JP4736376B2 - Multi-layer sliding member and rack guide in rack and pinion type steering apparatus using the same - Google Patents

Description

  The present invention relates to a multi-layer sliding member and a rack guide in a rack and pinion type steering apparatus using the same.

Japanese Patent Publication No.31-2452 Japanese Patent Publication No. 61-52322 No. 01-27495

  A multi-layer sliding member comprising a backing metal made of a steel plate, a porous metal sintered layer integrally formed on the surface of the backing metal, a pore of the porous metal sintered layer and a synthetic resin layer filled and coated on the surface ( In Patent Literature 1 and Patent Literature 2), the shafts of various mechanical devices are smoothed in the form of a cylindrical bearing bush formed by winding the synthetic resin layer inside, a so-called wound bush, or in the form of a sliding plate. It is widely used as a rack guide (see Patent Document 3) as a support means for supporting the rack bar and as a support means for smoothly supporting the rack bar in the rack and pinion type steering device of an automobile.

  As the synthetic resin that fills the pores of the porous metal sintered layer integrated on the back metal and is coated on the surface, ethylene tetrafluoride resin or polyacetal resin is mainly used under dry friction conditions. In addition, it exhibits excellent low friction properties in the presence of a lubricant such as grease.

However, when these multi-layer sliding members are applied to a rack guide, the multi-layer sliding member having a synthetic resin layer of ethylene tetrafluoride resin is resistant to use under load conditions where the surface pressure exceeds 100 kgf / cm ^2. Abrasion properties are remarkably lowered, and a multi-layer sliding member having a polyacetal resin as a synthetic resin layer has a drawback that the wear resistance is remarkably lowered when the contact pressure exceeds 150 kgf / cm ² .

  The present invention has been made in view of the above-mentioned points, and the object thereof is a multilayer sliding member that exhibits excellent wear resistance in use under high load conditions and a rack and pinion type using the same. It is in providing the rack guide of a steering device.

  The multilayer sliding member of the present invention includes a back plate made of a steel plate, a porous metal sintered layer integrally formed on the surface of the back plate, and the pores of the metal sintered layer are filled and coated on the surface. And an outer layer made of a synthetic resin composition, wherein the synthetic resin composition contains at least nylon 11 or nylon 12.

  Nylon 11 or nylon 12 has the characteristics that the water absorption is smaller than other nylon resins and the powder coating property is excellent. Specific examples include nylon 11 “Rilsan (trade name)” manufactured by Atofina Japan, nylon 12 “Daiamide (trade name)” manufactured by Daicel Degussa.

  The multilayer sliding member of the present invention exhibits excellent wear resistance when used under high load conditions under the presence of a lubricant such as grease.

  In the present invention, the synthetic resin composition may contain 0.1 to 5% by weight of a solid lubricant selected from the group of graphite, molybdenum disulfide, tungsten disulfide and boron nitride as an additional component. These solid lubricants exhibit the effect of improving the wear resistance of the outer layer. If the blending amount is less than 0.1% by weight, the effect of improving the wear resistance of the outer layer cannot be expected. If the blending amount exceeds 5% by weight, the strength of the outer layer made of the synthetic resin composition is impaired. Reduce.

In the present invention, the synthetic resin composition may contain 1 to 20% by weight of the phosphate alone or together with the solid lubricant as an additional component. Examples of the phosphate include metal salts such as secondary phosphate, tertiary phosphate, pyrophosphoric acid, phosphorous acid, and metaphosphoric acid, and mixtures thereof. Of these, metal salts of pyrophosphoric acid and metaphosphoric acid are preferable. As the metal, an alkali metal and an alkaline earth metal are preferable, and lithium (Li), calcium (Ca), and magnesium (Mg) are particularly preferable. Specifically, trilithium phosphate (Li ₃ PO ₄ ), lithium hydrogen phosphate (Li ₃ PHO ₃ ), lithium pyrophosphate (Li ₄ P ₂ O ₇ ), tricalcium phosphate [Ca (PO ₄ ) ₂ ], Calcium hydrogen phosphate (CaHO ₄ ), calcium pyrophosphate (Ca ₂ P ₂ O ₇ ), magnesium pyrophosphate (Mg ₂ P ₂ O ₇ ), calcium metaphosphate [Ca (PO ₃ ) ₂ ] n, magnesium metaphosphate [ Mg (PO ₃ ) ₂ ] n and the like are exemplified.

