Fan drive clutch for internal combustion engine

Abstract: A viscous-fluid fan-drive clutch for an internal combustion engine has a housing (3) divided into reservoir (8) and working chambers (9) by a pump plate (7) with an opening (12) slidably coverable by valve plate (23) elastically connected to the valve arm (21) by narrow connecting portion (24) of a slant plate (22). Resistance to the valve plate (23) lifting from the plate (7) may be enhanced by radially inward portions (25).

Description: The present invention relates generally to a fluid clutch, and especially to a fan drive clutch for an internal combustion. More specifically, the invention relates to a temperature sensitive type fan drive clutch including a fluid coupling for controlling the rotational speed of a fan. Use of temperature-sensitive fan-drive clutches in automotive cooling systems is well known in the art. This type of fan-drive clutch generally includes a fluid coupling that couples a drive shaft with a clutch housing on which a fan is disposed. The fan is operated according to the air temperature required by an automotive radiator. The fluid coupling allows the fan to rotate, blowing air into the radiator. The fan drive clutch is arranged to control the rotational speed of the fan so as to increase the fan speed when engine cooling requirements are severe and to drop the fan speed when the engine cooling requirements are low. Internally, the fluid coupling is provided with a pump plate for defining a fluid reservoir chamber and a working chamber, a clutch plate, a valve arm, and a bimetallic coil for controlling the movement of the valve arm. The clutch plate has labyrinth grooves in its outer end section for engaging with corresponding labyrinth grooves formed in the inner wall of the housing. The pump plate has a hole through which working fluid can pass from the reservoir chamber to the working chamber. The valve arm includes a valve plate for opening and closing that hole to control the flow rate of the working fluid from the reservoir chamber into the working chamber. The valve arm is rotatably attached to the clutch housing by means of a shaft which is inserted into a bearing hole provided in the clutch housing. The bimetallic coil is connected to the valve arm by means of the shaft passing through the bearing hole and is operable to move the valve arm so as to slide it according to variations in the temperature of the air passing through the radiator. This action causes the through hole in the pump plate to be opened and closed, the working fluid thereby flowing into the working chamber. The more working fluid is supplied into the labyrinths to couple the drive shaft with the clutch housing, the more torque from the drive shaft is transmitted to the clutch housing, and the higher the fan speed becomes. Conventional fan drive clutches usually require location of the valve plate as close to the pump plate as possible in order to close the through hole hermetically. However, in a conventional clutch, a certain clearance is provided between the shaft for supporting the valve arm and the bearing hole formed in the clutch housing on account of the assembly tolerance required. Thus, when the shaft moves within the clearance, the valve arm tends to swing according to the motion of the shaft. For example, the top edge of the valve plate can be forced against a surface of the pump plate, while the opposite edge thereof is lifted from the surface of the pump plate causing a relatively large gap to occur. As a result, the working fluid in the reservoir chamber flows into the working chamber through the gap and the through hole. The working pressure within the working chamber is therefore increased. As a result, even when engine cooling requirements are low, some torque from the drive shaft tends to be transmitted to the housing, causing the fan to rotate. Thus, the radiator can be overcooled during engine warm-up. EP-A-0 045 037, on which the preamble of claim 1 is based, discloses a fan clutch generally similar to the conventional clutches described above, but in which the valve arm is spring-biased into the closed position and the valve is opened by a solenoid that pulls the valve arm axially into frictional engagement with the end of the rotating drive shaft. In order to keep the valve plate in contact with the pump plate while accommodating the axial movement, it is resiliently biased by an S-shaped curved portion of the valve arm. EP-A-0 130 024 discloses a fan clutch with a solenoid-operated valve in which the valve plate engages a flat area on a cylindrical surface. The solenoid causes axial movement of the valve arm and axial sliding movement of the valve plate to open and close the valve. The valve plate is mounted on the valve arm by a pair of obliquely-extending support members integrally connected with the valve plate near the middle of each axially-extending side. It is an object of the present invention to provide a fan drive clutch wherein even if a fluid valve plate swings, no clearance occurs between the fluid valve plate and the pump plate. In this way, hermetic sealing of the opening which communicates between the fluid reservoir chamber and the working chamber can be maintained. The invention provides apparatus for coupling a first member with a second member connected to a drive source, comprising: a plate for defining a fluid reservoir chamber and a working chamber, said plate having an opening for fluid communication