Method for controlling a hybrid vehicle powertrain and hybrid vehicle controlled according to such a method

Abstract

Method for controlling a powertrain of a hybrid vehicle with an internal combustion engine, at least one motor / generator and a rechargeable battery, wherein the method comprises: Recording at least one set of route input data that includes a start point and an end point of a preferred route of the vehicle; Determining an optimal fuel-saving route to reach the endpoint based on at least one set of route input data; Selecting a powertrain control strategy to achieve the most fuel-efficient route, wherein the powertrain control strategy includes determining when to operate the engine and at least one motor / generator and when to charge the battery; and Execution of the powertrain control strategy; the optimal fuel-saving route is additionally determined based on the selected powertrain control strategy.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to a hybrid vehicle having a control method for improving fuel economy of the vehicle, and more particularly to a method and apparatus for determining an optimal energy management strategy for maximizing fuel economy of a hybrid vehicle operating in a charge-consuming mode. BACKGROUND OF THE INVENTION

[0002] Conventional hybrid vehicles are powered by an engine and one or more electric motor / generators, which in turn are fed by a rechargeable battery. In a charge-depleting mode, the battery is allowed to slowly discharge or drop to a minimum or threshold charge level over the course of the trip, where it can be recharged, for example, using available energy from the engine power, the motor / generator, and / or by connecting the battery to an available power source such as an electrical outlet when the vehicle reaches its destination.

[0003] During hybrid vehicle operation, a control method typically selects a preferred power source or combination of power sources (i.e., the engine and / or one or more motors / generators) to power the hybrid vehicle in an optimally fuel-efficient manner, as is known, for example, from US 2005 / 0 228 553 A1. The control method also monitors the battery charge level and schedules battery charging to ensure that the motors / generators remain operational for powering the hybrid vehicle, as is known, for example, from US 6 487 477 B1. The battery is maintained in a charge-consuming mode or a charge-sustaining mode.Generally, a battery enters a charge-depleting mode when a control method selects the motor / generator as the preferred power source, such as when the vehicle accelerates from a stop and draws energy from the battery, thereby depleting the battery charge. In charge-sustaining mode, the battery is maintained at a specific charge level, thereby preserving or maintaining the battery charge level.

[0004] The effectiveness of a given control method or algorithm in managing the selection and / or combination of available hybrid power sources is influenced by various external factors. For example, the distance of a vehicle's journey or route, the route topography, and the frequency of braking along the route each influence the vehicle speed profile over that route. The ability to "look ahead" to a planned route when determining an optimal powertrain strategy can therefore help maximize the hybrid vehicle's fuel economy over the route. SUMMARY OF THE INVENTION

[0005] According to the invention, a method having the features of claim 1 for controlling a drive train of a hybrid vehicle, a method having the features of claim 8 and a hybrid vehicle having the features of claim 13 are specified.

[0006] In one aspect of the invention, the method comprises receiving real-time traffic data as an additional set of route input data.

[0007] In a further aspect of the invention, the method comprises receiving topographical information describing the topography of the optimal fuel-efficient route as a further set of route input data.

[0008] In a further aspect of the invention, the method comprises continuously evaluating the real-time traffic data and updating the route and the powertrain control strategy based on the continuously evaluated real-time traffic data.

[0009] In another aspect of the invention, the method includes establishing a threshold battery charge level, determining the current charge level, and determining the powertrain control strategy based on the difference between the threshold charge level and the current charge level.

[0010] In another aspect of the invention, the powertrain control strategy includes driving the vehicle by the engine and includes, for the engine, either homogeneous charge compression ignition, port fuel injection, active fuel management, a direct injection strategy, or a variable compression ratio strategy.

[0011] In another aspect of the invention, the powertrain control strategy includes using ethanol and / or gasoline and / or dimethyl ether and / or diesel fuel to operate the internal combustion engine.

[0012] In another aspect of the invention, a method is provided for optimizing fuel consumption of a vehicle having a hybrid powertrain including an engine, a battery, and at least one motor / generator. The method includes determining the presence or absence of a preferred route for the vehicle, including the starting point and the ending point of the preferred route, and selecting a powertrain control strategy in either charge-consuming mode or charge-sustaining mode. The charge-consuming strategy is selected when a preferred route has been determined, while the charge-sustaining strategy is selected when no preferred route has been determined.

[0013] In another aspect of the invention, a hybrid vehicle is provided, including an engine, a motor / generator, a battery operatively connected to and chargeable thereby by the engine and the motor / generator, a navigation system operable to determine an optimal fuel-efficient route based in part on a user-selected starting point and an end point, and a powertrain control module (PCM) operatively connected to the navigation system. The PCM senses the battery charge level and, based on the charge level, determines an optimal powertrain strategy along the optimal fuel-efficient route when user-selected points have been selected, and maintains the sensed charge level in the absence of user-selected starting and end points.

