CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent Application No. 2019-056000 filed on Mar. 25, 2019, the entire contents of which are hereby incorporated by reference.

BACKGROUND

The disclosure relates to a gear unit mounted in a vehicle.

Most automobiles and other vehicles are equipped with gear units such as drive axles and transmissions, as disclosed in Japanese Unexamined Patent Application Publication Nos. 2008-286247, 2018-105419, and 2012-102856. A gear unit has a housing that contains oil to be supplied to a slide member, an actuator, and other internal parts during the running of the vehicle.

SUMMARY

An aspect of the disclosure provides a gear unit to be mounted in a vehicle. The gear unit includes a housing, a partition, and a helical gear. The housing is configured to store oil. Disposed inside the housing, the partition defines a first oil chamber and a second oil chamber and has a through-hole that allows the first oil chamber to communicate with the second oil chamber. Disposed inside the first oil chamber, the helical gear is configured to rotate during running of the vehicle. The helical gear has an angled tooth, a tip of which draws an addendum circle and a bottom of which draws a root circle. Both of the addendum and root circles define a virtual circumferential plane. The through-hole coincides with a portion of the virtual circumferential plane in an axial direction parallel to a central axis of the helical gear. When the helical gear rotates in conjunction with the running of the vehicle, the oil flows from the second oil chamber into the first oil chamber so that an oil level of the first oil chamber becomes higher than an oil level of the second oil chamber.

