Composite component and method for manufacturing composite component

Abstract

An EGR valve (40) is provided with: a valve shaft (41) having a press-fitting part (41b); and a valve body (42) having a center hole (42a) into which the press-fitting part (41b) is press-fitted. The press-fitting part (41b) has a straight part (51) the outer peripheral surface of which is press-fitted into the center hole (42a). The axial length of the straight part (51) is shorter than the axial length of the center hole (42a).

Description

Composite component and method for manufacturing composite component

[0001] The present disclosure relates to a composite component and a method for manufacturing a composite component.

[0002] Conventionally, composite components configured by assembling a plurality of members have been provided. For example, Patent Document 1 discloses a composite component configured by press-fitting a shaft into a hole of a press-fitted member.

[0003] Japanese National Publication of International Patent Application No. 2015-535749

[0004] Shafts such as linear motion shafts or rotating shafts are often manufactured using machining such as turning. When a shaft is manufactured by machining in this manner, unintended protrusions such as steps or burrs may be formed on the outer circumferential surface of the shaft.

[0005] Therefore, in the composite component disclosed in Patent Document 1, when a shaft having a protrusion formed on the outer circumferential surface thereof is press-fitted into the hole of the press-fitted member, the hole of the press-fitted member may be plastically deformed more than necessary due to the protrusion of the shaft. In this case, there is a risk that the bonding force between the outer circumferential surface of the shaft and the hole of the press-fitted member may decrease.

[0006] The present disclosure has been made to solve the above problems, and an object thereof is to provide a composite component capable of suppressing a decrease in bonding force between a shaft and a press-fitted member even when an unintended protrusion is formed on the outer circumferential surface of the shaft.

[0007] The composite component according to the present disclosure includes a shaft having a press-fitted portion, and a press-fitted member having a hole into which the press-fitted portion is press-fitted. The press-fitted portion has a straight portion whose outer circumferential surface is press-fitted into the hole, and the axial length of the straight portion is shorter than the axial length of the hole.

[0008] According to the present disclosure, even when an unintended protrusion is formed on the outer circumferential surface of the shaft, a decrease in bonding force between the shaft and the press-fitted member can be suppressed.

[0009] This is a longitudinal cross-sectional view of a valve device to which an EGR valve, a composite component according to Embodiment 1, is applied. This is a side view of an EGR valve, a composite component according to Embodiment 1. This is a diagram showing the state before the valve stem is press-fitted into the valve body. This is a diagram showing the outer circumference shape of the press-fit portion in a conventional valve stem. Figure 4A is a side view of a conventional press-fit portion. Figure 4B is an axial cross-sectional view of a conventional press-fit portion. Figure 4C is an enlarged view of the convex portion. This is a diagram showing the outer circumference shape of the press-fit portion according to Embodiment 1. Figure 5A is a side view of the press-fit portion according to Embodiment 1. Figure 5B is an axial cross-sectional view of the press-fit portion according to Embodiment 1. Figure 5C is an enlarged view of the main part of Figure 5B. This is an axial cross-sectional view showing another outer circumference shape of the press-fit portion according to Embodiment 1.

[0010] To provide a more detailed explanation of this disclosure, the forms for implementing this disclosure will be described below with reference to the attached drawings.

[0011] Embodiment 1. The composite component according to Embodiment 1 will be described with reference to Figures 1 to 6. Embodiment 1 described below is an example in which a composite component formed by press-fitting a shaft into a press-fitted member is applied to an EGR valve 40, which is constructed by press-fitting a valve stem 41 into a valve body 42. The composite component according to this disclosure can be applied, for example, to a motor in which a rotating shaft is press-fitted into the central hole of a rotor, a gear component in which a rotating shaft is press-fitted into the central hole of a gear, a cam component in which a camshaft is press-fitted into the central hole of a cam, and so on.

[0012] First, the configuration of the valve device 100 to which the composite component valve according to the embodiment is applied will be explained using Figure 1. Figure 1 is a longitudinal cross-sectional view of the valve device 100 to which the composite component EGR valve 40 according to Embodiment 1 is applied.

