TWI694940B - Electric power steering system - Google Patents

Abstract

An electric power steering system includes a first power module, a second power module and a control unit. The first power module includes a screw, a nut disposed on the screw in a thread matching manner and a first motor connected to the nut. The screw passes through the first motor. The second power module includes a second motor adjacent to the first motor, a transmission member connected to the second motor and a clutch. The clutch includes a first clutching member connected to the nut and a second clutching member connected to the transmission member. The first clutching member is clutched with the second clutching member. The control unit is electrically connected to the first motor, the second motor and the clutch. Besides, a control member adapted to the electric power steering system is also provided.

Description

Electric power steering system

The invention relates to an electric power steering system and a control method, and in particular to an electric power steering system that can provide additional power and save space and a control method suitable for the electric power steering system.

Electric Power Steering (EPS) system is a kind of power steering system that provides auxiliary torque by a motor. It is mainly composed of power motor, sensor, deceleration mechanism and controller. Compared with the traditional hydraulic power steering system, the electric power steering system can adjust the speed of the motor when the vehicle speed changes to provide optimized steering assistance, while taking into account the convenience at low speed and the stability at high speed, in addition, due to the reduction of the oil pump , Hydraulic tubing and other components, so it is conducive to modular design and matching to different car models. In recent years, it has become the main research object and has been widely used.

In the electric power steering system, the rack is used as the deceleration mechanism unit is called a rack assist type electric power steering system (Rack EPS, also known as R type EPS), and the speed reduction element is directly driven to move relative to the rack according to the assist motor , Or through the pinion gear to indirectly drive the reduction element to move relative to the rack, it can be further divided into rack direct drive type electric power steering system (RD-type EPS) and rack pinion drive type electric power steering system (RP -type EPS), these two steering systems can be provided by the rack The meshing teeth with high rigidity and strength can be used for medium and large general vehicles such as recreational vehicles or high-end cars. However, when the size or demand of the car body continues to increase, such as a medium-sized bus, the single electric power steering system described above will not provide sufficient steering power. On the other hand, in the driving system of electromechanical integration or electronic automation, the electric power steering system shoulders a very important responsibility in terms of safety. If the power assist motor loses its effectiveness, the driving vehicle will immediately lose auxiliary power and fall into the impossible. Among the dangers of turning with a predetermined radius of gyration.

To this end, researchers in related fields are devoted to increasing the number of power assist motors of the steering system. For example, Japanese Patent Publication No. JP 2005247214A discloses an electric power assist steering system. This electric power assist steering system is provided by installing power assist at different positions of the steering system. The motor, thus providing insufficient power and still having the output power of the other motor when one motor fails. However, due to the distributed installation of the motors, the overall volume of the electric power steering system is quite large, which in turn compresses the space and flexibility of the other components of the vehicle body.

The present invention provides an electric power steering system that can provide additional power and save space, and a control method suitable for the above electric power steering system to solve the above problems.

The electric power steering system of the present invention includes a first power module, a second power module and a control unit. The first power module includes a screw, a nut, and a first motor, the nut screw is provided on the screw, the first motor is connected to the nut, and the screw passes through the first motor; the second power module includes a second motor, a A transmission member and a clutch. The second motor is adjacent to the first motor. The transmission member is connected to the second motor. The clutch includes a first clutch member and a second clutch member. The first clutch member is connected to the nut and the second clutch member. Connected to the transmission member, the first clutch member can be coupled to the second clutch member, The control unit is electrically connected to the first motor, the second motor, and the clutch, and controls the first clutch member and the second clutch member to be coupled or disconnected.

In an embodiment of the invention, the transmission member includes a belt, the second clutch member includes a pulley, and the belt is sleeved on the pulley and the second motor.

In an embodiment of the invention, the first clutch member has a first gear hobbing structure, and the second clutch member has a second gear hobbing structure. When the first clutch member is combined with the second clutch member, the first The gear hobbing structure meshes with the second gear hobbing structure.

In an embodiment of the present invention, the inner wall of the first clutch member is provided with at least one groove, and the starting point and the end point of the at least one groove are located at both ends of the first clutch member in the axial direction.

In an embodiment of the invention, the shape of the at least one groove is a straight line or a screw thread.

