Abstract:
A portable dynamometer includes a frame, an axle rotatably mounted on the frame, and a flywheel secured to the axle. An endless loop drive mechanism connects the axle and the output shaft of the engine to be tested. A ring gear drivingly attaches to the axle and an automotive starter connects to the ring gear to start the axle and engine turning. Various position-adjustable mounting pad assemblies can be mounted on the frame to hold different sizes and types of engines. The whole dynamometer can be tipped on end to facilitate testing of engines with vertical output shafts. A caliper brake mounts on the frame and decelerates the flywheel. Other methods of warming up and loading the engine are also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority based upon United States Provisional Application Ser. No. 60/108,929, filed Nov. 16, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to inertia flywheel assemblies of dynamometers used for testing of automotive drive train components, including motors and clutches. 
     A number of conventional automotive vehicle dynamometer systems are available to test automotive components. However, many of these systems are large and stationary. These large test assemblies must be connected to permanent sources of electricity and hydraulics to operate. 
     Portable dynamometer test assemblies have been devised to overcome the limitations of stationary test assemblies. However, even these portable test assemblies are limited in the number of different types of tests they can perform. Some portable dynamometer test assemblies must directly replace the final component in the vehicle&#39;s drive train in order to take the necessary measurements. This is not always desirable. Existing dynamometer test assemblies also cannot run tests on engines and clutches (clutch slip and engagement rpm) with substantially the same setup. A completely different test setup or massive changeover of the test stand is generally required for testing other components or variables in addition to the usual motor efficiency or performance tests. A relatively small, flexible and portable flywheel test stand or dynamometer would be very useful in testing small engines and clutches such as those found in go-karts and the like. 
     Therefore, a primary objective of the present invention is the provision of a portable flywheel assembly for a dynamometer which can be used to test the horsepower and torque of an engine. 
     Another objective of the present invention is the provision of a flywheel assembly for a dynamometer which is economical to manufacture, easily transportable, and simple to use. 
     Another objective of the present invention is the provision of a flywheel assembly for a dynamometer which is versatile and can be used in many applications with minimal changeover time. 
     Another objective of the present invention is the provision of a flywheel assembly for a dynamometer which can test components in a vertical or horizontal orientation. 
     Another objective of the present invention is the provision of a dynamometer that uses an automotive type starter to automatically start the engine to be tested in either direction of rotation by rotating the dynamometer axle, which is in turn connected to the output shaft of the engine. 
     Another objective of the present invention is the provision of a flywheel assembly for a dynamometer which can utilize standard data acquisition systems. 
     These and other objectives will become apparent from the drawings, as well as from the description and claims which follow. 
     SUMMARY OF THE INVENTION 
     This invention relates to a flywheel test assembly or dynamometer disposed on a portable table. An axle is rotatably supported in the table. The axle is drivingly connected with a sprocket hub assembly and a flywheel mounted thereon. A ring gear is mounted for rotation on the axle in spaced relation to the flywheel. 
     The unit to be tested mounts on a mounting plate which can be secured to the top or side of the table. An endless loop drive mechanism interconnects the axle and the engine being tested. A chain or belt drivingly connects a driven sprocket or pulley hub assembly with the unit to be tested. The sprocket or pulley hub assembly can be moved to various locations along the axle. The table can also be pivoted ninety degrees. These features allow the flywheel test assembly to easily adapt to and test units having either horizontal or vertical output shafts. Setup or changeover efforts are kept to a minimum. 
     The flywheel test assembly also utilizes an automotive-type starter system in which the starter motor engages a ring gear attached to the axle. Thus, when the starter motor turns the ring gear, the flywheel, the sprocket hub assembly, and therefore the engine are driven. 
     The flywheel test assembly of this invention is extremely flexible and allows drive train systems and components, including engines and clutches, to be tested using basically the same setup. Various measures of engine performance can be documented and plotted using computerized data acquisition equipment. Furthermore, various measures of clutch performance, such as any type of drive train system slippage, can be documented. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the portable dynamometer of this invention. 
