EGR valve

Abstract

To improve heat radiation properties of heat generated in a drive part and suppress deterioration of performance due to heat generation in the drive part in an EGR valve formed by connecting the drive part that operates electrically to a resin housing.SOLUTION: An EGR valve 1 includes: a resin housing 8 having flow passages 5b, 11a; a valve seat 12 provided in the flow passage; a valve element 13 provided in the flow passage so as to be seated on the valve seat; a valve stem 14 in which the valve element is provided; and a drive part (stepping motor 15) electrically operates to drive the valve stem. A bracket 7 having heat transfer properties is provided between the stepping motor 15 and the housing 8, and the stepping motor and the housing are configured to be supported by a cylinder head of an engine via the bracket.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology disclosed in this specification relates to an EGR valve formed by connecting an electrically operated drive unit to a resin housing.

Background Art

[0002] Conventionally, as this type of technology, for example, the technology of an "EGR valve system" described in Patent Document 1 below is known. This technology includes a valve assembly and a resin housing adapter assembled to the valve assembly. The valve assembly includes a resin housing including an EGR gas flow path, a valve seat provided in the flow path, a valve body provided in the flow path so as to be seated on the valve seat, a valve shaft provided with the valve body, and a drive unit for driving the valve shaft. Here, the drive unit is composed of a motor including a coil and is configured to operate electrically. On the other hand, the housing adapter includes an assembly hole for the housing of the valve assembly, an inlet flow path and an outlet flow path communicating with the assembly hole. Then, the housing of the valve assembly is assembled to the assembly hole of the housing adapter, and in the assembled state, the inlet flow path and the outlet flow path communicate with the flow path of the housing, and a set of EGR valves is configured.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, in the technology described in Patent Document 1, the housing and housing adapter of the valve assembly are made of resin, which results in poor thermal conductivity. When the valve assembly is assembled to the housing adapter, the heat generated by the coil of the drive unit does not escape to the outside well, resulting in poor heat dissipation of the coil. As a result, there is a risk that the coil may exceed its heat resistance temperature, which could lead to a decrease in the performance of the drive unit. On the other hand, when the EGR valve is assembled to the housing adapter, it is conceivable to provide a metal bracket to the EGR valve in order to support it to the engine body or the like. However, because the coil of the drive unit is heavy, in order to ensure strength in the housing adapter, the bracket also needs to be strong, and increasing its plate thickness resulted in the EGR valve becoming larger.

[0005] Patent Document 1 describes a set of EGR valves in which the valve assembly is assembled to a housing adapter. However, the same problems as described above can be expected between the resin housing and the drive unit of an EGR valve in which the housing is not assembled to a housing adapter.

[0006] In conventional EGR valves, where the drive unit was fixed to an aluminum housing and a metal bracket was provided, the heat generated by the coil could be dissipated to the engine body via the bracket regardless of where the bracket was placed on the housing. Alternatively, by providing a cooling water passage in the housing, the heat generated by the coil could be dissipated from the housing to the cooling water without needing to dissipate it via the bracket, thus keeping the coil below its heat resistance temperature. In contrast, when the housing and housing adapter were made of resin and the EGR valve was supported on the engine body via a metal bracket, the poor thermal conductivity of resin meant that the heat generated by the drive unit (coil) could not be adequately dissipated to the engine body, potentially leading to a decrease in the performance of the drive unit.

[0007] This disclosed technology has been made in view of the above circumstances, and its purpose is to improve the heat dissipation of heat generated in the drive unit by electrical operation and suppress performance degradation due to heat generation in the drive unit of an EGR valve, which has an electrically operated drive unit connected to a resin housing. [Means for solving the problem]

[0012] To achieve the above objective, Claim 1 The technology described herein relates to an EGR valve comprising a resin housing containing an EGR gas passage, a valve seat provided in the passage, a valve body provided in the passage so as to be seatable on the valve seat, a valve stem on which the valve body is provided, and an electrically operated drive unit for driving the valve stem, wherein a portion of a heat-conducting bracket is sandwiched between the drive unit and the housing, the drive unit includes a substantially annular coil arranged around the valve stem, and the portion of the bracket is arranged in the circumferential direction of the drive unit, extending inward from the outer diameter edge of the coil between the drive unit and the housing.

