P-EPS middle and lower shell connecting structure and assembling method thereof

Abstract

The invention discloses a P-EPS middle and lower shell connecting structure and an assembling method thereof, and belongs to the technical field of P-EPS steering gears of steering systems for automobiles. A P-EPS middle and lower shell connecting structure comprises a second lower shell and a second middle shell, and further comprises a lower mounting hole and an upper mounting hole which are formed in the second lower shell respectively, a bearing mounting hole is formed in the second middle shell, a second needle bearing is fixedly mounted in the lower mounting hole, and a second four-point bearing is fixedly mounted in the bearing mounting hole; a second gear shaft and a first middle journal; the middle shell is designed into an annular shape with good rigidity and strength, the bearing outer ring cannot generate conical deformation, so that the two sides of the bearing track generate symmetrical shrinkage deformation, the abrasion of the bearing track and the steel balls is reduced, the abnormal sound of the four-point bearing cannot be caused, the service life can be prolonged, meanwhile, the pressing rivet qualification rate is high through verification, the assembly efficiency can be improved, and the production cost is reduced. The production cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of a P-EPS steering gear for a steering system of an automobile, and in particular to a P-EPS middle and lower shell connection structure and an assembly method thereof. Background Art

[0002] P-EPS, also known as the pinion power steering system EPS, places the power-assist motor on the pinion of the steering gear. It has a compact structure and is suitable for small cars with small power-assist requirements. The lower housing structure in P-EPS is an important component of the pinion power-assist system, which is usually used to protect internal components and provide structural support.

[0003] Depend on Figure 1 It can be seen that the P-EPS middle and lower housing structure is popular in the prior art, and is mainly composed of a first lower housing (1), a first needle bearing (2), a first gear shaft (3), a gear shaft retaining ring (4), a first four-point bearing (5), a first bolt (6), a first middle housing (7), a first bearing (8), a first partition (9), a first sensor body (10), a first sensor body (11), a first stop pin (12), a first input shaft (13), a first torsion bar (14), a first sliding bearing (15), a first O-ring (16) and other components. The middle and lower housing connection structure is that half of the first four-point bearing (5) is pressed into the mounting hole of the first middle housing (7) by interference fit, and the other half is installed in the mounting hole of the first lower housing (1) and is tightened on the end face of the first lower housing (1) by the first bolt (6). In order to axially press the first four-point bearing (5), a gap will appear at the connection between the middle and lower housings. Its main disadvantages are as follows:

[0004] 1. The first middle housing (7) has insufficient rigidity at the mounting hole for mounting the first four-point bearing (5). When the axial load on the first gear shaft (3) is at its maximum, the first middle housing (7) will deform elastically, causing the gear shaft to move axially and generate abnormal noise.

[0005] Second, the first middle housing (7) must completely compress the first four-point bearing (5), and the minimum thickness of the first four-point bearing (5) must be greater than the sum of the bearing mounting holes of the first middle housing (7) and the first lower housing (1). A gap will inevitably appear at the connection between the middle and lower housings, causing the first middle housing (7) to produce axial deformation;

[0006] 3. The first four-point bearing (5) is fitted with the first middle housing (7) by interference, and with the first lower housing (1) by clearance, so that the outer ring of the bearing produces a conical deformation, thereby causing asymmetric deformation on both sides of the bearing track, accelerating the wear of the bearing track and the steel ball, causing abnormal noise of the first four-point bearing (5) and shortening its life;

[0007] Fourth, the first gear shaft (3) is axially locked with the first four-point bearing (5) by means of a gear shaft clamp ring (4) through riveting. It has been verified through mass production that the qualified rate of riveting is not high, and a large number of returned workpieces are produced, which affects the assembly progress and cost. Summary of the invention

[0008] The purpose of the present invention is to solve the problem of gaps appearing at the connection of the middle and lower shells in the prior art, and to propose a P-EPS middle and lower shell connection structure and an assembly method thereof.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A P-EPS middle and lower shell connection structure includes a second lower shell and a second middle shell, and also includes: a lower mounting hole and an upper mounting hole, which are respectively opened inside the second lower shell, wherein a bearing mounting hole is opened in the second middle shell, a second needle bearing is fixedly installed in the lower mounting hole, and a second four-point bearing is fixedly installed in the bearing mounting hole; a second gear shaft and a first middle shaft neck, wherein the bottom of the second needle bearing is fixedly connected to the upper mounting hole, a bearing inner hole 2 is opened on the second four-point bearing, and the second gear shaft and the first middle shaft neck are respectively fixedly connected to the bearing inner hole 2, and the first middle shaft neck axially locks the second four-point bearing.

