KR102247313B1 - Electric power steering system - Google Patents

Abstract

An electric power steering system comprises a housing, a ball screw, a motor, an angle sensor, and a calculation unit. The ball screw includes a nut and a screw. The motor is installed inside the housing and connected to the nut, the motor includes a bushing and a metal part, the metal part is fixedly installed on the bushing, and the metal part includes a center part, a first wing part, and a second wing part. The angle sensor is installed in the housing and fixed to the housing, the angle sensor includes a first sensing unit and a second sensing unit, the first sensing unit is provided with a first through hole, and the second sensing unit is provided with a second through hole. The calculation unit is electrically connected to the first sensing unit and the second sensing unit. The outer diameter of the central portion is smaller than each of the diameters of the first through hole and the second through hole. The present invention can effectively reduce the number of parts and required volume during assembly to enhance convenience.

Description

Electric power steering system {ELECTRIC POWER STEERING SYSTEM}

The present invention relates to an electric power steering system, and more particularly, to an electric power steering system capable of calculating the axial position of a screw by an angle sensor installed in a motor.

Electric Power Steering (EPS) system is a power steering system that provides auxiliary torque by a motor. It is mainly composed of units such as EPS motor, sensor, reduction mechanism, and controller, and largely depending on the mounting position of the EPS motor. It can be divided into type electric power steering (also called Column EPS, C-EPS), pinion type electric power steering (also called Pinion EPS, P-EPS) and rack type electric power steering (also called Rack EPS, R-EPS). In addition, the rack type EPS is divided into a direct-drive type EPS and an indirect-drive type EPS according to a method in which the EPS motor drives the rack or screw of the reduction mechanism. Compared to the conventional hydraulic power steering system, the electric power steering system adjusts the speed of the motor when the vehicle speed changes to provide optimized steering assistance, while simultaneously considering convenience at low speed and stability at high speed, and also oil pump. , Since parts such as hydraulic oil pipes are reduced, it is easy to combine with various vehicle models, and in recent years, it has become a major research subject and is widely applied.

In an electric power steering system, it is an important task to determine the absolute angle that changes the direction of the vehicle body. To this end, Chinese Patent Publication No. CN 103171616 B, has a first rotor connected to the input shaft, a second rotor connected to the output shaft, a first angular element measuring the absolute angle of the first rotor, and the relative of the first rotor. It includes a second angle element and a third angle element for measuring an angle, and an electronic control unit, wherein the electronic control unit obtains a reference angle according to the absolute angle and the relative angle, and determines the relative angle of the second angle element and the third angle element. An electric power steering system has been disclosed, which is tracked and accumulated to obtain a first absolute angle and a second absolute angle, and then additionally calculates an absolute angle at the time of steering a vehicle body according to the first and second absolute angles.

In addition, Chinese Patent Publication No. CN 106068219 B also includes a steering shaft, a torque sensor installed on the steering shaft to measure the torque of the steering wheel, and an angle sensor installed on the motor. An electric power steering apparatus with a steering angle detection device connected by a vernier algorithm and a tracking algorithm to calculate a steering angle of a vehicle body has been disclosed.

However, with the introduction of Advanced Driver Assistance System (ADAS) and unmanned autonomous driving technology, the steering wheel and steering column have become increasingly unnecessary parts, and more and more developers are trying to reduce the volume of the instrument and reduce costs. , In the electric power steering system, the input shaft assembly and the torque sensor were removed to switch to control by electrical connection. In this case, how to obtain the absolute angle to change the direction of the vehicle body or the position of the output shaft (screw) is a problem to be solved. Has emerged again. In addition, in order to fit into various vehicle models, developers do their best to reduce the number of elements of the reduction mechanism and powertrain, and the position of the steering angle or output shaft of the vehicle body due to the accumulation of errors such as aging of elements or interference and spacing between elements. So as not to affect the reliability of calculating. However, in all of the above patent guns, a steering wheel and a steering column must be installed, and a sensor for measuring a steering angle must be installed in the steering column, so the housing for installing the steering column must have a sensor installation space in advance. However, the overall system has a disadvantage that the volume is too large, and cannot be applied to various vehicle models. In addition, the electric power steering apparatus of the above-described patents has a more complicated assembly process due to the assembly structure and mutual arrangement of the steering column and the sensor during assembly, resulting in lower assembly convenience and increased assembly time, thereby further increasing production cost.