therethrough so as to allow a working fluid to flow from the fluid reservoir chamber into the working chamber; a valve including a valve arm and a valve plate, the valve arm being supported by the first member via supporting means so that said valve plate slidably contacts a surface of said plate so as to open and close said opening; fluid coupling means, provided within the working chamber, for coupling the first member with the second member to transmit torque from the drive source to the first member through the second member in accordance with variations in the amount of working fluid within the working chamber due to the opening and closing of said valve plate; and absorbing means for absorbing vibrations transmitted via the valve arm from the supporting means to the valve plate; characterised in that the valve plate includes a pair of extending portions, each being integrally connected to an edge of the valve plate so as to extend in a direction opposite a portion corresponding to said opening with respect to a position at which the valve plate is connected to the valve arm. The vibration-absorbing means may be an elastic member connecting the valve plate to the valve arm so as to be elastically deformed by vibration of the valve arm to maintain the valve plate in contact with the surface of the plate without any clearance therebetween. The elastic member may be in the form of a strip plate having a width narrower than that of the valve arm. One form of fan-drive clutch which is apparatus for coupling a first member with a second member constructed in accordance with the invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is a cross sectional view of a fan drive clutch; Fig. 2 is a front view of a valve arm for the fan-drive clutch shown in Fig. 2; Fig. 3 is a side view of the valve arm shown in Fig. 2 and a clutch plate; and Fig. 4 is a partially cut-out front view of the fan drive clutch shown in Fig. 1. Referring now to the drawings, and initially to Fig. 1, a fan drive clutch according to the present invention is shown which includes a fluid coupling filled with a special silicone oil or so forth as a working fluid. This fan drive clutch generally includes a clutch housing 3, a pump plate 7, a shaft 14, and a valve arm 21. On the circumference of the housing 3, a fan 5 for blowing air to cool a radiator (not shown) as installed. A drive shaft 1 is rotatably supported by the clutch housing 3 via ball bearings 4. A V-belt pulley 2 is mounted on one end of the drive shaft 1, while a clutch plate 6 is installed firmly on the other end of the drive shaft within the housing 3. The clutch plate 6 has labyrinth grooves 10 are its outer section. On the inner wall of the clutch housing 3, at a portion corresponding to the labyrinth grooves 10, as formed labyrinth grooves 11 interleaving with labyrinth grooves 10. These labyrinths 10 and 11 function as a fluid coupling by the viscous resistance of the working fluid. The pump plate 7 is disposed within the clutch housing 3 to define a working chamber 9 and a fluid reservoir chamber 8. The pump plate 7 has an opening 12 elongate in the radial direction for allowing the fluid to pass therethrough from the reservoir chamber 8 into the working chamber 9. In the center of the clutch housing 3, a hole 3b is provided as a bearing. The shaft 14, on one end of which the valve arm 21 is installed, is inserted into the bearing hole 3b. A bimetallic coil 13 is mounted on the other end section of the shaft 14. The bimetallic coil 13 is operable to rotate the valve arm 21 in accordance with the changing temperature of air which has passed through the radiator. This action causes the opening 12 to be opened and closed as shown in Fig. 4, thereby controlling the communication betweeen the working chamber 9 and the fluid reservoir chamber 8, that is, the amount of oil in the fluid coupling. When engine cooling requirements are severe, as during high-temperature, high-speed operation, more oil is injected into the fluid coupling from the reservoir chamber through the opening 12. This action increase the amount of engine torque transmitted to the coupling. Fan speed therefore increases. When engine cooling requirements are low, as during low-temperature, intermediate-speed operation, oil is withdrawn from the fluid coupling through a return fluid path 18, subsequently less power passes through the coupling and fan speed is reduced. Referring to Figs. 2 and 3, there is illustrated the valve arm 21 of the fan drive clutch shown in Fig. 1. This valve arm 21 is provided with a slant plate 22 bent toward the pump plate and a valve plate 23 for opening and closing the opening 12. The slant plate 22 includes a connecting plate 24 of narrower width than the valve plate 23. The valve plate 23 is substantially rectangular in shape and is integrally connected to an end of the slant plate 22 via the connecting plate 24 so as to be arranged parallel to the surface of the pump plate 7. The connecting plate has a width about 2 to 3 (mm) narrower than that of the slant plate 22 so as to be elastically deformable. On the two sides of the end of the valve plate 23 towards the shaft 14, a pair of extending portions 25 are formed integrally with the valve plate 23. The extending portions 25 extend toward the slant plate and lie in the plane of the valve plate 23. The extending portions 25 extend on either side of the connecting plate 24, and the connecting plate is also integrally formed with the valve