Abstract:
A motor vehicle having a primary internal combustion engine is equipped with a secondary engine and an electric motor to supplement the power produced by the primary engine. The primary engine provides power for acceleration and hill climbing. When in a cruising mode of travel, the primary engine is deactivated, and the secondary engine, which is smaller and more fuel-efficient than the primary engine, provides the driving power. The electric motor adjustably augments the power provided by the secondary engine.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to hybrid vehicles which use electric motors powered by batteries in combination with internal combustion engines to improve fuel efficiency. 
   2. Description of the Prior Art 
   There is considerable interest in the development of hybrid vehicles to improve fuel efficiency without sacrifice in mechanical performance. Such vehicles combine the use of internal combustion engines and electric motors. 
   Some hybrid vehicles use a relatively small but fuel-efficient internal combustion engine to enable it to cruise economically, and use additional power from the electric motor to assist in acceleration and hill-climbing, etc. Others use the electric motor to cruise, and supplement it with power from the engine for acceleration and hill-climbing, etc. Still others use any combination of both modes of operation. Power from the engine is used to charge the batteries. Regenerative braking is sometimes used to assist in recharging the batteries and thereby conserve fuel. 
   Although the hybrid system significantly improves automotive fuel efficiency, it has many disadvantages. It often requires severe down-sizing of the engine to achieve improved fuel efficiency and therefore needs a powerful electric motor to add sufficient power for acceleration and hill-climbing. This requires a complex and expensive electrical control system, a set of high capacity, high output batteries, and a powerful electric motor, resulting in high initial cost and high maintenance costs. These costs may not be fully offset by savings attributable to the improved fuel efficiency of the vehicle. For instance, the limited useful life of the batteries will require them to be replaced before these savings are fully realized. 
   On the other hand, using a large engine in combination with a smaller, less powerful but less expensive electric motor system will not solve the problem either. Firstly, the larger engine will be less fuel-efficient because of its larger size. Then, to cruise economically the vehicle will still need a sufficiently powerful electric motor with high capacity powerful batteries to supply enough power for cruising, otherwise the larger engine will have to be operated more, simply to assist in cruising. This would reduce the vehicle&#39;s fuel efficiency, yet still largely retain the high initial and maintenance cost of the components of the system. 
   So far, therefore, the hybrid vehicle as an approach towards achieving fuel efficiency in motor vehicles is proving to be unsatisfactory. If the engine is downsized sufficiently to permit the vehicle to cruise economically, the electric motor has to be made powerful enough to give the vehicle acceptable acceleration and hill climbing capability; but the powerful electric motor is expensive and requires expensive high capacity batteries, resulting in high initial and maintenance cost. On the other hand, if the electric motor is made less powerful so as to reduce its cost and the cost of the batteries, then the engine will need to be more powerful (and less fuel efficient) in order for the vehicle to have acceptable acceleration and hill-climbing capability. 
   What is needed is a system that will not only permit sufficient downsizing of the engine that is used for cruising so that the vehicle can cruise over long distances with significantly reduced fuel consumption, but will also permit sufficient downsizing of the electric motor and batteries. Such downsizing should be accomplished without sacrifice in the accelerating and hill-climbing performance of the vehicle, and preferably without extensive redesign of motor vehicles as they currently exist. 
   The prior art has not met this need. The present invention is intended to provide a solution to this problem. It does so by recognizing that motor vehicles really need two distinct types of power sources in order to have satisfactory mechanical performance and to achieve high fuel efficiency for long distance travel. These requirements are, namely, (1) a power source with high power output and high torque for acceptable acceleration, towing and hill-climbing capability, and (2) a lower power output power source capable of providing continuous lower power with high fuel-efficiency for long distance travel at cruising speeds. This invention meets the first requirement through the use of the standard power train of current motor vehicles without any essential modifications, and then meets the second requirement through the use of a fuel-efficient hybrid system comprising a secondary, smaller internal combustion auxiliary engine augmented by an electric motor for cruising. Furthermore mechanical efficiency of this hybrid system is improved by directly coupling the hybrid system to the drive axle, bypassing the transmission, thereby eliminating any frictional power losses generated in the transmission. 
