US20090038303A1

US20090038303A1 - Exhaust throttle valve

Info

Publication number: US20090038303A1
Application number: US12/216,698
Authority: US
Inventors: Mitsuru Takeuchi; Naohito Sarai; Koji Sakurai; Naoki Matsubara
Original assignee: Aisan Industry Co Ltd
Current assignee: Aisan Industry Co Ltd
Priority date: 2007-08-08
Filing date: 2008-07-09
Publication date: 2009-02-12
Also published as: JP2009041419A; DE102008036776A1

Abstract

An exhaust pressure control valve comprises a casing including a bore and a pair of first and second shaft support parts, and a valve shaft placed across the bore and rotatably supported by the shaft support parts. A first end portion of the valve shaft is arranged protruding outside the casing. A throttle valve is secured to the valve shaft inside the bore. An actuator is coupled to the first end portion to open and close the throttle valve. The second shaft support part is located in a bypass passage downstream from a bypass valve and has an opening in which a cap formed with a through hole is fitted. The inside of the second shaft support part is allowed to communicate with atmosphere through the through hole, the bypass passage, and others so that an end face of a second end portion can be subjected to atmospheric pressure.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to an exhaust throttle valve to be mounted in an exhaust system of an engine to restrict a flow of exhaust gas.
2. Description of Related Art
Heretofore, one technique of this type is disclosed in, for example, in JP2005-299457A. This '457A discloses an exhaust throttle valve mounted in an exhaust system of a diesel engine, downstream from a continuous regeneration DPF. As shown in FIG. 6, this exhaust throttle valve 61 is configured such that a butterfly valve element 64 is placed in a bore 63 of a casing 62. The casing 62 is formed, at both sides (at right and left sides in the figure), with a first shaft support part 66 and a second shaft support part 67 corresponding to both end portions of a valve shaft 65 respectively. Both end portions 65 a and 65 b of the valve shaft 65 are supported by the shaft support parts 66 and 67 through bearings 68. One end (the first end portion) 65 a of the valve shaft 65 is provided protruding outside the casing 62 and connected to an actuator (not shown) through a lever 69. The other end (the second end portion) 65 b of the valve shaft 65 is supported by the second shaft support part 67 through the bearing 68. An opening 67 a of the valve part 67 at one end is closed by a cover plate 70.
However, in the exhaust throttle valve 61 disclosed in the above '457A, the opening 67 a of the second shaft support part 67 supporting the second end portion 65 b of the valve shaft 65 is closed by the cover plate 70. The inside of the shaft support part 67 is thus closed in bag or box form. Accordingly, when the valve element 64 is brought into a full closing position, the inner pressure of the bore 63 upstream from the valve element 64 rises, acting on the inside of the second shaft support part 67 through a gap between the valve shaft 65 and the bearing 68. At that time, the first end portion 65 a of the valve shaft 65 positioned outside the casing 62 is subjected to atmospheric pressure. This results in a difference in pressure acting on end faces of the end portions 65 a and 65 b of the valve shaft 65, thereby causing the valve shaft 65 to be pressed toward the first end portion 65 a. Consequently, the valve element 64 is also pressed toward the first end portion 65 a, and one side edge of the valve element 64 is pressed against an inner wall of the bore 63. When the valve element 64 in such a pressed state is rotated, the inner wall of the bore 63 may be scratched due to friction with the valve element 64. Such scratches are liable to cause malfunction of the valve element 64.

BRIEF SUMMARY OF THE INVENTION

The present invention has been made in view of the above circumstances and has an object to provide an exhaust throttle valve adapted to mitigate pressure that presses one side edge of a valve element against a bore when the valve element is brought into a full closing position to restrict the flow of exhaust gas.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the purpose of the invention, there is provided an exhaust throttle valve which can be mounted in an exhaust system of an engine to restrict a flow of exhaust gas, comprising: a casing including a bore and a pair of first shaft support part and second shaft support part; a valve shaft that has a first end portion and a second end portion and is placed across the bore, the first end portion being rotatably supported by the first shaft support part and the second end portion being rotatably supported by the second shaft support part, the first end portion having one end passing through the first shaft support part to protrude outside the casing; and a butterfly-type valve element attached to the valve shaft inside the bore; wherein an inside of the second shaft support part supporting the second end portion is allowed to communicate with atmosphere so that an end face of the second end portion can be subjected to atmospheric pressure.
According to another aspect, the invention provides an exhaust throttle valve which can be mounted in an exhaust system of an engine to restrict a flow of exhaust gas, comprising: a casing including a bore and a pair of first shaft support part and second shaft support part; a valve shaft that has a first end portion and a second end portion and is placed across the bore, the first end portion being rotatably supported by the first shaft support part and the second end portion being rotatably supported by the second shaft support part, the first end portion having one end passing through the first shaft support part to protrude outside the casing; and a butterfly-type valve element attached to the valve shaft inside the bore; and an actuator coupled with the end of the first end portion protruding outside the casing and arranged to drive the valve element to open and close, wherein an inside of the second shaft support part supporting the second end portion is allowed to communicate with atmosphere so that an end face of the second end portion can be subjected to atmospheric pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification illustrate an embodiment of the invention and, together with the description, serve to explain the objects, advantages and principles of the invention.