[0014] In another aspect of the invention, a plurality of vehicle sensors receive real-time traffic data from an external source, wherein the PCM receives the real-time traffic data and determines the optimal route based on the received real-time traffic data and the points selected by the user.

[0015] The above features and advantages, as well as other features and advantages of the present invention, will become readily apparent from the following detailed description of the best modes for carrying out the invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram of a hybrid vehicle according to the present invention; and Fig. Figure 2 is a flowchart illustrating the preferred method of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] In the drawings where the same reference numerals refer to the same components, Fig. 1 shows a schematic representation of a hybrid vehicle 10 according to the present invention. The hybrid vehicle 10 is shown for illustrative purposes, but alternative hybrid vehicle configurations are contemplated within the scope of the invention. The hybrid vehicle 10 includes an engine 12 operatively connected to a transmission 14. The transmission 14 includes at least one electric motor / generator 16 powered by a rechargeable battery 18 when acting as a motor and operative to charge the battery 18 when acting as a generator. Transmission power or torque is transferred to the wheels 19 to thereby propel or drive the hybrid vehicle 10. Operably connected to the engine 12 and the transmission 14 is a power train control module (PCM) 22.

[0017] When the hybrid vehicle 10 is driven or operated, the PCM 22 designs an optimal powertrain control strategy for driving the hybrid vehicle 10 in an optimal fuel-efficient manner. The powertrain control strategy may include, for example, determining when to operate the engine 12 and the electric motor / generator 16 and / or when to charge the battery. As described in more detail below, the PCM 22 includes a control method or algorithm 38 (see Fig. 2), which, as described below, is configured or programmed to "look ahead" and generate the powertrain control strategy and an optimal route for a particular trip. For the purposes of the present invention, "look ahead" refers to the ability to anticipate future driving conditions or events.

[0018] To enable "look-ahead," the PCM 22 is operatively connected to a vehicle navigation system 24. To initiate the method of the present invention, the operator manually enters route input data for a preferred route in the form of the starting point and the ending point into the navigation system 24. The navigation system 24 may obtain the current location of the vehicle 10 using a global positioning system, or GPS (not shown), or alternatively, the current location may be manually entered by the operator. This provides the PCM 22 with data identifying the starting point and ending point of a preferred route or journey.

[0019] The PCM 22 includes a storage device 26. An electronic map, such as those available from TeleAtlas, located in Southfield, Michigan, is stored in the storage device 26. Using the electronic map and the starting and ending points of a particular route or trip, the PCM 22 can select an optimal route. The determination of which route is optimal is preferably based primarily on vehicle fuel economy, but other considerations may include, for example, the estimated time for the trip, the distance required for the trip, and / or traffic regulations. The electronic map preferably includes elevation or topography information, which may also be used in selecting an optimal route.As an example, a shorter route with extreme elevation changes such as hilly or mountainous topography may require more fuel consumption than a longer route with a generally constant or flat elevation.

[0020] The PCM 22 receives “look-ahead” data in the form of real-time traffic information from one or more of a variety of external sources 28. The real-time traffic sources 28 may, for example, be an OnStar ®System, a satellite radio, a vehicle-to-vehicle communication device, and / or a cellular connection. This real-time traffic data may be used by the PCM 22 in determining the optimal route. As an example, a shorter route with excessive traffic congestion may require more frequent vehicle acceleration and deceleration compared to a longer route with light traffic, thereby increasing fuel consumption, so the longer route would be the optimal one.

[0021] The PCM 22 receives vehicle data from one or more of a plurality of vehicle sensors 30. The vehicle sensors are configured or programmed to receive and / or monitor various vehicle characteristics such as fuel level, remaining battery charge or current charge level, temperature, and / or speed or RPM, or other similar vehicle characteristics. This received or monitored sensor data is used to determine the powertrain control strategy. As one example, when the battery charge level is low, i.e., less than or equal to a default or threshold battery charge level, it may be necessary to operate the engine 12 to propel the vehicle 10 and charge the battery 18 to maintain adequate vehicle performance.

[0022] Having described the apparatus of the present invention above, the preferred method will now be explained. Fig. Figure 2 shows a method or algorithm 38 of the present invention. More specifically, Fig. 2 is a block diagram showing steps performed by the PCM 22 (in Fig. 1 shown).

