JP4175363B2 - Power steering device - Google Patents

Description

  The present invention relates to a power steering device that assists in steering a vehicle.

Conventionally, when it is determined that the vehicle has collided based on the detection signal from the airbag collision detector, the motor for the electric power steering (EPS) is stopped so that the overcurrent to the motor drive circuit is reduced. An electric power steering device that has been prevented is known (see, for example, Patent Document 1).
JP 2000-72007 A

  In the above-described conventional electric power steering apparatus, the collision with the vehicle is determined based on the detection signal from the collision detector for the airbag. For this reason, although the collision of the object with the vehicle is detected, there is a possibility that the impact on the EPS mechanism itself cannot be detected accurately.

  The present invention has been made to solve such problems, and has as its main object to detect the impact on the EPS mechanism with higher accuracy.

In order to achieve the above object, one embodiment of the present invention provides:
A power steering device that is disposed at a front portion of a vehicle and applies steering assist torque for assisting steering to a rack shaft,
The power steering apparatus includes a collision detection unit that detects a collision of an object with a rack housing that houses the rack shaft.

  According to this aspect, the collision detection means for detecting the collision of an object such as a vehicle member with the rack housing that houses the rack shaft is provided. Thereby, the impact on the EPS mechanism in the rack housing can be detected with higher accuracy.

  In this aspect, the collision detection means may detect a collision load on the fastening portion of the rack housing.

  In this aspect, the collision detection means may detect deformation of the stress concentration portion of the rack housing.

  In this aspect, the collision detection means may detect relative movement of the rack housing with respect to the vehicle body.

  In this aspect, the control mode of the steering assist torque applied to the rack shaft may be changed when the collision detection unit detects a collision of an object with the rack housing. For example, when the collision detection unit detects a collision of an object with the rack housing, the application of the steering assist torque to the rack shaft may be limited or stopped.

  According to the present invention, the impact on the EPS mechanism can be detected with higher accuracy.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the accompanying drawings. Note that the basic concept, main hardware configuration, operating principle, basic control method, and the like of the electric power steering apparatus are known to those skilled in the art, and thus detailed description thereof is omitted.

  FIG. 1 is a schematic diagram of a power steering apparatus according to an embodiment of the present invention. The power steering device 1 according to the present embodiment is roughly constituted by a rack housing 2, a rack shaft 3, an electric motor 4, a motor shaft 5, a ball screw device 6, and the like. The rack housing 2 includes a hollow cylindrical first rack housing 2a and second rack housing 2b, and a yoke housing 2c provided between the rack housings 2a and 2b. The housings 2a, 2b and 2c are bolts or the like. Are coaxially fastened.

  A rack shaft 3 is penetrated through the rack housing 2 so as to be movable in the axial direction (directions indicated by arrows X1 and X2 in the figure), and both ends of the rack shaft 3 protruding from the first and second rack housings 2a and 2b are The tie rods 7 and 8 are connected to the left and right front wheels. Between the end portions of the first and second rack housings 2a and 2b and the tie rods 7 and 8, boots 9 and 10 that can be expanded and contracted are mounted. Shielded.

  The first rack housing 2a is provided with a pinion 12 connected to the input shaft 11 connected to the steering wheel. The pinion 12 meshes with rack teeth (not shown) formed on the rack shaft 3. is doing. Therefore, when the driver operates the steering wheel, the pinion 12 is rotated via the input shaft 11 by this operating force, and the rotation of the pinion 12 is converted into the linear movement of the rack shaft 3 by meshing the pinion 12 with the rack teeth. As a result, the front wheels are steered through the tie rods 7 and 8.

  The electric motor 4 is disposed around the rack shaft 3 in the yoke housing 2c constituting the rack housing 2, and has a function of applying a steering assist force to the rack shaft 3 via the motor shaft 5 as will be described later. Play. The electric motor 4 is a brushless DC motor, and has a drive stator 4a serving as a stator and a motor shaft 5 serving as a rotor. The drive stator 4a is wound with a coil and is disposed on the inner wall of the yoke housing 2c.

