The present invention relates to a parallel arrangement of valved aspirators coupled to an engine system. A combined motive flow rate through the aspirators may be controlled to achieve a pumping performance comparable to that of a conventional electrically-driven or engine-driven vacuum pump.
Vehicle engine systems may include various vacuum consumption devices that are actuated using vacuum. These may include, for example, a brake booster. Vacuum used by these devices may be provided by a dedicated vacuum pump, such as an electrically-driven or engine-driven vacuum pump. While such vacuum pumps advantageously produce a pumping curve that is independent of intake manifold pressure, they do so at the expense of fuel and/or energy efficiency. As an alternative to such resource-consuming vacuum pumps, one or more aspirators may be coupled in an engine system to harness engine airflow for generation of vacuum. Aspirators (which may alternatively be referred to as ejectors, venturi pumps, jet pumps, and eductors) are passive devices which provide low-cost vacuum generation when utilized in engine systems. An amount of vacuum generated at an aspirator can be controlled by controlling the motive air flow rate through the aspirator. For example, when incorporated in an engine intake system, aspirators may generate vacuum using energy that would otherwise be lost to throttling, and the generated vacuum may be used in vacuum-powered devices such as brake boosters.
While aspirators may generate vacuum at a lower cost and with improved efficiency as compared to vacuum pumps, their use in engine intake systems has traditionally been constrained by intake manifold pressure. Whereas conventional vacuum pumps produce a pumping curve which is independent of intake manifold pressure, pumping curves for aspirators arranged in engine intake systems may be unable to consistently provide a desired performance over a range of intake manifold pressures. Some approaches for addressing this issue involve arranging a valve in series with an aspirator, or incorporating a valve into the structure of an aspirator. An opening amount of valve is then controlled to control the motive air flow rate through the aspirator, and thereby control an amount of vacuum generated at the aspirator. By controlling the opening amount of the valve, the amount of air flowing through the aspirator and the air flow rate can be varied, thereby adjusting vacuum generation as engine operating conditions such as intake manifold pressure change. However, such valves can add significant component and operating costs to engine systems. As a result, the cost of including the valve may reduce the advantages of aspirator vacuum control.
To address at least some of these issues, the inventors herein have identified a parallel, valved aspirator arrangement which, when incorporated in an engine system, may advantageously produce a pumping curve comparable to that of a conventional driven vacuum pump without the costs and efficiency losses of a conventional vacuum pump. For example, the inventors herein have recognized that the valves of multiple valved aspirators arranged in parallel and bypassing an intake throttle may be controlled based on intake manifold vacuum and/or based on desired engine airflow to minimize throttling losses while generating vacuum for use with vacuum-powered devices. Because multiple, parallel aspirators are used, each aspirator may have a relatively small flow diameter and yet the arrangement can still achieve an overall motive flow rate commensurate with that of a single larger aspirator when needed. The relatively small flow diameters of the aspirators enable the use of smaller, cheaper valves controlling their motive flow. Further, relative flow diameters of the parallel aspirators may be strategically selected such that the valves of the aspirators may be controlled based on intake manifold vacuum level and/or desired engine airflow to produce a desired pumping curve. Furthermore, because the combined motive flow rate through the aspirator arrangement is controllable via the valves, conditions where the motive flow through the aspirators may cause air flow greater than desired may be reduced. Thus, since air flow rate greater than desired can lead to extra fuel being injected, fuel economy may be improved by use of the aspirator arrangement.
