CN1005211B - Water heater - Google Patents

Abstract

A water heater with a combustion device and a combustion chamber. The burned gas flows out of the combustion chamber, deflects into the annular space, and then flows along the heat exchanger through the exhaust port on the combustion device. The shell of the heat exchanger is made of plastic, and it forms an annular space together with the metal inner sleeve, and water flows through it as a heat transfer medium. The connection of the plastic shell to the metal inner sleeve is airtight, pressure-resistant, and stable over temperature changes. As a result, the plastic shell reduces the weight of the water heater, and the reduction in heat flow losses from the shell also increases the efficiency of such water heaters.

Description

Water heater

The present invention relates to a water heater, in particular for a motor vehicle. The water heater has a burner and a combustion chamber surrounded by a heat exchanger. An annular outflow space is formed between the burner and the combustion chamber and the heat exchanger, through which the combusted gases flow from the combustion chamber, are forced to turn in opposite directions and then flow to the exhaust ports.

Water heaters of the type described above are used as automotive heaters or auxiliary heaters. In the heat transfer system of the conventional water heater, not only the combustion chamber constituting the inner wall is metallic, but also the outer shell is made of steel or is a metal casting. As a result, the water heater assembly becomes heavy and the choice of steel or cast metal material limits the formation of these parts. This is because die casting is an example of a suitable shape that can be selected to enable cost-effective manufacture. In addition, cast metals, such as steel, because of their good thermal conductivity, radiate heat causing heat loss that reduces the efficiency of the overall water heater. It is particularly disadvantageous that the housing of the water heater, which is also the housing of the complete machine, heats up during operation of the water heater and can therefore only be installed correspondingly in suitable places in the motor vehicle. In most cases, the housing needs to be surface treated to reduce thermal conductivity.

German specification No. 2847525 or european patent No. 0029859 in the description of heat exchangers for evaporators, in particular for air-conditioning systems, indicate that, in view of the special requirements of such heat exchangers for evaporators made of plastic, a connection box is to be produced for it, which, by means of a corresponding design, is selected with a coolant or refrigerant which is as uniform as possible.

From german patent publication 8009473, a heater for a motor vehicle is known, which has a row of pipes inside, which are provided at both ends with two end plates, which are connected to two tanks, respectively, which are made of one piece of plastic. According to siede DE OS2013754, there is a heater, in particular an air heater for a motor vehicle, which has an annular space inside, fresh air being fed in at one end of the space, the air being forced to flow back into the other annular space, since the other end is closed. The housing forming the first annular space is made of two pieces of plastic. Since in this embodiment the fresh air flows along the inner walls of the two plastic shells, no problems due to excess heat arise. In particular, such air heaters do not require the coupling of the type that is air tight, pressure resistant and temperature resistant as is required when joining metal parts to plastic parts. Since such a heater does not use a liquid, such as water, no leakage occurs. If a liquid is used, leakage may occur which may render the heater useless or even damage the vehicle.

In view of the above knowledge, we assume that in the construction of a water heater, in order to form an annular space through which the heat transfer medium can flow, the components in contact with the heat transfer medium must be made of hard stainless steel or cast metal, thereby ensuring that the annular space is sealed from the environment in a gas-tight and pressure-resistant manner. The above difficulties are well recognized in order to ensure that such water heaters will operate reliably for long periods of time.

Furthermore, as shown in us patent No. 3779229, conventionally, after thermal conversion of the heat transfer medium, the hot burned gas is discharged through an exhaust pipe which passes through the annular space of the flow path of the heat transfer medium, and some local heat generation points occur around the exhaust pipe due to the influence of the temperature of the exhaust gas. A similar phenomenon occurs in the spatial end of the heat transfer medium flow path near the exhaust pipe due to the burned gas flow path casting, as described in us 4395225. Such a pipe is robust only if the material properties of the parts to be connected to each other are the same, so that one is forced to use the same material or materials with the same thermal properties for manufacturing the casing kit and the exhaust pipe of the annular space of the flow path for the liquid heat-conducting medium. In water heaters, it is considered that water as the heat transfer medium must flow directly through the annular space of the heat transfer means at a certain operating pressure, and therefore all connections must be pressure-resistant and gas-tight.