   The manner of interaction of these various drive components are unobvious and they produce these unexpected advantages. This particular combination of parts and the manner in which they interact to achieve these results has not previously been described. 
   U.S. Pat. No. 6,179,078 to Belloso discloses an inexpensive, fuel-efficient automobile which uses two internal combustion engines; two for acceleration and one for cruising. Each engine is coupled to a driving wheel via a torque converter. It uses an electric motor for reverse motion, not for the purpose of improving fuel economy. 
   U.S. Pat. No. 6,852,062 to Abner, et. al., discloses two internal combustion engines and one or two starter/generators, all coupled to one transmission. It uses two engines to start and then uses the engines and motors to individually or jointly transmit power to the transmission thence to the drive wheels of the vehicle. None of the engines or motors bypass the transmission for the purpose of eliminating frictional power losses. The many modifications necessary to couple the two internal combustion engines and starter/generators to the transmission and to coordinate their functions make it difficult to use this system as an add-on feature to currently existing motor vehicles. 
   U.S. Pat. No. 6,722,458 to Hofbauer discloses two internal combustion engines which are both coupled by clutches to one transmission which drives the drive wheels. It further discloses the use of one or two electric motors. The vehicle starts and accelerates on power from the two engines, possibly supplemented by power from the motor(s), and cruises on power from one engine, one motor or a combination of both. Neither of the engines bypass the transmission for the purpose of eliminating frictional power losses generated therein. It does not teach the specific use of a fuel-efficient engine directly coupled to the differential primarily for the purpose of maintaining the vehicle at cruising speed. The many modifications needed to couple both engines and possibly one electric motor to the transmission and the associated control means to coordinate their function make it difficult to adapt this system as an add-on feature to existing motor vehicles. 
   U.S. Pat. No. 6,306,056 to Moore discloses a dual engine hybrid electric vehicle including two internal combustion engines and one motor/generator. Both engines are coupled to one transmission which is then coupled to the differential and drive wheels. During normal driving conditions a single engine is used. When load increases, the electric motor is used temporarily, then the second engine is speeded up to assist the first engine. Presumably both engines are used to start and accelerate the vehicle until it reaches normal driving conditions, wherein one engine may be turned off. Neither engine bypasses the transmission for the specific purpose of eliminating any frictional power losses generated therein. The many modifications necessary to couple both engines to a single transmission makes this system unacceptable as an add-on feature for an existing vehicle. 
   U.S. Pat. No. 5,492,189 to Kriegler, et. al., discloses a hybrid drive system comprising one internal combustion engine operating in steady-state mode and two transiently operating engines configured as hydraulic engines or electric motors. All engines are coupled to a planetary gear system with associated control means for coordinating the functioning of the internal combustion engine and the two transient engines. It does not disclose use of two internal combustion engines. It does not teach use of a primary internal combustion combined with a secondary internal combustion engine augmented by an electric motor bypassing the transmission, for the specific purpose of maintaining the vehicle at cruising speed. Furthermore, the many new features and modifications to adapt this system to a planetary gear system precludes easy application as an add-on feature to current motor vehicles. 
   U.S. Pat. No. 6,814,686 to Carriere, et. al., discloses primary and secondary engines and a phase clutch interactive between the crankshafts of the primary and secondary engines to provide proper coupling of the crankshafts. Both engines are coupled to one transmission which transmits power to drive the vehicle. Both engines are used to start and accelerate, and one engine is used to cruise. 
   It is accordingly an object of this invention to provide a hybrid vehicle capable of traveling at cruising speed for long distances with improved fuel efficiency. 
   It is another object of the present invention to provide a vehicle as in the foregoing object which does not require expensive powerful electric motors and powerful high-capacity batteries. 
   It is a further object of this invention to provide a vehicle of the aforesaid nature having sufficient power for quick acceleration and good hill-climbing abilities. 
   It is a still further object of the present invention to provide a component system for enhancing the fuel efficiency of motor vehicles, said system being amenable to installation into current motor vehicles in the streets and preserving the integrity of the power train of these vehicles. 
   It is yet another object of this invention to provide a hybrid vehicle with improved fuel efficiency and reduced manufacturing and maintenance costs. 
   These objects and other objects and advantages of the invention will be apparent from the following description. 