  These phosphates are not themselves substances that exhibit lubricity like the solid lubricants described above, but are added to the synthetic resin composition, so that the surface of the counterpart material can be used in sliding between the outer layer and the counterpart material. The effect of promoting the film-forming property of the lubricating coating of the synthetic resin composition on the (sliding friction surface) is exhibited. These phosphates are added to the synthetic resin composition in a small amount (for example, 1% by weight), and the effect of promoting the film forming property of the lubricating film of the synthetic resin composition on the surface of the counterpart material begins to appear. The effect is maintained up to 20% by weight. However, when it exceeds 20% by weight, the amount of the lubricating coating formed on the surface of the counterpart material becomes too large, and there is a possibility that the wear resistance is lowered.

  In the present invention, the synthetic resin composition comprises an inorganic filler selected from potassium titanate powder, potassium titanate fiber, wollastonite and barium sulfate as an additional component alone or the solid lubricant and / or phosphate. You may mix | blend with. These inorganic fillers can further improve the wear resistance of the outer layer by blending with the above-described solid lubricant and / or phosphate. The compounding quantity of an inorganic filler is 0.1 to 5 weight%, Preferably it is 0.5 to 3 weight%. If the content is less than 0.1% by weight, the effect of improving the wear resistance is not exerted. If the content exceeds 5% by weight, the exposed ratio on the surface of the outer layer increases, and the counterpart material may be damaged. On the other hand, there is a risk of reducing the wear resistance.

  Next, a multi-layer slide having an outer layer formed by filling and covering the pores of the porous metal sintered layer integrally formed on the surface of the back plate made of a steel plate and the synthetic resin composition having the above-described component composition on the surface. A method for manufacturing the moving member will be described.

  As the back metal, a general structural rolled steel plate is used. Although it is preferable to use a continuous strip provided as a hoop material by winding it in a coil shape, the steel plate is not necessarily limited to a continuous strip, and a strip cut to an appropriate length can also be used. These strips may be subjected to copper plating or tin plating as necessary to improve the corrosion resistance. The thickness of the back plate made of this steel plate is approximately 0.5 mm.

  The metal powder forming the porous metal sintered layer integrally formed on the surface of the back metal is made of a sieve of approximately 100 mesh, such as bronze, lead bronze or phosphor bronze excellent in friction wear characteristics of the metal itself. Passing copper alloy powder is used, but powders other than copper alloy, such as aluminum alloy and iron, can be used depending on the purpose. The metal powder may be in the form of a lump, a sphere, or an irregular shape. The sintered porous metal layer must be firmly bonded to the alloy powder and the strip of the steel plate, and have a certain thickness and the required porosity. The thickness of the sintered porous metal layer is preferably about 0.15 to 0.40 mm, more preferably 0.2 to 0.3 mm, and the porosity is about 10% by volume or more, especially 15 to A volume of 40% is recommended.

  For the outer layer, a nylon 11 or nylon 12 powder or a synthetic resin composition comprising a mixture of nylon 11 or nylon 12 powder and at least one of the above-mentioned solid lubricant, phosphate, and inorganic filler is used.

  The multilayer sliding member of the present invention is manufactured through the following steps (a) to (c).

(A) A synthetic resin composition containing at least nylon 11 or nylon 12 is sprayed and supplied onto a porous metal sintered layer integrally formed on a back metal plate made of a steel plate, and the thickness of the synthetic resin composition is measured with a leveler. To a uniform thickness.
(B) The back metal treated in the step (a) is held for 6 minutes in a heating furnace heated to a temperature of 220 ° C. which is higher than the melting point of nylon 11 (melting point 187 ° C.) or nylon 12 (melting point 177 ° C.), Next, the synthetic resin composition is filled in the pores of the porous sintered layer through a pair of heat rollers heated to a temperature of 80 ° C., and is coated on the porous metal sintered layer to form an outer layer. .
(C) Next, the back metal on which the outer layer of the synthetic resin composition is formed is naturally cooled, and then subjected to a correction roller treatment to obtain a desired multilayer sliding member whose size is adjusted.

