Disconnect mechanism for a tandem axle system

A vehicle includes a tandem axle system having an inter-axle differential and clutching assembly, a forward or first axle assembly, and a rear or second axle assembly. The inter-axle differential and clutching assembly includes a differential mechanism having first and second side gears and a clutch mechanism having a clutch member and an actuator assembly. At least one of the first axle assembly and the second axle assembly is in selective driving engagement with the inter-axle differential and clutching assembly.

BACKGROUND

Conventional tandem axle systems have two drivable axles for a vehicle. Such tandem axle systems typically include either 6×4 drivelines (i.e. two wheels on a steer axle and four driving wheels on a pair of tandem axles behind the steer axle) or 6×2 drivelines (i.e., two wheels on the steer axle and four wheels on the tandem axles behind the steer axle where only two wheels are on a drive axle). The 6×2 drivelines are often undesirable since they lack the required tractive effort under poor traction conditions. However, the 6×4 drivelines are also undesirable because under most driving traction coefficient conditions, two drive axles are not required to develop the necessary tractive effort for a truck, such as a Class 8 truck, Additionally, the 6×4 drivelines can be costly and heavy.

At startup, on grades, at low speeds, during backup maneuvering, or in other environments where additional traction is needed, it would be beneficial to operate a tandem vehicle in a 6×4 mode. However, as the tandem vehicle nears a predetermined speed or condition where less traction is required, operating the tandem vehicle in a 6×2 mode is more desirable as it increases efficiency.

In view of the disadvantages of the known prior art systems, it would be advantageous to develop a tandem axle system that allows a tandem vehicle to selectively operate in both the 6×2 and 6×4 modes.

SUMMARY

In concordance and agreement with the present disclosure, a tandem axle system that allows a tandem vehicle to selectively operate in both a 6×2 mode and a 6×4 mode, has surprisingly been discovered.

In one embodiment of the present disclosure, a tandem axle system comprises: a first axle assembly; a second axle assembly; and an inter-axle differential and clutching assembly coupled to at least one of the first axle assembly and the second axle assembly, wherein the inter-axle differential and clutching assembly includes an inter-axle differential having a differential mechanism and a clutch mechanism, wherein the differential mechanism includes a first side gear drivingly connected to one of the first and second axle assemblies, and a second side gear disposed about a pinion drivingly connected to of one of the first and second axle assemblies, and wherein the clutch mechanism includes a movable clutch member disposed on the pinion and configured to selectively engage the second side gear.

As aspects of certain embodiments, at least one of the first axle assembly and the second axle assembly includes a plurality of axle half shafts.

As aspects of certain embodiments, the differential mechanism further includes a bearing disposed between the second side gear and the pinion.

As aspects of certain embodiments, the clutch member is in splined engagement with the pinion.

As aspects of certain embodiments, the second side gear includes a plurality of first teeth and a plurality of second teeth formed thereon.

As aspects of certain embodiments, the clutch member includes a plurality of teeth formed thereon.

As aspects of certain embodiments, the teeth of the clutch member selectively engages the first teeth formed on the second side gear.

As aspects of certain embodiments, the second teeth of the second side gear are in meshed engagement with at least one pinion gear of the differential mechanism.

As aspects of certain embodiments, the differential mechanism is at least partially disposed in a housing.

As aspects of certain embodiments, the inter-axle differential further includes an inter-axle differential lock.

As aspects of certain embodiments, the inter-axle differential lock selectively engages the housing of the differential mechanism.

As aspects of certain embodiments, the inter-axle differential lock includes a main body having a plurality of teeth formed thereon.

As aspects of certain embodiments, the main body of the inter-axle differential lock is disposed about the second side gear.

As aspects of certain embodiments, the teeth of the main body of the inter-axle differential lock selectively engages a plurality of teeth formed on a housing of the differential mechanism.

As aspects of certain embodiments, the inter-axle differential further includes an actuator assembly configured to selectively engage and disengage at least one of the clutch mechanism and the inter-axle differential lock.

DETAILED DESCRIPTION

FIG. 1illustrates a vehicle10including a tandem axle system100according to an embodiment of the presently described subject matter. The tandem axle system100may be drivingly connected to a transmission (not depicted). The transmission may be drivingly connected to an engine of the vehicle10or other source of rotational power. In certain embodiments, the transmission can be, but is not limited to, an automated manual transmission, a dual clutch transmission, an automatic transmission or a manual transmission.