In the drawings,

FIG. 1 is a schematic configuration view showing a configuration of an exhaust system of an engine;

FIG. 2 is a sectional view showing a schematic configuration of main parts of an exhaust pressure control valve in a first embodiment;

FIG. 3 is a sectional view taken along a line A-A in FIG. 2;

FIG. 4 is a sectional view showing a schematic configuration of main parts of an exhaust pressure control valve in a second embodiment;

FIG. 5 is a sectional view showing a schematic configuration of main parts of an exhaust pressure control valve in a third embodiment; and

FIG. 6 is a sectional view sectional view showing a schematic configuration of main parts of an exhaust pressure control valve in a prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiment 1

A detailed description of a first preferred embodiment of an exhaust throttle valve embodying the present invention will now be given referring to the accompanying drawings. In this embodiment, the exhaust throttle valve of the invention is embodied as an exhaust pressure control valve for a diesel engine.
FIG. 1 is a schematic configuration view showing a configuration of an exhaust system of a diesel engine (hereinafter, simply referred to as an “engine”) 1. The exhaust system of the engine 1 includes a diesel particulate filter (DPF) unit 2, an exhaust pressure control valve 3, and a muffler 4. Further, an electronic control unit (ECU) 6 is provided to control a fuel pump 5 of the engine 1 and the exhaust pressure control valve 3. The DPF unit 2 contains a ceramic filter and oxidation catalyst for trapping particulates and graphite (plumbago or black lead) contained in exhaust gas. An upstream side of the DPF unit 2 is connected to an exhaust manifold 8 of the engine 1 through an exhaust pipe 7. A downstream side of the DPF unit 2 is connected to the exhaust pressure control valve 3 through an exhaust pipe 9. A downstream side of the exhaust pressure control valve 3 is connected to the muffler 4 through an exhaust pipe 10. The upstream-side exhaust pipe 7 is attached with a first pressure sensor 11 to detect the pressure of exhaust gas and the downstream-side exhaust pip 9 is also attached with a second pressure sensor 12 to detect the pressure of exhaust gas. The ECU 6 is arranged to receive a detection signal from each of the pressure sensors 11 and 12 and detection signals from various sensors for detecting an operating state of the engine 1. The ECU 6 controls the fuel pump 5 and the exhaust pressure control valve 3 based on those detection signals.
The exhaust pressure control valve 3 is arranged to control the pressure of exhaust gas discharged out of the engine 1. In this embodiment, the exhaust pressure control valve 3 corresponds to an exhaust throttle valve of the invention. The ECU 6 controls the fuel pump 5 according to the operating state of the engine 1 to control a fuel supply amount and a fuel supply timing with respect to the engine 1. Further, the ECU 6 calculates a difference in pressure (differential pressure) detected by the pressure sensors 11 and 12. When the differential pressure exceeds a predetermined value, the ECU 6 closes the exhaust pressure control valve 3 to regenerate a filter of the DPF unit 2.
Exhaust gas discharged out of the engine 1 flows to the DPF unit 2 through the exhaust manifold 8 and the exhaust pipe 7. The DPF unit 2 traps particulates and graphite contained in the exhaust gas to purify or decontaminate the exhaust gas. The exhaust gas purified by the DPF unit 2 passes through the exhaust pipe 9, the exhaust pressure control valve 3, and the exhaust pipe 10 and is released to the atmosphere through the muffler 4.
Herein, as the DPF unit 2 traps particulates and graphite, a pressure loss of the DPF unit 2 increases. This pressure loss appears as a differential pressure between the upstream side and the downstream side of the DPF unit 2. When ECU 6 determines that the differential pressure exceeds the predetermined value based on the detection signals from the pressure sensors 11 and 12, the ECU 6 closes the exhaust pressure control valve 3. Accordingly, exhaust pressure of the engine 1 rises and an amount of fuel to be supplied to the engine 1 is increased according to the exhaust pressure rise. The exhaust gas containing unburned components therefore flows in the DPF unit 2, in which this gas is supplied to the oxidation catalyst placed upstream from the filter. The unburned components supplied to the oxidation catalyst increase the gas temperature in the catalyst by oxidation reaction. This causes the particulates and graphite trapped in the filter of the DPF unit 2 to be burnt, and thus the filter is regenerated. After completion of regeneration of the filter of the DPF unit 2, the ECU 6 controls the exhaust pressure control valve 3 to open and returns to a normal operation. Such regeneration control of the DPF unit 2 is executed every time the pressure loss (differential pressure) of the DPF unit 2 exceeds the predetermined value.
