GB2067723A

GB2067723A - Thermally sensitive control valve

Info

Publication number: GB2067723A
Application number: GB8101315A
Authority: GB
Original assignee: Honda Motor Co Ltd; Fuji Thomson Co Ltd
Current assignee: Honda Motor Co Ltd; Fuji Thomson Co Ltd
Priority date: 1980-01-17
Filing date: 1981-01-16
Publication date: 1981-07-30
Also published as: FR2474129A1; CA1155432A; DE3101248C2; DE3101248A1; JPS56101471A; GB2067723B; FR2474129B1; JPS5947186B2

Abstract

A thermostat valve has a thermally sensitive bulb 17 mounted to move axially within a frame 10 having a stationary seat 14. A movable valve element 27 has sliding contact with the seat 14. Cooperating surfaces 33, 24 on the valve element 27 and the casing 18 of the bulb 17 serve to prevent flow between the surfaces when the bulb temperature is below a first predetermined value. When the bulb temperature rises above that value a leakage path is opened between those surfaces, and when the bulb temperature reaches a second higher predetermined value the valve element 27 is moved by contact with an arm 35 carried by the casing away from the seat 14 to permit a greater rate of flow. <IMAGE>

Description

SPECIFICATION Thermally sensitive control valve This invention relates to a thermally sensitive control valve, particularly but not exclusively for use in controlling the flow and thereby the temperature of cooling water in a water-cooled internal combustion engine or the like.

A conventional valve of this kind generally includes an auxiliary valve having a small valve port which opens when the temperature of a thermally sensitive bulb is raised to a first predetermined value. The conventional valve assembly also includes a main valve having a large valve port which opens when the cooling water temperature is further elevated to a second and higher predetermined value. In such a construction, it is possible to prevent hunting of the valve which can occur due to fluctuations in the pressure on the upstream and downstream sides of the valve produced by sudden opening of the valve when the thermally sensitive bulb is actuated to open the valve upon its sensing a certain level of cooling water temperature. It is also possible to prevent an increase in the actual valve-opening temperature.

However, in the above conventional valve, the main valve and the auxiliary valve are formed in separate bodies, which results in complexity of the valve structure as well as in inaccuracy of the flow rate control.

An object of this invention is to eliminate the above-mentioned disadvantages, and to provide a thermally sensitive valve in which the main valve also serves per se as the valve or valve seat of the auxiliary valve, whilst the casing of the thermally sensitive bulb also serves per se as the valve or valve seat of the auxiliary valve, thereby providing a simplified structure which is capable of performing flow rate control with higher accuracy.

Thus according to the invention there is provided a thermally sensitive control valve comprising a frame having a stationary seat, a thermally sensitive bulb having an axially movable casing positioned within the frame, a movable valve element encircling a portion of said thermally sensitive bulb and having axial sliding contact with said stationary seat, a surface on the movable valve element being engageable with a surface of said casing to close a leakage path, resilient means acting on said casing to hold said surfaces in contact to prevent flow therebetween, and a valve engaging member fixed to a portion of said casing, the casing moving in a direction to open a leakage path between said surfaces when the temperature of said thermally sensitive bulb reaches a first predetermined level, the movable valve element remaining closed against the stationary seat during movement of said casing to open the leakage path, and said valve engaging member being adapted to separate said movable valve element from said stationary seat when the temperature of the thermally sensitive bulb reaches a second and higher pre-determined level.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is an axial cross-sectional view of a thermally sensitive control valve according to this invention; and Figure 2 is a top plan view of the valve.

Referring to the drawings, the valve comprises a frame generally designated 10 and including a flat annular ring 11, a retainer 12, and a strap 13, all fixed together against relative movement. Fixed to the inner boundary of the ring 11 is a stationary cylindrical seat 14 having an axially extending inner surface 1 5. A supporting shaft 1 6 is fixed to the strap 1 3 and projects slidably into the interior of a thermally sensitive bulb 1 7. The bulb 1 7 has a casing 1 8 with a cylindrical portion 19 positioned to slide axially within a central opening 21 in the lower end of the retainer 1 2.The casing 1 8 has an enlarged portion 22 above the cylindrical portion 1 9 and this enlarged portion 22 has a conical surface 23 on its lower portion and a convex curved surface 24 on its upper portion. The casing 1 8 contains a crystalline wax of a type which expands when its temperature is raised above a predetermined critical point.

A spring seat 25 encircles the thermally sensitive bulb 17 and has a portion which engages the conical surface 23. A main spring 26 has a lower end which engages the lower portion of the retainer 12 and an upper end which supports the spring seat 25.