[0013] The valve device 100 according to Embodiment 1 shown in Figure 1 is, for example, an EGR valve device for an exhaust gas recirculation (EGR) system mounted on a vehicle.

[0014] The EGR system is intended to reduce harmful substances contained in the exhaust gas discharged from the combustion chamber of a vehicle's engine, or to reduce pumping losses, which are intake resistance caused by the throttle valve. For this reason, the EGR system is equipped with an exhaust gas recirculation passage (hereinafter referred to as the EGR passage) and an EGR valve device, etc.

[0015] The exhaust gas recirculation passage is designed to recirculate (recirculate) a portion of the exhaust gas (hereinafter referred to as EGR gas) from the engine's exhaust passage to the intake passage. The EGR valve device is installed in the middle of the EGR passage to control the flow rate of the EGR gas. The EGR valve device controls the flow rate of the EGR gas from the exhaust passage to the intake passage by adjusting the valve opening.

[0016] Figure 1 shows the valve device 100 according to Embodiment 1 in a fully closed state. The arrow G in Figure 1 indicates the flow direction of the EGR gas. Furthermore, the dashed-dot arrow in Figure 1 indicates the direction of movement of the motor shaft 11 and the valve body 42.

[0017] As shown in Figure 1, the valve device 100 according to Embodiment 1 comprises a motor 10 and a housing 20. The motor 10 is located at the top of the valve device 100. The housing 20 is located at the bottom of the valve device 100. The bottom of the motor 10 and the top of the housing 20 are fixed to each other, for example, using bolts.

[0018] Motor 10 is a so-called direct-acting motor. Motor 10 includes a stator (not shown), a rotor (not shown), and a motor shaft 11 which is the output shaft.

[0019] The stator is cylindrical and fixed. The rotor is rotatably supported relative to the inner circumferential surface of the stator. The motor shaft 11 is supported relative to the rotor so that its rotation around its axis is restricted, and it is movable in the axial direction. The tip of the motor shaft 11 is positioned to protrude downward from the motor 10. Therefore, in the motor 10, when the rotor rotates relative to the stator, the motor shaft 11 reciprocates in its axial direction. In other words, the motor shaft 11 is movable in the vertical direction.

[0020] The housing 20 has an internal space 21, a gas passage 22, and a through hole 23.

[0021] The internal space 21 is located in the upper part of the housing 20. The internal space 21 is formed to be open to the upper surface of the housing 20. The motor 10 is installed so as to cover the internal space 21 from above. At this time, the tip of the motor shaft 11 is located inside the internal space 21. Therefore, the tip of the motor shaft 11 moves back and forth, that is, moves in the vertical direction, within the internal space 21.

[0022] The gas passage 22 is located in the lower part of the housing 20. The gas passage 22 is located in the middle of the EGR passage and forms a part of the EGR passage. The gas passage 22 is formed to extend, for example, from the bottom to the side of the housing 20. The EGR gas flows through the gas passage 22.

[0023] The through-hole 23 is located in the middle of the housing 20 in the vertical direction. The through-hole 23 is a hole that extends in the vertical direction. The through-hole 23 penetrates between the internal space 21 and the gas passage 22. That is, the upper end of the through-hole 23 opens into the internal space 21, and the lower end of the through-hole 23 opens into the gas passage 22.

[0024] Furthermore, the housing 20 is provided with a bearing member 31, a spring holder 32, a spring 33, a valve seat 34, and an EGR valve 40.

[0025] The EGR valve 40 has a valve stem 41 and a valve body 42. The valve stem 41 constitutes the shaft, and the valve body 42 constitutes the press-fitted member. The valve stem 41 is positioned so that its axis extends in the vertical direction. The valve stem 41 is also positioned coaxially with the motor shaft 11. The valve body 42 is provided at the lower end of the valve stem 41. Further details of the EGR valve 40 will be described later.

[0026] The bearing member 31 is provided within the through hole 23. The valve stem 41 of the EGR valve 40 is supported by the bearing member 31 so as to be movable in the vertical direction. Therefore, the upper end of the valve stem 41 is located within the internal space 21. The tip of the motor shaft 11 can contact the upper end of the valve stem 41. The lower end of the valve stem 41 is located within the gas passage 22. That is, the valve body 42 provided at the lower end of the valve stem 41 is located within the gas passage 22.