FIG. 2 is a sectional view showing a schematic configuration of main parts of the exhaust pressure control valve 3. This exhaust pressure control valve 3 is provided with a casing 23 including a bore 21 and a bypass passage 22, a butterfly-type throttle valve element (hereinafter, “valve element”) 24 for opening and closing the bore 21, and a bypass valve 25 for opening and closing the bypass passage 22. The valve element 24 corresponds to a valve element of the invention. The bypass valve 25 corresponds to a bypass valve element of the invention. The bypass passage 22 is formed adjacent to in parallel with the bore 21 and defined by a partition wall 26. An upstream side (a left side in the figure) of the bore 21 is connected to the exhaust pipe 9 and a downstream side (a right side in the figure) of the bore 21 is connected to the exhaust pipe 10. The partition wall 26 is formed with an inlet port 22 a and an outlet port 22 b of the bypass passage 22. The inlet port 22 a is formed to open in the bore 21 located upstream from the valve element 24 and the outlet port 22 b is formed to open in the bore 21 located downstream from the valve element 24. The valve element 24 is operated to open or close the bore 21 between the inlet port 22 a and the outlet port 22 b.
As shown in FIG. 2, the valve element 24 is a butterfly-type valve element, which is secured to a valve shaft 27. In association with rotation of the valve shaft 27, the valve element 24 is selectively switched to a position that fully opens the bore 21 or a position that fully closes the bore 21. The bypass valve 25 is a flapper valve and secured to a distal end of an arm 28 with a bolt 29. The arm 28 is rotatable about a pivot shaft 30. The arm 28 is rotated by an actuator (not shown) when the pressure of exhaust gas exceeds a predetermined value, moving the bypass valve 25 to open the bypass passage 22.
FIG. 3 is a sectional view taken along a line A-A in FIG. 2. The inlet port 22 a has a circular section so that the inlet port 22 a is easily gas-tightly closed by the bypass valve 25. The outlet port 22 b has a nearly rectangular section to have a larger passage sectional area than the inlet port 22 a to facilitate the flow of exhaust gas through the outlet port 22 b into the bore 21. As shown in FIG. 2, a downstream side of the outlet port 22 b continuous with the bore 21 is formed as a curved portion 31, thereby allowing the exhaust gas flowing in the bore 21 to easily flow toward the downstream side of the bore 21.
As shown in FIG. 2, the casing 3 further includes a pair of a first shaft support part 32 and a second shaft support part 33. The valve shaft 27 is arranged to extend across the bore 21 and rotatably supported by the first and second shaft support parts 32 and 33. A distal end of an end portion (a first end portion) 27 a of the valve shaft 27 is arranged protruding outside the casing 23. The valve element 24 is secured to the valve shaft 27 inside the bore 21. Specifically, part of the first end portion 27 a of the valve shaft 27 is rotatably supported by the first shaft support part 32 through a bearing 34. This first shaft support part 33 is formed as a boss protruding outside the casing 23. The distal end of the first end portion 27 a of the valve shaft 27 is placed passing through the first shaft support part 32 and protruding outside. In the first shaft support part 32, a seal ring 35 is set adjoining to the bearing 34. This seal ring 35 can prevent leakage of exhaust gas. The distal end of the first end portion 27 a protruding outside through the first shaft support part 32 is coupled with a rod 37 of a diaphragm actuator 36 with a lever 38. The actuator 36 is configured to operate when applied with negative pressure. Supply of negative pressure to the actuator 36 is switched on/off by an unillustrated vacuum switching valve (VSV). The ECU 6 controls opening and closing of this VSV. When negative pressure is supplied to the actuator 36, causing the rod 37 to expand, the valve shaft 27 is rotated by the lever 38. This rotation causes the valve element 24 to be closed.
