US3727517A

US3727517A - Automatic speed control

Info

Publication number: US3727517A
Application number: US00120422A
Authority: US
Inventors: M Slavin; R Emery; R Carp; L Ang
Original assignee: Bendix Corp
Current assignee: Bendix Corp; Siemens Automotive LP
Priority date: 1971-03-03
Filing date: 1971-03-03
Publication date: 1973-04-17
Anticipated expiration: 1990-04-17
Also published as: CA950775A

Abstract

An automobile speed control system of the vacuum actuated type having a unitized housing embodying actuator, modulator, electronic components and inductive position feedback means. Electrical connections into the hermetically sealed expansible actuator, and noise caused by feedback potentiometer wear are eliminated. Valve means within the actuator are operated by magnetic forces generated externally to the actuator, thus eliminating electrical connections. The feedback means comprise a metallic body sealed in the actuator and movable therewith and an inductor external to the housing arranged so that its inductance will vary according to the position of the metallic body.

Description

United States Patent 1191 Slavin et al.

1 1 Apr. 17, 1973 AUTOMATIC SPEED CONTROL [73] Assignee: The Bendix Corporation, SouthfieId,Mich.

[22] Filed: Mar. 3, 1971 {21] Appl.No.: 120,422

[52] US. Cl. ..9l/36l, 91/457, 92/40 [51] Int. Cl. ..Fl5b 9/03, Fl5b 9/09 7 [58] Field of Search ..91/363 R, 361, 454,

[56] References Cited UNITED STATES PATENTS 3,477,346 1 1/1969 Slavin et al. 3,556,245 1/1971 Radin 3,572,214 3/1971 Woodword 9l/363 R Primary Examiner-Paul E. Maslousky Attorney-Flame, Hartz, Smith & Thompson ABSTRACT An automobile speed control system of the vacuum actuated type having a unitized housing embodying actuator, modulator, electronic components and inductive position feedback means Electrical connections into the hermetically sealed expansible actuator, and noise caused by feedback potentiometer wear are eliminated. Valve means within the actuator are operated by magnetic forces generated externally to the actuator, thus eliminating electrical connections. The feedback means comprise a metallic body sealed in the actuator and movable therewith and an inductor external to the housing arranged so that its inductance will vary according to the position of the metallic body.

3,222,996 12/1965 Thieme (it al 3,313,212 4/1967 Baker et a1. 6 Claim, 7 Drawing Figures 3,455,411 7/1969 Carp et al ..123/102 TACHOMETER GENERATOR MEMORY COMPARATOR VACUU M 080. DETECTOR PATENTEDAFR 1 Y 1915 3.727. 517

SHEET 1 OF 2 TACHOMETER GENERATOR MEMORY COMPARATOR RAYMEN F. EMERY L. l BY A Z k-A.

ATTORN EY 62 (ATMOSPHERE ,-7| 7o\ 030. DETECTOR FIG. 5

72 I INVENTORS f RALPH w. CARP 73 LEONCIO T. ANG

: MICHAEL SLAVIN AUTOMATIC SPEED CONTROL BACKGROUND OF THE INVENTION The present invention relates to improvements in automatic speed controls for automobiles.

More particularly, it relates to improvements in the speed control and the modulator-actuator thereof disclosed and claimed in U.S. Pat. Nosv 3,455,4ll and 3,477,346.

The modulator-actuator of U.S. Pat. No. 3,477,346 comprises a rigid housing closed at one end by a spring biased flexible diaphragm and containing two solenoid operated plunger valves, one of which controls flow through a passage communicating with the atmosphere and the other of which controls flow through a passage communicating with the intake manifold of an automobile engine. The valves are operated by circuit means disclosed in U.S. Pat. No. 3,455,41 l in such manner as to control the pressure within the housing at some level below ambient atmospheric thereby causing the diaphragm to be collapsed a controlled amount to displace a linkage controlling the engine throttle position.

