Patent Application
20080026899
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
Turning to
As illustrated in
The drive-receiving opening 65 is part of the input side 105 of the transmission 20. A first bushing 115 is positioned within the first portion 95 of the housing 60, and a second bushing 120 is positioned in the second portion 100 of the housing 60. The first bushing 115 and second bushing 120 cooperate to support a fixed portion 125 of a primary pulley 130.
The fixed portion 125, shown in
Returning to
In some constructions, a biasing member (not shown) is positioned to bias the movable portion 155 away from the fixed portion 125. For example, one construction employs a coil spring between the fixed portion 125 and the movable portion 155 that biases the movable portion 155 away from the fixed portion 125.
With continued reference to
As shown in
The flange 220 includes a first surface 230 that surrounds the ramps 225, and a second surface 235 opposite the ramps 225. The second surface 235 abuts the bushing flange 205 to inhibit movement of the upper wedge 185 toward the first portion 95 of the housing 60. Several apertures 240 extend through the flange 220 and several alignment tabs 245 extend from the flange 220.
The adjusting collar 195, shown in
The lower wedge 190 includes a central aperture, a plurality of ramp portions, and a lower surface 270 opposite the ramp portions. The central aperture is sized to closely fit over the bushing 180 to allow free rotation of the lower wedge 190 with respect to the bushing 180. The ramp portions correspond with and engage the ramp portions 225 of the upper wedge 185 such that rotation of the upper wedge 185 with respect to the lower wedge 190 causes the ramp portions to slide on one another and changes the axial distance between the second surface 235 and the lower surface 270. In some constructions, anti-friction material is applied to the ramp portions 225 to reduce the sliding friction between the lower wedge 190 and the upper wedge 185.
The lower surface 270 is coupled to the adjustment boss 165 such that axial movement of the second surface 235 produces a corresponding axial movement of the adjustment boss 165 and the movable portion 155. Because the axial position of the second surface 235 is substantially fixed, rotation of the upper wedge 185 with respect to the lower wedge 190 produces axial movement of the lower surface 270 in an axial direction. As illustrated in
The output side 110 of the transmission 20 includes the driven shaft 75, the output pulley 80, and a secondary pulley 275. The first portion 95 of the housing 60 includes a first boss 280 that extends from the housing 60 along the driven shaft axis, and includes a second boss 285 that extends in the opposite direction. The first boss 280 and the second boss 285 cooperate to define an opening. Bushings 290 fit within the first boss 280 and the second boss 285 to support the driven shaft 75 for rotation.
The secondary pulley 275 includes a secondary fixed portion 295, a secondary movable portion 300, and a biasing element 305. The secondary fixed portion 295 includes a pulley portion 310 that defines a frustoconical surface 315, and includes a shaft portion 320 that supports the pulley portion 310 and abuts one of the bushings 290 to inhibit axial movement of the secondary fixed portion 295. In preferred constructions, the secondary fixed portion 295 includes a steel shaft portion 320 and an integrally-cast aluminum pulley portion 310.
The secondary movable portion 300 includes a collar portion 325, and includes a pulley portion 330 that defines a frustoconical surface 335. The collar portion 325 supports the pulley portion 310 and defines a cylindrical aperture 340 that fits over the shaft portion 320 to allow axial movement of the secondary movable portion 300 with respect to the secondary fixed portion 295. The frustoconical surface 315 of the secondary fixed portion 295 cooperates with the frustoconical portion 335 of the secondary movable portion 300 to define a second V-shaped slot 345. Movement of the secondary movable portion 300 produces a corresponding variation in the width of the second V-shaped slot 345. Anti-friction material or a sleeve-type bushing may be located between the cylindrical aperture 340 and the shaft portion 320 of the fixed portion 295.
A locking cap 350 engages the driven shaft 75 and sandwiches the shaft portion 320 of the secondary fixed portion 295 between the locking cap 350 and the bushing 290 to inhibit movement of the secondary fixed portion 295 with respect to the driven shaft 75. The biasing member 305 engages the locking cap 350 at one end and the secondary movable portion 300 at the other to bias the secondary movable portion 300 toward the secondary fixed portion 295.
Operation of the transmission 20 will now be described with continued reference to
The crankshaft is coupled to the shaft portion 145 of the fixed portion 125 of the primary pulley 130 such that the fixed portion 125 of the pulley 130 rotates with the crankshaft. As discussed, the crankshaft or another shaft may extend below the transmission to drive a pulley 150 that drives other components such as one or more mower blades. Alternatively, the crankshaft or another shaft could directly drive the other components or mower blades.
