Transmission having torque measurement device

The invention relates to a transmission for a drive train of a motor vehicle, having a shaft section, to which a torque measurement device, designed to measure a torque applied to the shaft section is attached, wherein an electronics unit connected to the torque measurement device is received radially within the shaft section. The invention further relates to a drive train for a motor vehicle, having a transmission.

BACKGROUND

The invention relates to a transmission for a drivetrain of a motor vehicle, such as a passenger car, truck, bus, or other commercial vehicle, with a shaft section on which is mounted a torque measurement device that is designed for measuring a torque applied to this shaft section. The invention also relates to a drivetrain with this transmission.

Transmissions according to this class have been known for a long time from the prior art. In this context, e.g., EP 0 228 199 A2 discloses a tension sensor and a control arrangement for a CVT transmission.

Additional prior art is disclosed with WO 2016/050 241 A1, which shows a device for detecting a torque applied to a rotatably supported component. DE 10 2013 204 924 A1 shows a very similar construction for measuring a torque acting on a steering control shaft.

In CVT transmissions, the engine torque signal MMI is often used for the torque-related contact pressure between the respective drive and driven plate pairs. This signal, however, is relatively imprecise, especially in partial load operation. An excessive contact pressure between the individual plates of the drive and driven plate pair negatively affects, in turn, the transmission efficiency indirectly and unnecessarily increases the pump power consumption. However, the torque sensors previously used as an alternative for this purpose, especially torque sensors using hydraulic-mechanical effects, are associated with disadvantages with respect to the axial installation space and the high manufacturing expense.

SUMMARY

Therefore, the objective of the present invention is to eliminate the disadvantages known from the prior art and, in particular, to provide a transmission that is to be individually adjustable as much as possible to the respective operating state of the drivetrain, wherein simultaneously the use of installation space and the manufacturing expense of the transmission are to be further improved.

This objective is achieved according to the invention in that an electronics unit connected to the torque measurement device is mounted radially inside the shaft section.

By providing this torque measurement device, the installation space of the transmission is utilized more intensely or alternatively the installation space can even be reduced in comparison with known solutions. In addition, due to the close spatial arrangement of the electronics unit to the torque measurement device, the measurement accuracy is further increased. On the other hand, such a shaft section can be produced in an especially cost-effective way and can be easily installed during assembly.

Additional advantageous embodiments are explained in more detail below.

It is also advantageous if the transmission is a continuously variable transmission (also called CVT) that preferably has a drive plate pair and a driven plate pair that are actively interconnected by an endless traction mechanism, wherein the shaft section is then locked in rotation preferably with a (first) plate of the drive plate pair. In this way, the shaft section has an especially effective effect.

The torque transmitted by the shaft section during operation is used, in particular, for controlling the contact pressure forces, e.g., in the transmission, preferably the continuously variable transmission, in clutches, in converters, brakes, etc.

If the electronics unit is mounted/fastened onto a radial inner circumferential surface of the shaft section, the required installation space outside of the shaft section is further reduced. This is because the shaft section and its torque measurement device and electronics unit then form one module that is integrated into the transmission in the fewest possible work steps.

If the electronics unit has evaluation electronics that convert a measurement signal detected by the torque measurement device and corresponding to a torque applied to the shaft section/the (first) plate of the drive plate pair into a data transmission signal to be transmitted, the accuracy of the data transmission and the subsequent evaluation is further improved.

In addition, it is useful if the torque measurement device is, in turn, attached to a radial outer side of the shaft section and connected electrically to the electronics unit, preferably by a connecting line running in the radial direction. Thus, a direct electrical connection is implemented between the electronics unit and the torque measurement device.

If the torque measurement device has a strain measurement layer/strain-sensitive coating, which is preferably mounted directly on the radial outer side of the shaft section or, more preferred, on a sleeve formed separate to the shaft section but locked in rotation on the shaft section, the torque measurement device has an especially effective design.

If the shaft section has a tubular component that is preferably locked in rotation/connected to a gear shaft, preferably a transmission input shaft, a sub-gear unit, more preferably a planetary gear device, the shaft section is used in an especially clever and space-saving way preferably as an integral component of a driveshaft. The shaft section is used for forming the transmission as a continuously variable transmission in that the (first) plate of the drive plate pair is locked in rotation with a gear shaft.

