JP2016088297A - Electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve suppression of a radio noise with a simple configuration.SOLUTION: A electric vehicle, in which drive force output from a motor is transmitted to a left rear wheel 12 via a transmission 17 to drive the vehicle, includes: a transmission bearing 21 disposed inside the transmission 17; a knuckle for pivotally supporting a drive shaft 18 freely rotationally, the shaft connected to an output shaft of the motor; and a hub bearing 72 for bearing the knuckle. Further, an absolute value of impedance of the hub bearing 72 is set smaller than an absolute value of impedance of the transmission bearing 21, and a grounding harness 64 is disposed for electrically connecting the knuckle to the GND (a vehicular body).SELECTED DRAWING: Figure 5

Description

  The present invention relates to an electric vehicle driven by a driving force output from, for example, a driving motor.

  Due to the electrification of automobiles in recent years, electric vehicles (for example, hybrid cars and electric cars) using a motor as a rotational drive source are increasing. When a motor is used as a rotational drive source, noise is generated in the rotor that constitutes the motor, and this noise is transmitted to the knuckle through the drive shaft, and may be emitted from the knuckle to the outside to become radio noise. . For example, a radio antenna mounted on a vehicle picks up noise and generates radio noise.

  Therefore, in Patent Document 1, as a countermeasure against such radio noise, a carrier that is rotatably provided relative to the axle and a parking brake wire are electrically connected and grounded, whereby radio noise is caused to the vehicle body side. The escape is suppressed from radiating to the outside.

JP 2009-29326 A

  By the way, in the connection part of the arm member (upper arm, lower arm) and the knuckle constituting the suspension mechanism, and in the connection part of the arm member (upper arm, lower arm) and the vehicle body, mounts such as rubber bushes are provided to absorb vibration. A member may be mounted.

  This mount member has a high resistance value, for example, several k (Ω) electrically compared to other body parts. For this reason, the axial current that flows through the drive shaft that is rotatably supported by the knuckle is less likely to flow to the vehicle body side due to the relatively high resistance value of the mount member, and also to the wheel side. The shaft current that flows to the wheel side is radiated as electromagnetic waves to the outside of the vehicle, and radio antennas may receive the electromagnetic waves and generate radio noise (radiation noise).

  The present invention has been made in view of the above points, and an object thereof is to provide an electric vehicle capable of further suppressing radio noise with a simple structure.

  In order to achieve the above object, the present invention provides an electric vehicle in which a driving force output from a drive motor is transmitted to a wheel via a transmission to drive the vehicle, and is disposed on an output shaft of the drive motor, or A first bearing disposed inside the transmission, a knuckle for rotatably supporting a drive shaft connected to an output shaft of the drive motor, and a second bearing for supporting the knuckle, The absolute value of the impedance of the second bearing is set smaller than the absolute value of the impedance of the first bearing, and a conductor harness that electrically connects the knuckle and the vehicle body is provided.

  According to the present invention, when an axial voltage is generated on the motor shaft of the drive motor or the drive shaft connected to the motor shaft, the axial current caused by the axial voltage is transmitted from the wheel side via the second shaft and the conductor harness. Also flows easily to the GND (vehicle body). For this reason, the axial current which flows into the wheel side can be reduced, and generation | occurrence | production of the radio noise (radiation noise) to the vehicle exterior can be suppressed.

  Moreover, according to this invention, radio noise can be suppressed with the simple structure of connecting a knuckle and a vehicle body with a conductor harness.

  According to the present invention, a mount member is disposed between the knuckle and the vehicle body, and the conductor harness is electrically connected between the knuckle and the vehicle body by bypassing the mount member in an equivalent circuit diagram. It is characterized by connecting to.

  According to the present invention, since the conductor harness bypasses the mount member and electrically connects the knuckle and the vehicle body, it bypasses the mount member where the axial current hardly flows and bypasses the mount current to the GND (vehicle body). Can flow reliably.

  In the present invention, it is possible to obtain an electric vehicle capable of further suppressing radio noise with a simple structure.

