JP2009209913A - Exhaust heat recovery device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make both compatible in not blocking up a bypass passage by a valve element even if a flow rate of exhaust gas increases when the medium temperature is a predetermined value or less and in surely preventing overheat of a medium by blocking up a heat exchange passage by the valve element when heat recovery is not required, in an exhaust heat recovery device for switching the heat exchange passage and the bypass passage by exhaust gas dynamic pressure acting on the valve element. <P>SOLUTION: The first valve element and the second valve element energized in the relative separation direction by an energizing body, are journaled in the rear of the bypass passage, and the first valve element is rotatingly driven by an actuator for expandably operating when the medium temperature becomes the predetermined value or more, and the second valve element is driven by the first valve element via the energizing body. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust heat recovery device that is provided in an exhaust system of a vehicle or the like equipped with an internal combustion engine and recovers exhaust heat to a medium and uses it for warming up.

  Conventionally, as this type of exhaust heat recovery apparatus, a valve body is opened and closed according to the operating state of an internal combustion engine and the temperature of a medium (cooling water or the like), and a bypass that bypasses the heat exchange path and the exhaust gas flow path A device that performs switching control to a route is known. Among these, there is a method that relies on the exhaust gas dynamic pressure applied to the valve body for switching control, but when the exhaust gas flow rate is small and the dynamic pressure is small, the bypass path is blocked, so the flow resistance is large. In some cases, the exhaust gas flow in the heat exchange path alone cannot follow the output demand of the internal combustion engine. In order to solve such a problem, the exhaust heat recovery device described in Patent Document 1 forcibly opens the bypass path regardless of the temperature of the medium when the exhaust gas flow rate increases to a predetermined value or more. Thus, the exhaust gas flow resistance is reduced.

International Patent Publication WO2006 / 090725A1

  However, in a state in which the valve body does not close the bypass path (bypass path open state), the valve body cannot completely close the heat exchange path, so the conduction of the exhaust gas to the heat exchange path cannot be completely stopped, In particular, there was concern about overheating of the medium when the exhaust gas flow rate was large (at the time of large heat input).

  Therefore, the present invention provides that the valve body does not block the bypass path even if the exhaust gas flow rate increases when the medium temperature is below a predetermined value, and that when the heat recovery is unnecessary, the valve body blocks the heat exchange path and overheats the medium. It is an object of the present invention to provide an exhaust heat recovery device that can be reliably prevented.

  In order to solve the above-described problems, the present invention provides a heat exchange path that houses a heat exchanger that performs heat exchange between exhaust gas and a medium, and exhaust gas bypasses the heat exchanger. In an exhaust heat recovery apparatus including a bypass path and a branching section and a merging section before and after both paths, a first valve body capable of closing a heat exchange path is pivotally supported in the merging section, and the first valve body A second valve body that is urged by an urging body in a relative separation direction and can close the bypass path is pivotally supported in the merging portion coaxially with the first valve body, and the first valve body is a temperature of the medium. And the second valve body is driven by the first valve body via the biasing body.

  According to the exhaust heat recovery apparatus of the present invention, the valve body does not close the bypass path even if the exhaust gas flow rate increases when the medium temperature is equal to or lower than the predetermined value, and the valve body closes the heat exchange path when heat recovery is unnecessary. Therefore, it is possible to reliably prevent overheating of the medium.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The product of the present embodiment is not limited to an exhaust heat recovery device attached to an exhaust pipe of an automobile, for example, and is widely used as an exhaust heat recovery device attached to various industrial and household combustion devices. Moreover, although this embodiment assumes the metal welding assembly structure, it is not restricted to this, The integral molding structure by casting or forging may be sufficient.

  FIG. 1 shows the outer shape of the exhaust heat recovery apparatus 1 according to the first embodiment of the present invention, where the left side of the figure is the exhaust gas upstream side and the right side is the downstream side. Exhaust gas transmitted from an upstream exhaust gas component (not shown) flows into the inflow part 2, passes through the heat exchange path 6 and / or bypass path 7 at the branch part 4, flows into the junction part 5, and flows out part 3. And flows into a downstream exhaust gas component (not shown). A medium inlet 8 and a medium outlet 9 are provided in the heat exchange path 6 and communicate with a heat exchanger 23 described later. The branching section 4 and the merging section 5 do not have to be in this shape, and the branching section 4 may have any shape as long as the branching section 4 has an exhaust gas diversion function and the merging section 5 has an exhaust gas merging function. is there.

