Hydraulic synchronizer

Abstract

Hydraulic synchronizer (50) for selectively coupling one or more gears (42, 40) to a drive shaft (54) which is rotatable about a pivot axis (R), the synchronizer (50) comprising: a shaft hub (56) configured to rotate with the drive shaft (54), wherein the shaft hub (56) has a first toothed rim (76, 74) and at least one fluid passage (136, 138, 140); a first ring (60, 62) which is attached around the shaft hub (56) and is movable along the axis of rotation (R) with respect to the shaft hub (56); a first shift sleeve (112, 110) that is rigidly coupled to the first ring (60, 62), wherein the first shift sleeve (112, 110) has a toothed ring (122, 120) that engages with the first toothed ring (76, 74) of the shaft hub (56), wherein the shift sleeve (112, 110) is configured to be disengaged from the teeth (184a) of a first of the gears (42, 40) when the first ring (60, 62) is in a first neutral position and to be engaged with the teeth (184a) of the first gear (42, 40) when the first ring (60, 62) is in a first axial position to transmit rotary drive from the shaft hub (56) to the first gear (42, 40); and first and second hydraulic chambers (150a, 150b, 150d, 150c) configured to receive hydraulic fluid from the at least one fluid feedthrough (136, 138, 140); wherein hydraulic pressure in the first hydraulic chamber (150a, 150d) acts on the first ring (60, 62) to move the first ring (60, 62) into the first axial position and hydraulic pressure in the second hydraulic chamber (150b, 150c) acts on the first ring (60, 62) to move the first ring (60, 62) into the first neutral position.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

[0001] Not applicable. INFORMATION ON GOVERNMENT-FUNDED RESEARCH AND DEVELOPMENT

[0002] Not applicable. AREA OF REVELATION

[0003] This disclosure relates to synchronizer assemblies for interconnecting a drive input to one or more gears of a transmission, and more particularly to hydraulic synchronizers for work vehicles. BACKGROUND OF REVELATION

[0004] Various transmission assemblies, such as those used in the drivetrains of various work vehicles, may include transmissions that incorporate "synchronizers" that facilitate the selective coupling of a rotating input shaft (e.g., driven by an engine or prime mover) to one or more shift ranges. Often, the synchronizers are actuated by a shift fork riding along a shift rail to move a shift sleeve splined to the input shaft into meshing engagement with a gear to transmit rotational power from the input shaft to the transmission, and thereby initiate or execute a change in speed range and torque to the wheels or tracks of the work vehicle. Reversing the actuation of the shift fork disengages the shift sleeve from the gear, and thus the transmission from the input shaft, until another gear is engaged.The shift fork can be engaged manually or under tension (e.g., via hydraulic power). In some cases, the shift fork can be eliminated, and the shift sleeve can be engaged with the gear by a hydraulic piston arrangement and released by other mechanical means (e.g., return springs).

[0005] DE 10 2007 009 462 A1 discloses a synchronizing device for a manual transmission, with which an idler gear can be selectively held rotatably or fixedly mounted relative to a shaft. An actuator axially fixed relative to the shaft is disclosed, which has at least one moving element that is movable in a displacement direction and is connected to the shaft in a rotationally fixed manner. A friction surface is arranged on the moving element, which can interact with a counter friction surface arranged on the idler gear to frictionally fix the idler gear on the shaft. SUMMARY OF REVELATION

[0006] The disclosure provides a hydraulic synchronizer assembly such as for transmissions and the like in work vehicles.

[0007] One aspect of the disclosure provides a hydraulic synchronizer for selectively coupling one or more gears to a drive shaft rotatable about a rotational axis. A shaft hub is configured to rotate with the drive shaft and includes a first toothed ring and at least one fluid passage. A first ring is disposed about the shaft hub and is movable along the rotational axis relative to the shaft hub. A first shift sleeve is fixedly connected to the first ring. The first shift sleeve has a toothed annulus with the first toothed annulus engaging the first toothed annulus of the shaft hub. The first shift sleeve is configured to engage gear teeth of a first gear when the first ring is in a first axial position and to disengage from the gear teeth of the first gear when the first ring is in a first neutral position.The first shift sleeve is configured for the following:. Transmitting a rotational drive force from the shaft hub to the first gear when the first ring is in the first axial position. First and second hydraulic chambers are configured to receive hydraulic fluid from the at least one fluid passage. Hydraulic pressure in the first hydraulic chamber acts on the first ring to move the first ring to the first axial position, and hydraulic pressure in the second hydraulic chamber acts on the first ring to move the first ring to the first neutral position; Another aspect of the disclosure provides a hydraulic synchronizer for selectively coupling first and second gears to a drive shaft rotatable about a rotational axis. A shaft hub is configured to rotate with the drive shaft, the shaft hub having first and second toothed annuli and at least one fluid passage. First and second rings, each disposed about the shaft hub, are movable along the rotational axis relative to the shaft hub. First and second shift sleeves are connected to the associated first and second rings. The first and second shift sleeves each have a toothed annulus for engaging the associated first and second toothed annuli of the shaft hub.The shift sleeve is configured to engage gear teeth with the associated first and second gears when the associated first and second rings are in the associated first and second axial positions and to disengage from the gear teeth of the associated first and second gears when the associated first and second rings are in the associated neutral positions. The first and second shift sleeves are configured to transmit rotational drive power from the shaft hub to the associated first and second gears when the associated first and second rings are in the associated first and second axial positions. A plurality of hydraulic pistons are configured to receive hydraulic fluid from the at least one fluid passage and move the first and second rings to the associated first and second axial positions and associated neutral positions.The synchronizer is configured to prevent the first and second rings from being in the associated first and second axial positions at the same time.

