SPECIFICATIONBlocking pin for a transmission synchronizer assemblyBACKGROUND OF THE INVENTION1. Field of the Invention:The present invention relates in general to motor vehicle transmissions and in particular to an improved blocking pin for a transmission synchronizer assembly.
Synchronizing clutches, such as are used in transmission gearings for motor vehicles, are typically shiftable in opposite directions from a neutral position to either of two different speed ratio or drive positions. Clutches of the type typically include a single, toothed element and two friction elements, the toothed element having clutch teeth formed on opposite ends thereof and the friction elements having a friction having a friction face formed on outwardly facing ends thereof. The two friction elements can be connected by a piurality of blocking pins, each having a blocking shoulder formed thereon to prevent the toothed element from shifting at undesired times. The blocking pins can each include a notch formed thereon to position the toothed element accurately in a neutral position between the two drive positions.
The toothed element and friction face at one end of the synchronizer assembly coact with a respective complementary element and face on a member in one gear drive means while the toothed element and friction face at the other end of the synchronizer assembly coact with a respective complementary element and face on a member in another gear drive means. The synchronizer assembly elements are shiftable as a unit in one direction or the other by applying a shifting force to the toothed element until the friction face of the friction element at one end of the synchronizer assembly engages with the complementary friction face on the gear drive means.The toothed element is then, after synchronization of the speeds of the output shaft and the gear drive means, shiftable axially relative to the friction elements as the shifting force is continued to be applied such that the toothed element is brought into engagement with the coacting gear drive means element.
2. Description of the Prior ArtUnited States Patent No. 2,384,439 toCarnagua et al. discloses a positive clutch mechanism wherein the shaft from a lower ratio, such as a second speed, to a higher ratio, such as a direct drive, is effected automatically in response to a decelerating torque load transmitted from the lower ratio driving member to the clutch mechanism. The downshift from the higher ratio to the lower ratio may be effected by a torque responsive means under the control of the operator in moving the engine throttle control in a throttle opening direction. The torque responsive mechanism energizes both a frictional synchronizing mechanism and a positive clutch means.
Blocking pins in the frictional synchronizing mechanism can include a recess or groove positioned on either side of the neutral position recess for positioning a shift sleeve in a desired gear ratio. Similar grooves are illustrated in United States Patent No. 3,086,633 to Winter.
United States Patent No. 2, 425,203 toPeterson et al. discloses a synchronizing clutch having a blocking shoulder or blocking tooth arrangement whereby blocking takes place only when a shift is being made from a lower speed drive into a higher speed drive or, if desired, from a higher gear ratio into a lower gear drive wherein the vehicle is in motion and a member in the gear train is rotating. Blocking does not take place when a shift is being made from a lower gear drive when the vehicle is stationary or the member in the lower gear drive is not rotating.
United States Patent No. 2,900,059 toZittrell et al. discloses an improved synchronization device having a friction shift member and a push dog sleeve which can be locked until synchronization is reached. Locking members are guided so as to be radially movable on a friction ring freely rotatable within the inner part of the gear shift sleeves.
The locking members have sloping rounded surfaces at each end, the inwardly directed ends of which fit opposing surfaces situated on the inner portion of the gear shift sleeve and are effected in the peripheral direction.
The outwardly directed ends of the sloping rounded surfaces meet opposite surfaces of the push dog sleeve and are effected in the axial direction. The opposite surfaces arranged in the inner part of the gear shift sleeve are formed in marginal recesses of the inner part which allow space for partial rotation of the friction ring relative to the inner part so as to permit radial movement of the locking members during rotation of the friction ring.
SUMMARY OF THE INVENTIONThe present invention relates to an improved blocking pin for a transmission synchronizer assembly. The assembly includes a toothed element which is rotatable with an output shaft and adapted to be selectively engaged with a gear drive means for rotating the output shaft. A synchronizing friction element rotatable with the toothed element is adapted to be selectively engaged with a friction face of the gear drive means. A plurality of blocking pins are provided to slidably mount the toothed element coaxially with respect to the friction element. Each of the blocking pins includes a central recessed portion for retaining the toothed element in a first, typically non-engaged or neutral, position relative to the friction element.An in dined ramp portion is provided on each blocking pin having a first end adjacent to an edge of the neutral recessed portion and a second end recessed in the blocking pin for retaining the toothed element in a second, typically engaged, position relative to the friction element. Locking means are resiliently retained in the toothed element and urged into frictional engagement with each of the blocking pins for cooperating with the recessed portions and the ramp portions to selectively retain the toothed element in the engaged position.
