GB2031822A - A method and apparatus for driving a load, such as a vehicle - Google Patents

Abstract

The apparatus includes a prime mover such as engine (10), a transmission unit (20), preferably infinitely variable, and a flywheel (16). During deceleration of the vehicle, the fuel supply to the engine is substantially reduced or cut off, and the flywheel is used to store energy. To enable continued operation of ancillaries when the engine is not operating, the flywheel is used to power the ancillaries. In one embodiment the flywheel is used to turn the engine over at low speeds to keep ancillaries functioning. Alternatively, the flywheel may be completely disconnected from the engine and drive the ancillaries directly. When the flywheel energy has been dissipated to a certain level, the engine is restarted. The flywheel is coupled to the engine by means of a clutch (14) permitting total or partial disengagement as required. <IMAGE>

Description

SPECIFICATION Method and apparatus for driving a load The invention relates to a method of operating apparatus for driving a load such as a motor vehicle, and to such apparatus.

In general a motor vehicle will be powered by a prime mover such as a petrol or diesel engine. As a result of the current emphasis on fuel conservation, it is a well publicised fact that the fuel consumption of a motor vehicle under city driving conditions is considerably higher than that under highway conditions. The reasons for this are well known and primarily the result of energy losses in decelerating and stopping a vehicle in city traffic, with kinetic energy being dissipated in braking, idling operation of the engine while the vehicle is stopped, and operation for a large percentage of the distance travelled at engine speeds which are above speeds at which engine efficiency is optimum.

Hybrid power systems are known by which the fuel consumption of an automobile engine, particularly under city driving conditions, can be decreased substantially by storing in a flywheel, for example, energy made available during deceleration of the vehicle. The stored energy can be used as an ancillary source of power when required, to reduce power demands on the engine, i.e. the prime mover. Such systems also enable excess power generated by the engine, when operated at a power level giving improved efficiency but greater than that required for driving the load, to be diverted to the flywheel for subsequent use. Moreover, the fuel consuming engine of the system may be shut off when the vehicle is stopped and the flywheel stored energy used both to accelerate the vehicle initially from rest and to restart the engine.

Stopping an engine when a vehicle is decelerating or stopped in traffic causes certain problems, since engine driven ancillaries will cease to operate. This could affect important functions such as power steering, power brakes and so forth.

Viewed from one aspect, the invention provides a method of operating apparatus for driving a movable load, such apparatus including a prime mover, means for supplying fuel to the prime mover, means for transmitting power from the prime mover to the load and to at least one ancillary, and means for storing energy; the method comprising the steps of storing energy made available by the load during deceleration thereof; terminating fuelled operation of the prime moved during periods of deceleration or rest of said load; transmitting power from said energy storing means to said ancillary during periods when fuelled operation of the prime mover is terminated; and recommencing fuelled operation of the prime mover when the energy stored by said storing means has been reduced to a predetermined value.

Preferably the storing means stores kinetic energy, and is desirably in the form of a flywheel.

It has been found that substantial reductions in fuel consumption and emission of air pollutants under city driving conditions can be realised with a system using a relatively simple flywheel represented, for example, by a carbon steel disc a few centimetres in thickness and between 40 and 50 centimetres in diameter. A flywheel of this type provides a kinetic energy storage capacity adequate not only to propel a conventional automobile for limited periods of time, but also to supply the power to drive ancillaries such as power brakes, power steering, air conditioning and so forth, whilst the fuel consuming prime mover is not operating.

During power generating operation of the prime mover, the flywheel will be coupled with the prime mover, for example being linked to the crank shaft of a conventional petrol engine. During load deceleration or rest, the prime mover may be completely shut off, for example by interrupting the fuel supply. In this case the flywheel will be uncoupled from the stationary prime mover, and may drive ancillaries directly. Complete engine shutdown, however, may create problems in certain circumstances. Repeated stopping and starting an engine can materially reduce the life of various engine components, particularly bearings and other lubricated surfaces which build and retain a film of lubrication only when kept in motion. In other words, relative movement of bearing surfaces, in itself, is important to retention of a hydrodynamic lubricating film of the bearing surfaces.

Thus, the flywheel may be only partially disengaged from the prime mover, and used to turn the prime mover at low speeds. The fuel supply may be completely interrupted, or merely reduced to below that necessary to maintain unassisted fueled engine idling. The speed at which the prime mover is turned, i.e. the cranking speed, should be chosen so that friction losses etc.

are minimised, and will generally be less than the normal idling speed.

Such low speed cranking of the prime mover serves to maintain continuity of engine driven ancillaries, such as the oil pump, generator and so forth, with little or no fuel consumption.

Preferably, an infinitely variable transmission is employed to inter-relate the speeds of the flywheel, the prime mover, and the load represented by an automobile drive shaft for example.

Such transmissions have been developed to a state where power in excess of that developed in automobile engines can be transmitted at high efficiencies through infinitely variable input/output speed ratios in a wide range extending to zero. Reference is made for example to United States Patent Application 706,291.

To accommodate highway driving conditions, the power train of an automobile should preferably be adaptable to a direct drive connection of the prime mover, i.e. engine, and the load, i.e. drive wheels. It has been proposed in previous systems to de-clutch an energy storing flywheel from a drive train under highway driving conditions. Reference is made to Scott, David, "Flywheel Transmission Has Variable-Speed Gear", Automotive Engineering, March 1977, 85:3 pages 18-19, or to United States Patent 3,672,244. Alternatively it has been proposed to shunt entirely the flywheel and infinitely variable transmission components of the system for transmission of power directly to load. Reference is made to United States Patent 3,870,116.

Such power train requirements have been complex in terms of required controls and component organization, space consuming by comparison to conventional automobile power trains and potentially an additional source of mechanical failure over and above that which already exists in a conventional power train.

