JP4844600B2 - Exhaust heat recovery unit - Google Patents

Description

  The present invention relates to an exhaust heat recovery unit used for effectively utilizing exhaust heat by transferring heat of exhaust gas to a cooling medium.

  Generally, a heat exchanger (hereinafter referred to as an “exhaust heat recovery device”) is provided in the middle of an exhaust pipe of an internal combustion engine, a combustion apparatus, etc., and switches the internal flow path when necessary to recover the heat of exhaust gas to a gaseous medium or liquid medium. ") Is known.

  In this exhaust heat recovery unit, the recovered heat is delivered to a necessary place such as a vehicle via a cooling medium, or is subjected to secondary heat exchange with another cooling medium in the middle, and finally heated. It is used for warming up various devices and heating oils and fats. On the other hand, when heat recovery is unnecessary, the flow path in the exhaust heat recovery device is switched to guide the exhaust gas to the bypass flow path, and the exhaust gas is discharged straight without going through the heat exchanging portion, thereby suppressing an increase in pressure loss. Therefore, at the time of bypassing, it is desirable that the bypass channel is thick and straight, as well as having no heat exchange part in the channel.

  As a structure of this type of flow path switching type exhaust heat recovery device, a so-called multi-tube type in which an annular gap between a plurality of tubes arranged coaxially is used as a flow path is common.

  Typical examples of such a multi-tube exhaust heat recovery device include those proposed in Patent Documents 1 and 2.

  In the multi-tube exhaust heat recovery device proposed in Patent Document 1, the outer cylinder, the intermediate cylinder, and the inner cylinder are arranged coaxially, and the inner cylinder is connected to the first exhaust passage, and the inner cylinder and the intermediate cylinder are arranged. Is defined in the second exhaust passage, and the gap between the intermediate cylinder and the outer cylinder is defined in the cooling medium path. Further, on the upstream side thereof, a valve body capable of opening and closing the front end of the inner cylinder is provided, and at the time of closing, exhaust gas is mainly guided to the second exhaust passage serving as a heat recovery passage, and then the first through the small hole group. Return to the exhaust passage and discharge. On the other hand, at the time of opening, the exhaust gas is mainly guided and discharged to the first exhaust passage serving as a bypass flow path. Depending on the necessity of heat recovery, the valve body is opened and closed and the flow path is appropriately selected.

  In the multi-pipe exhaust heat recovery device proposed in Patent Document 2, the outer cylinder and the inner cylinder are arranged coaxially, and the inner cylinder has a first exhaust passage and a gap between the inner cylinder and the outer cylinder. Are respectively defined in the second exhaust passages. A cooling medium passage of the spiral tube is provided in the second exhaust passage. A valve body is disposed in the inner cylinder downstream end so as to be openable and closable, and a small hole group is formed in the inner cylinder upstream end. With such a configuration, when the valve body is closed, the exhaust gas is mainly guided to the second exhaust passage serving as a heat recovery path, and is applied to the spiral tubular cooling medium path to perform heat recovery.

  However, in the multi-pipe type exhaust heat recovery device described in Patent Document 1, since the intermediate tube bears the structural strength, it is inevitable to increase the thickness. However, in order to improve the heat exchange efficiency, the intermediate tube which is a heat transfer wall It is difficult to obtain an efficient and high strength exhaust heat recovery device, which has the contradiction that the tube must be thinned.

  Moreover, although the multi-tube exhaust heat recovery device described in Patent Document 2 has a simple double-pipe structure, it has a problem because the cooling medium passage is a spiral tube. That is, the high-temperature exhaust gas hits the uppermost (first winding) spiral, but after that it is difficult to hit the entire surface, so the heat exchange efficiency is low. Therefore, in this cooling medium passage, there is a problem that desired heat recovery is difficult even if the spiral length and thickness are increased. Furthermore, it is very difficult to manufacture a helical tube that is fixed so as not to interfere with the annular second exhaust passage, and to penetrate both ends into the outer cylinder, and the structure for exposing the spring-like object to the pulsating fluid is as follows. There is a risk of vibration damage.