  A temperature-driven actuator 10 is mounted on the outer surface of the heat exchange path 6, and the actuator 10 communicates with the medium outlet 9 to conduct the medium inside. A rod 11 extending from the actuator 10 is rotatably connected to one end of the crank 12, and the other end of the crank 12 is fixed to the valve shaft 13 so as to be rotatable. As the temperature-driven actuator 10, it is preferable to use a so-called thermo-element type that expands and contracts when the medium temperature acts on the built-in wax.

  FIG. 2 shows a cross section of the exhaust heat recovery apparatus 1 according to the first embodiment of the present invention, and shows a particularly aggressive heat recovery state. In the heat exchange path 6, a plurality of mutually communicating water jackets 21 and exhaust gas passages 22 are alternately arranged to form a heat exchanger 23. That is, the heat exchanger 23 is built in the exhaust heat recovery apparatus 1. The medium inlet 8 and the medium outlet 9 communicate with the water jacket 21 at the uppermost side in FIG. The heated medium flows out from the medium outlet 9.

  A first valve 24 and a second valve 25 that are cantilever butterfly valves are pivotally supported on the merging portion 5 by a common valve shaft 13, but the first valve 24 is fixed to the valve shaft 13, The valve 25 is rotatably fitted to the valve shaft 13. That is, the first valve 24 is rotationally driven according to the rotation of the valve shaft 13, but the second valve 25 does not receive a driving force directly from the valve shaft 13. A spring-like return spring 26 is set coaxially with the valve shaft 13 in the merging portion 5 and is locked to the first valve 24 and the second valve 25 so that the two valves are separated from each other ( Energized to open).

  The return spring 26 is not fixed to the merging portion 5. Further, the return spring 26 is adjusted so that the first valve 24 and the second valve 25 are stopped at a certain maximum angle (relative opening angle). In the present embodiment, the separation angle (relative opening angle) in FIG. 2 is the maximum state, and no further opening is performed. The setting of the separation angle (opening angle) is not limited to the return spring 26, and some locking means may be provided on the valve body or the valve shaft. Furthermore, the return spring 26 is not a spring, and a coil spring or a leaf spring may be directly installed between the first valve 24 and the second valve 25.

  FIG. 2 shows a state where it is desired to positively recover the exhaust gas heat, such as when the engine is warming up (during cold). That is, the second valve 25 is in a state where the rear end of the bypass passage 28 constituting the bypass passage 7 is closed, and almost all of the exhaust gas passes through the heat exchanger 23 in the heat exchange passage 6. In order for the second valve 25 to be in such a position (vertical in FIG. 2), the position of the first valve 24 (the second valve 25 is pressed against the rear end of the bypass passage 28 by the urging force of the return spring 26 ( The opening state of the rod 11 of the actuator 10 when the medium is low is set in advance so that the position (opening degree) of the first valve 24 is obtained. As described above, when the entire amount of the exhaust gas passes through the heat exchanger 23, a silencing effect corresponding to a silencer (muffler) is also obtained.

  Of course, even if the exhaust gas flow rate increases when the medium temperature is equal to or lower than the predetermined value, the second valve 25 receives the exhaust gas dynamic pressure and opens the necessary amount against the urging force of the return spring 26 and does not block the bypass path. . Therefore, even if the exhaust gas flow rate increases to a predetermined value or more, the bypass path is forcibly opened regardless of the medium temperature, and the exhaust gas flow resistance decreases. The thermoelement actuator 10 is in a state where the built-in wax 29 (shown by a two-dot chain line) is most contracted, and the rod 11 is moved by the biasing force of the built-in return spring 30 (shown by a two-dot chain line). FIG. 2 shows a state in which it is pushed upward.

  FIG. 3 shows a state where heat recovery is not required after the engine is warmed up, and the exhaust gas passing through the bypass passage 28 is appropriately throttled. In an exhaust system for an internal combustion engine of an automobile, this corresponds to a time of slow acceleration in which a certain amount of noise reduction effect is expected by the throttle. In this case, since heat recovery is unnecessary, the first valve 24 is set at a position where the heat exchange path 6 is closed and the exhaust gas flow is shut off. This is because the wax 29 of the actuator 10 expands due to an increase in the medium temperature, pushes the rod 11 downward in FIG. 2 against the biasing force of the return spring 30, and the first valve through the rotation of the crank 12 and the valve shaft 13. By pressing 24 against the valve seat 27, the heat exchange path 6 is completely closed. Therefore, overheating of the medium due to heat recovery more than necessary can be surely prevented. And the silencing effect lost by not passing through the heat exchanger 23 can be compensated for by the restriction by the second valve 25 described later.