  The motor shaft 5 has a hollow cylindrical shape and is loosely fitted coaxially around the rack shaft 3. The motor shaft 5 is rotatably supported by the first rack housing 2a and the yoke housing 2c via a bearing 13 at a predetermined position.

  The ball screw device 6 is provided near the end of the motor shaft 5 in the direction of the arrow X1 in the drawing. The ball screw device 6 includes a ball screw nut 6a, a ball 6b, and the like.

  FIG. 2A is a partially enlarged view of the portion A shown in FIG. 1 as viewed from above the vehicle, and is a diagram schematically showing the main part of the power steering device 1.

  The rack housing 2 is disposed between a suspension member 20 extending in the vehicle width direction and a vehicle front member 21 such as an engine member (engine assembly) in an engine room at the front of the vehicle. In addition, the first rack housing 2a and the second rack housing 2b are connected to the suspension member 20 and the like via the EPS mount 22 and the mount bush 23, whereby the rack housing 2 is supported by the vehicle body.

  As described above, the first rack housing 2a and the yoke housing 2c are fastened by the bolts 24. That is, a plurality of bolt holes are formed in the flange portion of the first rack housing 2a and the flange portion of the yoke housing 2c. The bolts 24 are inserted into these bolt holes, and nuts are screwed into the inserted bolts 24, whereby the first rack housing 2a and the yoke housing 2c are fastened.

  FIG. 2B is a partially enlarged view of a portion B of the power steering apparatus shown in FIG. 2A, and is a cross-sectional view of flange portions of the first rack housing 2a and the yoke housing 2c.

  As shown in FIG. 2B, a washer-type strain sensor 25 formed in an annular shape is fitted into the bolt holes formed in the flange portions of the first rack housing 2a and the yoke housing 2c. Bolts 24 are inserted through the inside. Further, the flange portion of the first rack housing 2a and the flange portion of the yoke housing 2c are fastened by bolts 24 in an offset state. Thereby, since a moment force acts on the strain sensor 25 by a load load from the front of the vehicle, the load load from the front of the vehicle can be detected more reliably and a collision can be detected with higher accuracy. The strain sensor 25 outputs an output signal according to the amount of strain.

  The collision sensor 25 such as the strain sensor described above is an interference detection ECU (Electronic Control Unit) that detects interference of surrounding members (hereinafter referred to as surrounding members) such as the suspension member 20 and the vehicle front member 21 to the rack housing 2. , An electronic control unit) 30 is connected via a sensor harness 26 (FIG. 3). The interference detection ECU 30 detects the interference of surrounding members to the rack housing 2 based on the output signal from the collision sensor 25.

  The interference detection ECU 30 and an EPS (electric power steering device) ECU 31 to be described later are composed of a microcomputer, which executes various processes according to control and calculation programs and controls each part of the device (CPU ( Central Processing Unit (ROM), ROM (Read Only Memory) for storing CPU execution programs, RAM (Random Access Memory) for storing operation results, timers, counters, input / output interfaces (I / O), etc. Have.

  The interference detection ECU 30 is connected to an airbag G sensor 32 that detects an impact (acceleration) to the vehicle at the time of a vehicle collision. Based on the acceleration detected by the airbag G sensor 32 and the output signal from the collision sensor 25, the interference detection ECU 30 detects interference of surrounding members to the rack housing 2 at the time of a vehicle collision.

  The interference detection ECU 30 determines, for example, the collision of the vehicle based on the acceleration detected by the airbag G sensor 32, and outputs an output signal from the collision sensor 25 and a threshold map stored in advance in the ROM. Based on this, it is determined whether or not the surrounding member has interfered with the rack housing 2 in the event of a vehicle collision. Further, the interference detection ECU 30 damages the rack housing (including the inside of the rack housing) 2 due to the interference of surrounding members based on the output signal from the collision sensor 25 and the damage map stored in advance in the ROM. Estimate the level of. In the damage map, the relationship between the output signal from the collision sensor 25 and the level of damage to the rack housing 2 is experimentally obtained and stored in the ROM. For example, the level of damage to the rack housing 2 increases as the output signal from the collision sensor 25 increases.

