DE19820638A1 - Arrangement of gear wheels to reduce tooth clearance - Google Patents

Abstract

Tooth clearance is reduced in an arrangement of gears comprising at least two gear wheels (42, 50, 100), such that the arc - shaped thickness (T50A) of the teeth one gear wheel is smaller than the arc - shaped thickness of the teeth of the other gear wheel. The teeth of first gear wheel are at least 0.005 cm larger than those of the second gear wheel. The number of teeth of the gears which mesh varies as a function of the force (DF1) acting against a spring pre-load which is applied to the gear wheels. Preferably, the flank width of the teeth of the first gear wheel is at least 50% larger than that of the teeth of the second gear wheel.

Description

The invention relates to gears and in particular, but not exclusively, the reduction of tooth play in gear drive ben.

If the tooth of one gear in the tooth gap of another Meshes, the tooth gap typically offers more Space than is needed to accommodate the tooth. This about The amount of space is sometimes referred to as "air" or "tooth play" net. Due to a number of factors, such as radial play in the Gear bearings, eccentricity of the gear shaft, imprecise axis Distance between the gears and size fluctuation of the gears Due to the manufacturing process, the backlash can fluctuate.

The excess of space associated with the backlash leads to habit Lich that the teeth of a gear a significant Subject to shock loads. This strain often creates strong noise and can cause other problems of a tooth lead wheel drive. For example, backlash can the gear ver increase wear. A reduction in the backlash is of of particular importance for applications within a combustion motor - especially for gear drives that are used at diesel engines be used. U.S. Patent Nos. 5,450,112, 4,920,828, 4,700,582, 3,523,003 are used here as examples for the users of gear drives in various motors.

Precise machining and assembly of the gears is essential a way to reduce backlash. This procedure however, is generally expensive and does not provide a solution for tooth play that changes over time due to wear Another approach to reducing backlash was the use of one or more scissor gears in the Gear drive. Scissor gears generally have teeth that face each other resize to the available space between Teeth of a paired gear. The U.S. patents  No. 5 056 613, 4 747 321, 4 739 670, 3 365 973 and 2 607 238 are here as examples of different types of Called scissors gears.

The adjustment of the backlash using a scissors gear is often limited when the scissors gear with two or more Gears are engaged, which are of different sizes Have play. Typically, the paired gear gives the smallest game the effective tooth size of the scissors tooth rades forward; however, this size is generally not sufficient to pair the larger game of the other ten gears. A possible solution to this problem is the selection of paired gears that the game sub minimize divisions, but this process of "game assignment" is typically expensive and time consuming. Hence there is further need for a gear drive arrangement, the Spielun different, with a scissors gear compensates for standing gears.

A particular scissor-gear arrangement has two toothed ones Wheels that are resiliently biased to relative to each other to rotate a common axis. For this arrangement gear teeth paired by each wheel spread to the avail space between the teeth of an adjacent gear to fill. In some gear drives, the load of the Pair of teeth through the adjacent gear to each pair of teeth align against the preload of the spring. Typically is each link of the aligned pair by dimensioning designed in the same nominal thickness, proportionately this bear high load. However, it was found that accidental Any deviations from the nominal value are usually sufficient, one Tooth or the other of each pair is disproportionate to let large part of the load carry until it is sufficient deformed to match the other tooth. This The deformation process often reverses the gear teeth directed bending loads, which make the teeth faster wear out as teeth, the non-directional bending bela are exposed. Such a deformation can also  cause larger tooth size differences and worse Performance and a louder gear drive. Therefore there is a need for a backlash gear arrangement, the one tolerates high loads without these disadvantages.

It was also found that the knocking sound was heavier Diesel engines, often attributed to the combustion process was caused by a loud impact noise from the gear teeth. Typically, this noise is caused by conventional arrangement not sufficiently reduced scissors gears. Thus, there is also a need for a gear drive, which this Sort of noise removed.

The present invention relates to game-reducing Gear assemblies and gear drives that have one or more use gear assemblies to reduce play.

According to one form of the invention, a gear drive is put together built by providing a first gear and a first engagement between the first gear and a second Gear is made. The second gear is a scissors tooth wheel with an effekti determined by the first intervention ve tooth size. A mounting position for a third gear chosen so that a second engagement with the second gear arises. This mounting position is determined depending on the effective tooth size to the backlash of the second one control handles.

In another form there is an engine system, the one Includes gear drive. This system includes a combustion motor, with the first, second and third gears rotatable are connected. The first gear meshes with the first gear with a first engagement, and the third gear meshes with that second gear with a second engagement. The second gear is a scissors gear. This system also includes one adjustable adjustment mechanism that has an adjustment range of Axis of rotation of the third gear relative to the axis of rotation of the second gear provides to the backlash of the second one  handles to control. An advantage of these forms of the invention is that the game difference between two gears that with comb a scissors gear, can be compensated. In another form of the invention is a game reducing Gear arrangement provided that a first gear that a first number of teeth arranged on the circumference, and has a second gear wheel with a spring preload engages in the first wheel around the first and second wheel an essentially common center of rotation relative to each other to turn. The second wheel has a number arranged on the circumference neter teeth, each with an associated one of the first Teeth match. Each pair of teeth has a composite Thickness corresponding to a force against the bias works. The first teeth each have a first arcuate thickness and the second teeth each have a nominally smaller arc shaped thickness than the first arcuate thickness. In general this difference in thickness shifts the load even more than the preload on the first wheel to the alternately directed Reduce bending loads.

In another form of the invention is a game reducing Gear arrangement such as a scissors gear with a high maximum preload torque executed to knock diesel eliminate motors. In general, this is for the Verrin of such noises required maximum preload torque depending on the respective engine version and the expected selected load. In a preferred embodiment becomes a maximum preload moment of at least about 135 Newton meters (100 foot-pounds) applied. In a preferred one Ren embodiment is a maximum bias torque of used at least about 270 Newton meters. In one more A more preferred embodiment is a maximum preload torque of at least about 675 Newton meters. Although it is in Contrary to the recognized level of knowledge, was highlighted found that this relatively high preload torque is undesirable Hammer or knocking noises of some diesel engines are reduced.  

In yet another form, a backlash-reducing tooth arrangement Proposed voltage that has a first gear on the Includes a first number of teeth and a second number of Keyways are arranged. This arrangement also includes a second gear, on the circumference of which a first number of teeth and a second number of keyways are arranged. The first and second keyways engage one another in one essential common axis of rotation and are related to this Axis inclined to the first and second wheel relative to each other to turn. The first and second teeth are paired to one To give the number of composite teeth that with a Dre hung of the first and second gear relative to each other Change size.