[0013] According to the configuration of the above technology The heat generated in the drive unit by electrical operation is not easily transferred to the resin housing, but it is easily transferred to other components via the heat-conducting bracket. A portion of the bracket extends inward from the outer diameter edge of the coil, which is roughly annular in the circumferential direction of the drive unit, between the drive unit and the housing. Therefore, the portion of the bracket that extends inward from the outer diameter edge of the coil is reliably positioned close to the coil.

[0014] To achieve the above objective, Claim 2The technology described herein relates to an EGR valve comprising a resin housing including an EGR gas passage, a valve seat provided in the passage, a valve element provided in the passage so as to be seatable on the valve seat, a valve stem on which the valve element is provided, and an electrically operated drive unit for driving the valve stem, wherein a heat-conducting bracket is provided between the drive unit and the housing or on the drive unit, and the drive unit includes a substantially annular coil arranged around the valve stem and a resin casing covering the coil, and a flange is provided at one end of the casing near the coil, and a part of the bracket is fastened and fixed by bolts on the flange in the circumferential direction of the drive unit.

[0015] According to the configuration of the above technology The heat generated in the drive unit by electrical operation is not easily transferred to the resin housing, but it is easily transferred to other components via the heat-conducting bracket. A portion of the bracket is fastened to the flange of the drive unit by bolts in the circumferential direction of the drive unit. Therefore, at least a portion of the bracket actively contacts the drive unit, increasing the contact area between the drive unit and the bracket.

[0016] To achieve the above objective, Claim 3 The technology described herein relates to an EGR valve comprising a resin housing including a passage for EGR gas, a valve seat provided in the passage, a valve body provided in the passage so as to be seatable on the valve seat, a valve stem on which the valve body is provided, and an electrically operated drive unit for driving the valve stem, wherein a heat-conducting bracket is provided between the drive unit and the housing or on the drive unit, and the EGR valve comprises a valve assembly and a resin housing adapter assembled to the valve assembly, the valve assembly includes a resin sub-housing including a passage, a valve seat, a valve body, a valve stem, and an drive unit, the housing adapter includes an assembly hole for the sub-housing and a passage communicating with the assembly hole, the housing is formed by assembling the sub-housing into the assembly hole of the housing adapter, and in the assembled state, a low thermal conductivity sealing member is provided between the sub-housing and the inner wall of the assembly hole.

[0017] According to the configuration of the above technology The heat generated in the drive unit by electrical operation is not easily transferred to the resin housing, but it is easily transferred to other components via the heat-conducting bracket.The housing is formed by assembling the sub-housing into the assembly hole of the housing adapter. In the assembled state, a low thermal conductivity sealing member is provided between the sub-housing and the inner wall of the assembly hole. Therefore, it becomes difficult for the heat of the EGR gas flowing through the flow path of the housing adapter to be transmitted to the sub-housing, and accordingly, the heat generated in the drive unit is more likely to be transmitted to the bracket.

Effect of the Invention

[0020] According to the technique described in claim 1 the heat dissipation performance of the heat generated in the coil can be further improved by the amount that the bracket is brought closer to the coil. This improves the heat dissipation of the heat generated in the drive unit through electrical operation, thereby suppressing performance degradation due to heat generation in the drive unit. Furthermore,

[0021] 2 According to the technique described in claim This improves the heat dissipation of the heat generated in the drive unit through electrical operation, thereby suppressing performance degradation due to heat generation in the drive unit. Furthermore, the heat dissipation performance of the heat generated in the drive unit can be further improved by the amount that the contact area with the bracket increases.

[0022] 3 This improves the heat dissipation of the heat generated in the drive unit through electrical operation, thereby suppressing performance degradation due to heat generation in the drive unit. Furthermore, According to the technique described in claim the heat dissipation performance of the heat generated in the drive unit can be further improved by the amount that heat is more likely to be transmitted from the drive unit to the bracket.

[0023]

Brief Description of the Drawings

[0024] Hereinafter, embodiments in which the EGR valve is embodied in an EGR device provided in an engine will be described in detail with reference to the drawings.