  Further, the interference detection ECU 30 performs a corresponding process after the surrounding member interferes with the rack housing 2 based on the estimated damage level (for example, a warning to the user for limiting or stopping the application of the auxiliary torque). Then, a command signal is transmitted to the EPS ECU 31 or the alarm device 33 described later. Note that the alarm device 33 corresponds to, for example, a speaker that performs an alarm by voice, a warning light that performs an alarm by turning on or flashing light, a specific alarm message, a display device that displays an abnormality content, and the like. Further, the EPS ECU 31 communicates with an information center via a transceiver mounted on the vehicle, communicates with a dealer (dealer) registered in advance and capable of repairing the vehicle, etc. The details of the failure may be notified. As a result, it is possible to quickly deal with it.

  The interference detection ECU 30 is connected to an EPS ECU 31 for controlling a steering assist torque for assisting steering. The EPS ECU 31 controls the steering assist torque applied to the rack shaft 3 by controlling the electric motor 4. The interference detection ECU 30 and the EPS ECU 31 are configured separately, but may be configured integrally. The EPS ECU 31 limits or stops the application of the steering assist torque to the rack shaft 3, for example, based on the control signal from the interference detection ECU 30.

  Next, a control processing flow of the power steering apparatus 1 configured as described above will be described. FIG. 4 is a flowchart showing an example of a control processing flow of the power steering apparatus 1 according to the present embodiment. The control process flow shown in FIG. 4 is repeatedly executed every predetermined minute time.

  The collision sensor 25 detects the interference of surrounding members to the rack housing 2 (S100), and the airbag G sensor 32 detects the collision of an object with the vehicle (S110).

  The interference detection ECU 30 determines whether or not the output signal from the collision sensor 25 has changed (S120), and determines whether or not the output signal (acceleration) from the airbag G sensor 32 has changed. (S130).

  The interference detection ECU 30 determines that the output signal from the collision sensor 25 has changed (Yes in S120) and the output signal from the airbag G sensor 32 has changed (Yes in S130). When it is determined that the object has collided, the output signal from the collision sensor 25 is compared with the threshold map (S140), and it is determined whether or not the surrounding member has interfered with the rack housing 2 at the time of the vehicle collision (S140). S150). As described above, the collision of the object with the vehicle is determined based on the output signal from the airbag G sensor 32, and whether or not the surrounding member interferes with the rack housing 2 based on the output signal from the collision sensor 25. By determining, the interference of the surrounding members to the rack housing 2 can be determined more accurately.

  When the interference detection ECU 30 determines that the surrounding member has interfered with the rack housing 2 (Yes in S150), the rack housing due to the interference of the surrounding member based on the output signal from the collision sensor 25 and the damage map. 2 is estimated (S160).

  Further, the interference detection ECU 30 determines the corresponding processing after interference with the rack housing 2 according to the estimated damage level (S170), and stores the processing content in the RAM (S180).

  The interference detection ECU 30 transmits a command signal to the EPS ECU 31 or the alarm device 33 according to the determined response process (S190).

  As described above, in the power steering apparatus 1 according to this embodiment, the level of damage to the rack housing (including the inside of the rack housing) 2 is estimated based on the output signal from the collision sensor 25 disposed in the rack housing 2. Yes. Therefore, it is possible to accurately detect an impact on the rack mechanism in the rack housing 2 when the vehicle collides.

  Further, the interference detection ECU 30 determines the handling process after the interference with the rack housing 2 according to the estimated damage level. Therefore, it is possible to deal with damage more appropriately.

