JP2009096213A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the mountability of an electric power steering device being mounted on a vehicle by reducing the restriction of the mounting space of an auxiliary power supply having a plurality of electric double-layer capacitor cells. <P>SOLUTION: The electric power steering device 10 comprises an electric motor 31, the auxiliary power supply 40 capable of distributing electric power to the electric motor 31, a steering shaft 13 to be rotated by the operation of a steering member 11, and a deceleration mechanism 30 for transmitting the power of the electric motor 31 to the steering shaft 13. The auxiliary power supply 40 has a plurality of electric double-layer capacitor cells 50 connected in series. The plurality of cells 50 are disposed around the steering shaft 13 on a housing 43 of the deceleration mechanism 30. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric power steering device mounted on a vehicle such as an automobile.

In the electric power steering apparatus, as the required steering assist force is larger, it is necessary to flow a larger current to the motor. Therefore, power is usually supplied to the motor from the in-vehicle battery, which is the main power source. However, when the required steering assist force is large, such as during stationary operation or sudden steering, the auxiliary power source that has previously stored power is used. Has also been proposed for supplying electric power to make up for the shortage of electric power in the on-vehicle battery (see, for example, Patent Document 1). In Patent Document 1, for example, an electric double layer capacitor (capacitor) is used as an auxiliary power source.
JP 2003-320942 A

Since the electric double layer capacitor as described above has a low rated voltage of about 2.0 to 3.0 V, when used as an auxiliary to an in-vehicle battery, a plurality of electric double layer capacitors are connected in series. It is necessary to increase the rated voltage. In this case, it is conceivable that a plurality of cells are stored in a single case in a state where they are aligned vertically and horizontally, and this case is mounted on a vehicle.
On the other hand, since the electric double layer capacitor has an operation guarantee temperature on the high temperature side of about 60 ° C. to 80 ° C., it is difficult to arrange the electric double layer capacitor in the engine room where the temperature is higher. Therefore, it can be considered that the engine room is arranged in a compartment. However, since various instruments, electrical components, electrical wiring, etc. are arranged around the vehicle interior, especially around the steering wheel of the dashboard, there is a space for arranging a case in which a plurality of cells are stored together as described above. It is difficult to secure.

  In view of such circumstances, the present invention provides an electric power steering apparatus that can reduce the restriction on the arrangement space of an auxiliary power source provided with a plurality of electric double layer capacitor cells and can be mounted on a vehicle. For the purpose.

  The present invention provides an electric power steering apparatus that transmits power of an electric motor to a steering force transmission shaft that moves by operation of a steering member. The electric power steering apparatus includes an auxiliary power source capable of supplying electric power to the electric motor. It is configured by connecting cells of an electric double layer capacitor in series, and the plurality of cells are arranged in accordance with the shape of the constituent member of the electric power steering apparatus.

According to this configuration, since the cells of the plurality of electric double layer capacitors constituting the auxiliary power supply are arranged according to the shape of the constituent members of the electric power steering device, the plurality of cells are arranged in one place. Compared to the case, the arrangement space can be reduced. Therefore, for example, each cell can be arranged in a narrow space such as a dashboard in the vehicle interior.
Examples of the constituent members of the electric power steering apparatus include an electric power steering such as a steering force transmission shaft, a shaft support that supports the steering force transmission shaft, and a transmission mechanism that transmits the power of the electric motor to the steering force transmission shaft. Mention may be made of members that form the main mechanical structure of the device, and cells may be arranged in accordance with one or more of these shapes.

As described above, when a plurality of cells are arranged in accordance with the shape of the constituent members of the electric power steering apparatus, the distance between the cells may not be kept uniform. If the distance between the cells becomes non-uniform, the voltage of each cell tends to vary, leading to a decrease in the performance of the auxiliary power supply. For this reason, it is recommended to maintain an appropriate voltage balance between the cells and maintain the performance by providing an equalizing means for equalizing the voltages of the plurality of cells.
As the equalizing means, for example, the diameter and width of conductive members such as conductive wires and bus bars connecting the cells differ depending on the distance between the cells, and the balance of resistance of the conductive members is adjusted. It is possible to adopt a configuration to

  The plurality of cells are preferably arranged around the steering force transmission axis. In this case, the whole of the plurality of cells does not greatly protrude radially outward from one place around the steering force transmission shaft, and the amount of protrusion of each cell radially outward can be reduced. . As a result, it is not necessary to secure a large space for arranging a plurality of cells, and restrictions on the arrangement space can be further reduced.