It is an object of the present invention to reduce the time required to shift from one gear to the next in a synchronized multi-speed transmission.
It is another object of the present invention to maintain the gear-changing elements of a synchronized multi-speed transmission in a generally planar relationship during shifting.
Other objects and advantages of the present invention will become 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 DRAWINGSFigure 1 is a sectional elevational view illustrating the upper half of a prior art transmission synchronizer assembly utilizing conventional blocking pins, wherein the transmission synchronizer assembly is shown in a neutral position.
Figure 2 is a sectional elevation similar toFig. 1, wherein the prior art transmission synchronizer assembly is shown in a selected gear engaging position.
Figure 3 is a sectional elevational view illustrating the upper half of a transmission synchronizer assembly utilizing improved blocking pins in accordance with the present invention, wherein the transmission synchronizer assembly is shown in a neutral position.
Figure 4 is a sectional elevational view similar to Fig. 3, wherein the transmission synchronizer assembly is shown in a selected gear engaging position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTReferring now to the drawings, there is illustrated in Figs. 1 and 2 the upper half of a transmission synchronizer assembly 10 which is known in the art. The transmission synchronizer assembly 10 includes a toothed element, such as a disk-shaped shift sleeve 1 2 having an outer annular channel 14 connected by a generally flat central portion 1 6 to an enlarged inner sleeve portion 18. The outer annular channel 14 cooperates with a manually operable shift fork (not shown) to apply an axial shifting force to the transmission synchronizer assembly 10. The inner sleeve portion 18 has a plurality of inwardly-extending splines 20 for engaging a driven output shaft (not shown) of the transmission synchronizer assembly 10.
The inner sleeve portion 18 also includes a first plurality of outwardly-extending splines 22 (only one is illustrated) formed on one side of the shift sleeve 1 2 and a second plurality of outwardly-extending splines 24 (only one is illustrated) formed on the other side of the shift sleeve 1 2. The first and second pluralities of outwardly-extending splines 22 and 24 are provided to cooperate with respective first and second gear drive means (not shown) which are each connected to an input shaft (not shown) in a known manner to selectively rotate the output shaft at two different speed ratios with respect to the speed of the input shaft.
A plurality of apertures 26 (only one is illustrated) are formed in the central portion 1 6 of the shift sleeve 1 2. Typically, six such apertures 26 are formed in the central portion 1 6 and are spaced equidistantly therearound.
Each aperture 26 has a conventional blocking pin 28 extending therethrough. Each blocking pin 28 includes an enlarged side region 30 and a generally flat tapered cam surface 32.
In practice, the blocking pins 28 are disposed around the shift sleeve 1 2 such that the side portions 30 are oriented in altering fashion sequentially about the shift sleeve 1 2.
Each blocking pin 28 also includes a central recessed portion 34 formed on a generally flat inner surface 36 of the pin 28, as shown most clearly in Fig. 2. A locking means is resiliently retained in central portion 1 6 of shift sleeve 1 2 for cooperating with the recessed portion 34 of each blocking pin 28 so as to releasably retain the shift sleeve 1 2 in a first position, such as the non-engaged or neutral position illustrated in Fig. 1. The locking means can include an outwardly-extending detent 38 which is slidably retained in and axially extending aperture 39 formed in the central portion 1 6 of the shift sleeve 1 2. The detent 38 is urged into frictional engagement with the blocking pin 28 by a spring 40.
The ends of each blocking pin 28 are attached in a known manner to respective synchronizing friction elements, such as a synchronizer races or cones 42 and 44. Each of the synchronizer races 42 and 44 is an annular member having a generally flat, threaded, tapered inner surface 46. A plurality of axially extending channels 48 are formed in the inner surfaces 46 of each of the synchronizer races 42 and 44. The threaded inner surfaces 46 and the axially extending channels 48 of the synchronizer races 42 and 44 provide a path for draining transmission fluid or other lubricant from the region of the inner surface 46 such that a reliable frictional engagement with the corresponding friction face in the selected gear drive means can be obtained.
When it is desired to shift the transmission synchronizer assembly 10 out of the first or neutral position illustrated in Fig. 1 into a second or gear engaging position, a shifting force is applied to the outer annular channel 14 of the shift sleeve 12 by means of the shift fork. Initially, the entire transmission synchronizer assembly 10 slides a short distance along the output shaft, typically .030 to .090 inches, until the inner surface 46 of the synchronizer race 42 frictionally engages the corresponding friction face of the desired gear drive means. Such frictional engagement is necessary to synchronize the speeds of rotation of the input and output shafts during the gear shifting process.After such speed synchronization, additional shifting force causes the shift sleeve 12 to slide axially with respect to the synchronizer race 42 into the second position illustrated in Fig. 2, wherein the first gear drive means is engaged.
