This application relates to and claims priority from Japanese Patent Application No. 11-89794 filed on Mar. 30, 1999, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates generally to heat exchangers, and is suitably applied to a radiator which radiates heat of coolant of a water-cooled engine of a vehicle into atmospheric air.
2. Related Art
JP-U-58-154389 discloses a radiator having plural metal tubes and a header tank communicating with the tubes. The header tank is formed by connecting a metal core plate and a resin tank body by clamping. The tubes are brazed to the core plate. Recently, recycling performance of vehicle parts such as a radiator is demanded to be improved for reducing industrial waste. However, since the above-mentioned radiator is made of at least two kinds of materials including metal and resin, parts of the radiator needs to be divided into metal parts and resin parts for recycling. Therefore, the number of processes for recycling the radiator is increased, and recycling performance of the radiator is low.
As shown in FIG. 20, when a header tank 520 of a radiator (not shown) is made of only metal with a relatively small rigidity or a relatively small Young""s modulus such as aluminum, the header tank 520 may not have a sufficient mechanical strength. As a result, the header tank 520 may be readily deformed by an internal pressure thereof to be expanded. Further, a connection portion of the header tank 520 to which a tube 511 is connected has a mechanical strength larger than that of a non-connection portion of the header tank 520 to which no tube 511 is connected. As a result, the non-connection portion of the header tank 520 may be intensively applied with stress and largely deformed.
Furthermore, as shown in FIG. 21, when the header tank 520 has a rectangular cross-section having a longer side ml and a shorter side m2, a longer-side wall of the header tank 520 has a larger area than a shorter-side wall of the header tank 520. Therefore, the longer-side wall is applied with a larger amount of the internal pressure of the header tank 520 than the shorter-side wall and may be largely deformed. Deformation of the header tank 520 may be restricted by increasing a thickness of a metal plate from which the header tank 520 is formed. However, in this case, a weight and a manufacturing cost of the radiator may be increased.
In view of the foregoing problems, it is an object of the present invention to provide a heat exchanger including a metal header tank having a sufficient mechanical strength without increasing a weight and a manufacturing cost of the heat exchanger.
According to the present invention, a heat exchanger has a plurality of metal tubes through which fluid flows, and a metal header tank disposed at a flow-path end of the tubes to extend in a direction perpendicular to a longitudinal direction of the tubes and to communicate with the tubes. The header tank includes first and second walls opposite each other. The first wall has a plurality of connection portions each of which is connected to each of the tubes. The second wall has a plurality of first reinforcement ribs which increase a rigidity of the header tank. The connection portions are arranged in the direction perpendicular to the longitudinal direction of the tubes at a first pitch. The first reinforcement ribs are arranged in the direction perpendicular to the longitudinal direction of the tubes at a second pitch approximately equal to the first pitch.
Therefore, a rigidity of a non-connection portion of the header tank to which no tube is connected is increased by the first reinforcement ribs, and stress is restricted from being intensively applied to the non-connection portion. As a result, a mechanical strength of the header tank is increased without increasing a thickness of a metal plate from which the header tank is formed, thereby restricting a weight and a manufacturing cost of the heat exchanger from increasing.
Preferably, the header tank is formed by connecting a first tank member and a second tank member each of which is formed by pressing to have a L-shaped cross-section so that the first and second tank members are formed using the same die.