[0008] The details of one or more embodiments are set forth in the accompanying drawings and the following description. Further features and advantages are apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of a work vehicle in the form of a tractor in which a hydraulic synchronizer according to the present disclosure can be incorporated; Fig. 2 is a perspective view of an example of a hydraulic synchronizer between two shift ranges; Fig. 3 is a view (in section) thereof along the line 3-3 of Fig. 2 with a switching area and certain other components shown in exploded view; Fig. 4 is a partial exploded perspective view of the exemplary hydraulic synchronizer of Fig. 2; Fig. 5 is a partial view (in section) taken along the line 5-5 of Fig. 2 and shows the exemplary hydraulic synchronizer in a neutral state; Fig. 6A and Fig. 7A are enlarged views (in section) thereof; Fig. 6B and Fig. 7B are views similar to the corresponding Fig. 6A and Fig. 7A and 7B show the exemplary hydraulic synchronizer selectively engaged with the first and second gears; Fig. 8A-10A are partial side views (in section) of certain components of the exemplary hydraulic synchronizer in various positions before and after engagement with the second shift range; and Fig. 8B-10B are partial plan views thereof.

[0009] The same reference symbols in the different drawings indicate the same elements. DETAILED DESCRIPTION

[0010] The following describes one or more exemplary embodiments of the disclosed hydraulic synchronizer assembly, as illustrated in the accompanying figures of the drawings briefly described above. Various modifications to the exemplary embodiments may be contemplated by one skilled in the art.

[0011] The term "axial," as used herein, refers to a direction that is generally parallel to an axis of rotation, axis of symmetry, or centerline of a component or components. For example, in a cylinder with a centerline and opposite, circular ends, the "axial" direction may refer to the direction that is usually parallel to the centerline between opposite ends. In certain cases, the term "axial" may be used with reference to components that are not cylindrical (or otherwise radially symmetric). For example, for a rectangular housing containing a rotating shaft, the "axial" direction may be considered a direction that is generally parallel to the shaft's axis of rotation.Furthermore, the term "radial," as used herein, may refer to a direction or relationship of components with respect to a line extending perpendicularly outward from a common centerline, axis, or similar reference. For example, two concentric and axially overlapping cylindrical components may be considered "radially" aligned across the portions of the components that overlap axially, but not "radially" aligned across the portions of the components that do not overlap axially. In certain cases, components may be considered "radially" aligned even though one or both components may not be cylindrical (or otherwise radially symmetric).

[0012] Furthermore, the terms "toothed" and "toothed annulus" and derivatives, as used herein, can encompass any conventional mechanical connection for transmitting torque from one rotating component to another rotating component that is mounted to the torque-transmitting rotating component and in the direction of rotation. This can include various known gear configurations, such as parallel gears, involute gears, crowned splines, knurled gears, helical gears, and ball gears. This can also include various key and toothed arrangements of various configurations. Thus, these terms do not necessarily describe a particular profile of the intermeshing features and grooves, nor a particular mode by which torque is transmitted (e.g., key and groove engagement, toothed mating contact, and so on).The terms “annulus” and “anuli” refer to the arrangement of interlocking features and grooves, regardless of configuration, in a cylindrical path around the rotating component.

[0013] Certain known synchronizers couple the rotating shaft to the engine output shaft through movement of a shift rail and fork assembly, which can be operated manually or semi-automatically. Generally, one or more fork elements ride along one or more shift rails to shift a synchronizer into engagement with a transmission drive gear (e.g., intermeshing synchronizer gears with spline teeth). The synchronizer is coupled for co-rotation with the shaft, and thus, the engagement of the synchronizer with the gear also couples the gear to the shaft for co-rotation, thereby integrating the gear into the rotational force (or torque) path from the engine. A ratchet is mounted between the synchronizer and the gear to prevent displacement of the synchronizer until their gear teeth are timed with the gear teeth.The engagement and disengagement of the gear is therefore largely, if not entirely, mechanical, in the sense that the shift rail actuates the synchronizer back and forth relative to the gear. The shift rails and forks increase the complexity of the assembly, as well as the weight and space it occupies within the vehicle.

[0014] Certain other known synchronizers have been developed that utilize hydraulic power to couple transmission gears to the engine output shaft. Some of these utilize a shift rail and fork arrangement similar to the one described above, although shift fork movement is accomplished hydraulically. Other systems eliminate the shift rail and fork arrangement altogether. Instead, these systems direct hydraulic fluid into chambers that drive pistons to move shift sleeves into engagement with the gears. The shift sleeve is released from a gear by venting the pressure chamber, allowing one or more return springs to act on the piston and move the shift sleeve back to a neutral position. These systems can thus be considered hybrid mechanical-hydraulic systems in which each mode contributes to the actuation of the shift sleeves (i.e., the shift sleeves are hydraulically engaged and mechanically (spring) released).The spring mechanism increases the complexity of manufacturing and assembly and makes the synchronizer susceptible to failure (e.g., due to breakage or “sticking” of the springs).

[0015] This disclosure addresses some of the issues mentioned above and may provide various other benefits. In general, a fully hydraulic synchronizer is disclosed herein in which certain mechanical elements (e.g., shift rails, shift forks, actuating springs, etc.) of conventional synchronizers have been eliminated. Therefore, movement of the shift sleeves into on and off positions is accomplished hydraulically.

[0016] In certain embodiments, the disclosed hydraulic synchronizer operates to selectively couple one or more gears to a drive shaft via a shaft hub rotated by the drive shaft. The shaft hub may have a splined annulus and one or more fluid passages. A ring may be mounted around the shaft hub and movable along the shaft axis relative to the shaft hub. A shift sleeve may be coupled to the ring and may have a splined annulus. The shift sleeve splines may engage the shaft hub and, when the ring is engaged in an axial position, a gear. The shift sleeve may be disengaged from the splined annulus of the shaft hub when the ring is in a neutral position. The shift sleeve thus transmits rotational drive from the shaft hub to the gear when the ring is engaged in the axial position.Two hydraulic pistons can receive hydraulic fluid from the fluid passage to move the ring to the engaged and neutral axial positions. In certain embodiments, a second ring and shift sleeve can be provided on the shaft hub to selectively couple a second gear to the shaft hub, allowing the synchronizer to selectively couple either gear to the engine.