The movable portion 155 of the primary pulley 130 is coupled to the shaft portion 145 of the fixed portion 125 such that the movable portion 155 is substantially free to move axially along the axis of rotation, but is not free to rotate relative to the fixed portion 125. As such, the fixed portion 125 and the movable portion 155 rotate in unison. In one construction, one or more axial-extending grooves, formed in one of the fixed portion 125 and the movable portion 155, engages one or more corresponding guides formed in the other of the fixed portion 125 and the movable portion 155. In still other constructions, a spline is formed in the shaft portion 145, and the movable portion 155 includes a spline-receiving aperture that allows for axial movement and facilitates the transfer of torque between the fixed portion 125 and the movable portion 155. In some constructions, anti-friction material or a bushing may be positioned between the movable pulley portion 155 and the fixed shaft portion 125.
The V-shaped slot 170 defined by the fixed portion 125 and the movable portion 155 receives the primary belt. The primary belt is V-shaped such that it engages the two frustoconical surfaces 140, 160 of the fixed portion 125 and the movable portion 155. When the movable portion 155 is in a first position, the space between the fixed portion 125 and the movable portion 155 is such that the primary belt engages the primary pulley 130 near the axis of rotation. When the movable portion 155 is in a second position, the space between the fixed portion 125 and the movable portion 155 is such that the primary belt is forced outward and engages the frustoconical surfaces 140, 160 at a second position further from the axis of rotation.
The biasing member (if employed) biases the movable portion 155 away from the fixed portion 125, toward the first position and maintains contact between the adjustment boss 165 and the spacer 200. The upper wedge 185 and the lower wedge 190 are arranged such that their ramp surfaces engage one another and they are positioned between the spacer or spacers 200 and the bushing 180. The adjustment collar 195 attaches to the upper wedge 185 such that rotation of the adjustment collar 195 produces a corresponding rotation of the upper wedge 185. As the upper wedge 185 rotates in a first direction, the ramp surfaces 225 of the upper wedge 185 move with respect to the ramp surfaces of the lower wedge 190 to move the lower wedge 190 toward the pulley 130. Downward movement of the lower wedge 190 produces a corresponding movement of the movable portion 155 toward the fixed portion 125. When the upper wedge 185 rotates in the opposite direction, the biasing member biases the lower wedge 190 upward to maintain contact between the ramp surfaces. Thus, the movable portion 155 moves away from the fixed portion 125.
When the adjustment collar 195 is in the first position, the movable portion 155 is spaced from the fixed portion 125 such that the primary belt rotates near the axis of rotation. In this position, the belt rotates at a first speed. As the adjustment collar 195 rotates in the first direction, the movable portion 155 moves toward the fixed portion 125 to force the primary belt outward. At its most outward position, the primary belt rotates at a second speed that is higher than the second speed.
The primary belt also engages the secondary pulley 275 such that the secondary pulley 275 rotates in response to the rotation of the primary pulley 130. The secondary pulley 275 includes frustoconical surfaces 315, 335 similar to those of the primary pulley 130 that engage the primary belt such that the secondary pulley 275 rotates in response to rotation of the primary pulley 130. The secondary pulley 275 includes a secondary movable portion 300 that moves with respect to the secondary fixed portion 295. The secondary movable portion 300 moves to maintain the tension of the primary belt. For example, when the adjustment collar 195 is in the first position, the primary belt is positioned near the axis of rotation of the primary pulley 130. To maintain the desired tension in the belt, it is desirable that the primary belt be spaced away from the axis of rotation of the secondary pulley 275. As the adjustment collar 195 rotates in the first direction, the primary belt moves outward, away from the axis of rotation of the primary pulley 130. As the belt moves outward, the belt tension increases. The increased tension produces a separating force that acts on the secondary movable portion 300 in opposition to the biasing member 305 and moves the secondary movable portion 300 away from the secondary fixed portion 295 to allow the belt to move closer to the axis of rotation of the secondary pulley 275. In this way the overall length of the belt as well as the belt tension remain constant without the use of an idler pulley or other belt tensioner.
For a fixed engine speed, the primary pulley 130 rotates at the same fixed speed. However, the linear speed of the primary belt varies with its distance from the axis of rotation. Thus, if the diameter at which the primary belt engages the primary pulley 130 is doubled, the linear distance the primary belt must travel for a given rotation of the primary pulley 130 must double. This results in a doubling of the belt speed. Thus, by moving the primary belt outward, the transmission is able to move the primary belt at a faster linear speed which results in a higher rotational speed of the secondary pulley 275.