The present invention provides an electric power steering system capable of calculating the position of a screw in the axial direction by an angle sensor installed in a motor, effectively reducing the number of elements, and improving assembly convenience by reducing the volume required for assembly. .

The electric power steering system of the present invention includes a housing, a ball screw, a motor, an angle sensor, and a calculation unit. The ball screw includes a nut and a screw, and moves the screw in the axial direction when the nut rotates. The motor is installed inside the housing and connected to the nut, the motor rotates the nut, the motor includes a bushing and metal parts, the bushing is installed on the screw and moves with the nut, and the metal parts are fixedly installed on the bushing. , The metal part includes a central portion, a first wing portion and a second wing portion, and the first wing portion and the second wing portion are installed on the outer circumferential surface of the central portion. The angle sensor is installed inside the housing and fixed to the housing, the angle sensor includes a first detection unit and a second detection unit, the first detection unit is provided with a first through hole and corresponds to the first wing, The second detection unit is provided with a second through hole and corresponds to the second wing portion. The calculation unit is electrically connected to the first detection unit and the second detection unit. Since the outer diameter of the center is smaller than the diameter of the first through hole and the outer diameter of the center is smaller than the diameter of the second through hole, the center is inserted into the first through hole and the second through hole. When the electric power steering system is operated, the first detection unit and the second detection unit detect the rotation angle of the motor and output the first detection signal and the second detection signal to the calculation unit, respectively, and the calculation unit is the first detection signal and the second detection unit. The position of the screw in the axial direction is calculated according to the detection signal.

1 is a schematic diagram of an appearance of an electric power steering system according to an embodiment of the present invention.
2 is a cross-sectional view of the electric power steering system of FIG. 1 in the axial direction.
3 is a schematic diagram of an internal device after a part of the housing of the electric power steering system of FIG. 1 is removed.
4 is a schematic diagram of a first sensing unit, a second sensing unit, a first metal member, and a second metal member of FIG. 3.
5 is an axial cross-sectional view of an electric power steering system according to another embodiment of the present invention.
6 is a schematic diagram of an internal device after a part of the housing of the electric power steering system of FIG. 5 is removed.
7 is a schematic diagram of an angle sensor and a metal part of FIG. 6.
8 is a flowchart illustrating a method of calculating a screw position according to another embodiment of the present invention.
9 is a schematic diagram of a first detection signal and a second detection signal respectively corresponding to the first detection unit and the second detection unit of FIG. 8.
10 is a schematic diagram of a first detection signal and a second detection signal and a target angle of FIG. 9.
11 is a schematic diagram of a difference value after subtracting the first detection signal and the second detection signal of FIG. 9.
12 is a schematic diagram comparing a positive number of a difference value of FIG. 11 and a total rotation angle.

With respect to the above-described technical content and other technical content, features, and effects of the present invention, it will be described clearly through the detailed description of the preferred embodiment incorporating the following drawings. Directional terms such as up, down, left, right, front or back mentioned in the examples below are only directions with reference to the drawings. Accordingly, the directional terms used are for illustrative purposes only and are not intended to further limit the present invention. In addition, in each of the examples below, the same or similar elements will use the same or similar reference numerals.

1 to 3, FIG. 1 is an external schematic diagram of an electric power steering system 100 according to an embodiment of the present invention, and FIG. 2 is an axial cross-sectional view of the electric power steering system 100 of FIG. 1. , FIG. 3 is a schematic diagram of an internal element after a part of the housing 110 of the electric power steering system 100 of FIG. 1 is removed, and the internal element in FIG. 3 is an exploded state. The electric power steering system 100 of this embodiment includes a housing 110, a ball screw 120, a motor 130, an angle sensor 140, and a calculation unit 160, and the ball screw 120 includes a nut ( 122) and a screw 124, and moves the screw 124 in the axial direction when the nut 122 rotates. The motor 130 is installed inside the housing 110 and connected to the nut 122, and the motor 130 rotates the nut 122. The angle sensor 140 is installed inside the housing 110 and fixed to the housing 110, and the angle sensor 140 includes a first detection unit 142 and a second detection unit 144, and a calculation unit 160 is electrically connected to the first sensing unit 142 and the second sensing unit 144.