[0011] In order to improve the connection effect of the second middle shell, preferably, a lower end surface is provided on the inner wall of the second middle shell, an upper end surface is provided on the second lower shell, one side of the second needle roller bearing is fitted with the lower end surface, and the other side of the second needle roller bearing is fixedly connected to the upper end surface by a second bolt, and the two planes at the connection are fitted with each other.

[0012] In order to prevent the middle housing from axial deformation, preferably, the second middle housing is annular, and the second middle housing and the second four-point bearing are interference fit.

[0013] In order to improve the connection stability of the gear shaft, further, a second sliding bearing is arranged on the second gear shaft, a second input shaft is arranged on the inner hole of the second sliding bearing, and a second torsion bar is arranged on the inner hole of the second input shaft.

[0014] In order to improve the practicability of the device, preferably, a second sensor body is fixedly connected to the second gear shaft, an upper journal and a first shoulder end face are respectively provided on the second gear shaft, and the second sensor body is respectively against the upper journal and the first shoulder end face.

[0015] Preferably, a second sensor magnetic ring is fixedly connected to the second input shaft, a second middle shaft journal and a second shaft shoulder end face are respectively provided on the second input shaft, and the second sensor magnetic ring abuts against the first middle shaft journal and the second shaft shoulder end face respectively.

[0016] In order to improve the connection effect of the needle roller bearing, preferably, the second needle roller bearing is provided with a bearing inner hole one, the second gear shaft is provided with a lower journal, and the second gear shaft and the lower journal are respectively fixedly connected in the bearing inner hole one.

[0017] In order to prevent excessive deviation between the input shaft and the gear shaft, preferably, the critical values ​​of the left and right rotation angles of the second input shaft relative to the second gear shaft are S1 and S2 respectively, and the difference between S1 and S2 is less than or equal to 30°.

[0018] In order to position the gear shaft, preferably, a positioning outer circle is provided on the second middle housing, and the second gear shaft coincides with the axis of the positioning outer circle.

[0019] A method for connecting and assembling a lower shell of a P-EPS, the operation steps are as follows:

[0020] Step 1: First, press the second four-point bearing into the bearing mounting hole of the second middle housing by interference fit to complete the assembly of the middle housing assembly;

[0021] Step 2: The second housing is designed into a ring shape, and then the positioning outer circle is used for installation and positioning, and the bearing mounting hole is used for installing the four-point bearing;

[0022] Step 3: When assembling the second gear shaft and the second input shaft, apply high-efficiency long-lasting grease to the outer circumferential surface of the second input shaft that matches the inner hole of the second sliding bearing, and apply high-efficiency long-lasting grease to the outer circumferential surface of the second torsion bar that matches the inner hole of the second input shaft;

[0023] Step 4: Install the first middle journal on the second gear shaft into the second inner hole of the second four-point bearing, and then position it with the journal on the second gear shaft, and then axially lock the second four-point bearing with the second gear shaft clamp ring;

[0024] Step 5: Position the second sensor body with the journal on the second gear shaft, and weld the first shaft shoulder end face against the second gear shaft;

[0025] Step 6: Position the second sensor magnetic ring with the second middle journal of the second input shaft, support it with the second shaft shoulder end face, and weld it to the second input shaft;

[0026] Step 7: Press the second needle roller bearing into the lower mounting hole of the second lower housing with interference fit to complete the assembly.

[0027] Compared with the prior art, the present invention provides a P-EPS middle and lower shell connection structure and an assembly method thereof, which has the following beneficial effects:

[0028] 1. The P-EPS middle and lower housing connection structure is pressed into the middle housing through a four-point bearing interference fit, positioned by the positioning outer circle of the middle housing, supported by the lower end face, installed in the upper mounting hole of the lower housing, and tightened on the upper end face of the lower housing by bolts. The two planes of this connection are tightly attached; at the same time, the lower journal of the gear shaft is installed in the bearing inner hole of the needle bearing;

[0029] 2. The P-EPS middle and lower shell connection structure, by designing the middle shell into a ring with good rigidity and strength, will not cause elastic deformation of the middle shell, and will not cause axial movement of the gear shaft to produce abnormal noise;

[0030] 3. The connection structure of the middle and lower shells of the P-EPS adopts interference fit only with the middle shell through the four-point bearing, and tightens the bearing gland to axially lock the four-point bearing through threaded connection. In addition, the middle shell is designed as a ring with good rigidity and strength, which will not cause the outer ring of the bearing to produce conical deformation, so that the two sides of the bearing track will produce symmetrical shrinkage deformation, reduce the wear of the bearing track and steel balls, will not cause abnormal noise of the four-point bearing, and can extend the service life;

[0031] 4. In the connection structure of the lower shell in the P-EPS, the gear shaft is riveted to axially lock the four-point bearing through the gear shaft clamp ring. It has been verified that the riveting qualification rate is high, which can improve assembly efficiency and reduce production costs.