In this context, it is also useful if the shaft section has a first tooth section (preferably in the form of a spline/serration) that engages locked in rotation with first mating teeth on the (first) plate and/or a second tooth section (preferably formed, in turn, as a spline/serration) that engages locked in rotation with second mating teeth on the gear shaft (preferably formed as an output rotating part, for example, a sun gear of the planetary gear device). In this way, the installation space of the transmission is used even more efficiently.

If a data transmission unit arranged between a housing and the shaft section that can rotate relative to the housing is connected to the electronics unit, the electronics unit can be connected in an especially clever way in operation with a central control unit of the motor vehicle.

In this context, it is especially advantageous if the data transmission unit has a bearing formed for transmitting data, preferably a roller bearing formed for transmitting data. In this way, data transmission can take place in an especially space-saving way.

Here it is also advantageous if the bearing formed for data transmission has a first bearing ring (preferably a bearing inner ring) that is locked in rotation with the (first) plate. With a second bearing ring (bearing outer ring) that can rotate relative to the first bearing ring in the bearing formed for transmitting data, the first bearing ring is then more preferably connected in a data-transmitting way, e.g., a non-contact way (by a rotor and stator antenna).

It is also advantageous if a first antenna element (rotor antenna) arranged on the first bearing ring is connected to the electronics unit in an electrical connection running in the radial direction. In this way, the space-saving construction of the transmission is further improved.

In this way, the electronics unit is connected to a central control unit by the data transmission unit that has at least the bearing formed for transmitting data and an electrical connection in a data-transmitting way, preferably also an energy-transmitting way, in the operating state of the transmission.

In addition, the invention relates to a drivetrain for a motor vehicle with such a transmission. In this way, the drivetrain also has an especially efficient design.

In other words, an electronic torque measurement is implemented in this way for determining a contact pressure force in a CVT unit. A torque measurement unit (torque measurement device) is proposed in which the measurement position and the necessary electronic components (electronics unit) are integrated inside the driveshaft (shaft section). The measurement principle is based on a strain-sensitive coating (strain measurement layer), preferably a Schaeffler Sensotect® coating. The data transmission unit is here a bearing of the CVT drive unit/transmission, which is arranged coaxial to the tubular component (shaft section) of the torque measurement unit.

DETAILED DESCRIPTION

The figures are only of a schematic nature and are to be used only for understanding the invention. Identical elements are provided with identical reference symbols.

In connection withFIG. 1, the construction of a continuously variable transmission1according to the invention described below is described in detail according to a preferred embodiment. The continuously variable transmission1(also called CVT unit) corresponds in its basic design and in its basic functioning to the variable transmissions already known from the prior art. As an example, a continuously variable transmission1′ from the prior art is shown inFIG. 2. The continuously variable transmission1′ of the prior art typically has, like the transmission1according to the embodiment according to the invention, which, however, for the sake of clarity cannot be seen completely inFIG. 1, a drive plate pair2and a driven plate pair3. The drive plate pair2is locked in rotation with the driven plate pair3by an endless traction mechanism4mounted so that it can move relative to these plate pairs2and3.

The drive plate pair2is locked in rotation inFIG. 2indirectly, as described in more detail below by a planetary gear device12, with a drive shaft22. In particular, a first plate5of the drive plate pair2is coupled with the drive shaft22(by the planetary gear device12). A second plate23of the drive plate pair2is supported so that it can move in the axial direction relative to the first plate5. Both plates5and23together form the drive plate pair2. In particular, both plates5and23have conical contact surfaces facing each other in the axial direction of the drive shaft22. The contact surfaces of the plates5and23run in the radial direction of the drive shaft22conically outward such that the axial distance between the contact surfaces of the plates5and23increases in the radial direction. The endless traction mechanism4is pressed onto the contact surfaces at a certain radial height, forming a friction-fit connection, as a function of the axial distance between the first plate5and the second plate23.

The driven plate pair3, as can also be seen inFIG. 2, has a similar construction and function with respect to the drive plate pair2. The driven plate pair3also has two plates, namely a first plate24and a second plate25. The plates24and25are locked in rotation with a driven shaft26. In particular, the first plate24of the driven plate pair3has a materially integrated construction with the driven shaft26. The material integration, however, is not mandatory. In other constructions, the first plate24is also mounted by a shrink-fitting or contact-pressing procedure.