[0025] [First Embodiment]

[0026] First, the first embodiment will be described in detail with reference to FIGS. 1 to 3.

[0027] [Regarding the EGR Device] FIG. 1 shows a cross-sectional view of the EGR valve 1 in the fully closed state in this embodiment. FIG. 2 shows a perspective view of a part of the EGR device including the EGR valve 1. As is well known, the EGR device is a device that allows a part of the exhaust gas discharged from the combustion chamber of the engine to the exhaust passage to flow as EGR gas into the intake passage and reflux to the combustion chamber. What is shown in FIG. 2 is a part of the EGR device provided in the middle of the EGR passage, and includes an EGR cooler 2 that cools the EGR gas with cooling water, and an EGR valve 1 fixed to the outlet flange 3 of the EGR cooler 2. The EGR valve 1 includes a resin housing adapter 5 connected to the outlet flange 3 via a valve flange 4, and a valve assembly 6 assembled to the housing adapter 5. The downstream side of the housing adapter 5 is connected to an intake manifold (not shown). Also, a metal bracket 7 is provided between the valve assembly 6 and the housing adapter 5. One end of the bracket 7 is fixed between the housing adapter 5 and the valve assembly 6, and the other end is supported by the cylinder head of the engine (not shown).

[0028] [Regarding the EGR Valve] As shown in Figure 1, the EGR valve 1 is configured as both a poppet valve and an electrically operated valve. The EGR valve 1 comprises a valve assembly 6 and a resin housing adapter 5 to which the valve assembly 6 is assembled, as described above. The valve assembly 6 comprises a resin sub-housing 11 including an EGR gas passage 11a, a valve seat 12 provided in the passage 11a, a valve body 13 provided in the passage 11a so as to be seatable on the valve seat 12, a valve stem 14 with the valve body 13 at one end, a stepper motor 15 that operates electrically to drive (stroke) the valve stem 14 together with the valve body 13, a thrust bearing 16 provided between the sub-housing 11 and the valve stem 14 to support the valve stem 14 so as to be able to drive (stroke), and a lip seal 17 provided between the sub-housing 11 and the valve stem 14 to seal the space between them 11 and 14. The stepper motor 15 corresponds to an example of the "drive unit" in this disclosed technology.

[0029] On the other hand, the housing adapter 5 includes the valve flange 4 mentioned above, an assembly hole 5a for the sub-housing 11 of the valve assembly 6, and a flow path 5b communicating with the assembly hole 5a. The sub-housing 11 of the valve assembly 6 is then assembled, or dropped in, into the assembly hole 5a of the housing adapter 5, and in this assembled state, the flow path 5b communicates with the flow path 11a of the sub-housing 11, thereby forming the EGR valve 1. In this assembled state, the sub-housing 11 and the housing adapter 5 constitute the housing 8 of the EGR valve 1. In this assembled state, two upper and lower sealing members 18 and 19 made of rubber with low thermal conductivity are provided between the sub-housing 11 and the inner wall of the assembly hole 5a, flanking the flow path 11a.

[0030] In Figure 1, the valve stem 14 is positioned to penetrate the sub-housing 11 vertically. The valve body 13 is fixed to the lower end of the valve stem 14, has an umbrella shape, and its slanted surface is positioned to contact or be separated from the valve seat 12. A spring retainer 14a is integrally provided on the upper part of the valve stem 14.

[0031] Figure 3 shows a cross-sectional view of the stepper motor 15 in Figure 1 and the connection between the stepper motor 15 and the sub-housing 11 and housing adapter 5. As shown in Figures 1 and 3, the stepper motor 15 includes a stator 22 containing a coil 21 and a magnet rotor 23 provided inside the stator 22, with the upper part of the valve stem 14 positioned at the center of the magnet rotor 23. These components 21-23 are molded and covered by a resin casing 24. A connector 25 protruding laterally is integrally formed on the casing 24. Terminals (not shown) extending from the coil 21 are provided on the connector 25. Furthermore, a casing flange 26 is provided at the lower end (one end) of the casing 24 near the lower end of the coil 21.