It is a schematic structure section of a wheel suspension system arranged in an electric vehicle concerning an embodiment of the present invention. It is a perspective view of the wheel suspension system shown in FIG. FIG. 3 is a partially enlarged perspective view of FIG. 2. It is a disassembled perspective view which shows the state by which the terminal of a grounding member is fastened with a volt | bolt with respect to the ground connection part toward the vehicle rear of a knuckle. It is the equivalent circuit schematic which simplified the vehicle suspension system containing a transmission. It is a partial expanded sectional view which shows the state which a ball rolls along the ball | bowl track surface of a bearing. It is a perspective view which shows the state by which the earth | ground member was fastened with the volt | bolt with respect to the earth connection part toward the vehicle front of the knuckle. In this embodiment, it is explanatory drawing which shows the relationship between the radio noise electric field strength and the resistance value of a grounding harness.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. 1 is a schematic sectional view of a wheel suspension system arranged in an electric vehicle according to an embodiment of the present invention, FIG. 2 is a perspective view of the vehicle suspension system shown in FIG. 1, and FIG. 3 is a partially enlarged view of FIG. It is a perspective view.

  As shown in FIG. 1, the wheel suspension system 10 includes a suspension mechanism 14 that is connected to a subframe of a vehicle (not shown) and supports a left rear wheel (wheel) 12, and a brake mechanism 16 that brakes the left rear wheel 12 ( 2) and a hub mechanism 19 that transmits the rotational driving force of the drive shaft 18 to the left rear wheel 12 via a transmission (transmission) 17.

  A transmission bearing (first bearing) 21 that rotatably supports the shaft is disposed in the transmission 19. The mission bearing 21 is filled with a lubricant (for example, lubricating oil). The plurality of balls disposed in the mission bearing 21 so as to be freely rollable are oil-lubricated with lubricating oil. In the present embodiment, the mission bearing 21 is the first bearing. However, for example, a motor shaft bearing (not shown) that rotatably supports the output shaft of the motor M described later may be used as the first bearing.

  The left rear wheel 12 includes a spoke portion 12a, an annular rim portion 12b fixed to the outer periphery of the spoke portion 12a, and a tire 12c attached to the rim portion 12b. In this case, the spoke part and the rim part form a wheel as a conductor.

  The suspension mechanism 14 rotatably supports a drive shaft 18 connected to an output shaft of a motor (drive motor) M, supports the knuckle 20 formed of a conductive material, the knuckle 20, and the knuckle 20 And a plurality of arms suspended on a subframe (not shown). In addition, the motor M is comprised by the three-phase alternating current motor, for example.

  FIG. 4 is an exploded perspective view showing a state in which the terminal of the ground member is fastened by a bolt with respect to the ground connection portion facing the vehicle rear of the knuckle.

  As shown in FIG. 4, the knuckle 20 includes a knuckle body 20 a, a projecting portion 22 that projects substantially horizontally from the upper part of the knuckle body 20 a toward a subframe (not shown) (inside the vehicle body), and a knuckle body 20 a. Two ring portions 26 a and 26 b that are integrally provided on the lower side and have a through hole 24 are provided. A through hole 28 for mounting a hub bearing to be described later is formed at the approximate center of the knuckle body 20a.

  The protrusion 22 is formed with a connection hole 32 to which an upper arm 30 (see FIG. 1) is connected via a substantially cylindrical rubber bush (mount member) 29. Further, the projecting portion 22 is provided with a ground connection portion 34 formed by a substantially rectangular flat surface facing the rear of the vehicle. By screwing a bolt 38 into the screw hole 36 of the ground connection portion 34, a terminal 40a of the ground member 40 described later is fastened. Thereby, the ground member 40 is electrically connected to the knuckle 20.