[0017] In certain embodiments, the hydraulic synchronizer may have a double-acting or two-way piston arrangement of each shift sleeve / gear that can be coupled to the shaft hub. Each piston arrangement may include a piston element of the associated ring that is actuated by hydraulic fluid in the chambers formed between the shaft hub and the ring. For example, each hydraulic chamber may be formed between spaced-apart annular walls extending radially from the ring and / or the shaft hub. In the case of multiple shift sleeve / gear arrangements, the rings may be nested radially inward / outward from each other, with the inner ring (and not the shaft hub) forming one wall of the chamber for the outer ring.

[0018] In certain embodiments, the hydraulic synchronizer may include a locking ring arranged to be mounted between the respective shift sleeve and the associated gear to prevent the ring from moving to the engaged axial position until an inner toothed annulus of the shift sleeve is rotationally aligned with a toothed annulus of the gear. The locking ring pivots about the rotational axis relative to the shift sleeve to enable alignment and engagement of the inner toothed annulus of the shift sleeve with the toothed annulus of the gear. A spring may bias the locking ring against the gear before the ring is engaged in the axial position. It is worth noting that in this arrangement, the spring is only used to bias the locking ring and does not actuate the shift sleeve, which is hydraulically or electro-hydraulically engaged and fully disengaged.

[0019] In certain embodiments, the spring may be retained by a spring retainer having a plurality of fingers between a toothed annulus of the clamping ring, which engages the inner toothed ring of the shift sleeve and allows the inner toothed annulus to engage the toothed ring of the gear when the ring is engaged in the axial position. A pin-slot arrangement may rotatably couple the clamping ring and the shaft hub. The pin and slot are configured to allow relative rotation of the clamping ring with respect to the shaft hub to enable pivoting of the clamping ring with respect to the shift sleeve.

[0020] Referring now to the drawings, the disclosed hydraulic synchronizer can be used in connection with a wide range of work vehicles, including agricultural tractors, as in Fig. 1. In this regard, while a tractor is illustrated and described herein as an exemplary work vehicle, one skilled in the art will recognize that the principles of the hydraulic synchronizer disclosed herein can be readily adapted for use in other types of work vehicles, including, for example, various other agricultural machines and other machines in the construction and forestry industries. Thus, the present disclosure should not be limited to applications associated with a tractor or the particular example tractor illustrated and described.

[0021] As in Fig. 1, the work vehicle 20 includes a vehicle frame 22. Supported by the vehicle frame 22 is a power source 24 that supplies power to a transmission 26. In one example, the engine 24 is an internal combustion engine, such as a diesel engine, controlled by an engine control module. It should be appreciated that other forms of power may be provided, such as a fuel cell, an electric motor, a hybrid gas-electric power plant, etc. The transmission 26 transfers power from the engine 24 to a suitable drivetrain coupled to one or more driven wheels 28 of the work vehicle 20 to enable the work vehicle 20 to travel over the terrain.In certain embodiments, the work vehicle 20 may include an electro-hydraulic system with one or more hydraulic pumps 30 and electro-hydraulic valves 32, operated by one or more controllers 34, to control operating modes of the transmission 26. Information related to the transmission (e.g., current drive mode or gear) may be communicated to the operator in an operator cab 38 via an operator interface 36 (e.g., display screen).

[0022] With reference now to Fig. 2 and Fig. 3, the transmission 26 may include one or more gears for forward and reverse movement of the work vehicle 20, including multiple forward range gears, such as gears 40, 42, for propelling the work vehicle 20 at various speeds. To shift between gears, such as between gears 40, 42, the transmission 26 may include one or more synchronizers, such as synchronizer 50 between gears 40, 42, all of which may be concentric with a rotational axis R extending from a drive shaft 54 ​​that delivers power from the engine 24. The gears 40, 42 may be mounted directly to smooth portions of the drive shaft 54 ​​or to various bushings or sleeves so that the drive shaft 54 ​​can rotate relative to the gears 40, 42 until one (but not both) of the gears 40, 42 is engaged by the synchronizer 50.The synchronizer 50 may be mounted to the drive shaft 54 ​​through a shaft hub 56, such as that attached to the drive shaft 54 ​​for continuous common rotation, such as via the mating splines 58 shown in . Fig. 3, or via other suitable toothed or multi-sided sections of the drive shaft and shaft hub. In this way, the engine torque is applied to the synchronizer 50 through the drive shaft 54 ​​and shaft hub 56, and when one of the gears 40, 42 is engaged.

[0023] With reference now also to Fig. 4 and Fig. 5, the hydraulic synchronizer 50 includes two annular bodies or rings mounted to the shaft hub 56. In the illustrated example, the hydraulic synchronizer 50 includes an inner ring 60 nested radially within an outer ring 62. The rings 60, 62 are configured to move axially relative to each other and to the shaft hub 56. The mounting of the rings 60, 62 to the shaft hub 56 forms a plurality of fluid chambers into which hydraulic fluid can be directed in a controlled manner to move either the inner ring 60 or the outer ring 62 axially away from the shaft hub 56 during gear shifting, i.e., coupling one of the gears 40, 42 to the input shaft 54.Controlled venting and filling of one or more of the fluid chambers causes the axially displaced ring 60, 62 to return to a neutral position, as well as the other ring 60, 62 to be axially displaced during shifting to another gear 40, 42.

[0024] The illustrated example of the hydraulic synchronizer 50 will now be described in detail for the purpose of providing one or more example arrangements for practicing the principles of this disclosure. However, it should be understood that other arrangements may be devised without departing from the scope of this disclosure. As shown, the shaft hub 56 is an annular component having a toothed central annulus 70 in which the teeth are oriented in the direction of the rotational axis R so as to engage the radially outwardly directed teeth 58 of the drive shaft 54 ​​to mesh together to transmit sufficient torque from the engine 24. From the central annulus 70, the shaft hub 56 extends radially outward along an axially narrowed body to a widened annular periphery 72.The annular periphery 72 defines a pair of spaced-apart toothed rings 74, 76, one on each axial side of a radial plane bisecting the shaft hub 56. The toothed rings 74, 76 are formed on an inner periphery of the annular periphery 72 such that the teeth project radially inward toward the rotational axis R. Two spaced-apart annular walls 78, 80 project radially outward from an outer side of the annular periphery 72, with a generally smooth cylindrical wall therebetween. The walls 78, 80 have grooved ends that support seals 82. In other embodiments, the shaft hub 56 may be formed primarily as a single, monolithic structure with the exception of the wall 80, which is a separate piece, retained by a snap ring 84 and sealed by an O-ring 86. The O-ring 86 may be retained in an annular groove 88 so that it is recessed below the outer peripheral surface of the shaft hub 56.