In one example, a method for an engine includes increasing a combined motive flow rate through a parallel aspirator arrangement of at least two valved aspirators bypassing an intake throttle as intake manifold pressure increases. This method takes advantage of the engine's ability to handle a greater throttle bypass flow rate as intake manifold pressure increases by controlling the valves of the valved aspirators of the aspirator arrangement such that the combined motive flow rate through the aspirator arrangement increases with increasing intake manifold pressure. When the combined motive flow rate through the aspirator arrangement increases, it follows that the vacuum generated by the aspirator arrangement increases, and therefore a pumping curve which resembles a vacuum pump's pumping curve (e.g., which is independent of intake manifold) may be achieved by the aspirator arrangement. Accordingly, the technical result achieved via this example method is the generation of vacuum by a parallel valved aspirator arrangement in quantities that are substantially independent of intake manifold pressure, while continuing to supply an appropriate engine air flow rate. In embodiments where the aspirator arrangement bypasses the intake throttle, the intake throttle may be adjusted to supply a difference between a desired engine air flow rate and a maximum combined motive flow rate through the aspirator arrangement.
Further, the inventors herein have recognized that the parallel valved aspirator arrangement described herein may advantageously supply a sufficient, controllable engine air flow rate during intake throttle fault conditions. Accordingly, a cheaper intake throttle may be used instead of a more costly intake throttle with a partially open unpowered position which is often used in engine systems to allow for sustained engine operation in the case of malfunction of electronic throttle control.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
Methods and systems are provided for controlling a motive flow rate through a parallel arrangement of valved aspirators coupled to an engine system, such as the engine systems of
Turning to
Engine 12 includes a control system 46. Control system 46 includes a controller 50, which may be any electronic control system of the engine system or of the vehicle in which the engine system is installed. Controller 50 may be configured to make control decisions based at least partly on input from one or more sensors 51 within the engine system, and may control actuators 52 based on the control decisions. For example, controller 50 may store computer-readable instructions in memory, and actuators 52 may be controlled via execution of the instructions.
Engine 12 has an engine intake 23 that includes an air intake throttle 22 fluidly coupled to an engine intake manifold 24 along an intake passage 18. Air may enter intake passage 18 from an air intake system including an air cleaner 33 in communication with the vehicle's environment. A position of throttle 22 may be varied by controller 50 via a signal provided to an electric motor or actuator included with the throttle 22, a configuration that is commonly referred to as electronic throttle control. In this manner, the throttle 22 may be operated to vary the intake air provided to the intake manifold and the plurality of engine cylinders. As discussed above, whereas motorized throttles are often designed to default to a 6° or 7° open position when unpowered, for example so that the engine may receive enough air flow to complete a current trip even in the case of failure of the electronic throttle control (sometimes referred to as “limp home” operation), throttle 22 may have a fully closed default position. A fully closed default position may be used in conjunction with the parallel valved aspirator arrangement described herein because the combined motive flow through the arrangement may be sufficient in the case of electronic throttle control failure (e.g., the combined motive flow rate of the aspirator arrangement may be 7.5 grams per second (g/s) in one non-limiting example). In this way, as discussed above, the costly partially open unpowered position of the intake throttle may be eliminated. As a further advantage over the partially open unpowered position of the intake throttle, the parallel valved aspirator arrangement provides multiple airflow levels for use during the fault mode, depending on the number of aspirators in the arrangement, providing better performance during limp home operation.
A mass air flow (MAF) sensor 58 may be coupled in intake passage 18 for providing a signal regarding mass air flow in the intake passage to controller 50. While MAF sensor 58 is arranged downstream of the charge air cooler and upstream of aspirator arrangement 180 in the embodiment depicted in
In some examples, additional pressure/vacuum sensors may be coupled elsewhere in the engine system to provide signals regarding pressure/vacuum in other areas of the engine system to controller 50.
In some embodiments, engine system 10 is a boosted engine system, where the engine system further includes a boosting device. In the present example, intake passage 18 includes a compressor 90 for boosting an intake air charge received along intake passage 18. A charge air cooler (or intercooler) 26 is coupled downstream of compressor 90 for cooling the boosted air charge before delivery to the intake manifold. In embodiments where the boosting device is a turbocharger, compressor 90 may be coupled to and driven by an exhaust turbine (not shown). Further compressor 90 may be, at least in part, driven by an electric motor or the engine crankshaft.