Therefore, in Patent Document 3, in the multi-tube heat recovery device of the flow channel switching type, a simple structure is obtained by configuring the annular cooling medium passage extending in the axial direction with an intermediate cylinder fixed to the inner surface of the outer cylinder. The heat recovery efficiency is improved.
Japanese Utility Model Publication No. 63-110615 Japanese Utility Model Publication No. 63-115520 JP 2006-250524 A

  However, in the exhaust heat recovery device described in Patent Document 3, regarding the heat load of the radiator, the setting of the exhaust heat recovery device has a considerable effect on the cooling water even when exhaust heat is not recovered. That is, there is a problem that power consumption is reached only by the increment of cooling due to an increase in the load on the radiator, which affects the actual fuel consumption. In addition, it is necessary to consider surrounding heat damage.

  This is because the exhaust gas inlet to the exhaust heat recovery unit is always open to a certain area, and high temperature gas is transferred from this opening to the exhaust heat recovery unit at high load, so consider a compact exhaust heat recovery unit This is because it is difficult to increase the distance from the inlet to the exhaust heat recovery unit.

  The present invention has been made in view of the above technical problem, and an exhaust heat recovery device capable of suppressing the flow of exhaust gas to the exhaust heat recovery unit when exhaust heat recovery is unnecessary and reducing the amount of recovered heat at a high temperature. The purpose is to provide.

  In order to achieve the above object, an exhaust heat recovery device according to the present invention is an exhaust heat recovery device used to effectively utilize exhaust heat by transferring heat of exhaust gas to a cooling medium, An exhaust heat recovery part having a heat exchange part for transferring heat of the exhaust gas to the cooling medium inside, a bypass pipe having the front end side as an exhaust gas inlet, and a large number of parts for introducing the exhaust gas into the exhaust heat recovery part A punching pipe in which an opening is formed, and an exhaust valve for switching recovery / non-recovery of exhaust gas by opening and closing a rear end of the punching pipe, and the bypass pipe is an end as a closing member upstream of the exhaust flow The punching pipe extends rearward while being fixed to the plate, and the punching pipe extends forward with the rear end side being fixed to the exhaust heat recovery unit on the downstream side of the exhaust flow, and cooling the exhaust heat recovery unit. Medium The relative expansion between the rear end of the bypass pipe and the opening of the punching pipe that shields the opening of the punching pipe due to the difference between the thermal expansion due to the thermal expansion and the thermal expansion due to the exhaust gas temperature at the exhaust gas inlet. The positional relationship changes.

  In the above configuration, the relative positional relationship between the rear end of the bypass pipe and the opening of the punching pipe that shields the opening of the punching pipe is determined by the thermal expansion caused by the cooling medium of the exhaust heat recovery unit and the exhaust gas at the exhaust gas inlet. It changes depending on the difference from thermal expansion due to temperature. Therefore, to increase the temperature of the cooling medium in order to warm up quickly, the temperature of the bypass pipe is low during cold start, so the effective area of the opening of the punching pipe can be increased, improving exhaust heat recovery performance To do. On the other hand, when the exhaust gas temperature rise due to a high load and the heat received by the cooling medium are to be suppressed from the radiator load, the bypass pipe heats up, so when the exhaust valve is opened, the heat circulates to the exhaust heat recovery unit. Is suppressed, and the amount of recovered heat can be reduced.

  According to the present invention, it is possible to suppress the flow of exhaust gas to the exhaust heat recovery section when exhaust heat recovery is unnecessary, and to reduce the amount of recovered heat at a high temperature.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[First embodiment]
FIG. 1 is a diagram showing a simplified internal structure of an exhaust heat recovery device according to a first embodiment of the present invention.

  Referring to FIG. 1, an exhaust heat recovery device 1 according to the present embodiment is used for effectively utilizing exhaust heat by transferring the heat of engine exhaust gas to cooling water. The exhaust heat recovery unit 3 having heat exchange units 2a and 2b for transferring the heat of the exhaust gas to the cooling water, the bypass pipe 4 having the front end side as the exhaust gas inlet, and the exhaust gas as the exhaust heat recovery unit 3 is provided with a punching pipe 6 in which a large number of minute openings 5 are formed for introduction into the exhaust gas 3, and an exhaust valve 7 for switching exhaust gas recovery / non-recovery by opening and closing the rear end of the punching pipe 6. .

