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
However, in the exhaust throttle valve 61 disclosed in the above '457A, the opening 67a of the second shaft support part 67 supporting the second end portion 65b 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 65a 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 65a and 65b of the valve shaft 65, thereby causing the valve shaft 65 to be pressed toward the first end portion 65a. Consequently, the valve element 64 is also pressed toward the first end portion 65a, 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.
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.
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,
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.
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.
As shown in
As shown in
As shown in
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 27b 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 40a 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 27c of the second end portion 27b. At that time, the first end portion 27a of the valve shaft 27 is located outside the casing 23 and hence subjected to the atmospheric pressure. Both the end portions 27a and 27b 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 40a 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 40a 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 27b 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.
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.
Except that the exhaust gas may leak out through the through hole 40a of the cap 40, this embodiment can provide the same operations and advantages as those in the first embodiment.
A third embodiment of the exhaust throttle valve of the invention will be explained in detail with reference to the accompanying drawing.
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.
Number | Date | Country | Kind |
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2007-206152 | Aug 2007 | JP | national |