Press-fit tone wheel for a speed-sensing apparatus

A planetary gearset is provided in a transmission for a vehicle. The planetary gearset includes a carrier that rotates about the axis. Tone wheels can be used as part of a speed-sensing mechanism in which the tone wheel includes surface features on an outside surface, and a speed sensor senses the surface features as they rotate about the axis and past the speed sensor. The tone wheel is connected to the carrier via a press-fit or interference-fit. To do so, the tone wheel includes legs or flanges that extend inward from an inner surface of the tone wheel. The legs or flanges flex as the tone wheel is pressed onto the carrier. The legs or flanges securely attach the tone wheel to the carrier.

TECHNICAL FIELD

This disclosure generally relates to a tone wheel configured to interact with a speed sensor. More particularly, the tone wheel is for a planetary gearset and is configured to attach via an interference fit with a gear of the planetary gearset.

BACKGROUND

Modern vehicles include a plethora of electronic sensors that provide information to one or more controllers. One such sensor is a rotational speed sensor that detects the speed of a rotating component. A tone wheel can either be formed integrally with the rotating component or attached to it. The tone wheel includes slots, grooves, or other surface features. As the rotating component rotates, the surface features of the tone wheel also rotate and an electrical pulse is generated each time a surface feature rotates past the sensor.

Transmissions in vehicles have many rotating parts, and a speed of the rotating parts is helpful in many different control settings. One example of a mechanism in a transmission with rotating parts is a planetary gearset. Planetary gearsets include a sun gear, planet gears, a planet carrier, and a ring rear. Any one of these gears can be configured to rotate about the central axis. The detected rotating speed of one of these gears can typically make the rotational speeds of the other gears known through the given gear ratio of the planetary gear set. For example, a tone wheel may be provided about and secured to the carrier to make the speed of the carrier known; hence, the speed of the sun and planet gears also known.

SUMMARY

In one embodiment, a transmission includes a planetary gearset having a carrier. An annular-shaped tone wheel is connected to the carrier, and has an inner-diameter surface and an outer-diameter surface. The tone wheel further includes a pair of legs extending inward from the inner-diameter surface. An interference fit is provided between the legs and the carrier.

In another embodiment, a tone wheel for a transmission of a vehicle is provided. The tone wheel has a body having a convex outer surface, a concave inner surface, and a plurality of flanges. The outer surface has a plurality of surface features arranged annularly thereon about a central axis. The flanges extend inward from the inner surface toward the central axis. Each flange has a mating surface for contacting a carrier. The mating surface is axially offset from the inner surface of the body.

In yet another embodiment, a method of assembling a planetary gearset is provided. The method includes connecting a plurality of planet gears to a carrier, wherein the carrier has a plurality of surfaces each located between adjacent planet gears. The method also includes press-fitting a pair of legs of a tone wheel onto each surface to secure the tone wheel to the carrier.

DETAILED DESCRIPTION

Referring to1-4, a planetary gear set10for a transmission of a vehicle is illustrated. The planetary gearset10includes a sun gear (not shown) that shares a central axis with that of the gearset10. Radially outward from the sun gear are three planet gears14. The planet gears14include meshing teeth16that correspond to teeth on the sun gear. As the sun gear rotates, each of the planet gears14rotates about its own respective axis.

A carrier18is driveably connected to each of the planet gears14. The carrier18can transfer rotational movement to and from the planet gears14such that the planet gears14can rotate in unison about the sun gear. As the carrier18rotates about the central axis, the planet gears14rotate about the central axis and their own individual axis as well.

A tone wheel is illustrated generally at20, and shown in isolation inFIGS. 2 and 3. The tone wheel20couples to the planet carrier18to rotate with the carrier with the same rotational speed. Functioning as part of a rotational speed sensor, rotation of the tone wheel20is sensed to determine the rotational speed of the carrier18and thus the rotational speed of other components within the planetary gearset through known mathematical gear relationships.

The tone wheel20is generally round in shape and therefore includes a general diameter. The tone wheel20includes an outer-diameter surface22. A continuous series of grooves, holes, undulations, or other such surface features24are stamped, formed, or otherwise provided on the outer-diameter surface. As will be described below with reference toFIG. 5, a pulse is created by a sensor when these surface features pass by the sensor. The speed or frequency of the pulse corresponds to the rotational speed of the tone wheel20.

Utilizing a tone wheel20enables a vehicle controller to determine the rotational speed of the carrier and other portions of the planetary gearset10. Accurate determination of the rotational speed of these components is useful for knowing the speeds going into and out of the planetary gear set.

During assembly of the planetary gearset10, the tone wheel20must be installed onto the carrier18after the planet gears14and the carrier18are assembled together. Welding the tone wheel20to the carrier18can increase the risk of contamination getting into the planet gears and bearings of the planetary gearset10. And, typical press-fit applications deform surfaces of the pressed part to assure a tight fit. Precise location and clearance between the tone wheel20and the associated sensor is imperative for accurate speed readings.

According to the present disclosure, the tone wheel20of the planetary gearset10is provided with structure that enables it to be press-fit onto the carrier18. This eliminates the need for the time, expense, and potential contaminants that come naturally with welding.