  A cooling water flow path is provided in each of the heat exchange units 2a and 2b. These heat exchanging parts 2a and 2b are arranged inside and outside at intervals. Thus, an inner exhaust gas flow path 8a is formed between the inner heat exchange part 2a and the punching pipe 6, and an outer exhaust gas flow path is formed between the outer heat exchange part 2b and the inner heat exchange part 2a. 8b is formed.

  The bypass pipe 4 extends rearward in a state of being fixed to an end plate 9 serving as a closing member on the exhaust flow upstream side (location indicated by A in FIG. 1). On the other hand, the punching pipe 6 extends forward in a state in which the rear end side is fixed to the exhaust heat recovery unit 3 on the exhaust flow downstream side (location indicated by B in FIG. 1). And the rear end of the bypass pipe 4 that shields the opening 5 of the punching pipe 6 due to the difference between the thermal expansion caused by the cooling water of the exhaust heat recovery unit 3 and the thermal expansion caused by the exhaust gas temperature at the exhaust gas inlet The relative positional relationship with the opening 5 of the punching pipe 6 changes.

  The bypass pipe 4 is connected to a front connection pipe (not shown), but the punching pipe 6 is supported by a holding member 10 having a ring-shaped mesh structure with respect to the bypass pipe 4. Further, the wall thickness of the bypass pipe 4 is thinner than that of the punching pipe 6.

  The exhaust valve 7 is supported by the valve shaft 11 so as to be freely opened and closed, and the opening and closing operation is performed by a thermoactuator (not shown).

  Here, the heat recovery of the exhaust gas performed in the exhaust heat recovery device 1 will be described.

  When the exhaust gas discharged from the engine flows through the bypass pipe 4, as shown in FIG. 1A, when the exhaust valve 7 is closed, the exhaust gas passing through the bypass pipe 4 is changed to an arrow. As shown by, the gas passes through the opening 5 of the punching pipe 6 and is introduced into the inner heat recovery exhaust gas flow path 8a and flows in the direction of the arrow. The exhaust gas flowing through the inner heat recovery exhaust gas flow path 8a exchanges heat with the cooling water in the inner heat exchange section 2a, and then reverses in the end plate 9 to reverse the outer heat recovery exhaust gas flow path 8b. To be introduced.

  Similarly, the exhaust gas flowing in the outer heat recovery exhaust gas passage 8b also exchanges heat with the cooling water in the inner heat exchange portion 2a and the outer heat exchange portion 2b, while the outer heat recovery exhaust gas passage. Go through 8b. Thereafter, the exhaust gas is discharged to the exhaust system constituent members on the downstream side.

  When the heat of the exhaust gas is not recovered by the exhaust heat recovery device 1 or when the amount of heat recovered by the exhaust heat recovery device 1 is suppressed, the exhaust valve 7 is opened as shown in FIG. When the exhaust valve 7 is opened, most of the exhaust gas led to the inner heat recovery exhaust gas flow path 8a through the opening 5 of the bypass pipe 4 passes through the bypass pipe 4 as indicated by an arrow. Then, the air is discharged from the rear end of the punching pipe 6 to the exhaust system components on the downstream side.

  By the way, as described above, the relative positional relationship between the rear end of the bypass pipe 4 and the opening 5 of the punching pipe 6 that shields the opening 5 of the punching pipe 6 is caused by the cooling water of the exhaust heat recovery unit 3. It varies depending on the difference between the thermal expansion and the thermal expansion caused by the exhaust gas temperature at the exhaust gas inlet.

  Therefore, it is desired to increase the temperature of the cooling water in order to warm up early. At the time of cold start, since the temperature of the bypass pipe 4 is low, the effective area of the opening 5 of the punching pipe 6 can be increased, so that the exhaust heat recovery Performance is improved.