In another form it has a backlash gear arrangement a first wheel with a first number of on the circumference arranged teeth and a second gear that with a Spring preload engages the first and the first wheel the second wheel relative to one another about a common axis of rotation yielding to turn. The second wheel places a second number of teeth firmly, each with a corresponding one of the first wheel is paired to a number composed Variable thickness teeth to reduce backlash produce. In addition, an adjustment device is also included a threaded shaft carried by the first wheel and a head available. The head can optionally be relative to the first wheel be positioned opposite an adjustable storage generate the second wheel against the bias and ent speaking the alignment of the first and second teeth change. Preferably, the head has a position in the essentially aligns the first and second teeth around the To simplify installation of the arrangement in a gear drive.

Other forms of the invention combine the various inventions according to play-reducing gear assemblies in a tooth wheel drive and use the different according to the invention Gear drives with an internal combustion engine.  

Accordingly, it is an object of this invention the tooth play a gear drive drive comprising a scissors gear reduce order by matching a gear with the Scissors gear is engaged, one by one another intervention has certain effective tooth size.

Next is reducing that of a motor's gear drives emitted noises an object of this invention.

Another object of this invention is a game de gear arrangement, which the noise emission of tooth wheel drives reduced.

Another object is a backlash gear arrangement which reduces the noise emission by using a improved comparatively high preload torque.

Another object of this invention is load balancing between several gears of a scissors tooth to control wheel arrangement.

Another object is a reliable game changing gear arrangement that is easy to install.

Other objects, properties, advantages and points of view This invention will become apparent from the drawings and the description exercise can be seen.

Several embodiments of the invention are set out below explained in more detail with reference to schematic figures. It shows:

Fig. 1 is a front view of an engine system of a first embodiment of the invention,

Figs. 2 and 3 are plan views of components of a play-reducing gear assembly for the embodiment of Fig. 1,

Fig. 4 is a plan view of the game in a reducing gear built-in components 2 and 3 assembly of FIG. In a non-aligned state,

Fig. 5 is a spatial representation of the play reducing gear assembly of FIG. 4 in an aligned state,

Fig. 6 is a sectional view of a non-driven gear wheel and an adjustable Verstellmechanis mechanism taken along section lines 6-6 in Fig. 1,

FIGS. 7A and 7B are schematic front views of the system of Fig. 1 in different stages of assembly,

FIGS. 8A to 8C are schematic front views showing the selected flow stages constitute a part of the system of Fig. 1,

Figure 9 illustrates veran. A diagram showing various relationships of the sequence stages shown in FIGS. 8A-8C,

Fig. 10 is an exploded view of a play-reducing gear assembly according to alter native embodiment of this invention,

FIG. 11A is a plan view of the play reducing Zahnradanord voltage of FIG. 10 in the non-aligned state,

FIG. 11B is a side view of the play reducing gear assembly of FIG. 11A,

FIG. 12A is a plan view of the play reducing Zahnradanord voltage of FIG. 10 in the aligned state,

Fig. 12B is a side view of the play reducing gear assembly of Fig. 12A.

Fig. 1 shows an internal combustion engine system 20 according to the inven tion. The system 20 includes an engine block 22 with a ge dashed dashed crankshaft 24th The engine system 20 further includes a head assembly 30 connected to the block 22 . The head assembly 30 each contains an indicated ge injector camshaft 32 and a valve camshaft. In one embodiment, the block 22 and the head assembly 30 are designed as a large, 6-cylinder in-line utility diesel engine. However, the invention can also be used for other types of motors.

The system 20 includes a synchronizing gear 40 which includes a drive wheel 42 connected to the crankshaft 24 .

The crankshaft 24 and the drive wheel 42 have their center of rotation at the intersection of the cross lines designated 44. In the figures, to which reference is made here, centers of rotation are shown with a dashed line piece indicating the axis of rotation if the axis of rotation is not perpendicular to the plane of the drawing, and with cross lines if the axis of rotation is perpendicular to the plane of the drawing. The gear 42 rotates with the crankshaft 24 during the operation of the engine system 20 about the center of rotation 44 in order to drive the remaining toothed wheels of the gear drive 40 .

The gear 42 has teeth 46 which engage 48 with the lower non-driving backlash reducing gear 50 . The gear 50 rotates about the shaft 53 with the center of rotation 54 . The shaft 53 is fastened to the block 22 with fastening means 55 . A bearing 56 establishes a rotatable bearing relationship between the play-reducing gear arrangement 58 made of gear 50 and shaft 53 .

Fig. 2-5 provide further details of the structure and function of the play-reducing gear assembly 58 of the gear 50 is. With reference to FIG. 2, various details of the gear wheel 60 are shown prior to assembly into the gear assembly 58.

Gear 60 includes a hub 63 . A web 64 defines seven circumferentially spaced openings 65 . In addition, the web 64 defines for each opening 65 a finger-shaped edge 65 a at one end, which is opposite an edge 65 b at another end. The opening 65 and the edges 65 a, 65 b are distributed substantially uniformly over the circumference of an imaginary circle around the center 54 . The gear wheel 60 has a number of gear teeth 66 which are spaced apart from one another in the circumferential direction and are fixed by a wheel rim 67 . The wheel rim 67 is connected in one piece to the hub 63 by the web 64 . The adjacent links of the gear teeth 66 are separated from one another essentially evenly by tooth gaps 66 . For the sake of clarity, only a few of the teeth 66 and the tooth gaps 68 are designated. Each link of gear teeth 66 is substantially the same size and shape as the others. Similarly, each tooth gap 68 is of essentially the same size and shape.

Referring to FIG. 3, a gear 70 of the backlash-reducing gear assembly 58 is illustrated. Gear 70 includes a hub 73 that rotatably mates with shaft 53 via bearing 56 (see FIG. 1). The hub 63 of the gear 60 is in engagement with the hub 73 . The connection between the hubs 63 and 70 allows the gears 60 and 70 to rotate relative to each other. Gear 70 also includes a web 74 . Strips 74 a protrude from the web 74 substantially perpendicular to the plane of FIG. 3 and are with one side to form corresponding depressions 75 on the wheel rim 77 BEFE Stigt. A threaded bore 79 is formed at least by a strip 74 a. The bore 79 has a longitudinal axis which is essentially parallel to the plane of the drawing in FIG. 3. The web 74 also defines holes 75 a for weight reduction, one for each recess 75 . The strips 74 a and the recesses 75 are arranged substantially uniformly on the circumference of a ge-thought circle around the center 54 .

The wheel 70 comprises a number of gear teeth 76 formed by the wheel rim 77 . The wheel rim 77 is connected in one piece to the hub 73 by the web 74 . Adjacent members of the gear teeth 76 are substantially evenly separated from one another by tooth gaps 78 . For the sake of clarity, only a few of the teeth 76 and tooth gaps 78 are identified. Each of the gear teeth 76 is substantially the same size and shape as the others. Similarly, each tooth gap 78 is of substantially the same size and shape. Before preferably the number of teeth 76 of the wheel 70 is equal to the number of teeth 66 of the wheel 60 .

