Electronic throttle control

Details Electronic throttle control Electronic throttle control

2000-05-19

2001-11-20

Argenbright, Tony M. (Department: 3747)

Internal-combustion engines

Engine speed regulator

Open loop condition responsive

C123S399000

Reexamination Certificate

active

06318337

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to electronically controlled throttles for vehicle engines. In particular, the present invention relates to the controlling of throttles that are spring biased towards a fast-idle default position.
BACKGROUND OF THE INVENTION
A throttle controls the flow of air, or air and fuel, inducted into an internal combustion engine, and thereby controls the power produced by the engine. Engine power defines the speed of the engine or vehicle to which it is attached, under a given load condition, and thus, reliable control of the throttle setting is important.
In prior art mechanical systems, a direct mechanical linkage controlled the throttle, typically in the form of a cable running from the accelerator pedal, operable by the user of the vehicle, to the throttle valve. Although mechanical linkages are simple and intuitive, they are not readily adapted to electronic control of an engine such as may be desired in sophisticated emissions reduction systems or for features such as automatic vehicle speed control. For these purposes, the mechanical linkage may be replaced with electrical wiring carrying throttle signals from a position sensor associated with the accelerator pedal to a throttle controller operating a throttle actuator (typically an electric motor) for actuating the throttle valve.
While electronic control without mechanical linkages allows for the introduction of a variety of desirable control features, electronic control also makes the operation of the throttle dependent upon the throttle signals to the throttle controller, which controls the throttle actuator. These throttle signals may pick up errors due to noise or otherwise. Those errors can have undesirable effects on the control of the throttle, as discussed below.
As shown in
FIG. 1
(Prior Art), a typical throttle includes a conduit, through which air (or an air-fuel mixture) flows, and a rotatable throttle plate that in part determines the flow rate based on its position within the conduit. In between a closed position, in which the throttle plate prevents nearly all flow through the conduit, and a wide-open position, in which the throttle plate allows a maximum flow rate, there is typically a default position for the throttle plate. The default position is a position of the throttle plate in which a relatively small flow rate is allowed (i.e., where the throttle plate is closer to closed than open).
Under normal operating conditions, the position of the throttle plate is positioned by the throttle actuator (i.e., electric motor). The throttle actuator is typically coupled to the throttle plate by a pair of gears in between which exists lash. (In other cases, the throttle actuator and throttle plate can be coupled by other linking elements that also have lash, such as a belt.) However, the throttle plate is also coupled to a spring mechanism which biases the throttle plate towards the default position. If for some reason the throttle actuator is unable to control the position of the throttle plate (i.e., the throttle actuator produces no output torque), the spring mechanism moves the throttle plate to the default position. Because there is a small amount of flow through the conduit in the default position, the vehicle remains (at least partly) operational when this occurs.
Although the spring mechanism is necessary for allowing partial operation of the vehicle when the throttle actuator is malfunctioning, the spring mechanism complicates the electronic control of the throttle. Proper control of the throttle under normal operating conditions (i.e., when the throttle actuator is properly operating) requires that the throttle actuator compensate for (i.e., counteract) the torque of the spring mechanism. Typically, this compensation is effected by the introduction, into the throttle signals, of a feedforward component.
Generation of the proper feedforward component when the throttle plate is near the default position is difficult, however, for two reasons. As shown in
FIG. 2
(Prior Art), the torque provided by the spring mechanism changes in a discontinuous manner when the throttle plate crosses over the default position. Additionally, because the spring mechanism biases the throttle plate in opposite directions when the throttle plate is on opposite sides of the default position, the gears coupling the throttle plate and the throttle actuator experience a relative shift due to the gear lash as the throttle plate moves through the default position.
Because of the interaction of the spring mechanism, the gear lash and the feedforward component, exact control of the positioning of the throttle plate near the default position is difficult, and undesirable fluctuation of the throttle plate can occur near the default position. This particularly becomes a problem if noise (i.e., duty cycle variation) occurs within the throttle command signal when the throttle plate is at or very close to the default position, such that the throttle signals are effectively commanding the throttle plate to shift back and forth across the default position. Under these circumstances, the throttle plate can experience rapid, undesirable fluctuation that can result in annoying rattling of the throttle plate.
SUMMARY OF THE INVENTION
The present inventor has recognized that the rapid fluctuation and rattling of the throttle plate is caused by the operation of the feedforward component of the throttle control signal while the throttle plate is positioned near the default position, at which there are discontinuities due to operation of the spring mechanism and the gear lash. Thus, the rapid fluctuation and rattling of the throttle plate can be reduced by modifying the throttle control signal.
The present invention therefore relates to a throttle control apparatus in a vehicle having a throttle valve with a default position intermediate a fully-closed position and a fully-open position, and a spring mechanism coupled to the throttle valve that creates torque to move the throttle valve toward the default position in the absence of other torque. The throttle control apparatus includes an actuator for generating torque to open and close the throttle valve in response to a control signal, wherein the actuator is attached to the throttle valve by a mechanical coupling having lash. The throttle control apparatus further includes a processor in communication with the actuator. The processor generates the control signal based upon a command signal. The processor executes a stored program including a portion to compare a new value of the command signal with a prior value of the command signal, and to generate the control signal as a function of the deviation between the new and prior values of the command signal.
The present invention additionally relates to a throttle control method in a vehicle having a throttle valve with a default position intermediate a fully-closed position and a fully-open position, and a spring mechanism coupled to the throttle valve that creates torque to move the throttle valve toward the default position in the absence of other torque. The throttle control method includes receiving a command signal at a processor, comparing a new value of the command signal with a prior value of the command signal at the processor, and generating a control signal at the processor, wherein the control signal is a function of the deviation between the new and prior values of the command signal. The throttle control method further includes providing the control signal to an actuator that is attached to the throttle valve, with lash existing between the actuator and the throttle valve, and generating torque at the actuator to open and close the throttle valve in response to the control signal.
The present invention further relates to a vehicle comprising a throttle valve with a default position intermediate a fully-closed position and a fully-open position. The vehicle includes a restoring means coupled to the throttle valve for creating torque to move the throttle valve toward the default position

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