In a preferred embodiment of the present invention, the power train uses a flywheel which is the approximate equivalent of a conventional crankshaft flywheel, and an infinitely variable transmission permitting optimum engine power generating speeds for low and moderate vehicle speeds while at the same time permitting a direct engine-drive wheel connection during a mode of operation represented by an automobile operating under highway driving conditions. The flywheel is keyed or otherwise linked for rotation at all times with the input of the infinitely variable transmission, and releasably coupled by a clutch, for example, directly to the crankshaft or equivalent power shaft of the prime mover. In other words the position of the clutch is a reversal of the flywheel-clutch connection to the crankshaft of a conventional automobile drive train.The flywheel functions both as a crankshaft flywheel and as a kinetic energy storage flywheel.

The output of the infinitely variable transmission is coupled with the load propelling shaft through a simple gear box adjustable to provide "forward", "reverse" and "neutral" operating modes as well as to provide a direct connection of the propelling shaft with the input of the infinitely variable transmission. When the load propelling shaft is coupled with the input of the transmission, power transmitting efficiency losses in the transmission can be avoided.

Viewed from another aspect the invention provides apparatus for driving a movable load, comprising a prime mover; means for supplying fuel to the prime mover; means for transmitting power from the prime mover to the load and to at least one ancillary; means arranged to store energy made available during deceleration of the load; means arranged to terminate fuelled operation of the prime mover during periods of deceleration or rest of said load; means arranged to transmit power from said energy storing means to said ancillary during periods when fuelled operation of the prime mover is terminated; and means arranged to restart fuelled operation of the prime mover when the energy stored by said storing means is reduced to a predetermined level.

Viewed from a still further aspect the invention provides apparatus for driving an inertial load, comprising a prime mover having an output shaft, a fuel supply and means for controlling the supply of fuel to the prime mover to vary the speed thereof and to reduce the supply to a level below that necessary for maintaining unassisted operation of the prime mover; a variable speed transmission having an input shaft and an output shaft; means for transmitting power from the transmission output shaft to the load; a flywheel connected for rotation directly with said transmission input shaft; and means for selectively coupling said flywheel and said prime mover output shaft to enable the transmission of full torque or less than full torque therebetween.

The flywheel can be adapted to drive an ancillary when the supply of fuel to the engine is reduced to the level below that necessary for maintaining unassisted operation of the prime mover.

Thus, during normal powered operation, the coupling means will transmit full torque from the prime mover, the flywheel acting to maintain the inertia of prime mover operation. During deceleration, the coupling means will transmit less than full torque, and the flywheel will store energy released during such deceleration of the load. The flywheel may drive the ancillary directly, if desired no torque being transmitted between the flywheel and prime mover.

Alternatively, the flywheel may be coupled to some extent to the prime mover, to turn the output shaft at low speed and drive the ancillary indirectly. If desired, energy stored by the flywheel during deceleration of the load, could be used to augment the power developed by the prime mover, or to restart the prime mover. Ancillaries may or may not be driven when the prime mover is shut off, as desired.

Some embodiments of the invention will now be described by way of example, and with reference to the accompanying drawings, in which: Figure 1 is a schematic view illustrating various mechanical components of a hybrid power system in accordance with the present invention in relation to sensing and control functions represented in block diagram form; Figures 2a and 2b are segmented longitudinal cross-sections through a preferred embodiment of power train assembly to be incorporated in the system; Figure 3 is a schematic cross-section illustrating the coaction of gearing embodied in the transmission unit shown in Fig. 2; Figure 4 is a set of graphs in which quantitative values of various parameters are plotted on ordinates against a common abscissa; Figure 5 is a schematic illustration of components in a modified embodiment of the invention; and Figure 6 is a similar schematic illustration of another modified embodiment of the invention.

In Fig. 1 of the drawings, the functioning components of a hybrid power system are shown schematically to facilitate an understanding of interrelated working and control components as well as overall system operation. Thus, in Fig. 1, a prime mover is designated generally by the reference numeral 10 and shown to include a power shaft 1 2 releasably connected by a friction clutch 14 to a flywheel 1 6 rotatable with and, in this instance, carried by the input shaft 1 8 of a variable speed transmission unit 20 preferably of a type known in the art as an infinitely variable or l.V. transmission unit.The variable speed output of the transmission unit 18, represented by a shaft 22, is connected through a mode control unit 24 to a load propelling shaft 26 coupled by conventional differential gearing (not shown) to the drive wheels 28 of a vehicle to be propelled by the system. As will be described in more detail below, the transmission unit 20 additionally includes a direct drive shaft 30 represented by phantom lines in Fig. 1 extending from the input shaft 1 8 to the mode control unit 24. Also to be understood more clearly from the description to follow, the clutch 14, flywheel 16, transmission unit 20 and mode control unit 24 are components of a power train assembly 32 represented in Fig. 1 by the dashed line rectangle circumscribing these components.

It is also to be noted that although the hybrid power system both represented by the schematic illustration in Fig. 1 and to be described in more detail hereinafter is depicted as a vehicular power system in which system load is represented by the drive wheels 28 of a powered vehicle, the system is equally applicable to other inertial loads or loads which require power for acceleration and which dissipate kinetic energy during deceleration. Similarly, while the prime mover 10 is represented in Fig. 1 as a carbureted spark ignition piston engine, other forms of prime movers may be used and may be preferred from the standpoint of achieving optimized system operation.Apparatus in accordance with the invention has particular utility with fuel injected spark ignition engines, diesel engines, Stirling engines and other prime movers which operate to convert a succession of discrete power impulses to continuous rotary output or power shaft motion. It will be noted in this respect, therefore, that the engine 10 includes a crank shaft 34 and that the power or output shaft 1 2 is a direct extension of the crank shaft. More importantly, the organization of the crank shaft 34 and the power shaft 1 2 is devoid of the conventional crank shaft flywheel or other added inertial components by which continuity and smoothness of rotation in the power shaft 1 2 will be maintained without an auxiliary supply of kinetic energy.