Fig. 4 explains the backlash gear assembly 58 in an out-of-alignment form, as is usually shown prior to preparation for installation in the gear drive 40 . In this arrangement, the wheels 60 and 70 are loosely engaged so that each opening 65 of the wheel 60 is substantially over a corresponding recess 75 of the wheel 70 to define a number of pockets 80 . A number of coil springs 81 are provided, each having an end 82 and an opposite end 84 . Each spring 81 is arranged in an associated pocket of the pockets 80 , the end 82 being engaged with an associated strip 74 a, and the end 84 being aligned with an associated edge 65 a. The ends 84 , however, are not typically engaged with the edges 65 a in this arrangement.

The assembly 58 also includes an adjustment bolt 90 having one with a threaded shaft 92 and an opposite head 94 . The shaft 92 is shown fully screwed into the bore 79 in FIG. 4, the head 94 being in contact with the associated strip 74 a. According to the usual convention, the teeth are tion 66 and 76 "non-aligned" in a Posi, so that the teeth 66, the tooth spaces 78 overlap between the teeth 76 and the teeth 76, the tooth spaces 68 Zvi rule the teeth 66 overlap. The hub 73 of the wheel 70 forms a rotatable bearing relationship with the hub 63 of the wheel 60 so that the wheels 60 and 70 can rotate relative to each other.

The head 94 defines a contact surface 95 for abutting against the edge 65 b of the wheel 60 when the wheel 60 is rotated counterclockwise relative to the wheel 70 . When the wheel 60 is rotated clockwise relative to the wheel 70 , the spring ends 84 are finally engaged with the associated edges 65 a. Each edge 65 a preferably has a finger which fits into the spiral of each spring 81 in order to simplify correct alignment with the wheel 60 . If they are turned clockwise with sufficient force, the springs 81 , as illustrated in FIG. 5, are compressed between the associated edges 65a and strips 74a .

FIG. 5 shows an "aligned" position of the gear wheels 60 and 70 , which reflects a compilation for installation in the gear drive 40 . Aligned to one another, the teeth 76 and 66 , as shown in FIG. 5, are approximately centered on one another. The springs 81 are located between the edges 65 a and the strips 74 a in a strongly compressed state and provide a correspondingly high spring force. The setting of the arrangement 58 from the compilation menstellung from Fig. 4 in the compilation from Fig. 5 is carried out by unscrewing the bolt 90 so that the head 94 away from the bore 79 along the shaft axis S. As long as this unscrewing continues, the surface 95 abuts the adjacent edge 65 b and the springs 81 are compressed between the adjacent, aligned strips 74 a and edges 65 a.

Unscrewing the bolt 90 spreads the associated Strei fen 74 a and the edge 65 b to rotate the wheels 60 and 70 relative to each other and to move the teeth 66 and 76 past each other. A given tooth 66 of the wheel 60 can migrate into and out of the overlap with a plurality of teeth 76 before the highly prestressed form of FIG. 5 is reached from the non-prestressed form of FIG. 4.

Fig. 5 also shows a surface 66 a of each tooth 66 of the wheel 60 , some of which are shown. Each tooth 76 of the wheel 70 has in the same way a surface 76 a, some of which are shown. A width W60 corresponds to the width of a typical surface 66 a. In the same way, a width W70 corresponds to the width of a typical area 76a . The width W60 is preferably smaller than the width W70. More preferably, the width W70 is at least 50% larger than the width W60. Most preferably, the width W70 is at least about twice the width W60.

Under common reference to Figs. 4 and 5, a play-reducing gear assembly 58 is produced by the wheel 70 and applying one of the springs 81 aligned with the bore 79. The bolt 90 is screwed into the bore 79 so that the head 94 touches the associated strip 74 a. The remaining springs 81 are arranged in the recesses 75 of the wheel 70 . The wheel 60 is arranged above the wheel 70 to form associated pockets 80 which are distributed substantially uniformly on an imaginary circle 86 (dashed line in FIG. 4). The ends 84 of the associated springs 81 are aligned with the edges 65 a.

Before mounting assembly 58 on shaft 53 , teeth 66 and 76 should preferably be aligned. To achieve this direction, the bolt 90 is partially rotated out of the bore 79 so that the head 94 touches the adjacent edge 65 b of the wheel 60 and compresses the spring 81 accordingly. As a result, teeth 66 and 76 move past each other. Unscrewing the bolt 90 continues this movement until the aligned position of FIG. 5 is substantially reached. As a result, as shown in FIG. 5, the wheel 60 is spaced from the wheel 70 along the shaft axis S by the distance D. It should be noted that part of the shaft 92 of the bolt 90 remains screwed into the bore 79 in both the non-aligned position of FIG. 4 and the aligned position of FIG. 5. In other embodiments, more than one or all of the strips 74 a can hold a bore 79 for interlocking with a bolt 90 . In the same way, a plurality of bolts 90 can be used in embodiments with a plurality of bores 79 .

Once teeth 66 and 76 are in the shape of FIG. 5, assembly 58 is secured to shaft 53 by bearing 56 . In this manner, the teeth 66 , 76 form an engagement 48 with the teeth 46 of the drive wheel 42 . However, the engagement 48 typically has a significant amount of play when the teeth 66 , 76 are forcibly aligned by the protrusion of the pin 90 . To take up this game with the gear 50 men, the wheels 60 and 70 are preferably allowed to rotate relative to each other under the influence of the bias of the compressed springs 81 . This rotation is made possible by screwing the bolt 90 back into the bore 79 after the assembly 58 is in engagement 48 with the drive wheel 42 . As a result, the spring bias shifts teeth 66 and 76 against each other to occupy substantially all of the space between adjacent teeth 46 involved in engagement 48 . It should be noted that the engagement 48 does not allow the teeth 66 , 76 to return to the unloaded position shown in FIG. 4.

Each pair of initially aligned teeth 66 , 76 functions together as a composite tooth with a variable effective size or "thickness" that depends on the space between the engaged teeth 46 . By changing the thickness, these composite teeth can reduce or even effectively eliminate the tooth play in the engagement 48 . To complete the installation of the assembly 58 , the bolt 90 should be tightened so that the head 94 bears against the associated strip 74 a. The bolt 90 is preferably carried by the wheel 70 during the entire adjustment process and the use of the arrangement 58 as part of the wheel 50 .

Preferably, the wheels 60 and 70 are made of a metallic material that is suitable for long use in a synchronizing gear drive of a diesel engine. It is also preferred that the pin 90 and springs 81 be selected from compatible materials that are suitable for long use in a diesel engine environment. Nonetheless, other materials may be used in other embodiments as would be apparent to those skilled in the art.

Although the gear 50 is illustrated in FIG. 1 as a non-driving gear, in other cases it may be configured as a driving wheel, a driven wheel, or otherwise adapted or modified as would be apparent to those skilled in the art. In all of these forms, the gear wheel 50 can be viewed as a new type of "scissor gear".

Referring again to FIG. 1, the gear 50 of the gear drive portion 40 and communicates with a non-driving gear 100 in engagement 96th The non-driving gear 100 rotates around the center of rotation 104 and has teeth 106 distributed on the circumference, which are separated by gaps 108 to form a handle 96 with the gear 50 .

