MXPA98000467A - Closure assembly for vehic transmission - Google Patents

Abstract

A locking assembly for a vehicle transmission prevents more than a plurality of displacement rails from being simultaneously moved axially away from the central neutral position to a gear engaging position. The closure assembly includes a closure plate having four semicircular cuts (one for each of the travel rails) and two relatively large interior openings. The closure assembly further includes a back plate, which is a little smaller than the closure plate and has two relatively small interior openings. A pair of threaded fasteners extend through the small openings of the backing plate and through the respective spacer bushings disposed in the large interior openings of the closing plate towards threaded engagement with the housing of the hydraulic actuator. The spacer bushings prevent the closure plate from being frictionally engaged between the backing plate and the hydraulic actuator housing. As a result, the closure plate is loosely supported on the threaded fasteners and can slide freely in any direction relative thereto, each of the four cuts of the closure plate being formed having opposite tapered edges, which cooperate with each other. taper grooves formed on the outer surfaces of the four sliding rails. When any of the four displacement rails move out of the central neutral position, the closure plate slides to extend into the slots of the other three displacement rails. In this way, the closing plate prevents the other sliding rails from moving until all are in the neutral position.

Description

CLOSURE ASSEMBLY FOR TRANSMISSION OF VEHICLE BACKGROUND OF THE INVENTION This invention relates in general to vehicle transmissions and in particular to an improved structure for a closing assembly to prevent more than one drive train in a vehicle transmission from being moved from a neutral position at a given time. On most vehicles, a transmission is provided on the drive train between the engine and drive wheels. As is well known, the transmission includes a cover containing an input arrow, an output arrow and a plurality of take-off gears. Means are provided for connecting the selected gears of the take-off gears between the input shaft and the output shaft to provide a desired rate reduction gear ratio between them. The take-up gears contained within the transmission cover are of a variable size in order to provide a plurality of such gear ratios. By properly moving between these various gear ratios, the acceleration and deceleration of the vehicle can be achieved in a uniform and efficient manner. The displacement of the transmission between the available gear ratios is often achieved manually, wherein the selection and coupling of a specific gear ratio is performed in response to some physical effort by the driver of the vehicle. More commonly, the driver takes and physically moves an upper portion of an elongated shift lever to initiate the selection and engagement of a gear ratio. In response to this, a lower portion of the shift lever engages and moves a plurality of displacement rails provided within the transmission. The movement of the selected displacement rail causes certain tap gears to be connected between the input arrows and the output shaft, in order to provide the desired gear ratio between them. Manually displaced transmissions are desirable because they are relatively simple, inexpensive and lightweight in structure and operation. Because of this, most medium and heavy duty truck transmissions in common use today are manually displaced transmissions. In order to provide the convenience of using manually offset transmissions, several structures have been proposed to partially or completely automate the displacement thereof. In a partially automatic manual transmission, the travel lever manipulated by the driver engages and moves certain travel rails, while an automatic movement mechanism (which can be hydraulically or pneumatically driven) engages and moves the rest of the travel rails . For example, the lower gear ratios of a partially automatic manual transmission can be manually selected and coupled by the vehicle driver using the shift lever, while the higher gear ratios are automatically selected and coupled by the automatic shift mechanism . In a fully automatic manual transmission, the shift lever operated by the driver is usually replaced by the automatic shift mechanism. The automatic movement mechanism works to move all the displacement rails within the transmission through all the available gear ratios. A partially automatic manual transmission is advantageous, particularly in long haul applications and similar transport applications, since it is lower in cost than a comparable fully automatic manual transmission, offers an automatic shift in the higher gear ratios, where it occurs most of the displacement between the gearsin a normal way In both types of transmissions, the displacement rails are typically modalized as elongated members, which are supported in a separate and parallel manner within the transmission cover. Each of the displacement rails usually moves from a central neutral position either axially forward to a first gear coupling position or axially back towards a second gear coupling position. In this way, for example, a transmission having four displacement rails is capable of selecting a total of eight different gear ratios, (usually seven forward gear ratios and one reverse gear ratio) In order to prevent damage to the transmission occurs during use, it is important that only one of the displacement rails be moved out of the neutral position at any given time. To achieve this, it is known to provide the transmission with a closing mechanism, which responds to the movement of one of the travel rails out of the neutral position to positively maintain all the other travel rails in a neutral position. A wide variety of such closure mechanisms are known in the art. In many cases, the closing mechanism is connected to the movement lever to move with it. However, in the fully automatic manual transmissions described above, no shift lever is typically provided. In other transmissions, the closing mechanism directly responds to the movement of the displacement rails unfortunately, the known locking mechanisms of this type are relatively complicated and expensive. In this way, it may be desirable to provide an improved structure for a locking mechanisms for a vehicle transmission that is suitable for use in both manual and automatic transmissions, and also that it be simple and inexpensive in structure and operation.