Irrespective of the particular type of engine used as the prime mover 10, it will have a supply of potential energy represented by a fuel supply 36 from which fuel may be fed or directed to the prime mover under the control of the throttle 38, for example, in normal operation at speeds varying from idling speeds with the throttle substantially closed to maximum speeds with the throttle wide-open. In accordance with the present invention, the supply of potential energy or fuel is additionally regulated for complete shutoff or for reduction to supply levels less than that needed for prime mover operation using only potential energy or fuel.In the embodiment represented schematically in Fig. 1, a valve 40 is provided in the line between a fuel supply and the prime mover upstream from the control represented by the throttle 38 so that the supply of fuel to the prime mover 10 may be cut off by closing the valve 40 or reduced to a level less that the lowest throttle setting. It is to be noted that in some engines, such as an internal combustion engine eqipped with an electronic fuel injection system, for example, the function of the valve 40 may be served by the same device used to regulate the supply of fuel to the engine for controlling the power developed by the engine. In fact, fuel injection systems are preferred due to increased precision of fuel feed and the closed proximity of fuel flow regulation to combustion or working chambers by comparison to carbureted fuel feeds.Hence, the throttle 38 and the valve 40 is merely representative of a particular means for reducing or shutting off the fuel supply 36 at the speed controlling throttle. Additionally, an ignition switch 42 will be provided in the case of a spark ignition engine or the equivalent of such an ignition switch provided for the purpose of enabling or disabling operation of the engine.

The working components thus described generally with reference to Fig. 1 are operated by a control system illustrated in block diagram form to include an electronic computer 44 for processing driver and system inputs to develop appropriate control signal outputs. Specifically, driver inputs include a power switch 46, a direction control 48, an accelerator 50 and a brake pedal 52. System functions which are monitored include engine speed, +, flywheel and transmission input speed å and variable transmission output speed (), the operating mode of the unit 24 and the reaction torque of the transmission 29.Adjustable parameters to be controlled by the computer 44 include the ignition switch 42, the engine throttle 38 or other control of engine speed, the clutch 14, the speed ratio of the l.V. transmission 20, and the mode control unit 24. Although the details of the control system are not shown beyond the block diagram representation of Fig. 1, such computerized systems are well known and within the skill of one familiar with computer logic circuitry, given the desired operational characteristics to be accomplished.

The structure of the power train assembly 32 is illustrated most clearly in Figs. 2a and 2b of the drawings. The components of the assembly are housed within a single frame or casing 54 having a flared front portion 56 adapted to be bolted or otherwise fixed to the engine 10 in essentially the same manner as a conventional automotive transmission. This portion of the casing 54 contains the flywheel 1 6 and the clutch 14. The central portion of the casing houses and serves as a frame component of the l.V. transmission unit 20 whereas an end bell casing component 58 houses the mode control unit 24 and is secured to the central portion of the casing 54 such as by bolts 60.

As shown in Fig. 2a, the end of the power shaft 1 2 is conventionally flanged to mount a clutch disc hub 62 in turn splined to receive an axially movable, lightweight clutch disc 64. The disc 64 extends outwardly to be positioned between an axially fixed abutment ring 66 and an axially adjustable pressure pad ring 68, both carried directly by the flywheel 1 6. The adjustable pad 68 is urged by a series of compression springs 69 into engagement with the disc 64 and abutment 66, thereby to couple the disc 64 and thus the shaft 1 2 with the flywheel 1 6. The adjustable pad 68 is supported by rods 70 extending to an annular piston 72, movable in an annular chamber 74 again provided in the flywheel 1 6. Fluid under pressure at a passage way 76 will operate to retract the pad 68 against the bias of the compression springs 69.

In light of the foregoing, it will be appreciated that the clutch 14 is in the nature of a conventional friction clutch which may be adapted to fully couple the shaft 1 2 with the flywheel 16 in the absence of fluid pressure acting to move the annular piston against the bias of the springs 69. The shaft 1 2 will be completely decoupled from the flywheel 1 6 when pressure acting against the annular piston 72 retracts the pad 68 away from the disc 64. Further, appropriate adjustment of fluid pressure acting against the annular piston 72 may effect a range of intermediate coupling conditions in the clutch 14 under which a limited torque may be transmitted between the shaft 12 and the flywheel 1 6 irrespective of the relative speeds of these members.Also as may be seen in Fig. 2a, the flywheel is separated in rotation from the shaft 1 2 and the hub 62 by roller bearings 78 and is splined or otherwise coupled for rotation directly with the input shaft 18 of the l.V. transmission unit 20.

As will be appreciated from the ensuing description, the precise form of the transmission unit 20 as well as the mode control unit 24 may vary considerably from that illustrated in Figs. 2a and 2b of the drawings. The transmission unit 20 however, is preferably of a type disclosed in United States Patent Application Ser. No. 706,291. As such, the transmission structure includes as a frame, the central portion of the casing 54 and a pair of transverse wall members 80 and 81 in which a rotatable cranking body 82 is supported by bearings 84 and 86 for rotation about a primary or first axis 87. A nutatable body 90 is rotatably supported from the cranking body 82 by bearings 92 and 94 on a second axis 96 inclined with respect to the first axis 87 by the angle a.The body 90 includes a supporting shaft 98 on which a pair of conical members 100 and 102 are supported for relative axial movement along the second axis 96 and for limited rotation relative to the shaft 98. The conical members 100 and 102 are spaced on the shaft 98 by a system of ball ramps, generaly designated by the reference numeral t04 and which function to move the conical members 100 and 102 axially away from each other in response to torque loading on the transmission. The ball ramp system 104 is disclosed in United States Patent Application Ser. No. 5,605.