  As mentioned above, although the best mode for carrying out the present invention has been described using one embodiment, the present invention is not limited to such one embodiment, and within the scope not departing from the gist of the present invention, Various modifications and substitutions can be made to the above-described embodiment.

  For example, in the above-described embodiment, as the collision sensor 25, an annular washer-type strain sensor 25 fitted in a bolt hole formed in the flange portion of the first rack housing 2a and the yoke housing 2c is used. Alternatively, the film type sensor 35 may be disposed in the portion 2d where the stress concentration of the rack housing 2 occurs (FIG. 5). For example, during a vehicle collision, surrounding members interfere with the flange portions of the first rack housing 2a and the yoke housing 2c, and stress concentration occurs in the reduced root portion 2d of the first rack housing 2a. A film type sensor 35 is disposed along the circumferential direction on the root portion 2d. The film type sensor 35 is made of, for example, a composite material in which an optical fiber is inserted into a resin member, and changes its resistance value according to the deformation of the root portion 2d of the first rack housing 2a. Further, the level of damage to the rack housing 2 may be estimated with higher accuracy by using the washer-type strain sensor 25 and the film-type sensor 35 in combination.

  Moreover, the structure which arrange | positions the conduction | electrical_connection sensor 45 instead of the film-type sensor 35 in the site | part where the stress concentration of the rack housing 2 produces may be sufficient (FIG. 6). For example, the continuity sensor 45 connects the connector 45b to both ends of the wire 45a, and connects the connector 45b to the portion 2d where stress concentration occurs. In this case, when the rack housing 2 is deformed by a predetermined amount or more, the connector 45b is disconnected and disconnected. The interference detection ECU 30 can determine the deformation of the rack housing 2 by confirming the conductive state of the wire 45a. A sensor cover 45c is attached to the outer periphery of the continuity sensor 45 so that the wire 45a does not break due to catching during assembly or traveling.

  In the above embodiment, the stroke sensor 55 may be disposed between the suspension member 20 and the EPS mount 22 (FIG. 7). The stroke sensor 55 performs a stroke in the vehicle front-rear direction, and detects, for example, a contraction amount d of the mount bush 23 when a surrounding member interferes with the rack housing 2. The interference detection ECU 30 can estimate the level of damage to the rack housing 2 based on the amount of shrinkage d of the mount bush 23 detected by the stroke sensor 55.

  Further, instead of the stroke sensor 55 disposed between the suspension member 20 and the EPS mount 22, a configuration may be adopted in which a limit switch 65 is disposed on the EPS mount 22 (FIG. 8). The limit switch 65 outputs an on signal when it is turned on, and outputs an off signal when it is turned off. When the shrinkage amount d of the mount bush 23 is equal to or greater than a predetermined amount, the limit switch 65 is turned on, and the interference detection ECU 30 performs, for example, a rack housing based on an output signal (on signal or off signal) from the limit switch 65. 2 The damage to the inside can be predicted.

  In the above embodiment, a G (acceleration) sensor 34 for detecting the acceleration (vibration) of the rack mechanism in the rack housing 2 may be disposed on the rack housing (inner surface or outer surface) 2 (FIG. 3). The G sensor 34 is disposed on the upper side of the rack housing 2 and in a highly rigid portion so as not to be affected by noise. In addition, the measurement direction of acceleration by the G sensor 34 is set in the front-rear direction of the vehicle, and more accurate acceleration measurement is possible.

  For example, when the interference detection ECU 30 determines that the acceleration detected by the G sensor 34 is equal to or greater than the threshold, the interference detection ECU 30 transmits a control signal to the EPS ECU 31 to control the steering assist torque applied to the rack shaft 3. Stop. Thereby, the secondary malfunction of a rack mechanism, etc. can be prevented reliably.

  In the above embodiment, a load sensor 75 such as a load washer may be disposed between the EPS mount 22 and the suspension member 20 and / or the fastening bolt 36 to which the EPS mount 22 is fastened to the vehicle body ( FIG. 9).