     FIG. 1A is a perspective view similar to FIG. 1, but shows the mounting rack flipped over or rotated end-for-end. 
     FIG. 2 is a sectional view of the dynamometer taken along line  2 — 2  in FIG.  1 . 
     FIG. 3 is a sectional view taken along line  3 — 3  in FIG.  1  and is similar to FIG. 2, but shows an alternative embodiment wherein the dynamometer includes four bearings and a one-way clutch is interposed between the two innermost bearings. 
     FIG. 4 is a perspective view of the dynamometer of this invention tipped over on its end and configured to test an engine with a vertical output shaft. 
     FIG. 5 is a sectional view of the dynamometer taken along line  5 — 5  in FIG.  4 . 
     FIG. 6 is a partial end elevation view showing an engine having a horizontal output shaft mounted on a wedge attached to the mounting plate of the dynamometer so as to simulate the angled mounting conditions often found in go karts. 
     FIG. 7 is a partial side elevation view of the lower portion of one of the dynamometer table legs and shows how an optional bumper pad assembly pivotally mounts to the legs. 
     FIG. 8 is a sectional view similar to FIG. 2, but shows an alternative arrangement for warming up or loading the engine. 
     FIG. 9 is a graph of acceleration horsepower and rpm versus time in seconds from a performance test of a motor. 
     FIG. 10 is a graph of the drive ratio and engine rpm versus distance in feet resulting from clutch slip. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An automotive vehicle for the purposes of this invention is considered to be any self-powered vehicle and includes, but is not limited to, motorcycles, motor cars, trucks, go-karts, snowmobiles, all-terrain vehicles, water craft, aircraft, and scale models. The power plants of such vehicles can include, but are not restricted to, an internal combustion engine, an electric motor, a turbine, and/or a flywheel. 
     In FIGS. 1-3, the major components of the inertial dynamometer flywheel test assembly  10  of this invention are shown. A table  12  sits on a support surface  13  and rotatably supports an axle  14 . The axle  14  is drivingly connected to a. flywheel  16 . The position of the flywheel  16  on the axle  14  is slidably adjustable in the axial direction. 
     A sprocket hub assembly  18  is mounted for rotation with the axle  14 . Like the flywheel  16 , the sprocket hub assembly  18  is slidably adjustable in an axial direction. The sprocket hub assembly  18  includes a sprocket  18 A or pulley wheel mounted on the axle  14 . Assembly  18  and  18 A can also be replaced with an axle clutch assembly. An appropriate endless loop means  18 B, such as a chain or drive belt, drivingly connects the unit to be tested  20  to the sprocket hub assembly. See FIG.  2 . 
     Referring again to the axle  14 , spaced apart bearings  22 A,  22 B rotatably support each end with respect to the table  12 . An additional bearing  22 C is disposed between the sprocket hub assembly  18  and the flywheel  16 , inwardly of the outer bearings  22 A,  22 B. 
     A flywheel starter ring gear assembly  26  comprises a ring gear  27  mounted on a support plate which is connected to the axle  14  by a centering hub  32 . The hub  32  centers and supports the starter ring gear  27  and the support plate on the axle  14 . A plurality of spacers  30  may interconnect the flywheel  16  and ring gear assembly  26 , thus operatively mounting the flywheel  16  on the axle  14 . 
     A starter motor  34  selectively drivingly engages the ring gear  27  to rotate the flywheel  16 , the axle  14 , and thereby the unit to be tested  20 . The starter motor  34  selectively engages with the starter ring gear  27  when a key switch or solenoid  38  is activated. The switch could be an electrically activated switch or solenoid assembly. In the preferred embodiment, the test assembly  10  utilizes an automotive-type starling system. A battery  36  is grounded to the table 12 by a cable  40 , and a positive cable  42  extends to the solenoid  38  and then to the starter motor  34 . By reversing its polarity, the starter motor  34  can rotate the ring gear  27  (and thereby the output shaft of the engine  20 ) in either direction, as needed. 