Although the conical members 100 and 102 are permitted relative rotation on the supporting shaft 98, they are restrained against rotation with respect to the shaft 98 for a given torque loading on the transmission as a result of ball ramp system 104 which is fixed or coupled for rotation with the shaft 98.

The exterior surfaces of the conical members 100 and 102 are of a variable radius Rb and are in rolling friction engagement with interior traction surfaces of a radius Rw on a pair of rings 106 and 108 fixed against rotation with respect to the casing 54 but axially movable along the first axis 87 toward and away from a point S of intersection of the axes 87 and 96 under the control of an electrically driven control screw 109.

As the cranking body 82 is driven by torque at the input shaft 1 8 of the transmission 20, the body 90 will be carried in nutation about the axis 87 causing rotation of the body 90 and thus of the shaft 98. The combined movement of the shaft 98 is transmitted by a bevel gear 110 coupled for rotation with the shaft 98, through an idler gear 11 2 (Fig. 3) carried by the cranking body 82, to a bevel gear 114 keyed for rotation with the variable output shaft 22 of the transmission on the axis 82. The relative movement of the gears 110, 11 2 and 114 is depicted in Fig. 3 of the drawings.Also the respective rotational speeds of these gears are related by the general equation: o - = ( p=0 p = 0 In this equation, & is the speed of rotation of the transmission input or of the cranking member 82; ss is the speed of rotation of the nutating body 90 about the axis 96 in a fixed frame of reference; w is the rotational speed of the rings 106 and 108 about the axis 87; and p is the ratio of the radii of the external conical surfaces of the members 100 and 102 or Rb to the radii on the traction surfaces of the rings 106 and 108 or R, (p = Rb/R,,). In the particular transmission shown, the rings 106 and 108 are held against rotation with the casing 54 so that w= 0.The general equation may be simplified to p = & 1 - 1 /p). Further, if the ratio of the number of teeth on the gear 1 10 divided by the number of teeth on the gear 1 14 is k, then the speed of the output shaft 22 (H) is related to k, p, and & by the equation: a = -k/p).

From this latter equation, it will be apparent that the output rotation (8) will be a reversal of input rotation ( & when the function k/p is greater than 1; that output rotation will be zero regardless of input rotation when k/p is equal to 1; and that output rotation will be in the same direction as input rotation when k/p is less than 1. As will be observed from the geometrical configuration of the transmission 20 in Fig. 2a, the maximum numerical value of the function p or Rb/RW will approach but not reach unity. The minimum value of p, though theoretically unlimited, is dependent on the physical dimensions of the transmission and in practice may extend to an approximate numerical value of 0.4, for example.The numerical value of k may be selected from a relatively wide range of numerical values and if equated to the maximum value of p, say 0.88, then the range of input/output speed rations available in the transmission 20 will be infinite. Furthermore, a directional reversal of rotation at the output shaft 22 relative to the input shaft 1 8 may be achieved with adjustable values of p which bracket or which extend above or below the numerical value of k It is preferred that the transmission be designed with values of kand p which permit at least a zero output shaft rotation (B = 0) regardless of input shaft rotation ( & .

Although as indicated, the specific construction of the transmission 20 may differ from that illustrated in Fig. 2a without departure from the broader aspects of the invention, the illustrated construction provides several advantages which contribute to overall system integrity and operation. For example, the particular transmission embodiment illustrated provides a wide range of infinitely variable speed ratios and is capable of transmitting power in excess of that developed by conventional automotive engines at high efficiencies. The bearings 84 and 86 on which the cranking body 82 is rotatably supported also support the flywheel 1 6 and provide a substantial moment arm by which precessional forces exhibited by the flywheel 1 6 may be controlled.Furthermore, the cranking body 82 rotates directly with the flywheel 1 6 and thus represents, in itself, a kinetic energy storage capacity which augments that of the flywheel 16.

As mentioned, design flexibility in the relative sizes of the gears 11 0, 11 2 and 114 or their equivalent, enables variation in system design including a possible elimination of the mode control unit 24. This is possible because of the facility for the transmission 20 to be designed to handle "forward", "neutral" and "reverse" modes of operation.

While the mode control unit may be considered as an optional component depending on the particular design of the transmission unit 20, its inclusion in the hybrid system is advantageous and as such is preferred. In particular, the mode control unit 24 permits a design of the transmission unit 20 which provides a wide range of infinitely or continuously variable input/output speed ratios; it enables a complete decoupling of the flywheel 1 6 as well as the engine 10 from the load propelling shaft 26; and it enables a direct coupling of the engine power shaft 12 with the load propelling shaft 26. The structural organization by which these characteristics are obtained may be appreciated by reference to Fig. 2b of the drawings.

In Fig. 2b, it will be noted that the variable speed output shaft 22 of the transmission unit 20 is a tubular shaft to which a sun gear 11 6 is keyed or otherwise coupled for direct rotation with the shaft 22. The sun gear 11 6 meshes with one or more, preferably three planet gears 11 8 rotatable on shafts 1 20 carried by a pair of interconnected carrier rings 1 22 and 1 24 journalled for rotation on the variable speed output shaft 22. In the embodiment disclosed, the planets 11 8 are compound planet gears which extend in meshing relation between the sun gear 11 6 and a ring gear 126.The ring gear 126 is fixed for direct rotation with a spider assembly 128 which in turn is coupled for rotation directly with the propelling shaft 26.

As will be seen from the speed ratio equations given above, the widest range of variable speed ratios in the transmission unit 20 is provided where the rotational direction of the variable speed output shaft 22 is opposite to that of the input shaft 1 8. To facilitate a direct drive connection of the input shaft 18 to the propelling shaft 26 it is preferred that in a "forward" mode of operation, power transmission between the variable speed output shaft 22 and the propelling shaft 26 effect a directional reversal of these two shafts. To provide this mode of operation, therefore, a clutch C1 is provided by which the carrier rings 1 22 and 1 24 are locked against rotation.Thus, power will be transmitted from the sun gear 11 6 and output shaft 22 through the planet gears 11 8 to the ring gear 1 26 and spider 1 28 to the propelling shaft 26.