Specifically, the screw 124 is an output shaft connected to a wheel of a vehicle, and the electric power steering system 100 further includes an input shaft 170 connected to the steering wheel to provide steering torque, and the input shaft 170 and the screw (124) are connected to each other through the rack portion 126 of the ball screw 120 is engaged. For example, the input shaft 170 may be fitted to the pinion structure, and may be coupled to the rack unit 126 through the toothed structure of the pinion. In addition, the electric power steering system 100 may determine an absolute angle for changing the direction of the vehicle body by changing the position of the corresponding output shaft in the axial direction A. Specifically, the nut 122 is screwed to the screw 124 by a plurality of rollers (not shown), and when the nut 122 is rotated, the screw 124 in the axial direction (A) is The movement is promoted, and the operation principle of the ball screw 120 is a prior art, so a description thereof will be omitted.

In this embodiment, the motor 130 includes a stator 131, a rotor 132, a bushing 133 and a metal part 136, and the stator 131 is fixed to the housing 110, and the bushing 133 is installed on the screw 124 and moves together with the nut 122, the metal part 136 is fixedly installed on the bushing 133, the metal part 136 is the first metal member 134 and Including a second metal member 135, the rotor 132, the bushing 133, the metal parts 136, and the nut 122 are installed coaxially to rotate synchronously, and the stator 131, the rotor 132 ), the bushing 133 and the metal part 136 are all installed inside the housing 110. When the electric power steering system 100 is activated, the rotor 132 rotates with respect to the stator 131 while rotating the bushing 133 and the nut 122 together, so that the screw 124 in the axial direction (A) It promotes the movement of the vehicle to achieve the effect of changing the direction of the vehicle body.

In this embodiment, the motor 130 is a hollow torque motor, and since the shaft center portion is hollow, it is possible to directly rotate the nut 122 through the rotor 132, so that there is no need for a reduction mechanism, due to gear shifting. Reduced wear and power loss. In addition, the screw 124 is installed directly through the rotor 132, the bushing 133, and the nut 122, and the rotor 132 and the nut 122 are connected coaxially and rotate synchronously, so that the nut 122 ) Improves the stability when rotating, and since the angle sensor 140 is installed inside the housing 110, there is no need to separately install the angle sensor on the input shaft 170, and the required cost can be greatly reduced, Furthermore, since the installation of the input shaft 170 can be omitted, there is a greater development potential in an autonomous vehicle.

2 to 4, FIG. 4 is a schematic diagram of a first detection unit 142, a second detection unit 144, a first metal member 134, and a second metal member 135 of FIG. 3. In this embodiment, the metal part 136 includes a first metal member 134 and a second metal member 135, and the first metal member 134 and the second metal member 135 are bushings 133 It is fixedly installed on. Specifically, the bushing 133 is provided with a first portion (133a) and a second portion (133b), the outer diameter (D1) of the first portion (133a) is smaller than the outer diameter (D2) of the second portion (133b). The first metal member 134 and the second metal member 135 are stacked along the axial direction A and fixedly installed on the second part 133b through at least one locking member 137, and the first The metal member 134 and the second metal member 135 are located outside the first portion 133a in the radial direction. More specifically, the number of the locking member 137 may be plural, the locking member 137 may be a screw, the first metal member 134 is provided with a plurality of through holes 134c, and the second metal The member 135 is provided with a plurality of through holes 135c, and a plurality of screw holes (not shown) in the cross section of the second portion 133b facing the first metal member 134 and the second metal member 135 Is installed, the number of through-holes 134c, through-holes 135c, and screw holes may correspond to the number of locking members 137. Accordingly, the locking member 137 is inserted through the through hole 134c and the through hole 135c and locked into the screw hole of the second part 133b, while the first metal member 134 and the second metal member ( 135) can be fixed to the bushing 133 to rotate synchronously with the bushing 133 and the nut 122, regardless of the axial direction (A) or the radial direction of the screw 124, the first metal member ( The volume occupied by the motor 130 may be reduced by minimizing all portions of the 134 and the second metal member 135 exceeding the bushing 133. In addition, in FIG. 2, only a part of the locking member 137 is shown for a visual relationship, and in FIG. 3, only two locking members 137 are shown for simplicity of the drawing, and the remaining locking members 137 are omitted. The first metal member 134 includes a first central portion 134a and a plurality of first wing portions 134b, wherein the number of the first wing portions 134b is 5, and the second metal member ( 135) includes a second central portion (135a) and a second wing portion (135b), the plurality of first wing portions (134b) are spaced apart at the same angle and connected to the outer peripheral surface (134d) of the first central portion (134a) And, the second wing portion (135b) forms a fan shape and is connected to the outer peripheral surface (135d) of the second central portion (135a).

