Method for engaging and disengaging clutch elements of a transmission

A method selectively locks a notch plate to a pocket plate such that the notch and pocket plates rotate together. The pocket plate includes struts that work in opposite directions. The pocket plate rotational speed and the notch plate rotational speed are identified. Once the notch plate rotational speed is close to the pocket plate rotational speed, the struts in one direction are activated. Once seated, the struts in the other direction are activated. This two-step engagement of the struts provides a smoother transition between clutch engagements (gear shifts) while not requiring the precision of having all struts activated at the same time.

BACKGROUND ART

1. Field of the Invention

The invention relates to a method for shifting between two gears of a transmission. More particularly, the invention relates to a method for shifting between two gears of a transmission using digital coupling components.

2. Description of the Related Art

Transmissions in vehicles are used to control rotational torque to move the vehicle effectively and as efficiently as possible. Traditionally, transmissions employ hydraulic or pneumatic clutches (hydraulic clutches) to change gear ratios. Hydraulic clutches are, however, very inefficient in that much of the energy used to operate the hydraulic clutches is converted into thermal energy, much of which is dissipated into the atmosphere. In addition, hydraulic clutches require constant pressure to remain engaged, which further expends energy. This waste of energy is not acceptable in vehicles that use batteries as a primary energy source to create the motive force of the vehicle.

Digital clutches can be used to vastly reduce the amount of energy used during a change in gears of a transmission. Control of these digital clutches in the transmission are paramount to the proper function of the transmission. If a digital clutch does not transition properly, it could damage the transmission.

SUMMARY OF THE INVENTION

A method selectively locks a notch plate to a pocket plate such that the notch and pocket plates rotate at the same speed. The pocket plate subassembly includes at least one first direction strut and at least one second direction strut. The method includes the step of identifying a pocket rotational speed of the pocket plate. The method also identifies a notch rotational speed of the notch plate. The rotational speeds of the notch and pocket plates are modified so the rotational speeds are approximately equal. The at least one first direction strut is pivoted to extend out past the pocket plate which allows the at least one first direction strut to engage the notch plate. The notch rotational speed is then decreased to equal the pocket rotational speed allowing the at least one first direction strut to extend into the notch of the notch plate. The notch rotational speed is further reduced to less than the pocket rotational speed such that the notch plate engages the at least one first direction strut. The method then pivots the at least one second direction strut to engage the notch plate preventing relative motion between the notch and pocket plates in either direction.

DETAILED DESCRIPTION OF THE DRAWINGS

For purposes of this discussion, elements will be identified by reference characters, typically reference numerals. There are a few embodiments shown in the Figures that will be described in detail below. For purposes of simplicity, these elements will retain their reference characters throughout the discussion. If an element has characteristics that are different from one embodiment to another, those differences will be discussed when introducing the same element for the new embodiment.

Referring toFIG.1A, a perspective view of one embodiment of a transmission is generally shown at10. In this Figure, the transmission10is operatively connected to a first motor12and a second motor14. Physically, the second motor14is mounted to the transmission10between the transmission10and the first motor12. The first motor12has an output (discussed subsequently) that extends through the second motor14and to the transmission10.

The transmission10includes a transmission housing16having a housing cap20.FIGS.1A and1Bshow the second motor14(B-Motor) secured to the transmission housing16and the first motor12(A-Motor) secured to the second motor14(B-Motor). A first motor output shaft18of the first motor12(A-Motor) defines a length15that is longer than a length17of the first motor12. The first motor output shaft18also defines an outer diameter19at its distal end21.

The second motor14(B-Motor) includes a second motor output shaft21. The second motor output shaft21defines an inner diameter23that is larger than the outer diameter19of the first motor output shaft18. The first motor output shaft18extends through and is coaxial with the second motor output shaft21. It should be appreciated by those skilled in the art that the first motor output shaft18may not extend all the way through the second motor output shaft21.

In alternative embodiments that will be discussed in greater detail below, the first12and second14motors may be mounted on either side of the transmission10. Oil used to cool the transmission10, the first motor12and the second motor14is collected by a catch basin22and recirculated using a pump24, which is in fluid communication with the catch basin22. Because the catch basin22extends along the entire length of the transmission10, the first motor12and the second motor14, only one pump24is necessary. The transmission10has an output shaft26that extends out through the center of the housing cap20. Electrical ports (not shown) provide electrical access inside the first12and second14motors. The transmission10, first motor12, second motor14, and pump24may be referred to as a powertrain, generally shown at30.