[0032] A male screw 27 is provided on the outer circumference of the valve stem 14 above the spring receiver 14a. The magnet rotor 23 includes a rotor body 28 and a cylindrical magnet 29 integrally provided on the outer circumference of the rotor body 28. A first radial bearing 30 is provided between the upper end of the rotor body 28 and the casing 24. A second radial bearing 31 is provided between the lower end of the magnet 29 and the thrust bearing 16. These upper and lower radial bearings 30 and 31 support the magnet rotor 23 so that it can rotate inside the stator 22. A female screw 32 that screws into the male screw 27 is provided at the center of the rotor body 28. A first compression spring 33 is provided between the magnet rotor 23 and the lower second radial bearing 31. Between the spring receiver 14a and the second radial bearing 31, a second compression spring 34 is provided that biases the valve stem 14 toward the magnet rotor 23, that is, biases it in the closing direction so that the valve body 13 seats on the valve seat 12.

[0033] As shown in Figure 1, in the fully closed state with the valve body 13 seated on the valve seat 12, the magnetic rotor 23 rotates in one direction. Due to the screw-like relationship between the male thread 27 of the valve stem 14 and the female thread 32 of the rotor body 28, the valve stem 14 rotates in one direction and strokes downward in the thrust direction as shown in Figure 1, against the biasing force of the second compression spring 34. This stroke motion of the valve stem 14 causes the valve body 13 to stroke downward in Figure 1 along with the valve stem 14, causing the valve body 13 to separate from the valve seat 12 and open the valve.

[0034] On the other hand, in the fully open state (not shown) where the valve body 13 is as far away from the valve seat 12 as possible, the magnetic rotor 23 rotates in the opposite direction. Due to the screw relationship between the male thread 27 of the valve stem 14 and the female thread 32 of the rotor body 28, and the biasing force of the second compression spring 34, the valve stem 14 rotates in the opposite direction while stroking upward in the thrust direction as shown in Figure 1. This stroking motion of the valve stem 14 causes the valve body 13 to stroke upward in Figure 1 along with the valve stem 14, bringing the valve body 13 closer to the valve seat 12 and closing the valve, resulting in the fully closed state shown in Figure 1.

[0035] As shown in Figures 1 and 3, a metal bracket 7 with the aforementioned heat-conducting properties is provided between the valve assembly 6 and the housing adapter 5. As shown in Figure 3, an adapter flange 35 is provided at the upper end of the housing adapter 5. Part of the bracket 7 is positioned between the stepper motor 15 and the housing adapter 5, more specifically between the casing flange 26 and the adapter flange 35. Part of the bracket 7 is also fastened with a bolt 36 while sandwiched between the casing flange 26 and the adapter flange 35. A metal collar 37 is provided between the casing flange 26 and the bolt 36. An insert nut 38 is provided between the adapter flange 35 and the bolt 36, which is threaded onto the bolt 36.

[0036] In the stepper motor 15, the substantially annular coil 21 is positioned around the valve stem 14. As shown in Figure 3, a portion of the bracket 7 extends inward from the outer diameter edge RE of the coil 21 between the casing 24 of the stepper motor 15 and the housing adapter 5 in the circumferential direction of the stepper motor 15. The valve assembly 6 and the housing adapter 5 are then supported by the engine head (other components (not shown)) via the bracket 7 fixed in this manner.

[0037] [Regarding the operation and effects of the EGR valve] As described above, in the configuration of the EGR valve of this embodiment, a heat-conducting bracket 7 is provided between the valve assembly 6, which includes an electrically operated stepper motor 15, and the resin housing 8, and the valve assembly 6 and housing 8 are supported by the engine head via the bracket 7. Therefore, the heat generated by the stepper motor 15 due to electrical operation is not easily transferred to the resin housing 8, but is easily transferred to the engine head (other components) via the heat-conducting bracket 7. For this reason, in the EGR valve 1, which has an electrically operated stepper motor 15 (drive unit) connected to the resin housing 8, the heat dissipation of the heat generated by the stepper motor 15 due to electrical operation can be improved, and the performance degradation due to heat generation of the stepper motor 15 can be suppressed.

