Temperature responsive flow control valve apparatus

Abstract: A temperature responsive valve particularly adapted for use in a manual valve of a vehicular automatic transmission control is shown in which the temperature responsive valve has a generally cylindrical housing with a reduced diameter section and a cylindrical valve element rotatably received in the reduced diameter section. A thermostatic coil is coupled to the valve element to control the angular position of the valve element. Apertures are provided in both the housing and the valve element forming a variable orifice for pneumatic fluid which flows into an open end of the housing and out of a minimum fixed orifice in the reduced diameter section and, depending on the temperature, may also flow through the variable orifice.

Description: This invention relates generally to hydraulic control systems and more specifically to a temperature responsive flow control valve that can be used to modify the operation of a manual control valve. In automotive automatic transmissions it is conventional to use a torque convertor to couple engine power to the gear train through oil dependent upon the position of the transmission selector lever. Typically the transmission quadrant has six positions including P (park), R (reverse), N (neutral), D (drive), I (intermediate) and L (low). The selector lever is mechanically coupled to a manual valve which is adapted to bring various hydraulic lines into and out of comunication depending on the position selected. For example, when the transmission selector lever is moved to the drive position the manual valve moves to allow line pressure to be delivered to the forward clutch. The oil is metered to the forward clutch piston through an orifice to provide a smooth application of the clutch. However, as the transmission fluid warms up and becomes less viscous, the fluid flow becomes excessive and causes uneven shifting. This is particualrly noticeable when shifting from reverse to drive. In US-A-4,502,627, assigned to the assignee of the present invention, a temperature responsive flow control valve for use in a transmission is disclosed and claimed which compensates for temperature change to maintain fluid flow at a constant level and thereby provide smooth shifting. The flow control valve comprises a base having a first orifice of a selected minimum area and second parallel passageway in the form of an elongated slot oriented to lie along an arc of movement of a thermostat metal element carrying a flag which slides on the base so that very small angular movement of the element causes the flag to cross over the entire width of the slot shaped orifice making adjustments in the effective orifice size as the temperature varies between two reference points. Although this valve mechanism is very effective its physical configuration is such that it can be used only in certain locations. That is, the arrangement of parts makes it unsuitable for use in small cylindrical passageways, for example. US-A-3 008 697, on which the preamble of claim 1 is based, discloses a thermostatic valve used in the fuel supply of a carburettor. The valve has a cylindrical housing with its upper end open into a fuel reservoir and a reduced-diameter portion at its lower end in the output passage from a fuel pump. A rotatable valve member within the reduced-diameter portion has a passage the ends of which can be rotated into and out of alignment with ports in the wall of the reduced-diameter portion to form the actual valve. The middle of the passage is in communication through another passage with the open end of the housing. Within the housing is a bimetallic helical coil of which one end is fixed round the valve member and the other end is fixed in the open end of the housing. The valve is closed at low fuel temperatures but is opened at higher temperatures to allow part of the fuel from the pump to return to the reservoir. GB-A-1 111 585 discloses a thermostatic valve for controlling the gas supply to a gas-fired water heater or the like. A valve member or valve operating arm projects from a spindle, which lies co-axially within a thermostatic helical coil. The end of the coil nearer the valve is fixed to a support, while the other end is stated to be attached to the spindle. The helical coil is disposed within a closed cylindrical housing that projects into the water the temperature of which is to be regulated. There are many existing transmission systems which have fixed control orifices and which therefore are adversely affected by temperature variations. It is an object of the present invention to provide a temperature responsive flow control valve which can be used with transmission systems without requiring a change in design and tooling for the transmission housing. It is another object of the invention to provide a temperature responsive valve which can be placed within a passageway of a manual valve currently used in transmission systems. Yet another object is the provision of an inexpensive yet reliable temperature responsive valve. Other objects and features of the invention will become more readily understood from the following detailed description and appended claims when read with the accompanying drawings in which like reference numerals designate like parts throughout the figures thereof. The invention provides a temperature-responsive flow-control valve comprising a generally cylindrical housing having an open first end and a second end, the housing having a reduced-diameter portion that extends from the second end and has an aperture through it; a valve element that fits closely within the reduced diameter portion of the housing and has through it an aperture that is in communication with the interior of the housing and is in alignment lengthwise of the valve with the said aperture in the housing, the two apertures together forming a variable orifice; and a thermostatic helical coil disposed within the housing and having one end so connected to the housing and the other so connected to the valve element that expansion and contraction of the helical coil as the temperature changes causes the valve element to rotate, varying the size of the said variable