Transaxle for electric vehicles

Abstract

The present invention provides a transaxle for an electric vehicle that provides lubrication to the gears of the differential gear system during the startup of the electric vehicle until forced lubrication is initiated. [Solution] A parking gear 40 is mounted on a reduction gear shaft 18a that is rotatable around an axis C2 parallel to the rotation axis C1 of the differential case 20a of the differential gear unit 20. The parking gear 40 overlaps with the opening 24 of the differential case 20a in the axial direction, and the outer teeth of the parking gear 40 are lower than the static oil level FL of the lubricating oil F in the transaxle case 22. When the electric vehicle 8 is started, the lubricating oil F scraped up by the parking gear 40 is supplied into the opening 24 provided in the differential case 20a. Therefore, when the electric vehicle 8 is started, the lubricity of the gears in the differential gear unit 20 is increased until forced lubrication is started.

Description

Technical Field

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[0001] The present invention relates to a technique for improving the initial lubricity of a differential gear device in a transaxle that transmits driving force from an electric motor to an axle.

Background Art

[0002] There is known a transaxle for an electric vehicle that houses an electric motor, a speed reducer, and a differential gear device in a transaxle case, reduces the rotation from the electric motor by the speed reducer and transmits it to the differential gear device, and transmits it to the axle via the differential gear device. For example, the drive unit of the electric vehicle described in Patent Document 1 is such an example.

Prior Art Documents

Patent Documents

[0007] In other words, the gist of the present invention is a transaxle for an electric vehicle in which (a) a reduction gear for reducing the rotation from an electric motor and a differential gear device for transmitting the rotation from the reduction gear to the drive wheels are housed in a transaxle case, and the differential case of the differential gear device is located higher than the static oil level of the lubricating oil in the transaxle case, (b) the reduction gear has a reduction gear shaft parallel to the rotation axis of the differential case of the differential gear device, and (c) a parking gear is provided on the reduction gear shaft such that it overlaps with an opening formed in the differential case in the axial direction, and the outer teeth of the parking gear are lower than the static oil level of the lubricating oil in the transaxle case. [Effects of the Invention]

[0008] According to the electric vehicle transaxle of the present invention, a parking gear is provided on the reduction gear shaft parallel to the rotation axis of the differential case of the differential gear, overlapping with the opening of the transaxle case in the axial direction, and the outer teeth of the parking gear are positioned lower than the static oil level of the lubricating oil inside the transaxle case. Therefore, when the electric vehicle is started, the lubricating oil scraped up by the parking gear is supplied into the opening provided in the differential case, thereby improving the lubricity of the gears of the differential gear until forced lubrication is initiated when the electric vehicle is started.

[0009] Preferably, the parking gear is positioned such that its axial position is within the axial range of the opening formed in the differential case in the axial direction. This allows the lubricating oil scraped up by the parking gear to be supplied more easily into the opening in the differential case, thereby further improving the lubrication of the gears in the differential gear system.

[0010] Preferably, the parking gear rotates at a higher speed than the differential case. This allows more lubricating oil scraped up by the parking gear to be supplied to the opening in the differential case. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram illustrating the configuration of the transaxle of the electric vehicle according to the present invention. [Figure 2] This diagram shows the side view of the transaxle in Figure 1, with the cover cut out. [Figure 3] This is a partial plan view showing the transaxle with the cover covering the side removed, as shown in Figure 1. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the following embodiments, the drawings have been simplified or modified as appropriate, and the dimensional ratios and shapes of each part are not necessarily accurately depicted. [Examples]

[0013] Figure 1 is a schematic diagram illustrating the configuration of the transaxle 10 of the electric vehicle 8 of the present invention. In Figure 1, the electric vehicle 8 is a vehicle equipped with an electric motor 12 as a power source. The transaxle 10 comprises a transaxle case (hereinafter referred to as the case) 22 that houses the electric motor 12 for driving, a reduction gear 18 and a differential gear device 20 that transmit the power of the electric motor 12 to a pair of left and right drive wheels 14 and 16. In Figure 1, the right side is the front of the electric vehicle 8. However, the right side may also be the rear of the electric vehicle 8.