Referring toFIGS.2and3, the powertrain30is shown mounted between two rails32,34of a vehicular frame, generally shown at36. A body40, including a passenger compartment (not shown), is shown fixedly secured to the vehicular frame36. Referring specifically toFIG.3, the transmission10is shown connected to a drive line38that drives four wheels (none shown).

Referring toFIGS.4and5, the transmission10is shown in a configuration for operating with a single input. In this configuration, the single input is the first motor12fixedly secured directly to the transmission housing16in the absence of the second motor14. The first motor12is not shown inFIG.4, but the first motor output shaft18would be received the input shaft44.

The input shaft44is also designated as shaft “1” in the power flow shown inFIG.5. The transmission10also includes a first gearset, generally shown at46, and a second gearset, generally shown at50. The first gearset46includes first52, second54and third56rotating members. The second gearset50includes a fourth60, fifth62, and sixth64rotating members. These gearsets46,50may be any gearset that has three rotating members. Types of gearsets contemplated include, but are not limited to, Ravigneaux gearsets, Simpson gearsets and ring-carrier/ring-carrier gearsets. The gearsets46,50shown inFIGS.4and5are ring-carrier/ring-carrier gearsets. Because these gearsets46,50are ring-carrier/ring-carrier gearsets, the first52, second54and third56rotating members are a sun gear, a carrier, and a ring gear, respectively. These are indicated as S1, C1, and R1for the first gearset46and S2, C2, and R2for the second gearset50. Two rotating members from the first gearset46and two rotating members from the second gearset50are fixedly secured to each other. These connections create a four-node linkage for the transmission10. As such, each pair of rotating members is represented by a single circle inFIG.5. Therefore, the first rotating member56(ring gear R1) and the fifth rotating member62(carrier C2) are fixedly secured to each other and represented by both reference numerals56and62inFIG.5, whereas the second rotating member54(carrier C1) and the sixth rotating member64(ring gear R2) are fixedly secured to each other and represented by both reference numerals54and64inFIG.5.

The output shaft26of the transmission10is also fixedly secured to two rotating members, one from each gearset46,50. In the embodiment shown inFIGS.4and5, the output shaft26is fixedly secured to the third rotating member56(the ring gear R1of the first gearset46and the fifth rotating member62of the second gearset50(the carrier C2of the second gearset50). The motor12is connected directly to the fourth rotating member60of the second gearset50using the input shaft44(shaft1).

A controllable clutch66is connected between the input shaft44(shaft1) at one end and the output shaft26(shaft3) at the other end. The controllable clutch66is also represented by the nomenclature K13because it couples shafts1and3together. Referring specifically toFIG.5, the controllable clutch66is represented by a switch70and two diodes72,74. These three elements70,72,74represent the attributes of the controllable clutch66. More specifically, the switch70signifies that the controllable clutch66may be turned on and off. The diodes72,74represent the fact that the controllable clutch66will the third rotating member56(ring gear R1), the fifth rotating member62(second carrier C2) and the output shaft26(shaft3) to lock in both directions, or to rotate freely in both directions. Therefore, when the switch70is closed, representing the active state for the controllable clutch66, the output shaft26rotates with the rotation of the input shaft44. When the switch70is open, representing an inactive state for the controllable clutch66, the output shaft26does not rotate or, alternatively, rotates based on the torques it receives from the other rotating elements52,54,60,64of the first46and second50gearsets.

The transmission10also includes a first controllable brake76(B04) that couples the first rotating member52(sun gear S1) of the first gearset46to the transmission housing16. The first controllable brake76also has the symbol B04because it is a brake that connects shaft0(which is just the transmission housing16) with a fourth shaft80(shaft4). The first controllable brake76(B04) is similar to the controllable clutch66in that it is represented by two diodes82,84representing that it will lock and allow rotation in either direction. The first controllable brake76(B04) is different from the controllable clutch66in that each direction of operation can be controlled independently of the other, as represented by switches86,90. Operation of the first controllable brake76will be discussed in greater detail subsequently.