  As shown in FIG. 2, the plurality of arms are substantially A-shaped in plan view, and one end on the outer side of the vehicle body is connected to the protruding portion 22 (see FIG. 3) of the knuckle 20 and the other end on the inner side of the vehicle body is not illustrated. An upper arm 30 connected to the frame, a first lower arm 42a and a second lower arm whose one end on the outside of the vehicle body is connected to the two ring portions 26a and 26b of the knuckle 20 and the other end on the inside of the vehicle body is connected to a subframe (not shown). 42b and a control arm 43 connected to an intermediate portion of the knuckle 20. As shown in FIG. 1, a rubber bush is interposed in each connection portion.

  A suspension portion 44 is provided between one end and the other end of the upper arm 30 to suspend two arm portions 30a and 30b branched from one end. The suspension portion 44 is connected to a damper 46 and a bolt 46 via bolts (not shown). A coil spring 48 is connected.

  The brake mechanism 16 includes a disc-shaped brake disc 50 and a brake caliper 52. The brake caliper 52 has a housing 54, and a brake pad (not shown) and a plurality of pistons (not shown) that press the brake pad toward the brake disc 50 are disposed inside the housing 54.

  The brake caliper 52 is disposed close to and opposed to the ground connection portion 34 of the knuckle 20 in the vehicle longitudinal direction. In other words, the ground connection portion 34 is disposed between the knuckle 20 and the brake caliper 52. A wheel speed sensor (ABS sensor) 58 that detects the rotational speed of the left rear wheel 12 is attached to the disk cover 56 that covers the brake disk 50.

  As shown in FIG. 2, the ground member 40 has a single grounding harness 64 connected to the ground connection portion 34. Further, a tube member 66 that integrally covers an ABS harness and an EPB harness (not shown) is provided.

  The grounding harness 64 is attached to the outer peripheral surface of the tube member 66 via a winding means (not shown), extends along the tube member 66, and branches from a branching portion 68 located above the knuckle 20. It is configured. The grounding harness 64 is grounded to a conductive vehicle body (for example, a subframe (not shown)) via a terminal (not shown).

  Returning to FIG. 1, the hub mechanism 19 includes a hub body 70 and a hub bearing 72 (second bearing) that rotatably supports the hub body 70.

  The hub main body 70 includes a stepped cylindrical portion 74 to which the hub bearing 72 is fitted, and a disc portion 78 to which the left rear wheel 12 is fixed by a plurality of hub bolts 76. The stepped cylindrical portion 74 is provided with a spline fitting portion 80 including a through hole penetrating along the axial direction. The spline fitting portion 80 is spline fitted to a shaft portion 82a of a joint (for example, a Barfield type constant velocity joint) 82 connected to the tip end portion of the drive shaft 18, whereby the drive shaft 18 and the joint 82, the hub main body 70, and the left rear wheel 12 rotate integrally.

  The hub bearing 72 is mounted between the through hole 28 of the knuckle 20 and the stepped cylindrical portion 74, and includes an outer diameter outer retainer 84, an inner diameter inner retainer 86, and a plurality of balls 88. The plurality of balls 88 are provided so as to roll along a ball raceway surface formed between the outer retainer 84 and the inner retainer 86. As shown in FIG. 6 to be described later, a predetermined separation distance d is formed between the ball 88 and the ball raceway surface.

  Further, a lubricant (for example, grease) is filled between the outer retainer 84 and the inner retainer 86. The ball 88 is grease-lubricated with a lubricant. The hub bearing 72 is attached to the through hole 28 of the knuckle 20 with a predetermined allowance.

  The wheel suspension system 10 arranged in the electric vehicle according to the present embodiment is basically configured as described above, and the function and effect thereof will be described next.

  FIG. 5 is a simplified equivalent circuit diagram of a vehicle suspension system including a transmission, and FIG. 6 is a partially enlarged cross-sectional view showing a state where a ball rolls along a ball raceway surface of a bearing.

  In this equivalent circuit diagram, the mission bearing 21 is composed of a first RC parallel circuit 90 in which a first resistor R1 and a first capacitor C1 are connected in parallel, and the hub bearing 72 is composed of a second resistor R2 and a second capacitor C2. Are configured by a second RC parallel circuit 92 connected in parallel.