[0023] Beginning with step 40, the algorithm 38 determines whether a preferred route is selected or entered, for example, by determining whether user-selected start and end points describing a preferred route have been entered into the navigation system 24 (see Fig. 1). As stated above, starting point data may be obtained from a GPS (not shown) or manually entered into the navigation system 24 by the vehicle operator (see Fig. 1). The data identifying the end point of the journey is preferably entered manually by the vehicle operator. If the start point and end point data are not entered at step 40, the algorithm 38 defaults to step 52 and implements a more conventional "charge-maintaining strategy" or mode, as defined in more detail below. Otherwise, the algorithm 38 proceeds to step 42.

[0024] In step 42, the route data from the PCM 22 (see Fig. 1) and recorded in memory 26. The algorithm 38 then proceeds to step 44.

[0025] In step 44, the algorithm 38 selects an optimal route and designs a powertrain control strategy. There may be a relationship between these two objectives, such that the selection of an optimal route may influence the powertrain control strategy and vice versa. The optimal route and the powertrain control strategy are therefore preferably jointly determined based on the received or monitored "look-ahead" data described above, for example, from the real-time traffic sources 28, the vehicle data from the vehicle sensors 30 and / or the data stored in the memory device 26 (see Fig. 1) stored or recorded map information or topographical information. The selected or determined optimal route is preferably communicated to the vehicle operator via the navigation system 24 (see Fig. 1) transmitted.

[0026] According to the preferred embodiment, the powertrain control strategy of step 44 operates the hybrid vehicle 10 (see Fig. 1) In a "charge-depleting mode." For the purposes of the present invention, a "charge-depleting mode" is a mode in which the vehicle 10 is powered primarily by the electric motor / generator 16, such that the battery 18 is depleted or nearly depleted by the time the vehicle 10 reaches its destination. In other words, during the charge-depleting mode, the engine 12 is operated to the extent necessary to ensure that the battery 18 is not depleted before the destination is reached. A conventional hybrid vehicle operates in a "charge-sustaining mode," wherein when the battery charge level falls below a predetermined level (e.g., 25%), the engine is automatically operated to recharge the battery.Therefore, by operating in a charge-consuming mode, the hybrid vehicle 10 can conserve some or all of the fuel that would otherwise be used in a conventional hybrid vehicle to maintain the 25% battery charge level. Note that the vehicle 10 is preferably operated in the charge-consuming mode only when the battery 18 can be recharged after the destination is reached by connecting it to a power source (not shown).

[0027] According to an alternative embodiment, the powertrain strategy of step 44 operates the engine 12 (see Fig. 1) using homogeneous charge compression ignition or HCCI. As is known to those skilled in the art, HCCI is an efficient operating mode in which an internal combustion engine generates pressure to ignite the combustion gases (i.e., ignite without a spark). Other operating modes of the engine 12 designed to improve efficiency and fuel economy are contemplated. Alternative operating modes of the engine 12 may include, for example, a current base combustion technology such as port fuel injection, as well as other modern combustion strategies such as variable valve actuation (VVA), active fuel management (also known as displacement on demand or cylinder deactivation), direct injection, or variable compression ratio.

[0028] According to another alternative embodiment, the powertrain strategy of step 44 operates the engine 12 using different fuel types to improve the efficiency and fuel consumption of a particular application. Such fuels may include, for example, gasoline or diesel fuel, or may include alternative fuels such as ethanol or dimethyl ether. Once an optimal route has been selected and a powertrain strategy has been determined in step 44, the algorithm 38 proceeds to step 46.

[0029] In step 46, the algorithm 38 executes the powertrain strategy designed in step 44. More specifically, the PCM 22 (see Fig. 1) the engine 12 and the transmission 14, which includes the electric motor / generator 16 and the battery 18, such that the vehicle 10 is driven in the manner prescribed by the powertrain strategy. The algorithm then proceeds to step 48.

[0030] In step 48, the algorithm 38 continuously evaluates route input data, which includes data from the real-time traffic sources 28 (see Fig. 1) to "look ahead" and include vehicle data from the vehicle sensors 30. This step is performed to account for new information that was not available initially when the optimal route was selected and the powertrain strategy was designed. As an example, if the vehicle is traveling along a pre-selected optimal route and the PCM 22 receives real-time traffic information indicating that a traffic jam is developing on the currently selected route as a result of a traffic accident, it may be necessary to select an alternative route. The algorithm then proceeds to step 50.

[0031] In step 50, algorithm 38 determines whether the input data from step 48 necessitates a change in the route or control strategy. If, in step 50, the input data from step 48 does not necessitate a change in the route or control strategy, algorithm 38 continues in a loop with step 48 and continuously evaluates the input data. If, in step 50, the evaluated input data from 48 necessitates a change in the route or control strategy, algorithm 38 returns to step 44.