   SUMMARY OF THE INVENTION 
   In summary, the above and other beneficial objects and advantages are accomplished in accordance with the present invention by a hybrid motor vehicle having a chassis, front and rear paired wheels, at least one of said pairs serving as driving wheels, and an improved power train comprising:
     a) a primary internal combustion engine mounted on said chassis, said primary engine being of suitable size and power to accelerate said vehicle to cruising speed in an acceptable acceleration rate and provide acceptable hill-climbing and load-carrying capacity, a speed change transmission interactive with said primary engine and associated means for transmitting power to said driving wheels,   b) a secondary internal combustion engine mounted on said chassis, said secondary engine being of suitable size and power so that when operating at maximum efficiency it is capable of maintaining said vehicle at an acceptable cruising speed with maximal fuel efficiency, and associated means for transmitting power to said driving wheels while said vehicle is operated at cruising speed,   c) an electric motor mounted on said chassis, an associated rechargeable storage battery which activates said motor, a generator which recharges said battery, and power transfer means for transmitting power from said electric motor to said driving wheels to provide supplemental power for cruising,   d) means for shifting said transmission to neutral after said vehicle has been accelerated to cruising speed by said primary engine, and causing said vehicle to be maintained at cruising speed by power from said secondary engine supplemented, as needed, by power from said electric motor, and   e) means for shifting said transmission to “drive” to supply additional power from said primary engine whenever more power needs to be supplied to said drive wheels beyond that supplied by said secondary engine and electric motor.   

   The fundamental feature of this invention is that it uses a hybrid system comprised of said secondary engine and electric motor simply to maintain the vehicle at cruising speed. Since the power needed for cruising is much less than the power needed for acceleration and hill climbing, using the hybrid system solely for cruising results in fuel efficiency and permits downsizing and simplification of the system. For instance, the secondary engine used for cruising can be relatively small and therefore more fuel-efficient. Since the electric motor is not needed for acceleration and hill-climbing, but merely to assist the secondary cruiser engine in maintaining the vehicle at cruising speed, it also can be of relatively small size. Furthermore, since power from the motor is only used intermittently as needed to assist the secondary engine, the battery will not need to be as large and powerful as those used in current hybrid engines. For most vehicles, inexpensive lead-acid batteries may prove quite adequate. 
   Although the above-described downsizing of the secondary engine and its electric motor results in improvement in fuel efficiency for long distance travel at cruising speeds, increased power is periodically required for acceleration and hill-climbing. The improved power train of the present invention meets such need by the selective utilization of the power train of the existing motor vehicle, into which the components of the improved power train of this invention are installed. Since the engine of the existing vehicle is used only for limited periods of time, especially when traveling over long distances on the highways, the fact that it is relatively less fuel-efficient does not significantly affect the over-all fuel economy of a vehicle equipped with the improved power train of this invention. It is estimated that the vehicle will be traveling on the fuel-efficient secondary cruiser engine at least 50% of the time during city driving and up to 90% of the time while traveling on the highway, resulting in substantial fuel savings. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     With these and other advantages in view, the invention is disclosed in the following description which will be more fully understood when read in conjunction with the following drawings in which: 
       FIG. 1  is a schematic top view of a motor vehicle equipped with an embodiment of the improved power train of this invention. 
       FIG. 2  is a schematic top view of a motor vehicle equipped with an alternative embodiment of the improved power train of this invention. 
       FIG. 3  is a schematic top view of a motor vehicle equipped with a second alternative embodiment of the improved power train of this invention. 
       FIG. 4  is a magnified view, partly in section, of a portion of the embodiment of  FIG. 3 . 
       FIG. 5  is a schematic top view of a motor vehicle equipped with a third alternative embodiment of the improved power train of this invention. 
   

   For clarity of illustration, details which are not relevant to the invention, such as control linkages, gearshift linkages, internal parts of speed change transmissions, differentials and transaxles, engine mounts, suspension, etc., have been largely omitted from these drawings. 