During the above-described gear shifting process, it will be appreciated that the shifting force applied to the shift sleeve 1 2 causes the detent 38 to overcome the urging of the spring 40-and retract inwardly within the aperture 39 formed in the central portion 1 6 of the shift sleeve 1 2. Once removed from the recessed portion 34 of the blocking pin 28, the detent 38 slides along the flat inner surface of the pin 28 until the shift sleeve 1 2 reaches the second position. As disclosed in the prior art, a second recess (not shown) may be formed in the blocking pin 28 such that the detent 38 may extend therein to releasably retain the shift sleeve 1 2 in the second position.A similar structure may be utilized to move the shift sleeve 1 2 towards the other synchronizing race 44 into a third position, wherein the second gear drive means is engaged.
Figs 3 and 4 illustrate a similar transmission synchronizer assembly 50 utilizing an improved blocker pin 52 in accordance with the present invention. The structures of the shift sleeve 1 2 and the synchronizer races 42 and 44 are identical to that described above and, accordingly, identical reference numerals are utilized to describe these elements. The improved blocking pin 52 includes an enlarged side region 54, a generally flat tapered cam surface 56, and a central recessed portion 58 respectively similar to the side portion 30, cam surface 32, and central recessed portion 34 described above. The blocking pin 52 additionally includes a pair of inclined ramp portions 60, each extending from a first end adjacent to an edge of the central recessed portion 58 outwardly toward a second end recessed to form recessed portion 62 in the blocking pin 52.Although any desired incline may be utilized for the ramp portion 60, it has been found desirable that a gradual ramp of approximately twelve degrees yields desirable results.
In operation, when the applied shifting force begins to move the shift sleeve 1 2 with respect to the synchronizer races 42 and 44, the detent 38 will initially be pushed radially inwardly within the aperture 39. However, once completely removed from the central recessed portion 58, the detent 38 will begin to move axially outwardly under the urging of the spring 40 as the shift sleeve 1 2 slides farther along the inclined ramp portion 60 until it reaches the fully recessed portion 62 of the second position illustrated in Fig. 4.
The inclined ramp portions 60 provide several significant advantages over the prior art blocking pins 28. The frictional engagement of the detent 38 with the inclined ramp portion 60 of the blocking pin 52 generates forces which tend to "pull" the shift sleeve 1 2 toward the selected gear engaging position. It has been found that the additional force required to return the shift sleeve 1 2 to the neutral position is insignificant. The frictional engagement of the detent 38 with the inclined ramp portion 60 also generates forces which reduce the time required to shift from one gear engaging position to the other gear engaging position.For example, if the transmission synchronizer assembly 50 is in the second position near the synchronizer race 42, as illustrated in Fig. 4, and it is desired to shift to the third position near the other synchronizer race 44, a shifting force is initially applied to the shift sleeve 1 2. If the inclined ramp portions 60 of the present invention were not present, the shift sleeve 1 2 would initially move to the neutral position before the transmission synchronizer assembly 50 would slide as a unit along the output shaft until the synchronizer race 44 engages the frictional face of the second gear drive means.
However, when the inclined ramp portions 60 are present in the blocking pin 52, the transmission synchronizer assembly 50 will shift slightly along the output shaft as a unit in the relationship illustrated in Fig. 4 until the synchronizer race 44 engages the friction face of the second gear drive means. Thereafter, the shift sleeve 1 2 will move through the first or neutral position into the third position. Also, it can be seen that the abovedescribed movement of the transmission synchronizer assembly 50 causes the first synchronizer race 42 to be pulled out of frictiona engagement with the first gear drive means sooner than would otherwise occur. This movement minimizes the effect due to runout.
Additionally, the present invention tends to maintain the synchronizer races 42 and 44 in a generally planar relationship with the shift sleeve 1 2 during the shifting process. The detents 38 in the shift sleeve 1 2 exert small uniform forces about the synchronizer race 42 or 44 which the shift sleeve 1 2 is moving towards. Such forces tend to prevent cocking or other misalignment of the synchronizer races 42 and 44.
In accordance with the provisions of the patents statutes, the principle and mode of operation of the present invention have been explained and illustrated in its preferred embodiment. However, it must be appreciated that the present invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.