Patent Application
20110017178
This disclosure relates generally to canister purge control valve control systems and more particularly to canister purge control valve control systems operated in response to pulse width modulation control signals.
As is known in the art, many multi-cylinder internal combustion engines include an evaporative fuel recovery system in which fuel vapors vented from the fuel tank and captured in a carbon canister are drawn into the engine where they are combusted along with fuel delivered by fuel injectors. Such systems can include a purge control valve, which controls the flow rate of canister purge fuel vapors entering the engine. Some purge control valves are controlled by pulse-width modulation signals. Pulse-width modulated valves can be driven by an electrical input signal which is high for a fraction of the signal period and low for the remainder of the signal period. The high portion of the signal is called the on-pulse. The valve opens to allow purge fuel vapors to enter the engine during the on-pulse and closes for the remainder of the signal period. The frequency and duration of the on-pulse determines the average flow rate through the valve. In some canister purge control valve control systems operated in response to pulse width modulation control signals, the canister purge valve (CPV) creates an undesirable clomping sound that is heard in vehicle passenger compartment. One pulse width modulation signal control system is presented in U.S. Patent Publication No. US2004/105209A1.
In one embodiment, purge control valve control system is provided having: a voltage source; a purge control valve having an inductor coupled to the voltage source; a transistor having: a control electrode fed by a train of pulses; a first electrode coupled to the voltage source; and a second electrode coupled to the voltage source through the inductor; and a diode connected in parallel with the transistor. Pulse width modulation pulses are fed to the control electrode and switch the transistor between a conducting and a non-conducting condition. When in the conducting condition current from the voltage source passes through the inductor with a potential being produced across the diode to bias the diode to a non-conducting condition and when the transistor switches into the non-conducting condition, energy previously stored in the inductor produces a voltage pulse to bias the diode to a conducting condition and such stored energy is dissipated as such energy passes through the biased diode to the voltage source.
In one embodiment, the diode is connected to the first and second electrodes of the transistor.
In one embodiment, the diode is a Zener diode.
In one embodiment, a purge control valve control system is provided for an internal combustion engine system. The system includes: a voltage source having a positive potential and a negative potential; a purge control valve having a solenoid, such solenoid comprising and electrically inductive element, such inductive element having a first terminal coupled to the positive potential of the voltage source; and a Zener diode having an anode and a cathode and wherein the anode is connected to the negative potential of the voltage source. A control unit comprises: a transistor having: a control electrode fed by a train of pulses; a first electrode coupled to the negative potential of the voltage source; and a second electrode coupled to a second terminal of the inductive element and to the cathode of the diode. A train of pulses fed to the control electrode is a pulse width modulated signal and switches the transistor between a conducting condition, wherein current passes between the first electrode and the second electrode, and a non-conducting condition, wherein current is prevented from passing between the first electrode and the second electrode. When the transistor is in the conducting condition current from the voltage source passes through the inductive element and through the first and second electrodes with a potential being produced across the diode to bias the diode to a non-conducting condition and wherein when the transistor switches into the non-conducting condition, energy stored in the inductor when current passes through the inductor during the conducting condition of the transistor, produces a voltage pulse to breakdown the diode to a conducting condition and such stored energy is dissipated in the inductor as such energy passes as current through the Zener diode to the negative potential of the voltage source voltage source.
In one embodiment, a purge control valve control system is provided having: a voltage source; a purge control valve having an inductor coupled to the voltage source; a first transistor having a first electrode coupled to the voltage source and a second electrode coupled to the voltage source through the inductor; and a second transistor connected in parallel with the inductor. Pulse width modulated pulses are fed to the control electrode of the first transistor and to a control electrode of the second transistor to switch the transistors between a conducting and a non-conducting condition. When the first transistor is in the conducting condition the second transistor is in the non-conducting condition and current from the voltage source passes through the inductor and the first transistor and when the first transistor is in the non-conducting condition the second transistor is in a conducting condition and energy previously stored in the inductor passes through the conducting second transistor.
In one embodiment, the pulse width modulated pulses fed to the control electrodes of the first transistor and second transistors are out of phase one with the other.