   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the aforesaid drawings, there is shown in  FIG. 1  a motor vehicle chassis  11  with front wheels  12 , rear wheels  13 , front bumper  14  and rear bumper  15 . Mounted at the front portion of the chassis  11  is a commonplace standard engine component of an existing vehicle, herein designated as primary engine  16 . In the illustrated embodiment, engine  16  drives the front wheels  12  through its transaxle  17 , left and right halfshafts  18 , left and right front universal joints  19  and left and right axles  20 . This is essentially the layout of a standard front engine, front wheel drive vehicle. In fact, the size and power of primary engine  16  may be the same as those engines generally used in a regular non-hybrid vehicle of similar size. The transaxle  17  combines the functions of a speed change transmission, either manually operated or automatic, and the differential. In this embodiment, the transaxle  17  can be shifted to “neutral” while the vehicle is in motion, a feature which is common to most vehicles. Primary engine  16  is used to accelerate the vehicle from a dead stop to cruising speed. It is also used whenever increased power is needed, such as when climbing a hill, passing another vehicle or towing a trailer, etc. It is also used to move the vehicle in reverse. 
   A secondary engine  21  is mounted at the rear portion of chassis  11 . Engine  21  may also be referred to as a “cruiser” or “auxiliary” engine. CVT driver pulley  22  is mounted on the output shaft  23  of said engine  21  and is connected to driven pulley  24  by drive belt  25 . Driven pulley  24  is mounted on jack shaft  26  which is journaled on jack shaft bearing  27  and connected to pinion shaft  28  through jack shaft universal joint  29 . Pinion shaft  28  transmits power to rear differential  30  which is fixedly mounted on chassis  11 . Differential  30  transmits power to rear wheels  13  through rear universal joints  31  and rear axles  32  with independent rear suspension. 
   After the vehicle is accelerated to cruising speed by power from primary engine  16 , transaxle  17  is shifted to neutral, and secondary engine  21  is speeded up to transmit power through drive pulley  22 , drive belt  25 , driven pulley  24 , jack shaft  26 , pinion  28 , differential  30 , universal joints  31 , and rear axles  32  to rear wheels  13  to keep the vehicle moving forward at cruising speed. If more power is needed from time to time, electric motor  33  is switched on to draw variable amounts of power from battery  341  and transmit supplemental power to rear wheels  13  via motor drive chain  34  sprockets  35 , pinion  28 , differential  30 , universal joint  31  and axles  32 . When the vehicle needs to be slowed down, part of its kinetic energy can be converted to electricity by generator  36  which is connected to pinion  28  by generator chain  37  and sprockets  38 , well known to the art as regenerative braking. Other variations and features of regenerative braking, well known in the prior art, may be employed but need not be described here. The electrical connections and controls between the motor  33 , battery  341  and generator  36  are also well known in the prior art, and do not need to be shown and described in this disclosure. 
   The novel feature of this invention is that it uses an add-on hybrid power system comprised of secondary engine  21  and electric motor  33  to maintain the vehicle at cruising speed, and uses primary engine  16  for acceleration, hill climbing and reverse functionality. Because only a comparatively small amount of power is needed to maintain the vehicle at cruising speed, the hybrid power system can be downsized. This results in increased improvement in fuel efficiency as well as in reduction in the initial and maintenance costs of the secondary engine, battery and electric motor. 
   Furthermore, since the hybrid power system is essentially used only for what really amounts to an “overdrive” function, it does not really need to have a regular speed change transmission. One speed ratio serves perfectly well. At most, a limited range of speeds such as those provided by a movable sheave continuously variable ratio torque converter (CVT) may be quite satisfactory, resulting in further cost savings. 
     FIG. 2  illustrates how the invention may be embodied in a motor vehicle with standard front engine, rear wheel drive layout with a live unsprung rear axle, with provision to place the hybrid system at the front portion of the vehicle as well. This frees the rear portion of the vehicle for other uses such as for the trunk or cargo space. Primary engine  39 , which may be any commonplace automotive engine, is mounted on chassis  40 , and is connected to speed change transmission  41 , which may be manual or automatic. Rotary power from said transmission is forwarded sequentially to front universal joint  42 , propeller shaft  43 , rear universal joint  44 , pinion  45 , and differential  50  to rear drive wheels  51 . This is a popular layout for pickup trucks, SUV&#39;s, high performance cars and many luxury sedans. These vehicles may therefore retain their regular engines, transmissions and differentials, then be modified by installation of the hybrid cruiser system of this invention to achieve long distance travel capability with economical fuel cost. In effect this invention allows the owners to have it both ways: retain their much desired powerful original engine for fast acceleration, heavy towing, and high load carrying capacity, etc., and at the same time have a fuel efficient hybrid engine system with which to cruise economically over long distances. Furthermore, while long mileage is accumulated on the secondary engine, the primary engine is spared from excessive wear. 