  When the transmission mechanism includes a gear attached to the steering shaft and a housing that covers the gear, the plurality of cells can be provided on the axial end surface of the housing. In this case, since the gear and the housing have a dimension that protrudes radially outward by themselves, a plurality of cells are provided on an end face in the axial direction of the housing so that the radial protrusion by the cell itself can be prevented. Can be eliminated.

  ADVANTAGE OF THE INVENTION According to this invention, the restrictions of the arrangement space of the auxiliary power supply provided with the cell of the some electric double layer capacitor can be decreased, and the mounting property to a vehicle can be improved.

  FIG. 1 is a schematic diagram of an electric power steering apparatus 10 according to a first embodiment of the present invention. The apparatus 10 is mounted on, for example, an automobile and a steering operation of a driver applied to a steering wheel (steering member) 11 is illustrated. Accordingly, a steering shaft 13 for changing the direction of the tire (steering wheel) 12 is provided. The steering shaft 13 is rotatably supported by a steering column 42, and a first shaft portion 14 having a steering wheel 11 attached to an upper end portion thereof, and a first torsion bar 15 connected to the first shaft portion 14. It has the 2nd axial part 16 connected, and rotation of the steering wheel 11 is transmitted directly.

  A steering gear 20 is connected to the lower end of the second shaft portion 16 via universal joints 17 and 18 and an intermediate shaft 19. The steering gear 20 is of a rack and pinion type including a pinion shaft 21 and a rack shaft 22, and the pinion shaft 21 is connected to the universal joint 18 at the upper end and includes pinion teeth 21a at the lower portion. The rack shaft 22 includes rack teeth 22a that mesh with the pinion teeth 21a.

  The rack shaft 22 is supported in the rack shaft housing 23 so as to be movable in the axial direction (left and right direction). The tire 12 is connected to both ends of the rack shaft 22 in the axial direction via tie rods 24 and knuckle arms 25. ing. The pinion shaft 21 is supported by a pinion shaft housing 26 that is continuous with the rack shaft housing 23 so as to be rotatable about its axis.

In the above-described configuration, when the steering wheel 11 is rotated for steering, the pinion shaft 21 connected via the steering shaft 13, the intermediate shaft 19 and the like rotates, and this rotation is caused by the pinion teeth 21a and the rack teeth 22a. Is converted into the movement of the rack shaft 22 in the axial direction. The movement of the rack shaft 22 is transmitted to the left and right knuckle arms 25 via the tie rods 24, and the left and right tires 12 are steered in the operation direction of the steering wheel 11 by pushing and pulling these knuckle arms 25. .
Here, the shafts 13, 19, 21, and 22 between the steering wheel 11 and the tire 12 constitute a steering force transmission shaft that transmits a steering force.

  An electric motor 31 to which electric power is supplied from a power supply unit 37 is connected to the steering shaft 13 via a speed reduction mechanism (transmission mechanism) 30. The speed reduction mechanism 30 includes a worm (drive gear) 32 that is coupled to the output shaft of the electric motor 31 so as to be integrally rotatable, a worm wheel (driven gear) 33 that meshes with the worm 32, and a housing 43 that covers them. The worm wheel 33 is coupled to the second shaft portion 16 so as to be integrally rotatable. Therefore, the rotational power of the electric motor 31 is transmitted to the steering shaft 13 while being decelerated by the speed reduction mechanism 30.

  The power steering apparatus 10 according to the present embodiment includes a steering shaft 13, a steering column 42, a speed reduction mechanism 30, an electric motor 31, and a power supply unit 37, and steering that applies a steering assist force to the steering shaft 13. It is an axis assist (column assist) type electric power steering device (C-EPS). In the column assist type electric power steering apparatus 10, the main mechanical structure (main structure portion) is configured by the steering shaft 13, the steering column 42, and the speed reduction mechanism 30.

  The electric motor 31 includes a detection result of a torque sensor 35 that detects a steering torque based on a relative rotational displacement amount between the first shaft portion 14 and the second shaft portion 16, a vehicle speed, a steering angle of the steering wheel 11, and the like. Drive control is performed by an ECU (electronic control unit) 36 so as to generate an appropriate steering assist force based on the detection result. Specifically, the detection result of the torque sensor 35 or the like is input to the ECU 36, and the ECU 36 obtains the target power corresponding to the steering assist force required from the detection result, and the target power is electrically driven from the power supply unit 37. Supply to the motor 31.