To provide a "reverse" operational mode, the clutch C1 is disengaged and a clutch C2 engaged to lock the assembly of the sun gear carrier rings 122, 124, planet gear 11 8 and sun gear 11 6 as a unit. In this mode of operation, the propelling shaft 26 will be driven directly with the variable speed output shaft 22. A third clutch C3 is provided to effect a "direct drive" mode.In this respect it will be noted that the shaft 30, which extends through the hollow variable speed output shaft 22, is keyed or otherwise connected for direct rotation with the cranking body 82 of the transmission unit 20 (see Fig. 2a) and extends between the body 82 and a flared plate 1 30. The plate 1 30 is releasably engageable by the clutch C3 to the spider assembly 1 28 such that when the clutch C3 is engaged, a direct torque transmitting train exists between the transmission unit input shaft 1 8 and the propelling shaft 26.

A "neutral" condition of the mode control unit 24 is provided by merely adjusting the three clutches C1, C2 and C3 to a disengaged condition. It will be noted also that the clutches Cl, C2 and C3 are alternately engageable in the sense that only one of the three clutches is engaged while the other two are disengaged to provide the various operational modes described.

In the operation of the hybrid power system illustrated in Figs. 1-3 of the drawings, and assuming all components to be at rest, the mode control unit 24 will be in a "neutral" condition and the clutch 14 will be engaged by the compression springs 69. The engine 10 is started in conventional fashion by manipulation of the main switch 46, closure of the ignition switch 42, and energization of an electric starter motor (not shown) drivingly coupled with the flywheel 1 6.

Rotation of the flywheel will crank the engine 10 to initiate operation thereof in conventional fashion. It will be noted that at this stage of operation, the flywheel 1 6 functions in the same manner as a conventional crank shaft flywheel. Acceleration of the vehicle or other load to be driven by the system is brought about by depressing the accelerator pedal 50 which, through the control of the computer 42, will adjust the mode control unit to engage the clutch C1 and at the same time regulate the speed of the engine by control of the throttle 38 and adjust the speed ratio of the I.V. transmission unit 20 to accelerate the propelling shaft 26 and drive wheels 28.In this respect, it will be noted that while the I.V. transmission may be adjusted in the same manner as a conventional automotive transmission to relate speed and torque components of the power required for a given rate of acceleration, it will do so more efficiently as a result of the continuously or infinitely variable ratio available in the transmission unit 20.

Accordingly the fuel supply to the engine 10 and the transmission unit 20 may be adjusted to optimize fuel consuming operation of the engine. Propelling of the vehicle at constant low or moderate speeds which require power developing operation of the engine 10 will likewise be carried out in this manner. It is to be noted, however, that at all times during power generating operation of the engine 10, the clutch 14 will be in a fully engaged condition to couple the flywheel 1 6 and the crank shaft 34 of the engine 10.

Deceleration of the vehicle or load may occur either with or without regenerative braking or storage of kinetic energy in the flywheel 16 and components of the I.V. transmission 20 rotatable therewith. If it is assumed that the flywheel 1 6 is rotating at less than its maximum permitted speed and that it is desired to decelerate the vehicle at a higher rate of deceleration than would occur by coasting, the brake pedal 52 would be depressed, causing the clutch 14 to be either partially or completely disengaged and the l.V. transmission unit 20 to be downshifted.Under this condition, the energy of vehicular momentum would be absorbed or stored by increasing the speed of the flywheel 1 6. Power generating operation of the engine will be terminated during such deceleration by opening the ignition switch 42 and closing the valve 40 for so long as the speed of the flywheel 1 6 remains above that speed representing an amount of stored kinetic energy needed to restart the engine by re-engaging the clutch 14 and reversing the condition of the ignition switch 42 and the fuel supply valve 40.

Energy stored in the flywheel may augment the power developed by the engine depending on the amount of accelerating power to be applied to the load as directed by adjustment of the accelerator pedal 52 and the percentage of that accelerating power available as kinetic energy in the flywheel 1 6. For example, if the flywheel is rotating at speeds above the speed of the engine and load accelerating power is called for, the accelerating power will be supplied by the flywheel 1 6 through the l.V. transmission unit 20 until the flywheel slows to a rotational speed approximating that engine speed at which the engine 10 will develop power called for by the particular adjustment of the accelerating pedal 52. When the energy available in the flywheel represents a large percentage of the accelerating power called for, engine speed required to develop that accelerating power may be at or only slightly above idling speed. In this case, engine operation with fuel supply would merely be reinitiated when the speed of the flywheel dropped to the idling speed of the engine. If, on the other hand, maximum accelerating power is called for at a time when the flywheel is rotating at its maximum permissible speed and also when the engine is off, system operation would involve opening the fuel supply valve 40 to reinstate fueled operation of the engine 10.In this condition, power transmitted to the load would be supplied both from the flywheel 1 6 and the engine 1 0. In particular, the clutch 14 will be adjusted toward a condition of full engagement during the period of such maximum acceleration. At the same time, the I.V. transmission 20 will be adjusted toward a higher output/input speed ratio. The kinetic energy stored in the flywheel may be dissipated as power either to the load through the l.V. transmission 20, to the engine 10 through the clutch 14 and thus reduce the time required for the engine to attain full power generating speeds, or the flywheel power may be transmitted to both the load and the engine.The precise distribution of flywheel power at any instant of maximum acceleration may be optimized by controlled adjustment of the clutch 14 and the l.V. transmission unit 20. In any event, flywheel speed will decrease whereas engine speed will increase to a point where engine and flywheel speeds are equal. Thereafter, continued application of maximum accelerating power would be developed exclusively by the engine 1 0. Thus, it will be seen that power for acceleration of a vehicle, or of an inertial load in general, may be a combination of energy stored in the flywheel 1 6 and power developed by the engine 1 0.