plate 23 and extends between the extending portions 25 at an angle from the plane of the valve plate 23. The width of the connecting plate 24 flares at a predetermined point along its length to form the tapered slant plate 22. With conventional valve arms, if while operating the shaft 14 moves within a clearance occurring because of a tolerance between the bearing hole 3b and the shaft 14, the valve arm tends to vibrate, slapping back and forth against the pump plate 7. In such a case, the valve arm 21 shown in Figs. 2 and 3, through the spring action thereof, forces the connecting portion 24a, which forms the border between the valve plate 23 and the connecting plate 24, against the surface 7a of the pump plate 7. Even when the connecting portion 24a is forced against the surfaces 7a, the top edge 23a of the valve plate 23 can be caused to lift away from the surface 7a by leverage caused by pressure against the lower edge of the connecting portion 23b. That lifting action is prevented through counter-leverage induced by the extending portions 25 via the elastic properties of the connecting plate 24 to prevent the edge 23a from lifting. In other words, movement or vibrations of the valve arm 21 are absorbed by the connecting plate 24. The entire surface of the valve plate 23 therefore maintains hermetic contact with the surface 7a. On the other hand, when the vibrations of the valve arm 21 are such that the bordering edge 23b is inclined to be lifted from the surface 7a the connecting plate 24 is deformed elastically. This deformation absorbs the movement of the valve arm 21 to maintain the contact of the valve plate 23 with the surface 7a without any clearance therebetween. It will be appreciated that the entire surface 23c of the valve plate 23 contacts the opposing surface 7a uniformly and hermetically regardless of the movement of the valve arm 21. This secure closing of the opening 12 by the valve plate 23 is achieved when the temperature of the air passing through the radiator is low enough that flow of working fluid from the reservoir fluid chamber 8 into the working chamber 9 is unnecessary. Thus, unnecessary rotation of the clutch housing 3 with the clutch plate 6 is prevented when engine cooling requirements are low. As is clear from the above, in the fan drive clutch for an internal combustion engine shown in the drawings, an elastically transformable narrow plate, or connecting plate, 24 is provided which is connected to the edge of the valve plate 23. A pair of extending portions 25 are also provided at either side of the connecting plate 24, extending in the plane defined by the valve plate 23. Therefore, by elastic deformation of the connecting plate 24, vibrations of the valve arm 21 are absorbed so as to maintain the valve plate 23 hermetically in contact with the pump plate 7. This hermetic contact enables the valve to seal the opening 12 without any clearance. As a result, overcooling caused by excessive rotation speeds of the clutch housing 3 during starting is prevented and subcooling of the radiator is avoided to improve engine performance during warm-up.

Claims: Apparatus for coupling a first member (5) with a second member (6) connected to a drive source (1), comprising: a plate (7) for defining a fluid reservoir chamber (8) and a working chamber (9), said plate having an opening for fluid communication (12) there-through so as to allow a working fluid to flow from the fluid reservoir chamber (8) into the working chamber (9); a valve including a valve arm (21) and a valve plate (23), the valve arm (21) being supported by the first member (5) via supporting means so that said valve plate (23) slidably contacts a surface of said plate (7) so as to open and close said opening (12); fluid coupling means (10, 11), provided within the working chamber (9), for coupling the first member (5) with the second member (6) to transmit torque from the drive source (1) to the first member (5) through the second member (6) in accordance with variations in the amount of working fluid within the working chamber (9) due to the opening and closing of said valve plate (23); and absorbing means (24) for absorbing vibrations transmitted via the valve arm (21) from the supporting means (14) to the valve plate (23); characterised in that the valve plate (23) includes a pair of extending portions (25), each being integrally connected to an edge of the valve plate (23) so as to extend in a direction opposite a portion corresponding to said opening (12) with respect to a position at which the valve plate (23) is connected to the valve arm (21). Apparatus as claimed in claim 1, characterised in that the vibration-absorbing means (24) includes an elastic member (22) connecting the valve plate (23) to the valve arm (21) so as to be elastically deformed by the vibrations to maintain the valve plate (23) in contact with a surface of said plate (7a) without any clearance therebetween. Apparatus as claimed in claim 2, characterised in that the said elastic member (22) is in the form of a strip plate having a width narrower than that of the valve arm.

Inventors: HARIMA TOSHIO ATSUGI MOTOR PAR, MATSUYA TATSUYUKI ATSUGI MOTOR, SATO KENICHI ATSUGI MOTOR PART, HARIMA, TOSHIO ATSUGI MOTOR PARTS COMP. LTD., MATSUYA, TATSUYUKI ATSUGI MOTOR PARTS COMP., SATO, KENICHI ATSUGI MOTOR PARTS COMP. LTD.
Applicants: ATSUGI UNISIA CORP, UNISIA JECS CORPORATION
Application year: 1989
Main classification: F16D35
IPC codes: F01P7, F16D35, F16K3