The angle sensor 140 includes a first detection unit 142 and a second detection unit 144, and the first detection unit 142 is provided with a first through hole 143 and a first wing part 134b And, the second detection unit 144 is provided with a second through hole 145 and corresponds to the second wing portion 135b, and the outer diameter D3 of the first central portion 134a is the first detection unit ( It is smaller than the aperture H1 of the first through hole 143 of 142, and the outer diameter D4 of the second central portion 135a is the aperture H2 of the second through hole 145 of the second detection unit 144 Since it is smaller, the first central portion 134a and the second central portion 135a are in the first through hole 143 of the first sensing unit 142 and the second through hole 145 of the second sensing unit 144. Each should be inserted and installed. In addition, when the first metal member 134 and the second metal member 135 are assembled, the first central portion 134a and the second central portion 135a are connected to form the central portion (reference numeral not shown). Can be formed. In this embodiment, the centrifugal angle formed by the axial center of the second wing portion 135b and the second central portion 135a is 180 degrees, and the plurality of first wing portions 134b are spaced apart from each other at the same angle, and the first wing When the part 134b and the second wing part 135b are designed to have different separation angles, the first detection unit 142 and the second detection unit 144 can measure detection signals of two different measurement ranges. Thus, it is advantageous for calculation by the Vernier Algorithm and the Angle Follower Algorithm of the calculation unit 160, and specific details related to the algorithm will be described later.

When assembling the motor 130, the first detection unit 142 corresponds to the first metal member 134, the second detection unit 144 corresponds to the second metal member 135, and the first center ( 134a) and the second central portion 135a are respectively inserted and installed in the first through hole 143 of the first detection unit 142 and the second through hole 145 of the second detection unit 144. Through this arrangement, when the first metal member 134 and the second metal member 135 rotate synchronously with the nut 122, the first detection unit 142 is The rotation angle of the member 134 may be sensed to output the first detection signal S1, and the second detection unit 144 may determine the rotation angle of the second metal member 135 by a magnetic signal or a light reflection signal. It may sense and output a second detection signal (S2), and the calculation unit 160 may detect the screw 124 in the axial direction (A) according to the first detection signal (S1) and the second detection signal (S2). By calculating the position and knowing the correct tire angle, the vehicle will change direction accurately. In addition, the first central portion 134a and the second central portion 135a are respectively inserted into the first through hole 143 of the first sensing unit 142 and the second through hole 145 of the second sensing unit 144 Since it is installed, it allows the elements to be more tightly coupled, further reducing the volume of the entire electric power steering system 100.

Further, in this embodiment, the maximum outer diameter D5 of the first metal member 134 is smaller than the diameter H2 of the second through hole 145. Therefore, when assembling the electric power steering system 100, first, the first detection unit 142 and the second detection unit 144 are fixed in the housing 110, and then the first metal member 134 and the second metal When the member 135 is fitted to the first part 133a and locked to the second part 133b along the axial direction (A), the first part 133a of the bushing 133 is continuously attached to the first metal. Together with the member 134, the second through hole 145 of the second detection unit 144 may be penetrated, and the maximum outer diameter D5 of the first metal member 134 is the diameter of the second through hole 145 Since it is smaller than (H2), the first metal member 134 easily penetrates the second through hole 145 and is installed between the first detection unit 142 and the second detection unit 144, and the first detection unit By making 142 and the second detection unit 144 correspond to the first metal member 134 and the second metal member 135, respectively, the purpose of facilitating installation is reached.