This transmission10also includes a second controllable brake92(B05) which couples the second rotating member54(carrier C1) of the first gearset46and the sixth rotating member64(ring R2) of the second gearset50to the transmission housing16. The second controllable brake92differs from the first controllable brake76in that it only has the ability to control whether a notch plate94(shaft5) is rotating or if it is tied to the transmission housing16and prevented from rotating. As such, the second controllable brake92only includes a single switch96representing the two states of the second controllable clutch92(B05) as being either on or off, and two diodes100,102indicate that the second controllable brake92(B05) can lock or allow the notch plate94(shaft5) rotate in either direction.

Referring toFIG.6, a lever diagram showing the transmission10having two inputs (FIGS.1A and1B) is shown. The lever diagram is substantially similar to lever diagram for the single-input transmission shown inFIG.5. One difference between the two configurations is the transmission10has two input shafts44,126, wherein the first input shaft44receives torque from the first motor12(A-Motor) and the second input shaft126receives torque from the second motor14(B-Motor). Another difference between the two configurations is the use of two controllable clutches140(K23),142(K24) instead of the single controllable clutch66(K13).

The output of the first motor12(A-Motor) is received by the first input shaft44(shaft1), which is fixedly secured to the fourth rotating member60(sun gear S2) of the second gearset50. The output of the second motor14(B-Motor) is received by the second input shaft126(shaft2). The second input shaft126(shaft2) is connected to the first controllable clutch140(K23) and the second controllable clutch142(K24). The first controllable clutch140(K23) operates in both directions as is indicated by the diodes144,146, which are oriented in opposite directions. A switch150illustrates that the clutch140(K23) is controllable and may be locked or allowed to rotate in both directions. The second controllable clutch142(K24) operates in both directions, as is indicated by the diodes152,154, which are oriented in opposite directions. A switch156illustrates that the controllable clutch142(K24) is controllable and may be locked or allowed to rotate in both directions.

The first controllable clutch140(K23) couples the second input shaft126(shaft2) and the output shaft26(shaft3). The second controllable clutch142(K24) couples the second input shaft126(shaft2) with the fourth shaft80(shaft4). As discussed above, the output shaft26is fixedly secured to both the third rotating member56(ring R1) of the first gearset46and the fifth rotating member62(carrier C2) of the second gearset50.

The transmission10also includes a first controllable brake76(B04) that couples the first rotating member52(sun gear S1) of the first gearset46to the transmission housing16. The first controllable brake76also has the symbol B04because it is a brake that connects the transmission housing16(shaft0) with a fourth shaft80(shaft4). The first controllable brake76is similar to the controllable clutches140,142in that it is represented by two diodes82,84representing operation in either direction. The first controllable brake76is different from the controllable clutches140,142in that each direction of operation can be controlled independently of the other, as represented by the two switches86,90. Operation of the first controllable brake76will be discussed in greater detail subsequently.

This transmission10also includes a second controllable brake92(B05) which couples the second rotating member54(carrier C1) of the first gearset46and the sixth rotating member64(ring R2) of the second gearset50to the transmission housing16. The second controllable brake92differs from the first controllable brake76in that it only can control whether a notch plate94(shaft5) is rotating, or if it is tied to the transmission housing16and prevented from rotating. As such, the second controllable brake92only includes a single switch96representing the two states of the second controllable clutch92(B05) as being either on or off, and two diodes100,102indicate that the second controllable brake92(B05) can lock in both directions or it can move freely in both directions.

Because the first46and second50gearsets are ring-carrier/ring-carrier gearsets, the connections described in the power flow inFIG.5, and the first18and second19motor output shafts are coaxial, the second motor14(B-Motor) is able to drive the output shaft26(shaft3) directly. The number of modes of operation increase due to this capability. In the embodiments shown in the Figures, the first motor output shaft18extends through the second motor output shaft19. As such, the second motor output shaft19is hollow providing a space through which the first motor output shaft18extends.