Thus, the present invention provides a water heater as mentioned above, with the object of solving the above-mentioned problems. The water heater has compact design, light weight, good sealing performance and suitability for mass production. In particular, it is gas-tight and pressure-resistant and can reliably keep the flow space of the heat transfer medium isolated from the outside.

The key to the present invention is the heat exchanger. The heat exchanger has a plastic outer shell and a metal inner shell. The heat conducting medium flows between the outer shell and the inner sleeve. The connection of the outer shell to the inner sleeve is airtight, pressure resistant and not affected by temperature changes.

Surprisingly, it has been found that the housing not only forms the boundary wall of the annular space through which the heat-conducting medium flows, but also is a housing for the water heater. Such a housing can be made of plastic, thereby greatly reducing the weight of the heater. At the same time, the manufacture of the outer envelope from plastic also offers the possibility of designing the shape of the outer envelope at will, since it is not necessary to make its structural requirements to meet the constraints of the metal casting, in particular the connection of the plastic outer envelope with the metal inner envelope is made gas-tight, pressure-resistant and stable in temperature variations. Further, the water heater has a housing having a strength comparable to that of a heater with a metal housing.

This invention makes it possible to manufacture the heat exchanger shell from plastic. In particular, since the hot exhaust gas pipe is located in the vicinity of the burner, rather than flowing through a heat-conducting medium, the annular space formed by the outer jacket and the inner jacket is formed, while the gas does not pass through the end of the closed annular space. The connection between the plastic outer shell and the metal inner sleeve is far away from the exhaust pipe, so that too high heat does not cause trouble at the connection. The temperature at the junction is approximately the same as the temperature of water as the heat transfer medium. As a heat transfer medium, the temperature of water is much lower than the temperature of the exhaust gas in the exhaust pipe. Thus, according to the invention, in the case of water, the connection is arranged in a so-called low-temperature zone.

The invention uses plastic to make the shell, which not only greatly reduces the weight of the shell, but also reduces the temperature of the shell compared with the metal shell. The water heater has a higher efficiency due to the reduced heat loss caused by heat dissipation. Since the housing of the water heater of the present invention is made of plastic, it does not heat up as much as a metal housing, so it is not necessary to consider the problem of heating up when installing the water heater. At the same time, the plastic housing does not require surface treatment. This heater is well suited for mass production because of the elimination of the pre-extra machining process required for the metal housing. The material of the shell is preferably thermosetting plastic. The shell is salt water tolerant and corrosion resistant even without surface treatment.

The invention improves the efficiency of the water heater by using a simple and constructively rich method. The water heater mounted on a motor vehicle is particularly advantageous because the self weight of the water heater is greatly reduced.

For the preferred embodiment, the connection between the plastic outer shell and the metal inner sleeve is gas-tight, pressure resistant, and stable during temperature changes. In any case, the connection is adapted to the required operating conditions of the water heater, and the connection and assembly is simple. In the embodiment, dry adhesive paint is selected to realize adhesive connection. The adhesive does not corrode the connecting surface, and the plastic outer shell and the metal inner sleeve are firmly adhered together by the adhesive paint through chemical reaction.

In order to ensure the tightness of the joint, other measures can be taken, such as using an O-ring seal or applying a sealant to the joint between the metal and the plastic.

The use of a plastic housing greatly simplifies the manufacture of the baffle. The flow deflecting device is in the form of flow-limiting ribs on the inner wall of the plastic housing, without the inner jacket having to be cast in metal. The features of plastic parts allow more flexibility in design than metal castings.

According to the present invention, since the outer case is made of plastic, the water supply and discharge members can be directly injection-molded on the outer case without causing difficulty in manufacturing, and the water supply and discharge members can be separately manufactured, for example, by using metal to be coupled with the outer case at the time of injection-molding the plastic outer case, or by using the same method as that of coupling the plastic outer case with the metal inner case.

Even if the water feeding part and the water discharging part are made of plastic together with the housing, they can be connected with the metal connecting member and then the connecting pipe is connected with the metal connecting member. The water heater has the advantage that the connection from the hose, the connection piece and thus the water supply and drainage parts can be made in a conventional manner when the metal is compatible with the material of the hose.

Finally, the use of a plastic housing according to the invention makes it possible to injection mould additional components on the housing. They can be used for devices such as cable harnesses, injection molded cable troughs or as heater fixing and support devices. Furthermore, it is possible to make holes in the plastic housing without any effort for attaching accessories such as thermostats.