BRIEF DESCRIPTION OF THE INVENTION This invention relates to an improved structure for a closure assembly for a vehicle transmission, which is adapted to prevent more than one of a plurality of displacement rails being simultaneously moved axially away from the central neutral position towards a position gear coupling. The closure assembly includes a closure plate having four semicircular outlet cuts (one for each of the travel rails) and two relatively large interior openings. The closure assembly further includes a back plate, which is a little smaller than the closure plate and has two relatively small interior openings. A pair of threaded fasteners extend through the small openings of the backing plate and through the respective spacer bushings disposed in the large interior openings of the closing plate towards threaded engagement with the housing of the hydraulic actuator. The spacer bushings prevent the closure plate from being frictionally engaged between the backing plate and the hydraulic actuator housing. As a result, the closure plate is supported loosely on the threaded fasteners and can freely slide in any direction relative thereto. Each of the four cuts of the closure plate is formed with opposite tapered edges, which cooperate with tapered grooves formed on the outer surfaces of the four displacement rails. When any one of the four scroll rails moves out of the central neutral position, the closing plate slides to extend into the slots of the other three slide rails. In this way, the closing plate prevents other sliding rails from moving until they are all in the central neutral position.

Various objects and advantages of this invention will be apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a sectional elevation view of a portion of a vehicle transmission that includes a displacement cylinder assembly and a closing mechanism in accordance with this invention. Figure 2 is an enlarged top plan view of the displacement cylinder assembly and closure mechanism illustrated in Figure 1. Figure 3 is a sectional elevation view of the displacement cylinder assembly and closure mechanism illustrated in FIG. Figures 1 and 2. Figure 4 is an extreme elevation view, partially separated, of the displacement cylinder assembly and the closing mechanism illustrated in Figure 3.

Figure 5 is an enlarged elevation view of the closure plate for the closure mechanism illustrated in Figures 1 to 4. Figure 6 is a sectional elevation view of the closure plate taken along the line 6. -6 of Figure 5. Figure 7 is an enlarged elevation view of a backing plate for the closing mechanism illustrated in Figures 1 to 4.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY Referring now to the drawings, a portion of a vehicle transmission, generally indicated at 10, is illustrated in Figure 1 in accordance with this invention. The transmission 10 includes a cover 11, which encloses a number of components not illustrated, including an inlet arrow, an exit arrow, a plurality of intake gears and means for connecting the selected gears of the intake gears between the arrow input and the output arrow. These unillustrated components are so well known in the art that a discussion thereof is not necessary for a total and complete understanding of the invention. The take-up gears contained within the transmission cover 11 are of a variable size, in order to provide a plurality of gear ratios. The proper displacement between these various gear ratios achieves the acceleration and deceleration of the vehicle in a moderate and efficient manner. A plurality of elongated displacement rails 20, 21, 22 and 23 (see Figure 2) are provided within the cover 11 of the transmission 10. The displacement rails 20, 21, 22 and 23 are supported in a parallel fashion within the transmission cover 11 in a conventional manner. Each of the displacement rails 20, 21, 22 and 23 is longitudinally movable from a central neutral position toward either a forward position (to the left when viewed in Figure 1) to engage a first gear ratio, or to a backward position (to the right when looking at Figure 1) to attach a second gear ratio. The manner in which the displacement rails 20, 21, 22 and 23 move, will be explained later. The forward ends of the displacement rails 20, 21, 22 and 23 have respective notches 20a, 21a, 22a, and 23a formed therein. The notches 20a and 22a are formed on the lower surfaces of the displacement rails 20a and 22a, while the notches 21a and 23a are formed on the upper surfaces of the displacement rails 21a and 23a. The purposes of these notches 20a, 21a, 22a, 23a will be explained later. A first travel fork 25 is connected to the first travel rail 20 through rivets 25a or other conventional means for moving therewith. Similarly, second, third and fourth displacement forks (not shown) are respectively connected to the second, third and fourth displacement rails 21, 22 and 23. The displacement forks 25 extend downwardly from their associated displacement rails 20, 21, 22 and 23 in engagement with the respective gear coupling mechanisms (not shown) provided in the lower portion of the transmission 10. The shift forks 25 and gear coupling mechanisms are also conventional in the art.