In this case, the absolute value (| Z2 |) of the impedance of the hub bearing 72 functioning as the second bearing is set smaller than the absolute value (| Z1 |) of the impedance of the mission bearing 21 functioning as the first bearing. (| Z1 |> | Z2 |).
However, | Z | = √ (R ² + X ² ). R is the real part of the impedance, and X is the imaginary part of the impedance.
Since the transmission bearing 21 and the hub bearing 72 have the same frequency (ω), the absolute values of the impedances can be compared.

  In the equivalent circuit diagram, the resistor R3 is a plurality of parallel rubber bushes (mounting members) connected to the arm members of the suspension mechanism (upper arm 30, first lower arm 42a, second lower arm 42b, control arm 43, etc.). 29 composite values are shown. The resistor R3 is connected in series with the second RC parallel circuit 92 on the ground side of the second RC parallel circuit 92, which is the hub bearing 72.

  Further, in the equivalent circuit diagram, the resistor R4 indicates the ground member 40 connected to the ground connection portion 34 that is the side surface of the knuckle 20. The resistor R4 bypasses the resistor R3 of the rubber bush 29 and is connected in series between the second RC parallel circuit 92 and GND (vehicle body).

  Furthermore, the electromagnetic wave radiated outward from the left rear wheel 12 as a conductor is received by the antenna of the in-vehicle radio, but it is considered that a large resistance (deemed resistance) exists when the electromagnetic wave propagates in the air. It is. The radio noise is composed of a sine wave component and a high frequency component, as schematically shown in the equivalent circuit diagram.

Here, the capacitors C1 and C2 constituting the first RC parallel circuit 90 and the second RC parallel circuit 92 are respectively expressed by the following equations.
C = εS / d (formula)
Where ε; dielectric constant S; opposing area between the ball and the ball raceway surface d; spacing distance between the ball and the ball raceway surface Also, the resistors R1 and R2 constituting the first RC parallel circuit 90 and the second RC parallel circuit 92 Is represented as the resistance of the lubricant flowing through the clearance between the ball 88 and the ball raceway surface.

Because of the difference in the dielectric constant ε in the above formula and the distance d between the ball 88 and the ball raceway surface of the hub bearing 72 set narrower than that of the mission bearing 21, the capacitor of the hub bearing 72 C2 is larger than the capacitor C1 of the mission bearing 21.
As a result, the AC impedance (1 / jωC2) of the hub bearing 72 is smaller than the AC impedance (1 / jωC1) of the mission bearing 21.

  In the present embodiment, when the shaft voltage V is generated in the drive shaft 18 connected to the motor shaft of the drive motor M, the shaft current i resulting from the shaft voltage V is passed through the hub bearing 72 and the grounding harness 64. It becomes easier to flow toward the GND (vehicle body) side than the left rear wheel side (wheel side) 12.

  That is, the resistance R3 of the rubber bush 29 has a high resistance value of, for example, several k (Ω) compared to other body parts, so that the axial current i flowing through the drive shaft 18 is originally Since the resistance R3 of the rubber bush 29 is relatively high, it is difficult for the rubber bush 29 to flow toward the GND (vehicle body) side.

  In contrast, in the present embodiment, the axial current I flowing through the drive shaft 18 flows to the GND (vehicle body) side via the grounding harness 64 connected in series to the second RC parallel circuit 92 of the hub bearing 72. become. For this reason, the axial current i flowing to the left rear wheel side (wheel side) 12 can be reduced, and generation of radio noise (radiation noise) to the outside of the vehicle can be suppressed.

  In the present embodiment, radio noise can be suppressed by a simple structure in which the knuckle 20 and GND (vehicle body) are connected by the grounding harness 64.

  Furthermore, in this embodiment, the grounding harness 64 bypasses the resistor R3, which is a composite value of the rubber bush 29, and electrically connects the knuckle 20 and GND (vehicle body), so that the axial current i It is possible to bypass the resistor R3 of the rubber bush 29, which is difficult to flow, and to reliably flow the axial current I to the GND (vehicle body). In other words, the resistance R4 of the grounding harness 64 is connected in parallel with the resistance R3, which is a composite value of the rubber bush 29, and thereby along the resistance R4 of the grounding harness 64 having a resistance value smaller than that of the resistance R3. An axial current I can flow through the GND (vehicle body).

