JP4036083B2 - Power transmission device for electric vehicles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power transmission device for an electric vehicle that transmits a rotational force of a motor from a motor rotation shaft to a drive shaft via a transmission and a differential mechanism.
[0002]
[Prior art]
A motor used in an electric vehicle may generate electrical noise on the motor rotation shaft.
[0003]
For example, noise generated by the operation of the switching element in the inverter that drives the motor is transmitted to the motor rotation shaft through some path, or is generated by electromagnetic action between the motor stator and the rotation shaft. Can be considered.
[0004]
Noise generated in the motor rotation shaft may adversely affect, for example, a radio receiver, making it difficult to listen to the radio, and may cause malfunction of electronic devices inside or outside the vehicle. For this reason, it is necessary to take measures to prevent each electronic device from being affected by noise.
[0005]
As a countermeasure, a method of grounding the motor rotation shaft to the vehicle body (so-called body grounding) is effective. By electrically connecting the motor rotation shaft and the vehicle body, noise of the motor rotation shaft can be released to the ground through the vehicle body and the wheels. For this purpose, electrical continuity between the motor rotating shaft and the vehicle body must be realized.
[0006]
A conventional technique for realizing electrical continuity between the motor rotation shaft and the vehicle body will be described below.
[0007]
The first conventional technique is as follows.
[0008]
The rotational force from the motor is transmitted from the motor rotation shaft to the drive shaft via the transmission and differential mechanism. In the path, for example, a motor rotation shaft, a gear shaft in the transmission, a drive shaft, and the like are supported by the case via bearings. The bearing case is fixed to the vehicle body. That is, the motor rotation shaft is electrically connected to the vehicle body via the bearing.
[0009]
The second conventional technique includes the following.
[0010]
The brush is brought into contact with the motor rotation shaft. For example, this brush is attached to a transmission housing or the like in order to achieve electrical continuity with the vehicle body. That is, in this example, electrical continuity is realized between the motor rotating shaft and the vehicle body via the brush.
[0011]
In this case, since the contact resistance between the motor rotation shaft and the brush is small, for example, the electrical connection between the motor rotation shaft and the vehicle body is smaller than in the case of using a bearing as in the first prior art. It can be expected that the conduction is improved.
[0012]
As a third conventional technique, there is one described in Patent Document 1.
[0013]
That is, in contrast to the first conventional technique, the conductive grease is filled in the bearing, and the electric conduction characteristic between the motor rotating shaft and the vehicle body is improved as compared with the case of the first conventional technique. Is possible.
[0014]
[Patent Document 1]
JP 2000-310296 A
[Problems to be solved by the invention]
However, the above conventional techniques have the following problems.
[0016]
According to the first conventional technique, the rolling elements and the washer in the bearing are each made of metal, and the mutual contact is through an oil film such as lubricating oil. For example, when the bearing is a ball bearing, the contact between the rolling element and the raceway is point or line contact, and when the bearing is a roller bearing, line contact. Therefore, the contact area between the rolling element and the raceway is reduced, the contact resistance is increased, and sufficient electrical conduction is not realized.
[0017]
In the second conventional technique, the brush is brought into direct contact with the motor rotation shaft by surface contact, so that the contact resistance therebetween becomes small.
[0018]
However, since the brush is brought into contact with the moving part of the motor rotation shaft, problems such as noise generation and brush wear occur with the rotation of the motor rotation shaft.
[0019]
In the first place, when a brushless motor is used instead of a brushed motor to avoid brush wear and noise as a motor, the brush is attached to the motor rotating shaft to achieve electrical continuity between the motor rotating shaft and the vehicle body. Contacting is nonsense.
[0020]
In addition, bringing the brush into contact with the rotating motor rotation shaft hinders rotation and causes loss. If the rotation is fast, that is, if the torque is large, the loss increases.
[0021]
In the third conventional technique, the contact resistance at the bearing is reduced by the conductive grease as compared with the first conventional technique. However, as in the case of the first prior art, the contact between the rolling element and the bearing disc is a contact at a point or a line.
[0022]
Furthermore, in the first place, it is desirable for the bearing to have a contact area as small as possible so that the shaft rotates smoothly, that is, in order to reduce mechanical resistance. However, in order to reduce the electrical resistance, it is desirable to increase the contact area. Therefore, if an attempt is made to maintain the properties that the original bearing should have, the electrical resistance increases and noise cannot be removed.
[0023]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reliably remove noise generated on a motor rotation shaft without hindering rotation of the motor.