The components of the transmission 10 thus described constitute the basic structure of the main section of the transmission 10, which provides a predetermined number of gear reduction ratios between its input and output arrows (not shown). In the illustrated embodiment, the first travel rail 20 is provided to travel between the sixth and seventh gear ratios, the second travel rail 21 is provided for displacement between the fourth and fifth gear ratios, the third travel rail 22 it is provided for the displacement between the second and third gear ratios, and the fourth displacement rail 23 is provided for the displacement between the inverse and the first gear ratios. In this way, the illustrated main section of the transmission 10 is a speed transmission 8 (seven forward gear ratios and one reverse gear ratio). However, it will be appreciated that this invention can be used in transmissions having a greater or lesser number of displacement rails and gear ratios.

The transmission 10 further includes an enlarged bell housing 30, which is attached to the forward end of the transmission cover 11 through a plurality of threaded fasteners 31 or other means. The bell housing 30 is generally hollow in shape and is provided for securely enclosing portions of a conventional clutch (not shown) connected between a motor or other rotational energy source and the transmission 10. The bell housing 30 includes a wall lower 32, which closes the open front end of the transmission cover 11 to enclose in a protective manner the various components of the transmission 10. An opening 33 is formed through the upper portion of the inner wall 32 of the bell housing. A displacement cylinder assembly, generally indicated at 50, is provided to selectively perform longitudinal movement of the displacement rails 20, 21, 22 and 23. The displacement cylinder assembly 50 includes a housing 51 having a pair of portions. of flange 52 extending outwardly formed therein. A pair of openings 52a is formed through a portion of the flanges 52. The respective threaded fasteners 53 extend through each of the openings 52a to secure the housing 51 to the inner wall 32 of the bell housing. 30. In this way, the housing 51 of the displacement cylinder assembly 50 is fixed at a position relative to the other components of the transmission 10. Referring to Figure 3, a plurality of openings 55 are formed longitudinally in extension to through the housing 51 of the displacement cylinder assembly 50. Each of the openings 55 has an internally threaded portion 56 located at the forward end of the displacement cylinder assembly 50. Each of the openings 55 further includes a first internal shoulder 57 , a second internal shoulder 58 and a rear end 59. The purposes of the first and second internal shoulders 57 and 58 will be further explained. nte. Each of the openings 55 functions as a cylinder for a hydraulic shift mechanism, which is provided for each of the displacement rails 20, 21, 22 and 23 contained within the transmission 10. In this manner, an opening 55 preferably it is provided for each of the displacement rails 20, 21, 22 and 23 contained within the transmission 10. Since the same openings 55, as well as the hydraulic movement mechanisms contained therein, are identical for each of the displacement rails 20, 21, 22 and 23, the structure of only one of such openings 55 and its associated hydraulic shift mechanism will be explained in detail. A is provided. Screw plug 60 for ~ closing the forward end of the opening 55. If desired, an O-shaped ring 61 or other sealing structure may be disposed within or near the internally threaded portion 56 in order to provide a fluid-tight seal. An outer piston 62 is disposed within the opening 55 adjacent the plug 60. The outer piston 62 is hollow and has a cylindrical shape and may include an O-shaped ring 63 or other sealing structure to provide a fluid-tight seal between its outer surface and the inner surface of the opening 55. As will be explained in detail later, the outer piston 62 is longitudinally movable between a first backward position where the rear end of the