As mentioned above, according to the present invention, the manufacture of the housing from plastic not only greatly reduces the weight of the water heater, but also brings about unexpected benefits that are not directly related to the reduction in weight.

The above and further objects, features and advantages of the present invention will become more apparent upon consideration of the following description, taken in conjunction with the accompanying drawings, illustrating several embodiments.

The drawings are briefly described as follows:

fig. 1 is a partial sectional view of the entire water heater.

Fig. 2 is a partial cross-sectional view of a plastic housing.

Fig. 3-6 illustrate several embodiments of the plastic outer shell coupled to the metal inner shell. Water as heat conducting medium flows through the annular space formed by the plastic outer shell and the metal inner sleeve.

Fig. 7 is a partial cross-sectional view of a plastic housing.

Fig. 8-10 illustrate other embodiments of the plastic outer shell coupled to the metal inner shell.

The detailed description of the preferred embodiments follows:

figure 1 shows a water heater according to the invention, said water heater being designated in its entirety by reference numeral 1. The water heater 1 has a burner arrangement which extends into the combustion chamber 3. Facing the burner 2, the gases burnt at the rear end of the combustion chamber 3 are forced to flow in a deflected manner into an annular exhaust space 4, where they flow along a heat exchanger 5. The combusted gases pass through the heat exchanger 5 and are then exhausted from the water heater through an exhaust pipe 6 near the burner 2. The figure shows a burner 2, a combustion chamber 3 and an exhaust space 4, which are only shown and explained in the description, to make it possible to understand the invention.

The heat exchanger 5 has an annular space 7 through which water flows as a heat-conducting medium. This annular space is located between the metal inner sleeve 10 and the plastic outer shell 11. In the annular space 7, there are helical flow-limiting ribs 12 constituting the flow-deflecting means, which, according to one embodiment of the invention, are integrally moulded on the inner wall 13 of the plastic casing 11. Thus, the outer wall 9 of the inner sleeve, which is one of the bounding walls of the annular space 7, has a surface without slopes, which simplifies the manufacturing process of the metal inner sleeve 10.

The heat exchanger 5 also has a water feed part 14 and a water discharge part 15 through which water is fed and discharged as a heat transfer medium. The inner shell 10 and the outer shell 11 each have a flange 16 and 17 at their end edges, whereby the outer shell 11 and the inner shell 10 of the heat exchanger are joined together. The joint is not only airtight and pressure-resistant, but also can be kept stable when the temperature changes. The method of connecting the plastic outer shell 11 and the metal inner shell 10 will be explained in more detail in fig. 3 to 6.

As indicated above, the plastic housing 11 is not only the outer wall of the heat exchanger, but also the housing of the water heater 1. On the outer wall 18 of the housing 11 there is a box 19 into which the various control elements of the heater can be fitted. Without making the manufacturing process more complicated. Also, it is possible to make a device for fixing and supporting the heater 1 and other accessories, such as a thermostat, since most of the plastic outer wall 18 of the housing 11 can be shaped at will, the tank 19 and the fixing frame 20 being only two examples, as regards which the water heater 1 can be fixed to the corresponding part of the motor vehicle by means of a not shown cast-shaped clamping plate, passing through the hollow of the fixing frame 20.

Fig. 2 is a detailed view of the entire plastic housing 11. Reference numerals 14 and 15 denote water supply and discharge parts, respectively. Through which water is fed into and discharged from the heat exchanger 5. The plastic housing is cup-shaped and its inner wall 13 forms a boundary wall of the annular space 7 of the heat exchanger 5. The housing 19 and the holder 20 are located above the outer wall 18 of the housing 11, also shown in fig. 2.

Fig. 3 to 6 illustrate various connection means between the plastic outer shell 11 and the metal inner shell 10 in detail. These connections are gas tight, pressure resistant and stable over temperature changes, and the inner sleeve 10 is an aluminum casting. Naturally, the various connection methods shown in fig. 3 to 6 can be combined or interchanged.