  Furthermore, in the present embodiment, the ground connection portion 34 to which the ground member 40 is connected is provided between the brake caliper 52 and the knuckle 20 of the brake mechanism 16 along the vehicle front-rear direction. As a result, even if snow adheres to the knuckle 20, the attached snow can be removed and removed by the heat generation action of the brake caliper 52 located near the ground connection portion 34 of the knuckle 20. . As a result, in this embodiment, it is possible to prevent the ground harness 64 from being damaged due to the influence of snow.

  Next, the case where the ground member 40 is connected to the ground connection portion 34 which is a side surface of the knuckle 20 facing the front of the vehicle, as opposed to FIG.

  FIG. 7 is a perspective view showing a state in which the ground member is fastened by a bolt to the ground connection portion of the knuckle facing the front of the vehicle. Components that are the same as or correspond to those shown in FIG. 4 are given the same reference numerals, and descriptions thereof are omitted.

  As shown in FIG. 7, when the ground member 40 is connected to the ground connection portion 34 that is the side facing the front of the vehicle of the knuckle 20 that constitutes the rear suspension, the brake caliper located in front of the vehicle relative to the knuckle 20. 52 functions as a protective wall for the knuckle 20. Thereby, the earth connection part 34 (earth grounding surface) can be protected from chipping (chipping) by, for example, flying stones of the front wheels.

  In this embodiment, the knuckle 20 attached to the rear wheel is described. However, the present invention is not limited to this, and the ground connection portion 34 is connected to the knuckle 20 attached to the front wheel (not shown). Can be provided. In this case, the ground member 40 is connected to the ground connection portion 34 that is a side surface of the knuckle 20 attached to the front wheel (not shown) facing the rear of the vehicle or the ground connection portion 34 that is the side surface of the knuckle 20 facing the front of the vehicle. Grounded.

  Next, the setting of the resistance value of the grounding harness 64 connected to the ground connection 34 will be considered. FIG. 8 is an explanatory diagram showing the relationship between the radio noise electric field strength and the resistance value of the grounding harness in this embodiment.

  As can be understood from the characteristic curve shown in FIG. 8, the electric field strength of the radio noise is a region where the resistance value R of the grounding harness 64 decreases at about 10Ω as a boundary and is kept at a substantially constant value at the lower limit ( Halftone dot reference). That is, by setting the upper limit of the resistance value R of the grounding harness 64 corresponding to the electric field intensity of radio noise to be greater than 0Ω and 10Ω or less (0 <R ≦ 10), radio noise can be reduced and grounding can be performed. As the harness 64, an inexpensive harness having a resistance value near 10Ω currently available on the market can be used. Thereby, there exists an advantage which can manufacture the wheel suspension system 10 still more cheaply.

10 Vehicle suspension system 12 Left rear wheel (wheel)
17 Transmission 18 Drive shaft 20 Knuckle 21 Mission bearing (first bearing)
29 Rubber bushing (mounting member)
64 Harness for grounding (conductor harness)
72 Hub bearing (second bearing)
M motor (drive motor)
i, I axis current

Claims (2)

In the electric vehicle in which the driving force output from the drive motor is transmitted to the wheel via the transmission to drive the vehicle,
A first bearing disposed on the output shaft of the drive motor or disposed inside the transmission;
A knuckle that rotatably supports a drive shaft connected to the output shaft of the drive motor;
A second bearing for supporting the knuckle;
With
The absolute value of the impedance of the second bearing is set smaller than the absolute value of the impedance of the first bearing;
An electric vehicle comprising a conductor harness that electrically connects the knuckle and the vehicle body. The electric vehicle according to claim 1,
A mount member is disposed between the knuckle and the vehicle body,
In the equivalent circuit diagram, the conductor harness bypasses the mount member and electrically connects the knuckle and the vehicle body.

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