As shown in FIG. 2, the other end portion (a second end portion) 27 b of the valve shaft 27 is rotatably supported by the second shaft support part 33 through a bearing 39. This second shaft support part 33 is formed as a boss in the partition wall 26 of the casing 23 and located between the inlet port 22 a and the outlet port 22 b. The second end portion 27 b of the valve shaft 27 is fitted and placed in the second shaft support part 33. An opening 33 a of the second shaft support part 33 opens in the bypass passage 22. In this shaft support part 33, a cap 40 is fitted at the opening 33 a to prevent the particulates and graphite from entering. This cap 40 also serves as a stopper for preventing the bearing 39 from coming off the second shaft support part 33. In this embodiment, the cap 40 is formed with a through hole 40 a for providing communication between the inside of the second shaft support part 33 and the bypass passage 22. This allows the inside of the second shaft support part 33 corresponding to the second end portion 27 b of the valve shaft 27 to communicate with atmosphere through the bypass passage 22 and the exhaust pipe 10. Thus, atmosphere will acts on an end face 27 c of the second end portion 27 b through the bypass passage 22. Accordingly, the pressure of exhaust gas to be applied on the end face 27 c is greatly reduced. In measurements, while the valve element 24 is closed, the pressure applied on the end face 27 c was “200 kPa” in the case of the cap 40 formed with no through hole 40 a and the pressure applied on the end face 27 c was reduced to “60 kPa” in the case of the cap 40 formed with the through hole 40 a.
According to the exhaust pressure control valve 3 in this embodiment mentioned above, when the control of regeneration of the DPF unit 2 is executed during operation of the engine 1, the valve element 24 of the exhaust pressure control valve 3 is switched from a fully open state to a fully closed state. Then, the inside of the bore 21 upstream from the valve element 24 increases in pressure by the exhaust gas. This pressure will act on the inside of the second shaft support part 33 supporting the second end portion 27 b of the valve shaft 27 through a gap between the bearing 39 and the valve shaft 27. In this embodiment, however, the inside of the second shaft support part 33 is allowed to communicate with the atmosphere through the through hole 40 a of the cap 40, the bypass passage 22, and others. Accordingly, the inside of the second shaft support part 33 will not remain at high pressure due to the pressure of exhaust gas and the atmospheric pressure will act on the end face 27 c of the second end portion 27 b. At that time, the first end portion 27 a of the valve shaft 27 is located outside the casing 23 and hence subjected to the atmospheric pressure. Both the end portions 27 a and 27 b of the valve shaft 27 are equally subjected to the atmospheric pressure. It is therefore possible to prevent the valve shaft 27 from becoming pressed to one side in its axial direction and to greatly reduce the pressure that presses one side edge of the valve element 24 against the wall surface of the bore 21. As a result, the wall surface of the bore 21 can be protected from becoming scratched by friction with the valve element 24. This makes it possible to prevent malfunction of the valve element 24 resulting from the scratches.
In this embodiment, the through hole 40 a is simply formed in the cap 40 in order to make the inside of the second shaft support part 33 communicate with the bypass passage 22. The need to machine the shaft support part 33 can be eliminated. Further, the through hole 40 a will not impair the ability of the cap 40 to prevent the bearing 39 from coming off the second shaft support part 33.
In this embodiment, the bypass passage 22 is formed in the casing 23 by detouring around the valve element 24. Accordingly, when the inner pressure of the bore 21 upstream from the valve element 24 rises due to the exhaust gas, the bypass valve 25 is opened as appropriate to allow the exhaust gas to flow in the bypass passage 22, so that the rise in inner pressure of the bore 21 upstream from the valve element 24 is mitigated. Consequently, the inner pressure of the bore 21 upstream from the valve element 24 can be controlled appropriately. The regeneration control of the DPF unit 2 can therefore be executed appropriately continuously since the start thereof.
In this embodiment, the inside of the second shaft support part 33 supporting the second end portion 27 b of the valve shaft 27 is made communicate with the bypass passage 22 downstream from the bypass valve 24. Thus, the inside of the second shaft support part 33 will not communicate directly with the outside. This makes it possible to prevent direct outside leakage of exhaust gas from the second shaft support part 33 and maintain reliability as the exhaust pressure control valve 3.