  On the other hand, when it is desired to suppress the temperature rise of the exhaust gas due to a high load and the heat received by the cooling water from the radiator load, the bypass pipe 4 is thermally expanded with a displacement amount C as shown in FIG. Along with the opening of the valve 7, the flow of heat into the exhaust heat recovery unit 3 is suppressed, and the amount of recovered heat can be reduced.

  Incidentally, as shown in FIG. 3, the elongation of F based on E (E to F), the elongation of G based on F (F to G), and the elongation of H based on E are expressed by the following equations. Is required.

(1) E elongation based on E (E to F)
(Length) 300 mm × (Average temperature) 80 ° C. × (Coefficient of thermal expansion) 1.2 × 10 ⁻⁵
= 0.29 mm
(2) G elongation based on F (F to G)
(Length) 20 mm × (Average temperature) 500 ° C. × (Thermal expansion coefficient) 1.2 × 10 ⁻⁵
= 0.12 mm
(3) H elongation based on E (length) 300 mm × (average temperature) 800 ° C. × (thermal expansion coefficient) 1.2 × 10 ⁻⁵
= 2.88mm
From the above (1) to (3), when the bypass pipe 4 is extended, the relative displacement amount of the opening 5 is (3) − ((1) − (2)) = 2.88 mm−0.29 mm + 0.12 mm = 2. .71 mm.

  Moreover, since the heat transfer can be avoided by directly supporting the bypass pipe 4 with the punching pipe 6 by the holding member 10 having a ring-shaped mesh structure, it is possible to suppress a further rapid increase in the temperature of the cooling water.

  Furthermore, the heat capacity itself can be reduced by making the wall thickness of the bypass pipe 4 thinner than that of the punching pipe 6, and in this respect also, it is possible to suppress a further rapid increase in the temperature of the cooling water.

[Second Embodiment]
FIG. 3 is a diagram showing a simplified internal structure of an exhaust heat recovery device according to the second embodiment of the present invention.

  Referring to FIG. 3, the exhaust heat recovery device 1 according to the present embodiment is characterized in that a heat insulating material 20 such as a catalyst mat is interposed in a gap (gap) generated between the bypass pipe 4 and the punching pipe 6. The other configuration is the same as that of the first embodiment.

  In the present embodiment, the heat insulating material 20 may be interposed in the entire region of the gap generated between the bypass pipe 4 and the punching pipe 6.

  According to the present embodiment, in addition to the same operations and effects as those of the first embodiment, the following operations and effects are achieved.

  Since the heat insulating material 20 is disposed in the gap generated between the bypass pipe 4 and the punching pipe 6, heat conduction caused by convection of internal air can be suppressed. Therefore, heat conduction to the heat exchange parts 2a and 2b is suppressed during exhaust gas bypass (exhaust gas non-recovery).

[Third embodiment]
FIG. 4 is a diagram showing a simplified internal structure of an exhaust heat recovery device according to the third embodiment of the present invention.

  Referring to FIG. 4, the exhaust heat recovery device 1 according to the present embodiment is characterized in that the connection portion between the bypass pipe 4 and the front side connection pipe 30 has a double pipe structure, and the other configuration is the first. This is the same as the second embodiment.

  According to the present embodiment, in addition to the same functions and effects as those of the second embodiment, the following functions and effects are achieved.

  By connecting the bypass pipe 4 and the front connection pipe 30 with a double pipe structure, the exhaust gas temperature during exhaust heat recovery is suppressed from radiative cooling, and the temperature of the punching pipe 6 is also suppressed during high loads. Can do.

[Fourth embodiment]
FIG. 5 is a diagram showing a simplified internal structure of an exhaust heat recovery device according to the fourth embodiment of the present invention.

  Referring to FIG. 5, the exhaust heat recovery device 1 according to the present embodiment is characterized by an arc shape in which the shaft case 40 of the valve shaft 11 is opened toward the exhaust flow downstream side, and the shaft case forming this arc shape. 40 is located immediately after the exhaust heat recovery unit 3 with a predetermined interval, thereby covering the valve shaft 11 in a semicircular shape, and other configurations are the same as in the embodiment.