[0014] The electric motor 12 is, for example, an AC synchronous motor, and is a so-called motor-generator that functions as both an electric motor and a generator. The electric motor 12 comprises a rotor 12a, a stator 12b, and a cylindrical rotor shaft 12c that supports the rotor 12a and is rotatably mounted in the case 22.

[0015] The stator 12b is fixed to the case 22 with a coil 12d wound around a cylindrical stator core and positioned on the outer circumference of the rotor 12a. The rotor shaft 12c is positioned to extend along the width direction of the electric vehicle 8 and is rotatably supported by the case 22 via bearings (not shown). The axial direction of the electric motor 12 is the width direction of the electric vehicle 8.

[0016] The differential gear unit 20 includes a differential case 20a rotatably mounted in a case 22 via a bearing (not shown) concentric with the rotor shaft 12c of the electric motor 12, with an opening 24 formed in its outer peripheral wall; a pair of side gears 20b, 20c mounted inside the differential case 20a and connected to a pair of left and right drive wheels 14, 16 via a pair of left and right axles 26, 28; and a pair of pinions 20e, 20f rotatably supported by a pinion shaft 20d between the pair of side gears 20b, 20c in a state of meshing with those side gears 20b, 20c.

[0017] The reduction gear 18 includes a reduction gear shaft 18a rotatably mounted on the case 22 around an axis C2 parallel to the rotation axis C1 of the rotor shaft 12c via a bearing (not shown), a first gear pair 16b consisting of an output gear 30 provided at the end of the rotor shaft 12c and a driven gear 32 fixed to the reduction gear shaft 18a and meshing with the output gear 30, and a second gear pair 16c consisting of a ring gear 34 provided on the differential case 20a and a drive gear 36 fixed to the reduction gear shaft 18a and meshing with the ring gear 34, and reduces the rotation of the electric motor 12 and transmits it to the drive wheels 14 and 16.

[0018] In the first gear pair 16b, the number of teeth (diameter) of the output gear 30 is smaller than that of the driven gear 32, so the reduction gear shaft 18a is rotationally driven at a lower rotational speed than the rotor shaft 12c. Also, in the second gear pair 16c, the number of teeth (diameter) of the drive gear 36 is smaller than that of the ring gear 34, so the differential case 20a is rotationally driven at a lower rotational speed than the reduction gear shaft 18a. That is, the reduction gear shaft 18a rotates at a higher rotational speed than the differential case 20a when the electric vehicle 8 is running.

[0019] A hydraulic pump 38 is provided at the shaft end of the reduction gear shaft 18a on the motor 12 side. When the hydraulic pump 38 is rotationally driven by the reduction gear shaft 18a that rotates as the electric vehicle 8 runs, the lubricating oil F that has refluxed to the lower part in the case 22 is pumped to each lubricating part such as bearings and gears, including inside the differential case 20a, so that forced lubrication is performed.

[0020] The case 22 includes a cylindrical main body case 22a, a left side cover 22b fixed to the main body case 22a so as to liquid-tightly close the opening on the left side of the main body case 22a, and a right side cover 22c fixed to the main body case 22a so as to liquid-tightly close the opening on the right side of the main body case 22a. The electric motor 12 is housed inside the left side cover 22b, and the left side cover 22b also functions as an electric motor case. The reduction gear 18 and the differential gear device 20 are housed inside the main body case 22a and the right side cover 22c.

[0021] FIG. 2 is a side view of the transaxle 10 with a part of the right side cover 22c cut away, and FIG. 3 is a plan view of the main part of the transaxle 10 with the right side cover 22c removed.

[0022] [[ID=​​​ As shown in Figure 2, the case 22 is positioned higher than the static oil level FL of the lubricating oil F that has recirculated to the lower part of the transaxle 10, while the parking gear 40 fixed to the reduction shaft 18a is positioned such that at least its inner circumferential teeth are lower than the static oil level FL of the lubricating oil F.