[0038] According to the configuration of this embodiment, a portion of the bracket 7 is sandwiched between the stepper motor 15 and the housing 8, so at least a portion of the bracket 7 actively contacts the stepper motor 15, thereby increasing the contact area between the stepper motor 15 and the bracket 7. As a result, the heat dissipation performance of the heat generated by the stepper motor 15 (drive unit) can be further improved by the increased contact area with the bracket 7.

[0039] According to the configuration of this embodiment, a portion of the bracket 7 is positioned to extend inward from the outer diameter edge RE of the substantially annular coil 21 between the stepper motor 15 and the housing 8 in the circumferential direction of the stepper motor 15. Therefore, the portion of the bracket 7 that extends inward from the outer diameter edge RE of the coil 21 is positioned close to the coil 21. As a result, the heat dissipation performance of the heat generated in the coil 21 can be further improved by the amount to which the bracket 7 is positioned close to the coil 21.

[0040] According to the configuration of this embodiment, the housing 8 is formed by assembling the sub-housing 11 into the assembly hole 5a of the housing adapter 5, and in this assembled state, low thermal conductivity sealing members 18 and 19 are provided between the sub-housing 11 and the inner wall of the assembly hole 5a. Therefore, the heat of the EGR gas flowing through the passage 5b of the housing adapter 5 is less likely to be transferred to the sub-housing 11, and the heat generated by the stepper motor 15 is more easily transferred to the bracket 7. As a result, the heat dissipation performance of the heat generated by the stepper motor 15 can be further improved by the amount by which heat is more easily transferred from the stepper motor 15 to the bracket 7.

[0041] In other words, according to the configuration of this embodiment, since sealing members 18 and 19 are provided between the sub-housing 11 and the inner wall of the mounting hole 5a, the sub-housing 11 and the housing adapter 5 are not in direct contact, and the heat of the EGR gas flowing through the passage 5b of the housing adapter 5 is blocked from the sub-housing 11, so that almost no heat flows to the sub-housing 11. Therefore, most of the heat transferred (heat dissipated) from the bracket 7 to the cylinder head is the sum of the heat generated by the coil 21 and the heat received by the sub-housing 11 from the EGR gas. As a result, there is almost no heat transferred from the housing adapter 5 to the bracket 7, and almost all of the heat generated by the coil 21 can be dissipated to the cylinder head (other components) side via the bracket 7. As a result, the temperature rise of the coil 21 can be suppressed, and the performance degradation due to overheating of the stepper motor 15 can be suppressed.

[0042] In addition, in this embodiment, the stepper motor 15 is fastened to the housing adapter 5 with a metal bracket 7 in between, so that the heat-generating stepper motor 15 is directly grounded via the bracket 7, and the contact area is increased by fastening the bolts 36. As a result, the heat transfer rate from the stepper motor 15 to the bracket 7 is improved, and the temperature rise of the stepper motor 15 can be further suppressed.

[0043] <Second Embodiment>

[0044] Next, the second embodiment will be described in detail with reference to Figure 4. In the following description, components equivalent to those in the first embodiment will be denoted by the same reference numerals and their descriptions will be omitted, with the focus being on the differences.

[0045] [About EGR valves] In this embodiment, the configuration differs from the first embodiment in terms of the arrangement of the bracket 7. Figure 4 shows the stepper motor 15 and the connection between the stepper motor 15, the sub-housing 11, and the housing adapter 5 in a cross-sectional view similar to that of Figure 3. As shown in Figure 4, in this embodiment, a part of the bracket 7 is positioned on the casing flange 26 in the circumferential direction of the stepper motor 15 and is fastened and secured by bolts 36 that tighten between the flange 26 and the adapter flange 35. In other words, in this embodiment, the bracket 7 is not sandwiched between the valve assembly 6 and the housing adapter 5, but is fastened and secured on the casing flange 26 by bolts 36.

[0046] [Regarding the operation and effects of the EGR valve] According to the configuration of the EGR valve of this embodiment described above, a portion of the bracket 7 is fastened and fixed to the casing flange 26 of the stepper motor 15 by bolts 36 in the circumferential direction of the stepper motor 15. Therefore, at least a portion of the bracket 7 actively contacts the stepper motor 15, increasing the contact area between the stepper motor 15 and the bracket 7. As a result, the heat dissipation performance of the heat generated by the stepper motor 15 can be further improved by the increased contact area with the bracket 7.