The second plate25of the driven plate pair3is arranged so that it can move in the axial direction relative to the first plate24. Conical contact surfaces facing each other in the two plates24and25interact, in turn, with the endless traction mechanism4, forming a friction-fit connection. The respective relative position of the second plates23or25to the first plates5or24defines the gear ratio of the variable transmission1′,1. The driven shaft26is then typically connected to the wheels of the motor vehicle by several other teeth steps and a differential27of the drivetrain.

InFIG. 1, in particular, the differences of the transmission1according to the invention compared with the transmission1′ fromFIG. 2can be seen.

The transmission1is shown inFIG. 1in the area between the first plate5and a planetary gear/planetary gear device12of the transmission1. In particular, a shaft section6according to the invention, which is locked in rotation on the first plate5, is shown. The planetary gear device12represents a sub-gear unit of the transmission1. The planetary gear device12can also be replaced in other constructions by other transmissions/sub-gear units.

The shaft section6is a tubular component that is constructed separately from the first plate5/drive plate pair2. The shaft section6is used as an additional drive shaft/connection shaft. In particular, the shaft section6is a relatively short/axial short-build section.

A torque measurement device7is mounted on the shaft section6. This torque measurement device7has a strain measurement layer11that is connected rigidly to the shaft section6. The strain measurement layer11is constructed in this embodiment in the form of a sleeve component constructed separately from the shaft section6. The shaft section is fastened rigidly to the surface of the radial outer side10of the shaft section6(by multiple fasteners28). The fasteners28can basically have different constructions, for example, welded or bonded connections, alternatively, however, fastener pins could also be used. In addition, the strain measurement layer11could alternatively also be constructed as a direct coating of the shaft section6and mounted as a (material-fit) layer on the outer side10.

The torque measurement device7is always attached, together with its strain measurement layer11, on the outer side10of the shaft section6, so that it measures, in the operation of the transmission1, a torque transmitted by the shaft section6(between the planetary gear device12and the first plate5) and generates a measurement signal corresponding to the torque.

An electronic component/electronics unit8is also connected to the shaft section6for evaluating/converting the measurement signal of the torque measurement device7. This electronics unit8is arranged on a radial inner side36, namely a radial inner circumferential surface9, of the shaft section6. In particular, the electronics unit8is fastened/connected to this inner circumferential surface9.

The electronics unit8has several electronic components/parts that form, at least partially, the evaluation electronics for the transmitted measurement signal of the torque measurement device7. These evaluation electronics are designed to convert/change the measurement signal generated by the torque measurement device7into a data transmission signal suitable for data transmission. Here, the measurement signal that is detected directly by the torque measurement device7is processed/modulated accordingly, in order to generate the most exact possible data transmission signal that is forwarded, as described in more detail below, to the corresponding central control unit of the motor vehicle.

The torque measurement device7is connected in a data-transmitting and/or electrical way to the electronics unit8directly by the connecting line not shown in more detail here for the sake of clarity. Here, the electronics unit8is used both to construct a data connection with the torque measurement device7and maintain it during operation and also to supply electrical power to the torque measurement device7. For example, strain gauge sections of the strain measurement layer11that are not shown for the sake of clarity are connected during operation to a constant power supply provided by the electronics unit8, so that a bridge voltage changing with the strain/torque on the shaft section6is picked up. The connection line runs radially through the shaft section6.

The electronics unit8is further connected, during operation, to a central control unit not shown in more detail here for the sake of clarity, for example, an engine control module, of the motor vehicle, for transmitting data and also for transmitting electrical power. For this purpose, a data transmission unit19is provided in the transmission1.

The data transmission unit19has a bearing20in the form of a roller bearing, namely a ball bearing, which basically corresponds in its construction to the roller bearing disclosed in DE 10 2013 207 864 A1; therefore, the known construction is considered integrated herein in this context. The bearing20, however, is not limited to the construction as a ball bearing. The bearing20is constructed for data transmission. In particular, the bearing20has, on one axial side, two antenna elements29and30that are in active electrical connection to each other and form a wireless/non-contact (antenna) connection. However, a loop contact device or a coil device could also be provided as an alternative here, then with two loop contact elements/coil elements on the bearing20.

A first bearing ring31, in the form of a bearing inner ring, of the bearing20is locked in rotation on the first plate5of the drive plate pair2. A second bearing ring32of the bearing20is supported so that it can rotate via several roller bodies33relative to this first bearing ring31. The second bearing ring32is locked in rotation on a housing18of the transmission1(also designated as transmission case/transmission bell housing).