A feature of the speed control system described in U.S. Pat. No. 3,455,4l l is the provision of a feedback signal related to throttle position. This signal is derived from a potentiometer energized by a dc. source and having its movable arm linked to the displaceable member of the actuator.

A disadvantage of the use of a potentiometer for feedback is that, in time, wear of the movable contact causes the output signals generated thereby to be noisy or even to fail completely.

It is an object of this invention to provide a speed control system similar to that of U.S. Pat. No. 3,455,41 l but improved thereover by the elimination of the potentiometer as the means for generating the feedback signal.

Another object of the invention is to provide a control system of unitized construction insofar as both the electromechanical elements and the circuit components are all contained within a single compact housing of simplified construction, thereby reducing manufacturing costs, cost of installation on a vehicle and the space occupied thereon.

Briefly, the invention comprises a control mounted in a housing which includes a rigid body section and a flexible section deformable by atmospheric pressure to produce a substantially linear output displacement. The two housing sections are separated by an airtight wall having valve ports therein through which air may be admitted to and exhausted from the flexible section. The feedback means are comprised in a preferred embodiment by a variable frequency oscillator tuned by means of a movable core coil. A cylindrical well is molded in the airtight wall with its open end facing the flexible section of the housing. A ferrite slug is inserted in the well and secured at one end to the flexible section so that movement of the flexible section varies the depth of insertion of the slug in the well. The well cylinder protrudes from the wall into the rigid body section of the housing and supports the coil of the variable frequency oscillator. The frequency and amplitude of the oscillator signal vary according to the depth of insertion of-the slug into the coil, thus the oscillator frequency or amplitude is indicative of the position of the flexible section. The oscillator output is detected to provide a dc. signal which may be utilized in the same manner as the signal provided by prior feedback potentiometers. Iron solenoid cores and supports for valve flappers are molded into the airtight wall during its manufacture providing an assembly in which the electrical elements requiring circuit connections are all external to the flexible, hermetically sealed section, thus eliminating the airtight seals for conductors needed in prior assemblies.

In the drawings:

FIG. 1 is a perspective of the invention with portions thereof broken away to show the interior construction;

FIG. 2 is a section along the line 2-2 of FIG. 1;

FIG. 3 is an elevation, partly in section, of the normally open flapper valve controlling admission of air from the atmosphere to the flexible section of the housmg;

FIG. 4 is an elevation, partly in section, of the normally closed flapper valve controlling exhaust of the air from the flexible section of the housing to the engine intake manifold;

FIG. 5 is a functional block diagram of the invention;

FIG. 6 is a schematic diagram of the variable frequency oscillator providing a position feedback signal; and

FIG. 7 is a section along the line 7-7 of FIG. 4.

Referring to FIGS. 1 and 2, the invention is seen as comprising a housing having a rigid body section 10 and a flexible body section 11 separated by an air-tight wall 12. Body section 11 is formed of a molded rubber accordion-like bellows 13 having a metal stiffening ring 14 and

lips

15 and 16 molded therein. The outer end of bellows 13 is closed by a disk 17 of rigid plastic material inserted in lip 15 and sealed either by the elastic forces of the lip or by a suitable cement. Wall 12 is formed with a circumferential flange 18 which fits tightly within the groove of lip 16 and is sealed thereto either by the elasticity of the lip or by a suitable cement. Wall 12 is molded with a dish-like cavity 19 containing the valve operating flappers, later to be described; an axial cylindrical portion 21 closed at its remote end and receiving in the well thereof a slug 22; and a sectorial flange 23 projecting forwardly within the bellows l3. Flange 23 serves as a guide for a compression spring 24 which tends to expand the bellows 13. Slug 22 is flexibly attached to disk 17 by an unloaded tightly coiled tension spring 25. This permits slug 22 to move linearly within cylinder 21 while disk 17 may be flexed into a plane askew the axis of cylinder 21. The position and attitude of disk 17 with respect to the axis of cylinder 21 is somewhat indefinite during operation since the forces tending to constrain housing 11 into strictly reciprocal motion are relatively small.