Embodiment 2

A second embodiment of the exhaust throttle valve of the invention will be explained below referring to the accompanying drawings. In each embodiment explained below, similar parts or components to those in the first embodiment are given the same reference codes and their details are not explained repeatedly. The following explanation will be made with a focus on differences from the first embodiment.
FIG. 4 is a sectional view of a schematic configuration of main parts of the exhaust pressure control valve 13 in this embodiment. In this second embodiment, a bypass passage 41 is formed in the casing 23. However, this embodiment differs from the first embodiment in that the opening 33 a of the second shaft support part 33 is not matched with the bypass passage 41 and the opening 33 a of the second shaft support part 33 is not positioned inside the bypass passage 41 but is placed outside the casing 23. In FIG. 4, the bypass passage 41 includes an inlet port 41 a and an outlet port 41 b, and a bypass valve 25 is placed at the inlet port 41 a. A diaphragm actuator 42 is placed close to the bypass passage 41 to cause the bypass valve 25 to open and close.
Except that the exhaust gas may leak out through the through hole 40 a of the cap 40, this embodiment can provide the same operations and advantages as those in the first embodiment.

Embodiment 3

A third embodiment of the exhaust throttle valve of the invention will be explained in detail with reference to the accompanying drawing.
FIG. 5 is a sectional view of a schematic configuration of main parts of an exhaust pressure control valve 14 in the third embodiment. This embodiment differs from the first and second embodiments in that the casing 23 is not provided with any bypass passages 22 and 41, and the opening 33 a of the second shaft support part 33 is placed outside the casing 23.
In this embodiment, consequently, the inner pressure of the bore 21 upstream from the valve element 24 could not be controlled appropriately. Except for it, however, the third embodiment can provide the same operations and advantages as those in the first embodiment.
The present invention is not limited to the above embodiment(s) and may be embodied in other specific forms without departing from the essential characteristics thereof.
For instance, each of the above embodiments embody the exhaust throttle valve of the invention as the exhaust pressure control valve 3, 13, or 14 to be used for the control of regeneration of the DPF unit 2. As an alternative, the exhaust throttle valve of the invention may be applied to an exhaust throttle valve for exhaust brake.
While the presently preferred embodiment of the present invention has been shown and described, it is to be understood that this disclosure is for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.

Claims

1. An exhaust throttle valve which can be mounted in an exhaust system of an engine to restrict a flow of exhaust gas, comprising:

a casing including a bore and a pair of first shaft support part and second shaft support part;

a valve shaft that has a first end portion and a second end portion and is placed across the bore, the first end portion being rotatably supported by the first shaft support part and the second end portion being rotatably supported by the second shaft support part,

the first end portion having one end passing through the first shaft support part to protrude outside the casing; and

a butterfly-type valve element attached to the valve shaft inside the bore;

wherein an inside of the second shaft support part supporting the second end portion is allowed to communicate with atmosphere so that an end face of the second end portion can be subjected to atmospheric pressure.

2. An exhaust throttle valve which can be mounted in an exhaust system of an engine to restrict a flow of exhaust gas, comprising:

a butterfly-type valve element attached to the valve shaft inside the bore; and

an actuator coupled with the end of the first end portion protruding outside the casing and arranged to drive the valve element to open and close,

3. The exhaust throttle valve according to claim 1 further comprising:

a bypass passage formed in the casing to detour the valve element to provide communication between the bore upstream from the valve element and the bore downstream from the valve; and

a bypass valve element for opening and closing the bypass passage.

4. The exhaust throttle valve according to claim 2 further comprising:

a bypass valve element for opening and closing the bypass passage.

5. The exhaust throttle valve according to claim 3, wherein

the inside of the second shaft support part supporting the second end portion is placed to communicate with the bypass passage downstream from the bypass valve element.

6. The exhaust throttle valve according to claim 4, wherein

7. The exhaust throttle valve according to claim 1, wherein

the second end portion is fitted in the second shaft support part and placed inside thereof,

the first and second end portions are rotatably supported by the first and second shaft support parts through bearings respectively.

8. The exhaust throttle valve according to claim 2, wherein

9. The exhaust throttle valve according to claim 5, wherein

10. The exhaust throttle valve according to claim 6, wherein

11. The exhaust throttle valve according to claim 7, wherein

at least one of the first and second shaft support parts includes a seal ring adjoining to the bearing.

12. The exhaust throttle valve according to claim 8, wherein

13. The exhaust throttle valve according to claim 9, wherein

14. The exhaust throttle valve according to claim 10, wherein

15. The exhaust throttle valve according to claim 7, wherein

the second shaft support part has an opening which can be subjected to the atmospheric pressure, and

the exhaust throttle valve further includes a cap fitted in the opening of the second shaft support part, the cap being formed with a through hole for providing communication between the inside and an outside of the second shaft support part so that the atmospheric pressure can act on an end face of the second end portion through the through hole.

16. The exhaust throttle valve according to claim 9, wherein

17. The exhaust throttle valve according to claim 10, wherein

18. The exhaust throttle valve according to claim 11, wherein

19. The exhaust throttle valve according to claim 13, wherein

20. The exhaust throttle valve according to claim 14, wherein