Furthermore, the described arrangement allows for a greater variation in the rotational speed of the secondary pulley 275 with respect to the primary pulley 130. For example, for a fixed engine speed the primary pulley 130 rotates at the same fixed speed. However, the linear speed of the primary belt varies with its distance from the axis of rotation. Thus, if the diameter at which the primary belt engages the primary pulley 130 is doubled, the linear distance the primary belt must travel for a given rotation of the primary pulley must double. This results in a doubling of the belt speed.
The secondary pulley 275 is coupled to the output pulley 80 such that the output pulley 80 rotates at the same speed as the secondary pulley 275. The transfer belt 85 extends from the output pulley 80 to the differential pulley 90 to provide an input to the differential 25.
The control system 30 illustrated in
As illustrated in
The control rod 360 is a substantially elongated cylindrical rod that includes a first end 400 that defines an aperture 405. The hook portion 390 fits within the aperture 405 such that linear movement of the rod 360 along its long axis is transferred to the link arm 355, while the control rod 360 remains substantially free to rotate slightly with respect to the link arm 355.
The control bracket 375 includes an interface surface 410, a side surface 415, and two support ears 420 that extend from the side surface 415. Each support ear 420 includes an aperture 425 through which the control rod 360 passes. The apertures 425 may include bearings (e.g., bushings, journal bearings, linear bearings, roller bearings, etc.) that support the control rod 360 for both rotation and axial movement.
The interface surface 410 extends from the side surface 415 and is spaced apart from the support ears 420. The interface surface 410 defines an interface aperture 430 that includes three substantially parallel paths 435a, 435b, 435c and one transverse path 440.
As illustrated in
The control system 30 also includes a transfer link 445 that includes a first portion 450, a pair of ears 455 extending from the first portion 450, and a tab 460 extending from the first portion 450 in a direction substantially opposite the ears 455. The ears 455 define apertures 465 that receive the control rod 360 such that the transfer link 445 is supported for pivotal movement about the control rod 360. The tab 460 extends through an aperture 470 formed in the sidewall 415 of the control bracket 375 as illustrated in
The operator link 370 defines an aperture 475 that facilitates the attachment of the operator link 370 to the transfer link 445. A pin 480 or other attachment member extends through the aperture 475 to pivotally attach the operator link 370 to the transfer link 445, while inhibiting relative non-pivotal movement between the operator link 370 and the transfer link 445. The operator link 370 also includes a first end 485 disposed above the interface surface 410 in a position that allows the user of the lawn tractor 10 to manipulate the operator link 370, and a second end 490 coupled to the control collar 365. Thus, movement of the operator link 370 in a first direction substantially parallel to the control rod 360 produces a corresponding movement of the control collar 365 and control rod 360 in an opposite direction. However, movement of the operator link 370 in a direction transverse to the control rod 360 produces a pivoting movement of the transfer link 445 about the control rod 360. The pivoting motion produces a similar arcuate motion of the tab 460.
With reference to
In operation, the control system 30 is operable to both vary the output speed of the transmission 20 and to shift the differential 25 between the first speed range, the second speed range, and the third speed range. With reference to
It should be noted that the angular travel of the adjusting collar 195 and the axial travel of the upper and lower wedges 185, 190 is sufficient to disengage the primary belt from the primary pulley 130. Thus, when the operator link 370 is near or in the transverse path 440, the transmission 20 is in a neutral mode as there is no belt tension. This allows for the easy shifting of the gears within the differential 25 without the need for a clutch.
In the construction illustrated in
As shown in
A first support shaft 545 is supported by the housing 515 for rotation and extends out one side of the housing 515 to define an exposed portion 550. The shaft 545 includes two slots 555 that extend along the length of the shaft 545 for at least a portion of the length. In preferred constructions, bearings are disposed at either end of the shaft 545 to support the shaft 545 for smooth rotation. A brake disk 560 is attached to the exposed portion 550 and can be used to slow or stop movement of the lawn tractor 10 as is known in the art.