Fig. 3 shows a threaded connection 21. The flange 17 of the plastic housing 11 has a threaded hole 22 and the flange 16 of the inner sleeve 10 has a counter bore 23 that mates with the threaded hole 22. The flanges 16 and 17 are firmly connected by screws 24. As shown in the figure, an O-ring 25 is arranged between the parts where the inner wall of the plastic outer shell 11 and the outer wall of the metal inner shell 10 are in contact, which is pressed by both walls. The connection 21 ensures that the annular space is air tight when the screws 24 are tightened. Although fig. 3 shows only one screw at 21 on the flange, several screws may be used evenly around the flanges 16 and 17 as desired.

Fig. 4 shows an adhesive connection, which is designated in its entirety by 26. The inner surface of the flange 16 and the outer surface of the flange 17 constitute an adhesive surface 27 for bonding them together. The adhesive surface 27 is coated with a dry adhesive paint which, through a chemical reaction, solidifies between the metal inner shell 10 and the plastic outer shell 11 to form an airtight, pressure-resistant and stable joint under temperature change, and which does not corrode the joint portion between the plastic outer shell 11 and the metal inner shell 10. Of course, the adhesive surface must have a relatively large area to ensure that the connection between the outer shell 11 and the inner shell 10 on the adhesive surface 27 is secure. Alternatively, for safety reasons, a metal annular sleeve 8 may be used to hold the flanges 16 and 17 together, as shown in figure 1.

The reference numeral 28 is attached in fig. 5. The flange 17 of the plastic housing 11 and the flange 16 of the metal inner housing are enclosed by an injection molded sleeve 29 which is milled and cast. In order to ensure the engagement force of the forming sleeve 29, the flanges 16 and 17 each have a projection 30, 31 in opposite directions.

In fig. 6 a riveted connection 32 connects the plastic outer shell 11 and the metal inner shell 10. The flange 16 of the inner sleeve 10 has a plurality of holes 33 through which plastic rivets are passed and, after mating therewith, heated to form rivet joints 35. To ensure the reliability of the seal, the sealing surfaces 36 and 37 of the flanges 16 and 17, respectively, are coated with a sealing compound. Such a sealant may also be used for the other connections described above. Also, in order to increase the stability of the connection, a forming sleeve as described in fig. 5 can be used as an additional outer sleeve. Other various specific connection methods may also be used in combination or interchanged.

Fig. 7 illustrates the structure of the water feed part 14 and the water discharge part 15 of the heat exchanger 5. In this embodiment, the parts 14 and 15 are formed together with the plastic housing 11. Although not illustrated, it will be appreciated that the plastic housing 11 has two holes therein, and that the separately manufactured components 14 and 15 are inserted into the plastic housing 11 during final assembly and attached thereto in the same or similar manner as described with reference to figures 3 to 6. In this case, the water feeding and discharging member may be made of a metal alloy. Fig. 7 illustrates that metal connectors 45 may be inserted into the water supply and drainage components 14 and 15 formed with the housing and then connected in a similar manner as illustrated in fig. 3-6. The connector is used to connect the water pipe so that the water pipe can be connected to the metal member by a conventional method.

Fig. 8, 9 and 10 show other embodiments of connecting the plastic outer shell 11 and the metal inner shell 10. Parts that are identical or similar to the embodiments described above use the same reference numerals.

As shown in fig. 8, the flange 16 of the metal inner case 10 is formed in a thick ring shape. Its peripheral region is located almost in the same plane as the inner wall of the plastic housing 11. In order to connect the flange 16 of the inner sleeve 10 thus designed to the outer shell 11, the contacting portions are bonded together. In this case, the adhesive surface extends as far as possible in a direction parallel to the longitudinal axis of the plastic outer shell 11 and the metal inner sleeve 10. For sealing purposes, an O-ring 25 is arranged between the burner 2 and the flange 16. In this embodiment, a sufficiently large adhesive surface is possible parallel to the longitudinal axis of the outer shell 11 and the inner sleeve 10, while the thickness of the plastic shell material in the radial direction must also be taken into account.

Figure 9 shows a similar embodiment. Is a two-in-one design. The ring member 38 is welded to the outer wall of the metal inner case 10 and then interposed between the outer wall of the inner case 10 and the inner wall of the outer case 11. The annular part 38 extends almost to the inner wall of the outer shell 11, as is the case in fig. 8, and accordingly forms a large-area bond parallel to the longitudinal axes of the inner shell 10 and the outer shell 11. In fig. 9, there is also an O-ring 25 which is arranged between the flange 46 of the burner 2 and the ring element 38.