With additional reference to FIG. 6, further details of the non-driving gear 100 are given. The non-driving wheel 100 comprises a wheel rim 107 , which determines teeth 106 and is integrally connected to a web 114 . The web 114 defines holes 116 for weight reduction. The web 114 is also integrally connected to a hub 118 which, as shown in the cross-sectional view of FIG. 6, has a slightly smaller thickness along the rotating axis corresponding to the center 104 than the wheel rim 107 . A cylindrical bushing 119 provides a rotatable bearing surface between a shaft 103 and the hub 118 . The shaft 103 defines four passages 105 for attaching the non-driven gear 100 to the block 22 .

The non-driven gear 100 is attached by an adjustable positioning mechanism 120 . The mechanism 120 includes a mounting plate 130 which is arranged between the shaft 103 of the non-driven gear 100 and the block 22 . It should be noted that the plate 130 is a clear distance from the hub 118 of the non-driven gear 100 such that the non-driven gear 100 can rotate freely about the shaft 103 .

The non-driven gear 100 and the mounting plate 130 are arranged between the block 22 and a retaining plate 140 . The retention plate 140 includes mounting holes 145 that are generally aligned with the mounting passages 105 of the shaft 103 , with mounting passages 135 of the plate 130, and with threaded holes 25 of the block 22 . It should be noted that the passages 105 have a larger dimension in an axis perpendicular to the axis of rotation of the gear 100 than the passages 135 , the holes 145 and the bores 25 . The non-driven gear 100 is secured between the plates 130 and 140 by inserting capped screw holders 150 through the holes 145 , the passages 105 and the passages 135 , and by screwing the ends of the threaded shafts 152 into the bores 25 . The holders 150 each have a head 154 which is opposite the threaded shaft 152 . The head 154 is so great that it contacts the retaining plate 140 when the shafts 152 are fully threaded into the bores 25 to the plate 140 to clamp against the shaft 153 and to clamp the shaft 153 against the plate 130th

In operation, the mechanism 120 positions the non-geared gear 100 relative to a flat area that is preferably parallel to the drawing plane of FIG. 1 and perpendicular to the drawing plane of FIG. 6. In this area, the gearwheel 100 can be positioned with a tolerance of 2 degrees, as symbolized in FIG. 1 by the direction arrows X and Y.

In order to attach the non-driven gear 100 , the mounting plate 130 is first attached to the block 22 with ordinary brackets (not shown) so that the passages 135 are aligned with the bores 25 . When the plate 130 is attached to the block 22 , the non-driven gear 100 is placed on the plate 130 so that the passages 105 overlap with the passages 135 . The plate 140 is then placed over the shaft 103 to place the holes 145 over the corresponding passages 105 and 135 and the bores 25 . The holder 150 are then each placed through an aligned hole 145 , a passage 105 and a passage 135 and loosely screwed into the corresponding bore 25 . Preferably, the holders 150 are initially screwed into the bores 25 far enough to contact the plate 140 and yieldingly hold the non-driven gear 100 in position. In this state, the position of the non-driven gear 100 relative to the plane area symbolized by the directional arrows X and Y can be selected within the distance specified by the clear distance between the holders 150 in the passages 105 . Once an XY position has been selected, the retainers 150 are tightened to secure the undriven gear 100 and mechanism 120 .

Teeth 106 of the non-driven gear 100 form an engagement 196 with the play-reducing gear 200 . Gear 200 is attached to injector camshaft 32 of head assembly 30 and can rotate about axis of rotation 204 . The gear 200 is preferably designed like the gear 50 , with composite gear tooth pairs, which are represented by the reference number 266 . Furthermore, the springs 281 of the toothed wheel of the 200 are shown which are designed in the same way as the springs 81 of the toothed wheel 50 , although there are fewer (three are shown). An adjustment bolt 290 is also shown, which for installation purposes can function in the same way as the bolt 90 of the gear wheel 50 . The gear 50 , gear, 200, or both can use Bellville rings to create a spring preload either with or without coil springs.

The gear 200 forms an engagement 296 with a paired gear 300 . The paired gear 300 is connected to the valve camshaft 34 and rotates about the center of rotation 304 . Gear 300 defines teeth 306 that cooperate with pairs of teeth 266 of gear 200 to form engagement 296 .

In operation, gear 42 rotates with crankshaft 24 to rotate gear 50 . As a result, the gear 50 rotates the non-driven gear 100 via the engagement 96 . The non-driven gear 100 drives the gear 200 via the engagement 196 and regulates the synchronization of the injection nozzles (not shown) of the engine system 20 by rotating the injection nozzle camshaft 32 . Further, gear 200 drives paired gear 300 via engagement 296 and rotates valve cam shaft 34 so as to synchronize the engine valves (not shown) of head assembly 30 . Thus, the sprocket 40 rotates the camshafts 32 and 34 of the head assembly 30 due to the rotation of the crankshaft 24 to synchronize the engine system 20 .

In other embodiments, a different number and different arrangement of gears may be used in the gear train 40 as would be apparent to those skilled in the art. In an alternative embodiment, an ordinary scissors gear can be used in place of gear 50 , gear 200 , or both. In still other embodiments, a non-driven gear with an adjustable positioning mechanism may not be required.

In one embodiment of the gear drive 40 , the number of teeth 46 for the gear 42 is approximately 48; the number of teeth 66 , 76 for the gears 60 , 70 about 70; the number of teeth 106 of the adjustable non-driven gear 100 is approximately 64; the number of composite teeth 266 of the gear 200 is approximately 76, and the number of teeth 306 of the gear 300 is approximately 76. Furthermore, the gears 42 , 50 , 100 , 200 , 300 in this form are spur gears and made of metallic material, which is suitable for long use with internal combustion engines, and generally have parallel axes of rotation which cross the drawing plane of FIG. 1 perpendicularly.

According to the description of selected structural and func tional features of the system 20 will now be described some aspects of the installation of the system 20 in conjunction with the specific matic drawings 7A and 7B, the reference sign schematically the structures represent, in FIGS. 1-6 are identified by the same reference numerals; however, the gear meshes have been enlarged to highlight selected features of this invention. At this stage, the drive gear 42 has been previously attached and rotates about the center 44 in the direction of arrow R1. In the same way, the meshing gear 300 has been attached and rotates about the center 304 in the direction of arrow R5.

After the gears 42 and 300 are attached, the gears of 50 and 200 are assembled to form an engagement 48 between gears 42 and 50 and an engagement 296 between gears 200 and 300 . The formation of the interventions 48 , 296 depends on the effective composite tooth size of the corresponding pairs of the teeth of the gears 50 and 200 , respectively, when they occupy the tooth gaps between the teeth 46 and 306 of the gears 42 and 300 , respectively. For the gear 50 , the teeth 76 of the wheel 70 are shown with broken lines; and the teeth 66 of the wheel 60 are shown with solid lines. The effective arcuate tooth thickness T50 of a composite pair of teeth of the gear 50 is also shown. This composite tooth strength is determined along the rolling circle of the tooth rack 50 for the engagement 48 . It should be noted that the thickness T50 is determined by the mating tooth gap of the teeth 46 of the gear 42 when the non-driven gear 100 is not present.