Four gears are supported by the shaft 545 and are free to rotate about the shaft 545 but are fixed axially to inhibit movement of the gears along the length of the shaft 545. A first or reverse bevel gear 565 is disposed near the exposed portion 550 of the shaft 545. A second or low-speed range spur gear 570 is positioned adjacent the reverse bevel gear 565 on the side opposite the exposed portion 550 of the shaft 545. A third or forward bevel gear 575 is disposed adjacent the low-speed range spur gear 570, and a fourth or high-speed range spur gear 580 is positioned adjacent the forward bevel gear 575 and near the second end of the shaft 545 away from the exposed portion 550. Each of these gears 565, 570, 575, 580 is free to rotate about the shaft 545. Thus, the input bevel gear 540 engages both the forward bevel gear 575 and the reverse bevel gear 565 such that the forward bevel gear 575 rotates about the shaft 545 in a first direction, while the reverse bevel gear 565 rotates about the shaft 545 in a second direction opposite the first direction.
A shift collar 585 is positioned on the shaft 545 and is coupled to the fork 505 such that movement of the fork 505 produces a corresponding axial movement of the collar 585 along the shaft 545. Two shift keys 590 are positioned within the shaft slots 555 such that a first end of each shift key 590 is fixedly coupled to the collar 585. The second ends of the shift keys 590 include a gear engaging boss 595 that, when properly positioned, couples one or more of the gears 565, 570, 575, 580 to the shaft 545 for rotation.
In
In an intermediate or third position (slot 435b), illustrated in
As illustrated in
When the control system 30 is in the first position (
The third spur gear 600 is fixedly attached to the second shaft 605 and is similar in size to the second spur gear 580. As such, there is little or no speed reduction between the first shaft 545 and the second shaft 605 and the second shaft 605 rotates in a forward direction when the control system 30 is in the first position.
When the control system is in the second position (
The fourth spur gear 610 is larger than the first spur gear 570, thus producing a second stage of speed reduction. Thus, when the control system 30 is in the second position, the second shaft 605 rotates at a speed that is slower than the first shaft 545 and rotates in a reverse direction.
When the control system 30 is in the third position (
When the third spur gear 600 is being driven by the second spur gear 580, the fourth spur gear 610 must rotate with the second shaft 605 as they are fixedly attached to one another. However, since the first spur gear 570 is not engaged, it is free to rotate about the first shaft 545 at any speed. Similarly, when the fourth spur gear 610 is driven by the first spur gear 570, the third spur gear 600 must rotate with the second shaft 605. However, the ability of the second spur gear 580 to freely rotate about the first shaft 545 inhibits binding of the transmission 20.
The fifth spur gear 615, positioned near one end of the second shaft 605, engages a ring gear 620 that is supported substantially coaxially with a pair of axles 625. No matter which gear 600, 610 causes the rotation of the second shaft 605, the rotation rotates the fifth spur gear 615, which rotates the ring gear 620. As illustrated, the ring gear 620 is larger than the fifth gear 615, thereby producing a third stage of speed reduction (second stage if the control system 30 is in the first position). The ring gear 620 includes spur gear teeth on an outer surface of a ring that defines a substantially hollow ring interior 630.
In some constructions, the ring gear 620 includes a shoulder 635 (
Two axles or shafts 645 extend toward one another along the axis of the ring gear 620 within the ring interior 630 and support two ring bevel gears 650 for rotation. Each of the ring bevel gears 650 is rotatably attached to one of the shafts 645 such that the ring bevel gears 650 are free to rotate about or with their respective shafts 645. In most constructions, bearings support the bevel gears 650 on the shafts 645 within the ring gear 620 to facilitate smooth reduced friction rotation.
The two axles 625 extend from the housing 515 and support wheels 655 (shown in
Each axle 625 supports an axle bevel gear 665 disposed at the inner most end and engaged with the ring bevel gears 650. In the illustrated construction, the axle bevel gears 665 are substantially the same size as the ring bevel gears 650. Of course other sizes and gear types are possible.
The ring bevel gears 650 rotate with the ring gear 620, but do not rotate about the ring gear shafts 645 during straight travel of the vehicle 10. Rotation of the ring bevel gears 650 with the ring gear 620 causes rotation of the axle bevel gears 665 and rotation of the vehicle wheels 655. During a turn, the inner wheel rotates more slowly than the outer wheel. To facilitate this, the ring bevel gears 650 rotate about (or with) the ring shafts 645, thereby allowing the axle bevel gear 665 associated with the inner wheel to rotate slower than the axle bevel gear 665 associated with the outer wheel.
The differential 25 has been described as including several bearings. While not specified, journal, needle, roller, ball, tapered roller bearings, and the like could be used for any or all of the bearings described.