   Further in  FIG. 2 , secondary engine  52  is mounted on chassis  40 . It delivers power to rear drive wheels  51  through a CVT system comprised of drive pulley  53 , drive belt  54 , driven pulley  55 , front jack shaft  56 , front small universal joint  57 , short propeller shaft  58 , rear small universal joint  59 , rear jack shaft  60 , rear jack shaft sprocket  61 , rear jack shaft chain  63 , and first transmission output shaft sprocket  64 . Power transmitted from secondary engine  52  to sprocket  64  is then further transmitted to transmission output shaft  65 , universal joint  42 , propeller shaft  43 , rear universal joint  44 , pinion  45 , and differential  50  to drive wheels  51 . 
   The vehicle is driven from a standing start to cruising speed by power from primary engine  39  transmitted through speed change transmission  41 , propeller shaft  43  and differential  50  to drive wheels  51  in the conventional manner. After cruising speed is attained, speed change transmission  41  is shifted to neutral, and primary engine  39  is run at idle speed, or stopped to conserve fuel. If it is stopped, means are provided to automatically restart it when additional power is needed, and speed change transmission  41  is engaged. Secondary engine  52  is then speeded up to transmit power to drive wheels  51 , through the CVT system and connections previously described, to keep the vehicle at cruising speed. When further power is needed to maintain the speed of the vehicle, a variable amount of electric power from battery  66  is transmitted to electric motor  67 , from which additional mechanical power is transmitted through motor sprocket  68 , motor chain  69 , and front jack shaft sprocket  70  to front jack shaft  56  upon which front jack shaft sprocket  70  is fixedly mounted. Thus, additional power from electric motor  67  is ultimately supplied to drive wheels  51  as needed to assist secondary engine  52  in maintaining the vehicle at the desired cruising speed. 
   When the vehicle needs to be slowed down or stopped, the kinetic energy of the vehicle can be converted to electricity through regenerative braking as used in most hybrid vehicles. For this purpose generator  71  is connected through generator sprocket  72 , generator chain  73  and rear transmission output shaft sprocket  74  to the transmission output shaft  65 . Thus, rotation of wheels  51  is transmitted through differential  50 , pinion  45 , rear universal joint  44 , propeller shaft  65 , thence through chain  73  and sprockets  74  and  72  to drive generator  71 . Electrical connections and other associated means and features used in the operation of the hybrid system are well known in the art and need not be described here. 
     FIGS. 3 and 4  illustrate an embodiment of the invention wherein the primary and secondary engines, the electric motor and generator are placed in the front part of the chassis in a front wheel drive vehicle. Primary engine  75  is coupled to the front drive wheels  76  via transaxle  77 , half shafts  78 , universal joints  79  and axles  80 . A transaxle is the combination of a speed change transmission and a differential, usually housed in a common casing. Power from primary (regular) engine  75  is first transmitted to the speed change transmission portion of transaxle  77  then to the differential  81  via internal pinion  82  which meshes with crown wheel  83  of differential  81  from which power is eventually transmitted through half shafts  78 , universal joints  79  and axles  80  to drive wheels  76 . Power from primary engine  75  is used to accelerate the vehicle from a standing start to cruising speed. 
   A unique feature of this embodiment is that transaxle  77  has been modified to have an external pinion  89  which also meshes with crown wheel  83  of differential  81 . This enables differential  81  to receive power from primary engine  75  via internal pinion  82  and to receive power from another source via external pinion  89 . 
   After the vehicle reaches cruising speed, transaxle  77  is shifted to neutral, thereby disengaging engine  75  from wheels  76  and placing the vehicle in a free wheeling state. Secondary engine  84  is then speeded up, causing drive pulley  85  to engage drive belt  86  and drive driven pulley  87 . Driven pulley  87  is fixedly mounted on jack shaft  88  so that, when secondary engine  84  is speeded up, the power transmitted to driven pulley  87  is transmitted via jack shaft  88 , rear universal joint  90 , external pinion  89 , crown wheel  88  differential  81 , half shafts  78 , side universal joints  79  thence to axles  80  and drive wheels  76 , thereby maintaining the vehicle at cruising speed. Meanwhile, primary engine  75  may be run at idle speed, or stopped, to conserve fuel. 