For the engagement 296 , the gear wheel 200 forms composite tooth pairs 266 . For clarity, each pair of teeth 266 has a link which is represented by a dashed line and a link which is represented by a solid line. The effective arcuate tooth thickness of a composite pair of teeth 266 is shown as an arcuate thickness T200 with respect to a rolling circle of the gear 200 .

Arrows R4, R5 indicate the direction of rotation in which the gear wheels of the 200 and 300 are driven. Also the fastening supply holes 25 of the engine block 22 are shown.

After setting the arcuate thickness T50 and T200, the non-driven gear 100 is installed and, as shown in FIG. 7B, forms the engagement 96 with the gear 50 and the engagement 196 with the gear 200 . The tooth thicknesses T50 and T200 are typically different, corresponding to a difference in the amount of backlash in the engagements 48 and 296 . By using the mechanism 120 for adjusting the XY position of the center of rotation 104 relative to the fixed centers of rotation 54 and 204 , the non-driven gear 100 can be arranged so that it meshes optimally with the predetermined tooth sizes of the gears 50 and 200 despite a play difference can. The holders 150 of the mechanism 120 are illustrated in FIG. 7B.

The adjustable position adjustment of the non-driven gear 100 relative to the other gears leads to a clear control of the amount of play in the engagements 96 and 196 . If the difference in backlash due to different widths T50 and T200 is within certain limits, the backlash can be reduced or even completely eliminated by arranging the non-geared gear 100 correctly along a flat area perpendicular to the axes of rotation of the meshing gears.

It should be noted that although the preferred embodiment shows two engagements 96 , 196 with the non-driven gear 100 , in other embodiments this type of assembly can be used to control the backlash of a different number of meshing gears. For example, this assembly technique is used in gear drives that have only three gears arranged similarly to gears 42 , 50 and 100 .

With reference to FIGS. 8A-8C, selected stages of the operation of the gear wheels 42 , 50 and 100 are shown schematically with reference signs which denote the same structures as in FIGS. 1-6; however, fewer and larger teeth are schematically illustrated in these drawings to highlight various properties. Referring to FIG. 8A, the gears 42 , 50 , 100 are in a static (motionless) position relative to each other. With reference to the engagement 48 imaginary rolling circles C1, C2, C3 of the respective gear wheels 42 , 50 , 100 are shown with broken lines. The arcuate thickness T50a of a pair of gear teeth 76 , 66 of gear 50 is shown as an arc along the accompanying rolling circle C2. The arrows DF1 represent the forces acting against the pre-tension of the gear 50 under the static conditions shown in FIG. 8A. The static counter forces of the gear 100 are shown by the arrows RF1. Also shown is the arcuate thickness T60 of a selected tooth 66 and the arcuate thickness T70 of a selected tooth 76 . Preferably, the arcuate thickness T60 is nominally less than the arcuate thickness T70 of each of the teeth 60 , 70 . In a preferred embodiment, T60 is at least about five thousandths (0.005) of a centimeter smaller than T70. More preferably, this difference is at least about 10 thousandths (0.010) of a centimeter. Most preferred is a range between five to fifteen thousandths (0.005-0.015) of a centimeter.

In Fig. 8B, gear 42 rotates in the direction indicated by arrow R1 and provides a resultant driving force, which is shown by arrow DF2. As a result, gear 50 rotates in the direction indicated by arrow R2 and gear 100 rotates in the direction indicated by arrow R3. The resulting counterforce of the gear 100 is represented by an arrow RF2 Darge. The resulting forces DF2 and RF2 are sufficiently large to partially overcome the spring preload and to compress the springs 81 of the gear 50 . As a result, the arcuate thickness T50b of the composite tooth pairs of the gear 50 decreases relative to the thickness T50a (T50b is smaller than T50a). As the magnitude of the force transmitted by the drive wheel 42 increases, the teeth 66 , 76 continue to transition to the aligned state.

In Fig. 8C, the resulting driving force DF3 of the gear 42 and the counter force RF3 of the gear 100 compress the spring 81 enough to align the gear teeth 66 and 76 . Oriented in this way results in a composite thickness T50c. T50c is smaller than both T50a and T50b and is substantially equal to the arcuate thickness T70 of tooth 76 . In the state of Fig. 8C, springs 81 are substantially completely compressed; they store an essentially equal amount of energy as the springs 81 in the state of FIG. 5.

The narrower arcuate thickness of teeth 66 compared to teeth 76 (T60 <T70) prevents loading of teeth 66 beyond the load applied by the compressed springs of FIG. 8C. In contrast, teeth 76 carry any load beyond the load of the springs. Limiting the load on the teeth 66 to the spring preload causes a reduction in the backward bending load that conventionally results from random size differences of the pairs of teeth, each link nominally the same size. Preferably, the wider head flank W70 of each tooth 76 carries the driving force that exceeds the spring preload; however, the total increase in width (W60 + W70) for gear 50 is typically less than the increase in width required to withstand the backward bending loads from a scissor gear having the same nominal thickness for all teeth.

Fig. 9 graphically shows with a load line 400 the typical effect of the reduced arcuate thickness T60 compared to the arcuate thickness T70. The broken line 400 represents the gear 60 and the solid line 400 represents the gear 70. A horizontal section 410 corresponds the bias of the gear 50 under the static conditions of FIG. 8A. A sloping portion 420 corresponds to the load on teeth 66 , 76 between the static condition of FIG. 8A and the aligned position of FIG. 8C. FIG. 8B corresponds to a point on the portion 420. When the load compresses the springs 81 to align the teeth as illustrated in FIG. 8C, the load on the teeth 66 of the gear 60 flattens to the maximum load of the springs 81 , as shown in a section 430 . At the same time, the thicker surface W70 of teeth 76 carries the high load, as shown by an inclined portion 440 . By letting the wheel 70 absorb the high loads and limiting the load on the wheel 60 with the arcuate thickness difference (T70-T60), backward bending loads are typically reduced.

It has been found that much of the unwanted noise associated with heavy duty diesel engines, such as e.g. B. the "hammer" noises, caused by loud impact noises of the gear drives associated with these motors. An unexpectedly large change in the noise behavior, typically associated with an overall reduced noise level, is observed when a relatively high preload torque is applied with a scissors gear arranged in the gear drive. Here, "preload torque" stands for the size of the torque delivered by a spring-loaded scissors-gear arrangement. The preload torque depends on the size of the cross product of the vectors, which correspond to a radial distance from the center of rotation of the gear wheel to the teeth and a force that acts tangentially on a circle with a corresponding radius. Typically, the preload torque changes depending on the load of the scissors gear preload. Preferably, the pretensioning moment is maximum when the gear teeth are aligned against the pretension in the union. For the aligned state of the teeth 66 , 76 in FIG. 5, a radial vector T and a force vector F are illustrated, which can be used to determine the pre-tensioning torque of the arrangement 58 .