orifice; characterised in that the valve element has an end wall and a side wall, in that a shaft is fixed to the end wall and extends along the axis of the housing essentially to the open end of the housing and is supported by a bracket disposed in the open end of the housing, and in that the helical coil has one end fixed to the shaft and has a tab at the other end attached to the bracket by means so constructed as to prevent rotation of the tab round the axis while permitting radial movement of the tab as the coil expands and contracts. The bracket preferably has a central bearing portion with a pair of tabs extending therefrom in an outwardly direction relative to the housing and fixedly secured thereto. A pair of fingers preferably extend from the central bearing portion in an inward direction relative to the housing and lie in a first plane which is parallel to the longitudinal axis of the cylindrical housing. A third finger, between the pair, then extends from the central bearing portion in the inward direction and lies in a second plane parallel to the first but spaced therefrom a distance slighlty greater than the thickness of the tab, which is advantageously flat, extending from the end of the thermostatic helical coil. The coil is attached to the bracket by having the tab received in the space between the fingers so that its angular position is fixed but it is free to move radially outwardly and inwardly as the thermostatic coil expands and contracts with changes in temperature. Another aperture is preferably formed in the reduced diameter section, out of alignment with the valve element, to serve as a fixed orifice to provide a selected minimum control orifice. The variable orifice then provides a path in parallel with the fixed orifice, with a variable controlled cross sectional area at temperatures below a selected level. Embodiments of the invention include a valve arrangement comprising a cylindrically-shaped passageway having a temperature-responsive flow-control valve according to the invention received and closely fitting within the passageway, and a vehicular automatic transmission control in which a manual valve member that comprises such a valve arrangement is movably positionable among different locations to bring selected pneumatic lines into and out of communication with each other. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic representative of an automotive transmission control including the quadrant, manual valve, temperature responsive flow control valve, forward clutch and pneumatic lines; Fig. 2 is a cross section view taken along the longitudinal axis of the temperature responsive flow control valve, Fig. 2a is a back elevational view of a portion of the Fig. 2 valve, Fig. 3 is a left side view of the Fig. 2 valve, Fig. 4 is a right side view of the Fig. 2 valve, Fig. 5 is an enlarged side view of a bracket shown in Figs. 2 and 3, and Fig 6 is a top plan view of the bracket of Fig. 5. DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to Fig. 1 an automatic transmission control utilizing a temperature responsive flow control valve made in accordance with the invention is schematically shown. A quadrant 2 having six positions: park (P), reverse (R), neutral (N), drive (D), intermediate (I) and low (L) is shown in the neutral position. The manual selector level 4 is coupled to a manual valve 10 which controls communication among hydraulic lines such as drive and line passages and forward clutch 16 schematically shown in the figure by virtue of its axial position in bore 20 of casing 22. Manual valve 10 is formed with bores 12, 14 an open end 17 and an intermediate passage 18 therebetween for passage of hydraulic fluid therethrough. A temperature responsive flow control valve 30 is disposed within intermediate passage 18 locked therein by lock washer 24 and is adapted to permit the passage of hydraulic fluid as will be explained in detail below. As seen in Figs 2-4, valve 30 comprises a generally cylindrical housing 32 having a diameter such that the valve closely fits within passage 18. Housing 32 has an open end 34 at one end and a reduced diameter section 36 at its opposite end culminating at end wall 37. A generally cup shaped valve element 38 having an end wall 39 and a cylindrical horizontal axis coincident with the horizontal axis of cylindrical housing 32 is slidingly received in section 36 and is adapted to rotate around its horizontal axis as will be explained below. A shaft 40 extends essentially the entire length of housing 32 and has a head portion 42 formed at one end thereof which is fixedly connected to end wall 39 in any suitable manner, as by welding at 44 (Fig. 2). The opposite end of shaft 40 is supported by a bracket 50. Bracket 50 is formed with a bearing section 52 formed with a bore 54 adapted to receive shaft 40 and a pair of parallel disposed tabs 56 extending in a first direction towards open end 34 from opposite lateral ends of bearing section 52. Tabs 56 are fixedly attached to housing 32 in any suitable manner, as by welding at 58 (Fig. 3) to mount shaft 40 with wall 39 of valve element 38 contiguous with end wall 37. An aperture 60 is preferably provided in end wall 37 to allow air to escape when valve element 38 is inserted in section 36. Bracket 50, in addition to supporting an end of shaft 40 also mounts one end of a thermostatic element 62. Thermostatic element 62 is formed into a helix with one end 64 formed into a flat tab portion fixedly attached to shaft 40 in a conventional manner, as by welding at 66 and an opposite end 68 formed into a flat tab portion fixedly mounted to bracket 50 with regard to its angular position but slidingly received with regard to movement inwardly and outwardly in a radial direction. A pair of fingers 70 extend from bearing section 52 in a second direction towards end wall 37, opposite to the direction tabs 56 extend, and lie in a first plane parallel to the horizontal axis of shaft 40. A third finger 72 extends from section 52 in the second direction and lies in a second plane parallel to the first plane but spaced therefrom a distance slightly greater than the thickness of tab portion 68 of thermostatic element 62. This arrangement allows