[0047] <Third Embodiment>

[0048] Next, the third embodiment will be described in detail with reference to Figure 5.

[0049] [Regarding the configuration of the EGR valve] In this embodiment, the housing 8 is constructed as a single integrated housing 8, rather than being composed of a sub-housing 11 and a housing adapter 5. Figure 5 shows the stepper motor 15, and Figure 3 shows a cross-sectional view of the connection between the stepper motor 15 and the housing 8. As shown in Figure 5, in this embodiment, a part of the bracket 7 is sandwiched between the casing flange 26 and the housing flange 35 formed on the upper end of the housing 8 and fastened with a bolt 36.

[0050] [Regarding the operation and effects of the EGR valve] According to the configuration of the EGR valve of this embodiment described above, the same operation and effects as those of the first embodiment can be obtained.

[0051] <Another embodiment> Furthermore, this disclosed technology is not limited to the embodiments described above, and it may be implemented by appropriately modifying some parts of the configuration without departing from the spirit of the disclosed technology.

[0052] In the third embodiment described above, as a modification of the first embodiment, the housing 8 is constructed as an integrated housing 8 without being composed of a sub-housing 11 and a housing adapter 5. In contrast, as a modification of the second embodiment, the housing can also be constructed as an integrated housing without being composed of a sub-housing and a housing adapter. [Industrial applicability]

[0053] This disclosed technology can be used in EGR devices installed in engines. [Explanation of symbols]

[0054] 1 EGR valve 5 Housing Adapters 5a Assembly hole 5b Flow channel 6 Valve Assembly 7 Brackets 8 Housing 11 Subhousing 11a Channel 12 valve seats 13 Valve body 14 Valve stem 15 Stepper motor (drive unit) 18 sealing member 19. Sealing member 21 coils 26 Casing flange 35 Adapter flange 36 volts RE outer diameter edge

Claims

1. A resin housing including the EGR gas passage, A valve seat provided in the aforementioned flow path, A valve body is provided in the aforementioned flow path so as to be seatable on the valve seat, The valve stem on which the valve body is provided, A drive unit that operates electrically to drive the valve shaft and In an EGR valve equipped with, A portion of a heat-conducting bracket is sandwiched between the drive unit and the housing. The drive unit includes a substantially annular coil arranged around the valve stem, A portion of the bracket is positioned in the circumferential direction of the drive unit, extending inward from the outer diameter edge of the coil between the drive unit and the housing. An EGR valve characterized by the following features.

2. A resin housing including the EGR gas passage, A valve seat provided in the aforementioned flow path, A valve body is provided in the aforementioned flow path so as to be seatable on the valve seat, The valve stem on which the valve body is provided, A drive unit that operates electrically to drive the valve shaft and In an EGR valve equipped with, A heat-conducting bracket is provided between the drive unit and the housing, or on the drive unit. The drive unit includes a substantially annular coil arranged around the valve stem and a resin casing covering the coil. Near the coil, a flange is provided at one end of the casing. A portion of the bracket is fastened and secured by bolts on the flange in the circumferential direction of the drive unit. An EGR valve characterized by the following features.

3. A resin housing including the EGR gas passage, A valve seat provided in the aforementioned flow path, A valve body is provided in the aforementioned flow path so as to be seatable on the valve seat, The valve stem on which the valve body is provided, A drive unit that operates electrically to drive the valve shaft and In an EGR valve equipped with, A heat-conducting bracket is provided between the drive unit and the housing, or on the drive unit. The EGR valve comprises a valve assembly and a resin housing adapter that is assembled to the valve assembly. The valve assembly includes a resin sub-housing containing the flow path, the valve seat, the valve body, the valve stem, and the drive unit. The housing adapter includes an assembly hole for the sub-housing and a flow path communicating with the assembly hole, The housing is constructed by assembling the sub-housing into the assembly hole of the housing adapter, and in this assembled state, a low thermal conductivity sealing member is provided between the sub-housing and the inner wall of the assembly hole. An EGR valve characterized by the following features.

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