When it is desired to use the engine 10 to decelerate the inertial load represented by an automotive vehicle, the fuel supply valve 40 may be again turned off and the clutch 14 fully engaged to couple the engine and wheels 28. Also, the engine throttle 38 may be closed to maximise the pumping torque of the engine and the l.V. transmission may be down-shifted or otherwise regulated to achieve the degree of engine braking desired.

Under operating conditions where the vehicle or load is to be driven at relatively constant speeds requiring continuous development of power by the prime mover or engine 10, such as under highway driving conditions in the case of an automotive vehicle, the mode control unit is shifted to the "direct drive" mode by engaging the clutch C3 and disengaging the clutches C1 and C2. In this condition of operation, the engine drive shaft 1 2 will be coupled directly with the load propelling shaft 26 with the result that the l.V. transmission unit 20 will merely idle with no torque transfer between the traction drive components thereof. While the surfaces of the cone members 100 and 102 may be in contact with the traction surfaces on the rings 106 and 108, the absence of a torque load will preclude any normal force loading of these components.

Also, it is contemplated that these surfaces may be retracted out of engagement with each other under a no-load condition.

In the "direct drive" mode, therefore, the system operates as a conventional automotive drive train with the flywheel 1 6 and components rotatable therewith functioning solely in the manner of a conventional crank shaft flywheel. The facility for shifting to a direct drive is made available by the mode control unit 24 and provides the potential for overall system efficiencies higher than a system using an appropriately designed l.V. transmission unit alone. It is known for example, that the fuel consuming efficiency of a conventional automotive drive train in a "direct drive" mode at continuous moderate to high speeds is quite good. In the "direct drive" mode of the present invention, such existing conditions are retained with no loss of efficiency in the system due to efficiency losses in the transmission unit 20.Also it will be appreciated that where the unit 20 is designed for a ratio range extending to 1:1, alternate coupling of the load propelling shaft 26 with the variable speed output shaft 22 and the direct drive shaft 30 may be synchronous with no energy loss upon engagement of the clutch C3. The characteristics of the l.V. transmission unit 20, however, are such that its operating efficiency increases to maximum at the high end of its output/input speed ratio range.The mode control unit, therefore, and in particular the clutch C3 enables an I.V. transmission unit design with an output/input speed ratio range extending from zero to less than 1:1 thereby to provide increased I.V. unit efficiencies when the unit 20 is needed for intermittent or city driving conditions under which the energy storing capacity of the flywheel is important to reduced fuel consumption. It is contemplated, therefore, that shifting the coupling of the load propelling shaft 26 between the variable speed output shaft 22 and the direct drive shaft 30 may be nonsynchronous; that is, with the slipping of the clutch C3 and a corresponding loss of energy less than that gained by increased efficiency in the operation of the l.V. unit 20.It will be appreciated, therefore, that the mode control unit 24 adds materially to design flexibility in the overall system.

To provide a more complete understanding of the hybrid system shown in Figs. 1-3 under intermittent or city driving conditions, reference is made to Fig. 4 of the drawings in which curves are plotted in which calculated quantitative values of either parameters are plotted against time in seconds. The curves shown in Fig. 4 were calculated using a computer simulated automotive passenger vehicle equipped with the hybrid power system shown in Figs. 1-3 and having the following specifications: Vehicle weight - 2890 Ibs (curb) - 3190 Ibs (loaded) Engine - 2. 1 liter with fuel injection - 4 cylinders in-line - 100 HP at 5250 rpm - Compression ratio 8.5:1 Axle Ratio - 3.73:1 Max. I.V.Unit Efficiency - 91% Combined inertia of flywheel and connected rotary parts - 0.704 Kg-m2 Exhaust system - Closed loop Lambda-Sond converter with 3-way catalyst With reference to curves A-H of Fig. 4, curve A is a graphic representation of part of a standard city driving cycle. Curve B is the result of plotting as ordinate values, energy in Joules needed at the drive wheels to accelerate the mass of the vehicle against its aerodynamic and rolling resistance to the speed on curve A corresponding to the same point in time. Negative values on curve B represent energy recoverable deceleration.

Curve C is the portion of wheel energy in horse power to be supplied by the engine. Curve D is the energy in Joules available from the flywheel and parts rotatable directly therewith. As above-mentioned, in reaccelerating the vehicle from a stop, energy is first drawn from this source with the difference needed to make up the required wheel energy to be supplied by the engine.

Curves E and F illustrate, respectively, whether the engine is off or on and when on, the speed of the engine. Flywheel speed is represented by curve G and l.V. ratio expressed as output/input is represented by curve H.

The curves illustrated in Fig. 4 were developed by a computer simulation of the vehicle abovementioned. Although not shown in Fig. 4, the same computer simulation results in a fuel economy gain of from 1 9mpg to 32mpg and with low emission levels, specifically NO, - 0.06, CO - 0.33 and HC - 0.09. Although it is recognized that results in actual practice will be somewhat less than these theoretical results due to transients and other factors that cannot be taken into consideration by a computer simulation, the potential theoretical gains are so substantial that actual results which fall considerably short of the theoretical results would represent a substantial improvement in fuel economy.

The significance of the clutch 1 4 in terms of its physical position and function in the system of the present invention will now be appreciated. It will be noted first that at all times when the engine 10 is used for its primary purpose of developing load driving power (or under certain circumstances as described for absorbing load momentum), the clutch 14 is fully engaged to provide a direct coupling of the engine crank shaft 34 with the flywheel 1 6 and the input shaft 1 8 of the I.V. transmission unit 20. When such a coupling exists, the flywheel 1 6 rotates at the same speed as the engine crank shaft 34 and acts in all respects as a conventional crank shaft flywheel.