In an embodiment of the present invention, the screw defines a first axis, the second motor includes an output shaft and a small pulley fixed to the output shaft, the output shaft defines a second axis, the transmission member is connected to the small pulley, and The first axis is parallel to the second axis.

In an embodiment of the invention, the electric power steering system further includes a sensing unit, and the sensing unit is electrically connected to the first motor, the second motor, and the control unit.

The control method of the present invention is applicable to an electric power steering system. The electric power steering system includes a first power module, a second power module, a control unit, and a sensing unit. the first The power module includes a screw, a nut screwed on the screw, and a first motor connected to the nut and passed by the screw; the second power module includes a second motor adjacent to the first motor, connected to the first A transmission part and a clutch of the two motors, the clutch includes a first clutch part connected to the nut and a second clutch part connected to the transmission part, the first clutch part can be coupled to the second clutch part, and the first The motor, the second motor, the clutch, the control unit, and the sensing unit are electrically connected to each other. The control method includes the sensing unit detecting a working torque output by the first motor and the control unit calculating a predetermined torque. When the control unit determines that the first motor has failed through the sensing unit, the control unit controls the first clutch member to be coupled to the second clutch member, and drives the second motor to output an alternative torque, and the magnitude of the alternative torque is equal to the predetermined torque . When the control unit determines that the first motor has not lost its function through the sensing unit, but the working torque is less than the predetermined torque, the control unit controls the first clutch member to be combined with the second clutch member, and drives the second motor to output a compensation torque, and the compensation The magnitude of the torque is the difference between the predetermined torque and the working torque, so that the first motor and the second motor jointly provide the predetermined torque.

10: Electric power steering system

100: the first power module

110: screw

120: nut

130: First motor

200: second power module

210: second motor

211: output shaft

212: Small pulley

220: Transmission parts

222: belt

230: clutch

231, 231a, 231b, 231c: the first clutch

232: electromagnetic coil

233: First hobbing structure

236: Second clutch piece

237: Pulley

238: Second hobbing structure

300: control unit

400: sensing unit

A: axial

A1: The first axis

A2: Second axis

G: groove

S01, S02, S03, S04, S05, S06, S07, S08, S09, S10, S11: steps

T _W : working torque

T _P : predetermined torque

T _R : Alternative torque

T _C : compensation torque

Figure 1 is a perspective schematic view of the electric power steering system of the first embodiment of the present invention; Figure 2 is an exploded schematic view of the electric power steering system of Figure 1; Figure 3 is a cross section of the electric power steering system of Figure 1 Figure 4 is a block diagram of the mechanical components of the electric power steering system of Figure 1; Figure 5 is a schematic diagram of the first clutch member and second clutch member of Figure 2 in a separated state; Figure 6 is the second FIG. 1 is a schematic diagram of a first clutch member and a second clutch member in a combined state; FIG. 7 is a schematic diagram of a first clutch member of an electric power steering system according to a second embodiment of the invention; FIG. 8 is a first embodiment of the invention A schematic diagram of the first clutch of the electric power steering system of the third embodiment; FIG. 9 is a schematic diagram of the first clutch of the electric power steering system of the fourth embodiment of the present invention; FIG. 10 is a functional block diagram of the electric power steering system of FIG. 1; FIG. 11 is a flowchart of steps of a control method according to an embodiment of the present invention.

The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of the preferred embodiments with reference to the drawings. It is worth mentioning that the direction terms mentioned in the following embodiments, for example: up, down, left, right, front or back, etc., are only referring to the directions of the attached drawings. Therefore, the directional terms used are for illustration, not for limiting the present invention. In addition, in the following embodiments, the same or similar elements will use the same or similar reference numerals.

Fig. 1 is a schematic perspective view of the electric power steering system of the first embodiment of the present invention, Fig. 2 is an exploded schematic view of the electric power steering system of Fig. 1, and Fig. 3 is a cross section of the electric power steering system of Fig. 1 Figure 4, Figure 4 is a block diagram of the mechanical components of the electric power steering system of Figure 1, please refer to Figure 1 to Figure 4. The electric power steering system 10 of this embodiment includes a first power module 100 and a second power module 200. The first power module 100 includes a screw 110, a nut 120, and a first motor 130. The nut 120 is screwed. Set on the screw 110, the first motor 130 is connected to the nut 120, and the screw 110 passes through the first motor 130; the second power module 200 includes a second motor 210, a transmission member 220, and a clutch 230, the second motor 210 Adjacent to the first motor 130, the transmission member 220 is connected to the second motor 210, the clutch 230 includes a first clutch member 231 and a second clutch member 236, the first clutch member 231 is connected to the nut 120, and the second clutch member 236 It is connected to the transmission member 220, and the first clutch member 231 is clutchably coupled to the second clutch member 236.