An optional bypass passage 28 may be coupled across compressor 90 so as to divert at least a portion of intake air compressed by compressor 90 back upstream of the compressor. An amount of air diverted through bypass passage 28 may be controlled by opening compressor bypass valve (CBV) 30 located in bypass passage 28. By controlling CBV 30, and varying an amount of air diverted through the bypass passage 28, a boost pressure provided downstream of the compressor can be regulated. This configuration enables boost control and surge control.
In some embodiments, engine system 10 may include a positive crankcase ventilation (PCV) system (not shown) that is coupled to the engine intake so that gases in the crankcase may be vented in a controlled manner from the crankcase. Therein, during non-boosted conditions (when MAP is less than barometric pressure (BP)), air is drawn into the crankcase via a breather or vent tube 64. Crankcase ventilation tube 64 may be coupled to fresh air intake passage 18 upstream of compressor 90. In some examples, the crankcase ventilation tube 64 may be coupled downstream of air cleaner 33 (as shown). In other examples, the crankcase ventilation tube may be coupled to intake passage 13 upstream of air cleaner 33. As shown in
Engine system 10 further includes a parallel valved aspirator arrangement 180. In the depicted embodiment, for the sake of example, aspirator arrangement 180 includes two aspirators, aspirators 150 and 160; however, it will be appreciated that aspirator arrangement 180 may include more than two aspirators (e.g., three, four, five, six, or more aspirators) arranged in parallel without departing from the scope of this disclosure. One or both of aspirators 150 and 160 may be ejectors, aspirators, eductors, venturis, jet pumps, or similar passive devices. Each aspirator of aspirator arrangement 180 is a three-port device including a motive inlet, a mixed flow outlet, and an entraining inlet arranged at a throat of the aspirator. For example, aspirator 150 includes a motive inlet 153, a mixed flow outlet 157, a throat 161, and an entraining inlet 165. Similarly, aspirator 160 includes a motive inlet 154, a mixed flow outlet 156, a throat 163, and an entraining inlet 167. As described further below, motive flow through each aspirator generates a suction flow at the entraining inlet of the aspirator, thereby generating vacuum, e.g. which may be stored in a vacuum reservoir and provided to various vacuum consumers of the engine system.
An aspirator shut-off valve (ASOV) is arranged in series with each aspirator of aspirator arrangement 180. In the embodiment depicted in
In the embodiments described herein, ASOVs 151 and 152 are solenoid valves which are actuated electrically, and the state of each ASOV may be controlled by controller 50 based on various engine operating conditions. However, as an alternative, the ASOVs may be pneumatic (e.g., vacuum-actuated) valves; in this case, the actuating vacuum for the valves may be sourced from the intake manifold and/or vacuum reservoir and/or other low pressure sinks of the engine system. For example, because it may be advantageous to increase a combine flow through the aspirator arrangement as intake manifold pressure increases as described herein, it may be advantageous to use vacuum-actuated ASOVs which are actuated based on intake manifold vacuum. Actuation thresholds of such vacuum-actuated valves may be different for different aspirators to achieve different desired combined flow levels through the aspirator arrangement. In embodiments where the ASOVs are pneumatically-controlled valves, control of the ASOVs may be performed independent of a powertrain control module (e.g., the ASOVs may be passively controlled based on pressure/vacuum levels within the engine system).
Whether they are actuated electrically or with vacuum, ASOVs 151 and 152 may be either binary valves (e.g. two-way valves) or continuously variable valves. Binary valves may be controlled either fully open or fully closed (shut), such that a fully open position of a binary valve is a position in which the valve exerts no flow restriction, and a fully closed position of a binary valve is a position in which the valve restricts all flow such that no flow may pass through the valve. In contrast, continuously variable valves may be partially opened to varying degrees. Embodiments with continuously variable ASOVs may provide greater flexibility in control of the combined motive flow rate of the aspirator arrangement, with the drawback that continuously variable valves may be much more costly than binary valves. In other examples, ASOVs 151 and 152 may be gate valves, pivoting plate valves, poppet valves, or another suitable type of valve.