InFIG.5, the steady-state lever104represent when the host vehicle is not in motion. The operational lever106represents when the vehicle is moving through the operation of the first motor12(A Motor) and/or the second motor14(B Motor). The first controllable clutch140(K23) is open as represented by the switch150being open. In addition, the second controllable clutch142(K24) is closed. Therefore, the second motor14(B Motor) is coupled to the first rotating member52(sun gear S1) of the first gearset46. The first rotating member52(sun gear S1) is not grounded to the transmission housing16because the first controllable brake76(B04) is open. Finally, the second controllable brake92(B05) is closed tying the second rotating member54(carrier C1) of the first gearset46and the sixth rotating member64(ring gear R2) of the second gearset50are ground to the transmission housing16through the notch plat94(shaft5).

In this configuration, the first motor12is operating in the forward direction, indicated by arrow160, and the second motor14is operating in the reverse direction, indicated by arrow162. By way of example, and in not to be limiting, exemplary torques are provided based on the designs of the gearsets46,50and the motors12,14. Given the output of the first motor12(A Motor) provides a torque of 1000 NM on the second sun gear60(sun gear S2) and the output of the second motor14provides a torque of 1000 NM in the opposite direction on the first rotating member52(sun gear S1) results in a torque of 4272 NM on the second rotating member54(carrier C1) of the first gearset46and the sixth rotating member64(ring gear R2) of the second gearset50and an output torque of 6272 NM at the output shaft26. This is “first gear.” The transmission10is more fully described in U.S. Pat. No. 10,711,867, which is co-owned by Applicant, and the disclosure therein is expressly incorporated herein by reference.

Referring toFIGS.7through10, clutch elements are shown in various stages of operation to facilitate the shifting of the transmission10. The clutch elements may be used for either brake clutches or controllable clutches. In the embodiment shown, the clutch elements are a part of the the first controllable brake76(B04). It should be appreciated by those skilled in the art that these clutch elements could be used with any of the independently controllable clutches used in this transmission10.

Referring specifically toFIG.7, the clutch elements shown include first200and second202actuators. In the embodiment shown, the first200and second202actuators are solenoids, each having a plunger204,206, respectively. The actuators200,202are fixedly secured to a pocket plate210using a mounting plate212and a plurality of bolts214. Electrical power to and control of the two actuators200,202come through a communications module as represented by a wire harness connector216as is known in the art. The plungers204,206extend through channels220,222, respectively, in the pocket plate210and into first224and second226pockets disposed adjacent to an inner diameter (244) of the pocket plate210. The channels220,222allow the plungers204,206to move axially between respective retracted positions (FIG.7) and extended positions (FIG.10) wherein distal ends230,232of the plungers204,206extend into the pockets224,226of the pocket plate210. The plungers204,206and channels220,222are linear and the plungers204,206move back and forth along the channels220,222, but they204,206,220,222may or may not be radial extensions of the notch plate250.

In each of the first224and second226pockets are first234and second236directional struts. The struts234,236reside in the pockets224,226. In their retracted positions, the struts234,236are completely within their respective pockets224,226. When the struts234,236pivot, an engagement portion240,242of the struts234,236move out beyond the pockets224,226past a pocket plate inner diameter244and into notches246of a notch plate250having an outer diameter252slightly smaller than the pocket plate inner diameter244. More specifically, the engagement portions240,242of the struts234,236engage respective notch walls238,239of the notches246. Position modules254,256identify the position of the struts234,236. Examples of position sensors are described in U.S. patent application owned by Applicant, having Ser. No. 17/495,062, the specification of which is hereby incorporated by reference. It should be appreciated by those skilled in the art that a clutch may include a plurality of these actuator/strut pairs and only a pair of these actuator/strut assemblies are shown in the Figures for purposes of simplicity.

FIG.7is a default starting position of the clutch elements using the method described herein. InFIG.7, all of the struts234,236are retracted into their respective pockets224,226. This allows the notch plate250to rotate freely with respect to the pocket plate210. In this embodiment, the pocket plate210does not rotate and is fixed to ground (typically, the transmission housing16). However, it should be appreciated by those skilled in the art that other embodiments can include a pocket plate that rotates independently of the notch plate250and with respect to the transmission housing16(ground).