[0024]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a power transmission device for an electric vehicle that transmits a rotational force of a motor from a motor rotation shaft to a drive shaft via a transmission and a differential mechanism. The gear or planetary carrier constituting the planetary gear is switched to become an input element, an output element or a fixed element according to the transmission gear ratio required for the operation of the electric vehicle, and between the gears constituting the planetary gear. And the motor rotating shaft is mechanically fixed to and electrically connected to a gear or planetary carrier that is an input element of the planetary gear, and is also a gear or planetary that is an output element of the planetary gear. The carrier is mechanically connected to the differential mechanism. A conductive member that electrically connects the gear or planetary carrier that is a fixed element of the planetary gear and the vehicle body, and the motor rotation shaft is connected to the gear or planetary that is the input element. The vehicle body is electrically connected to the vehicle body via a carrier, a gear or planetary carrier serving as the fixing element, and the conductive member.
[0025]
【The invention's effect】
According to this invention, the motor rotating shaft is electrically connected to the vehicle body via the gear or planetary carrier serving as the input element, the gear or planetary carrier serving as the fixed element, and the conductive member provided on the fixed element. As a result, noise generated on the motor rotation shaft can be reliably removed without hindering the rotation of the motor.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0027]
FIG. 1 is a schematic diagram showing an overall configuration of a power transmission device for an electric vehicle according to an embodiment of the present invention. A rotational force is input from the motor rotating shaft 3 of the motor 1 to the planetary gear 7 constituting the transmission 5.
[0028]
In the planetary gear 7, one member of the gear or the planetary carrier constituting the planetary gear 7 serves as an input element, and the rotational force of the motor rotating shaft 3 is input to this input element. The planetary gear 7 or another member of the planetary carrier serves as a fixed element, and the other member serves as an output element to output rotational force. The output from the output element is transmitted to the differential mechanism 11 via the propeller shaft 9 and further transmitted to the drive shaft 13.
[0029]
The above-described planetary gear 7 or planetary carrier is switched to become an input element, an output element, or a fixed element according to the gear ratio of the transmission 5 necessary for the operation of the electric vehicle.
[0030]
FIG. 2 is a schematic cross-sectional view showing the internal structure of the transmission 5 described above. The planetary gear 7 in the transmission 5 includes a sun gear 15, a ring gear 17, a plurality of pinion gears 19, and a planetary carrier 21 that connects the pinion gears 19 to each other. Storing.
[0031]
The sun gear 15, the ring gear 17, and the planetary carrier 21 are provided with brushes 25, 27, and 29 as conductive members that can be brought into contact with each other. These brushes 25, 27, and 29 are installed in the casing 23 of the transmission 5 via a metal spring that will be described later.
[0032]
One member of the sun gear 15, the ring gear 17 and the planetary carrier 21 is always a fixed element, but when it becomes a fixed element, a brush corresponding to the fixed element is attached to a gear or planetary carrier serving as the fixed element. Contact.
[0033]
The brush corresponding to each element does not contact the gear or planetary carrier that is not the fixed element but the input element and the output element.
[0034]
FIG. 3 shows a meshing portion between the gears 31 and 33 in the planetary gear 7. Conductive grease 35 is provided at the meshing portion between the gears 31 and 33.
[0035]
Next, a method for bringing the brushes 25, 27, and 29 shown in FIG. 2 into contact with the corresponding sun gear 15, ring gear 17, and planetary carrier 21 will be described.
[0036]
Here, the brush 25 corresponding to, for example, the sun gear 15 among the three brushes 25, 27, and 29 will be described, but the same structure can be adopted for the other brushes 27 and 29.
[0037]
FIG. 4 is a schematic view in which the brush 25 described above is integrated with a multi-plate clutch 37 as a connecting and fixing means. The brush 25 is connected via a metal spring 39 to the casing 23 of the transmission 5 that is electrically connected to the vehicle body.
[0038]
And the sun gear 15 becomes a fixed element by pressing the multi-plate clutch 37 against the connecting plate portion 15a of the sun gear 15 in the right direction in the figure. At the same time, the brush 25 corresponding to the sun gear 15 elastically contacts the connecting plate portion 15a by the action of the metal spring 39, and electrical conduction is realized between the motor rotating shaft 3 and the vehicle body.
[0039]
According to the above-described embodiment, the motor rotating shaft 3 is connected to the gear or planetary carrier serving as the input element, the gear or planetary carrier serving as the fixed element, and the brush 25 (27, 27, 27, 27 that contacts the gear or planetary carrier serving as the fixed element. 29), the noise generated in the motor rotating shaft 3 can be reliably removed without interfering with the rotation of the motor 1.