     FIG. 2 shows that the unit to be tested  20  is a motor or engine mounted to the top of the table  12  with its horizontal output shaft extending toward the flywheel  16 . 
     As best seen in FIGS. 1-3, a caliper brake  44  mounts on the table  12  adjacent the flywheel assembly  16 . The caliper brake  44  is hydraulically operated and selectively engages the flywheel  16  to stop its rotation. The brake  44  can also load the engine  20  under test by decelerating the flywheel without completely stopping it. The caliper brake  44  includes brake pads  43 ,  45  arranged on either side of the flywheel  16  to frictionally engage it. 
     The unit to be tested  20  is secured and supported on a mounting plate  46 . The mounting plate is slidingly supported by three rails  48 A,  48 B,  48 C which extend generally perpendicular to the axle  14 . 
     The table 12 has a plurality of normally upright legs  50  which support a pair of spaced apart longitudinal members  52  and a plurality of cross members  54  that interconnect the longitudinal members  52  as shown in FIG.  2 . One or more reinforcing members  56  can optionally extend between the legs  50  to provide additional stability as shown in FIG.  1 . For the sake of simplicity, the reinforcing members  56  have been omitted from the other figures. 
     As best seen in FIGS. 1-3, the mounting rails  48 A,  48 B, and  48 C are spaced apart in a particular way. The distance between the center of rail  48 B and  48 C is approximately  3  inches. This spread corresponds to the American standard for motors  20  in the 0-40 horsepower range. An American motor mount wing member  58  threadedly engages the bottom of the motor mount plate  46  and engages or clamps against the lower side of the rails  48 B and  48 C to secure the plate  46  in the desired location. On the other hand, the distance between the centers of the rails  48 A and  48 B is approximately 3½ inches. This distance corresponds to the International motor mounting standards. An International motor mount wing member  60  threadedly engages or clamps against the underside of the plate  46  and the rails  48 A,  48 B to secure the plate  46  in the desired location. The center rail  48 B is shared by both the International and American mounting systems. 
     FIG. 6 illustrates another variation of the invention wherein a wedge-shaped motor mounting fixture  46 B can be provided. This provides a standardized cart rail system, which is used worldwide for testing go-kart engines. The wedge  463  is angled because kart engines are generally mounted on the right rear frame rail and the fuel tank and carburetor must be elevated to clear the right rear tire. 
     In other applications a rectangular block-shaped mounting plate  46 A is used. The mounting plate  46 A is shown in greater detail in FIG.  4 . The plate  46 A is designed to be universal and hold a variety of different types of units to be tested  20 . The mounting plate  46 A has a round aperture  62  extending vertically therethrough for receiving the output shaft of the unit to be tested  20  when the output shaft is oriented vertically. The mounting plate  46 A also has a plurality of perpendicular slots  64  which extend through the mounting plate  46 A and radially outward from the aperture  62 . The slots  64  allow the unit  20  to be secured to the mounting plate  46 A by conventional fasteners. The elongated slots  64  provide adjustment and flexibility so as to allow accurate placement of the unit to be tested  20 . 
     One skilled in the art can appreciate that a plurality of individual threaded mounting holes can be used instead of the aperture and slot configuration when the unit to be tested  20  is placed on the mounting plate  46  with its output shaft in a horizontal orientation, as shown in FIGS. 1-3. Most original equipment manufacturers for small engines use the same motor mount or bolt pattern so that their engines will be interchangeable and fit almost all equipment designed for that engine size. For example, vertical engines (sizes 8 horsepower to about 12.5 horsepower) will fit on almost all riding mowers. Plate  46  will be laser cut to accept most OEM bolt patterns so that most engines will bolt on very easily. 
     As best seen in FIG. 2, the bearing  22 A is mounted to the underside of the left cross member  54 . Meanwhile, a second bearing  22 B is mounted to the underside of the right cross member  54 . A third bearing  22 C is mounted on the intermediate cross member  54  between the other bearings  22 A,  22 B. The bearing  22 C is also interposed between the sprocket hub assembly  18  and the starter ring gear assembly  26 . This arrangement rotatably supports the axle  14  at three or more spaced apart points along its length. 