Turning attention toFIG.11, the method used to operate the clutch elements is generally shown at300. The method300begins with commencing a clutch apply at302. As stated above, this occurs when the clutch elements are in the orientation shown inFIG.7, namely the first234and second236struts are fully retracted in their respective first224and second226pockets within the pocket plate210. The rotational speed of the notch plate250is identified at304as the notch rotational speed, and the rotational speed of the pocket plate210is also identified at306as the pocket rotational speed. Identification may occur through either measurement using speed sensors or through calculations based on the rotational speeds of other elements in the clutch and/or transmission10.

Once the respective rotational speeds of the notch250and pocket210plates have been identified, the method300controls the notch rotational speed to match it to the pocket rotational speed (even if the rotational speed of the pocket plate210is zero). Control of the relative rotational speed can be done using proportional integral derivative (PID) control. This step occurs at310inFIG.11. The matching of the rotational speeds of the notch plate250with that of the pocket plate210allows the first234and second236struts to pivot within their respective pockets224,226reduces the noise created by the clutch. “Match” as used herein implies that the rotational speeds are relatively close; they do not need to be identical. The notch plate250can be rotating slightly faster or slower than the pocket plate210for the two plates210,250to be considered matching. Matching rotational speeds allows for a positive and a negative difference in the rotational speeds between the notch250and pocket210plates.

It is determined at312whether the rotational speed of the notch plate250matches the rotational speed of the pocket plate210within a predetermined range. By way of example only, an acceptable range within which the method300would accept would be a relative difference less than 20 RPM. Obviously, the difference will be based on the actual configuration of the elements of the clutch and the transmission10. If it is determined that the relative rotational speed of the notch plate250is not within the predetermined range of the rotational speed of the pocket plate210, the method300loops back at314and continues to control the rotational speed of the notch plate250at310. A counter resets whenever the speed is not within the predetermined range requiring a loop back at314.

If it is confirmed that the rotational speed of the notch plate250is within the acceptable range based on the rotational speed of the pocket plate210, the method300then determines if the relative rotational speed of the notch plate250is within the acceptable range for a predetermined period of time at316. The counter will continue until the relative rotational speed falls out of the range or the predetermined period of time is met. If the rotational speed of the notch plate250is not within the acceptable range for the predetermined period of time, the method300loops back at320to continue controlling the rotational speed of the notch plate250at310.

Once the rotational speed of the notch plate250is within the acceptable range for the predetermined time, the method300activates the first clutch actuator200at322to pivot the first strut234such that the engagement portion of the first strut234extends beyond the pocket plate inner diameter244and is received by a notch246in the notch plate250. The orientation of the first strut234and the extension of the plunger204of the first clutch actuator200are shown inFIG.8.

After the engagement portion240of the first strut234exits one of the pockets224, the method300applies a negative or reverse torque to the notch plate250at324. This reverses the direction of rotation of the notch plate250. The negative torque apply is to ensure the engagement portion of the first strut234actually enters the notch246and engages the notch246. This forces the notch plate250into a reverse direction. The first strut234prevents the rotation of the notch plate in the reverse direction an amount equal 360 degrees divided by the number of notches246in the notch plate250. In one embodiment, this limitation is less than three degrees.

If the negative torque is large enough, it will force the first strut234to pivot further within the notch246and its pocket224. This additional rotation, which creates three points of contact between the first strut234, the notch246and the first pocket224is referred to as camming. The negative torque sufficient to create the camming will create an abutting relationship between a wall238of the notch246and the engagement portion240of the first strut234. The extended push rod ensures the first strut234will be retained within the notch246(possibly ratcheting in one direction). This is represented byFIG.9wherein the first strut234has been retained in the notch246(by virtue of contact with engagement surface with the notch wall238) even though the plunger204of the first clutch actuator200has been retracted and no longer is pushing the first strut234in any direction. In this condition, the clutch is engaged.

After the negative torque is applied, confirmation for the orientation of the first strut234is requested at326. If the first strut234orientation is not confirmed, the method300loops back at330to continue applying a negative torque to the notch plate250. If the first strut234orientation is confirmed, the second strut236is pivoted at332into a notch246of the notch plate250and the clutch is engaged at334. This condition is represented inFIG.10, wherein the notch plate250is locked with the pocket plate210.

Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.