  In this state, the second valve 25 follows the first valve and moves (from the position shown in FIG. 2), but the second valve 25 tends to separate (try to open each other) by the urging force of the return spring 26. And the exhaust gas dynamic pressure converges to a position (position of FIG. 3) at which it balances. This is a state that is narrower than the maximum separation angle (relative opening angle) in FIG. 2 by the dynamic pressure receiving pressure. By taking into account the back pressure requirement and the silencing requirement by the throttle for the exhaust gas flow rate at this time, bypass It is preferable to adjust the biasing force of the return spring 26 so that the exhaust gas passing through the passage 28 has an opening that is optimally throttled.

  FIG. 4 shows a state in which heat recovery after engine warm-up is not required and the bypass passage 28 is fully open (no throttling). In an exhaust system for an internal combustion engine of an automobile, a rapid acceleration or the like for obtaining a maximum engine output by minimizing an exhaust gas flow rate is applicable. In this case as well, since heat recovery is unnecessary, the first valve 24 is set at a position where the heat exchange path 6 is closed, as in FIG. 3, and the medium is reliably prevented from overheating.

  In this state, the second valve 25 receives a larger exhaust gas dynamic pressure than that in the state of FIG. 3, and converges to a position that balances with the urging force of the return spring 26, that is, the position of FIG. In this state, similarly to the state of FIG. 3, the back pressure requirement and the silencing requirement are considered with respect to the exhaust gas flow rate at this time, and the return spring 26 is set so that the bypass passage 28 has an optimum sectional area (maximum flow passage area). Adjust the biasing force.

  FIG. 5 shows a state in which heat recovery after engine warm-up is not required and the sectional area of the bypass passage 28 is actively reduced. In an exhaust system for an internal combustion engine of an automobile, when the exhaust gas flow rate is low, such as when decelerating, the flow passage cross-sectional area of the bypass passage 28 is further reduced compared with the case of slow acceleration in FIG. is there. In this case as well, heat recovery is unnecessary, so the first valve 24 is still set at a position where the heat exchange path 6 is closed, and overheating of the medium is reliably prevented.

  In this state, the second valve 25 receives an exhaust gas dynamic pressure smaller than that in the state of FIG. 3 and converges to a position that balances with the urging force of the return spring 26, that is, the position of FIG. In this state, as in the state of FIG. 3 and FIG. 4, the back pressure requirement and the silencing requirement are considered with respect to the exhaust gas flow rate at this time, and the return is made so that the bypass passage 28 has the optimum sectional area (maximum flow area). The urging force of the spring 26 is adjusted. For example, if priority is given to the silencing effect at the time of deceleration, it is effective to adjust the flow passage cross-sectional area of the bypass passage 28 to be about 75% to 90%.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, Even if there is a change of the range which does not deviate from the meaning of this invention, it is included by this invention.

  The present invention is not limited to an exhaust heat recovery device attached to an exhaust pipe of an automobile, and the product of the present embodiment can be used for, for example, an exhaust heat recovery device attached to various industrial and household combustion devices. .

It is a front view of the exhaust heat recovery device in one embodiment in the present invention. It is sectional drawing of the exhaust heat recovery apparatus in one Embodiment in this invention. It is sectional drawing of the exhaust heat recovery apparatus in one Embodiment in this invention. It is sectional drawing of the exhaust heat recovery apparatus in one Embodiment in this invention. It is sectional drawing of the exhaust heat recovery apparatus in one Embodiment in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heat recovery apparatus 2 Inflow part 3 Outflow part 4 Branch part 5 Merge part 6 Heat exchange path 7 Bypass path 8 Medium inlet 9 Medium outlet 10 Actuator 11 Rod 12 Crank 13 Valve shaft 21 Water jacket 22 Exhaust gas path 23 Heat exchanger 24 First valve 25 Second valve 26, 30 Return spring 27 Valve seat 28 Bypass passage

Claims (1)

Exhaust heat recovery comprising a heat exchange path that houses a heat exchanger for exchanging heat between the exhaust gas and the medium, a bypass path for the exhaust gas to bypass the heat exchanger, and a branching section and a merging section before and after both paths In the device
A first valve body capable of closing the heat exchange path is pivotally supported in the junction,
A second valve body that is biased by a biasing body in a direction away from the first valve body and can close the bypass path is pivotally supported coaxially with the first valve body in the merging portion;
The first valve body is rotationally driven by an actuator that expands and contracts depending on the temperature of the medium,
The second valve body follows the first valve body via the biasing body;
An exhaust heat recovery device.

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