It has been found that a maximum pretensioning torque of at least 135 Newton meters (Nm) creates improved noise properties and lower noise levels. A maximum preload torque of at least about 270 Nm is more preferred. Most preferred is a maximum preload torque of at least about 675 Nm. In a most preferred embodiment, gear 50 is provided with a maximum preload torque of approximately 945 Nm, and gear 200 is equipped with a maximum preload torque of approximately 270 Nm. In many cases, the biasing torque of this invention eliminates the need to use expensive enclosures or covers to attenuate unwanted noise.

Fig. 10 shows an exploded view of a play-reducing gear assembly 558 about the rotational axis 554 in accordance with another embodiment of this invention. The assembly 558 includes a gear 560 with splines 561 formed by the inner cylindrical surface 564 of the hub 563 . The hub 563 forms an opening 563 a passing through it. The key grooves 561 are directed helically around the center 554 and are inclined relative to the axis of rotation of the wheel 560 . The hub 563 is integrally connected to the web 564 . A number of teeth 566 arranged on the circumference are fixed by a wheel rim 567 , which is also connected in one piece to the web 564 . The teeth 566 are arranged substantially equally spaced from one another around the center 554 and are of essentially the same size and shape. Between the adjacent teeth 566 there are tooth gaps 568 , which are likewise arranged at substantially the same distance from one another and have essentially the same size and shape. The web 564 of the wheel 560 defines two opposing openings 569 .

The assembly 558 also includes a wheel 570 . The wheel 570 has keyways 571 defined by the outer cylindrical surface 572 of the hub 573 . The keyways 561 run helically around the center 554 and are inclined relative to the axis of rotation of the wheel 570 . The keyways 571 are inclined in substantially the same way as the keyways 561 to be able to engage therein. The hub 573 fits into the opening 563 a of the hub 563 to allow the keyways 561 and 571 to engage. The hub 573 has an opening 573 a, which is surrounded by an inner cylindrical surface 574 to form a rotatable bearing relationship with a mounting shaft. The wheel 570 also includes a land 574 which is integrally connected to the hub 573 . Teeth 576 are fixed by a wheel rim 577 , which is connected in one piece to the web 574 . The teeth 576 are substantially equally spaced from one another about the center of rotation 554 and each is of substantially the same size and shape. Teeth 576 define tooth gaps 578 between them. The tooth gaps 578 are substantially equally spaced from each other and each is of substantially the same size and shape. Together the hub 573 , the web 574 and the wheel rim 571 define a cylindrical recess 575 . The web 564 defines two threaded recesses 579 , each of which corresponds to an opening 569 .

In the recess 575 coil springs 581 are each net angeord, which are located at substantially the same distance from each other around the center 554 and between the hub 573 and the wheel rim 577 . There are adjusting devices 590 a, 590 b, each of which has an adjusting bolt 590 with a threaded shaft 592 . The shaft 592 has an end 593 opposite a head 594 . The devices 590 a, 590 b each contain a washer 596 through which the shaft 592 fits. In contrast, the head 594 is so large that it does not fit through the washer 596 . In addition, the outer diameter of the washer 596 is so large that it does not fit through the opening 569 . The opening 569 is so large that the shaft 592 has ample clearance and a selected arrangement of the shaft 592 is possible therein. The threaded recesses 579 are each designed to engage a corresponding shaft 592 .

Referring to FIG. 11A, an unaligned arrangement of assembly 558 is illustrated showing teeth 566 and 576 of wheels 560 and 570 , which, similar to the embodiment illustrated in FIG. 4, do not overlap. With additional reference to FIG. 11B, a side view of assembly 558 is illustrated in an unaligned state. The keyways 561 of the wheel 560 engage the keyways 571 of the wheel 570 . On each device 590 a, 590 b, the shafts 592 have corresponding shaft axes S1, S2 running in the longitudinal direction. The shafts 592 are pushed through corresponding washers 596 and openings 569 to initially engage in a corresponding de-threaded depression 579 . In the state of Figs. 11A and 11B, springs 581 are not substantially compressed.

With additional reference to FIGS. 12A and 12B, a perspective view and a side view of the assembly 558 are illustrated, each in an aligned state. This aligned state corresponds to the aligned state of the arrangement 58 illustrated in FIG. 5. In order to align the arrangement 558 , the shafts 592 of the adjusting devices 590 a, 590 b are screwed further into the recesses 579 in order to compress the springs 581 between the wheel 560 and 570 . When the springs 581 are compressed, the bevels of the intermeshing keyways 561 , 571 produce a ramp movement which converts the translational movement of the devices 590 a, 590 b into a substantially rotary movement of the wheels 560 , 570 . When the shafts 592 of the devices 590 a, 590 b are unscrewed, the compressed springs 81 generate a force which turns the wheels 560 and 570 in the opposite direction due to the intermeshing of the keyways 561 , 571 . The arrangement 558 is designed so that the teeth 566 and 576 are substantially aligned when the shafts 592 are completely screwed into the recesses 579 . This aligned state of assembly 558 is also preferably made to produce a selected maximum preload torque. The distance that the wheels 560 and 570 occupy along the shaft axis S1 and S2 changes from D1 in the non-aligned position of FIG. 11B to D2 in the aligned position in FIG. 12B, where D1 is greater than D2. It should be noted that D2 is the minimum distance that the wheels 560 , 570 of the assembly 558 occupy along the shaft axes S1, S2. Thus, the wheels 560 , 570 rotate relative to each other depending on the distance that the wheels 560 , 570 take along an axis of rotation corresponding to the center 554 .

Preferably, the number of teeth 566 is the same as the number of teeth 576 . Also preferably the number of helical splines 561 , 571 is the same as the number of teeth 566 , 576 . The same number of teeth and keyways simplifies assembly because it is not necessary to mark keyways 571 , 561 to ensure that the alignment of teeth 566 and 576 matches a strong spring compression. In other embodiments, the recess 569, in contrast to the essentially circular opening shown in FIG. 10, can be designed as a non-circular opening. In another embodiment, the recess 569 is designed as an arcuate slot, the bending radius of which extends from the center 554 .

The keyways 561 , 571 can be arranged at different locations next to the hubs 563 , 573 . As a non-limiting example, arcuate slots defined by one wheel may have an inner surface that defines keyways that engage keyways formed by a flange that projects into these slots from the other wheel. It should be noted that one or more segments of interlocking keyways arranged about the axis of rotation can allow the relative rotation of the gears without having to enclose the axis.

