Throttle body default actuation

An electronically actuated, air control valve regulates the flow of combustion air to an internal combustion engine. The valve includes an air passage having a throttle valve rotatable therein between a first, minimum air flow position and a second, maximum air flow position. Between the minimum and the maximum air flow positions is a default air flow position for operation of the engine during actuator inoperativeness. A biasing member has a first end operable to impart a force on the valve member in the direction of the default air flow position when the valve member in operable between the minimum air flow position and the default position. Likewise, the biasing member has a second end operable to impart a force on the valve member in the direction of the default air flow position when the valve member is operated in the range between the default air flow position and the maximum air flow position. As a result, a single biasing member operates to position the throttle valve at a default air flow position between the minimum and the maximum air flow positions across the entire range of positions.

TECHNICAL FIELD 
The invention relates to throttle body mechanisms for internal combustion 
engines and, particularly, to an apparatus for positioning the throttle 
valve of an electronically actuated throttle body in a default position 
allowing positive air flow therethrough. 
BACKGROUND 
Electronically controlled throttle valves are contemplated for controlling 
the quantity of combustion air admitted to the intake manifold of internal 
combustion engines. These systems, typically referred to in the automotive 
arts as electronic throttle control systems (ETC), utilize an 
operator-actuated pedal position sensor which functions to transmit driver 
intent to an electronic actuator for positioning the throttle valve. It 
may be desirable to mechanically locate the throttle valve in a 
predetermined "default" position at times of actuator inoperativeness 
thereby assuring continued engine operation. 
A contemplated apparatus for default positioning of the throttle valve 
utilizes a throttle valve having a range of travel extending from a 
negative throttle plate position through a zero or minimum throttle plate 
position at which air flow through the throttle valve is minimized to a 
maximum or wide-open-throttle position in which air flow is maximized. 
During operation of the electronic actuator, the throttle plate is 
operated between the minimum and maximum air flow positions. 
Inoperativeness of the actuator allows a biasing member to move the 
throttle plate to the negative throttle plate position assuring a default 
quantity of air flow to the engine and, therefore, continued engine 
operation. The negative position throttle body, referred to as an 
over-center design, involves costly manufacturing processes imposed by 
throttle bore/valve plate tolerances required to allow the throttle plate 
deflection through the zero or minimum air flow position. 
SUMMARY OF THE PRESENT INVENTION 
The present invention discloses an air control valve or throttle body 
having a valve which is operated by an electronic throttle actuator 
between a minimum air flow position and a maximum air flow position. 
During inoperativeness of the actuator, a default mechanism positions the 
throttle valve in a default position between the minimum and the maximum 
positions. In the default position, positive air flow through the valve 
allows continued engine operation. 
The air control valve includes a housing having an intake air passage or 
throttle bore in which is disposed a throttle valve. The throttle valve is 
rotatable between a minimum and a maximum position to thereby meter the 
quantity of air passing through the throttle bore and to the engine. The 
throttle valve, preferably of the butterfly type, includes a throttle 
plate attached to a rotatable shaft which extends diametrically across the 
throttle bore. 
The throttle shaft to which the throttle plate is attached, is driven by 
the electronic actuator to a desired location between the minimum and the 
maximum air flow positions. As mentioned above, a default position is 
located between the minimum and the maximum valve positions. It is 
desirable that in all cases of actuator inoperativeness the throttle valve 
be positioned in the default position to assure continued engine operation 
at the default air flow. A biasing member is operable on the throttle 
shaft at locations between the minimum air flow position and the default 
position and at locations between the default position and the maximum air 
flow position to return the throttle valve to the default position. 
The biasing member includes a spirally wound torsion spring in a coaxial 
relationship to the throttle valve shaft. The spring ends are preloaded 
such that each end exerts an opposed, rotational force on the throttle 
valve shaft. A spring stop on the housing limits the travel of each end of 
the torsion spring such that the rotational forces exerted by the two ends 
of the spring member on the throttle valve shaft are only applied to the 
shaft in the direction of the default throttle valve position. As such, 
during positioning of the throttle valve by the actuator, at throttle 
valve locations between the minimum air flow position and the default air 
flow position, one end of the spring member exerts a force on the throttle 
valve in the direction of the default position while the second end of the 
spring member is grounded against a housing stop. Should the actuator 
become inoperative in this range of motion, the first end of the spring 
member will return the valve to the default position. Alternatively, at 
throttle valve locations between the default air flow position and the 
maximum air flow position, the second end of the spring member exerts a 
force on the throttle valve in the direction of the default position while 
the first end of the spring member is grounded against a housing stop. 
Should the actuator become inoperative in this range of motion, the second 
end of the spring member will operate to return the throttle valve to the 
default position. 