   When more power is needed to maintain cruising speed, electricity is drawn from battery  91  to drive electric motor  92  which then delivers mechanical power through motor sprocket  93 , drive chain  94  and rear sprocket  95  to jack shaft  88 , thence through universal joint  90 , to pinion  89 , differential  81  and eventually through the linkages shown to wheels  76  to assist in maintaining cruising speed. 
   While the vehicle is in motion, rotation of the wheels  76  is transmitted via axles  80 , differential  81  and external pinion  89  to jack shaft  88 . Rotation of jack shaft  88  is transmitted through front jack shaft sprocket  96  to generator chain  97  and generator sprocket  98 , thereby causing generator  99  to generate electricity for charging battery  91 . Other means and features used to maximize regenerative braking are well known in the art and need not be described here. 
     FIG. 5  illustrates a third alternative embodiment of the invention wherein primary engine  100 , secondary engine  101  and motor/generator  102  are placed in the rear instead of the front portion of the vehicle. The motor/generator  102  is a combination of an electric motor and a generator, and can be switched to function either as an electric motor or as a generator. In the motor mode, it produces mechanical power by drawing power from the battery  103 , and in the generator mode it uses engine power or regenerative braking to charge battery  103 .  FIG. 5  shows primary engine  100 , secondary engine  101 , motor/generator  102  and storage battery  103 , all mounted on chassis  104 . Power from primary engine  100  is transmitted to driving wheels  105  via transaxle  106  and axles  107 , and is used to accelerate the vehicle to cruising speed. Upon reaching cruising speed the transaxle  106  is shifted to neutral and the vehicle is maintained at cruising speed by power from secondary engine  101  supplemented as needed by power from motor/generator  102 . 
   In all the above embodiments an alternator may be used instead of a generator, and a starter/alternator may be used instead of a motor/generator. Furthermore a motor/generator may be substituted for the separate electric motor and separate generator described hereinabove. 
   For improved ease of operation, means can be provided for automatically shifting the mode of operation from one being powered by the primary engine to one powered by the secondary engine, and vice versa, as well as to various other combinations, using the electric motor as well. Such automatic shifting operations may be driven by impulses from a vehicular central computer unit utilizing streaming data input from engine speed sensors, vehicle speed sensors and engine load sensors, etc. The shift modes may be actuated through a commonplace cruise control unit. 
   For further improved ease of operation, the accelerator pedal for the primary engine may be modified to also serve as the accelerator pedal for the auxiliary engine and the electric motor, thereby avoiding the need to provide a separate accelerator pedal for each power source. The linkages for the accelerator pedal may be configured so that when the speed change transmission for the primary engine is in “drive” the accelerator pedal would be connected only to the primary engine, and the connections to the auxiliary engine and electric motor would be automatically disconnected. When the vehicle is running at a predetermined cruising speed and the speed change transmission is shifted to neutral the accelerator pedal would be automatically decoupled from the primary engine (which may be automatically stopped or run at idle speed to conserve fuel), and said pedal would be automatically coupled to the auxiliary engine and electric motor, and used to adjust the power produced for cruising. 
   For further fuel economy the auxiliary engine may be provided with starter means. The auxiliary engine may then be stopped when it is not in use to conserve fuel, then restarted and accelerated when needed to produce power for cruising. Alternatively, the auxiliary engine may simply be run at idle speed when not in use, yet still be automatically coupled to the accelerator pedal when called upon to produce power for cruising. 
   The accelerator pedal may be coupled to the electric motor in a manner which permits the motor to increase and decrease its power output at the same pace as the auxiliary engine, thereby adding to its power output. Their combined power make it possible to maintain the vehicle at the desired cruising speed with a reduced power output from the auxiliary engine itself, resulting in further reduction in fuel consumption. 
   Although the preferred embodiments are described in considerable detail, it is to be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention which is more fully defined in the appended claims.