[0032] The parts not involved in the device are the same as the prior art or can be implemented by the prior art. The middle shell in the present invention is designed to be a ring with good rigidity and strength, which will not cause conical deformation of the outer ring of the bearing, thereby causing symmetrical shrinkage deformation on both sides of the bearing track, reducing the wear of the bearing track and the steel ball, and will not cause abnormal noise of the four-point bearing, and can extend the service life. At the same time, it has been verified that the pass rate of riveting is high, which can improve assembly efficiency and reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A diagram showing the structure of the lower shell connection in a P-EPS proposed in the prior art;

[0034] Figure 2 This is a diagram showing the connection structure of the lower shell body proposed by the present invention;

[0035] Figure 3 This is a diagram showing the structure of the middle shell body proposed by the present invention;

[0036] Figure 4 This is a diagram of the input shaft gear shaft combination structure proposed by the present invention;

[0037] Figure 5 This is a schematic diagram of the input shaft and gear shaft combination press riveting proposed by the present invention;

[0038] Figure 6This is a schematic diagram of laser welding of the input shaft gear shaft combination sensor proposed by the present invention;

[0039] Figure 7 This is a diagram of the lower shell assembly structure proposed by the present invention.

[0040] In the figure: 1, first lower housing; 2, first needle bearing; 3, first gear shaft; 4, gear shaft retaining ring 1; 5, first four-point bearing; 6, first bolt; 7, first middle housing; 8, first bearing; 9, first partition; 10, first sensor body; 11, first sensor magnetic ring; 12, first stop pin; 13, first input shaft; 14, first torsion bar; 15, first sliding bearing; 16, first O-ring; 21, second lower housing; 211, lower mounting hole; 212, upper mounting hole; 213, upper end face; 22, second needle bearing; 221, bearing inner hole 1; 23, second gear shaft; 231, lower journal; 232, first middle journal; 233, first Shoulder end face; 234, upper journal; 24, gear shaft clamp ring two; 25, bearing cover; 26, O-ring one; 27, second four-point bearing; 271, bearing inner hole two; 28, worm gear assembly; 29, second partition; 30, second bearing; 31, second sliding bearing; 32, second torsion bar; 33, O-ring two; 34, rubber plug; 35, second stop pin; 36, second input shaft; 361, second shoulder end face; 362, second middle journal; 37, second sensor magnetic ring; 38, second sensor body; 39, second middle shell; 391, bearing mounting hole; 392, lower end face; 393, positioning outer circle; 40, O-ring three; 41, second bolt. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0042] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0043] Embodiment 1:

[0044] Reference Figure 1A P-EPS middle and lower shell connection structure includes a first lower shell 1, a first needle bearing 2, a first gear shaft 3, a gear shaft clamp ring 4, a first four-point bearing 5, a first bolt 6, a first middle shell 7, a first bearing 8, a first partition 9, a first sensor body 10, a first sensor magnetic ring 11, a first stop pin 12, a first input shaft 13, a first torsion bar 14, a first sliding bearing 15, a first O-ring 16 and other components. The middle and lower shell connection structure is achieved by half of the first four-point bearing 5 being pressed into the mounting hole of the first middle shell 7 through interference, and the other half being installed in the mounting hole of the first lower shell 1 and tightened on the end surface of the first lower shell 1 through the first bolt 6.

[0045] The above is the connection structure of the lower shell in P-EPS in the prior art and is for reference only.