As detailed herein with reference to
In the example embodiment depicted in
While the example engine system depicted in
Returning to the aspirators of aspirator arrangement 180, a throat flow area (e.g., a cross-sectional flow area through the throat of the aspirator) of the aspirators may be non-uniform in some examples. For example, as may be seen in the detail view of aspirator arrangement 180 depicted in
Further, in some examples, each parallel flow path may itself branch into further parallel flow paths each containing one or more aspirators with either the same or different diameters/cross-sectional flow areas at their throats, e.g. downstream of the ASOV, which then merge into a single flow path upstream of the passage at which all of the parallel flow paths merge upstream of the low pressure sink (e.g., the intake manifold). Such configurations may provide further flexibility in controlling engine air flow rate and vacuum generation, e.g. during a throttle fault condition where the throttle is in a fully closed position and all airflow is directed through the aspirator arrangement. In such examples, the aspirators may have a common high pressure source such as throttle inlet pressure (TIP) but different low pressure sinks such as the intake manifold and compressor inlet pressure (CIP).
As previously mentioned, each aspirator of aspirator arrangement 180 includes an entraining inlet at the throat of the aspirator. In the example embodiment depicted in
Vacuum reservoir 38 may be coupled to one or more engine vacuum consumption devices 39. In one non-limiting example, a vacuum consumption device 39 may be a brake booster coupled to vehicle wheel brakes wherein vacuum reservoir 38 is a vacuum cavity in front of a diaphragm of the brake booster, as shown in
As shown, vacuum reservoir 38 may be directly or indirectly coupled to intake manifold 24 via a check valve 41 arranged in a bypass passage 43. Check valve 41 may allow air to flow to intake manifold 24 from vacuum reservoir 38 and may limit air flow to vacuum reservoir 38 from intake manifold 24. During conditions where the intake manifold pressure is negative, the intake manifold may be a vacuum source for vacuum reservoir 38. In examples where vacuum consumption device 39 is a brake booster, inclusion of the bypass passage 43 in the system may ensure that the brake booster is evacuated nearly instantaneously whenever intake manifold pressure is lower than brake booster pressure. While the depicted embodiment shows bypass passage 43 coupling common passage 89 with passage 86 in a region of mixed flow outlet 147 of the aspirator arrangement; other direct or indirect couplings of the intake manifold and the vacuum reservoir are also anticipated.
Now referring to
At 302, method 300 includes measuring and/or estimating engine operating conditions. Engine operating conditions may include, for example, MAP/MANVAC, stored vacuum level (e.g., in the vacuum reservoir), desired level of stored vacuum based on vacuum requests from vacuum consumers, engine speed, engine temperature, catalyst temperature, boost level, MAF, ambient conditions (temperature, pressure, humidity.), etc.
After 302, method 300 proceeds to 304. At 304, method 300 includes determining a desired combined motive flow rate through a parallel arrangement of two or more valved aspirators. In one example, the determination may be made at controller 50 based on signals received from one or more of MAP sensor 60, vacuum sensor 40, MAF sensor 58, and/or based on a position of throttle 22 (e.g., which may be indicative of a vehicle operator torque request) and a position of brake pedal 134. Thus, the determination may be made based on one or more of a desired engine air flow rate, stored vacuum level, and current vacuum requests, among other examples.
After 304, method 300 proceeds to 306. At 306, method 300 includes controlling the ASOVs (e.g., the valves of the valved aspirators) to achieve the desired combined motive flow rate (e.g., the desired combined motive flow rate determined at 304). For example, the ASOVs may be controlled in accordance with the methods of
As may be seen, the ideal performance characteristic 420 has a constant slope (specifically, a slope of 1 in the depicted example). Thus, in the depicted example, actual engine air flow rate is equal to desired engine air flow rate at any given point on the characteristic. In contrast, the actual aspirator arrangement performance characteristic 410 includes “steps” corresponding to the opening/closing of the ASOVs corresponding to the two parallel aspirators. At points 402, 404, and 406 which are arranged at corners of the steps, characteristics 420 and 410 intersect; at these points, the performance of the aspirator arrangement is the same as the performance of an ideal aspirator arrangement for the corresponding desired engine air flow rate and actual engine air flow rate. For aspirator arrangements with more than two parallel aspirators, the steps on such a graph will be smaller (e.g., the more aspirators, the smaller the steps). The relative throat flow areas of the aspirators in an aspirator arrangement will also affect the size of the steps (and thus the frequency of intersection between the actual and ideal performance characteristics). In embodiments where the ASOVs are continuously variable valves, further fine-tuning of performance of the aspirator arrangement may be achieved such that the aspirator arrangement performance characteristic conforms still further to the ideal performance characteristic.