[0025] The inner ring 60 is an annular component having a main ring body 90 and a ring extension 92. The ring body 90 has two axially spaced annular walls 94, 96 extending radially inward and outward on radially inner and outer sides of the ring body 90, each with groove ends that support additional seals 82. The ring extension 92 is radially spaced from the outer circumference of the ring body 90 except where it joins the ring body 90. At plateau 98, the outer circumference of the ring body 90 extends radially outward on the axial side of the ring body 90 where the ring extension 92 joins and has a groove for another seal 82. In certain embodiments, the ring wall 96 and the ring extension 92 are separate parts from the ring body 90, connected by additional snap rings 84, as shown in the illustrated example.Another O-ring 86 may be provided to seal the annular wall 96. Like the groove 88 in the shaft hub 56, an annular groove 100 may contain this O-ring 86 so that it is recessed below the outer peripheral surface of the annular body 90. The outer ring 62 is an annular component having an annular wall 102 extending radially inward on a radially inner side of the outer ring 62 with a groove end supporting another seal 82. The outer ring 62 is sized and shaped to fit around the annular body 90 of the inner ring 60 and partially into the space between the annular body 90 and the annular extension 92.

[0026] The inner and outer rings 60, 62 respectively bind the first and second corresponding shift sleeves 110, 112. The shift sleeve 110 has an angled cross-section whose axial leg extends axially toward the shaft hub 56 and is radially spaced from the inner periphery of the annular body 90. The shift sleeve 110 defines a double-sided toothed annulus 120 with radially inward and outward directed toothings toward and away from the rotational axis R. The shift sleeve 112 has an angled cross-section whose axial leg extends axially toward the shaft hub 56 and is radially spaced from the inner periphery of the outer ring 62 and defines another double-sided toothed annulus 122 with radially inward and outward directed toothings toward and away from the rotational axis R.In certain embodiments, the shift sleeves 110, 112 are separate parts from the inner and outer rings 60, 62, which are connected by additional snap rings 84, as shown in the illustrated example.

[0027] Hydraulic fluid can be supplied to the hydraulic synchronizer 50 through various internal passages. As shown in Fig. For example, as shown in Figure 5, the drive shaft 54 ​​may have two or more (two shown) fluid passages 130a, 130b extending axially from openings at the end of the drive shaft 54 ​​that are coupled to hydraulic lines 132a, 132b leading from two associated electro-hydraulic valves 32a, 32b. Two radial fluid passages 134a, 134b may connect to the respective axial fluid passages 130a, 130b, one extending to fluid passage 136 and the other to fluid passage 138, each of which extends separately through the shaft hub 56. One or more (one shown) fluid passages 140 may branch off from the fluid passage 138. In certain embodiments, the fluid passages 138, 140 are formed as through holes in the shaft hub 56, after which the open end of the fluid passage 138 is closed by a plug 142, as shown in the drawings.

[0028] The fluid passages 130a / b, 134, 136, 138, and 140 supply hydraulic fluid to hydraulic chambers defined by the assembly of the shaft hub 56 and the inner and outer races 60, 62. When filled with pressurized hydraulic oil, the hydraulic chambers can be characterized as "hydraulic pistons" or "plungers," since the pressurized fluid drives movement of the hydraulic synchronizer 50. Alternatively, the components actuated by the pressurized fluid in the hydraulic chambers can be characterized as "pistons," since such components are the physical bodies that drive the movement. In either case, the driving force is generated by pressure applied to an area of ​​one or more walls of the inner and outer races 60, 62 from a limited, albeit variable, volume.For this reason, the exemplary hydraulic synchronizer 50 will be discussed below with respect to the configuration and flow to and from the “hydraulic chambers” formed in the hydraulic synchronizer 50.

[0029] In the illustrated example, there are four hydraulic chambers 150a, 150b, 150c, and 150d. Hydraulic chambers 150a and 150b are formed between the shaft hub 56 and the inner ring 60, and hydraulic chambers 150c and 150d are formed between the inner ring 60 and the outer ring 62. Vent channels 160, 162 in the inner ring 60 enable communication between the hydraulic chambers 150a and 150c and between the hydraulic chambers 150b and 150d, respectively. The hydraulic chamber 150a is axially delimited by the annular wall 78 of the shaft hub 56 and the annular wall 96 of the inner ring 60, and the hydraulic chamber 150b is axially delimited by the annular wall 96 of the inner ring 60 and the annular wall 80 of the shaft hub 56. The hydraulic chamber 150c is axially delimited by the annular wall 96 of the inner ring 60 and the annular wall 102 of the outer ring 62, and the hydraulic chamber 150d is axially delimited by the annular wall 102 of the outer ring 62 and the raised plateau 98 of the inner ring 60.There are six seals 82, in addition to the two O-rings 86, to seal the hydraulic chambers 150a-d, all of which provide a dynamic seal between relatively moving parts.

[0030] Generally, the shaft hub 56 rotates during operation and does not move axially. During shifting into and out of gear 42 (right in Fig. 5), the inner ring 60 slides axially relative to the shaft hub 56 and the outer ring 62, which is held in a neutral position, as in Fig. 5. During shifting into and out of gear 40 (left in Fig. 5), the outer ring 62 slides axially relative to the shaft hub 56 and the inner ring 60, which is held in a neutral position, as in Fig. 5. Thus, the annular wall 96 of the inner ring 60 may be characterized as a double-acting piston that axially displaces the inner ring 60 in either direction when pressurized. Similarly, the annular wall 102 of the outer ring 62 also functions as a double-acting piston that axially displaces the outer ring 62 in either direction when pressurized. The annular walls 78, 80 of the shaft hub 56 and the annular wall 94 and raised plateau 98 of the inner ring 60 serve to define the axial ends of the hydraulic chambers and provide mechanical end stops.