Solenoid cores

26, 27 and

posts

28, 29 are molded into wall 12 during its manufacture. The longer portions of

cores

26 and 27 project into housing 10 and support

bobbins

31, 32 containing solenoid windings. The shorter portions of

posts

28 and 29 project into the flexible housing 11 and are notched to support

movable armatures

33, 34 of the flapper valves. The longer portions of

posts

28, 29 extend into housing 10 and serve as spacers for a circular printed circuit board 35 upon which circuit components (not shown) may be mounted and also to complete the magnetic circuits of the solenoids. The assembled solenoid cores, windings and armatures comprise exhaust and inlet valves and 30, more fully described with reference to FIGS. 3 and 4.

A bobbin 36 containing a coil 37 of wire is slipped over the outer surface of cylinder 21. Bobbin 36 also serves as a spacer for a second circular printed circuit board 38 which is held in place by a resilient washer 39 slipped on the end of cylinder 21 and captured by the end wall of housing 10. A stud 41 molded into the end of cylinder 21 and nut 42 holds the housing 10, printed circuit board 38, and bobbin 36 in place.

Slug 22 preferrably is of ferrite material although it can as well be composed of other magnetic or conductive materials. If the slug is magnetic, the inductance of coil 37 increases with increasing depth of slug insertion. If the slug is conductive the coil inductance decreases with increasing depth of slug insertion. The inductance of coil 37 is accordingly a measure of the position of the slug within the coil and the inductance can be gauged by a variety of known means. In the preferred embodiment coil 37 forms the inductive branch of the tank circuit of an oscillator, shown schematically in FIG. 5, but bridge circuits could be used as well. The composition of slug 22 is likewise a matter of choice, depending upon the magnitude and direction of inductance change desired.

Referring to FIGS. 3 and 4 valve 30, of the normally open type, controls the flow of air from the atmosphere through a port 43 in wall 12 into the flexible housing 11. As best seen in FIG. 7, which is a sectional view of FIG. 4 showing corresponding structure of valve 20, armature 33 extends through and pivots upon the bottom of the U-shaped notch 40 in the end of post 28 projecting into body section 11. Again referring to FIG. 3, a compression spring 44 bears against the upper surface of armature 34 and against a bracket 45 which is crimped to the. upstanding legs 46 provided by the notch in post 29. The end 47 of armature 34 is turned down towards wall 12 to provide a stop against which spring 44 normally biases the armature, holding an elastic valve poppet 48 carried by the armature normally clear of port 43. Printed circuit board 35 is held against bobbin 32 by an L-shaped bracket 49 and nut 50 threaded on the end of core 27. An upstanding tongue 51 is pierced and folded back from the leg of bracket 49 to provide opposing surfaces which grip the depending portion of post 29. Bracket 49 and post 29 complete the magnetic circuit through the armature and core of the solenoid. A thin disk 53 of elastic material fastened to the end of core 27 aids in releasing the armature when the solenoid is deenergized.

Referring to FIG. 4, valve 20 is similar in construction to valve 30 except that the elastic valve poppet 54 thereof is positioned within compression spring 44 so as to be normally forced against the valve seat 55 and seal the same, thereby providing a valve of the normally closed type. The manifold vacuum line connects to a channel 56 and valve port 57 molded into wall 12. When the solenoid is energized armature 33 is drawn towards core 26 raising poppet 54 from the valve seat 55 and permitting air to flow from the flexible housing 11 through passage 57 and channel 56 into the vacuum line.

The operation of the system is similar to that described in U.S. Pat. No. 3,455,41 1. Referring to FIG.