[0046] Embodiment 2:

[0047] Reference Figure 2-Figure 3 In order to improve the connection stability of the middle and lower shells, it includes a second lower shell 21 and a second middle shell 39, and also includes: a lower mounting hole 211 and an upper mounting hole 212, which are respectively opened inside the second lower shell 21, wherein a bearing mounting hole 391 is opened in the second middle shell 39, a second needle roller bearing 22 is fixedly installed in the lower mounting hole 211, and a second four-point bearing 27 is fixedly installed in the bearing mounting hole 391; a second gear shaft 23 and a first middle shaft journal 232, wherein the bottom of the second needle roller bearing 22 is fixedly connected to the upper mounting hole 212, a second bearing inner hole 271 is opened on the second four-point bearing 27, and the second gear shaft 23 and the first middle shaft journal 232 are respectively fixedly connected to the bearing inner hole 271, and the first middle shaft journal 232 axially locks the second four-point bearing 27.

[0048] A lower end surface 392 is provided on the inner wall of the second middle shell 39, and an upper end surface 213 is provided on the second lower shell 21. One side of the second needle roller bearing 22 is in contact with the lower end surface 392, and the other side of the second needle roller bearing 22 is fixedly connected to the upper end surface 213 by a second bolt 41, and the two planes at the connection are in contact with each other.

[0049] The second lower shell 21 has a lower mounting hole 211 , an upper mounting hole 212 and other holes, and the second middle shell 39 has a bearing mounting hole 391 and other holes. First, the second needle roller bearing 22 is pressed into the lower mounting hole 211 of the second lower shell 21 through interference, and the second four-point bearing 27 is pressed into the bearing mounting hole 391 of the second middle shell 39 through interference; the first middle journal 232 on the second gear shaft 23 is installed in the bearing inner hole 271 of the second four-point bearing 27, and the second gear shaft 23 is axially riveted by the gear shaft clamp ring 24, and the second four-point bearing 27 is axially compressed by tightening the bearing cover 25 through threaded connection, and then positioned with the positioning outer circle 393 of the second middle shell 39, the lower end face 392 is supported, and installed in the upper mounting hole 212 of the second lower shell 21, and tightened on the upper end face 213 of the second lower shell 21 by the second bolt 41, and the two planes at this connection are tightly attached; at the same time, the lower journal 231 on the second gear shaft 23 is installed in the bearing inner hole 221 of the second needle roller bearing 22 to complete the connection of the middle and lower shells.

[0050] Figure 3 The connection between the middle and lower shells is mainly composed of: the second four-point bearing 27, the second bearing inner hole 271, the second middle shell 39, the bearing mounting hole 391, the lower end surface 392, and the positioning outer circle 393;

[0051] First, the second four-point bearing 27 is interference-pressed into the bearing mounting hole 391 of the second middle housing 39 to complete the assembly of the middle housing assembly;

[0052] By interference pressing the second four-point bearing 27 into the second middle housing 39, the outer ring of the bearing will not produce conical deformation, thereby causing symmetrical shrinkage deformation on both sides of the bearing track, reducing the wear of the bearing track and the steel ball, preventing abnormal noise from the second four-point bearing 27, and extending the service life.

[0053] The second middle housing 39 is annular, and the second middle housing 39 and the second four-point bearing 27 are interference fit.

[0054] By designing the second middle housing 39 to be annular, not only the axial rigidity and strength of the second middle housing 39 are improved, but also the positioning outer circle 393 can be used for installation and positioning, and the bearing mounting hole 391 can be used for installing a four-point bearing.

[0055] Reference Figure 4 The second input shaft 36 and the second gear shaft 23 assembly are mainly composed of the second gear shaft 23, the lower journal 231, the first middle journal 232, the O-ring 1 26, the worm gear assembly 28, the second partition plate 29, the second bearing 30, the second sliding bearing 31, the second torsion bar 32, the O-ring 2 33, the rubber plug 34, the second stop pin 35, the O-ring 3 40, etc.

[0056] A second sliding bearing 31 is disposed on the second gear shaft 23 , a second input shaft 36 is disposed on the inner hole of the second sliding bearing 31 , and a second torsion bar 32 is disposed on the inner hole of the second input shaft 36 .

[0057] When the second gear shaft 23 and the second input shaft 36 are assembled, a high-efficiency and long-lasting grease is applied to the outer circumferential surface of the second input shaft 36 that matches the inner hole of the second sliding bearing 31, and a high-efficiency and long-lasting grease is applied to the outer circumferential surface of the second torsion bar 32 that matches the inner hole of the second input shaft 36; and when drilling and reaming, the critical values ​​of the left and right rotation angles of the second input shaft 36 relative to the second gear shaft 23 are S1 and S2 respectively, and the difference between S1 and S2 is less than or equal to 30°, and the axial dimension tolerance L+0.15,-0.05 must be ensured at the same time.