[0027] The spring holder 32 and the spring 33 are provided within the internal space 21. The spring holder 32 is formed in a circular shape. The central hole of the spring holder 32 is fixed to the outer peripheral surface of the upper end of the valve stem 41 of the EGR valve 40. In contrast, the spring 33 is positioned radially outward from the valve stem 41. The spring 33 is provided in a compressed state between the spring holder 32 attached to the valve stem 41 and the bottom surface of the internal space 21. Therefore, the spring 33 biases the valve stem 41 toward the motor 10, i.e., upward, via the spring holder 32. In this case, the spring 33 is always biasing the EGR valve 40 toward the closing direction.

[0028] The valve seat 34 is formed in an annular shape. The valve seat 34 is located within the gas passage 22. The valve body 42 of the EGR valve 40 can seat on the valve seat 34. Specifically, as shown by the solid line in Figure 1, the valve body 42 seats on the valve seat 34 when the valve stem 41 moves axially upward. In this case, EGR gas does not flow through the gas passage 22. Also, as shown by the dashed line in Figure 1, the valve body 42 disengages from the valve seat 34 when the valve stem 41 moves axially downward. In this case, EGR gas flows through the gas passage 22.

[0029] Therefore, when power is supplied to the motor 10, the motor shaft 11 is pushed out from the axially inward to the axially outward direction of the motor 10. As a result, the tip of the motor shaft 11 presses against the upper end of the valve stem 41 of the EGR valve 40, and the motor shaft 11 moves downward together with the valve stem 41. At this time, the motor shaft 11 moves the valve stem 41 of the EGR valve 40 downward against the biasing force of the spring 33. As a result, the valve body 42 of the EGR valve 40 detaches from the valve seat 34, opening the gas passage 22. Thus, the EGR gas is recirculated from the exhaust passage of the engine towards the intake passage. At this time, the flow rate of the EGR gas is controlled according to the valve opening degree of the valve body 42 relative to the valve seat 34.

[0030] Furthermore, when power is supplied to the motor 10, the motor shaft 11 is pulled in from the axial outer side to the axial inner side of the motor 10. As a result, the tip of the motor shaft 11 moves upward together with the valve stem 41, utilizing the biasing force of the spring 33. Ultimately, the tip of the motor shaft 11 separates from the upper end of the valve stem 41. As a result, the valve body 42 of the EGR valve 40 seats on the valve seat 34, closing the gas passage 22. Therefore, the flow of EGR gas from the exhaust passage to the intake passage is blocked. In other words, the EGR gas is not recirculated into the engine's intake passage.

[0031] Next, the configuration of the EGR valve 40 according to Embodiment 1 will be described with reference to Figures 2 to 6.

[0032] Figure 2 is a side view of the EGR valve 40, which is a composite component according to Embodiment 1. Figure 3 is a diagram showing the state before the valve stem 41 is press-fitted into the valve body 42.

[0033] As shown in Figures 2 and 3, the EGR valve 40 has a valve stem 41 and a valve body 42. The EGR valve 40 is constructed by press-fitting the lower end of the valve stem 41 into the valve body 42. The arrow in Figure 3 indicates the direction in which the valve stem 41 is press-fitted into the valve body 42.

[0034] The valve body 42 has an outer surface that can seat on the valve seat 34. The valve body 42 has a central hole 42a. The central hole 42a is a through hole that penetrates the center of the valve body 42.

[0035] The valve stem 41 has a shaft portion 41a, a press-fit portion 41b, and a press-fit restricting portion 41c. The shaft portion 41a, the press-fit portion 41b, and the press-fit restricting portion 41c are formed in a continuous sequence from the upper end to the lower end of the valve stem 41. That is, the shaft portion 41a is provided on the upper end side of the valve stem 41. The press-fit restricting portion 41c is provided on the lower end side of the valve stem 41. The press-fit portion 41b is provided between the shaft portion 41a and the press-fit restricting portion 41c in the axial direction of the valve stem 41. Furthermore, the shaft portion 41a, the press-fit portion 41b, and the press-fit restricting portion 41c are formed so that their outer diameters increase in order. That is, the outer diameter of the press-fit restricting portion 41c is larger than the outer diameter of the press-fit portion 41b. The outer diameter of the press-fit portion 41b is larger than the outer diameter of the shaft portion 41a.