The power supply unit 37 includes an in-vehicle battery (main power supply) 38 and an auxiliary power supply 40. The auxiliary power supply 40 is composed of an electric double layer capacitor, and is charged / discharged by a charge / discharge circuit 39 provided in the ECU 36.
This auxiliary power supply 40 is used when a large steering assist force is required, such as when entering a garage or parking. Specifically, when the required steering assist force is large and the load on the in-vehicle battery 38 becomes large, the ECU 36 switches the auxiliary power source 40 to a discharging state by the charge / discharge circuit, and in addition to the in-vehicle battery 38, the auxiliary power source 40 electric power is supplied to the electric motor 31. Thereby, sufficient electric power can be supplied to the electric motor 31, and stable steering assistance can be performed.

  Further, when the required steering assist force is relatively small and only the electric power of the in-vehicle battery 38 is sufficient, the auxiliary power source 40 is not used, and the ECU 36 switches the auxiliary power source 40 to the charged state by the charge / discharge circuit, The electric power of the in-vehicle battery 38 is supplied to the electric motor 31.

  FIG. 2 is a perspective view of the electric power steering apparatus, and FIG. 3 is a bottom view of the electric power steering apparatus (viewed in the direction of arrow III in FIG. 2). The steering shaft 13 of the electric power steering apparatus 10 is rotatably supported by a steering column (shaft support) 42 via a bearing. Below the steering column 42, a worm 32 and a worm of a speed reduction mechanism 30 are provided. A housing 43 that accommodates the wheel 33 is connected.

  The housing 43 includes a disk-shaped first portion 43A that covers the worm wheel 33, and a second portion 43B that is integrally formed with a part of the first portion 43A in the circumferential direction and covers the worm 32. An attachment portion 43C for attaching the electric motor 31 is formed in the second portion 43B.

  The auxiliary power supply 40 is configured by connecting a plurality of electric double layer capacitor cells 50 in series. Each cell 50 is arranged in a state matching the shape of the constituent member (main structure portion) of the electric power steering apparatus 10 as described above. Specifically, each cell 50 is arranged in the circumferential direction so as to surround the periphery of the steering shaft 13 on one axial end surface (lower end surface) of the first portion 43 </ b> A of the housing 43. A plurality of storage portions 51 are integrally formed in a protruding shape on the lower end surface of the first portion 43 </ b> A of the housing 43, and each cell 50 is stored in each storage portion 51.

  The cell 50 of the present embodiment is a cylindrical type, and the shape of the storage portion 51 is also formed in a cylindrical shape according to the shape of the cell 50. The cells 50 housed in the housing parts 51 are connected to each other via a conductive member 52 such as a conductive wire or a bus bar in the housing 43.

  A support bracket 44 for supporting the steering column 42 so as to be tiltable is integrally formed on the lower end surface of the first portion 43A. The storage 51 is formed so as to avoid the support bracket 44 and the second portion 43 </ b> B of the housing 43. In the illustrated example, the four storage units 51 are arranged in a close state, and one other storage unit 41 is arranged apart from the storage units 51. For this reason, the distance between each cell 50 accommodated in each accommodating part 51 does not become uniform, and the length of the electrically-conductive member 52 which connects the cell 50 accommodated in each accommodating part 51 also differs.

In such a case, if each cell 50 is connected using the conductive member 52 having the same diameter and width, the resistance of the conductive member 52 varies depending on the distance between the cells 50, and the voltage of each cell 50 is different. Variations are likely to occur. Such a variation in the voltage of each cell 50 leads to a decrease in the performance of the auxiliary power supply 40.
Therefore, in the present embodiment, the dimensions such as the diameter, width, and length of the conductive member 52 are changed according to the distance between the cells 50 so that the voltage balance of the cells 50 can be suitably achieved. By making the resistances between the cells 50 uniform, variations in the voltages of the cells 50 are prevented. That is, equalization means for equalizing the voltages of the cells 50 by adjusting the dimensions of the conductive member 52 is configured.

  In the above embodiment, since the plurality of electric double layer capacitor cells 50 constituting the auxiliary power supply 40 are arranged according to the shape of the constituent members of the electric power steering apparatus 10, for example, the plurality of cells 50 are The arrangement space of the plurality of cells 50 can be reduced as compared with the case where the cells are arranged in one place in the vertical and horizontal directions or arranged in a straight line. Therefore, even within the dashboard to which this column assist type electric power steering device 10 is mounted, the auxiliary power supply 40 can be arranged without securing a wide arrangement space.