outer piston 62 abuts the first internal shoulder 57 of the opening 55, and a second forward position wherein a front end of the outer piston 62 abuts the plug 60. An internal piston 65 is also disposed within the opening 55 and includes a front end portion, which extends concentrically within of the external piston 62. The internal piston 65 has a cylindrical shape and may include a ring 66 in the form 0 or other sealing structure for In addition, a fluid-tight seal between the outer surface of the front end thereof and the internal surface of the inner piston 62 can be provided. The inner piston 65 can further include an O-shaped ring 67 or other sealing structure to provide a seal. fluid-tight seal between its outer surface and the inner surface of the opening 55 formed through the displacement cylinder assembly 50. As will be explained in detail below, the inner piston 65 is longitudinally movable between a first forward position, in where an outer shoulder 65a formed on the inner piston 65 abuts the rear end of the outer piston 62 and a second rearward position where the outer shoulder 65a formed on the inner piston 65 is separated from the rear end of the external piston 62. It is also arranged a piston rod 70 inside the opening 55 and includes a front threaded end portion 70a, which is threaded in a corresponding hole 65b formed in the rear end of the inner piston 65, in this way the piston rod 70 is connected to the internal piston 65 for the longitudinal movement with it. The piston rod 70 extends rearwardly through a bushing 71, which is disposed within the opening 55 adjacent the rear end of the displacement cylinder assembly 50. The bushing 71 which is provided to support the piston rod 70 for the longitudinal movement, it is preferably adjusted by pressure inside the opening 55 in order to remain fixed in place relative thereto. An O-shaped ring 72 or other sealing structure may be provided adjacent the housing 71 in order to provide a fluid-tight seal between the outer surface of the piston rod 70 and the inner surface of the opening 55. It is formed an annular depression 73 around the piston rod 70 adjacent to its rear end whose purpose will be explained in detail later. The rear end of the piston rod 70 extends outwardly from the housing 51 of the displacement cylinder assembly 50 and ends "-in an extreme portion 74 generally in the form of L. The shape and size of the end of the L-shaped end portion 74 of the piston rod 70 generally corresponds to the size and shape of the notch 20a formed in the displacement rail 20. In this way, the better the shown in Figure 2, the end of the L-shaped end portion 74 of the piston rod 70 extends in cooperation with the notch 20a formed in the lower surface of the displacement arrow 20. As a result, the displacement rail 20 engages the piston rod 70 to move therewith. Similarly, the ends of the L-shaped end portions 74 of the other piston rods 70 extend in cooperation with the notches 21a, 22a and 23a formed in the other displacement rails 21, 22 and 23, consequently, the other rails displacement 21, 22 and 23 are also connected to move with the other piston rods 70. Referring back to Figure 1, it can be seen, that a first plurality of fluid ports 75, 76 and 77 are formed in the housing 51 of the displacement cylinder assembly 50. These fluid ports 75, 76 and 77 communicate with the front, intermediate and rear portions of the opening 55 formed through the housing 50, respectively. When it is desired to move the displacement rail 20 to the central neutral position i lustrade * .- in Figure 3, pressurized fluid, (such as air) is supplied to the front and rear fluid ports 75 and 77, respectively, while that the intermediate fluid port 76 is vented to the atmosphere. As a result, the outer piston 62 moves backward to abut the first internal shoulder 57 provided within the opening 55. At the same time, the inner piston 65 moves forward to abut the external piston 62. In this way, the internal piston 65, the piston rod 70, and the displacement rail 20 move towards the central neutral position illustrated in Figure 3.