As shown in graph 400, actual aspirator arrangement performance characteristic 410 reaches a maximum at point 406 (corresponding to an actual engine air flow rate and desired engine air flow rate which is between 5 and 10 g/s). As will be described with reference to FIG. 4B, this maximum corresponds to a maximum combined flow rate through the aspirator arrangement when both aspirators are fully open. Accordingly, as the aspirator arrangement may not be able to provide an air flow rate surpassing this maximum valve, it may be necessary to allow at least some intake air to travel via another path from the high pressure source (e.g., the intake passage) to the low pressure sink (e.g., the intake manifold). For example, if the aspirator arrangement is positioned as shown in
As shown in the first row of table 450, when the intake manifold vacuum level is greater than 40 kPa (e.g., when a negative pressure of less than 40 kPa is present in the intake manifold), the engine may be unable to afford any throttle bypass flow. Accordingly, during such conditions, it may be desirable to close both ASOVs such that a combined motive flow through the aspirator arrangement is 0. Closing the ASOVs may be an active process in embodiments where the ASOVs are solenoid valves (e.g., the ASOVs may be controlled by a controller such as controller 50 of
The second row of table 450 corresponds to an intake manifold vacuum level of between 35 kPa and 40 kPa (e.g., a pressure in the intake manifold which is less than −35 kPa but greater than or equal to −40 kPa). When intake manifold vacuum is in this range, it may be desirable to have a first level of combined motive flow rate through the aspirator arrangement. The first level of combined motive flow rate may be achieved by opening the ASOV corresponding to the first, smaller aspirator and closing the ASOV corresponding to the second, larger aspirator. The first level of combined motive flow rate may correspond to point 402 of
The third row of table 450 corresponds to an intake manifold vacuum level of between 30 kPa and 35 kPa (e.g., a pressure in the intake manifold which is less than −30 kPa but greater than or equal to −35 kPa). When intake manifold vacuum is in this range, it may be desirable to have a second level of combined motive flow rate through the aspirator arrangement. The second level of combined motive flow rate may be achieved by opening the ASOV corresponding to the second, larger aspirator and closing the ASOV corresponding to the first, smaller aspirator. The second level of combined motive flow rate may correspond to point 404 of
The fourth row of table 450 corresponds to an intake manifold vacuum level of less than or equal to 30 kPa and greater than 0 kPa (e.g., a pressure in the intake manifold which is greater than −30 kPa and less than 0 kPa). When intake manifold vacuum is in this range, it may be desirable to have a third level of combined motive flow rate through the aspirator arrangement. The third level of combined motive flow rate may be achieved by opening both the ASOV corresponding to the second, larger aspirator and the ASOV corresponding to the first, smaller aspirator. The third level of combined motive flow rate may correspond to point 406 of
Because of the 1:2 ratio of the cross-sectional flow areas at the throats of the aspirators of the example aspirator arrangement referred to in
Now referring to
At 502, method 500 includes measuring and/or estimating engine operating conditions, for example in the manner described above for step 302 of method 300.
After 502, method 500 proceeds to 504. At 504, method 500 includes determining a desired engine air flow rate. For example, desired engine air flow rate may be determined based on engine operating conditions, e.g. MAP/MANVAC, a torque request from a vehicle operator, brake pedal position, etc.