In operation, the transmission 20 provides power to the input pulley 90 in the form of a torque at a speed. The input pulley 90 operates at a first speed that varies in response to the position of the control system 30. The input bevel gear 540 rotates with the input pulley 90 at the same speed as the input pulley 90.
The input bevel gear 540 engages both the forward bevel gear 575 and the reverse bevel gear 565 to rotate the first shaft 545 at a second speed that is slower than the first speed. The position of the control system 30 determines which of the forward bevel gear 575 and reverse bevel gear 565 is rotationally coupled to the shaft 545. Thus, the control system 30 determines the direction of rotation of the shaft 545. In the illustrated construction, the forward and reverse bevel gears 575, 565 are approximately 2.5 times the diameter of the input bevel gear 540. As such, the first shaft 545 rotates about 2.5 times slower than the input pulley 90. The direction of rotation depends on which of the forward bevel gear 575 and the reverse bevel gear 565 is engaged with the shaft 545.
When the control system 30 is in either the second position or the third position, the first spur gear 570 is engaged with the first shaft 545 and thus drives the second shaft 605 via the fourth spur gear 610. In the illustrated construction, the fourth spur gear 610 is approximately 2.5 times larger than the first spur gear 570, thereby producing a second stage of speed reduction. As such, the second shaft 605 rotates at a third speed that is about 2.5 times slower than the second speed when the control system 30 is in either the second position or the third position.
When the control system 30 is in the first position, the second spur gear 580 drives the second shaft 605 via the third spur gear 600. Because the third spur gear 600 is approximately the same size as the second spur gear 580, there is no second stage reduction and the second shaft 605 rotates at a fourth speed that is the same as the second speed. Thus, for a given transmission output speed, the second shaft 605 rotates about 2.5 times faster when the control system 30 is in the first position than it does when the control system 30 is in the second or third positions.
The fifth spur gear 615 engages the ring gear 620 to rotate the ring gear 620 at a fifth speed. The ring gear is approximately 3 times the size of the fifth spur gear 615. As such, the fifth speed is approximately one-third the third speed when the control system 30 is in the second and third positions and one-third the fourth speed when the control system 30 is in the first position.
The illustrated construction provides a speed reduction of between about 18 to 1 and 19 to 1 when the control system 30 is in the second position or the third position, and a speed reduction of about 7.5 to 1 when the control system 30 is in the first position. Thus, when the input pulley 90 rotates at 2000 rpm, the ring gear 620 rotates at about 110 RPM when the control system 30 is in the second position or the third position, and about 265 RPM when the control system 30 is in the first position. In addition to the reduction in speed, there is a corresponding increase in torque at the ring gear 620.
During straight-line operation of the vehicle 10, rotation of the ring gear 620 produces a corresponding rotation of the ring bevel gears 650. However, the ring bevel gears 650 do not rotate about the ring gear shafts 645. As such, the ring bevel gears 650 couple the axle bevel gears 665 to the ring gear 620 such that the axle bevel gears 665 rotate at substantially the same speed as the ring gear 620. In addition, the axles 625 and the wheels 655 attached to the axles 625 rotate at substantially the same speed as the ring gear 620.
During a turn, one of the wheels 655, axles 625, and axle bevel gears 665 must rotate slightly slower than the opposite wheel 655, axle 625, and axle bevel gear 665. To facilitate this, the ring bevel gears 650 rotate about the ring shaft axes. The rotation of the ring bevel gears 650 allows one axle bevel gear 665 to rotate slower than the ring gear 620, while simultaneously allowing the opposite axle bevel gear 665 to rotate faster.
While the illustrated construction includes spur gears and bevel gears, one of ordinary skill in the art will realize that other types of gears (e.g., helical, etc.) could be employed. Furthermore, additional components not described herein may also be included in the transmission 20, differential 25, or control system 30.
The illustrated construction provides a continuously variable drive train that is operable across a large speed range. Some of the speed variation is provided by the transmission module 20 and some is provided by the differential module 25. For example, the transmission module 20 may allow for a variation of speed across a first speed range. The differential module 25 steps the first speed range down and provides for forward operation in a first, or low speed range and a second, or high speed range. Generally, the speed ranges overlap slightly. However, if properly arranged, the low and high speed ranges can cooperate to provide nearly double the speed range provided by the transmission alone. In addition, the differential module 25 allows for efficient variable speed operation in reverse. All of the speed and direction changes can be made using a single simple user interface 370 without a clutch. This greatly simplifies operation of the tractor 10 and reduces the number of components required to assemble the control system 30.
Various features and advantages of the invention are set forth in the following claims.