The tandem axle system100shown includes an inter-axle differential and clutching assembly102, a forward or first axle assembly104, and a rear or second axle assembly106. The first axle assembly104and the second axle assembly106are in selective driving engagement with the inter-axle differential and clutching assembly102. Although the axle assemblies104,106, as illustrated, are substantially similar in size and shape, it is understood that the axle assemblies104,106may have different sizes and shapes depending on the functions assigned to each, if desired.

In certain embodiments, the first axle assembly104may include a set of axle half shafts104a,104band a differential assembly (not depicted) drivingly connected thereto. Similarly, the second axle assembly106may include a set of axle half shafts106a,106b. As shown inFIGS. 2-3, the inter-axle differential and clutching assembly102may include a first housing portion103and a second housing portion or carrier105. Various shapes, sizes, and configurations may employed for each of the housing portions103,105such as the embodiments of the first housing portion103shown inFIG. 4and the second housing portion105shown inFIGS. 5-6. As a non-limiting example, the housing portions103,105are coupled to each other by a plurality of fasteners101. It is understood, however, that any suitable means of coupling the housing portions103,105together may be employed such as by mechanical and non-mechanical methods, if desired. It should be appreciated that additional housing portions may be employed or the housing portions103,105may be integrally formed as a unitary component if desired.

As illustrated inFIGS. 7-9, the inter-axle differential and clutching assembly102may further include an inter-axle differential (IAD)108disposed within the housing portions103,105. In certain embodiments, the IAD108includes a differential mechanism107disposed within a housing109and a clutch mechanism for axle disconnect110. In some embodiments, the differential mechanism107in the housing109is positioned within the housing position103and the clutch mechanism for axle disconnect110is at least partially positioned within both the housing portions103,105.

The IAD108is configured to divide a torque received from an input or source of torque (not depicted) between the first axle assembly104and the second axle assembly106. It should be appreciated that the IAD108may be used for other purposes and applications as desired. In certain embodiments, the torque is transferred from a driveline transmission of the vehicle10to the IAD108through an input shaft112formed with the housing109. It is understood that the input shaft112may be integrally formed with the housing109or as a separate and distinct component.

In the embodiment shown inFIGS. 7-9, the differential mechanism107of the IAD108may include a first side gear120, an opposing second side gear122, and a pair of opposing pinion gears124,125. Additional pinion gears (not depicted) may be employed as desired. In certain embodiments, the pinion gears124,125may be coupled to the housing109via respective pinion shaft127,128. The pinion shafts127,128may be configured to transfer the torque from the housing109of the IAD108to the pinion gears124,125. As illustrated, the first side gear120may be arranged to transfer the torque from the pinion gears124,125to a through-shaft130(depicted inFIG. 12). In certain embodiments, the first side gear120is disposed concentrically about the through-shaft130and coupled thereto for rotation therewith. Various methods of coupling the first side gear120to the through-shaft130may be employed such as by a splined engagement, for example. In certain embodiments, the through-shaft130may also be drivingly connected to the rear axle assembly106.

As shown, the second side gear122of the differential mechanism107may be arranged to selectively transfer the torque from the pinion gears124,125, through the clutch mechanism for axle disconnect110, to a hollow pinion140disposed concentrically about the through-shaft130. In some embodiments, as shown inFIG. 13, the second side gear122has a set of first teeth146formed on a first surface122aand a set of second teeth147formed on an opposing second surface122b. As a non-limiting example, the first teeth146of the second side gear122are configured to selectively mesh with the clutch mechanism for axle disconnect110and the second teeth147of the second side gear122are configured to mesh with a set of teeth (not depicted) formed on each of the pinion gears124,125. In certain embodiments, the second side gear122is mounted on a stem of the pinion140along with at least one bearing such as a needle roller bearing, for example, to allow free rotation about the pinion140.

In certain embodiments, the clutch mechanism for axle disconnect110includes a movable clutch member150and an actuator assembly151. The clutch member150is configured to selectively engage and disengage with the second side gear122. In certain embodiments, both of the second side gear122and the clutch member150are disposed concentrically about the pinion140and coupled thereto for rotation therewith. Various methods of coupling the second side gear122and the clutch member150to the pinion140may be employed such as by a splined engagement, for example. In certain embodiments, the clutch member150is coupled to the pinion140by a splined engagement to permit the clutch member150to translate axially along a longitudinal axis of the pinion140.