Similar to the embodiment of the assembly 58, the assembly 558 includes an alignment device for selectively aligning teeth of two gears of a backlash-reducing gear assembly by counteracting the spring bias of the assembly. To the aligned state of FIGS. 12A and 12B to reach for the installation are tightened the shafts 592nd If the arrangement 558 is in engagement with another gear, for example with the gear 42 , the shaft 592 of each device 590 a, 590 b is released in order to allow a relative rotation of the wheels 560 and 570 and to take up the play of the meshing gears . This disengaged arrangement would appear similar to the state of FIGS. 11A and 11B, but would preferably provide clearance between the head 594 and washer 596 of each bolt 590 to accommodate the changing play conditions of a corresponding engagement. In one embodiment, devices 590 a, 590 b are removed when assembly 558 is installed in engagement with another gear. In this embodiment, one can rely on the engagement to counteract the bias.

Each assembly 58 , 558 has a threaded shaft adjuster that is coupled to a wheel and extends along a shaft axis. These devices also include a head connected to the shaft, which is adjustable relative to the wheel. In essence, devices 58 and 558 can be made interchangeable with other features of this invention. Furthermore, the arrangement 58 or 558 can be adapted for use with the gear 200 to reduce play. In other embodiments of the assemblies 58 , 558 , the bolts 90 , 590 may be replaced by a threaded shaft which is attached to one of the wheels with a nut screwed thereon to form a movable head. This nut is positioned along the shaft to selectively engage the other wheel. In still further embodiments of this invention, no backlash arrangement is used. In fact, in some possible embodiments of this invention, an ordinary scissor gear arrangement can be used.

Claims (45)

1. Gear arrangement to reduce backlash, with
a first gear that has a first number of teeth arranged on the circumference;
a second gear that engages the first gear with a spring bias to rotate the first and second gears relative to each other about a substantially common center of rotation, the second gear having a second number of teeth on the periphery, each with a corresponding ones of the first teeth are paired to form a number of composite teeth which change size depending on a biasing force; and
wherein the first teeth each have a first arcuate thickness and the second teeth each have a second arcuate thickness, and the first thickness is at least about 0.005 of a centimeter (0.002 inch) greater than the second thickness. 2. Gear arrangement according to claim 1, wherein the first teeth a first flank width and the second teeth one each have a second flank width and a minimum of the first flank width is at least about 50% larger than the second flank width. 3. Gear arrangement according to claim 1 or 2, with a mini difference between the first and second arches Thickness of at least about 0.010 centimeters. 4. Gear arrangement according to claim 1 or 2, with a mini difference between the first and second arcuate thickness in a range of about 0.010 to 0.015 centimeters. 5. Gear arrangement according to one of claims 1-4, wherein the Spring preload at least a preload moment of about 135 Newton-meters related to a radius from the turning center the first and second teeth are generated when the first and second teeth are substantially aligned.   6. Gear arrangement according to one of claims 1-5, further with an alignment device on the first wheel to the first and second teeth for installation against the preload optionally align. 7. System with a gear drive arrangement, with
a first gear having a number of teeth that define a number of tooth gaps between them; and
a second gear that meshes with the first gear and has two toothed gear wheels in a backlash-free arrangement, which have a number of pairs of teeth each having a first tooth from one of the wheels and a second tooth from another of the wheels to form a composite tooth form and engage in an associated one of the tooth gaps, wherein the first tooth has a first arcuate thickness and the second tooth has a second arcuate thickness that is nominally smaller than the first arcuate thickness. 8. The system of claim 7, further comprising
a third gear meshing with the second gear;
a fourth gear that meshes with the third gear and is a scissors gear; and
a fifth gear that meshes with the fourth gear. 9. System according to claim 7 or 8, wherein a nominal minimum difference between the first and second arcuate thickness of at least 0.005 centimeters consists. 10. System according to any one of claims 7-9, further comprising
an internal combustion engine having a crankshaft, a first camshaft and a second camshaft;
a third gear meshing with the second gear;
a fourth gear that meshes with the third gear and is a scissors gear;
a fifth gear that meshes with the fourth gear; and
in which the first gear is attached to the crankshaft, the second gear is driven by the first gear, the third gear is driven by the second gear, the fourth gear is driven by the third gear and is attached to the first camshaft , The fifth gear is driven by the fourth gear and is attached to the second camshaft so that it rotates, and a nominally minimal difference between the first and second arcuate thicknesses is at least 0.010 centimeter. 11. Procedure comprising the steps

• (a) providing a first gear wheel, having a first number of teeth arranged on the circumference, each having a first arcuate thickness;
• (b) selecting a second gear, having a second number of circumferential teeth, each having a second arcuate thickness that is nominally less than the arcuate thickness; and
• (c) assembling the first and second gear wheels to a backlash gear assembly after selection.

12. The method of claim 11, wherein a minimal sub distinguished between the first and second arcuate thicknesses of is at least about 0.005 centimeters. 13. The method of claim 11, wherein a minimal sub distinguished between the first and second arcuate thicknesses of is at least about 0.010 of a centimeter. 14. The method of claims 11-13, further comprising the Align the first and second teeth for installation in one Gear drive. 15. The method according to any one of claims 11-14, wherein the Assembly inserting a number of coil springs contains between the first and second wheels to a spring to generate tension.   16. The method of claim 15, wherein the coil spring Preload torque generated by at least about 135 Newton meters. 17. Tooth play reducing gear arrangement, with
a first gear wheel having a first number of circumferential teeth;
a second gear wheel that engages the first wheel with a spring bias to yieldably rotate the first and second wheels relative to each other about a substantially common axis of rotation, the second wheel determining a second number of circumferential teeth, each are paired with the corresponding one of the first teeth to form a number of composite teeth, each of which changes size depending on the biasing force;
wherein the spring preload generates a maximum preload torque of at least 135 Newton meters in relation to a radius from the center to the first and second teeth. 18. Gear arrangement according to claim 17, wherein the first Teeth each have a first flank width and the second teeth each have a second flank width, the first flan width at least 50% larger than the second flank width is. 19. Gear arrangement according to claim 17 or 18, further with a bolt with a threaded shaft opposite a head, wherein the threaded shaft is screwed into a bore, the is determined by one of the first or second wheels, and the Head optionally into the other of the first and second wheels intervenes in a bearing relationship to counter the preload act and essentially the first and second teeth for the Align installation. 20. Gear drive arrangement, with
a first gearwheel with a number of teeth which determine a number of tooth gaps between; and
a second gearwheel with two toothed gearwheels which engage in one another in a play-reducing form and defines a number of paired teeth, at least one of which engages in a corresponding one of the tooth gaps, the wheels rotating relative to one another about a substantially common axis of rotation, and wherein the second gears a maximum pretensioning torque of at least about 135 Newton meters related to a radius from the center to the pairs of teeth he testifies. 21. Gear arrangement according to claim 20, further with
a third gear meshing with the second gear;
a fourth gear that meshes with the third gear and is a scissors gear; and
a fifth gear that meshes with the fourth gear. 22. Gear arrangement according to claim 20, further comprising
an internal combustion engine having a crankshaft, a first camshaft and a second camshaft;
a third gear meshing with the second gear;
a fourth gear that meshes with the third gear and is a scissors gear;
a fifth gear that meshes with the fourth gear;
the first gearwheel being attached to the crankshaft, the second gearwheel being driven by the first gearwheel, the third gearwheel being driven by the second gearwheel, the fourth gearwheel being driven by the third gearwheel and being attached to the first camshaft in a rotating manner, and the fifth gear is driven by the fourth gear and is attached to the second camshaft so that it rotates. 23. Gear arrangement according to one of claims 17-22, in which the maximum preload torque is at least about 270 Newton meters is. 24. Gear arrangement according to one of claims 17-22, in which the maximum preload torque is at least about 675 Newton meters is.   25. A method of assembling a gear drive comprising the steps

• (a) providing a first gear wheel;
• (b) arranging a first engagement between the first gear and a second gear, the second gear being a scissors gear with an effective tooth size determined by the first engagement;
• (c) selecting a mounting position for a third gear to form a second engagement with the second gear after placement, the mounting position being determined depending on the effective tooth size to control the backlash of the second engagement.