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, and FIG. 6 is a view of the electric power steering system 100 ′ of FIG. 5. It is a schematic diagram of the internal element after a part of the housing 110 is removed, the internal element in FIG. 6 is in an exploded state, and FIG. 7 is a schematic diagram of the angle sensor 140 ′ and the metal part 136 ′ of FIG. 6. In the electric power steering system 100' of this embodiment, the metal part 136' is fixedly installed on the bushing 133', and the metal part 136' is a central part 136a, a plurality of first wing parts 136b. ) And a second wing portion (136c), the first wing portion (136b) and the second wing portion (136c) are installed on the outer peripheral surface (136d) of the central portion (136a), specifically, the first wing portion ( The number of 136b) is 5, and the plurality of first wing portions 136b are installed at the same angle on the outer peripheral surface 136d of the central portion 136a, and the second wing portion 136c forms a fan shape and the central portion It forms a centrifugal angle of 180 degrees with the axial center of (136a), the second wing portion (136c) is located outside the radial direction of the first wing portion (136b), the inner radial direction of the second wing portion (136c) is partially It is connected to the outer side in the radial direction of the 1 wing part 136b. That is, the first wing portion 136b is located between the central portion 136a and the second wing portion 136c and is connected to the central portion 136a and the second wing portion 136c.

The angle sensor 140 ′ includes a first detection unit 142 ′, a second detection unit 144 ′, and a plurality of connection parts 147, and the number of the connection parts 147 is 4, and the first 1 The detection unit 142' is provided with a first through hole 143' and corresponds to the first wing portion 136b, and the second detection unit 144' is provided with a second through hole 145'. Corresponding to the second wing portion 136c, the first detection unit 142' is installed in the second through hole 145', and the connection portion 147 is the first detection unit 142' and the second detection unit Connect (144'). That is, the second through hole 145 ′ includes the first through hole 143 ′. The outer diameter (D6) of the center (136a) is smaller than the diameter (H1) of the first through hole (143'), the outer diameter (D6) of the center (136a) is less than the diameter (H2) of the second through hole (145') Since it is small, the central portion 136a is inserted and installed in the first through hole 143 ′ and the second through hole 145 ′. The main difference between the electric power steering system 100' and the electric power steering system 100 described above is that the angle sensor 140 of the electric power steering system 100 has two independent elements, the first detection unit 142 and the first. 2 The sensing unit 144 is included, and the angle sensor 140 ′ of the electric power steering system 100 ′ is a single element, and the metal part 136 of the electric power steering system 100 is a second independent element. The metal part 136 ′ of the electric power steering system 100 ′ including the first metal member 134 and the second metal member 135 is a single element. Accordingly, the overall structure can be simplified, and the situation in which interference occurs when assembling the angle sensor 140 ′ and the metal part 136 ′ is reduced.

When assembling the motor 130 ′, the central portion 136a of the metal part 136 ′ is inserted and installed in the first through hole 143 ′, and the first sensing unit 142 ′ and the second sensing unit 144 ′ ) Corresponds to the first wing portion 136b and the second wing portion 136c, respectively, so that the first detection unit 142 ′ and the second detection unit 144 ′ correspond to the first wing portion 136b and the second wing portion 136b. Each of the rotation angles of the wing portion 136c is sensed so that the first detection signal S1 and the second detection signal S2 can be respectively output. In this embodiment, the second wing portion (136c) forms a fan shape and forms a centrifugal angle of 180 degrees with the axial center of the center portion (136a), and the plurality of first wing portions (136b) are spaced apart from each other at the same angle, and the second wing When the part 136c and the first wing part 136b are designed to have different separation angles, the first detection unit 142' and the second detection unit 144' measure detection signals of two different measurement ranges. , Allows the calculation unit 160 to proceed with calculation by an algorithm. With respect to the motor 130, the motor 130 ′ of this embodiment includes an axial gap between the first sensing unit 142 and the second sensing unit 144 and the first metal member 134 and the second metal member ( 135), the space required for the motor 130' in the entire electric power steering system 100' may be further reduced.