  According to the present embodiment, in addition to the same operations and effects as those of the third embodiment, the following operations and effects are achieved.

  Since the exhaust gas immediately after collection is concentrated on the valve shaft 11 and the shaft case 40, the periphery of the valve shaft 11 is not exposed to high temperatures.

  Further, even when the exhaust gas is not recovered, the shaft case 40 (around the valve shaft 11) is close to the exhaust heat recovery unit 3, so that the temperature can be suppressed lower than the vicinity of the opening of the exhaust valve 7.

  Further, since the valve shaft 11 directly below the collector gas is covered in a semicircular shape by the shaft case 40, the condensate in the gas is blocked by the shaft case 40 and the valve shaft 11 is prevented from getting wet. it can.

[Water piping structure on the outlet side of the cooling water of the exhaust heat recovery unit 1]
FIG. 6 is a simplified view of the water piping structure on the cooling water outlet side of the exhaust heat recovery device. In addition, in this figure, although the example which applied the exhaust heat recovery device concerning 1st Embodiment is shown, it may apply the exhaust heat recovery device concerning other Embodiments 2-4. Needless to say.

  Referring to FIG. 6, the water piping structure on the cooling water outlet side of the exhaust heat recovery device 1 pays attention to the fact that the vehicle normally has an underfloor tunnel 50 in the center of the vehicle. An exhaust system 52 including the exhaust heat recovery device 1 is disposed below the insulator 51 that covers the inner surface of the tunnel 50.

  Specifically, the outlet water pipe 53 of the exhaust heat recovery device 1 is extended upward from the upper part of the exhaust heat recovery device main body, and the out pipe 54 to which the outlet water piping 53 is connected is directed upward toward the front of the vehicle. Further, the outlet water pipe 53 and the out pipe 54 are arranged alongside the exhaust pipe 55 almost in parallel under the insulator 51.

  By setting it as such a piping structure, the air cooling of a cooling water can be reduced and stable upward wiring can be implement | achieved.

  Note that the present invention is not limited to the above-described embodiment, and various design changes and modifications can be made within the scope of the appended claims.

It is a figure which simplifies and shows the internal structure of the exhaust heat recovery device concerning the 1st Embodiment of this invention. It is a figure which shows the calculation reference point etc. of the relative displacement amount of the formation part of an opening at the time of expansion of a bypass pipe. It is a figure which simplifies and shows the internal structure of the exhaust heat recovery device concerning the 2nd Embodiment of this invention. It is a figure which simplifies and shows the internal structure of the exhaust heat recovery device concerning the 3rd Embodiment of this invention. It is a figure which simplifies and shows the internal structure of the exhaust heat recovery device concerning the 4th Embodiment of this invention. It is a figure which simplifies and shows the water piping structure by the side of the cooling water outlet of an exhaust heat recovery device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust heat recovery device 2a, 2b Heat exchange part 3 Exhaust heat recovery part 4 Bypass pipe 5 Opening 6 Punching pipe 9 End plate

Claims (1)

An exhaust heat recovery device used to effectively utilize exhaust heat by transferring heat of exhaust gas to a cooling medium,
An exhaust heat recovery section having a heat exchange section for transferring heat of the exhaust gas to the cooling medium inside;
A bypass pipe with the front end side as an exhaust gas inlet;
A punching pipe in which a large number of openings are formed in order to introduce exhaust gas into the exhaust heat recovery section;
An exhaust valve that switches between recovery and non-recovery of exhaust gas by opening and closing the rear end of the punching pipe,
The bypass pipe extends backward in a state of being fixed to an end plate as a closing member on the upstream side of the exhaust flow,
The punching pipe extends forward in a state where the rear end side is fixed to the exhaust heat recovery unit on the exhaust flow downstream side,
The rear end of the bypass pipe and the punching that shield the opening of the punching pipe due to the difference between the thermal expansion caused by the cooling medium of the exhaust heat recovery unit and the thermal expansion caused by the exhaust gas temperature at the exhaust gas inlet An exhaust heat recovery device characterized in that a relative positional relationship with an opening of a pipe changes.

Images