[0058] Reference Figure 5 The second gear shaft 23 is fixedly connected with a second sensor body 38 , an upper journal 234 and a first shaft shoulder end face 233 are respectively provided on the second gear shaft 23 , and the second sensor body 38 abuts against the upper journal 234 and the first shaft shoulder end face 233 , respectively.

[0059] First, the first middle journal 232 on the second gear shaft 23 is installed in the bearing inner hole 271 of the second four-point bearing 27, and then the upper journal 234 of the second gear shaft 23 is positioned, and the enlarged first shoulder end face 233 is supported. A special press and riveting tool are used to rivet the gear shaft clamp ring 24 into a conical surface, and axially lock the second four-point bearing 27; in addition, the enlarged first shoulder end face 233 can increase the supporting area, ensure the stability and riveting quality of the gear shaft clamp ring 24 during riveting, improve the riveting qualification rate and extend the life of the tool.

[0060] Reference Figure 6 , first combine the riveted second gear shaft 23, the second input shaft 36 and the second middle housing 39, use a special wrench to tighten the bearing gland 25 through threaded connection to axially lock the second four-point bearing 27, and the second middle housing 39 is designed to be a ring with good rigidity and strength, so that the second gear shaft 23 will not produce axial movement and abnormal sound when the gear rack is meshed;

[0061] The second input shaft 36 is fixedly connected with a second sensor magnetic ring 37 . The second input shaft 36 is provided with a second middle journal 362 and a second shaft shoulder end face 361 . The second sensor magnetic ring 37 abuts against the first middle journal 232 and the second shaft shoulder end face 361 .

[0062] Then, the second positioning outer circle 393 of the second middle housing 39 is positioned, the lower end surface 392 is supported, the lower journal 231 of the second gear shaft 23 is clamped and driven to rotate, and installed on the fixture of the laser welding machine;

[0063] The second sensor body 38 is positioned by the journal 234 on the second gear shaft 23, and the first shaft shoulder end face 233 is supported and welded on the second gear shaft 23;

[0064] The second sensor magnetic ring 37 is positioned by the second middle journal 362 of the second input shaft 36 , supported by the second shaft shoulder end face 361 , and welded to the second input shaft 36 .

[0065] A positioning outer circle 393 is provided on the second middle housing 39 , and the second gear shaft 23 coincides with the axis of the positioning outer circle 393 .

[0066] A method for connecting and assembling a lower shell of a P-EPS, the operation steps are as follows:

[0067] Step 1: First, press the second four-point bearing 27 into the bearing mounting hole 391 of the second middle housing 39 by interference fit to complete the assembly of the middle housing assembly;

[0068] Step 2: The second middle housing 39 is designed to be annular, and then the positioning outer circle 393 is used for installation and positioning, and the bearing installation hole 391 is used for installation of the four-point bearing;

[0069] Step 3: When assembling the second gear shaft 23 and the second input shaft 36, apply high-efficiency long-lasting grease to the outer circumferential surface of the second input shaft 36 that matches the inner hole of the second sliding bearing 31, and apply high-efficiency long-lasting grease to the outer circumferential surface of the second torsion bar 32 that matches the inner hole of the second input shaft 36;

[0070] Step 4: Install the first middle journal 232 on the second gear shaft 23 in the second bearing inner hole 271 of the second four-point bearing 27, and then position it with the journal 234 on the second gear shaft 23, and then axially lock the second four-point bearing 27 with the gear shaft clamp ring 24;

[0071] Step 5: Position the second sensor body 38 with the journal 234 on the second gear shaft 23 and weld the first shaft shoulder end face 233 against the second gear shaft 23;

[0072] Step 6: Position the second sensor magnetic ring 37 with the second middle journal 362 of the second input shaft 36 and support it with the second shoulder end face 361, and weld it to the second input shaft 36;

[0073] Step 7: Press the second needle roller bearing 22 into the lower mounting hole 211 of the second lower housing 21 by interference fit to complete the assembly.

[0074] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A P-EPS middle and lower shell connection structure, comprising a second lower shell (21) and a second middle shell (39), characterized in that: Also includes: The lower mounting hole (211) and the upper mounting hole (212) are respectively opened inside the second lower shell (21). A bearing mounting hole (391) is provided in the second middle shell (39), a second needle roller bearing (22) is fixedly installed in the lower mounting hole (211), and a second four-point bearing (27) is fixedly installed in the bearing mounting hole (391); The second gear shaft (23) and the first middle journal (232), The bottom of the second needle roller bearing (22) is fixedly connected to the upper mounting hole (212), the second four-point bearing (27) is provided with a second bearing inner hole (271), and the second gear shaft (23) and the first middle shaft neck (232) are respectively fixedly connected to the second bearing inner hole (271), and the first middle shaft neck (232) axially locks the second four-point bearing (27).