Secondly, adjustment of the clutch 14 to a condition of partial engagement in which it will transmit only a limited amount of torque enables the engine or prime mover 10 to be cranked with the fuel supply 36 cut off or reduced and at speeds which are substantially below flywheel speeds but adequate to maintain continuity of lubrication, continuity of accessory drives and the like.As will be appreciated by those skilled in the art, the idling speed for an engine or prime mover may vary widely, but is intended herein to mean that minimum speed at which the engine or prime mover 10 will sustain operation with fuel alone at no load. "Cranking speed", where used herein is intended to mean that speed at which engine pumping and friction losses are minimal and at which engine driven accessories, such as coolant and lubricant circulating pumps, electric storage battery charging system as well as power driven accessories like power steering, power brakes and air conditioning are maintained. Torque losses in cranking the engine 10, namely pumping losses and friction losses, approach a minimum near idling speed but decrease further at a lower cranking speed. Since the cranking speed is a function of torque transmitted through the clutch 14, the precise speed at which the engine will be cranked may be regulated by adjusting the pressure under which the friction pads 68 are urged against the disc 64. The losses of so cranking the engine 10 may be further reduced by opening the throttle 38 during the period that the clutch is adjusted to crank a conventional automotive internal combustion engine and even further by closing the valves (not shown) of the engine in accordance with the disclosure of an article entitled "Valve Selector Hardware" SEA Technical Paper 78 0146, dated March 3, 1978.

When the engine is cranked using kinetic energy stored in the flywheel as above described, the fuel supply valve 40 may be completely closed or it may be adjusted to a partially closed condition in which the fuel supply to the engine is reduced to a level below that necessary to maintain engine operation by fuel supply alone. While maximum conservation of potential energy or fuel will often result with the valve 40 or its equivalent completely closed, overall system operation at minimal fuel consumption may be improved by fuel supply at levels reduced below that necessary to maintain engine idle speeds but adequate to maintain engine temperature.

Finally, the clutch 14 may be adjusted to a completely disengaged condition and the engine 10 completely shut off so long as adequate kinetic energy is stored in the flywheel for engine restarting purposes. Where this mode of operation is contemplated, the system may be provided with a separate accessory drive (not shown) extending from the flywheel 1 6 to the various accessories to be driven by the flywheel during periods -of time the engine 10 is inoperative.

In Fig. 5 of the drawings, a modified embodiment is schematically illustrated to include the same power train components shown in Fig. 1 except that the flywheel 1 6' is linked or drivingly connected for rotation with the shaft 18' at a fixed ratio by bevel gearing 1 32 and is of a design capable of storing larger amounts of kinetic energy than the flywheel 1 6 of Fig. 1. The gear ratio of the gearing 1 32 is selected so that the flywheel rotates at a higher speed than the shaft 12'. To represent the relative class of the flywheel 16', an evacuated housing 1 34 is illustrated schematically in Fig. 5 as representative of means to cut windage losses in a flywheel of this type.Although the engine 10' or prime mover of the system illustrated in Fig. 5 is like the engine 10 in Fig. 1 in all respects, it is intended in this case to be a prime mover which operates at a governed or constant operating speed with variation in the amount of fuel injected into the engine 10'. The mode control unit 24' may be modified from the unit 24 of Fig. 1 only in terms of reduction ratio. The system of Fig. 5 is, therefore, representative of a power system for use in larger vehicles such as buses or trucks where the power to weight ratio is low relative to automotive vehicles, for example, where high rates of load acceleration are called for.

The principal difference in the operation of the system disclosed in Fig. 5 to practice a variation in the method of the present invention resides in operation so that the speed of the flywheel is maintained at all times above the governed operating speed of the engine 1 0'. The clutch 14' is retained in the system of Fig. 5 and as before is operable to transmit full engine power in the direction of the load. On startup, therefore, the engine 10' will be operated to supply kinetic energy to the flywheel until such time as the rotational speed of the flywheel 16' is the same as the governed operating speed of the engine power shaft 1 2. Load acceleration is initiated after adjustment of the unit 24' and by adjustment of the l.V. transmission 20'.

On load deceleration, the kinetic energy of load momentum is fed back as before to the flywheel 16' but to drive the flywheel at speeds substantially in excess of engine operating speeds. This is accomplished by downshifting the l.V. transmission 20'. During subsequent acceleration of the load, assuming the flywheel 16' to be rotating at near maximum speeds of, for example, two to three times the operating speed of the engine drive shaft 1 2', the kinetic energy stored in the flywheel may be directed to the load, to the engine or both in a manner comparable to that described above with respect to Fig. 1. Because of the relative engine and flywheel speeds, however, prime mover developed power will never be directed to or absorbed by the flywheel 16'.Prime mover developed power will, of course, maintain minimal flywheel speeds by supplying a sufficient amount of energy to overcome friction and other losses tending to reduce the speed of flywheel rotation. In all other respects, the operation of the embodiment of Fig. 5 is the same as that described above with respect to Fig. 1.

In Fig. 6, a hybrid system in accordance with the invention is embodied in a power train of the type in which the engine or prime mover axis is generally parallel to the load propelling shaft or shafts. Such power trains are particularly suited to automotive front wheel drives, for example. Thus in Fig. 6, the engine 210 includes a power shaft 212 which, like the previously described embodiments, is a direct extension of the engine crank shaft without the conventional crank shaft flywheel. As in Figs. 1 and 2, the power shaft 212 carries a light-weight clutch disc 264 for releasable coupling engagement by clutch components carried directly by a flywheel 216. In this embodiment, the flywheel 216 is journalled by bearings 217 and 219 in a frame component 221 and on an extension 223 of the power shaft 202, respectively.The flywheel 216 is again linked for rotation at all times with the input shaft 218 of the l.V. transmission unit 220. In this instance, however, the linking is through a gear train including a drive gear 225 carried by the flywheel, an idler gear 227 and a driven gear 229 keyed to the l.V. input shaft 218. The variable speed output shaft 222 of the unit 220 is coupled by a gear 231 directly with a differential unit 223 from which a pair of propelling shafts 226 extend to drive wheels 228.