When it is desired to move the displacement rail 20, towards the forward position (to the left when looking at Figure 3) to attach a first gear ratio, pressurized fluid is supplied to the intermediate and rear fluid ports 76 and 77, respectively, while the front fluid port 75 is vented to the atmosphere . As a result, the outer piston 62 moves forward to abut the plug 60. At the same time the inner piston 65 moves forward to abut the external piston 62. In this manner, the internal piston 65, the piston rod 70 and the displacement rail 20 move forward from the illustrated central neutral position to engage a first gear ratio. Conversely, when it is desired to move the slide rail 20 to the rear position (to the right when viewed in Figure 3) to engage a second gear ratio, pressurized fluid is supplied to the front and intermediate fluid ports 75 and 76, respectively, while the rear fluid port 77 is vented to the atmosphere. As a result, the outer piston 62 moves backward to abut the first internal shoulder 57 provided within the opening 55. At the same time, the inner piston 65 moves rearwardly to abut the hub 71. In this way, the internal piston 65, the piston rod 70 and the displacement rail 20 move backward from the illustrated central neutral position to engage a second gear ratio. Similar fluid ports 75, 76 and 77 are formed in the housing 51 of the displacement cylinder assembly 50 to effect the longitudinal movement of the other displacement rails 21, 22 and 23 in a similar manner. A locking mechanism, indicated generally at 80, is provided to ensure that only one of the displacement rails 20, 21, 22 and 23 can be moved out of the central neutral position into a gear engaging position at any given time. The closure mechanism 80 includes a closure plate 81, which is disposed adjacent the rear end of the housing 51 of the displacement cylinder assembly 50. The structure of the closure plate 81 is illustrated in detail in Figures 5 and 6. As shown herein the closure plate 81 is flat and has a generally trapezoidal shape, having a plurality of arcuate cuts 82 formed therein. Each of the cuts 82 has tapered upper and lower surfaces 82a and 82b in order to define a curved side surface having a rounded profile, as best shown in Figure 6. Preferably, a cut 82 is provided for each of the piston rods 70. Thus, in the illustrated embodiment four of these cuts 82 are provided in the closure plate 81. However, a larger or smaller number of such cuts 82 may be provided if desired. closure plate 81 further has a pair of relatively large apertures 83 formed therein. The purpose of the openings 83 will be explained later '. A backing plate 85 is provided to retain the closure plate 81 adjacent the end 30 of the housing 51 of the displacement cylinder assembly 50. The structure of the backing plate 85 is illustrated in detail in Figure 7. As shown in FIG. the same, the back plate 85 is flat and generally has a trapezoidal shape, having a plurality of arcuate cuts 86 formed therein. As with the closure plate 81, the backing plate 85 preferably has a cutout 86 formed therein for each of the piston rods 70. Thus, in the illustrated embodiment, four of these cuts 86 are provided in the backing plate 85. However, a larger or smaller number of such cuts 86 may be provided if desired. The backing plate 85 also has a pair of openings relatively small 87 formed through it. A pair of threaded fasteners 88 is provided to retain the closure plate 81 and the backup plate 85 adjacent the rear end of the housing 51 of the displacement cylinder assembly 50. The threaded fasteners 88 extend through the openings 87 small ones formed through the backing plate 85 and through respective bushings 90 (see Figures 3 and 4) disposed within the relatively large openings 83 formed through the closure plate 81 towards threaded engagement with the housing 51 of the assembly displacement cylinder 50. The bushings 90 are hollow and have a cylindrical shape and are dimensioned to function as spacers to allow limited free movement of the closure plate 81 relative to the backrest lever 85 and the displacement cylinder assembly. . To achieve this, the bushings 90 are formed having a longitudinal elongation, which is slightly larger than the longitudinal thickness of the closure plate 81. As a result, when the threaded fasteners 88 are tightened, the bushings 90 define a longitudinally extending space between the backing plate 85 and the rear end of the housing 51, which is slightly larger than the closing plate 85 disposed between that spacing. Accordingly, the free movement of the closure plate 85 is not inhibited either by the backup plate 85 or by the housing 51. Furthermore, the bushings 90 are formed having an outer diameter which is a little smaller than the internal diameter defined by the relatively large openings 83 formed through the closure plate 81, as best shown in Figure 4. As a result, the closure plate 81 is able to move in any direction relative to the backing plate 88 and to the housing 51, limited only by the relative sizes of the outer diameter of the bushings 90 and the internal diameter defined by the relatively large openings 83 formed through the closing plate 81. The ratio between the thickness of the closing plate 81 and the longitudinal elongation of the bushings 90, as well as the ratio of the internal diameter of the relatively large openings 83 formed through the closure plate 81 and the external diameter of the bu jes 90, will vary with the design of the particular transmission 90 in which they are being used. When the closing mechanism 80 is assembled and all the displacement rails 20, 21, 22 and 23 are in their central neutral positions, the cuts 82 of the closure plate 81 are aligned with and extend partially within the annular depressions 73. formed on the displacement bars 20, 21, 22 and 23, as best shown in Figure 3. When, for example, the displacement rail 20 is moved longitudinally out of the central neutral position towards one of its engaging positions. gear, the associated depression 73 moves out of alignment with the cut 82 of the closure plate 81, and the internal surface of the cut 82 is engaged by the external surface of the piston rod 70. As a result, the closing plate 81 it moves laterally, so that the lateral surfaces of the other three cuts 82 move additionally towards the associated annular depressions 73 formed in the other three travel lanes 21, 22 and 23. If one attempts to move any of the other displacement tracks 21, 22 and 23 longitudinally out of the central neutral position, the cuts 82 of the closure plate 81 engage the sides of the annular depressions 73. Consequently, the closure plate 81 positively prevents more than one of the displacement rails 20, 21, 22 and 23 from moving out of the central neutral position at any given point. In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention has been explained and illustrated in its preferred embodiment. However, it should be understood that this invention may be practiced in a manner other than that specifically explained and illustrated without departing from its spirit or scope.