2. A P-EPS middle and lower shell connection structure according to claim 1, characterized in that: A lower end surface (392) is provided on the inner wall of the second middle shell (39), and an upper end surface (213) is provided on the second lower shell (21); one side of the second needle roller bearing (22) is in contact with the lower end surface (392), and the other side of the second needle roller bearing (22) is fixedly connected to the upper end surface (213) by a second bolt (41), and two planes at the connection are in contact with each other.

3. A P-EPS middle and lower shell connection structure according to claim 2, characterized in that: The second middle housing (39) is annular, and the second middle housing (39) and the second four-point bearing (27) are interference fit.

4. A P-EPS middle and lower shell connection structure according to claim 1, characterized in that: A second sliding bearing (31) is arranged on the second gear shaft (23), a second input shaft (36) is arranged on the inner hole of the second sliding bearing (31), and a second torsion bar (32) is arranged on the inner hole of the second input shaft (36).

5. A P-EPS middle and lower shell connection structure according to claim 4, characterized in that: The second gear shaft (23) is fixedly connected to a second sensor body (38); an upper shaft neck (234) and a first shaft shoulder end face (233) are respectively provided on the second gear shaft (23); and the second sensor body (38) is respectively positioned with the upper shaft neck (234) and abutted against the first shaft shoulder end face (233).

6. A P-EPS middle and lower shell connection structure according to claim 4, characterized in that: The second input shaft (36) is fixedly connected to a second sensor magnetic ring (37), the second input shaft (36) is respectively provided with a second middle shaft neck (362) and a second shaft shoulder end face (361), and the second sensor magnetic ring (37) is respectively abutted against the first middle shaft neck (232) and the second shaft shoulder end face (361).

7. A P-EPS middle and lower shell connection structure according to claim 1, characterized in that: The second needle roller bearing (22) is provided with a bearing inner hole (221), the second gear shaft (23) is provided with a lower journal (231), and the second gear shaft (23) and the lower journal (231) are respectively fixedly connected in the bearing inner hole (221).

8. A P-EPS middle and lower shell connection structure according to claim 4, characterized in that: The critical values ​​of the left and right rotation angles of the second input shaft (36) relative to the second gear shaft (23) are S1 and S2 respectively, and the difference between S1 and S2 is less than or equal to 30°.

9. A P-EPS middle and lower shell connection structure according to claim 1, characterized in that: The second middle housing (39) is provided with a positioning outer circle (393), and the second gear shaft (23) coincides with the axis of the positioning outer circle (393).

10. A method for connecting and assembling a P-EPS middle and lower shell, comprising a P-EPS middle and lower shell connection structure according to any one of claims 1 to 9, characterized in that: The steps are as follows: Step 1: firstly, the second four-point bearing (27) is interference-pressed into the bearing mounting hole (391) of the second middle housing (39) to complete the assembly of the middle housing assembly; Step 2: The second middle housing (39) is designed to be annular, and then the positioning outer circle (393) is used for installation and positioning, and the bearing installation hole (391) is used for installing the four-point bearing; Step 3: When assembling the second gear shaft (23) and the second input shaft (36), apply high-efficiency long-lasting grease to the outer circumferential surface of the second input shaft (36) that matches the inner hole of the second sliding bearing (31), and apply high-efficiency long-lasting grease to the outer circumferential surface of the second torsion bar (32) that matches the inner hole of the second input shaft (36); Step 4: Install the first middle journal (232) on the second gear shaft (23) in the second bearing inner hole (271) of the second four-point bearing (27), and then axially lock the second four-point bearing (27) with the journal (234) on the second gear shaft (23) and the second gear shaft clamp ring (24); Step 5: Weld the second sensor body (38) onto the second gear shaft (23) by using the shaft neck (234) and the first shaft shoulder end surface (233) on the second gear shaft (23); Step 6: Position the second sensor magnetic ring (37) with the second middle journal (362) of the second input shaft (36), support it with the second shaft shoulder end face (361), and weld it to the second input shaft (36); Step 7: Press the second needle roller bearing (22) into the lower mounting hole (211) of the second lower housing (21) by interference fit to complete the assembly.

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