5. whenever the automobile speed is below the command speed a substantial amount, a large positive error signal will be produced by comparator 60. This signal is sufficiently great to cause

transistors

61 and 62 both to conduct. Current will then flow from the positive voltage source 63 through the winding of solenoid 20,

transistors

61 and 62 to ground and through the winding of solenoid 30 and transistor 62 to ground. Valve 20 (normally closed) will be open and valve 30 (normally open) will be closed. Air will then be withdrawn from the flexible housing by manifold vacuum causing the engine throttle, which is linked to the flexible housing by a bead chain 64 or similar means, to be opened. As a result the vehicle speed will increase and as the vehicle speed approaches the command speed the error signal output voltage of comparator 60 drops in magnitude. In order for transistor 61 to conduct, the error signal applied thereto must exceed the level necessary to cause transistor 62 to conduct by an amount equal to the forward voltage drop of diode 65. Therefore, as the vehicle speed approaches the command speed and the error signal. decreases in magnitude, transistor 61 will first cease to conduct while transistor 62 remains conductive. This causes valve 20 to be deenergized and the passage from the flexible housing to manifold vacuum to be sealed. The volume of the flexible housing and consequently the position of the engine throttle will remain constant so long as the error signal remains at a level sufficient to maintain transistor 62 conductive but not great enough to cause transistor 61 to conduct. Should the vehicle speed exceed the command speed the error signal output of comparator 60 drops to a still lower level which is insufficient to maintain transistor 62 conductive. Both valves.20 and 30 are then deenergized so that'valve 30 reverts to its normally open condition while valve 20 remains closed, thus allowing air from the atmosphere to enter the flexible housing expanding it and moving the engine throttle towards a closed position. The foregoing brief explanation has not taken into account the fact that the error signal output of comparator 60 is actually a function of vehicle speed, command speed and throttle position, the latter of which quantities is derived from the position of slug 22 within cylinder 21.

Referring to FIG. 6, coil 37 is connected as the inductive branch of an oscillator tank circuit. The oscillator is suitably of the Colpitts type employing a transistor 67 and

tank capacitors

68, 69. The detector 71 comprising a diode rectifier 72 and an RC filter 73 is coupled to the collector of transistor 67 by a differentiating network 74. With slug 22 withdrawn from coil 37 to the limit of travel imposed by the fully expanded condition of bellows 13, the inductance of coil 37 will be at a minimum value and oscillator 70 will operate at its maximum frequency. The impedance of the tank circuit comprised by coil 37 and

capacitors

68, 69 will also be at a minimum value and consequently minimum signal voltage is coupled by network 74 to detector 71, producing a minimum direct voltage output. When bellows 13 is contracted to its full limit of travel, slug 22 will be inserted in coil 37 a maximum amount, thereby causing the inductance of coil 37 to be at its greatest value and the frequency of oscillator 70 to be at a minimum value. Under these conditions the impedance of the oscillator tank circuit will have increased to a maximum value and the voltage coupled into detector 71 will be at a maximum, resulting in a maximum direct voltage output from the detector. By appropriate selection of dimensions for the slug and coil, number of coil turns and the like, the direct voltage output of detector 71 can be caused to vary linearly as the bellows moves from one extreme position to the other. Consequently, the detector voltage output can be used as the full equivalent of a feedback voltage derived from a potentiometer energized by a dc. source.

Although the invention has been described with reference to a particular application as an automobile speed control, other obvious uses exist. For example, the source of command signals may be changed from a speed sensor to a temperature sensor and the invention may then be adapted to use as temperature controller for heating or air conditioning systems.

The invention claimed is:

l. A fluid operated servo of unitary construction comprising,

a fixed wall of rigid material,

a flexible bellows of generally cylindrical form sealed to said wall so as to be axially extensible therefrom,

a pair of ports in said wall, one of said ports providing the sole channel for the admission of fluid to the interior of said bellows and the other of said ports providing the sole channel for exhausting fluid therefrom,

first and second cores of magnetic material sealed in said wall adjacent said ports and projecting from said wall oppositely from said bellows,

first and second supporting posts sealed in said wall, each having a portion projecting from said wall into the interior of said bellows and each having a portion projecting from said wall exteriorly of said bellows generally parallel with the projections of said cores,

electrical solenoids wound on the projections of each of said cores,

first and second magnetic armatures each pivotally mounted on the projecting portion of said first and second posts interiorly of said bellows, said armatures each extending proximate the location of said first and second cores in said wall so as to be pivotally movable by magnetic forces from said cores generated by said solenoids,

first and second valve means each being carried by one of said armatures for sealing said one and said other of said ports,

of said ports is connected to the atmosphere.