[0036] The upper end of the shaft portion 41a can contact the tip of the motor shaft 11. The outer diameter of the shaft portion 41a is smaller than the inner diameter of the central hole 42a of the valve body 42. The press-fit portion 41b is the part that is press-fitted into the central hole 42a of the valve body 42. The outer diameter of the press-fit portion 41b is slightly smaller than the inner diameter of the central hole 42a of the valve body 42. The press-fit restricting portion 41c contacts the surface of the valve body 42 when the press-fit portion 41b is press-fitted into the central hole 42a of the valve body 42, thereby restricting further press-fitting of the press-fit portion 41b. The outer diameter of the press-fit restricting portion 41c is larger than the inner diameter of the central hole 42a of the valve body 42.

[0037] Therefore, when the valve stem 41 is press-fitted into the valve body 42, the shaft portion 41a passes through the central hole 42a, causing the press-fit portion 41b to be press-fitted into the central hole 42a. At this time, the press-fit regulating portion 41c comes into contact with the valve body 42, positioning the press-fit portion 41b in an appropriate axial position relative to the central hole 42a. As a result, the press-fit portion 41b is press-fitted into the central hole 42a with an appropriate bonding force.

[0038] Here, the outer circumferential shape of the press-fit portion 41d in a conventional valve stem will be explained using Figure 4. Figure 4 is a diagram showing the outer circumferential shape of the press-fit portion 41d in a conventional valve stem. The arrows shown in Figures 4A and 4B indicate the direction in which the valve stem 41 is pressed into the valve body 42.

[0039] Conventional valve stems have a press-fit portion 41d instead of the press-fit portion 41b of the valve stem 41 according to Embodiment 1. The valve stem 41 according to Embodiment 1 and conventional valve stems are manufactured using machining, such as turning.

[0040] As shown in Figures 4A and 4B, the conventional press-fit portion 41d has an R-shaped portion 55 and a straight portion 51 that are sequentially arranged from the upper end to the lower end in the axial direction. The outer circumferential surface of the straight portion 51 is the portion or range that is press-fitted into the central hole 42a of the valve body 42. The outer diameter of the straight portion 51 is constant in the axial direction. The R dimension of the R-shaped portion 55 is an arbitrary R dimension.

[0041] Thus, in the press-fit portion 41d, the R-shaped portion 55 and the straight portion 51 are formed sequentially from the upper end to the lower end in the axial direction, which can result in the formation of unintended protrusions 54, such as steps or burrs, between the straight portion 51 and the R-shaped portion 55. As shown in Figure 4C, the amount of protrusion of the protrusion 54 from the surface of the straight portion 51 is, for example, several micrometers.

[0042] Therefore, in a conventional valve stem, when the press-fit portion 41d, which has a protrusion 54 formed on its outer circumference, is press-fitted into the central hole 42a of the valve body 42, the protrusion 54 passes through the central hole 42a from the lower end to the upper end. As a result, the entire axial direction of the central hole 42a is plastically deformed more than necessary by the protrusion 54 of the press-fit portion 41d. Consequently, the bonding force between the straight portion 51 of the press-fit portion 41d and the central hole 42a of the valve body 42 is reduced.

[0043] In contrast, the outer peripheral shape of the press-fit portion 41b in the valve shaft 41 according to Embodiment 1 will be described with reference to Fig. 5. Fig. 5 is a diagram showing the outer peripheral shape of the press-fit portion 41b according to Embodiment 1. The arrows shown in Figs. 5A to 5C indicate the press-fitting direction of the valve shaft 41 relative to the valve body 42. Figs. 5B and 5C are diagrams comparing the outer peripheral shape of the press-fit portion 41b according to Embodiment 1 and the outer peripheral shape of a conventional press-fit portion 41d, and the dotted line indicates the outer peripheral shape of the conventional press-fit portion 41d.