26. The method of claim 25, wherein the selecting one Change the mounting position of the third gear with an adjustable adjustment device, which includes a Turning the third gear around an axis of rotation and an adjustment len on a substantially flat area that approx runs perpendicular to the axis of rotation. 27. The method according to claim 25 or 26, wherein the scissors assembly of the second gear includes a gear pair of springs connected to a spring preload to determine a number of gear pairs of teeth that are in spring relationship and each have a composite tooth width has an effective arcuate thickness that changes depending on the first procedure and with the steps of

• (b1) pressing against the spring bias to align each pair of gear teeth;
• (b2) engaging the second gear with the first gear during pushing to form the first engagement; and
• (b3) Holding the push after the engagement to allow the size of the pairs of teeth to be adjusted in accordance with the first engagement.

28. The method according to claim 27, comprising the steps of

• (d) rotatably mounting the third gear in the mounting position;
• (e) engaging a fourth gear with a fifth gear to form a third engagement, the fourth gear being a scissors gear;
  wherein the arranging includes rotatably mounting the first and second gears to form the first engagement, and wherein the selecting includes changing the mounting position of the third gear with an adjustable adjustment assembly that allows the third gear to rotate about and about an axis of rotation essentially flat area is adjustable perpendicular to the axis of rotation.

29. Engine system, with

• (a) an internal combustion engine;
• (b) a first gear rotatably connected to the motor to rotate about an axis;
• (c) a second gear rotatably connected to the motor to rotate about a second axis and engage the first gear in a first engagement, the second gear being a scissors gear;
• (d) a third gear rotatably connected to the motor to rotate about a third axis and engage the second gear in a second engagement; and with
• (e) an adjustable adjustment mechanism that allows a number of positions of the third gear relative to the second gear to control the backlash of the second gear.

30. The system of claim 29, further comprising
a fourth gear rotatably connected to the motor for engaging the third gear in a third engagement and which is a scissors gear;
a fifth gear that engages the fourth gear in a fourth engagement; and
wherein the adjustable adjustment mechanism continues to position the third axis relative to the fourth gear to control the backlash of the third engagement. 31. The system of claims 29 or 30, wherein the third Gear contains a shaft, with a pair of thereby mounting passages, and in which the adjustable Adjustment mechanism a pair of threaded holders contains, each one by a corresponding one of the through let it fit. 32. System according to any one of claims 29-31, wherein the Mecha nism an adjustment relative to a level approximately lower right to the first, second and third axes Area allows. 33. System according to one of claims 29-32, wherein the motor includes a crankshaft to which the first gear is attached is to turn the crankshaft and the second Gear to rotate, and in which the second gear is the third Gear drives. 34. Backlash gear arrangement, with

• (a) a first gear having a first number of circumferential teeth;
• (b) a second gear meshing with the first gear with spring bias to yieldably rotate the first and second wheels relative to each other about a substantially common axis of rotation, the second gear defining a second number of teeth, each paired are with a corresponding tooth of the first gear to form a number of composite teeth, each of a variable size to reduce the backlash when they are in engagement; and with
• (c) an adjuster having a threaded shaft connected to the first wheel and a head connected to the shaft, the head having a first selectable position for bearing relationship with the second wheel against the spring preload form to align the first and second teeth for installation.

35. Gear assembly according to claim 34, wherein the head has a second selectable position to the first and second Wheel a relative rotation to each other at about the preload after the arrangement has been installed to allow using to comb another gear. 36. Gear assembly according to claim 35, wherein the pre direction contains a bolt with the shaft and the head, and the first wheel defines a threaded hole, and at least part of the shaft is screwed into the bore around the Position the head between the hole and the second wheel. 37. Gear assembly according to claim 36, wherein the head touches the second wheel in the first position, and the first Touched the wheel in the second position. 38. Gear assembly according to claim 34 or 35, in which
the first wheel defines a threaded bore and has a first hub that defines a first number of spiral splines;
the second wheel defines an opening that covers the threaded bore and has a second hub that defines a second number of spiral splines, the first splines and the second splines interlocking; and
the device includes a bolt that has the stem opposite over the head and a washer, the stem extending through the washer and the opening to screw-in to grip the bore and optionally the washer and the second wheel between the head and the tension the first wheel in position. 39. Gear arrangement according to one of claims 34-38, at which the spring preload a maximum preload torque of at least about 135 Newton-meters related to a radius of the axis of rotation to the first and second teeth, wherein the first teeth each have a first arcuate thickness and the second teeth each have a second arcuate thickness,  and the first thickness is at least 0.005 centimeters larger than that second thickness is. 40. Gear arrangement for reducing tooth play, with
a first gear having a first number of circumferential teeth and a first number of keyways;
a second gear having a second number of circumferential teeth and a second number of splines, the first and second splines intermeshing about a substantially common axis of rotation and slanting relative to the axis about the first and second wheels to rotate with each other, and wherein the second teeth are each paired with a corresponding tooth of the second teeth to produce a number of composite teeth that change in size when the first and second wheels rotate relative to each other. 41. Gear assembly according to claim 40, wherein the first and second wheels mesh and a preload that at least partially by means of interposed screws which is applied, each one essentially for Apply parallel force to the axis of rotation. 42. Gear assembly according to claim 41, further comprising a Adjustment device which is carried by the first wheel and the first and second teeth against the bias optionally can align. 43. Gear assembly according to claim 42, wherein the pre direction a bolt with a threaded shaft opposite the Contains head. 44. Gear arrangement according to one of claims 41-43, at which the maximum preload torque is at least about 135 Newton meters related to a radius that is from the axis of rotation runs to the first and second teeth, the first Teeth each have a first arcuate thickness and the second teeth  each have a second arcuate thickness, and the first thickness is at least about 0.005 centimeters larger than that second thickness. 45. Gear arrangement according to one of claims 40-44, which the first wheel has a first hub which the first Keyways, and the second wheel has a second hub, which determines the second keyways, and where the together set teeth change their size according to the distance, that of the first and second wheels along the axis of rotation is taken.