[0031] The hydraulic synchronizer 50 can be kept in neutral state as in Fig. 5, in one of two ways, namely, maintaining the hydraulic chambers 150a-d in open communication with the hydraulic pressure source (e.g., by opening or otherwise operating both control valves 32a, 32b in "pressure" mode), or by venting the hydraulic chambers 150a-d to the tank (e.g., by closing or otherwise operating the control valves 32a, 32b in "tank" mode). The first case is explained below. In the latter case, sufficient pressure can be maintained in the hydraulic chambers 150a-d to maintain the inner and outer races 60, 62 in their neutral positions by the centrifugal force resulting from the high-speed rotation of the hydraulic synchronizer 50.

[0032] Specifically, to move the inner ring 60 into the axial position, it is necessary to engage the shift sleeve 112, the control valve 32a is in pressure mode, and the control valve 32b is energized for tank mode. In this way, the hydraulic line 132a and the drive shaft fluid passages 130a, 134a are pressurized, as is the fluid passage 136 of the shaft hub 56. Since the fluid passage 136 is always in communication with the hydraulic chamber 150a, regardless of the axial position of the inner ring 60 (which is prevented from blocking or diverting the flow from the fluid passage 136 by interference of the shift sleeve 112 and the shaft hub 56), the hydraulic chamber 150a (and the hydraulic chamber 150c via the vent channel 160) are pressurized.Furthermore, fluid passages 138, 140 are always in communication with the hydraulic chamber 150b via the groove 88 in the shaft hub 56, regardless of the axial position of the inner ring 60, so that the hydraulic chambers 150b, 150d can be vented to tank through the fluid passages 130b, 134b, 138, 140, when pressure builds up from the reduction volume of these chambers resulting from the axial movement of the inner ring 60 from its neutral position, shown in . Fig. 6A into the locked position, shown in Fig. 6B.

[0033] By resetting both valves 32a, 32b to pressure mode, pressure is supplied (via hydraulic line 132b and fluid passages 130b, 134b, 138, 140) to hydraulic chamber 150b (and hydraulic chamber 150d via vent channel 162). The surface area of ​​the end face of the annular wall 102 in hydraulic chamber 150c is larger than that of hydraulic chamber 150d, so that outer ring 62 remains in the neutral position, shown in Fig. 6A. The surface area of ​​the end face of the annular wall 96 in the hydraulic chamber 150b is larger than that in the hydraulic chamber 150a, so that the force of the hydraulic chamber 150b will overcome that of the hydraulic chamber 150a and return the inner ring 60 to its neutral position, shown in Fig. 6A. As the inner ring 60 moves in either axial direction, fluid can flow through the vents 160, 162 in the direction from the hydraulic chamber decreasing in volume to the hydraulic chamber expanding. Any increase in pressure in the hydraulic chamber 150a from the reduced volume caused by the movement of the inner ring 60 back to neutral that exceeds the supply pressure is forced back into the reservoir via the appropriate passages and lines.

[0034] The gear 40 is engaged by moving the outer ring 62 from its neutral position, shown in Fig. 7A, into the necessary axial position to engage the shift sleeve 110, as shown in Fig. 7B. This is achieved by energizing the control valve 32a in tank mode and the control valve 32b in pressure mode, thereby pressurizing the hydraulic line 132b, as well as the drive shaft fluid passages 130b, 134b and the shaft hub fluid passage 138. Since the fluid passage 138 is always in communication with the hydraulic chamber 150b, regardless of the axial position of the inner ring 60, the hydraulic chamber 150b (and the hydraulic chamber 150d via the vent channel 162, which is always in communication with the hydraulic chamber 150b, regardless of the axial position of the outer ring 62) is pressurized.Furthermore, the fluid passage 136 is always in communication with the hydraulic chamber 150a (and hydraulic chamber 150c via the groove 100), regardless of the axial position of the inner and outer rings 60, 62, so that the hydraulic chambers 150a, 150c can be vented to the reservoir through the fluid passages 130a, 134a, 136 as pressure builds up from the reduction in volume of these chambers due to the axial movement of the outer ring 62 from its neutral position, shown in . Fig. 7A into the engagement position, shown in Fig. 7B.

[0035] By returning both valves 32a, 32b to pressure mode, pressure is supplied (via hydraulic line 132a and fluid passages 130a, 134a, 136) to hydraulic chamber 150a (and hydraulic chamber 150c via vent channel 160). The surface area of ​​the end face of the annular wall 96 in hydraulic chamber 150b is larger than that of hydraulic chamber 150a, so that inner ring 60 remains in its neutral position, shown in Fig. 7A. The surface area of ​​the end face of the ring wall 102 in the hydraulic chamber 150c is larger than that in the hydraulic chamber 150d, so that the force of the hydraulic chamber 150c overcomes that of the hydraulic chamber 150d and returns the outer ring 62 to its neutral position, shown in Fig. 7A. Like the inner ring 60, when the outer ring 62 moves in either axial direction, fluid can flow through the vents 160, 162 toward the hydraulic chamber that is decreasing in volume, toward the hydraulic chamber that is expanding. Any increase in pressure in the hydraulic chamber 150d from the reduced volume resulting from the movement of the outer ring 62 back to neutral that exceeds the supply pressure is forced back into the reservoir via the appropriate passages and lines.