[0044] As shown in Figs. 5A to 5C, the press-fit portion 41b according to Embodiment 1 continuously includes a tapered portion 52 and a straight portion 51 in this order from the upper end side to the lower end side in the axial direction.

[0045] The outer peripheral surface of the straight portion 51 is a portion or region that is press-fitted into the center hole 42a of the valve body 42. The outer diameter of the straight portion 51 is constant in the axial direction. In addition, the axial length of the straight portion 51 is shorter than the axial length of the center hole 42a in the valve body 42.

[0046] The tapered portion 52 is a non-press-fit portion that is not press-fitted into the center hole 42a of the valve body 42. The tapered portion 52 is disposed adjacent to the front side of the straight portion 51 in the press-fitting direction. The outer peripheral surface of the tapered portion 52 is an inclined surface that is inclined with respect to the axis of the valve shaft 41. Specifically, the outer peripheral surface of the tapered portion 52 is an inclined surface that is gradually inclined from the lower end side toward the upper end side in the axial direction. In other words, the tapered portion 52 is an inclined surface whose outer diameter gradually decreases from the outer peripheral surface of the straight portion 51 toward the axis of the valve shaft 41. In addition, from the viewpoint of improving the bonding strength, it is preferable that the axial length of the straight portion 51 is longer than the axial length of the tapered portion 52.

[0047] As described above, even if the press-fitting portion 41b is formed by continuously forming the tapered portion 52 and the straight portion 51 in order from the upper end side to the lower end side in the axial direction, an unintended convex portion 54 may still be formed between the straight portion 51 and the tapered portion 52. That is, the convex portion 54 is formed at the front end of the straight portion 51 in the press-fitting direction. However, since the press-fitting portion 41b makes the axial length of the straight portion 51 shorter than the axial length of the center hole 42a, the convex portion 54 can be brought into contact with the center hole 42a.

[0048] Therefore, in the center hole 42a, the portion up to where the convex portion 54 passes will be plastically deformed more than necessary by the convex portion 54, and the convex portion 54 is in a wedge state with respect to the intermediate portion in the axial direction of the center hole 42a. As a result, even when an unintended convex portion 54 is formed on the outer peripheral surface of the press-fitting portion 41b, a decrease in the bonding force between the straight portion 51 and the center hole 42a of the valve body 42 can be suppressed.

[0049] FIG. 6 is an axial cross-sectional view showing another outer peripheral shape of the press-fitting portion 41b according to the first embodiment.

[0050] As shown in FIG. 6, the press-fitting portion 41b may have a small-diameter portion 53 instead of the tapered portion 52. The small-diameter portion 53 is a non-press-fitting portion that is not press-fitted into the center hole 42a of the valve body 42. The tapered portion 52 is arranged adjacent to the front side of the straight portion 51 in the press-fitting direction. An unintended convex portion 54 is formed between the straight portion 51 and the small-diameter portion 53. That is, the convex portion 54 is formed at the front end of the straight portion 51 in the press-fitting direction.

[0051] The outer diameter of the small-diameter portion 53 is smaller than the outer diameter of the straight portion 51. The outer diameter of the small-diameter portion 53 is constant in the axial direction. That is, the outer peripheral surface of the small-diameter portion 53 is a portion or region that is not press-fitted into the center hole 42a of the valve body 42, in other words, does not come into contact with the center hole 42a.

[0052] As described above, the composite component according to Embodiment 1 comprises a valve stem 41 having a press-fit portion 41b and a valve body 42 having a central hole 42a into which the press-fit portion 41b is press-fitted. The press-fit portion 41b has a straight portion 51 whose outer circumferential surface is press-fitted into the central hole 42a, and the axial length of the straight portion 51 is shorter than the axial length of the central hole 42a. Therefore, even if an unintended protrusion 54 is formed on the outer circumferential surface of the valve stem 41, the composite component according to Embodiment 1 can suppress a decrease in the bonding force between the valve stem 41 and the valve body 42.

[0053] In the composite part according to Embodiment 1, the press-fit portion 41b is adjacent to the straight portion 51 and has a non-press-fit portion that is not press-fitted into the central hole 42a, and this non-press-fit portion is positioned on the forward side in the press-fitting direction of the straight portion 51. Therefore, in the composite part according to Embodiment 1, the protrusion 54 formed between the straight portion 51 and the non-press-fit portion can be easily brought into contact with the central hole 42a.