     FIG. 3 shows another embodiment in which a fourth bearing  22 D is mounted to one or more intermediate cross members  54 . A one-way clutch or sprag-type bearing  66  is provided between the two intermediate bearings  22 C and  22 D. The one-way clutch  66  allows the flywheel  16  to be disengaged from the unit under test  20  should a catastrophic failure occur. In that event, the flywheel  16  will merely coast to a stop and therefore prevent further damage from being done to the engine, the drive system, or the test stand. 
     The bearings  22 A,  22 B,  22 C, and  22 D rotatably support the axle  14  with respect to the table  12 . Preferably, these bearings  22 A,  22 B,  22 C,  22 D are of the cast pillow block style, but other styles of bearings can be used without detracting from the invention so long as they are durable, reliable and have sufficient load-bearing capacity. 
     FIG. 3 also shows that the starter ring gear assembly  26  and starter  34  can be located on the other side of the sprocket hub assembly  18 , remote from the flywheel  16 . 
     Conventional safety shields  17  are preferably installed so as to cover the flywheel  16 . Additional shielding (not shown) is also desirable around the sprocket hub assembly  18  and the area around the chain or belt  18 B. 
     The flywheel test assembly  10  can be provided with a computerized data acquisition system (not shown). Sensors for speed, temperature, and other variables of interest can be placed in operative proximity to the motor output shaft and the flywheel  16 . Of course, any information that a data acquisition system or computer could collect through the sensors would be useful in analyzing any part of the engine  20  or the kart drive train system. 
     The present invention can best test motors or engines in the zero to 40 hp range, but it can also be adapted to larger engines. In operation, the flywheel test assembly  10  can test a motor or engine  20  with a horizontally disposed output shaft as follows. The motor  20  is removed from the vehicle and mounted on the mounting plate  46 . The endless loop means  18 B is connected to the output shaft, preferably by a sprocket or pulley mounted thereon. The sensors should be in place on the motor output shaft and the flywheel  16  or axle  14 . Optional sensors could also measure fuel pump pressure, exhaust temperature, engine vacuum, or other system attributes. Once the setup of the test stand is completed, the ignition key switch  38  is activated to engage the starter ring gear assembly  26  with the starter motor  34 . The starter motor  34  turns the starter ring gear assembly  26 , which in turn rotates the axle  14  and the flywheel  16 . The axle  14  starts the motor  20 , turning with the sprocket hub drive assembly  18 . 
     The versatility of the dynamometer  10  allows any number of ways to be used to warm up and or load the engine  20 . The caliper brake  44  can frictionally engage the flywheel  16  to load the motor  20  and speed up the warm-up process. The flywheel itself acts as the rotor for the brake  44 . Once warm-up has been achieved, plots of acceleration horsepower and engine rpm versus time (in seconds) can be generated by quickly and steadily increasing the engine rpm from a low value to a high value. FIG. 9 shows a typical plot. 
     The changeover or conversion of the flywheel test assembly  10  from a configuration capable of testing engines  20  with horizontal output shafts to a configuration capable of testing engines  20  with vertical output shafts is quite simple. As best seen in FIGS. 4 and 5, the flywheel test assembly  10  is merely rotated 90 degrees so that the legs  50  remote from the flywheel  16  become the top of the table 12. The legs  50  adjacent the flywheel  16  then rest on the floor or supporting surface  13 . The sprocket hub drive assembly  18  is moved along the axle  14  to a position where it is engageable with the output shaft of the engine  20 . Of course, a mounting plate  46 A can be provided on the upper legs  50 . FIG. 4 shows the mounting plate  46 A secured to the legs  50  for testing a vertical shaft engine  20 . 