[0032] In step 52 (see step 40), as described above, the algorithm 38 defaults to a "charge maintenance mode." In step 52, the PCM 22 senses or measures the current or present charge level of the battery 18 and compares this current charge level to a threshold or minimum battery charge. The algorithm 38 then proceeds to step 54, where the PCM 22 executes the default charge maintenance mode, thereby maintaining the charge level of the battery 18 at or above the threshold battery charge level.

[0033] While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.

Claims

[1] A method for controlling a drive train of a hybrid vehicle having an internal combustion engine, at least one motor / generator and a rechargeable battery, the method comprising: Recording at least one set of route input data comprising a start point and an end point of a preferred route of the vehicle; Determining an optimal fuel-efficient route to reach the endpoint based on the at least one set of route input data; Selecting a powertrain control strategy to achieve the optimal fuel-efficient route, the powertrain control strategy comprising determining when to operate the engine and the at least one motor / generator and when to charge the battery; and Executing the powertrain control strategy; The optimal fuel-saving route is additionally determined based on the selected powertrain control strategy. [2] The method of claim 1, further comprising receiving real-time traffic data, wherein the at least one set of route input data comprises the received real-time traffic data. [3] The method of claim 1, further comprising receiving topographical information describing the topography of the route, wherein the at least one set of route input data comprises the received topographical information. [4] The method of claim 2, further comprising continuously evaluating the real-time traffic data and updating the route and the powertrain control strategy based at least in part on the continuously evaluated real-time traffic data. [5] The method of claim 1, wherein determining an optimal fuel-efficient route comprises establishing a threshold charge level for the battery, determining the current charge level of the battery, and determining the powertrain control strategy based at least in part on the difference between the current battery charge level and the threshold battery charge level. [6] The method of claim 1, wherein designing the powertrain control strategy comprises driving the vehicle with the engine and further comprises applying one of homogeneous charge compression ignition, port fuel injection, active fuel management, a direct injection strategy, and a variable compression ratio strategy. [7] The method of claim 1, wherein determining a powertrain control strategy comprises using at least one of ethanol, gasoline, dimethyl ether, and diesel fuel to operate the internal combustion engine. [8] A method for optimising fuel consumption of a vehicle having a hybrid powertrain comprising an engine, a battery and at least one motor / generator, the method comprising: Determining the presence or absence of a user-selected endpoint as a destination for a preferred route; and Selecting either a charge-consuming mode in which the vehicle is powered primarily by the motor / generator such that the battery is depleted when the vehicle reaches its destination, or a charge-sustaining mode, wherein the charge-consuming mode is selected when presence has been determined and the charge-sustaining strategy is selected when absence has been determined. [9] The method of claim 8, further comprising, when the charge-consuming strategy is selected, detecting the current charge level of the battery, determining an optimal fuel-efficient route based on the detected current charge level, and determining a powertrain control strategy for optimizing fuel consumption of the vehicle over the route. [10] The method of claim 9, further comprising receiving real-time traffic data, wherein determining an optimal fuel-efficient route comprises continuously evaluating the received real-time traffic data and updating the powertrain control strategy in response to the evaluated real-time traffic data. [11] The method of claim 9, further comprising receiving topographical information describing the topography of the route and updating the powertrain control strategy in response to the topographical information. [12] The method of claim 8, further comprising, when the charge-maintaining strategy is selected, detecting a charge level of the battery and continuously charging the battery to thereby maintain the detected charge level. [13] Hybrid vehicle, comprising: a machine; a motor / generator; a battery operatively connected to the machine and the motor / generator and rechargeable by the machine and / or the motor / generator; a navigation system adapted to receive a starting point and an end point selected by the user; and a powertrain control module (PCM) operatively connected to the navigation system, the PCM operable to sense a battery charge level and, based in part on the sensed charge level, to determine a powertrain strategy along an optimal fuel-efficient route such that the battery is depleted upon reaching the endpoint if the route start and end points have been selected, and to maintain the sensed battery charge level in the absence of the route start and end points. [14] The hybrid vehicle of claim 13, comprising a plurality of vehicle sensors operable to receive real-time traffic data from an external source relative to the vehicle, wherein the PCM is configured to receive the real-time traffic data and determine the optimal fuel-efficient route based in part on the received real-time traffic data and the start and end points. [15] The hybrid vehicle of claim 13, wherein the navigation system includes topographical data for the route and the PCM determines the route based in part on the topographical data. [16] The hybrid vehicle of claim 13, wherein the powertrain strategy comprises driving the vehicle with the engine, and the engine comprises one of homogeneous charge compression ignition, port fuel injection, active fuel management, a direct injection strategy, and a variable compression ratio strategy. [17] The hybrid vehicle of claim 13, wherein the powertrain strategy comprises using ethanol and / or gasoline and / or dimethyl ether and / or diesel fuel to operate the internal combustion engine.

Images