Electricity: motive power systems – Miscellaneous
Reexamination Certificate
2000-04-26
2001-03-13
Ro, Bentsu (Department: 2835)
Electricity: motive power systems
Miscellaneous
C318S139000, C363S141000, C310S054000
Reexamination Certificate
active
06201365
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a drive unit in which an electric motor is used as a power source, and more particularly, to a cooling system in a drive unit for an electric vehicle or a hybrid drive unit.
2. Related Art
When an electric motor is used as a drive source for a vehicle, the load exerted on the electric motor varies significantly according to the running conditions. Accordingly, in order to manage the heat generated under a heavy load, cooling is necessary. Also, an electric motor requires a controller, e.g., an inverter in the case of an alternating current electric motor. Since a controller such as an inverter is connected to the electric motor with a power cable, it can be separated from the electric motor and mounted in an appropriate position. However, for mounting convenience in a vehicle, arrangements have also been used in which the inverter is integrated with the electric motor.
However, when the controller is integrated with the electric motor, not only does the temperature of the controller rise due to the heat generated by its own elements, but it is also affected by the heat from the electric motor and therefore requires cooling. Therefore, conventionally, where an electric motor has an integrated inverter, a heat sink for mounting the inverter is attached to a drive unit case, and a cooling water channel is formed between the heat sink and the drive unit case so as to simultaneously cool the motor and the inverter (see Japanese Patent Application Laid-Open No. 7-288949).
However, according to the conventional art construction as described above, because the same cooling water simultaneously cools the inverter and the electric motor, there is a problem of the heat from the electric motor being transferred to the inverter by the cooling water and the case.
SUMMARY OF THE INVENTION
Accordingly, an objective of the present invention is to prevent the heat of the electric motor from transferring to the inverter in a drive unit in which the electric motor and the inverter are cooled with a common coolant.
In order to achieve the foregoing objective, the present invention provides a drive unit comprising an electric motor; a drive unit case for accommodating the electric motor; an inverter fixed to the drive unit case for controlling the electric motor; and a flow passage for coolant for cooling the electric motor. The inverter is fixed to the drive unit case through an inverter panel, and a first chamber on the inverter side and a second chamber on the drive unit case side, divided by a partition wall, are arranged between the drive unit case and the inverter panel and are in communication with the coolant flow passage.
In the arrangement described above, the first chamber and the second chamber are preferably separated by an independent isolating means (partition wall) disposed on the inverter panel.
It is also preferred that the first chamber and the second chamber be in communication, in series, with the coolant flow passage, with the first chamber side disposed furtherest upstream.
Alternatively, the first chamber and the second chamber may communicate in parallel with the coolant flow passage.
It is also effective to arrange the above-described unit with the first chamber and the second chamber separated by an independent isolating means (partition) which prevents contact between the inverter panel and the drive unit case. Preferably, in such an embodiment, the isolating means is formed of a material having low heat conductivity.
In another preferred embodiment the inverter panel is constructed in the shape of a lid which contains the first chamber and the second chamber and which covers the drive unit case, the isolating means for separating the first chamber and the second chamber is disposed on the inverter side.
In yet another preferred embodiment the inverter panel is constructed in the shape of a lid which houses the first chamber and covers the drive unit case, and the independent isolating means (partition wall) for separating the first chamber and the second chamber is supported between the drive unit case and the inverter panel so as to prevent contact between the inverter panel and the drive unit case.
Furthermore, the isolating means which serves to separate the first chamber and the second chamber is preferably disposed nearer to the inverter than the drive unit case.
Because the space for coolant between the electric motor and the inverter is divided into two passages, one on the motor side and another on the inverter side, the coolant which flows therein acts as two heat insulating layers and it is possible to block the heat on the motor side, which becomes hotter than the inverter side, by absorbing it in two steps within the coolant space. Accordingly, it is possible to inhibit transfer of the heat from the motor to the inverter, and thus prevent the temperature of the inverter from rising due to the integration of the motor and the inverter.
Further, in the preferred embodiment wherein the isolating means is disposed on the inverter panel side, the isolating means serves as a barrier to heat transfer from the electric motor, and it is possible to inhibit heat transfer from the electric motor to the coolant which flows in the first chamber on the inverter side.
With the preferred embodiment wherein the first and second cooling chambers are connected in series with each other, it is possible to prevent the heat of the electric motor from transferring to the inverter through the coolant because the coolant flows so as to cool the electric motor after cooling the inverter.
On the other hand, with the first and second cooling chambers connected in parallel, it is possible to prevent the heat of the electric motor from transferring to the inverter through the coolant because the coolant flows independently through the first and second chambers, respectively.
In embodiments wherein the isolating means is an independent member and is disposed between the drive unit case and the inverter panel, the isolating means (partition) serves to insulate the inverter panel from the drive unit case and prevents heat transfer directly from the drive unit case to the inverter panel through their connecting portions.
In a preferred embodiment the inverter panel is formed as a lid defining both the first and second coolant chambers. In such an embodiment, the structure of the drive unit case can be simplified so that the inverter and the motor can be cooled with a simple structure. Moreover, since the isolating means is on the inverter panel, transfer of heat from the motor to the coolant which flows through the first chamber on the inverter side is inhibited by the isolating means.
Also, in preferred embodiments wherein the inverter panel contains the first chamber and wherein the isolating means is an independent member and is supported between connecting portions of the drive unit case and the partition wall, the isolating means serves as a heat insulator, impeding heat transfer between the connecting portions of the drive unit case and the inverter panel.
In preferred embodiments wherein the isolating means is closer to the inverter panel than to the surface portion of the drive unit case corresponding to the second chamber, the inverter panel may include a flange portion extending, beyond the isolating means, to the drive unit case to further suppress heat transfer to the inverter.
The teaching of Japanese Application No. 11-120286, filed Apr. 27, 1999, Japanese Application No. 11-356734, filed Dec. 15, 1999 and Japanese Application No. 2000-88590, filed Mar. 24, 2000, inclusive of their specifications, claims and drawings are incorporated herein in their entirety.
REFERENCES:
patent: 4711204 (1987-12-01), Rusconi
patent: 5631821 (1997-05-01), Muso
patent: 5670860 (1997-09-01), Conrady et al.
patent: 5905647 (1999-05-01), Shirai
patent: 6000912 (1999-12-01), Takada et al.
patent: 7-099750 (1995-04-01), None
patent: 7-288949 (1995-10-01), None
Agata Hiromichi
Hara Takeshi
Hotta Yutaka
Kido Takahiro
Kutsuna Naruhiko
Aisin Aw Co. Ltd.
Lorusso & Loud
Ro Bentsu
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