A movable valve element 27 encircles a portion of the thermally sensitive bulb 17 and includes a metallic ring 28 having an outer periphery 38 which underlies the cylindrical seat 14. A cover sheet 29 is positioned on the upper surface of the metallic ring 28 and has a downward extending lip 31 which slides within the axially extending inner face 1 5 of the cylindrical seat 14. An annular disk 32 underlies the metallic ring 28 and is provided with a concave curved surface 33 which conforms to the convex curved surface 24 on the casing 18.

Both the cover sheet 29 and the annular disk 32 are made from rubber or synthetic resin. An auxiliary spring 34 extends between the annular disk 32 and the spring seat 25. A valve engaging member in the form of a disk plate 35 is fixed to the casing 18 near its upper end and is provided with a downward extending peripheral rim 36.

Small openings 37 are provided at the juncture of the disk plate 35 and its rim 36 to permit flow of liquid through the openings under certain conditions, as described below.

Flow of coolant through the valve assembly occurs from the bottom to the top as viewed in Figure 1 of the drawings. When the temperature of the coolant reaches a first predetermined level, the casing 1 8 of the thermally sensitive bulb 1 7 moves axially in a downward direction, causing the convex curved surface 24 on the casing to move away from the concave curved surface 33 to a slight extent. This latter movement is limited by contact between the downward extending rim 36 on the disk plate 35 and the cover sheet 29 of the movable valve element 27. A small flow of coolant then passes between the surfaces 24 and 33, through the central opening 39 in the movable valve element 27, and through the small openings 37 in the disk plate 35.

When the temperature of the coolant reaches a second and higher predetermined value, the casing 18 of the thermally sensitive bulb 17 moves further in a downward direction to cause the disk rim 36 to move the movable valve element 27 against the force of the main spring 26, the lower end of the casing 18 moving through the opening 21 at the lower end of the retainer 12. This movement causes the cover sheet 29 of the movable valve element 27 to slide within the surface 1 5 of the seat 14 until it is completely clear of the seat 14. A greater flow of coolant may then pass under the cylindrical seat 14 and above the cover sheet 29. Subsequent loss of temperature in the coolant causes the thermosensitive bulb 17 to contract axially, urged by the main spring 26.The movable valve element 27 closes first in contacting the cylindrical seal 14, and the leakage path between the surfaces 24 and 33 closes when upward motion of the movable valve element 27 is arrested by contact between the lower edge of the cylindrical seat 14 and the outer periphery 38 of the metallic ring 28.

It will be noted that the cylindrical valve seat 14 has a predetermined substantial length in the moving direction of the valve element 27.

Accordingly, before the valve element can move to open position, it must be moved through a predetermined substantial axial distance.

Therefore; to open the main valve the coolant temperature must be continuously maintained at values above a predetermined temperature. This feature overcomes the disadvantage of a conventional thermally sensitive control valve in which the main valve element is not moved over such a predetermined substantial distance, resulting in fluctuations in the coolant temperature which cause repeated opening and closing of the main valve, which is turn causes fluctuations in the flow rate of collant passing through the main valve. This latter action may result in objectionable hunting of the main valve.

Claims

1. A thermally sensitive control valve comprising a frame having a stationary seat, a thermally sensitive bulb having an axially movable.

casing positioned within the frame, a movable valve element encircling a portion of said thermally sensitive bulb and having axial sliding = contact with said stationary seat, a surface on the movable valve element being engageable with a surface of said casing to close a leakage path, resilient means acting on said casing to hold said surfaces in contact to prevent flow therebetween, and a valve engaging member fixed to a portion of said casing, the casing moving in a direction to open a leakage path between said surfaces when the temperature of said thermally sensitive bulb reaches a first predetermined level, the movable valve element remaining closed against the stationary seat during movement of said casing to open the leakage path, and said valve engaging member being adapted to separate said movable valve element from said stationary seat when the temperature of the thermally sensitive bulb reaches a second and higher predetermined level.

2. A valve as claimed in claim 1, in which a spring seat contacts said casing, said resilient means comprising a main spring extending between said frame and said spring seat, and an auxiliary spring interposed between said spring seat and said movable valve element.

3. A valve as claimed in claim 1 or 2, in which said valve engaging member is a disk plate having openings therein for passage of liquid moving through said leakage path.

4. A thermally sensitive control valve substantially as hereinbefore described with reference to the accompanying drawings.