  In the multilayer sliding member obtained through the steps (a) to (c), the thickness of the porous metal sintered layer is 0.23 to 0.25 mm, and the thickness of the outer layer formed from the synthetic resin composition The thickness is set to 0.05 to 0.30 mm. The multi-layer sliding member thus obtained is cut into an appropriate size and used as a sliding plate in a flat plate state, or is round-bent and used as a cylindrical wound bush.

  A gear case, a pinion rotatably supported by the gear case, a rack bar formed with rack teeth that mesh with the pinion, a rack guide that slidably supports the rack bar, and the rack guide as a rack bar In the rack and pinion type steering device having a spring that presses toward the rack, the rack guide according to the present invention includes a rack guide base body having a cylindrical outer peripheral surface that is slidably in contact with the cylindrical inner peripheral surface of the gear case. The multilayer sliding member fixed to the rack guide base, and the multilayer sliding member slidably contacts the outer peripheral surface of the rack bar and slidably supports the rack bar. In the outer layer.

  In the present invention, the rack guide base may have an arcuate concave surface and a circular hole at the center of the bottom of the arcuate concave surface, and the multilayer sliding member may have an arcuate concave surface on the outer layer. And a hollow cylindrical protrusion extending from the bottom to the back metal side may be provided at the center of the bottom of the arcuate concave surface.

  A multi-layer sliding member provided with an arc-shaped concave surface complementary to the arc-shaped concave surface on the arc-shaped concave surface of the rack guide base is provided with a hollow cylindrical protrusion protruding from the back surface of the arc-shaped concave surface. The rack guide is formed by being fitted and seated in a circular hole formed in the center of the bottom of the arc-shaped concave surface of the multi-layered sliding member.

  In the present invention, the rack guide base includes a pair of flat surfaces facing each other, a pair of inclined surfaces extending integrally with each other from each of the pair of flat surfaces, and a bottom flat surface integrally extending from the pair of flat surfaces. And having a circular hole in the center of the bottom of the concave surface, the multilayer sliding member includes a pair of opposed inclined surface portions and a pair of flat surface portions that are continuous with the inclined surface portions, respectively. And a bottom surface portion that continues to each of the flat surface portions, and a hollow cylindrical protrusion that extends toward the back metal at the center of the bottom surface portion.

  On the concave surface of the rack guide base, a pair of inclined surface portions facing each other, a pair of flat surface portions continuing to each of the inclined surface portions, a bottom surface portion continuing to each of the flat surface portions, and a center of the bottom surface portion are extended to the back metal side. The multilayer sliding member having a hollow cylindrical projection is seated by fitting the projection at the center of the bottom portion into the hole at the center of the bottom of the concave surface of the rack guide base. A rack guide is formed in which the members are fixed to the rack guide base.

  According to the present invention, a multilayer sliding member that exhibits excellent wear resistance in use under high load conditions under the presence of a lubricant such as grease and a rack and pinion steering device using the same A rack guide can be provided.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to a following example, unless the summary is exceeded.

Examples 1-18
Synthetic resin compositions containing at least nylon 11 or nylon 12 shown in Tables 3 to 6 were supplied into a Henschel mixer and mixed by stirring to obtain synthetic resin compositions. A porous metal (bronze) sintered layer (thickness 0.24 mm) integrally formed on a back metal (thickness 0.50 mm) made of a metal thin plate with the mixed powder of the synthetic resin composition thus obtained It was sprayed and supplied to the top, and the thickness of the synthetic resin composition was adjusted to a uniform thickness with a leveler. Such a synthetic metal composition is held in a heating furnace heated to a temperature of 220 ° C. for 6 minutes, then taken out from the heating furnace, and then passed between a pair of heat rollers heated to a temperature of 80 ° C. Was filled in the pores of the porous metal sintered layer and the synthetic resin composition was coated on the porous metal sintered layer to form an outer layer.

  Next, after the back metal on which the outer layer of the synthetic resin composition is formed is naturally cooled, the outer layer (thickness 0.23 mm) of the synthetic resin composition whose thickness is adjusted by performing the correction roller process is formed. A member was obtained. FIG. 1 is a cross-sectional view showing the multilayer sliding member 51 obtained as described above. In the figure, reference numeral 52 denotes a back metal, and reference numeral 53 denotes a porous metal (bronze) integrally formed on the back metal 52. ) Sintered layer, reference numeral 54 is an outer layer made of a synthetic resin composition filled and coated on the pores and the surface of the porous metal sintered layer 53. After the correction, the multilayer sliding member 51 was cut and subjected to bending to obtain a semicylindrical test piece having a radius of 10.5 mm, a length of 12.0 mm, and a thickness of 0.97 mm.