After 504, method 500 continues to 506. At 506, method 500 includes determining whether throttle fault conditions are present. In one non-limiting example, control system 46 may set a flag when diagnostic procedures indicate failure of the electronic throttle control system, and the determination of whether throttle fault conditions are present may include checking whether this flag is set. Alternatively, the determination may be made based on readings from the MAP sensor, MAF sensor, and/or various other sensors.
If the answer at 506 is NO, this indicates that throttle fault conditions are not present (e.g., electronic throttle control is functioning correctly), and method 500 proceeds to 508. At 508, method 500 includes determining whether engine operating conditions permit throttle bypass. For example, during certain engine operating conditions, engine air flow requirements may be such that a fully open throttle and no throttle bypass is necessary. Alternatively, during other engine operating conditions, it may be desirable to divert intake air flow through an aspirator arrangement to thereby generate vacuum for consumption by vacuum consumers of the engine system while avoiding throttling losses.
If the answer at 508 is YES, indicating that engine operating conditions do permit throttle bypass, method 500 proceeds to 510 to determine whether the desired engine air flow rate (e.g., as determined at 504) is greater than a maximum combined motive flow rate through the aspirator arrangement. For example, as described above with reference to
If the answer at 510 is NO, the desired engine air flow rate is not greater than the maximum combined motive flow rate through the aspirator arrangement, and thus the throttle may be closed at 516. After 516, method 500 proceeds to 518 to control the ASOVs based on throat flow areas of the aspirators, desired engine air flow rate, and engine operating conditions. Accordingly, when throttle fault conditions are not present, engine operating conditions permit throttle bypass, and the desired engine air flow rate is less than the maximum combined motive flow rate through the aspirator arrangement, all intake air flow may be diverted around the intake throttle and through the aspirator arrangement to advantageously avoid throttling losses while generating vacuum for use by various vacuum consumers of the engine system. In some examples, control of the ASOVs may be performed in the manner described above with reference to
Returning to 510, if the answer is YES indicating that the desired engine air flow rate is greater than the maximum combined motive flow rate through the aspirator arrangement, method 500 proceeds to 512. At 512, method 500 includes controlling the ASOVs based on throat flow areas of the aspirators, desired engine air flow rate, and engine operating conditions, and further at least partially opening the throttle. In one example, step 512 may be performed in accordance with method 600 of
Returning to 508, if the answer is NO indicating that engine operating conditions do not permit throttle bypass (e.g., all intake air must pass through the throttle), method 500 proceeds to 514. Engine operating conditions may not permit throttle bypass during conditions where a wide open throttle position is necessary and where any lag associated with the flow restrictions of aspirators is unacceptable. As another example, if the control system diagnoses a fault in one or more of the ASOVs, this may constitute an engine operating condition wherein throttle bypass is not permitted. At 514, method 500 includes closing the ASOVs and controlling the throttle based on the desired engine air flow rate and engine operating conditions. In some examples, this may include increasing opening of the throttle as a pressure exerted on an accelerator pedal by a vehicle operator increases. After 514, method 500 ends.
Returning to 506, if the answer at 506 is YES indicating that throttle fault conditions are present, method 500 proceeds to 518 to control the ASOVs in the manner described above. Engine systems including the aspirator arrangements described herein may utilize intake throttles which do not have a costly partially-open unpowered position; instead, they may utilize intake throttles with fully closed unpowered positions, because the aspirator arrangement may provide sufficient engine air flow at controllable levels during the limp home operation described above. Accordingly, during throttle fault conditions where the throttle is in its default, unpowered closed position, the ASOVs alone may be controlled to achieve the desired engine air flow rate.