[0054] In the composite component according to Embodiment 1, the axial length of the straight portion 51 is longer than the axial length of the non-press-fit portion. Therefore, the composite component can achieve improved bonding strength.

[0055] In the composite component according to Embodiment 1, the non-press-fit portion is a tapered portion 52 whose outer diameter gradually decreases from the outer circumferential surface of the straight portion 51 toward the axis of the valve stem 41. Therefore, in the composite component according to Embodiment 1, the protrusion 54 formed between the straight portion 51 and the tapered portion 52 can be easily brought into contact with the central hole 42a.

[0056] In the composite part according to Embodiment 1, the non-press-fit portion is a small-diameter portion 53 having an outer diameter smaller than the outer diameter of the straight portion 51. Therefore, in the composite part according to Embodiment 1, the protrusion 54 formed between the straight portion 51 and the small-diameter portion 53 can be easily brought into contact with the central hole 42a.

[0057] Furthermore, in the manufacturing method of the composite component according to Embodiment 1, when the press-fit portion 41b of the valve stem 41 is press-fitted into the central hole 42a of the valve body 42, a straight portion 51 is formed on the press-fit portion 41b that is press-fitted into the central hole 42a, the axial length of the straight portion 51 is made shorter than the axial length of the central hole 42a, and the protrusion formed at the front end of the straight portion 51 in the press-fitting direction is brought into contact with the central hole 42a. For this reason, even if an unintended protrusion 54 is formed on the outer circumferential surface of the valve stem 41, the composite component according to Embodiment 1 can suppress a decrease in the bonding force between the valve stem 41 and the valve body 42.

[0058] Within the scope of this disclosure, any component of the embodiment may be modified or any component of the embodiment may be omitted.

[0059] The composite component according to this disclosure is suitable for use in composite components and the like because the axial length of the straight portion in the press-fit portion is shorter than the axial length of the hole in the member to be press-fitted, thereby suppressing a decrease in the bonding force between the press-fit portion and the hole.

[0060] 10 Motor, 11 Motor shaft, 20 Housing, 21 Internal space, 22 Gas passage, 23 Through hole, 31 Bearing member, 32 Spring holder, 33 Spring, 34 Valve seat, 40 EGR valve, 41 Valve stem, 41a Shaft portion, 41b Press-fit portion, 41c Press-fit restricting portion, 41d Press-fit portion, 42 Valve body, 42a Center hole, 51 Straight portion, 52 Tapered portion, 53 Small diameter portion, 54 Convex portion, 55 R-shaped portion, 100 Valve device.

Claims

1. A composite component comprising a shaft having a press-fit portion and a member to be press-fitted having a hole into which the press-fit portion is press-fitted, wherein the press-fit portion has a straight portion whose outer surface is press-fitted into the hole, and the axial length of the straight portion is shorter than the axial length of the hole.

2. The composite part according to claim 1, characterized in that the press-fit portion has a non-press-fit portion adjacent to the forward side in the press-fit direction of the straight portion and is not press-fitted into the hole.

3. The composite part according to claim 2, characterized in that the axial length of the straight portion is longer than the axial length of the non-press-fit portion.

4. The composite part according to claim 2 or 3, characterized in that the non-press-fit portion is a tapered portion whose outer diameter gradually decreases from the outer circumferential surface of the straight portion toward the axis of the shaft.

5. The composite part according to claim 2 or 3, characterized in that the non-press-fit portion is a small-diameter portion having an outer diameter smaller than the outer diameter of the straight portion.

6. The composite component described in claim 1 is a valve comprising a valve stem having the press-fit portion and a valve body having a central hole into which the press-fit portion is press-fitted.

7. A method for manufacturing a composite part, characterized in that, when press-fitting the press-fit portion of a shaft into a hole in a member to be press-fitted, a straight portion is formed in the press-fit portion that is press-fitted into the hole, the axial length of the straight portion is made shorter than the axial length of the hole, and a protrusion formed at the front end of the straight portion in the press-fitting direction is brought into contact with the hole.

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