  For example, when the interference detection ECU 30 determines that the load detected by the load sensor 75 is equal to or greater than the threshold value, the interference detection ECU 30 transmits a control signal to the EPS ECU 31 to control the steering assist torque applied to the rack shaft 3. Stop. Thereby, the secondary malfunction of a rack mechanism, etc. can be prevented reliably. The interference detection ECU 30 compares, for example, the load output from each load sensor 75 with a map obtained in advance by experiment, so that, for example, the portion of the rack housing 2 where the damage is large and the degree of damage are determined. It becomes possible to guess.

  In the above embodiment, the rack housing is obtained by arbitrarily combining the washer-type strain sensor 25, the film-type sensor 35, the continuity sensor 45, the stroke sensor 55, the limit switch 65, the G sensor 34, and the load sensor 75. 2 can be estimated with higher accuracy.

  In the above embodiment, the case where an object collides with the rack housing 2 from the front of the vehicle has been mainly described. However, depending on the mounting position of the power steering device 1, the object may May collide. For example, a large-mass component such as the engine ASSY may move forward due to inertia at the time of the vehicle collision and may collide with the power steering device 1 mounted on the vehicle forward side of the engine ASSY. In this case, since the inside of the rack housing 2 may be damaged in spite of no external damage on the appearance of the vehicle, it is effective to detect the impact on the EPS mechanism with high accuracy as described above. Become.

  The present invention can be used for a power steering device for a vehicle. The appearance, weight, size, running performance, etc. of the vehicle to be mounted are not limited.

1 is a schematic diagram of a power steering apparatus according to an embodiment of the present invention. (A) It is the elements on larger scale which looked at the A section shown in FIG. 1 from the vehicle upper direction, and is a figure which shows typically the principal part of a power steering apparatus. (B) It is the elements on larger scale of the B section of the power steering device shown in Drawing 2 (a), and is a sectional view of the flange part of the 1st rack housing and the yoke housing. 1 is a schematic block diagram illustrating a system configuration of a power steering apparatus according to an embodiment of the present invention. It is a flowchart which shows an example of the control processing flow of the power steering apparatus which concerns on a present Example. It is a figure which shows an example of the structure which has arrange | positioned the film type sensor in the site | part which stress concentration of a rack housing produces. It is a figure which shows an example of the structure which has arrange | positioned the conduction | electrical_connection sensor in the site | part which stress concentration of a rack housing produces. It is a figure which shows an example of the structure which has arrange | positioned the stroke sensor between a suspension member and EPS mount. It is a figure which shows an example of a structure which arrange | positions a limit switch in an EPS mount. It is a figure which shows an example of the structure which has arrange | positioned the load sensor between the EPS mount and the suspension member, and the fastening bolt.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power steering apparatus 2 Rack housing 2a 1st rack housing 2b 2nd rack housing 2c Yoke housing 3 Rack shaft 25 Collision sensor (washer type strain sensor)
30 Interference detection ECU
31 ECU for EPS
32 G sensor for airbag 35 Film type sensor 45 Continuity sensor 55 Stroke sensor 65 Limit switch

Claims (5)

A power steering device that is disposed at a front portion of a vehicle and applies steering assist torque for assisting steering to a rack shaft,
A power steering apparatus comprising: a collision detection unit that detects a collision of an object with a rack housing that houses the rack shaft. The power steering device according to claim 1,
The power steering apparatus according to claim 1, wherein the collision detection means detects a collision load on a fastening portion of the rack housing. The power steering device according to claim 1,
The power steering apparatus according to claim 1, wherein the collision detection means detects deformation of a stress concentration portion of the rack housing. The power steering device according to claim 1,
The power steering apparatus according to claim 1, wherein the collision detection means detects relative movement of the rack housing with respect to a vehicle body. The power steering device according to any one of claims 1 to 4,
The power steering apparatus according to claim 1, wherein when a collision of an object with the rack housing is detected by the collision detection means, a control mode of the steering assist torque applied to the rack shaft is changed.

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