Now referring to
At 602, method 600 includes determining if the intake manifold pressure (MAP) is less than a first threshold. In one non-limiting example, the first threshold may be −40 kPa (e.g., equivalent to a MANVAC of 40 kPA). If MAP is less than the first threshold, the answer at 602 is YES, and method 600 proceeds to 612 where both ASOVs may be adjusted to the closed position. As described above, closing both ASOVs may be performed actively by controller 50, or may be a passive process occurring based on vacuum levels in the engine system (e.g., based on MANVAC). It will be appreciated that if the ASOVs are already closed (e.g., from a previous iteration of method 500 or 600), step 612 may include taking no action such that both ASOVs remain closed. By ensuring that both ASOVs are in a closed position, throttle bypassing may be prevented such that engine air flow is limited to air flow through the throttle (e.g., combined motive flow rate through the aspirator arrangement is zero or an insubstantial leakage flow rate). After 612, method 600 proceeds to step 610 which will be described below.
In addition to the conditions for closing the ASOVs for all aspirators described for step 612, it will be appreciated that in the case of a boosted engine, where MANVAC may have a negative value during certain conditions, the controller may optionally choose to close the ASOVs for all aspirators to prevent reverse flow from MAP to CIP (e.g., in systems where the aspirator arrangement bypasses from MAP to CIP). However, in systems where the aspirator arrangement bypasses from TIP to MAP, there may not be potential for reverse flow.
Returning to step 602, If MAP is not less than the first threshold, the answer is NO, and method 600 proceeds to 604. At 604, method 600 includes determining if MAP is greater than or equal to the first threshold and less than a second threshold. In one non-limiting example, the second threshold may be −35 kPa (e.g., equivalent to a MANVAC of 35 kPa). If MAP is greater than or equal to the first threshold and less than the second threshold, the answer at 604 is YES, and method 600 proceeds to 614. At 614, method 600 includes opening the ASOV for the smaller aspirator and closing the ASOV for the larger aspirator. For example, as detailed above with respect to the second row of table 450 of
Returning to 604, if the answer is NO, method 600 proceeds to 606 to determine if MAP is greater than or equal to the second threshold and less than a third threshold. In one non-limiting example, the third threshold may be −30 kPa (e.g., equivalent to a MANVAC of 30 kPa). If MAP is greater than or equal to the second threshold and less than the third threshold, the answer at 606 is YES, and method 600 continues to 616. At 616, method 600 includes opening the ASOV for the larger aspirator and closing the ASOV for the smaller aspirator. For example, as detailed above with respect to the third row of table 450 of
However, if the answer at 616 is NO, MAP may be greater than or equal to the third threshold (e.g., −30 kPa). Accordingly, in this case, method 600 proceeds to 608 to open both ASOVs. For example, if MAP is greater than or equal to the third threshold, engine operating conditions may permit an increased throttle bypass flow rate, and therefore it may be desirable to open both ASOVs (or, all ASOVs in configurations with more than two parallel aspirators) in order to maximize the combined motive flow rate through the aspirator arrangement, thereby maximizing vacuum generated via the aspirator arrangement and minimizing throttling losses.
After 608 (as well as after each of steps 612, 614, and 616), method 600 proceeds to 610. At 610, method 600 includes adjusting throttle position based on the difference between the desired engine air flow rate and the combined motive flow rate through the aspirators. For example, as described above with reference to graph 400 of
Note that the example control and estimation routines included herein can be used with various system configurations. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various actions, operations, or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, functions, or operations may be repeatedly performed depending on the particular strategy being used. Further, the described operations, functions, and/or acts may graphically represent code to be programmed into computer readable storage medium in the control system
Further still, it should be understood that the systems and methods described herein are exemplary in nature, and that these specific embodiments or examples are not to be considered in a limiting sense, because numerous variations are contemplated. Accordingly, the present disclosure includes all novel and non-obvious combinations of the various systems and methods disclosed herein, as well as any and all equivalents thereof.
The present application is a continuation of U.S. patent application Ser. No. 13/962,526, entitled “SYSTEMS AND METHODS FOR MULTIPLE ASPIRATORS FOR A CONSTANT PUMP RATE,” filed on Aug. 8, 2013, now U.S. Pat. No. 9,404,453, the entire contents of which are hereby incorporated by reference for all purposes.
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Child | 15226843 | US |