Further, similar to the electric power steering system 100, in this embodiment, the bushing 133' is provided with a first portion 133a' and a second portion 133b', and the first portion 133a' The outer diameter (D1) of the second portion (133b') is smaller than the outer diameter (D2), the metal part (136') is fixedly installed to the second portion (133b') through a locking member (not shown), The component 136' is located radially outward of the first portion 133a'. Specifically, the metal part 136 ′ may be provided with a plurality of through holes 136 e so that the locking member is penetrated, and the locking member is locked at the end face of the second part 133 b ′ toward the metal part 136 ′. A plurality of screw holes (not shown) may be installed, and the related description of FIG. 3 may be referred to in relation to the locking member. Accordingly, in the electric power steering system 100 ′, the volume occupied by the motor 130 ′ may be reduced by minimizing the portion exceeding the bushing 133 ′ of the metal part 136 ′.

In addition, since the outer diameter D6 of the center portion 136a of the metal part 136' is smaller than the diameter H1 of the first through hole 143', when assembling the electric power steering system 100', first After fixing the angle sensor 140 ′ formed of the first sensing unit 142 ′ and the second sensing unit 144 ′ in the housing 110, the first part 133a ′ of the bushing 133 ′ is metal By penetrating through the first through hole 143 ′ together with the central part 136a of the part 136 ′, the first sensing unit 142 ′ and the second sensing unit 144 ′ are formed with the first wing part 136b and By making the second wing portions 136c correspond to each other, the purpose of facilitating installation is reached.

Referring to FIG. 8, FIG. 8 is a flowchart illustrating a method of calculating a screw position according to another embodiment of the present invention. Here, the electric power steering system 100 will be described, and in this embodiment, a first detection signal output by the first detection unit 142 and the second detection unit 144 installed on the motor 130 The position of the screw 124 in the axial direction A is calculated through (S1) and the second detection signal S2, and each step will be described in detail below. First, when the electric power steering system 100 is operated (step S01), and the electric power steering system 100 is operated, the first detection unit 142 and the second detection unit 144 are By detecting the rotation angle of the 134 and the second metal member 135, the rotation angle θ of the rotor 132 of the motor 130 is measured to detect the first detection signal S1 and the second detection. Each of the signals S2 is obtained, and at this time, the first detection unit 142 and the second detection unit 144 output the first detection signal S1 and the second detection signal S2 to the calculation unit 160, respectively, and (Step S02), the calculation unit 160 obtains a position through a first algorithm according to the difference value d between the first detection signal S1 and the second detection signal S2 (step S03). In this embodiment, the first algorithm is a vernier algorithm, and an accurate measurement result can be calculated by the difference value of the detection signals of two different measurement ranges.

9 to 12, FIG. 9 is a diagram of a first detection signal S1 and a second detection signal S2 corresponding to the first detection unit 142 and the second detection unit 144 of FIG. 8, respectively. It is a schematic diagram, and FIG. 10 is a schematic diagram of a first detection signal S2 and a second detection signal S2 and a target angle of FIG. 9, and FIG. 11 is a first detection signal S1 and a second detection signal ( It is a schematic diagram of the difference value after subtracting S2), and FIG. 12 is a schematic diagram comparing the positive number of the difference value in FIG. 11 with the total rotation angle. Specifically, assuming that the total rotation angle range of the input shaft 170 (that is, the total rotation angle of the steering wheel) in the present embodiment is 0 to 9000 degrees, the first detection signal S1 measured by the first detection unit 142 ) Corresponds to the first measurement range R ₁ , in this embodiment, the first measurement range R ₁ is 125 degrees, and the second detection signal S2 measured by the second detection unit 144 is Corresponding to the second measurement range (R ₂ ), and in this embodiment, the second measurement range (R ₂ ) is 360 degrees. When the measured target value exceeds the individual measurement range, the first detection signal S1 or the second detection signal S2 will increase again from 0 degrees. Specifically, in the vernier algorithm, since the first measurement range R ₁ must be different from the second measurement range R ₂ , the difference value d can be smoothly obtained only when measuring the same rotation angle. .