As more clearly shown inFIG. 9, the clutch member150is rotatably mounted on the stem of the pinion140. In certain embodiments, a set of splines (not depicted) on a radially inner surface153of the clutch member150may be engaged with a set of splines (not depicted) on a radially outer surface154of the stem of the pinion140. A set of teeth155(illustrated more clearly inFIG. 14) is formed on an axial end of the clutch member150to selectively engage with the teeth146(illustrated more clearly inFIG. 13) formed on the second side gear120. The clutch mechanism for axle disconnect110is axially movable along the stem of the pinion140by the actuator assembly151as shown inFIGS. 7-11to selectively engage and disengage the second side gear120. In some embodiments, the clutch mechanism for axle disconnect110selectively connects the IAD108to axle half shafts104a,104bof the forward axle assembly104through the pinion140. In certain embodiments, the actuator assembly151is used to position the clutch mechanism for axle disconnect110.

As a non-limiting example, the actuator assembly151may be a shift fork assembly using a pneumatic shifting mechanism to position the shift fork. It should be appreciated, however, that various other types of actuator assemblies may be employed as the actuator assembly151if desired. In certain embodiments, the actuator assembly151includes an actuator158(i.e. a shift fork shown inFIG. 15). In some embodiments, the actuator158may be connected to an axial first end159of a push rod160by a nut162. In other embodiments, the actuator158may be connected to the push rod160by any suitable method as desired. As shown, the actuator158is disposed at least partially about an outer circumferential surface of the clutch member150. The actuator158, depicted inFIG. 15, may include a first portion164and an opposing second portion166. As a non-limiting example, the portions164,166of the actuator158may be received into an annular groove168, more clearly illustrated inFIG. 9, formed in the clutch member150. In other embodiments, the actuator158may positioned adjacent the clutch member150opposite the second gear120.

Referring now toFIG. 10, the push rod160may have an axial second end170disposed in a cavity171formed in the second housing portion105. As illustrated, the push rod160may also have a biasing member172surrounding an outer surface of the push rod160inside the cavity171of the second housing portion105. A cap174is disposed on the second end170of the push rod160to limit an axial movement of the push rod160within the cavity171of the second housing portion105.

In certain embodiments, the IAD108may further include an inter-axle differential lock176configured to selectively engage and disengage with the housing109. As a non-limiting example, the inter-axle differential lock176is in a first or disengaged position when the clutch mechanism for axle disconnect110is in a first or engaged position, as shown inFIGS. 7 and 8, and the inter-axle differential lock176is in a second or engaged position when the clutch mechanism for axle disconnect110is in a second or disengaged position, as shown inFIG. 9. As more clearly illustrated inFIG. 10, the inter-axle differential lock176may include a main body178having a set of teeth180formed on an axial end surface and an annular groove182formed in an outer circumferential surface thereof. In the embodiment shown inFIG. 11, the teeth180may be configured to mesh with a set of teeth181formed on an end surface of the housing109of the IAD108for rotation therewith when the inter-axle differential lock176is in the first or engaged position.

In one embodiment, the inter-axle differential lock176may be caused to be selectively engaged and disengaged by an actuator assembly177. As a non-limiting example, the actuator assembly177may be a shift fork assembly using a pneumatic shifting mechanism to position the shift fork. It should be appreciated, however, that various other types of actuator assemblies may be employed as the actuator assembly177if desired. In certain embodiments, the actuator assembly177includes an actuator183(i.e. a shift fork more clearly shown inFIG. 10). In some embodiments, the actuator183may be connected to an axial first end186of a push rod184by a nut185. In other embodiments, the actuator183may be connected to the push rod184by any suitable method as desired. As shown, the actuator183is disposed at least partially about an outer circumferential surface of the main body178of the inter-axle differential lock176. The actuator183may include a first portion (not depicted) and a spaced-apart opposing second portion (not depicted). As a non-limiting example, the portions of the actuator183may be received into the annular groove182, more clearly illustrated inFIG. 10, formed in the main body178. Referring now toFIG. 10, the push rod184may have an axial second end (not depicted) disposed in a cavity179(depicted inFIG. 6) formed in the second housing portion105. A biasing member (not depicted) may be surround an outer surface of the push rod184inside the cavity179of the second housing portion105. A cap (not depicted) may be disposed on the second end of the push rod184to limit an axial movement of the push rod184within the cavity179of the second housing portion105. In another embodiment, the inter-axle differential lock176may be caused to be selectively engaged and disengaged with the housing109by the actuator assembly151, thereby employing only a single actuator assembly151for the IAD108.