     An elongated member  68  having a J-shaped cross-section rigidly mounts to the legs  50  so as to form a channel for slidingly receiving the edge of the mounting plate  46 A. The mounting plate  46 A has threaded holes adjacent each of its corners. The elongated J-shaped members  68  have an elongated slot  70  therein that accommodates the shanks of screws  72 , which are inserted into the holes in the mounting plate  46 A. Thus, the mounting plate  46 A can be slidably positioned in the channels between the legs  50  and the J-shaped elongated member  68 . 
     The mechanism  74  for adjusting the position of the mounting bracket or plate  46 ,  46 A is most clearly shown in FIG. 4, but is also generally shown in FIG.  1 . The mechanism  74  enables quick and accurate adjustment of the tension on the endless loop chain or belt  18 B. The mechanism includes a crank arm  76  that drivingly connects to a rod  78  having coarse Acme threads thereon. The rod  78  extends through a threaded hole in a member  80  that is fixed on the legs  50  (FIG. 4) or fixed to the plate  82  at the end of the mounting rails  48 A,  48 B,  48 C (FIG.  1 ). The end of the rod  78  opposite the crank arm  76  has no threads and extends through a bore in the end of a hollow coupling member  84  that is fixed, preferably welded to the mounting plate  46 ,  46 A as shown. A pin locked in place by a set screw  86  extends into the coupling member  84  and engages an annular groove in the rod  78  so that the plate  46 ,  46 A moves with the rod  78  in both directions, but the rod  78  rotates freely in the coupling member  84 . 
     Various drive train components can be tested on the dynamometer of this invention. One such component is a clutch on an engine  20 . The clutch slippage, expressed as a distance in feet, can be plotted versus engine rpm and drive ratio, as shown in FIG.  10 . 
     As previously discussed, the placement of a one-way clutch  66  between the sprocket hub assembly  18  and the flywheel  16  on the axle  14  helps prevent damage in the event of engine failure. The one-way clutch  66  operatively disengages one portion of the axle  14  from the other portion of the axle  14  so that the flywheel  16  can coast freely to a stop. See FIG.  3 . 
     In FIG. 7, an optional floor-gripping end for the legs  50  is shown. The floor-gripping bumper assembly  88  includes an L-shaped bracket  90  that is pivotally mounted to the lower end of the leg  50 . One or more resilient rubber pads  92  are rigidly fastened to the bottom of the bracket  90 . The pads  92  frictionally engage the supporting surface  13  and thereby help keep the dynamometer in place during operation. The pads  92  also assist in dampening vibrations. 
     Other alternatives can be utilized to load or warm up the engine  20  or associated kart drive train components. The caliper brake can be supplemented or even replaced altogether by a hydraulic load circuit, a water brake system, or an electrical load circuit Thus, the engine  20  or other kart drive train components can be tested at an exact desired operating temperature or the load on the engine can be varied to determine its effect on the failure rate of the component. For example, FIG. 8 shows an embodiment in which the dynamometer includes a clutch  94  that selectively disconnects the flywheel  16  from the axle  14 . An additional bearing  22 E rotatably supports the axle  14 . The alternative loading means  96 , such as described above and illustrated by the “black box” in FIG. 8, is operatively attached to the portion of the axle  114  that remains connected to the engine  20 . A Lovejoy coupling or another clutch  98  connects the alternate loading/warm-up means  96  to the ring gear assembly  26  and the engine  20 . Thin arrangement provides a means of warming up the engine  20  without having to overcome the high inertia of the flywheel  16  at startup. For startup, the warn-up load can be kept to a minimum Then the load can be gradually increased to raise the temperature of the engine  20 . The clutch  94  connects the flywheel  16  to the engine when the desired temperature has been reached. 
     Thus, it can be seen that the present invention at least achieves its stated objectives. 
     In the drawings and specification there has been set forth preferred embodiments of the invention, and although specific terms are employed, these are used in a generic and descriptive sense only and not for purposes of limitation. Changes in the form and the proportion of parts as well as in the substitution of equivalents are contemplated as circumstances may suggest or render expedient without departing from the scope of the following claims.