As a result of the bias exerted by the first and second spring ends against 
the throttle valve shaft, the throttle valve is biased towards a default 
position from all locations within it operating range. The bias of the 
throttle valve towards the default air flow position is achieved with a 
single spring member. 
Other objects and features of the invention will become apparent by 
reference to the following description and to the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, an air control valve assembly, designated generally as 
10, is shown having a throttle body housing 12 with an air flow passage or 
throttle bore 14 extending therethrough. The throttle bore 14 conducts air 
to the intake system of an internal combustion engine (not shown). A 
throttle valve 16, which includes a throttle plate 18 attached to a shaft 
20, is rotatably mounted within the throttle bore 14 of the throttle body 
housing 12. Bearings 22 support the throttle valve shaft 20 in the housing 
12 and define a throttle valve axis 24 about which the valve 16 rotates to 
meter the flow of air through the throttle bore 14. FIG. 3 illustrates the 
full range of motion of the throttle valve 16 in the bore 14. The valve is 
rotatably moveable from a minimum air flow position "A" to a maximum air 
flow position "B". Intermediate of the minimum and maximum throttle valve 
positions is a default position "C". The default position "C" relates to a 
predetermined positive air flow which will allow continued engine 
operation should the actuating mechanism used to position the throttle 
valve become inoperative. 
Operably connected to the throttle shaft 20 is an electronic actuator 26. 
The actuator drives the throttle valve 16, based on operator input, to 
position the throttle valve between the minimum "A" and the maximum "B" 
air flow positions. 
Referring now to FIGS. 1, 2, 4 and 5, the throttle body housing 12 includes 
a throttle return spring housing portion 28 which includes an inner wall 
30 and a bottom 32 through which the end 34 of the throttle valve shaft 20 
extends for attachment to the actuator 26. A biasing member such as 
spirally wound torsion spring 36 is disposed within the spring housing 
portion 28 of the throttle body housing 12. The spring 36 surrounds the 
end 34 of the throttle valve shaft 20 in a coaxial relationship therewith 
and includes first and second ends 38 and 40, respectively. Support for 
the spring coils may be provided by a bushing disposed between the 
throttle shaft 20 and the coils. 
The spring member 36 is rotationally preloaded within the spring housing 28 
by rotating the spring ends 38,40 in opposite directions about the 
throttle valve axis 24 in the direction of the spring bias. The preload of 
spring 36 is maintained by allowing each spring end 38,40 to abut a stop 
42 in the spring housing portion 28. In the embodiment shown in FIGS. 4, 5 
and 6, the spring ends 38,40 abut opposite sides 44,46 of the housing stop 
42 resulting in a spring force Fa being exerted on side 44 of the housing 
stop 42 in the counterclockwise direction, as viewed in the Figures, of 
rotation about axis 24, and a spring force Fb being exerted on side 46 of 
the housing stop 42 in the clockwise direction of rotation about axis 24. 
A spring actuating tang 48 depends from the throttle shaft 20 of the 
throttle valve 16 and is configured for positioning between the spring 
ends 38,40 in their positions against the housing stop 42; the position 
referred to as the default throttle position "C". In the default position, 
the throttle valve plate 18 is positioned within the throttle bore 14 to 
allow a positive, default quantity of air to flow to the intake of the 
engine allowing continued engine operation with no throttle plate movement 
as in the case of actuator inoperativeness. In the default position "C", a 
neutral or zero force condition exists on the throttle valve spring 
actuating tang 48 with the spring ends 38,40 seated against opposing sides 
44,46 of the housing stop 42 and the tang 48 positioned therebetween. 
During actuator operation and positioning of the throttle valve 16, the 
actuator 26 will rotate the throttle valve shaft 20 and attached throttle 
valve plate 18 through a range of motion extending between the minimum air 
flow position "A" and the maximum air flow position "B"; the range of 
motion including the default position "C". In the range of motion between 
the minimum air flow position "A" and the default air flow position "C", 
shown in FIG. 5, the first spring end 38 is moved off of its seated 
position against the housing stop 42. In this range of motion, force Fa is 
exerted on the spring actuating tang 48 and acts to return the tang to the 
default position "C". Actuator inoperativeness in the range of motion 
between the minimum air flow position "A" and the default position "C" 
will result in the throttle valve tang 48, and associated throttle valve 
16, being moved to the default position "C" under the force Fa exerted by 
the spring end in the counterclockwise direction. Once the tang 48 of the 
throttle shaft 20 is returned to the default position "C", it is prevented 
from moving off of the default position "C" by the action of both spring 
ends 38,40 against the housing stop 42 and the forces Fa and Fb exerted 
thereon in opposing directions which are operable to capture the tang 48 
therebetween, as shown in FIG. 2. Similarly, in the range of motion 
between the default air flow position "C" and the maximum air flow 
position "B", shown in FIG. 6, the second spring end 40 is moved off of 
its seated position against the side 46 of the housing stop 42. In this 
range of motion, force Fb is exerted on the valve shaft tang 48 and acts 
to return the tang to the default position "C". Actuator inoperativeness 
in the range of motion between the default air flow position "C" and the 
maximum air flow position "B" will result in the throttle valve 16 being 
moved to the default position "C" under the force Fb exerted by the spring 
end 40 in the clockwise direction. Similarly, once the tang 48 of the 
throttle shaft 20 is returned to the default position "C", it is prevented 
from moving off of the default position "C" by the action of both spring 
ends 38,40 against the housing stop 42 and the forces Fa and Fb exerted 
thereon in opposing directions which are operable to capture the tang 48 
therebetween. 