radial sliding motion and eschews skewing forces from being placed on cup shaped element 38 which would tend to bind the element and cause erratic sliding motion. A first generally rectangular valve aperture 74 is formed in the side wall of reduced diameter section 36 and a second generally rectangular valve aperture 76 is formed in the side wall of valve element 38. The length of aperture 76 in the direction of the longitudinal axes is preferably slightly longer than the corresponding length of aperture 74 to facilitate providing a consistent opening from one device to the next in the event of a slight misalignment in the axial direction. The combination of apertures 74, 76 results in a variable orifice the size of which is dependent upon the angular position of shaft 40. This in turn is dependent upon the temperature of the thermostatic element 62 which expands or contracts as its temperature changes. Such expansion or contraction causes rotational movement of shaft 40 and concomitantly valve element 38. In a device made in accordance with the invention, the thermostatic element and the sizes of the apertures 74, 76 were chosen so that the variable orifice is fully closed at 45°C (110°F) and remains closed up to 200°C (400°F), the variable orifice is fully opened at -18°C (0°F) and remains open down to minus 40°C (-40°F). In order to provide a minimum size passageway a separate bore 78 is provided in the reduced diameter portion 36 spaced from valve element 38 in the direction of the horizontal axis. Thus pneumatic fluid enters open end 34 of valve 30 and passes through fixed orifice 78 into passage 18 and, depending on the temperature of the fluid, through the variable orifice formed by apertures 74, 76. A valve made in accordance with the invention has a housing 30 and valve element 38 both formed of type 305 stainless steel 0.25mm (0.010 inch) in thickness. Shaft 40 is formed of type 430 stainless steel and bracket 50 is formed of type 304 stainless steel 0.3mm (0.012 inch) thick. The length of valve 30 is 40mm (1.575 inches) and the outer diameter 8.52mm (0.3355 inch) and the outer diameter of the reduced diameter section 36 is 7.09mm (0.279 inch). Clearance between reduced diameter section 36 and valve element 38 is 0.125mm (0.005 inches). Bore 78 comprising the fixed orifice is 2.18mm (0.086 inch) in diameter. The vertical heights, as shown in Fig. 2 of aperture 74 in housing 32 is 2.59mm (0.102") and of aperture 76 in valve element 38 is 3.61mm (0.142") while the widths in direction of the longitudinal axis of the housing and element are 4.09mm (0.161") and 4.60mm (0.181") respectively. The thickness of the flat tabs is 0.2mm (0.008 inch) while the space between the planes in which fingers 70, 72 lie is 0.24mm (0.0095 inch). Although the invention has been described with respect to a specific embodiment, variations and modifications will become apparent to those skilled in the art.

Claims: A temperature-responsive flow-control valve comprising a generally cylindrical housing (32) having an open first end (34) and a second end, the housing having a reduced-diameter portion (36) that extends from the second end and has an aperture (74) through it; a valve element (38) that fits closely within the reduced diameter portion of the housing and has through it an aperture that is in communication with the interior of the housing and is in alignment lengthwise of the valve with the said aperture (74) in the housing, the two apertures together forming a variable orifice; and a thermostatic helical coil (62) disposed within the housing and having one end (68) so connected to the housing and the other (64) so connected to the valve element that expansion and contraction of the helical coil as the temperature changes causes the valve element to rotate, varying the size of the said variable orifice; characterised in that the valve element (38) has an end wall and a side wall, in that a shaft (40) is fixed to the end wall and extends along the axis of the housing (32) essentially to the open end (34) of the housing and is supported by a bracket (50) disposed in the open end of the housing, and in that the helical coil has one end (64) fixed to the shaft and has a tab (68) at the other end attached to the bracket by means (70,72) so constructed as to prevent rotation of the tab (68) round the axis while permitting inward and outward movement of the tab as the coil (62) expands and contracts. A temperature-responsive flow control valve as claimed in claim 1, wherein there is an aperture (78) in the reduced-diameter portion (36) of the housing (32) providing a minimum fixed orifice. A temperature-responsive flow control valve as claimed in claim 1 or claim 2, wherein the bracket (50) has a central bearing portion (52), a shaft receiving bore (54) formed in the central bearing portion, a pair of tabs (56) extending in a first direction from the central bearing portion, the tabs fixedly connected (58) to the open end portion (34) of the housing (32), a pair of fingers (70) extending from the central bearing portion (52) in a second direction opposite to the first direction and lying in a first plane parallel to the longitudinal axis of the cylindrical housing, a third finger (72) between the pair of fingers (70), extending from the central bearing portion in the second direction and lying in a second plane parallel to the first plane, the first and second planes being spaced apart a distance slightly greater than the thickness of the tab (68) on the helical coil. A valve arrangement comprising a cylindrically-shaped passageway (20) having a temperature-responsive flow-control valve as claimed in any one of claims 1 to 3 received and closely fitting within the passageway. A vehicular automatic transmission control in which a manual valve member (10) is movably positionable among different locations (2) to bring selected pneumatic lines into and out of communication with each other, wherein the manual valve member comprises a valve arrangement as claimed in claim 4.

Inventors: TY HENRY, TY, HENRY
Applicants: TEXAS INSTRUMENTS INC, TEXAS INSTRUMENTS INCORPORATED
Application year: 1988
Main classification: G05D23
IPC codes: F16H59, G05D23, F16H61, F16K31