[0040]
Further, in this case, since the brush 25 (27, 29) contacts the gear or planetary carrier as a fixed element, the loss of the motor 1 can be prevented and the brush 25 (27, 29) and the motor accompanying the rotation of the motor 1 can be prevented. Noise between the rotating shaft 3 and wear of the brush 25 (27, 29) can be avoided.
[0041]
Further, by using the brushes 25, 27, 29 as the conducting members, the contact between the brushes 25, 27, 29 and the gears or the planetary carrier can be made a surface contact. Since it is not line contact, low contact resistance can be expected, and electrical conduction characteristics between the motor rotating shaft 3 and the vehicle body are improved.
[0042]
Moreover, a structure can be simplified by using brush 25,27,29 for each gearwheel or planetary carrier. For example, when one brush is to be brought into contact with all the gears or the planetary carrier, a mechanism for moving the brush by a distance that can be brought into contact with all the gears or a member to be fixed from each gear and the planetary carrier is selected. A mechanism is required, and the configuration becomes complicated.
[0043]
By providing a brush that contacts each gear and each planetary carrier, there is no need to move the brush or select a target member to be contacted, and the mechanism for switching the brush between a contact state and a non-contact state can be simplified. it can.
[0044]
In addition, since the mechanism (multi-plate clutch 37) is used to make one member of the gear or the planetary carrier as a fixed element, the brush is brought into contact with the gear or the planetary carrier, so that another mechanism such as a fixed element is used. It is not necessary to add a complicated mechanism for detecting a gear or a planetary carrier to be driven and driving a mechanism for bringing the brush into contact with the gear or the planetary carrier as a fixing element.
[0045]
In the first place, the mechanism of fixing the gear and the planetary carrier is a mechanism originally provided in the transmission 5. If the brush is brought into contact with a gear or a planetary carrier serving as a fixing element by utilizing this, it is possible to minimize the configuration added for ensuring the conductivity by the brush.
[0046]
In addition, as shown in FIG. 3, by providing the conductive grease 35, the electrical continuity characteristics between the gears 31 and 33 in the planetary gear 7 are improved. Thereby, the electrical conduction state between the motor rotating shaft 3 and the vehicle body, which is the object of the present invention, is improved.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an overall configuration of a power transmission device for an electric vehicle according to an embodiment of the present invention.
2 is a schematic cross-sectional view showing an internal structure of a transmission in the power transmission device for an electric vehicle in FIG.
FIG. 3 is an explanatory view showing a meshing portion of gears in a planetary gear of the power transmission device for an electric vehicle of FIG. 1;
4 is a schematic view in which a brush in the electric vehicle power transmission device of FIG. 1 is integrated with a multi-plate clutch.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Motor 3 Motor rotating shaft 5 Transmission 7 Planetary gear 11 Differential mechanism 13 Drive shaft 15 Sun gear (gear)
17 Ring gear (gear)
21 Planetary carrier 25, 27, 29 Brush (conductive member)
35 conductive grease 37 multi-plate clutch (connection fixing means)

Claims (5)

In a power transmission device for an electric vehicle that transmits a rotational force of a motor from a motor rotation shaft to a drive shaft via a transmission and a differential mechanism,
The transmission is composed of planetary gears,
The gear or planetary carrier constituting the planetary gear is switched to become an input element, an output element or a fixed element according to the transmission gear ratio required for the operation of the electric vehicle,
Electrically connecting each gear constituting the planetary gear,
The motor rotation shaft is mechanically fixed and electrically connected to a gear or planetary carrier serving as an input element of the planetary gear,
A gear or planetary carrier that is an output element of the planetary gear is mechanically fixed to the differential mechanism and electrically conducted,
A gear or planetary carrier, which is a fixed element of the planetary gear, and a conductive member that electrically connects the vehicle body;
Electric motor power characterized in that the motor rotating shaft is electrically connected to the vehicle body via a gear or planetary carrier serving as the input element, a gear or planetary carrier serving as the fixed element, and the conducting member. Transmission device. 2. The power transmission device for an electric vehicle according to claim 1, wherein conductive grease is provided at a meshing portion between the gears constituting the planetary gear. The power transmission device for an electric vehicle according to claim 1 or 2, wherein the conducting member is installed for each gear or planetary carrier constituting the planetary gear. The conducting member is provided in a connection fixing means for using one of the plurality of gears or planetary carrier constituting the planetary gear or a planetary carrier as a fixing element, and the connection fixing means allows the one gear or The power transmission device for an electric vehicle according to any one of claims 1 to 3, wherein when the planetary carrier is a fixed element, the conducting member is brought into contact with the fixed element. 5. The power transmission device for an electric vehicle according to claim 1, wherein the conductive member is a brush that is in surface contact with a gear or a planetary carrier serving as the fixing element.

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