Heating systems – Heat and power plants – Vehicle
Reexamination Certificate
1999-06-04
2001-03-27
Joyce, Harold (Department: 3744)
Heating systems
Heat and power plants
Vehicle
C122S026000, C126S247000
Reexamination Certificate
active
06206296
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a heater that generates heat by shearing viscous fluid. More specifically, the present invention relates to a method for securing a rotor for shearing viscous fluid to a shaft.
Various heaters that use the driving force of vehicle engines have been proposed as an auxiliary heater in a vehicle air conditioning system. Japanese Unexamined Patent Publication No. 10-217757 describes a heater that has a rotor and silicone oil, which are accommodated in a heating chamber defined in a housing of the heater. The rotor attached to a drive shaft is driven by an engine of the vehicle. When the driving force of the engine rotates the rotor, the silicone oil is heated from fluid friction. The heat of the oil is transferred to a coolant (heat transferring medium) in a heat transfer chamber adjacent to the heating chamber. Then, the coolant is sent to heating circuit and used for heating the passenger compartment.
In conventional heaters, the drive shaft is usually made of iron or iron alloy for its high hardness. On the other hand, the rotor is made of aluminum or aluminum alloy, which is light and easy to form. The coefficient of thermal expansion of aluminum or aluminum alloy is greater than that of iron or iron alloy. Therefore, when the rotor and the shaft are heated, the rotor expands more than the shaft, and this may loosen the fixation between them. If the rotor is not rigidly secured to the shaft, slipping occurs between them, thus lowering efficiency of heat generation. As a result, the heater may not generate enough heat for heating the passenger compartment. Usually, considering the difference of the thermal expansion between aluminum and iron, the rotor is formed to have interference with respect to the drive shaft. Furthermore, a thick boss is formed on the rotor to contact the drive shaft.
When attaching the rotor to the drive shaft, the following problems occurs.
When the predetermined interference between the rotor and the shaft is too small, the tightening force of the rotor against the drive shaft is weakened by heating. This causes slippage between the rotor and the drive shaft. Further, when using a cylindrical rotor, the space between the outer surface of the rotor and the inner wall of the heating chamber varies according to the temperature. To minimize the variation, the walls of the heating chamber are made of the same material as the rotor.
When the predetermined interference between the rotor and the drive shaft is too great, the force required to attach the rotor to the drive shaft is beyond the tension strength of the rotor, and this is likely to crack or break the rotor.
Thus, the interference between the rotor and the shaft must be determined very carefully, and the dimensions of the rotor must be strictly managed in manufacturing the rotor.
In particular, when positioning the rotor on the drive shaft relatively far from its ends, the rotor is more likely to crack or break. The rotor receives great resistance when being fitted to the drive shaft. The longer the distance from one end of the driveshaft to the target position, the more difficult it is to position the rotor. To facilitate the attachment of the rotor, lubricant is applied to the boss of the rotor. However, when the distance from the end of the drive shaft to the target position is long, the film of lubricant does not extend far enough, which may cause the rotor to break.
Another problem relates to the axial length of the part of the rotor contacting the drive shaft. The longer the length of contact is, the more likely it is that the force of the rotor against the drive shaft will vary axially. The part of the rotor having a stronger tightening force transmits the torque of the drive shaft. Therefore, the variation of the tightening force is likely to cause mechanical fatigue at the location where the stronger force is applied.
On the other hand, Unexamined Japanese Publication No. 9-323534 describes another heater having different means for preventing loosening of the rotor with respect to the drive shaft. In the heater of this Publication, the rotor includes an adapter that is fixed to the rotor with rivets. The adapter is joined to the drive shaft by splines. However, additional parts such as rivets are necessary to fix the adapter to the rotor. This increases the number of parts and the cost of the products.
SUMMARY OF THE INVENTION
The objective of the present invention is to provide a method for firmly fixing a rotor to a drive shaft, to provide a firmly fixed rotor and drive shaft assembly and a heater including such an assembly.
To achieve the above objective, the present invention provides a method for producing a rotor assembly of a heat generator. The rotor assembly includes an inner rotor and an outer rotor that is rotated integrally with the inner rotor. The producing method includes forming the inner rotor from iron or iron alloy, and casting the outer rotor around the inner rotor by aluminum or aluminum alloy.
The present invention further provides a rotor assembly for shearing viscous fluid to heat the viscous fluid in a heat generator. The heat generator has a housing and a heating chamber defined in the housing. The heating chamber accommodates the rotor assembly and the viscous fluid. The rotor assembly has an inner rotor and an outer rotor. The outer rotor is integrally attached with the inner rotor by casting. The inner rotor is made of iron or iron alloy. The outer rotor is made of aluminum or aluminum alloy, which has a thermal expansion coefficient greater than that of the iron or iron alloy.
The present invention further provides a heat generator for generating heat by shearing viscous fluid. The heat generator includes a housing, a heating chamber defined in the housing, viscous fluid accommodated in the heating chamber and a rotor assembly for shearing the viscous fluid to heat the viscous fluid. The rotor assembly includes an inner rotor and an outer rotor. The outer rotor is integrally attached with the inner rotor by casting. The inner rotor is made of iron or iron alloy. The outer rotor is made of aluminum or aluminum alloy, which has a thermal expansion coefficient greater than that of the iron or iron alloy.
REFERENCES:
patent: 4388042 (1983-06-01), Weber
patent: 4813342 (1989-03-01), Schneider et al.
patent: 5573184 (1996-11-01), Martin
patent: 5915341 (1999-06-01), Moroi et al.
patent: 6026767 (2000-02-01), Moroi et al.
patent: 6056520 (2000-05-01), Nguyen et al.
patent: 9-323534 (1997-12-01), None
patent: 10-217757 (1998-08-01), None
Ban Takashi
Hirose Tatsuya
Hoshino Tatsuyuki
Mori Hidefumi
Suzuki Shigeru
Boles Derek S.
Joyce Harold
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Morgan & Finnegan , LLP
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