Referring to FIG. 10, in this embodiment, assuming that the actual moving distance of the screw 124 is 36 mm, and the rotation angle θ of the nut 122 is 1620 degrees, the rotor 132 and the nut 122 are coaxial. Since it is connected and rotates synchronously, the rotation angle θ of the rotor 132 of the motor 130 is the rotation angle of the nut 122, and the corresponding first detection signal S1 is 120 degrees, 2 The detection signal (S2) is 180 degrees, the difference value (d) is (S1)-(S2) = -60 degrees, and the difference value (d) is negative, so the second measurement range (R ₂ ) is added or The comparison through FIG. 11 should be made to be a positive number d _pos = -60 + R ₂ = 300 of the difference value. After obtaining the positive number d _pos of the difference value, the angle correction amount can be obtained through Table 1 or FIG. 12 below.

Actual rotation angle, positive number of difference value, and comparison relationship of angle correction amount Actual rotation angle
Lower limit Actual rotation angle
maximum Positive difference Angle correction amount 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
(skip)

(skip)

(skip)
(skip) 8500 8624 140 8500 8625 8749 15 8625 8750 8874 250 8750 8875 8999 125 8875

According to Table 1 or 12, it _{can be seen that there are a total of 72 different positive values d pos} , and at the same time, the total measurement range (9000 degrees) is divided into 72 areas, and the rotation angle of this embodiment is the difference value By the positive number of d _pos = 300 degrees, it can be seen that the actual rotation angle (θ) belongs to the thirteenth area and the angle correction amount is 1500 degrees, so the actual rotation angle (θ) can be obtained through the following equation.

Here, θ _actual is the actual angle at which the nut 122 is rotated, and θ _correction is the angle correction amount. Therefore, the actual rotation angle θ is 1500 + 120 = 1620 degrees, where the angle correction amount can be regarded as the product of the angular amplitude of a single area (125 degrees) and the number of area intervals (13-1 = 12).

θ)에 따라, 제2 알고리즘을 통해 회전각도(θ) 및 스크류(124)의 위치를 갱신한다(단계S06). 본 실시예에서, 제2 알고리즘은 각도 추적 알고리즘이고, 적분 원리를 이용하여, 시간구간(t)에서의 각도변화량(

θ)을 제1 알고리즘을 통해 얻은 초기 값에 가산하여 회전각도(θ)를 갱신한다. 또한, 제1 감지 신호(S1) 또는 제2 감지 신호(S2)가 비정상이거나, 또는 전동식 파워 스티어링 시스템(100)이 재가동되면, 산출부(160)는 제1 감지 유닛(142) 및 제2 감지 유닛(144)에 의해 출력된 제1 감지 신호(S1) 및 제2 감지 신호(S2)를 다시 판독하고, 상술한 단계를 반복한다. After obtaining the actual rotation angle (θ) of the nut 122 through the above-described first algorithm, the position of the screw 124 in the axial direction (A) can be calculated through a linear-angle ratio. In this case, the calculation unit 160 may verify the calculation result (step S04), and check whether there is an abnormal phenomenon such as a clear wave or exceeding the measurement range of the detection signal. If both the first detection signal S1 and the second detection signal S2 are reliable and not obviously abnormal (step S05), the calculation unit 160 uses the obtained rotation angle θ as an initial value, The amount of change in time interval (t) and rotation angle (θ) (

According to θ), the rotation angle θ and the position of the screw 124 are updated through a second algorithm (step S06). In this embodiment, the second algorithm is an angle tracking algorithm, and using the integration principle, the angle change amount (

The rotation angle θ is updated by adding θ) to the initial value obtained through the first algorithm. In addition, when the first detection signal S1 or the second detection signal S2 is abnormal, or the electric power steering system 100 is restarted, the calculation unit 160 performs the first detection unit 142 and the second detection. The first detection signal S1 and the second detection signal S2 output by the unit 144 are read again, and the above-described steps are repeated.