The idler gear 227 is coupled directly by a shaft 235 with such accessories as the generator, fuel pump, oil pump, air conditioning, power steering unit and power brake unit, all of which are powered normally by the engine 210. Though not detailed in Fig. 6, these accessories are represented by the box 237 and labeled "accessories". An important feature of the power train shown in Fig. 6 is that the inclusion of the accessory drive in the gear train between the flywheel 216 and the I.V. input shaft 218 enables the accessories to be powered by the flywheel 216 with the flywheel completely disengaged from the clutch disc 264 and the engine 210 completely shut off. The operational characteristics of the embodiment shown in Fig. 6 are otherwise the same as the previously described embodiments.

Thus, it will be appreciated that in the preferred embodiments, highly effective hybrid power systems and methods are provided. While the energy saving potential and operating requirements of hybrid systems have been recognized previously, the power trains have been complex as regards controls and component organization, space consuming by comparison to conventional automative power trains and potentially an additional source of mechanical failure. The embodiments described herein show hybrid power systems which require minimal modification to existing vehicle structure and which permit highly efficient operation of an l.V. transmission capable of relating the speed of both a prime mover power shaft and a flywheel with a load propelling shaft for rotation of the propelling shaft in forward and reverse directions while facilitating a direct drive connection.

Claims (14)

1. A method of operating apparatus for driving a movable load, such apparatus including a prime mover, means for supplying fuel to the prime mover, means for transmitting power from the prime mover to the load and to at least one ancillary, and means for storing energy; the method comprising the steps of storing energy made available by the load during deceleration thereof; terminating fuelled operation of the prime mover during periods of deceleration or rest of said load; transmitting power from said energy storing means to said ancillary during periods when fuelled operation of the prime mover is terminated; and recommencing fuelled operation of the prime mover when the energy stored by said storing means has been reduced to a predetermined value.

2. A method as claimed in claim 1 wherein power from said energy storing means is transmitted to crank the prime mover for continued operation of an ancillary driven thereby, and the supply of fuel to the prime mover is reduced to a level less than that required for prime mover operation using fuel alone.

3. A method as claimed in claim 2, wherein the fuel supply to the prime mover is terminated completely during cranking thereof.

4. A method as claimed in claim 1, 2, or 3, wherein power provided by energy stored by said energy storing means is combined with power developed by the prime mover to accelerate the load.

5. A method as claimed in claim 4, wherein the energy storing means is a flywheel, the prime mover includes a rotatable output shaft, and the step of combining power from the energy storing means and the prime mover comprises discharging kinetic energy stored in the flywheel while increasing the speed of the output shaft until the speeds of the output shaft and flywheel are equal.

6. A method as claimed in any of claims 1 to 4, wherein the prime mover develops variable power at constant speed and the energy storing means is a flywheel, the speed of which is maintained above the speed of the prime mover.

7. A method of operating apparatus for driving a load, substantially as hereinbefore described with reference to the accompanying drawings.

8. Apparatus for driving a movable load, comprising a prime mover; means for supplying fuel to the prime mover; means for transmitting power from the prime mover to the load and to at least one ancillary; means arranged to store energy made available during deceleration of the load; means arranged to terminate fuelled operation of the prime mover during periods of deceleration or rest of said load; means arranged to transmit power from said energy storing means to said ancillary during periods when fuelled operation of the prime mover is terminated; and means arranged to restart fuelled operation of the prime mover when the energy stored by said storing means is reduced to a predetermined level.

9. Apparatus for driving an inertial load, comprising a prime mover having an output shaft, a fuel supply, and means for controlling the supply of fuel to the prime mover to vary the speed thereof and to reduce the supply to a level below that necessary for maintaining unassisted operation of the prime mover; a variable speed transmission having an input shaft and an output shaft; means for transmitting power from the transmission output shaft to the load; a flywheel connected for rotation directly with said transmission input shaft; and means for selectively coupling said flywheel and said prime mover output shaft to enable the transmission of full torque or less than full torque therebetween.

10. Apparatus as claimed in claim 9 wherein said flywheel is keyed to said transmission input shaft.

11. Apparatus as claimed in claim 10 wherein said flywheel is connected to said transmission input shaft by gearing.

1 2. Apparatus as claimed in claim 11 wherein said gearing has a gear ratio such that the speed of rotation of the flywheel is greater than that of said transmission input shaft.

1 3. Apparatus as claimed in any of claims 9 to 12, wherein an ancillary drive train is connected between said flywheel and said coupling means so that an ancillary may be driven by the flywheel when the coupling means is operated such that no torque is transmitted between said flywheel and said prime mover output shaft and the prime mover is completely shut off.

14. Apparatus as claimed in any of claims 9 to 1 2 wherein said flywheel cranks the prime mover at or below idling speeds during transmission of less than full torque by said coupling means.

1 5. Apparatus as claimed in any of claims 9 to 1 4 wherein said variable speed transmission comprises a frame, a cranking body journalled for rotation in said frame on a first axis, said transmission input shaft being coupled to said cranking body, a nutating body journalled for rotation in said cranking body on a second axis inclined with respect to and intersecting said first axis, and means for converting movement of said transmission input shaft, said cranking body and said nutating body to rotation of said transmission output shaft at infinitely variable ratios to the speed of input shaft rotation.

1 6. Apparatus as claimed in claim 15, wherein said cranking body is of a length approximating the length of the transmission along said first axis and is journalled for rotation in said frame by bearings at opposite ends of said cranking body and concentric with said first axis, said flywheel and said input shaft being supported directly by said cranking body.

1 7. Apparatus for driving a load, substantially as herein before described with reference to the accompanying drawings.