Comparative Example Pellets of copolymer-type polyacetal resin (“TENAC C4510 (trade name)” manufactured by Asahi Kasei Kogyo Co., Ltd.) were pulverized at low temperature with liquid nitrogen and classified with an 80 mesh sieve to obtain a fine powder having a particle size of 175 μm or less. It was. This fine powder was mixed with 5% by weight of graphite and mixed to obtain a synthetic resin composition. This synthetic resin composition is sprayed and supplied onto a porous metal (bronze) sintered layer (thickness 0.24 mm) integrally formed on a back metal (thickness 0.50 mm) made of a thin metal plate, Thus, the thickness of the mixed powder was adjusted to a uniform thickness. The backing metal is held in a heating furnace heated to a temperature of 200 ° C. for 6 minutes, then taken out of the heating furnace, and then passed through a pair of heat rollers to melt the synthetic resin composition into the pores of the porous metal sintered layer. And a synthetic resin composition was coated on the porous metal sintered layer to form a resin layer.

  Subsequently, the back metal on which the resin layer of the synthetic resin composition is formed is naturally cooled and then subjected to a correction roller treatment to form a resin layer (thickness 0.23 mm) of the synthetic resin composition whose dimensions are adjusted. A sliding member was obtained. After the correction, the multilayer sliding member was cut and then bent to obtain a semicylindrical test piece having a radius of 10.5 mm, a length of 12.0 mm, and a thickness of 0.97 mm.

  The blending ratio in the table is shown by weight%. In addition, as the nylon 11 in the table, “Rilsan (trade name)” manufactured by Atofina Japan Co., Ltd., and as the nylon 12 “Daiamide (trade name)” manufactured by Daicel Degussa Co., as potassium titanate powder Used “TIBREX-AFN (trade name)” manufactured by Kawatetsu Mining Co., Ltd., and “barium sulfate sulfate” manufactured by Sakai Chemical Mining Co., Ltd. as barium sulfate.

  About the semicylindrical test piece produced in Examples 1-18 mentioned above and the comparative example, sliding performance was evaluated by the test method of following (1) and (2).

(1) Reciprocating sliding test The friction coefficient and the amount of wear were measured under the conditions described in Table 1. The coefficient of friction indicates the fluctuation value of the coefficient of friction after the lapse of 1 hour from the start of the test until the end of the test. The amount of wear is the dimensional change of the sliding surface after the end of the test time (20 hours). Indicated.

(Table 1)
Sliding speed 3m / min
Load 500kgf
Time 20 hours Lubrication Mineral oil-based grease [“One Louver MO (trade name)” manufactured by Kyodo Yushi Co., Ltd.] is applied to the sliding surface before the test. Counterpart material High carbon chromium bearing steel (SUJ2)

(2) Thrust test The friction coefficient and the amount of wear were measured under the conditions described in Table 2. The coefficient of friction indicates the coefficient of friction at the time of stability until the end of the test after 1 hour from the start of the test, and the amount of wear indicates the dimensional change of the sliding surface after the end of the test time (20 hours). Shown in quantity.

(Table 2)
Sliding speed 5m / min
Load (surface pressure) 19.6 MPa (200 kg / cm ² )
Time 20 hours Lubrication Mineral oil-based grease [“One Louver MO (trade name)” manufactured by Kyodo Yushi Co., Ltd.] is applied to the sliding surface before the test. Counterpart material Carbon steel for machine structure (S45C)

The semicylindrical test pieces obtained in the above-described examples and comparative examples were tested by the above-described reciprocating sliding test. The test results are shown in Tables 3 to 7. Moreover, the multilayer sliding member obtained by the Example and the comparative example was cut | disconnected, and the plate-shaped test piece whose one side was 30 mm was obtained. The obtained plate-shaped test piece was tested by the above-described thrust test. Test results are shown in Tables 3-7.

  Next, the rack guide in the rack and pinion type steering apparatus using the multilayer sliding member described above will be described.