In detail, the first power module 100 of this embodiment is a rack direct drive type power module, wherein the first motor 130 can be screwed on the screw 110 through the nut 120, and both ends of the screw 110 (e.g. It is a one-direction rotation shaft connected to one wheel at each end of the screw 110). Therefore, when the first motor 130 is running, the nut 120 will rotate as the rotor of the first motor 130, and the screw 110 and the nut 120 are driven to move along the axial direction of the screw 110 to steer the wheels. On the other hand, the second power module 200 is a rack and pinion drive type power module, in which the nut 120 and the first clutch 231 are connected by a flange. In this embodiment, the transmission member 220 is a belt 222, and the second clutch member 236 includes a pulley 237. The pulley 237 has a plurality of gear teeth to facilitate the synchronous rotation of the belt 222 (that is, the transmission member 220), and the belt 222 is sleeved For the pulley 237 and the second motor 210. Since the first clutch member 231 is connected to the nut 120 and the second clutch member 236 is connected to the transmission member 220, when the first clutch member 231 and the second clutch member 236 are combined, the second motor 210 will drive the transmission member 220 when it is running The belt 222 further drives the pulley 237 and drives the nut 120 to rotate through the second clutch 236 and the first clutch 231 as another means to drive the screw 110 to move in the axial direction.

It is worth mentioning that the type of the transmission member 220 is not limited to this. According to the torque or rotation accuracy required to drive the nut 120, the belt 222 can also be replaced with other components that can transmit torque, such as chains or gears. The invention does not limit this.

In addition, as shown in FIG. 2, the second motor 210 is adjacent to the first motor 130, and the second motor 210 has an output shaft 211 and a small pulley 212 fixed to the output shaft 211. The extending direction of can define a first axis A1, and the extending direction of the output shaft 211 can define a second axis A2, wherein the transmission member 220 is connected to the small pulley 212, and the first axis A1 is parallel to the second axis A2. With the above-mentioned mechanism configuration, the overall volume occupied by the electric power steering system 10 can be greatly reduced, and compression to the installation space and elasticity for installing other components of the vehicle can be avoided.

Figure 5 is a schematic diagram of the first clutch member and the second clutch member of Figure 2 in a separated state Fig. 6 is a schematic diagram of the first clutch and the second clutch of Fig. 2 in a combined state, please refer to Fig. 5 and Fig. 6. In this embodiment, the clutch 230 is an electromagnetic clutch. Specifically, a plurality of electromagnetic coils 232 are arranged inside the first clutch 231. When the electromagnetic coil 232 is energized, the first clutch 231 will generate a magnetic force to cause the first The two clutch members 236 are adsorbed and combined. If the coupling state of the first clutch member 231 and the second clutch member 236 is to be released, only the power supply of the electromagnetic coil 232 needs to be stopped, and the second clutch member 236 will lose the suction power and move from the first clutch Piece 231 is separated. However, in other embodiments, the electromagnetic coil 232 can also be disposed on the second clutch member 236, and the first clutch member 231 can be attracted and separated by controlling the magnetic force through power-on and power-off. The present invention does not limit this.

On the other hand, as shown in FIG. 5, the first clutch member 231 has a first gear hobbing structure 233, and the second clutch member 236 has a second gear hobbing structure 238, in which the first gear hobbing structure 233 and the second The gear hobbing structure 238 is made by gear hobbing. Since the shape of the first gear hobbing structure 233 corresponds to the second gear hobbing structure 238, as shown in FIG. 5, when the first clutch member 231 is coupled to the second clutch member 236 in the above-described manner, the first gear hobbing The structure 233 can be engaged with the second gear hobbing structure 238, so that the first clutch member 231 and the second clutch member 236 are tightly coupled to ensure the stability of the synchronous rotation of the two.

FIG. 7 is a schematic diagram of the first clutch of the electric power steering system according to the second embodiment of the present invention. Please refer to FIG. 7. The first clutch member 231a of this embodiment is similar to the first clutch member 231 of the first embodiment, the main difference between the two is that: the inner wall of the first clutch member 231a is provided with at least one groove G, wherein the groove G The shape is a straight line, and the direction of the groove G is parallel to the axial direction A of the first clutch 231a. In other words, the starting point and the end point of the groove G are located at both ends of the first clutch 231a in the axial direction. In this embodiment, there are six grooves G, distributed at equal intervals along the circumferential direction of the inner wall of the first clutch 231a and filled with lubricating fluid, when the nut 120 rotates and drives the first clutch 231a to rotate together At this time, the lubricating fluid in the groove G will adhere to the surface of the screw 110 through the centripetal force during rotation, thereby raising the nut 120, the first separation The lubrication effect between the joint 231a and the screw 110 extends the service life of the components.

When the rotation speed of the screw 110 is faster or the outer diameter is larger and more lubricant is needed, the number of grooves G on the inner wall can also be appropriately increased. FIG. 8 is the electric power steering system of the third embodiment of the present invention. For the schematic diagram of the first clutch, please refer to Figure 7 and Figure 8. The first clutch member 231b of this embodiment is similar to the first clutch member 231a of the second embodiment, and the main difference between the two is that the first clutch member 231b is arranged in the upper, lower, left, and right directions of the circumferential direction Three grooves G, that is to say, a total of twelve grooves G are arranged on the inner wall of the first clutch member 231b, which can still provide sufficient lubricating fluid when the screw 110 rotates faster and the abrasion situation is severe. It is worth mentioning that the number of grooves G is not limited to this, as long as it is a groove G that can be prepared to meet the lubrication requirements of the screw 110 to store lubricating fluid, it is within the protection scope of the present invention.

FIG. 9 is a schematic diagram of the first clutch of the electric power steering system according to the fourth embodiment of the present invention. Please refer to FIGS. 7 and 9. The first clutch member 231c of this embodiment is similar to the first clutch member 231a of the second embodiment. The main difference between the two is that the groove G of the first clutch member 231c has a thread shape, that is, the first clutch member 231c The groove G is spirally arranged along the axial direction A. With this configuration, when the first clutch 231c rotates, the lubricating liquid inside the groove G can evenly flow along the thread to the surface of the screw 110, improving the lubrication effect.

Figure 10 is a block diagram of the components of the electric power steering system of Figure 1, please refer to Figure 10. In this embodiment, the electric power steering system 10 further includes a control unit 300 and a sensing unit 400, and the first motor 130, the second motor 210, the clutch 230, the control unit 300 and the sensing unit 400 are electrically connected to each other .

In detail, the control unit 300 of this embodiment includes an electronic control unit (Electric Control Unit, ECU), which can control the rotation speeds and output torques of the first motor 130 and the second motor 210 and the clutch through electrical signals or command signals The first clutch 231 and the second clutch 236 of 230 are combined or separated. On the other hand, the sensing unit 400 includes a torque sensor disposed on the steering shaft, which can detect the torque output by the first motor 130 and return it to the control unit 300. It is worth mentioning that the type of sensors included in the sensing unit 400 is not limited to this, and it can be replaced with other sensors such as a rotation speed sensor, a magnetic field sensor, etc. according to the discrimination needs of the control unit 300 .

In order to avoid that the torque output by the first motor 130 is insufficient to provide the torque required for vehicle steering, or to ensure that the vehicle still has sufficient power source to provide steering when the first motor 130 fails, the present invention provides a control method to respond The above situation. FIG. 11 is a flowchart of steps of a control method according to an embodiment of the present invention. Please refer to FIG. 11. First, after starting the electric power steering system 10, the first clutch member 231 and the second clutch member 236 are preset to be in a disengaged state. When the vehicle needs to turn, the first motor 130 will run at normal speed and output a working torque T _W , And the sensing unit 400 detects the working torque _TW output by the first motor 130 (step S01), and the control unit 300 is also detected and calculated by a sensor (such as the sensing unit 400) configured on the vehicle A predetermined torque _TP required for steering out (step S02). At this time, the control unit 300 determines whether the first motor 130 is disabled through the sensing unit 400 (step S03). If the first motor 130 is disabled, for example, the first motor 130 is stopped (that is, the working torque T _W is zero) Or the output working torque T _{W is} large or small. Based on safety considerations, the system can no longer rely on the output power of the first motor 130. Therefore, the control unit 300 controls the first clutch 231 to be coupled to the second clutch 236 (step S04), the second motor 210 and drives the output torque T _R to an alternative (step S05), and instead the magnitude of the torque T _R to the desired size equal to a predetermined torque T _P. In this way, even in the case where the first motor 130 fails, the electric power steering system 10 can still provide the required predetermined torque T _P with the assistance of the control unit 300 to turn the vehicle (step S06).

On the other hand, if the sensing unit 400 detects that the first motor 130 is stably outputting the working torque T _W , then the control unit 300 further determines the working torque T _W and after determining that the first motor 130 has not lost its function The predetermined torque _TP is compared, and it is confirmed whether the working torque _TW is smaller than the predetermined torque _TP (step S07). If the working torque _{TW is} not less than the predetermined torque _TP , it means that the first motor 130 alone can provide the power required for vehicle steering. At this time, the control unit 300 will continue to drive the first motor 130, and the first motor 130 provides the predetermined Torque _TP to steer the vehicle (step S08). If the working torque _{TW is} less than the predetermined torque _TP , it means that the power output by the first motor 130 alone is not sufficient to provide vehicle steering. Therefore, the control unit 300 controls the first clutch 231 to combine The second clutch 236 (step S09), and drives the second motor 210 to output a compensation torque T _C (step S10), and the magnitude of the compensation torque T _{C is} the difference between the predetermined torque _TP and the working torque _TW . That is, when the working torque T _W output by the first motor 130 is insufficient, the electric power steering system 10 can jointly provide the predetermined torque T by the first motor 130 and the second motor 210 with the assistance of the control unit 300 _P to steer the vehicle (step S11).

In summary, by arranging the second motor adjacent to the first motor, the electric power steering system of the present invention can provide an alternative or auxiliary power source through the clutch and the transmission member and save the space required by the system. In addition, through the control method provided by the present invention, the second motor can be driven to output alternative torque or compensation torque to avoid the steering risk that may exist when the first motor is disabled or the working torque is insufficient.

The above are only the preferred embodiments of the present invention, and all changes and modifications made in accordance with the scope of the patent application of the present invention shall fall within the scope of the present invention.

10: Electric power steering system

100: the first power module

110: screw

120: nut

130: First motor

200: second power module

210: second motor

211: output shaft

212: Small pulley

230: clutch

231: The first clutch

236: Second clutch piece

237: Pulley

Claims (5)

An electric power steering system includes: a first power module, including: a screw, defining a first axis; a nut, the screw is provided on the screw; and a first motor, connected to the nut, and the screw By the first motor, wherein when the first motor is running, the nut rotates as a rotor of the first motor, and the screw is driven to move along an axial direction of the screw by the screw relationship between the screw and the nut A second power module, including: a second motor adjacent to the first motor, the second motor includes an output shaft and a small pulley fixed to the output shaft, the output shaft defines a second An axis, and the first axis is parallel to the second axis; a transmission member connected to the second motor, the transmission member is a belt; and a clutch, including: a first clutch member connected to the nut; and A second clutch member is connected to the transmission member, and the first clutch member is clutchably coupled to the second clutch member. The second clutch member includes a pulley, wherein the belt sleeve is disposed on the pulley and the second A motor, and the belt is connected to the small pulley; and a control unit is electrically connected to the first motor, the second motor, and the clutch, and controls the first clutch member and the second clutch member to be coupled or disconnected. The electric power steering system according to claim 1, wherein the first clutch member has a first gear hobbing structure, and the second clutch member has a second gear hobbing structure, when the first clutch member is coupled to the In the second clutch member, the first gear hobbing structure meshes with the second gear hobbing structure. The electric power steering system according to claim 1, wherein the inner wall of the first clutch member is provided with at least one groove, and the starting point and end point of the at least one groove are respectively located on two axial directions of the first clutch member end. The electric power steering system according to claim 3, wherein the shape of the at least one groove is a straight line or a screw thread. The electric power steering system according to claim 1, further comprising a sensing unit, and the sensing unit is electrically connected to the first motor, the second motor, and the control unit.

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