To accomplish the press-fit, the tone wheel20includes an inner-diameter surface30with a plurality of legs32extending therefrom. The legs32are relatively flexible in that they can flex relative to the inner- and outer-diameter surfaces22,30of the tone wheel20. This allows the legs32to be pressed onto the carrier18and deform to assure a secure press-fit without deforming the outer-diameter surface22on which the surface features24are provided. In other words, the legs32provide a surface to be press-fit onto an associated surface of the carrier18while maintaining the shape of the outer-diameter surface22.

The legs32can come in pairs. As shown inFIG. 1, for example, the tone wheel20includes three pairs of legs32, with each pair contacting one corresponding contact region34of the carrier18. This embodiment is beneficial for a three-planet-gear gearset in which the carrier includes three regions that extend over and between two of the planet gears14. As illustrated inFIG. 1, the contact regions34can be flanges that extend from an area axially-outward of the planets14toward and in-between the planets14. The legs32can contact opposing sides of this contact region34of the carrier18. Between two of the pairs of legs32are concave regions36of the inner-diameter surface30. This provides clearance for the individual planet gears14to rotate.

The tone wheel20shown in the figures is but one embodiment in which the tone wheel20has three sets or pairs of legs32for each of three contact regions34of the carrier. This corresponds to the planetary gearset having three planet gears14. However, it should be understood that more or less than three planet gears14can be provided, and as such, the carrier18can be designed to have more or less than three contact regions34that extend between a respective pair of planet gears14. This can lead to a design of the tone wheel20having more or less than three pairs of legs32. For example, the planetary gearset10may have five planet gears, and the tone wheel20can include five pairs of legs32, with each pair of legs32contacting one respective contact region of the carrier.

To make an interference-fit or press-fit secure between the tone wheel20and the carrier18, a mechanical press (not shown) may be utilized. The press can be hydraulically equipped or otherwise capable of providing a large press force to the tone wheel20. The mechanical press can be operated to press the tone wheel20along the carrier18in the direction of the central axis of the planetary gearset10. As the tone wheel20is pushed along the carrier, the legs32are the first and only part of the tone wheel20to contact the carrier18. The legs32deform slightly outward from the central axis and provide resistance against the contact regions34of the carrier18. When the press is finished pressing the tone wheel20onto the carrier18, a secure interference fit is provided between the legs32and the contact region34.

As the legs32come in pairs, each pair of legs32provide an interference fit with the carrier18at two separate locations. Each pair of legs provides two loading points per contact region34of the carrier18. If three pairs of legs32are provided, as illustrated in the figures, then six different loading points are provided. With six different loading points, the mechanics of the deflection of forces with the interference fit is generally hexagonal in shape. If, in contrast, the tone wheel were to have single weld spots or the like to secure the tone wheel to the carrier, only three loading points would be provided and therefore the mechanics of deflection would be triangular in shape. Utilizing pairs of legs32to have additional loading points reduces the magnitude of deflection forces at each loading point by spreading the load to additional load points.

To further assist with a secure press-fit, the legs32are axially offset from the main portion of the tone wheel20. In particular, the tone wheel20includes an interior body portion40that extends from the inner-diameter surface30. This interior body portion40may extend about the entire inner-diameter surface30, and also includes other regions such as the concave regions36. The legs32extend from the interior body portion40and away from the inner-diameter surface and toward the central axis of the tone wheel20. The legs32also extend in a direction along the central axis from the interior body portion40such that the legs32are axially offset from the main body portion40. This provides the legs32with a contact surface42that is axially offset from the main body portion40for engaging with the contact region34. Thus, the point of engagement between the carrier18and the tone wheel20can be axially offset from the interior body portion40and inner-diameter surface30of the tone wheel20. Having an axially-offset location of contact allows the tone wheel to bend and yield during fitting in a non-functioning area.

As explained above, the legs32provide a mechanism to allow an interference fit between the carrier18and the tone wheel20with minimal or no distortion of the outer-diameter surface22of the tone wheel itself during assembly. This enables the tone wheel20to maintain a critically-accurate and relatively small clearance between the tone wheel20and an accommodating speed sensor50at all locations along the outer-diameter surface22. This is shown inFIG. 5. When the tone wheel20spins with rotation of the carrier18, a pulse is generated by the sensor50when the surface features24pass by the sensor50. The speed or frequency of the pulse corresponds to the rotational speed of the tone wheel20. A gap or clearance52between the sensor50and these surface features24can be about 1 mm, and between 0.5 and 1.5 mm in preferred embodiments. Maintaining the size and consistency of this gap52as the tone wheel20spins is important for accuracy of speed readings. The legs32assure the outer-diameter surface22is not distorted during the process of fitting the tone wheel20to the carrier18. This maintains the gap52at a preferable size.

To further a secure fit between the tone wheel20and the carrier18, nubs54may extend away from each leg32. The nubs can be arranged such that when the tone wheel20is fitted onto the carrier18, each contact region34can be held within a pair of the nubs54on either end of the contact region. The nubs can also be used as locating features to quickly align the tone wheel20to the carrier prior to press-fitting.