It is not essential to the operation of the present invention that the 
first and second ends of the spring member be positioned against a common 
housing stop as in the above example. An alternate embodiment of the 
invention, shown in FIGS. 7, 8 and 9, utilizes a throttle body housing 12' 
having first and second housing stops 50,52 located in arcuately separated 
positions about the throttle valve shaft axis. In the preloaded state, the 
ends 38',40' of the spring member 36' separately engage the housing stops 
50,52, respectively. The first spring end 38' engages first housing stop 
50 and exerts a force Fa in the counterclockwise direction, as viewed in 
the Figures, while the second spring end 40' engages second housing stop 
52 and exerts a force Fb in the clockwise direction. In this embodiment of 
the invention the default position of the throttle valve is defined across 
an arc between the stops 50,52 and the spring actuation tang 48' depending 
from the throttle valve shaft will similarly include the arc between its 
actuating faces 54,56. Although tang 48' is illustrated as a one piece 
body in the Figures, it is contemplated that multiple tangs having faces 
54,56 rotating in a fixed relationship to each other are equally suitable 
to the present application. 
During actuator operation and positioning of the throttle valve, the 
actuator will rotate the throttle valve through a range of motion 
extending between the minimum air flow position "A" and the maximum air 
flow position "B"; the range of motion including the default position "C". 
In the range of motion between the minimum air flow position "A" and the 
default air flow position "C", shown in FIG. 8, the first spring end 38' 
is moved off of its seated position against the housing stop 50. In this 
range of motion, force Fa is exerted on the spring actuating tang 48' and 
acts to return the tang to the default position "C". Actuator 
inoperativeness in the range of motion between the minimum air flow 
position "A" and the default position "C" will result in the throttle 
valve tang 48', and associated throttle valve, being moved to the default 
position "C" under the force Fa exerted by the spring end in the 
counterclockwise direction. Once the tang 48' is returned to the default 
position "C", it is prevented from moving off of the default position "C" 
by the action of both spring ends 38',40' against the housing stops 50,52 
and the forces Fa and Fb exerted thereon in opposing directions which are 
operable to capture the tang 48' therebetween. Similarly, in the range of 
motion between the default air flow position "C" and the maximum air flow 
position "B", shown in FIG. 9, the second spring end 40' is moved off of 
its seated position against the housing stop 52. In this range of motion, 
force Fb is exerted on the valve shaft tang 48' and acts to return the 
tang to the default position "C". Actuator inoperativeness in the range of 
motion between the default air flow position "C" and the maximum air flow 
position "B" will result in the throttle valve tang 48' being moved to the 
default position "C" under the force Fb exerted by the spring end 40' in 
the clockwise direction. Similarly, once the tang 48' of the throttle 
shaft is returned to the default position "C", it is prevented from moving 
off of the default position "C" by the action of both spring ends 38',40' 
against the housing stops 50,52 and the forces Fa and Fb exerted thereon 
in opposing directions which are operable to capture the tang 48' 
therebetween. 
The disclosed invention provides an air control valve for an internal 
combustion engine in which the throttle valve is positioned through an 
electronic actuator. A default position providing positive air flow to the 
engine is achieved through the use of a single spring member. The throttle 
default position lies between the minimum and maximum air flow positions 
of the throttle valve. 
The foregoing description of the preferred embodiment of the invention has 
been presented for the purpose of illustration and description. It is not 
intended to be exhaustive nor is it intended to limit the invention to the 
precise form disclosed. It will be apparent to those skilled in the art 
that the disclosed embodiments may be modified in light of the above 
teachings. The embodiments described were chosen to provide an 
illustration of the principles of the invention and its practical 
application to thereby enable one of ordinary skill in the art to utilize 
the invention in various embodiments and with various modifications as are 
suited to the particular use contemplated. Therefore, the foregoing 
description is to be considered exemplary, rather than limiting, and the 
true scope of the invention is that described in the following claims.