  2 to 4, a rack and pinion type steering apparatus 1 includes a gear case 3 made of aluminum or aluminum alloy having a hollow portion 2, and a steering supported rotatably on the gear case 3 via rolling bearings 4 and 5. A shaft 6, a pinion 7 disposed in the hollow portion 2 and provided integrally with a shaft end portion (pinion shaft) of the steering shaft 6, and a rack bar 9 formed with rack teeth 8 that mesh with the pinion 7; A rack guide 10 is provided in the hollow portion 2 of the gear case 3 and slidably supports the rack bar 9, and a coil spring 11 presses the rack guide 10 toward the rack bar 9.

  The gear case 3 has a cylindrical portion 12, and the rack bar 9, which passes through the gear case 3 in a direction perpendicular to the axis of the steering shaft 6 and is movably arranged in the perpendicular direction, has rack teeth. An arcuate outer peripheral surface 13 is provided on the back side facing the surface on which 8 is formed.

  The rack guide 10 has an arcuate concave surface 14 and an aluminum or aluminum alloy, zinc or zinc alloy having a circular hole 16 formed in the center of the bottom of the arcuate concave surface 14 in communication with the recess 15 and the recess 15. The rack guide base 17 formed of any one of iron-based sintered metals, the arc-shaped concave surface 18 having a shape complementary to the arc-shaped concave surface 14, and the center of the bottom of the concave surface 18 extend from the bottom to the back metal side. And a hollow cylindrical protruding portion 20 integrally formed with a distal end closing portion 19 as a reinforcing portion, and the protruding portion 20 is fitted into a hole 16 made of a through hole so that the arc-shaped concave surface 14 is tightly fitted. And a curved sliding plate piece 21 fixed to the rack guide base body 17 so as to be seated on the rack guide base member 17, and the multilayer sliding member 51 is used as the sliding plate piece 21. Sliding member 5 The sliding plate piece 21 has a concave surface 18 that slidably contacts the outer peripheral surface of the rack bar 9, in this example, the arc-shaped outer peripheral surface 13 shown in the figure, and supports the rack bar 9 slidably. 54. The rack guide base body 17 is slidably in contact with the inner peripheral surface 23 of the cylindrical portion 12 of the gear case 3 at a cylindrical outer peripheral surface 22 with a sliding clearance, whereby the rack guide 10 is in contact with the axis of the steering shaft 6. It is free to move in a direction perpendicular to it.

  5 and 6 show another example of a rack guide that can be used in the rack and pinion type steering apparatus 1, and the rack guide 10 shown in FIGS. 5 and 6 has one end in the axial direction. A pair of flat surfaces 24 facing each other, a pair of inclined surfaces 25 extending integrally opposite to each other from each of the pair of flat surfaces 24, and a bottom flat surface 26 extending integrally from the pair of flat surfaces 24. Aluminum or aluminum alloy, zinc or zinc alloy, or iron-based ceramics having a concave surface 27 and a recess 28 on the other end side in the axial direction and a circular hole 29 in the center of the bottom of the concave surface 27. A rack guide base 30 formed from any of the bonded metals, a pair of opposed inclined surface portions 31, a pair of flat surface portions 32 continuing to each of the inclined surface portions 31, and a bottom surface portion continuing to each of the flat surface portions 32 33 and the At the center of the surface portion 33, there is a hollow cylindrical protruding portion 35 that is integrally formed with a front end closing portion 34 as a reinforcing portion, and the protruding portion 35 is fitted into the hole 29 to form a concave surface 27. The slide plate piece 36 is fixed to the rack guide base 30 so as to be seated on the rack guide base 30. The multi-layer sliding member 51 is used as the sliding plate piece 36, and the sliding plate piece 36 as the multi-layer sliding member 51 is an outer peripheral surface of the rack bar 9, which is a concave surface 38 in this example. The outer layer 54 has a concave surface 38 that slidably contacts an outer peripheral surface (not shown) having a shape complementary to the outer peripheral surface of the rack bar 9 and slidably supports the rack bar 9. The rack guide base 30 is slidably in contact with the inner peripheral surface 23 of the cylindrical portion 12 of the gear case 3 at the cylindrical outer peripheral surface 37 with a sliding clearance, whereby the rack guide 10 is in contact with the axis of the steering shaft 6. It is free to move in a direction perpendicular to it.