Further, each cell 50 of the auxiliary power supply 40 is disposed on the end face in the axial direction of the housing 43 of the worm wheel 33, and therefore does not protrude outward in the radial direction from the housing 43. Therefore, a plurality of cells 50 can generally be arranged as long as the housing 43 can be arranged.
Since the storage portion 51 of the cell 50 is formed integrally with the housing 43 of the speed reduction mechanism 30, the number of parts can be reduced as compared with the case where the separate storage portion 51 is formed. 40 can be assembled easily.

  FIG. 4 is an explanatory front view of the electric power steering apparatus 10 showing the second embodiment of the present invention. In the present embodiment, a plurality of cells 50 are provided on the other axial end surface (upper end surface) of the first portion 43 </ b> A of the housing 43 of the speed reduction mechanism 30. Since other configurations are the same as those of the first embodiment, detailed description thereof is omitted.

  The present invention is not limited to the above-described embodiment, and can be appropriately modified. For example, the plurality of cells 50 can be arranged on the outer peripheral surface of the steering column 42, or can be arranged on the end surface or outer peripheral surface of the housing 34 (see FIG. 1) of the torque sensor 35. Also in this case, a plurality of cells 50 can be arranged around the steering shaft 13 as in the first and second embodiments. Further, the number of cells 50 is not limited to the above-described embodiment.

  Further, the equalizing means for equalizing the voltage of each cell 50 is not limited to the configuration by adjusting the size of the conductive member 52 as described above, but a configuration for equalizing the voltage of the cell 50 by an electric circuit, A conventionally known configuration in which a monitor circuit for monitoring the charge / discharge state of each cell 50 is provided, and the voltage is kept uniform by controlling the charge / discharge current for each cell 50 while monitoring the charge / discharge state of each cell 50 Can also be adopted.

  The shape of the cell 50 of the electric double layer capacitor is not limited to the cylindrical type, but may be a coin (disk) type or a square type. In the embodiment described above, the electric double layer capacitor cell 50 is accommodated in the accommodating portion 51 formed integrally with the housing 43 of the speed reduction mechanism 30, but the cells 50 are accommodated separately from the housing 43 of the speed reduction mechanism 30. A case including the portion 51 may be formed, and this case may be attached to the constituent members of the electric power steering apparatus 10 such as the housing 43 and the steering column 42.

  Further, the present invention is not limited to the column assist type electric power steering device but can be applied to other types of electric power steering devices such as a pinion assist type and a rack assist type. For example, in the case of a pinion assist type electric power steering device provided with a speed reduction mechanism and an electric motor with respect to the pinion shaft 21 of the steering gear 20, the electric power steering device 50 includes an electric double layer capacitor cell 50 constituting the auxiliary power source 40. They can be arranged in accordance with the shape of the speed reduction mechanism, pinion shaft housing 26, etc., which are constituent members of the apparatus. However, in this case, since the auxiliary power source 40 is disposed in the engine room, in consideration of the guaranteed operating temperature of the electric double layer capacitor, a column assist type in which the auxiliary power source 40 can be disposed in the vehicle interior. It is more preferable to apply the present invention to an electric power steering device.

1 is a schematic diagram of an electric power steering apparatus according to a first embodiment of the present invention. It is a perspective view of the same electric power steering device. It is a bottom view of the same electric power steering device. It is front explanatory drawing of the electric power steering apparatus which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

10 Electric power steering device 13 Steering shaft (steering force transmission shaft)
30 Deceleration mechanism (transmission mechanism)
31 Electric motor 32 Worm 33 Worm wheel 40 Auxiliary power supply 50 cell

Claims (4)

In the electric power steering device that transmits the power of the electric motor to the steering force transmission shaft that moves by the operation of the steering member,
An auxiliary power source capable of supplying electric power to the electric motor is provided, and the auxiliary power source is configured by connecting a plurality of electric double layer capacitor cells in series, and the plurality of cells are constituent members of the electric power steering apparatus. An electric power steering device, which is arranged in accordance with the shape of the electric power steering device.   The electric power steering apparatus according to claim 1, further comprising an equalizing unit that equalizes voltages of the plurality of cells.   The electric power steering apparatus according to claim 1, wherein the plurality of cells are arranged around the steering force transmission axis. A transmission mechanism for transmitting the power of the electric motor to the steering force transmission shaft;
The transmission mechanism includes a gear attached to the steering force transmission shaft, and a housing that covers the gear.
The electric power steering apparatus according to any one of claims 1 to 3, wherein the plurality of cells are arranged on an end face in an axial direction of the housing.

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