[0024] Furthermore, as shown in Figure 3, the parking gear 40 fixed to the reduction gear shaft 18a is positioned such that it overlaps with the opening 24 of the differential case 20a in the axial direction, preferably within the axial range A of the opening 24 formed in the differential case 20a in the axial direction.

[0025] In the transaxle 10 configured as described above, even when the electric vehicle 8 is started from a stationary state, especially after being left idle for a long period of time, some of the lubricating oil F scraped up by the rotation of the parking gear 40 is supplied into the opening 24 of the differential case 20a, so that the side gears 20b, 20c, the pinions 20e, 20f, and the pinion shaft 20d inside the differential case 20a are lubricated by the lubricating oil F. As a result, the lubrication of the side gears 20b, 20c, the pinions 20e, 20f, and the pinion shaft 20d inside the differential case 20a is enhanced when the electric vehicle 8 is started.

[0026] As described above, according to the transaxle 10 of the electric vehicle 8 of this embodiment, the reduction gear shaft 18a, which is rotatably mounted around an axis C2 parallel to the rotation axis C1 of the differential case 20a of the differential gear device 20, has a parking gear 40 that overlaps with the opening 24 of the differential case 20a in the axial direction, and the outer teeth of the parking gear 40 are positioned lower than the static oil level FL of the lubricating oil F in 22. Therefore, when the electric vehicle 8 is started, the lubricating oil F scraped up by the parking gear 40 is supplied into the opening 24 provided in the differential case 20a, thereby increasing the lubricity of the gears in the differential gear device 20 until forced lubrication is started when the electric vehicle 8 is started.

[0027] Furthermore, according to this embodiment, the parking gear 40 is positioned such that it is within the axial range A of the opening 24 formed in the differential case 20a in the axial direction. As a result, the lubricating oil F scraped up by the parking gear 40 is supplied more easily into the opening 24 provided in the differential case 20a, thereby further improving the lubrication of the gears in the differential gear unit 20.

[0028] Furthermore, according to this embodiment, since the parking gear 40 rotates at a higher speed than the differential case 20a, more lubricating oil F scraped up by the parking gear 40 is supplied into the opening 24 provided in the differential case 20a.

[0029] The above-described examples are embodiments of the present invention, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art, without departing from its spirit.

[0030] For example, in the above-described embodiment, a transaxle 10 of the type in which the electric motor 12 is housed inside the case 22 was described, but the electric motor 12 may be arranged outside the case 22. [Explanation of Symbols]

[0031] 8: Electric vehicle, 10: Transaxle, 12: Electric motor, 14, 16: Drive wheels, 18: Reducer, 18a: Reducer shaft, 20: Differential gear, 20a: Differential case, 22: Transaxle case (case), 24: Opening, 40: Parking gear, F: Lubricating oil, FL: Oil level, C1: Rotation axis, A: Axial axis range

Claims

1. A transaxle for an electric vehicle, wherein a reduction gear for reducing the rotation from an electric motor and a differential gear system for transmitting the rotation from the reduction gear to the drive wheels are housed within the transaxle case, and the differential case of the differential gear system is positioned higher than the static oil level of the lubricating oil inside the transaxle case, The reduction gear has a reduction gear shaft parallel to the rotation axis of the differential case of the differential gear device, The reduction gear shaft is provided such that the parking gear overlaps axially with an opening formed in the differential case, and the outer teeth of the parking gear are lower than the static oil level of the lubricating oil in the transaxle case. A transaxle for an electric vehicle characterized by the following features.

2. The parking gear is positioned such that its axial position is within the axial range of the opening formed in the differential case in the axial direction. A transaxle for an electric vehicle according to feature 1.

3. The parking gear rotates at a higher speed than the differential case. A transaxle for an electric vehicle according to the features of 1 or 2.

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