  In the rack and pinion type steering device 1 described above, the rack guide 10 ensures the meshing of the rack teeth 8 with the pinion 7 during the rotation of the steering shaft 6, and further, with respect to the axis of the steering shaft 6 due to the meshing. The movement of the rack bar 9 in the direction perpendicular to the direction is guided.

  The multilayer sliding member of the present invention exhibited good friction and wear characteristics under any test conditions. On the other hand, the multilayer sliding member of the comparative example had a large amount of wear under all the test conditions and was inferior in the frictional wear characteristics. And when the multilayer sliding member which showed the favorable friction-wear characteristic on said test conditions is applied to the sliding piece of a rack guide, a favorable friction-wear characteristic is shown similarly.

It is sectional drawing of the multilayer sliding member of a preferable example of this invention. It is sectional drawing which shows a rack and pinion type steering device. It is the III-III sectional view taken on the line of the rack guide using the multilayer sliding member of this invention shown in FIG. FIG. 4 is a plan view of the rack guide shown in FIG. 3. It is the VV sectional view taken on the line of FIG. 6 of the other rack guide which uses the multilayer sliding member of this invention. FIG. 6 is a plan view of the rack guide shown in FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rack and pinion type steering device 3 Gear case 6 Steering shaft 7 Pinion 9 Rack bar 10 Rack guide 17 Rack guide base body 21 Sliding plate piece

Claims (8)

  A backing metal made of a steel plate, a porous metal sintered layer formed integrally on the surface of the backing metal, and an outer layer made of a synthetic resin composition filled in the pores of the metal sintered layer and coated on the surface. The synthetic resin composition contains at least nylon 11 or nylon 12 and is selected from 1 to 20% by weight of magnesium pyrophosphate, calcium metaphosphate and magnesium metaphosphate as an additional component. A multilayer sliding member comprising a phosphate.   The multi-layer sliding according to claim 1, wherein the synthetic resin composition contains 0.1 to 5 wt% of a solid lubricant selected from the group of graphite, molybdenum disulfide, tungsten disulfide and boron nitride as an additional component. Element.   The synthetic resin composition contains 0.1 to 5% by weight of an inorganic filler selected from potassium titanate powder, potassium titanate fiber, wollastonite, and barium sulfate as an additional component. Multi-layer sliding member.   A gear case, a pinion rotatably supported by the gear case, a rack bar formed with rack teeth that mesh with the pinion, a rack guide that slidably supports the rack bar, and the rack guide as a rack bar In the rack and pinion type steering apparatus having a spring that presses toward the rack, the rack guide includes a rack guide base body having a cylindrical outer peripheral surface that slidably contacts the cylindrical inner peripheral surface of the gear case, and the rack guide A multilayer sliding member according to any one of claims 1 to 3, which is fixed to the base on the back metal side, and the multilayer sliding member is slidably applied to the outer peripheral surface of the rack bar. A rack guide in a rack and pinion type steering device having a concave surface in contact with and slidably supporting a rack bar on its outer layer.   The rack guide in a rack and pinion type steering apparatus according to claim 4, wherein the rack guide base has an arc-shaped concave surface and a circular hole at the center of the bottom of the arc-shaped concave surface.   The multi-layer sliding member has an arc-shaped concave surface on an outer layer thereof and a hollow cylindrical protrusion extending from the bottom to the back metal side at the center of the bottom of the arc-shaped concave surface. A rack guide in the rack and pinion steering device according to claim 5.   The rack guide base is a concave surface having a pair of flat surfaces facing each other, a pair of inclined surfaces extending integrally with each other from each of the pair of flat surfaces, and a bottom flat surface integrally extending from the pair of flat surfaces. The rack guide in the rack and pinion type steering apparatus according to claim 4, further comprising a circular hole at a center of the bottom of the concave surface.   The multi-layer sliding member includes a pair of opposed inclined surface portions, a pair of flat surface portions continuing to each of the inclined surface portions, and a bottom surface portion continuing to each of the flat surface portions, and at the center of the bottom surface portion. The rack guide in the rack and pinion type steering apparatus according to claim 4 or 7, further comprising a hollow cylindrical protrusion extending to the back metal side.

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