[0036] Proper engagement of each of the shift sleeves 110, 112 with their respective gears 40, 42 is facilitated by a spring-loaded ratchet assembly that serves to physically restrict the axial movement of the shift sleeves 110, 112 (and thereby the inner and outer races 60, 62) into the path of the gears 40, 42 until the two components are timed, allowing the gear teeth of the shift sleeve to axially (or rotationally) engage the grooves between the gear teeth. Furthermore, since the shift sleeves 110, 112, and indeed the entire hydraulic synchronizer 50, continuously rotate with the input shaft 54, the ratchet is utilized to initiate rotation of the gear and bring it up to the speed of the input shaft 54. Only after the shift sleeve and the gear rotate together in the correct timing does the locking arrangement allow the shift sleeve to slide axially so that the teeth mesh.

[0037] With reference again to Fig. 3 and Fig. 5, in the illustrated example of the hydraulic synchronizer 50, there are two locking assemblies, one for each shift sleeve 110, 112 and associated gear 40, 42. Each locking device includes a locking ring 170a, 170b, a spring 172a, 172b, and a spring retainer 174a, 174b. The locking rings 170a, 170b are coupled to, and thereby rotatable with, the shaft hub 56 by pins 176a, 178b (formed on or attached to the shaft hub) that fit into corresponding openings in the locking rings 170a, 170b. The locking rings 170a, 170b have conical inner diameters configured to correspond to the tapers of the conical portions 180a, 180b of the gears 40, 42. As can be seen, the mating cones provide frictional engagement of the locking rings 170a, 170b with the cones 180a, 180b of the gears 40, 42 when the pair of components is brought together (ieThe locking rings are advanced axially toward the gears, allowing some relative rotation (or slippage) in the early stages of engagement. In certain embodiments, each inner diameter of the locking rings 170a, 170b may include (e.g., by bonding) a layer of friction material to help create a robust frictional connection between the locking rings 170a, 170b and the cones 180a, 180b. In such cases, cooling grooves and the like may be formed in the friction material to assist heat dissipation.

[0038] For the sake of simplicity and clarity, only the locking arrangement with the locking ring 170a will be described in detail, with reference to Fig. 8A-10B. However, it should be understood that the following discussion also applies to the locking arrangement with the locking ring 170b. As mentioned, the locking ring 170a rotates with the shaft hub 56 due to the engagement of the pin 176a with a slot 178a in the locking ring 170a. The slot 178a is elongated to allow limited relative rotation of the locking ring 170a with respect to the shaft hub 56. During shifting, as the inner race 60 moves axially to move the shift sleeve 112 toward the gear 42, the spring 172a urges the locking ring 170a against the gear 42. Initially, there is a difference in rotational speed between the locking ring 170a (and thus the rest of the synchronizer 50 and the input shaft 54) and the gear 42.The spring force acting on the locking ring 170a against the gear 42, along with the speed differential, creates a torque on the locking ring 170a, causing it to rotate relative to the shaft hub 56 until the pin 176a hits the end of the slot 178, after which it continues to rotate with the shaft hub 56. This positions the locking ring 170a in a position that interferes with the axial travel of the shift sleeve 112, as shown in FIG. Fig. 8A and Fig. 8B. As the shift sleeve 112 continues to move, the tooth tips of the gear teeth 122 are in contact with the tooth tips of the gear teeth 186a of the locking ring 170a. The angled tips create a torque on the locking ring 170a and attempt to free the locking ring 170a from the path of the gear teeth 122 of the shift sleeve 112. However, this torque encounters resistance from a torque from the engagement of the locking ring 170a (or its friction material) and the cone 180a of the gear 42, which is still rotating at a different speed. As the gear 42 accelerates or decelerates to match the speed of the synchronizer 50, the friction torque is dissipated by the cone 180a to allow the shift sleeve 112 to traverse the locking ring 170a, as shown in Fig. 9A and Fig. 9B. At this stage, the gear 42 cannot be clocked with the locking ring 170a, as shown. However, as the shift sleeve 112 continues to move, the tooth tip contact between the shift sleeve 112 and the gear 42 creates a torque that pivots the locking ring 170a slightly (as far as permitted by the pin 176a and slot 178a arrangement) until the teeth 122 of the shift sleeve 112 can be fully engaged with the teeth 184a of the gear 42, as shown in Fig. 10A and Fig. 10B. In this way, the shift sleeve 112 can engage and couple the gear 42 to the drive shaft 54 ​​smoothly and without excessive wear on the drive shaft 54, the gear 42, or the synchronizer 50.

[0039] The spring 172a is circumferentially captured by narrow prongs 188a of the spring retainer 174a, which fit between the teeth 122 of the shift sleeve 112. The spring retainer 174a may be "floated" within the synchronizer 50, in which case it is not rigidly mounted but rather is located around an outer periphery of the locking ring 170a. The spring 172a is compressed and slides into a groove 182a formed in the teeth 122 of the shift sleeve 112. As the shift sleeve 112 moves, the spring 172a applies an axial force against a radial face of the locking ring 170. The axial force is an axial component of the radial force acting on the spring 172a by engaging a ramp angle of the groove 182a of the shift sleeve 112. Thus, as the shift sleeve 112 moves toward the gear 42, the locking ring 170a is positioned to first engage the gear 42 to achieve the pivoting and rotational timing as described above.

[0040] Additionally, in certain embodiments, gear selection may be determined by one or more sensors that detect the axial position of the inner and outer races 60, 62. For example, proximity sensors 190a, 190b may be mounted within the transmission housing, proximate the circumferential flanges 192a, 192b that face radially outward from the outer periphery of the respective inner and outer races 60, 62. Other sensor technologies and sensed areas may be utilized, and the sensed positions of the inner and outer races 60, 62 may be used for various purposes. For example, the sensors 190a, 190b may be part of a feedback loop to the controller 34 to provide an input signal indicative of the state of the hydraulic synchronizer 50 and / or confirmation of the gear selection. The controller 34 may utilize this feedback to control the operation of the electro-hydraulic system, and in particular, the control valves 32.Controller 34 may also output a feedback signal to operator interface 36 to provide the operator with a visual indication of the currently engaged gear. Controller 34 may also monitor the feedback signals from sensors 190a, 190b for operating anomalies or for diagnostic purposes.

