heating of the coolant and produces hotter exhaust gases to reduce the time taken by a catalytic converter to reach its light off temperature.

A disadvantage of the prior art is that complexity is introduced by the need for a clutch which requires an electrical control system and has friction plates which are prone to wear. If a power absorption device capable of dissipating several kilowatts of power is to be employed, then a substantial electromagnetic clutch is required, especially so if it is to be capable of rapid engagement and disengagement without severe wear to the clutch plates. Heat dissipated by energising the clutch would not in this case find its way to the coolant and would merely be a cause of increased fuel consumption.

In accordance with the present invention, there is provided a power absorption device for mounting in the coolant circuit of an engine to generate heat for directly increasing the temperature of the engine coolant, comprising a rotor and a stator operative to convert power into heat when rotated relative to one another and arranged in a common housing which in use sealingly engages an opening in the engine coolant circuit, wherein the rotor is fixedly mounted on a shaft which in use is driven from the engine crankshaft and the stator is associated with braking means for preventing the stator from turning when engine power is to be absorbed, the rotor and stator rotating in unison when the brake means are released.

Serious disadvantages of the prior art proposal lie in its cost and difficulty in packaging. Packaging is a problem because a suitable location must be found for the device where it can be driven by one of the belts connected to the crankshaft and cost is increased by the need for an additional pulley, housing and piping.

According to a preferred embodiment of the invention, the power absorption device is combined with the coolant pump and is mounted within a common housing.

In this way, the power absorption device can be driven by the same pulley as drives the coolant pump and the common housing avoids the need for a separate housing for the power absorption device. Furthermore, as the device is now already located within the coolant circuit, the need for any additional piping is avoided making for a less expensive construction and a more efficient thermal transfer.

In the prior art, when the electromagnetic clutch is not engaged, the rotor is not driven and both the rotor and the stator remain stationary. Such a device cannot of course be combined with a coolant pump which must be driven under all circumstances. By contrast, in the present invention the rotor is permanently driven but the stator is either braked when power is to be absorbed or allowed to rotate at the same speed as the rotor, by releasing the brake, when no power is to be absorbed. It is this feature that the rotor is constantly driven which enables the power absorption device of the present invention to be combined with existing driven equipment, such as the coolant pump.

The invention will now be described further, by way of example, with reference to the accompanying drawing which is a section through a combined coolant pump and power absorption device.

The illustrated combined coolant pump and power absorption device is designed as a direct replacement for a conventional coolant pump and many of the components are common to such a pump. In particular, the device includes a housing 10 to be bolted onto an engine block 12 and having a bearing 14 for a shaft 16 which carries an impeller 18. A cup shaped pulley 20 is secured to an end of the shaft projecting from'the housing 10. The housing 10 defines a coolant chamber 22 which forms part of the coolant circuit and from which coolant is pumped by the impeller 18 into the engine block when the shaft 16 is turned by the pulley 20, itself engaged by a crankshaft driven V-belt 24. A gland 26 seals the coolant chamber 22 around the shaft 16 and prevents coolant from escaping or reaching the bearing 14.

As so far described, the device resembles a conventional coolant pump, the main difference residing in the fact the the housing 10 is somewhat longer than a conventional coolant pump housing and is formed in two part 10a and lOb to permit assembly of the power absorption device which will be described below. Of course, because of the elongation of the coolant pump housing, the cup shaped pulley has also been extended to allow it to be driven by the V-belt 24.

The power absorption device 30 consists of a turbine fluid coupling, as found for example in a the torque converter of an automatic transmission. The coupling has a rotor 32 which is fast in rotation with the shaft 16 and a stator 34 which is free to rotate relative to the shaft 16 being mounted on a bearing 36 fitted to the shaft 16. However, because of the fluid coupling between the rotor 32 and the stator 34 the latter will experience a significant drag tending to make it rotate with the rotor 32. If the stator 34 is allowed to move with the rotor 32, no power is absorbed from the engine by the fluid coupling.

Surrounding the stator 34 is a brake band 38 operable by a calliper mechanism 40 which can be externally actuated by a lever 42. The lever is secured to a shaft 44 which passes through and is sealed relative to the housing 10.

When the lever 42 is pivoted by the application of an external force, the callipers 40 are drawn together and pull the brake band 38 about the periphery of the stator 34 to prevent the latter from turning with the rotor 32.

Brake bands are of course also well known from automatic transmissions and their construction and operation need not therefore be described in detail in the present context. It suffices to appreciate that the force required to actuate the brake is far less that the resulting braking force applied because of the self tightening nature of a brake band. The lever 42 does not therefore require a large force to move it from its rest position to an actuated position and this force can be applied by a relatively weak electro-magnet.

When the brake band 38 prevents the stator 34 from turning, energy imparted to the coolant by the rotor 32 is converted to heat instead of kinetic energy, and it is possible by the use of a fluid coupling of modest dimensions to achieve a heating effect equivalent to a 5 to 10 kilowatt electric heater. Consequently, the coolant temperature can be raised very rapidly.

Furthermore, the application of a brake requires the engine output power to be increased and this in turn increases the heat rejection from the engine which assists further in reducing warm up time.

The reduction in warm up time improves passenger comfort and fuel consumption (because fuel enrichment is required for a shorter time) but its most important advantage is in the reduction of emission of noxious gases by enabling sooner operation of the catalytic converter.

It will be appreciated that various modification can be made without departing from the scope of the invention as set forth in the appended claims. For example, the rotor and stator need not form part of a fluid converter but may consist of a friction clutch of which the plates are permanently engaged under the action of a spring.

Furthermore, the combined coolant pump and power absorption device need not be mounted directly on the engine block but may, as in some engines, be mounted to one side and connected by conduits in the engine coolant circuit. It will also be clear that the braking means need not necessarily be in the form of a brake band.

Claims

1. A power absorption device for mounting in the coolant circuit of an engine to generate heat for directly increasing the temperature of the engine coolant, comprising a rotor and a stator operative to convert power into heat when rotated relative to one another and arranged in a common housing which in use sealingly engages an opening in the engine coolant circuit, wherein the rotor is fixedly mounted on a shaft which in use is driven from the engine crankshaft and the stator is associated with braking means for preventing the stator from turning when engine power is to be absorbed, the rotor and stator rotating in unison when the brake means are released.

2. A power absorption as claimed in Claim 1, in combination with a coolant pump, the power absorption device and the coolant pump being mounted in the same housing and sharing a common drive train.

3. A power absorption device as claimed in claim 1 or 2, wherein the housing of the device is sealingly engageable with an opening in the engine block.

4. A power absorption device as claimed in any preceding claim, wherein the rotor and the stator together form a fluid coupling.

5. A power absorption device as claimed in any preceding claim, wherein the braking means comprises a calliper operated brake band surrounding the stator and disposed within said common housing.

6. A power absorption device constructed, arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawing.