CN112758172B - Electric power steering system - Google Patents
Electric power steering system Download PDFInfo
- Publication number
- CN112758172B CN112758172B CN201911077783.2A CN201911077783A CN112758172B CN 112758172 B CN112758172 B CN 112758172B CN 201911077783 A CN201911077783 A CN 201911077783A CN 112758172 B CN112758172 B CN 112758172B
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- Prior art keywords
- sensing unit
- hole
- electric power
- power steering
- steering system
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
- B62D5/0403—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by constructional features, e.g. common housing for motor and gear box
- B62D5/0406—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by constructional features, e.g. common housing for motor and gear box including housing for electronic control unit
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
- B62D5/0409—Electric motor acting on the steering column
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
- B62D5/0442—Conversion of rotational into longitudinal movement
- B62D5/0445—Screw drives
- B62D5/0448—Ball nuts
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D6/00—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits
- B62D6/001—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits the torque NOT being among the input parameters
Abstract
The invention provides an electric power steering system, which comprises a shell, a ball screw, a motor, an angle sensor and an arithmetic unit. The ball screw includes a nut and a screw. The motor is arranged in the shell and connected to the nut, the motor comprises a lining and a metal component, the metal component is fixedly arranged on the lining, and the metal component comprises a central part, a first wing part and a second wing part. The angle sensor is arranged in the shell and fixed relative to the shell, and comprises a first sensing unit and a second sensing unit, wherein the first sensing unit is provided with a first through hole, and the second sensing unit is provided with a second through hole. The operation unit is electrically connected to the first sensing unit and the second sensing unit. An outer diameter of the central portion is smaller than an aperture of each of the first through hole and the second through hole.
Description
Technical Field
The present invention relates to an electric power steering system, and more particularly, to an electric power steering system capable of calculating an axial position of a screw by means of an angle sensor disposed on a motor.
Background
An Electric Power Steering (EPS) system is a Power Steering system that provides an assist torque by means of an Electric motor, and is mainly composed of units such as an assist motor, a sensor, a speed reduction mechanism, and a controller, and can be roughly classified into three types according to the installation position of the assist motor: a Column-assist type (Column EPS, also called C-type EPS), a Pinion-assist type (Pinion EPS, also called P-type EPS), and a Rack-assist type (Rack EPS, also called R-type EPS), in which the Rack-assist type EPS is classified into a direct-drive type EPS and an indirect-drive type EPS according to the manner in which a power motor drives a Rack or a screw in a reduction mechanism. Compared with the traditional hydraulic power steering system, the electric power steering system can adjust the rotating speed of the motor when the vehicle speed changes so as to provide optimized steering power, and simultaneously has the advantages of convenience in low speed and stability in high speed.
In an electric power steering system, how to determine an absolute angle of steering of a vehicle body is an important issue. For this purpose, for example, chinese patent publication No. CN 103171616B discloses an electric power steering system, which includes a first rotor connected to an input shaft, a second rotor connected to an output shaft, a first angle element for measuring an absolute angle of the first rotor, a second angle element and a third angle element for measuring a relative angle of the first rotor, and an electronic control unit, wherein the electronic control unit obtains a reference angle according to the absolute angle and the relative angle, tracks and accumulates the relative angles of the second angle element and the third angle element to obtain a first absolute angle and a second absolute angle, and further calculates an absolute angle of a vehicle body during steering according to the first absolute angle and the second absolute angle.
In addition, chinese patent publication No. CN 106068219B discloses an electric power steering apparatus with a steering angle detection device, which includes a steering shaft, a torque sensor disposed on the steering shaft for measuring the steering wheel torque, and an angle sensor disposed on a motor, wherein the steering shaft and the motor are connected by a worm gear and a worm, and the steering angle of the vehicle body is calculated by an angle vernier algorithm and an angle following algorithm.
However, with the introduction of Advanced Driver Assistance Systems (ADAS) and unmanned automatic steering, steering wheels and steering columns are becoming unnecessary components, and more developers have been removing input shaft assemblies and torque sensors from the electric power steering System to change the electric connection control for the purpose of reducing the mechanism volume and saving the cost. In addition, in order to match different vehicle models, developers also aim to reduce the number of elements in the speed reducing mechanism and the transmission mechanism and avoid the influence of accumulated elements on the reliability of calculating the vehicle body rotation angle or the output shaft position due to aging or errors such as interference and clearance of connection of the elements. However, the above-mentioned prior art needs to provide a steering wheel and a steering column, and a sensor for measuring a steering angle is provided on the steering column, so that a space for providing the sensor is required to be reserved for a housing for mounting the steering column, which results in a large volume of the whole system, and the above-mentioned prior art is not suitable for various vehicle types. Moreover, when the electric power steering apparatus in the above-mentioned prior art is assembled, the assembling structure and mutual disposition relationship between the steering column and the sensor can make the assembling process more and complicated, not only reduce the assembling convenience, but also improve the assembling time and further improve the production cost.
Disclosure of Invention
The invention provides an electric power steering system, which can calculate the position of a screw rod in the axial direction by an angle sensor arranged on a motor, and can effectively reduce the number of elements, reduce the volume required during combination and improve the assembly convenience.
In order to achieve the purpose, the invention adopts the technical scheme that:
an electric power steering system, comprising:
a housing;
the ball screw comprises a nut and a screw rod, wherein the nut can drive the screw rod to axially displace when rotating;
a motor disposed in the housing and coupled to the nut, the motor capable of driving the nut to rotate, the motor comprising:
a bushing, configured on the screw rod and moving with the nut; and
a metal component fixed on the lining, the metal component comprises a central part, a first wing part and a second wing part, and the first wing part and the second wing part are arranged on the peripheral surface of the central part;
an angle sensor disposed within and fixed relative to the housing, the angle sensor comprising:
a first sensing unit having a first through hole and corresponding to the first wing; and
a second sensing unit having a second through hole and corresponding to the second wing part; and
the arithmetic unit is electrically connected with the first sensing unit and the second sensing unit;
wherein, an outer diameter of the central part is smaller than an aperture of the first through hole, and the outer diameter of the central part is smaller than an aperture of the second through hole, so that the central part is embedded in the first through hole and the second through hole;
when the electric power steering system is started, the first sensing unit and the second sensing unit sense a rotation angle of the motor and respectively output a first sensing signal and a second sensing signal to the arithmetic unit, and the arithmetic unit calculates a position of the screw in the axial direction according to the first sensing signal and the second sensing signal.
The electric power steering system, wherein: the metal member includes:
a first metal piece, including a first central part and the first wing part, the first wing part is connected to the peripheral surface of the first central part, an outer diameter of the first central part is smaller than the aperture of the first through hole, so that the first central part is embedded in the first through hole; and
a second metal piece, which comprises a second central part and a second wing part, wherein the second wing part is connected with the outer peripheral surface of the second central part, and the outer diameter of the second central part is smaller than the aperture of the second through hole, so that the second central part is embedded in the second through hole;
wherein the first central portion and the second central portion are connected to form the central portion.
The electric power steering system, wherein: the first sensing unit is arranged in the second through hole, and the angle sensor comprises a connecting part which is connected with the first sensing unit and the second sensing unit.
The electric power steering system, wherein: the bushing has a first portion and a second portion, an outer diameter of the first portion is smaller than an outer diameter of the second portion, the metal member is fixedly arranged on the second portion through a locking member, and the metal member is located on the radial outer side of the first portion.
The electric power steering system, wherein: the motor is a hollow torque motor and comprises a stator and a rotor, the rotor and the nut are coaxially arranged and synchronously rotate, the stator is fixed relative to the shell, and the screw rod penetrates through the nut.
The electric power steering system, wherein: the first sensing signal and the second sensing signal respectively correspond to a first measuring range and a second measuring range, wherein the first measuring range is different from the second measuring range, the computing unit obtains the position through a first algorithm according to a difference value of the first sensing signal and the second sensing signal, and updates the position through a second algorithm according to a time interval and a variation of the rotation angle.
The electric power steering system, wherein: the maximum outer diameter of the first metal piece is smaller than the aperture of the second through hole.
In summary, the electric power steering system of the present invention can obtain the first sensing signal and the second sensing signal by the first sensing unit and the second sensing unit disposed in the housing, and further calculate the axial position of the screw, so that the problem that the position of the screw is difficult to know when there is no input shaft can be solved. In addition, the input shaft and the sensing unit arranged on the input shaft can be omitted, so that the occupied volume of elements and the cost can be greatly reduced, and the system can correspond to various vehicle types and improve the function and the convenience of the system.
Drawings
Fig. 1 is an external view schematically illustrating an electric power steering system according to an embodiment of the present invention.
Fig. 2 is an axial sectional view of the electric power steering system of fig. 1.
FIG. 3 is a schematic diagram of the internal components of the electric power steering system of FIG. 1 with a portion of the housing removed.
Fig. 4 is a schematic view of the first sensing unit, the second sensing unit, the first metal element and the second metal element in fig. 3.
Fig. 5 is an axial sectional view of an electric power steering system according to another embodiment of the present invention.
FIG. 6 is a schematic diagram of the internal components of the electric power steering system of FIG. 5 with a portion of the housing removed.
FIG. 7 is a schematic view of the angle sensor and the metal member of FIG. 6.
FIG. 8 is a flowchart illustrating a method for calculating a screw position according to another embodiment of the present invention.
Fig. 9 is a schematic diagram of the first sensing signal and the second sensing signal respectively corresponding to the first sensing unit and the second sensing unit of fig. 8.
Fig. 10 is a schematic diagram of the first sensing signal and the second sensing signal of fig. 9 with a target angle.
Fig. 11 is a schematic diagram of a difference between the first sensing signal and the second sensing signal of fig. 9 after subtraction.
FIG. 12 is a comparison of positive difference values with total rotation angles of FIG. 11.
Description of reference numerals: 100. 100' -an electric power steering system; 110-a housing; 120-ball screw; 122-a nut; 124-screw rod; 126-rack portion; 130. 130' -a motor; 131-a stator; 132-a rotor; 133. 133' -a bushing; 133a, 133 a' -first portion; 133b, 133 b' -a second portion; 134-a first metal piece; 134 a-first central portion; 134b, 136 b-first wing portion; 134c, 135c, 136 e-perforations; 134d, 135d, 136 d-outer peripheral surface; 135-a second metal piece; 135 a-a second central portion; 135b, 136 c-a second wing; 136. 136' -a metal member; 136 a-a central portion; 137-locking piece; 140. 140' -an angle sensor; 142. 142' -a first sensing unit; 143. 143' -a first through hole; 144. 144' -a second sensing unit; 145. 145' -a second through hole; 147-a connecting portion; 160-an arithmetic unit; 170-input shaft; a-axial direction; d-difference; dpos-positive difference; d1, D2, D3, D4, D6-outer diameter; d5-maximum outer diameter; h1, H2-pore size; r1 — first measurement range; r2 — second measurement range; s1 — a first sense signal; s2 — a second sense signal; s01, S02, S03, S04, S05, S06-steps; t-time interval; theta-rotation angle; thetaactual-an actual angle; thetacorrection-an angle correction; delta theta-amount of change.
Detailed Description
The foregoing and other technical and other features and advantages of the invention will be apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings. The following examples refer to directional terms such as: up, down, left, right, front or rear, etc., are referred to only in the direction of the attached drawings. Accordingly, the directional terminology is used for purposes of illustration and is in no way limiting. In addition, in the following embodiments, the same or similar elements will be given the same or similar reference numerals.
Referring to fig. 1 to 3, fig. 1 is an external view of an electric power steering system 100 according to an embodiment of the present invention, fig. 2 is an axial cross-sectional view of the electric power steering system 100 of fig. 1, fig. 3 is a schematic view of internal components of the electric power steering system 100 of fig. 1 with a portion of a housing 110 removed, and fig. 3 shows the internal components in a burst state. The electric power steering system 100 of the present embodiment includes a housing 110, a ball screw 120, a motor 130, an angle sensor 140 and a computing unit 160, wherein the ball screw 120 includes a nut 122 and a screw 124, and the nut 122 drives the screw 124 to perform axial displacement when rotating. The motor 130 is disposed in the housing 110 and connected to the nut 122, and the motor 130 drives the nut 122 to rotate. The angle sensor 140 is disposed in the housing 110 and fixed relative to the housing 110, the angle sensor 140 includes a first sensing unit 142 and a second sensing unit 144, and the operation unit 160 is electrically connected to the first sensing unit 142 and the second sensing unit 144.
In detail, the screw 124 is an output shaft connected to wheels of the vehicle, and the electric power steering system 100 further includes an input shaft 170 connected to a steering wheel to provide a steering torque, and the input shaft 170 and the screw 124 are connected to and engaged with each other through the rack portion 126 of the ball screw 120. For example, the input shaft 170 may be sleeved over a pinion gear structure and coupled to the rack portion 126 via the pinion gear tooth structure. On the other hand, the electric power steering system 100 can determine the absolute angle of steering of the vehicle body by changing the position of the output shaft in the axial direction a. Specifically, the nut 122 is screwed on the Screw 124 by a plurality of rolling bodies (not shown), and when the nut 122 rotates, the Screw 124 is pushed by the plurality of rolling bodies to move in the axial direction a, and the operation principle of the Ball Screw 120(Ball Screw) is conventional and will not be described herein.
In the embodiment, the motor 130 includes a stator 131, a rotor 132, a bushing 133 and a metal member 136, wherein the stator 131 is fixed relative to the housing 110, the bushing 133 is disposed on the screw 124 and moves with the nut 122, the metal member 136 is fixed on the bushing 133, the metal member 136 includes a first metal 134 and a second metal 135, the rotor 132, the bushing 133, the metal member 136 and the nut 122 are coaxially disposed and rotate synchronously, and the stator 131, the rotor 132, the bushing 133 and the metal member 136 are disposed in the housing 110. When the electric power steering system 100 is started, the rotor 132 will rotate relative to the stator 131 and drive the bushing 133 and the nut 122 to rotate together, so as to push the screw 124 to move in the axial direction a to achieve the effect of steering the vehicle body.
In the embodiment, the motor 130 is a hollow torque motor, and since the shaft center portion is hollow, the nut 122 can be directly driven to rotate by the rotor 132 without a speed reduction mechanism, thereby eliminating the abrasion and power loss caused by gear transmission. In addition, the screw 124 directly passes through the rotor 132, the bushing 133 and the nut 122, and because the rotor 132 and the nut 122 are coaxially connected and synchronously rotate, the smoothness of the nut 122 during rotation is improved, and the angle sensor 140 is configured in the housing 110, so that the angle sensor does not need to be additionally configured on the input shaft 170, the required cost can be greatly reduced, even the configuration of the input shaft 170 can be omitted, and the development adaptability of the automatic driving vehicle is higher.
Referring to fig. 2 to 4, fig. 4 is a schematic view of the first sensing unit 142, the second sensing unit 144, the first metal part 134 and the second metal part 135 in fig. 3. In the present embodiment, the metal member 136 includes a first metal part 134 and a second metal part 135, and the first metal part 134 and the second metal part 135 are fixed on the bushing 133. Specifically, the bushing 133 has a first portion 133a and a second portion 133b, an outer diameter D1 of the first portion 133a is smaller than an outer diameter D2 of the second portion 133b, wherein the first metal piece 134 and the second metal piece 135 are stacked along the axial direction a and fixed on the second portion 133b by at least one locking member 137, and the first metal piece 134 and the second metal piece 135 are located at a radial outer side of the first portion 133 a. More specifically, the number of the locking members 137 may be plural, and the locking members 137 may be screws, the first metal member 134 is provided with a plurality of through holes 134c, the second metal member 135 is provided with a plurality of through holes 135c, the second portion 133b is provided with a plurality of screw holes (not shown) facing the end surfaces of the first metal member 134 and the second metal member 135, the number of the through holes 134c, the number of the through holes 135c and the number of the screw holes may correspond to the number of the locking members 137, in this manner, the locking member 137 can be inserted through the through hole 134c, the through hole 135c and locked into the screw hole of the second portion 133b, so that the first metal piece 134 and the second metal piece 135 are fixed to the bushing 133 to be rotatable synchronously with the bushing 133 and the nut 122, and the portions of the first metal member 134 and the second metal member 135 beyond the bushing 133 can be minimized, either in the axial direction a or in the radial direction of the screw 124, thereby reducing the volume occupied by the motor 130. In addition, fig. 2 only shows a part of the locking pieces 137 due to the view angle, and fig. 3 only shows two locking pieces 137 for simplifying the drawing, and the remaining locking pieces 137 are omitted. The first metal part 134 includes a first central portion 134a and a plurality of first wing portions 134b, the number of the first wing portions 134b is five, the second metal part 135 includes a second central portion 135a and a second wing portion 135b, wherein the plurality of first wing portions 134b are disposed at equal angular intervals and connected to the outer peripheral surface 134d of the first central portion 134a, and the second wing portion 135b is fan-shaped and connected to the outer peripheral surface 135d of the second central portion 135 a.
The angle sensor 140 includes a first sensing unit 142 and a second sensing unit 144, the first sensing unit 142 has a first through hole 143 corresponding to the first wing 134b, the second sensing unit 144 has a second through hole 145 corresponding to the second wing 135b, an outer diameter D3 of the first central portion 134a is smaller than an aperture H1 of the first through hole 143 of the first sensing unit 142, an outer diameter D4 of the second central portion 135a is smaller than an aperture H2 of the second through hole 145 of the second sensing unit 144, so that the first central portion 134a and the second central portion 135a are respectively embedded in the first through hole 143 of the first sensing unit 142 and the second through hole 145 of the second sensing unit 144. In addition, when the first metal part 134 and the second metal part 135 are assembled, the first central portion 134a and the second central portion 135a are connected to form a central portion (not labeled). In the embodiment, the central Angle formed by the second wing portion 135b and the second central portion 135a is 180 degrees, and the plurality of first wing portions 134b are disposed at equal angular intervals, so that the first wing portions 134b and the second wing portions 135b are designed to have different angular intervals, and the first sensing unit 142 and the second sensing unit 144 measure two sensing signals with different measuring ranges, thereby facilitating the operation of the operation unit 160 to perform the Angle Vernier Algorithm (Vernier Algorithm) and the Angle following Algorithm (Angle Follower Algorithm), the details of which are described later.
When the motor 130 is assembled, the first sensing unit 142 corresponds to the first metal part 134, the second sensing unit 144 corresponds to the second metal part 135, and the first central portion 134a and the second central portion 135a are respectively embedded in the first through hole 143 of the first sensing unit 142 and the second through hole 145 of the second sensing unit 144. With such a configuration, when the first metal part 134 and the second metal part 135 rotate synchronously with the nut 122, the first sensing unit 142 can sense the rotation angle of the first metal part 134 by the magnetic signal or the optical reflection signal and output a first sensing signal S1, the second sensing unit 144 can sense the rotation angle of the second metal part 135 by the magnetic signal or the optical reflection signal and output a second sensing signal S2, and the arithmetic unit 160 can calculate a position of the screw 124 in the axial direction a according to the first sensing signal S1 and the second sensing signal S2, so as to obtain an accurate tire angle, thereby enabling the vehicle to steer accurately. In addition, since the first central portion 134a and the second central portion 135a are respectively embedded in the first through hole 143 of the first sensing unit 142 and the second through hole 145 of the second sensing unit 144, the elements can be more tightly combined with each other, further reducing the volume of the entire electric power steering system 100.
In addition, in the embodiment, a maximum outer diameter D5 of the first metal element 134 is smaller than the aperture H2 of the second through hole 145, so that, when the electric power steering system 100 is assembled, the first sensing unit 142 and the second sensing unit 144 can be fixed in the housing 110 in advance, the first metal element 134 and the second metal element 135 are sleeved on the first portion 133a and locked on the second portion 133b along the axial direction a, and then the first portion 133a of the bushing 133 and the first metal element 134 can pass through the second through hole 145 of the second sensing unit 144, because the maximum outer diameter D5 of the first metal element 134 is smaller than the aperture H2 of the second through hole 145, the first metal element 134 can easily pass through the second through hole 145 and is disposed between the first sensing unit 142 and the second sensing unit 144, so that the first sensing unit 142 and the second sensing unit 144 correspond to the first metal element 134 and the second metal element 135, the purpose of convenient installation is achieved.
Referring to fig. 5 to 7, fig. 5 is an axial cross-sectional view of an electric power steering system 100 'according to another embodiment of the present invention, fig. 6 is a schematic view of internal components of the electric power steering system 100' of fig. 5 with a portion of a housing 110 removed, fig. 6 shows the internal components in an exploded state, and fig. 7 is a schematic view of an angle sensor 140 'and a metal member 136' of fig. 6. In the electric power steering system 100 'of the present embodiment, the metal member 136' is fixed on the bushing 133 ', the metal member 136' includes a central portion 136a, a plurality of first wing portions 136b and a second wing portion 136c, the first wing portions 136b and the second wing portions 136c are disposed on an outer circumferential surface 136d of the central portion 136a, specifically, the number of the first wing portions 136b is five, the plurality of first wing portions 136b are disposed on the outer circumferential surface 136d of the central portion 136a at equal angular intervals, the second wing portions 136c are fan-shaped and form a central angle of 180 degrees with an axis of the central portion 136a, the second wing portions 136c are located radially outside the first wing portions 136b, and the radially inner side of the second wing 136c is connected to the radially outer side of a portion of the first wing 136b, in other words, the first wing 136b is located between and connects the central portion 136a and the second wing 136 c.
The angle sensor 140 ' includes a first sensing unit 142 ', a second sensing unit 144 ' and a plurality of connecting portions 147, where the number of the connecting portions 147 is illustrated as four, the first sensing unit 142 ' has a first through hole 143 ' and corresponds to the first wing portion 136b, the second sensing unit 144 ' has a second through hole 145 ' and corresponds to the second wing portion 136c, the first sensing unit 142 ' is disposed in the second through hole 145 ', and the connecting portion 147 connects the first sensing unit 142 ' and the second sensing unit 144 ', in other words, the second through hole 145 ' covers the first through hole 143 '. An outer diameter D6 of the central portion 136a is smaller than an aperture H1 of the first through hole 143 ', and an outer diameter D6 of the central portion 136a is smaller than an aperture H2 of the second through hole 145', so that the central portion 136a is embedded in the first through hole 143 'and the second through hole 145'. The electric power steering system 100' differs from the electric power steering system 100 described above mainly in that: the angle sensor 140 of the electric power steering system 100 includes two independent components, i.e., a first sensing unit 142 and a second sensing unit 144, the angle sensor 140 'of the electric power steering system 100' is a single component, the metal member 136 of the electric power steering system 100 includes two independent components, i.e., a first metal part 134 and a second metal part 135, and the metal member 136 'of the electric power steering system 100' is a single component, so that the overall structure is simplified, and interference generated when the angle sensor 140 'and the metal member 136' are assembled is reduced.
When the motor 130 ' is assembled, the central portion 136a of the metal member 136 ' is embedded in the first through hole 143 ', and the first sensing unit 142 ' and the second sensing unit 144 ' respectively correspond to the first wing portion 136b and the second wing portion 136c, so that the first sensing unit 142 ' and the second sensing unit 144 ' can respectively sense the rotation angles of the first wing portion 136b and the second wing portion 136c and respectively output the first sensing signal S1 and the second sensing signal S2, in this embodiment, the second wing portion 136c is fan-shaped and forms a 180-degree central angle with the axis of the central portion 136a, and the plurality of first wing portions 136b are arranged at equal angular intervals, so that the second wing portion 136c and the first wing portions 136b are designed at different angular intervals, so that the first sensing unit 142 ' and the second sensing unit 144 ' measure two sensing signals with different measurement ranges, and the arithmetic unit 160 performs arithmetic operation, in addition, compared to the motor 130, the motor 130 ' of the embodiment further reduces the axial gap between the first sensing unit 142 and the second sensing unit 144 and the axial gap between the first metal part 134 and the second metal part 135, so that the space required by the motor 130 ' in the entire electric power steering system 100 ' can be further reduced.
On the other hand, similar to the electric power steering system 100, in the present embodiment, the bushing 133 ' has a first portion 133a ' and a second portion 133b ', wherein an outer diameter D1 of the first portion 133a ' is smaller than an outer diameter D2 of the second portion 133b ', the metal member 136 ' is fixed to the second portion 133b ' by a locking member (not shown), and the metal member 136 ' is located radially outside the first portion 133a '. Specifically, the metal member 136 ' may be provided with a plurality of through holes 136e for the locking member to pass through, and the end surface of the second portion 133b ' facing the metal member 136 ' may be provided with a plurality of screw holes (not shown) for the locking member to lock into, and the related description of the locking member may refer to fig. 3. Therefore, the electric power steering system 100 'can also minimize the portion of the metal member 136' that extends beyond the bushing 133 ', thereby reducing the volume occupied by the motor 130'.
Furthermore, since the outer diameter D6 of the central portion 136a of the metal member 136 'is smaller than the aperture H1 of the first through hole 143', when assembling the electric power steering system 100 ', the angle sensor 140' formed by the first sensing unit 142 'and the second sensing unit 144' can be fixed in the housing 110, and then the first portion 133a 'of the bushing 133' and the central portion 136a of the metal member 136 'pass through the first through hole 143', so that the first sensing unit 142 'and the second sensing unit 144' correspond to the first wing portion 136b and the second wing portion 136c, respectively, thereby achieving the purpose of convenient installation.
Fig. 8 is a flowchart illustrating a method for calculating a screw position according to another embodiment of the present invention, please refer to fig. 8. Here, the electric power steering system 100 is explained, in this embodiment, a position of the screw 124 in the axial direction a is calculated by the first sensing signal S1 and the second sensing signal S2 output by the first sensing unit 142 and the second sensing unit 144 disposed on the motor 130, and each step will be explained in detail as follows: first, the electric power steering system 100 is started (step S01), when the electric power steering system 100 is started, the first sensing unit 142 and the second sensing unit 144 sense the rotation angles of the first metal element 134 and the second metal element 135, measure the rotation angle θ of the rotor 132 of the motor 130 and respectively obtain a first sensing signal S1 and a second sensing signal S2, at this time, the first sensing unit 142 and the second sensing unit 144 respectively output the first sensing signal S1 and the second sensing signal S2 to the computing unit 160 (step S02), and the computing unit 160 obtains the position according to a first algorithm by using a difference d between the first sensing signal S1 and the second sensing signal S2 (step S03). In the embodiment, the first algorithm is an angle vernier algorithm, and an exact measurement result can be calculated by using a difference value of the sensing signals of two different measurement ranges.
Referring to fig. 9 to 12, fig. 9 is a schematic diagram of the first sensing signal S1 and the second sensing signal S2 respectively corresponding to the first sensing unit 142 and the second sensing unit 144 of fig. 8, fig. 10 is a schematic diagram of the first sensing signal S2 and the second sensing signal S2 of fig. 9 and a target angle, fig. 11 is a schematic diagram of a difference value obtained by subtracting the first sensing signal S1 and the second sensing signal S2 of fig. 9, and fig. 12 is a schematic diagram of a comparison between a positive difference value and a total rotation angle of fig. 11. In detail, in the present embodiment, it is assumed that the total rotation angle range of the input shaft 170 (i.e., the total rotation angle of the steering wheel) is between 0 to 9000 degrees; the first sensing signal S1 measured by the first sensing unit 142 corresponds to a first measurement range R1, in this embodiment, the first measurement range R1 is 125 degrees; the second sensing signal S2 measured by the second sensing unit 144 corresponds to a second measurement range R2, which is 360 degrees in the present embodiment of the second measurement range R2. When the measured target value exceeds the respective measuring range, the first sensing signal S1 or the second sensing signal S2 will be incremented again from 0 degrees. It should be noted that, in the angle vernier algorithm, the first measurement range R1 must be different from the second measurement range R2, so that the difference d can be obtained successfully when the measurements are performed for the same rotation angle.
Referring to fig. 10, in the present embodiment, it is assumed that the actual moving distance of the screw 124 is 36mm, the rotation angle θ of the nut 122 is 1620 degrees, and since the rotor 132 and the nut 122 are coaxially connected and synchronously rotate, the rotation angle θ of the rotor 132 of the motor 130 is the rotation angle of the nut 122, at this time, the corresponding first sensing signal S1 is 120 degrees, the second sensing signal S2 is 180 degrees, and the difference d is S1-S2-60 degrees, and since the difference d is a negative number, the second measurement range R2 needs to be compensated, or the difference d becomes a positive difference dpos-60 + R2-300 as compared with fig. 11. When the positive difference dpos is obtained, the angle correction can be obtained by the following table one or fig. 12:
table-actual rotation angle, positive difference and angle correction quantity comparison relationship
| Lower bound of actual angle of rotation | Upper bound of actual angle of rotation | Positive number of | Angle correction | |
| 0 | 124 | 0 | 0 | |
| 125 | 249 | 235 | 125 | |
| 250 | 374 | 110 | 250 | |
| 375 | 499 | 345 | 375 | |
| 500 | 624 | 220 | 500 | |
| 625 | 749 | 95 | 625 | |
| 750 | 874 | 330 | 750 | |
| 875 | 999 | 205 | 875 | |
| 1000 | 1124 | 80 | 1000 | |
| 1125 | 1249 | 315 | 1125 | |
| 1250 | 1374 | 190 | 1250 | |
| 1375 | 1499 | 65 | 1375 | |
| 1500 | 1624 | 300 | 1500 | |
| 1625 | 1749 | 175 | 1625 | |
| 1750 | 1874 | 50 | 1750 | |
| 1875 | 1999 | 285 | 1875 | |
| 2000 | 2124 | 160 | 2000 | |
| (slight) | (slight) | (slight) | (slight) | |
| 8500 | 8624 | 140 | 8500 | |
| 8625 | 8749 | 15 | 8625 | |
| 8750 | 8874 | 250 | 8750 | |
| 8875 | 8999 | 125 | 8875 |
From the table one or fig. 12, it can be seen that there are 72 different positive difference values dpos, and the total measurement range (9000 degrees) is divided into 72 regions, and the actual rotation angle θ falls in the 13 th region when the positive difference value dpos is 300 degrees, and the angle correction amount is 1500 degrees, so the actual rotation angle θ can be obtained by the following equation:
θactual＝θcorrection+S1
wherein theta isactualIs the actual angle of rotation of the nut 122, and θcorrectionThen is the angle correction. Therefore, the actual rotation angle θ is 1500+120 degrees 1620 degrees, wherein the angle correction amount can also be regarded as the product of the angle amplitude (125 degrees) of a single region and the region interval number (13-1 is 12).
After the actual rotation angle θ of the nut 122 is obtained by the first algorithm, the position of the screw 124 in the axial direction a can be obtained by calculating the linear angular transmission ratio, and at this time, the operation unit 160 can verify the operation result (step S04), that is, determine whether the sensing signal has abnormal phenomena such as obvious fluctuation or exceeding the measurement range. If the first sensing signal S1 and the second sensing signal S2 are both reliable and have no obvious abnormality (step S05), the operation unit 160 uses the obtained rotation angle θ as an initial value, and updates the rotation angle θ and the position of the screw 124 according to the time interval t elapsed and the variation Δ θ of the rotation angle θ by a second algorithm (step S06). In the present embodiment, the second algorithm is an angle following algorithm, which utilizes the principle of integration to add the total of the angle change Δ θ in the time interval t to the initial value obtained by the first algorithm to update the rotation angle θ. On the other hand, if the first sensing signal S1 or the second sensing signal S2 is abnormal or the electric power steering system 100 is restarted, the computing unit 160 will read the first sensing signal S1 and the second sensing signal S2 outputted by the first sensing unit 142 and the second sensing unit 144 again, and repeat the above steps.
In summary, the electric power steering system of the present invention can obtain the first sensing signal and the second sensing signal by the first sensing unit and the second sensing unit disposed in the housing, and further calculate the axial position of the screw, so that the problem that the position of the screw is difficult to know when there is no input shaft can be solved. In addition, the input shaft and the sensing unit arranged on the input shaft can be omitted, so that the occupied volume of elements and the cost can be greatly reduced, and the system can correspond to various vehicle types and improve the function and the convenience of the system.
The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the protection scope of the present invention.
Claims (7)
1. An electric power steering system, comprising:
a housing;
the ball screw comprises a nut and a screw rod, wherein the nut can drive the screw rod to axially displace when rotating;
a motor disposed in the housing and coupled to the nut, the motor capable of driving the nut to rotate, the motor comprising:
a bushing, configured on the screw rod and moving with the nut; and
a metal component fixed on the lining, the metal component comprises a central part, a first wing part and a second wing part, and the first wing part and the second wing part are arranged on the peripheral surface of the central part;
an angle sensor disposed within and fixed relative to the housing, the angle sensor comprising:
a first sensing unit having a first through hole and corresponding to the first wing; and
a second sensing unit having a second through hole and corresponding to the second wing part; and
the arithmetic unit is electrically connected with the first sensing unit and the second sensing unit;
wherein, an outer diameter of the central part is smaller than an aperture of the first through hole, and the outer diameter of the central part is smaller than an aperture of the second through hole, so that the central part is embedded in the first through hole and the second through hole;
when the electric power steering system is started, the first sensing unit and the second sensing unit sense a rotation angle of the motor and respectively output a first sensing signal and a second sensing signal to the arithmetic unit, and the arithmetic unit calculates a position of the screw in the axial direction according to the first sensing signal and the second sensing signal.
2. The electric power steering system according to claim 1, characterized in that: the metal member includes:
a first metal piece, including a first central part and the first wing part, the first wing part is connected to the peripheral surface of the first central part, an outer diameter of the first central part is smaller than the aperture of the first through hole, so that the first central part is embedded in the first through hole; and
a second metal piece, which comprises a second central part and a second wing part, wherein the second wing part is connected with the outer peripheral surface of the second central part, and the outer diameter of the second central part is smaller than the aperture of the second through hole, so that the second central part is embedded in the second through hole;
wherein the first central portion and the second central portion are connected to form the central portion.
3. The electric power steering system according to claim 1, characterized in that: the first sensing unit is arranged in the second through hole, and the angle sensor comprises a connecting part which is connected with the first sensing unit and the second sensing unit.
4. The electric power steering system according to claim 1, characterized in that: the bushing has a first portion and a second portion, an outer diameter of the first portion is smaller than an outer diameter of the second portion, the metal member is fixedly arranged on the second portion through a locking member, and the metal member is located on the radial outer side of the first portion.
5. The electric power steering system according to claim 1, characterized in that: the motor is a hollow torque motor and comprises a stator and a rotor, the rotor and the nut are coaxially arranged and synchronously rotate, the stator is fixed relative to the shell, and the screw rod penetrates through the nut.
6. The electric power steering system according to claim 1, characterized in that: the first sensing signal and the second sensing signal respectively correspond to a first measuring range and a second measuring range, wherein the first measuring range is different from the second measuring range, the computing unit obtains the position through a first algorithm operation according to a difference value obtained by subtracting the second sensing signal from the first sensing signal, and updates the position through a second algorithm according to a variation of the rotation angle in a time interval.
7. The electric power steering system according to claim 2, characterized in that: the maximum outer diameter of the first metal piece is smaller than the aperture of the second through hole.
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| CN201911077783.2A CN112758172B (en) | 2019-11-06 | 2019-11-06 | Electric power steering system |
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| CN201911077783.2A CN112758172B (en) | 2019-11-06 | 2019-11-06 | Electric power steering system |
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| CN112758172B true CN112758172B (en) | 2022-01-18 |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3539107A1 (en) * | 1984-11-02 | 1986-05-22 | Honda Motor Co Ltd | MOTOR DRIVEN SERVO DEVICE |
| CN201989842U (en) * | 2011-03-25 | 2011-09-28 | 比亚迪股份有限公司 | Steering column power assisting mechanism |
| CN104210544A (en) * | 2013-05-29 | 2014-12-17 | 爱信精机株式会社 | Rear wheel steering apparatus for vehicle |
| CN105599807A (en) * | 2014-11-19 | 2016-05-25 | 日立金属株式会社 | Torque steering angle sensor |
| DE102018202052A1 (en) * | 2017-02-10 | 2018-08-16 | Denso Corporation | Rotation sensing device |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6543570B2 (en) * | 2001-07-03 | 2003-04-08 | Trw Inc. | Electric power assisted steering system with friction compensation and method for controlling the system |
| GB201411297D0 (en) * | 2014-06-25 | 2014-08-06 | Trw Ltd | An electric power assisted steering system |
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2019
- 2019-11-06 CN CN201911077783.2A patent/CN112758172B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3539107A1 (en) * | 1984-11-02 | 1986-05-22 | Honda Motor Co Ltd | MOTOR DRIVEN SERVO DEVICE |
| CN201989842U (en) * | 2011-03-25 | 2011-09-28 | 比亚迪股份有限公司 | Steering column power assisting mechanism |
| CN104210544A (en) * | 2013-05-29 | 2014-12-17 | 爱信精机株式会社 | Rear wheel steering apparatus for vehicle |
| CN105599807A (en) * | 2014-11-19 | 2016-05-25 | 日立金属株式会社 | Torque steering angle sensor |
| DE102018202052A1 (en) * | 2017-02-10 | 2018-08-16 | Denso Corporation | Rotation sensing device |
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