[0041] The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the disclosure. As used herein, the singular forms "a," "an," "the," "the," and "the" also include the plural forms unless the context indicates otherwise. Furthermore, any use of the terms "comprises" and / or "comprising" in this specification indicates the presence of stated properties, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other properties, integers, steps, operations, elements, components, and / or groups thereof.

[0042] The description of the present disclosure has been presented for purposes of illustration and description, but is not exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. Embodiments explicitly referred to herein were chosen and described in order to best explain the principles of the disclosure and their practical application, and to enable others skilled in the art to understand the disclosure and to recognize many alternatives, modifications, and variations to the described example(s). Accordingly, various implementations other than those explicitly described herein are within the scope of the claims.

Claims

[1] A hydraulic synchronizer (50) for selectively coupling one or more gears (42, 40) to a drive shaft (54) rotatable about an axis of rotation (R), the synchronizer (50) comprising: a shaft hub (56) configured to be rotated with the drive shaft (54), the shaft hub (56) having a first toothed rim (76, 74) and at least one fluid passage (136, 138, 140); a first ring (60, 62) mounted around the shaft hub (56) and movable along the axis of rotation (R) relative to the shaft hub (56); a first shift sleeve (112, 110) fixedly coupled to the first ring (60, 62), the first shift sleeve (112, 110) having a toothed rim (122, 120) that engages the first toothed rim (76, 74) of the shaft hub (56), the shift sleeve (112, 110) being configured to be disengaged from teeth (184a) of a first of the gears (42, 40) when the first ring (60, 62) is in a first neutral position and to engage the teeth (184a) of the first gear (42, 40) when the first ring (60, 62) is in a first axial position to provide rotational drive from the shaft hub (56) to the first gear (42, 40). transferred; and first and second hydraulic chambers (150a, 150b, 150d, 150c) configured to receive hydraulic fluid from the at least one fluid passage (136, 138, 140); wherein hydraulic pressure in the first hydraulic chamber (150a, 150d) acts on the first ring (60, 62) to move the first ring (60, 62) into the first axial position and hydraulic pressure in the second hydraulic chamber (150b, 150c) acts on the first ring (60, 62) to move the first ring (60, 62) into the first neutral position. [2] The synchronizer of claim 1, wherein the first and second hydraulic chambers (150a, 150b) extend axially between spaced-apart annular walls (78, 96, 80) extending radially from at least one of the first ring (60) and the shaft hub (56). [3] The synchronizer of claim 1, wherein the toothed rim (122, 120) of the first shift sleeve (112, 110) is a double-toothed rim (122, 120) having a set of radially inwardly projecting teeth and a set of radially outwardly projecting teeth; and wherein the outwardly projecting teeth are in engagement with the first toothed rim (76, 74) of the shaft hub (56). [4] The synchronizer of claim 3, further comprising a first locking ring (170a, 170b) arranged to be mounted between the first shift sleeve (112, 110) and the first gear (42, 40) when the shaft hub (56) is mounted to the drive shaft (54), the first locking ring (170a, 170b) preventing the first ring (60, 62) from moving to the first axial position until the radially inwardly projecting teeth of the first shift sleeve (112, 110) are rotationally aligned with the teeth (184a) of the first gear (42, 40); and wherein the first locking ring (170a, 170b) pivots about the rotational axis (R) relative to the first shift sleeve (112, 110) to enable alignment and engagement of the inwardly projecting teeth of the first shift sleeve (112, 110) with the teeth (184a) of the first gear (42, 40). [5] The synchronizer of claim 4, wherein the first locking ring (170a, 170b) is biased toward the first gear (42, 40) by a first spring (172a, 172b); and wherein the first spring (172a, 172b) is retained by a first spring retainer (174a, 174b) having a plurality of fingers (188a) disposed between a toothed rim (186a) of the first locking ring (170a, 170b) that engage the radially inwardly projecting teeth of the first shift sleeve (112, 110) and allow them to engage the teeth of the first gear (42, 40) when the first ring (60, 62) is in the first axial position. [6] The synchronizer of claim 5, further including a first pin (176a, 176b) rotationally coupling the first locking ring (170a, 170b) to the shaft hub (56); wherein the first pin (176a, 176b) enables relative rotation of the first locking ring (170a, 170b) with respect to the shaft hub (56) to enable pivoting of the first locking ring (170a, 170b) with respect to the first shift sleeve (112, 110). [7] Synchronizer according to claim 1, further comprising: a second ring (62, 60) arranged around the shaft hub (56) and movable along the axis of rotation (R) relative to the shaft hub (56); a second shift sleeve (110, 112) fixedly coupled to the second ring (62, 60), the second shift sleeve (110, 112) having a toothed rim (120, 122) engaging with a second toothed rim (74, 76) of the shaft hub (56), the shift sleeve (110, 112) being configured to be disengaged from toothings of a second (40, 42) of the gears, when the second ring (62, 60) is in a second neutral position and to engage the teeth of the second gear (40, 42) when the second ring (62, 60) is in a second axial position to transmit rotary drive power from the shaft hub (56) to the second gear (40, 42); and third and fourth hydraulic chambers (150d, 150c, 150a, 150b) configured to receive hydraulic fluid from the at least one fluid passage (136, 138, 140); wherein hydraulic pressure in the third hydraulic chamber (150d, 150a) acts on the second ring (62, 60) to move the second ring (62, 60) into the second axial position and hydraulic pressure in the fourth hydraulic chamber (150c, 150b) acts on the second ring (62, 60) to move the second ring (62, 60) into the second neutral position. [8] Synchronizer according to claim 7, wherein the first and second rings (60, 62) are arranged radially with respect to each other and the first ring is an inner ring (60) nested within the second outer ring (62). [9] The synchronizer of claim 7, wherein the third and fourth hydraulic chambers (150d, 150c) extend axially between spaced-apart annular walls (98, 102, 94) extending radially from at least one of the first ring (60) and the second ring (62). [10] The synchronizer of claim 7, wherein the toothed rim (120, 122) of the second shift sleeve (110, 112) is a double-toothed rim (120, 122) having a set of radially inwardly projecting teeth and a set of radially outwardly projecting teeth; and wherein the outwardly projecting teeth of the second shift sleeve (110, 