In conclusion, since the electric power steering system of the present invention can calculate the axial position of the screw by obtaining the first detection signal and the second detection signal by the first detection unit and the second detection unit installed in the housing, the input shaft is It can solve the problem that it is difficult to know the screw location when there is no. In addition, since the input shaft and the sensing unit installed on the input shaft can be omitted, the volume and cost occupied by the device can be greatly reduced, and it is possible to cope with various vehicle models, thereby improving the function and convenience of the system.

The above description is only a preferred embodiment of the present invention, and all equivalent changes or modifications made according to the claims of the present invention should be included in the scope of the present invention.

: 변화량 100, 100': electric power steering system
110: housing
120: ball screw
122: nut
124: screw
126: rack unit
130, 130': motor
131: stator
132: rotor
133, 133': bushing
133a, 133a': first part
133b, 133b': second part
134: first metal member
134a: first center
134b, 136b: first wing portion
134c, 135c, 136e: through hole
134d, 135d, 136d: outer peripheral surface
135: second metal member
135a: second center
135b, 136c: second wing
136, 136': metal member
136a: central
137: locking member
140, 140': angle sensor
142, 142': first detection unit
143, 143': first through hole
144, 144': second detection unit
145, 145': second through hole
147: connection
160: calculation unit
170: input shaft
A: axial direction
d: difference value
d _pos : positive number of difference value
D1, D2, D3, D4, D6: outer diameter
D5: maximum outer diameter
H1, H2: Caliber
R ₁ : 1st measurement range
R ₂ : 2nd measurement range
S1: first detection signal
S2: second detection signal
S01, S02, S03, S04, S05, S06: Step
t: time interval
θ: rotation angle
θ _actual : actual angle
θ _correction : angle correction amount

: Change amount

Claims (3)

In the electric power steering system including a housing, a ball screw, a motor, an angle sensor, and a calculation unit,
The ball screw includes a nut and a screw, and moves the screw in the axial direction when the nut rotates,
The motor is installed in the housing and connected to the nut, and the motor rotates the nut,
The motor,
A bushing installed on the screw and moving together with the nut; And
It is fixedly installed on the bushing, and includes a central portion, a first wing portion and a second wing portion, the first wing portion and the second wing portion is a metal part installed on the outer peripheral surface of the center;
The angle sensor is installed in the housing and fixed to the housing,
The angle sensor,
A first detection unit having a first through hole and corresponding to the first wing portion;
A second detection unit having a second through hole and corresponding to the second wing portion; And
Includes; a calculation unit electrically connected to the first detection unit and the second detection unit,
Since the outer diameter of the central portion is smaller than the diameter of the first through hole, the outer diameter of the central portion is smaller than the diameter of the second through hole, the central portion is inserted and installed in the first through hole and the second through hole, ;
When the electric power steering system is operated, the first detection unit and the second detection unit sense the rotation angle of the motor and output a first detection signal and a second detection signal to the calculation unit, respectively, and the calculation unit Calculating the position of the screw in the axial direction according to the first detection signal and the second detection signal,
Electric power steering system. The method of claim 1,
The metal parts,
It includes a first central portion and the first wing portion, the first wing portion is connected to the outer circumferential surface of the first central portion, the outer diameter of the first central portion is smaller than the diameter of the first through hole, the first central portion A first metal member inserted and installed in the first through hole; And
A second central portion and the second wing portion, wherein the second wing portion is connected to an outer circumferential surface of the second central portion, and an outer diameter of the second central portion is smaller than the diameter of the second through hole, and thus the second central portion Includes; a second metal member inserted and installed in the second through hole
The first central portion and the second central portion are connected to form the central portion, and a maximum outer diameter of the first metal member is smaller than the diameter of the second through hole. The method of claim 1,
The first sensing unit is installed in the second through hole, the angle sensor further includes a connection, and the connection part connects the first sensing unit and the second sensing unit.

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