A first antenna element29/transmission element is mounted in the form of a rotor antenna on the first bearing ring31and is connected electrically to the electronics unit8. A second antenna element30/transmission element in the form of a stator antenna is mounted in an electrically conductive way on the second bearing ring32. The two antenna elements29and30are connected continuously in a wireless way in the operating state, so that a continuous (rotational position-independent) antenna connection/data and/or energy connection is produced between the housing18and the electronics unit8during operation.

As can also be seen, the first bearing ring31is locked in rotation on a bearing journal34of the first plate5, for example, by a type of splined key connection. This bearing journal34is penetrated in the radial direction by a connection channel35that is used for holding an electrical connection/connection line21. The connection channel35can be realized by a hole as inFIG. 1or preferably by a recess/indentation/groove that is formed in the end surface of the bearing journal34and in which the essentially radial connection line21is then inserted. The connection line21is connected electrically to the first antenna element29by a plug-in connection/connector receptacle on the first bearing ring31.

The data transmission unit19is thus formed on one hand by the bearing20, on the other hand by the electrically conductive material sections/components of the first plate5and the housing18. The data transmission unit19is designed so that the electronics unit8is connected during operation to a central control unit, on one hand, for data transmission and, on the other hand, also for receiving electrical energy that is provided by the control unit (directly or indirectly).

It can also be seen inFIG. 1that the shaft section6has a torque-transmitting section of the transmission1. The shaft section6is mounted in the flow of torque of the transmission1between the planetary gear device12and the first plate5. For the rotationally locked connection of the shaft section6to the first plate5or a transmission shaft17in the form of an output rotational part, namely a sun/sun gear, of the planetary gear device12, the shaft section6has two tooth sections13and14. Instead of the sun, another output rotational part of the planetary gear device12, for example, a connecting piece, could also be connected to the shaft section6in this way. The output rotational part is also not absolutely part of the planetary gear device12. The output rotational part can basically be part of any device changing direction of rotation. Sometimes, the device is also arranged downstream of the variator, then the measurement location is connected directly to the converter.

With a first tooth section13that is constructed in a first end area of the shaft section6on the radial outer side10, first mating teeth15engages in a rotationally locked way on a radial inner side of the first plate5. The tooth section13and mating teeth15together form a spline/serration. The second tooth section14is arranged on a second end area of the shaft section6opposite the first end area. The second tooth section14is also formed on the radial outer side10of the shaft section6. Second mating teeth16of the gear shaft17engage, in turn, in a positive-fit connection in this second tooth section14. Mating teeth16and tooth section14form a spline/serration. The torque measurement device7and electronics unit8are then arranged on the shaft section6, in turn, axially between these two tooth sections13and14.

In other words, according to the invention, a measurement location (the torque measurement device7) is integrated in a relatively installation space neutral way in the area of a drive shaft22of a CVT unit1. The non-positive-fit connection is realized by the planetary set/the planetary gear device12(for reversing the direction of rotation) by the torque measurement unit/device7on the first plate5of the CVT unit1. For the torque measurement, a tubular component6is used. The measurement principle is based on strain and is enabled with the help of a strain-sensitive coating11, preferably a Schaeffler Sensotect® coating. The sensor layer11thus can be either coated directly on the component6or attached with a material-fit connection on the component6in the form of a welded-on measurement sleeve. The required electronic components8are positioned inside the tubular component6. In other embodiments, the electronics8can also be stored in a separate component between the bearing20and sensor layer11. The measured signal is transmitted by a data transmission unit19from the rotating components to the signal-processing components that are spatially stationary with the transmission housing18, in order to then be able to process the signal further. The data transmission unit19is here a bearing20of the CVT drive unit1that is positioned coaxial to the tubular component6of the torque measurement unit7. The bearing20should be constructed here as disclosed in DE 10 2013 207 864 A1. The tubular component6is also constructed on its input and output side with a spline13,14, in order to connect the component easily to the connection partners. The signal connection from the tubular component6to the bearing inner ring31is realized by a cable connection21with a connector or alternatively by a connector-less connection (e.g., an adhesive, welded, and/or soldered connection). The bearing inner ring31is prevented from rotating relative to the gear shaft/first plate5, e.g., with a type of splined key connection (the cable connection is therefore protected). The signal connection from the tubular component6to the bearing inner ring31is realized by an antenna connection to the bearing inner ring31.

LIST OF REFERENCE SYMBOLS