112) are in engagement with the second toothed rim (74, 76) of the shaft hub (56). [11] The synchronizer of claim 10, further comprising a second locking ring (170b, 170a) arranged to be mounted between the second shift sleeve (110, 112) and the second gear (40, 42) when the shaft hub (56) is mounted to the drive shaft (54), the second locking ring (170b, 170a) preventing the second ring (62, 60) from moving to the second axial position until the radially inwardly projecting teeth of the second shift sleeve (110, 112) are rotationally aligned with the teeth (184a) of the second gear (40, 42); and wherein the second locking ring (170b, 170a) pivots about the rotational axis (R) relative to the second shift sleeve (110, 112) to enable alignment and engagement of the inwardly projecting teeth of the second shift sleeve (110, 112) with the teeth (184a) of the second gear (40, 42). [12] The synchronizer of claim 11, wherein the second locking ring (170b, 170a) is biased against the second gear (40, 42) by a second spring (172b, 172a); and wherein the second spring (172b, 172a) is retained by a second spring retainer (174b, 174a) having a plurality of fingers (188a) between a toothed rim (186a) of the second locking ring (170b, 170a) which engages the radially inwardly projecting teeth of the second shift sleeve (110, 112) and enables them to engage the teeth (184a) of the second gear (40, 42) when the second ring (62, 60) is in the second axial position. [13] The synchronizer of claim 12, further including a second pin (176b, 176a) rotationally coupling the second locking ring (170b, 170a) to the shaft hub (56); wherein the second pin (176b, 176a) enables relative rotation of the second locking ring (170b, 170a) with respect to the shaft hub (56) to enable pivoting of the second locking ring (170b, 170a) with respect to the second shift sleeve (110, 112). [14] A hydraulic synchronizer (50) for selectively coupling first and second gears (42, 40) to a drive shaft (54) rotatable about an axis of rotation (R), the synchronizer (50) comprising: a shaft hub (56) configured to be rotated with the drive shaft (54), the shaft hub (56) having first and second toothed rings (76, 74) and at least one fluid passage (136, 138, 140); first and second rings (60, 62) each arranged around the shaft hub (56) and movable along the axis of rotation (R) relative to the shaft hub (56); first and second shift sleeves (112, 110) which are fixedly coupled to the associated first and second rings (60, 62), wherein the first and second shift sleeves (112, 110) each have a toothed rim (122, 120) which is in engagement with the associated first and second toothed rims (76, 74) of the shaft hub (56), wherein the associated first and second shift sleeves (112, 110) are configured to engage with toothings (184a) of the associated first and second gears (42, 40) when the associated first and second rings (60, 62) are in the associated first and second axial positions and to be disengaged from the toothings (184a) of the associated first and second gears (42, 40) when the associated first and second Rings (60, 62) are in respective first and second neutral positions, wherein the first and second shift sleeves (112, 110) are configuredtransmit rotary drive from the shaft hub (56) to the associated first and second gears (42, 40) when the associated first and second rings (60, 62) are in the associated first and second axial positions; and, a plurality of hydraulic chambers (150a, 150b, 150d, 150c) configured to receive hydraulic fluid from the at least one fluid passage (136, 138, 140) and configured to move the first and second rings (60, 62) to the respective first and second axial positions and the respective neutral positions; wherein the first and second rings (60, 62) are prevented from being in the respective first and second axial positions simultaneously. [15] Synchronizer according to claim 14, wherein the first and second rings (60, 62) are arranged radially with respect to each other and the first ring (60) is an inner ring nested within the second outer ring (62). [16] The synchronizer of claim 14, wherein first and second of the hydraulic chambers (150a, 150b) extend axially between spaced annular walls (78, 96, 80) extending radially from at least one of the first ring (60) and the shaft hub (56); and wherein third and fourth of the hydraulic chambers (150d, 150c) extend axially between spaced annular walls (98, 102, 94) extending radially from at least one of the first ring (60) and the second ring (62). [17] The synchronizer of claim 16, further comprising first and second locking rings (170a, 170b) arranged to be located between the associated first and second shift sleeves (112, 110) and the associated first and second gears (42, 40) when the synchronizer (50) is mounted on the input shaft (54), the first and second locking rings (170a, 170b) preventing the associated first and second rings (60, 62) from moving to the associated first and second axial positions until inner toothed rims (122, 120) of the associated first and second shift sleeves (112, 110) are rotationally aligned with toothed rims (184a) of the associated first and second gears (42, 40). [18] The synchronizer of claim 17, wherein the first and second locking rings (170a, 170b) pivot about the rotational axis (R) relative to the associated first and second shift sleeves (112, 110) to facilitate alignment and engagement of the inner toothed rims (122, 120) of the associated first and second shift sleeves (112, 110) with the toothed rims (184a) of the associated first and second gears (42, 40). [19] A synchronizer according to claim 18, wherein the associated first and second locking rings (170a, 170b) are biased against the associated first and second gears (42, 40) by associated first and second springs (172a, 172b); and wherein the first and second springs (172a, 172b) are retained by associated first and second spring retainers (174a, 174b) each having a plurality of fingers (188a) between toothed rims (186a) of the associated first and second locking rings (170a, 170b) which engage the inner toothed rims (122, 120) of the associated first and second shift sleeves (112, 110) and enable the inner toothed rims (122, 120) of the associated first and second shift sleeves (112, 110) to engage the toothed rims (184a) of the associated first and second gears (42, 40) when the associated first and second rings (60, 62) are in the associated first and second axial positions. [20] The synchronizer of claim 19, further comprising first and second pins (176a, 176b) rotationally coupling the associated first and second locking rings (170a, 170b) to the shaft hub (56); wherein the first and second pins (176a, 176b) enable relative rotation of the associated first and second locking rings (170a, 170b) with respect to the shaft hub (56) to enable pivoting of the associated first and second locking rings (170a, 170b) with respect to the associated first and second shift sleeves (112, 110).

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