. A servo as claimed in claim 1 wherein said means providing an electrical signal related to the position of said bellows comprises,

a body of metallic material contained within said bellows and movable therewith, and w an inductor positioned adjacent said wall exteriorly to said bellows and having an inductance which varies according to the position of said body.

4. A servo as claimed in claim 1 wherein said first armatures and said first valve means carried thereby are located to control flow through said port connected to said source of vacuum and spring means are provided for biasing said first armature and said first valve means to a position normally closing said vacuum port, and

wherein said second armature and said second valve means carried thereby are located to control flow through said port connected to the atmosphere and spring means are provided for biasing said second armature and said second valve means to a position normally opening said atmospheric port.

5. A servo as claimed in claim 3 wherein said wall is formed with a cylindrical portion located along the axis of said bellows and having an open end facing said bellows and being closed at the opposite end,

said body of metallic material moving axially within said cylindrical portion of said wall, and

said inductor comprises an electrical coil wound upon the surface of said cylindrical portion of said wall exteriorly to said bellows.

6. A servo as claimed in claim 5 with additionally an oscillator circuit and a detector circuit and wherein said coil comprises part of a resonant circuit for said oscillator, the output of said oscillator varying in accordance with the position of said body of metallic material, said detector converting said oscillator output to a direct current signal related to the position of said body.

Claims

1. A fluid operated servo of unitary constRuction comprising, a fixed wall of rigid material, a flexible bellows of generally cylindrical form sealed to said wall so as to be axially extensible therefrom, a pair of ports in said wall, one of said ports providing the sole channel for the admission of fluid to the interior of said bellows and the other of said ports providing the sole channel for exhausting fluid therefrom, first and second cores of magnetic material sealed in said wall adjacent said ports and projecting from said wall oppositely from said bellows, first and second supporting posts sealed in said wall, each having a portion projecting from said wall into the interior of said bellows and each having a portion projecting from said wall exteriorly of said bellows generally parallel with the projections of said cores, electrical solenoids wound on the projections of each of said cores, first and second magnetic armatures each pivotally mounted on the projecting portion of said first and second posts interiorly of said bellows, said armatures each extending proximate the location of said first and second cores in said wall so as to be pivotally movable by magnetic forces from said cores generated by said solenoids, first and second valve means each being carried by one of said armatures for sealing said one and said other of said ports, first and second bodies of magnetic material each connecting the projections of said first and said second core with said generally parallel projection of said first and said second post, means connected to one of said ports for generating a differential fluid pressure between the interior and the exterior of said bellows, means for selectively energizing said solenoids, and means providing an electrical signal related to the axial position of said bellows.

2. A servo as claimed in claim 1 wherein one of said ports is connected to a source of vacuum and the other of said ports is connected to the atmosphere.

3. A servo as claimed in claim 1 wherein said means providing an electrical signal related to the position of said bellows comprises, a body of metallic material contained within said bellows and movable therewith, and an inductor positioned adjacent said wall exteriorly to said bellows and having an inductance which varies according to the position of said body.

4. A servo as claimed in claim 1 wherein said first armatures and said first valve means carried thereby are located to control flow through said port connected to said source of vacuum and spring means are provided for biasing said first armature and said first valve means to a position normally closing said vacuum port, and wherein said second armature and said second valve means carried thereby are located to control flow through said port connected to the atmosphere and spring means are provided for biasing said second armature and said second valve means to a position normally opening said atmospheric port.

5. A servo as claimed in claim 3 wherein said wall is formed with a cylindrical portion located along the axis of said bellows and having an open end facing said bellows and being closed at the opposite end, said body of metallic material moving axially within said cylindrical portion of said wall, and said inductor comprises an electrical coil wound upon the surface of said cylindrical portion of said wall exteriorly to said bellows.