In one embodiment, the pulse width modulated pulses are fed to the control electrodes of the first transistor and second transistors with the train of pulses fed to the second transistor having an on-time less than the off-time of the train of pulses fed to the first transistor so that the second transistor enters the non-conducting state before the first transistor enters the conducting state. In this way, the duty cycle of the second transistor could be smaller or larger than the first, depending whether the first duty cycle is more or less than 50%. For example, if the first transistor has 40% duty cycle (on-time), the second transistor could have an on-time (say 55%) less than the 60% off-time of the first transistor. This would stop all current flow and allow the valve to close. Note that in this case, the duty cycle of the second transistor is larger than that of the first transistor.
The details of one or more embodiments of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.
Multicylinder reciprocating internal combustion engine 10, shown in
Continuing with
Controller 40, which may comprise a conventional engine control microprocessor known to those skilled in the art, or a stand-alone processor, as desired, is charged with the task of operating engine 10 in both a stratified charge mode and a homogeneous charge mode. When no canister purging and either stratified or homogeneous operation is required, controller 40 operates canister vent valve 26 closed, canister purge valve 22 closed, and ambient air control valve 20 open. Compressor 16 compresses air passing through ambient air control valve 20 to a predetermined pressure regulated by relief valve 18. Compressed air from compressor 16 is delivered to air rail 14 for use by injectors 12 to enhance fuel properties, such as atomization, in the engine cylinders (not shown). At the same time, liquid fuel 30 from tank 28 is delivery to fuel rail 15 to be injected by injectors 12.
When purging of canister 24 is required, controller 40 adjusts canister vent valve 26, canister purge valve 22, and ambient air control valve 20 in response to a predetermined desired vapor purge rate. During purging operation, canister purge valve 22 is open, but canister vent valve 26 and air control valve 20 may be both open, both closed, or one open and one closed. For example, if the desired vapor purge rate is less than the vapor flow rate exiting canister purge valve 22, then ambient air control valve 20 is opened to dilute the vapor flow.
Here the purge control valve 22 is fed a pulse width modulated signal by the controller 40. More specifically, the vapor flow rate percent is controlled by the ratio of the duty cycles of the pulse width modulated signals.
The purge control valve control system 100 for the purge control valve 22 is shown in
Referring now to
More particularly, the inductor L has a first terminal Ti connected the positive potential (+) of the voltage source 200. A first transistor 209 has a first electrode, here a source electrode (S) connected to the negative potential (−) of the voltage source 200 and a second electrode, here a drain electrode (D) connected to the second terminal T2 of the inductor L and has a gate (G) electrode connected by a pulse width modulated signal 211 from the controller 40. Here a second N-channel MOS FET 215 has a first electrode (D) connected to both the first terminal Ti of the inductor L and the positive potential (+) of the voltage source 200 and a second electrode (S) connected to the second terminal T2 of the inductor L. Thus, the second transistor 215 is connected in parallel with the inductor L. The second transistor 215 has a control electrode, here gate (G) fed a pulse width modulated signal 211′ produced by the controller 40. It is noted that the train of pulses 211 is 180 degrees out of phase (i.e., a one pulse time delay) with the pulse train 211′. One implementation is to have a one pulse width time delay between the two pulse trains 211, 211′ as by passing pulse train 211 through a flip flop to generate the pulse train 211′. Thus, there is a one pulse time delay between the two pulse trains 211, 211′. Alternatively, the train of pulses 211′ may have a slightly shorter on time than the off-time of pulse train 211 to allow the valve to close fully before the next cycle.
In any event, pulses are fed to the control electrode (G) of the first transistor 209 and to a control electrode (G) of the second transistor 215 to switch the transistors 209, 215 between a conducting and a non-conducting condition. When the first transistor 209 is in the conducting condition the second transistor 215 is in the non-conducting condition and current from the voltage source 200 passes through the inductor L and the first transistor 209 and when the first transistor 209 is in the non-conducting condition the second transistor 215 is in a conducting condition and energy previously stored in the inductor L passes through the conducting second transistor 215.
A number of embodiments of the disclosure have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. For example other transistor types may be used for the transistors 209 and 215. Accordingly, other embodiments are within the scope of the following claims.