Claims (9)

1. A closing mechanism for a vehicle transmission having a plurality of movable displacement rails for selecting and coupling a desired gear ratio between an input shaft and an output shaft, the closure mechanism comprising: a housing; a closure plate defining a thickness and having an opening formed therethrough defining an internal diameter, the closure plate having a surface that is adapted to engage the plurality of displacement rails; a bushing arranged inside the opening formed through the closing plate, the bushing defining a length, which is slightly larger than the thickness of the closing plate, the bushing also defining an external diameter which is slightly smaller than the internal diameter of the opening; a backing plate having an opening formed therethrough; and a fastener extending through the opening of the backing plate and through the bushing disposed within the opening formed within the closure plate toward engagement with the housing to allow limited free movement of the closure plate in any direction.

2. The closure mechanism according to claim 1, wherein the closure plate has a pair of openings formed therethrough, each of which defines an internal diameter.

3. The closure mechanism according to claim 2, wherein a bushing is disposed within each of the openings formed through the closure plate.

4. The closure mechanism according to claim 3, wherein the bushings define a length, which is slightly greater than the thickness of the closure plate.

5. The closing mechanism according to claim 3, wherein the backing plate has a pair of openings formed therethrough.

6. The closure mechanism according to claim 5, wherein a fastener extends through each of the openings of the backing plate and through each of the bushings disposed within the openings formed through the plate. of closure towards coupling with the alloy.

7. The closing mechanism according to claim 1, wherein the closure plate is flat and has a generally trapezoidal shape.

8. The closure mechanism according to claim 1, wherein the closure plate has a plurality of cuts formed therein, which are adapted to couple the plurality of displacement rails.

9. The closing mechanism according to claim 8, wherein each of the cuts has tapered upper and lower surfaces to define a curved side surface having a rounded profile. SUMMARY OF THE INVENTION A locking assembly for a vehicle transmission prevents more than a plurality of displacement rails from being simultaneously moved axially away from the central neutral position to a gear engaging position. The closure assembly includes a closure plate having four semicircular cuts (one for each of the travel rails) and two relatively large interior openings. The closure assembly further includes a back plate, which is a little smaller than the closure plate and has two relatively small interior openings. A pair of threaded fasteners extend through the small openings of the backing plate and through the respective spacer bushings disposed in the large interior openings of the closing plate towards threaded engagement with the housing of the hydraulic actuator. The spacer bushings prevent the closure plate from being frictionally engaged between the backing plate and the hydraulic actuator housing. As a result, the closure plate is loosely supported on the threaded fasteners and can freely slide in any direction relative thereto., each of the four cuts of the closure plate is formed having opposite tapered edges, which cooperate with tapered grooves formed on the outer surfaces of the four displacement rails. When any of the four displacement rails move out of the central neutral position, the closure plate slides to extend into the slots of the other three displacement rails. In this way, the closing plate prevents the other sliding rails from moving until they are all in the central neutral position.