Referring now toFIG. 1, the rear axle assembly106may include a differential assembly200. The differential assembly200is drivingly connected to a set of axle half shafts106a,106bof the rear axle assembly106. It should be appreciated that the differential assembly200may be any suitable differential assembly200as desired.

In some embodiments, the vehicle10may also include a control system (not depicted). The control system allows an operator of the vehicle10and/or the controller to control the tandem axle system100. The control system includes at least one controller and one or more sensors or a sensor array. The sensors can be intelligent sensors, self-validating sensors and smart sensors with embedded diagnostics. The controller is configured to receive signals and communicate with the sensors. The one or more sensors are used to monitor performance of the tandem axle system100. The sensors can collect data from the driveline of the vehicle including, but not limited to, the torque and rotational speed of at least one of the axle half shafts104a,104b,106a,106b. The speed of rotation and the torque are indicative of the speed of rotation and torque of the engine. In one embodiment, the sensors are mounted along at least one of the axle half shafts104a,104b,106a,106b, but can also be mounted elsewhere on the vehicle10. In one embodiment, the control system includes additional discrete sensors beyond sensors already included in other components of the vehicle.

The control system can also include a vehicle communication datalink in communication with the sensors and the controller. The sensors generate signals that can be directly transmitted to the controller or transmitted via the datalink or a similar network. In one embodiment, the controller can be integrated into an existing controller system in the vehicle including, but not limited to, an engine controller, a transmission controller, etc. or can be a discrete unit included in the control system. The controller may communicate a vehicle communication datalink message (comm. link J1939 or the like) to other components of the driveline including, but not limited to, the engine.

In one embodiment, the controller is an electrical control unit (ECU). The ECU herein can be configured with hardware alone, or to run software, that permits the ECU to send, receive, process and store data and to electrically communicate with sensors, other components of the driveline or other ECUs in the vehicle. Additionally, the controller can include a microprocessor. The microprocessor is capable of receiving signals, performing calculations based on those signals and storing data received from the sensors and/or programmed into the microprocessor. The control system allows an operator of the vehicle10and/or the controller to control the tandem axle system100. In some embodiments, the control system includes an axle control unit in communication with the clutch mechanism for axle disconnect110.

In some embodiments, the control system receives signals noting the vehicle10is moving above predetermined speed or condition and send a signal to the clutch mechanism for axle disconnect110to disconnect the front axle assembly104by disengaging the clutch member150from the second side gear122.

In operation, when a 6×4 mode of the vehicle10is desired, the clutch mechanism for axle disconnect110is caused to move to the first or engaged position in which the clutch member150engages with the second side gear122and the inter-axle differential lock176is caused to move to the first or disengaged position in which the main body178disengages from the housing109of the IAD108, the torque flows from the second side gear122to the pinion140of the front axle assembly104and the vehicle configuration changes from the 6×2 mode to the 6×4 mode as shown inFIGS. 7 and 8.

When a 6×2 mode of the vehicle10is desired, the clutch mechanism for axle disconnect110is caused to move to the second or disengaged position in which the clutch member150disengages from the second side gear122and the inter-axle differential lock176is caused to move to the second or engaged position in which the main body178engages with the housing109of the IAD108, the torque from the input shaft112is disconnected from the second side gear122of the IAD108of the front axle assembly104and the vehicle configuration changes from the 6×4 mode to the 6×2 mode as shown inFIG. 9.

The foregoing description details certain embodiments. It will be appreciated, however, that no matter how detailed the foregoing appears in text, the preferred embodiments can be practiced in many ways. As is also stated above, it should be noted that the use of particular terminology when describing certain features or aspects of the preferred embodiments should not be taken to imply that the terminology is being re-defined herein to be restricted to including any specific characteristics of the features or aspects of the embodiments with which that terminology is associated.