According to the embodiment of fig. 10, the flange 16 of the inner sleeve 10 is manufactured so that it is arranged approximately on the inner wall surface of the plastic housing 11, coaxially to the surface 9, with the annular surface 39 extending forward in a direction away from the burner 2 parallel to the longitudinal axis of the housing 10, and the plastic housing 11 is glued to the annular surface 39 of the flange 16. The adhesion between the plastic outer shell 11 and the metal inner sleeve 10 on the annular part of the flange 16 is thermally insulated from the heat emitted from the surface 9, since there is a space 40 between the annular surface 39 and the inner sleeve 10, or a recess in the cylinder of the inner sleeve 10. So that the bonded joint does not become overheated.

While various embodiments are illustrated and described herein, it will be understood that the invention is not limited to these embodiments. Modifications to those skilled in the art are not difficult. Accordingly, the above illustration and description are not to be taken in a limiting sense.

Claims (15)

1. A water heater, particularly for motor vehicles, having a burner and a combustion chamber, the burnt gases being discharged from the combustion chamber and then diverted into a gas space, flowing along a heat exchanger to an exhaust port provided in the burner, the heat exchanger having an annular space which is formed by an outer shell and an inner shell made of metal, the outer shell and the inner shell having flanges, said annular space having a flow-limiting internal spiral ribbed baffle and having a water feed opening and a water discharge opening, water as a heat exchange medium being introduced into and discharged from the water feed opening and the water discharge opening, characterized in that: the outer shell (11) is made of plastic, and the connection between the inner sleeve (10) and the outer shell (11) is airtight, pressure-resistant and capable of maintaining a stable connection during temperature changes.

2. The water heater of claim 1, wherein: the airtight seal formed by the metal inner sleeve (10) and the flanges (16, 17) of the plastic housing (11), which is pressure resistant and can maintain a stable connection during temperature changes, is completed by a threaded connection (21) and is fitted with an O-ring (25).

3. The water heater of claim 1, wherein: the metal inner sleeve (10) and the flanges (16, 17) of the plastic shell (11) form a hermetic seal, resist pressure and can keep stable connection in the temperature change process, and the bonding is realized.

4. The water heater of claim 1, wherein: the metal inner sleeve (10) and the flanges (16, 17) of the plastic housing (11) form a gas-tight, pressure-resistant and stable connection during temperature changes, and an injection-molded sleeve (29) is used to form the housing.

5. The water heater of claim 1, wherein: the metal inner sleeve (10) and the flanges (16, 17) of the plastic shell (11) form an airtight and pressure-resistant connection which can be kept stable in the temperature change process, and a riveting connection (32) is adopted.

6. A water heater according to any one of claims 2 to 5, wherein: the contact surface (36) of the connection region of the metal inner sleeve (10) and the plastic outer sleeve (11) is provided with a sealing layer (37).

7. The water heater according to claim 1, characterized in that the baffle in the form of a flow-limiting internal helical rib (12) is injection-molded onto the inner surface (13) of the metal housing (11).

8. The water heater of claim 1, wherein: the water supply and drainage components (14, 15) are moulded onto the plastic housing (11).

9. The water heater of claim 1, wherein: the water supply and drainage elements (14, 15) are manufactured separately and mounted on the metal-plastic shell (11) by any of the joining methods mentioned in claims 2 to 6.

10. A water heater according to claim 8 or 9, wherein: the water supply and discharge elements (14, 15) are connected to the metal connecting piece.

11. The water heater of claim 1, wherein: for supporting and securing the wires, heater 1 and/or other accessories such as thermostats, a cable trough (19) is molded into the outer surface (18) of the plastic housing (11).

12. The water heater of claim 1, wherein: on the flange (16) of the inner sleeve (10) there is an annular part (38) or an annular surface (39) enabling the plastic housing (11) to be glued parallel along the longitudinal axis of the heater (1).

13. The water heater of claim 12, wherein: the annular member (38) is a separate member welded to the inner sleeve (10).

14. A water heater according to claim 12 or 13, wherein: a space is present between the annular surface (39) and the outer surface of the inner sleeve (10), which space is provided for thermal insulation.

15. The water heater of claim 3, wherein said metal inner sleeve and said plastic outer shell are bonded together with an adhesive.

Images