Method and system for requesting the ON / OFF state of the engine in a hybrid electric vehicle

Abstract

A method for controlling a hybrid electric vehicle comprising a drive unit, an energy storage device, and a controller with a state machine having multiple states, wherein the method comprises a sequence of the following steps: (a) determining the value of a parameter of the storage device; (b) when the machine is in an OFF state requiring the drive unit to be switched off, and the parameter is less than an ON level, causing the machine to transition from the OFF state to an OPPORTUNISTIC state requiring the motor to remain switched on if it is already switched on; (c) when the machine is in an ON state requiring the drive unit to be switched on, and the parameter is greater than the ON level, causing the machine to transition from the ON state to the OPPORTUNISTIC state;(d) if the machine is in the OPPORTUNIST state and the parameter is less than a MIN level, where the MIN level is less than the ON level, the machine is caused to transition from the OPPORTUNIST state to the ON state; and (e) if the machine is in the OPPORTUNIST state and the parameter is greater than an OFF level, where the OFF level is greater than the ON level, the machine is caused to transition from the OPPORTUNIST state to the OFF state.

Description

[0001] The invention relates to hybrid electric vehicles and in particular to a strategy for requesting an ON or OFF state of the motor. due to the condition of the vehicle battery.

[0002] It is well known that the consumption of fossil fuels and the emission of pollutants by automobiles and other vehicles with The number of vehicles powered by combustion engines must be reduced. Vehicles powered by electric motors have attempted to address this. to meet needs. However, electric vehicles have limited range and limited power, while at the same time a It takes a considerable amount of time to recharge their batteries. An alternative solution is the combination of an internal combustion engine. and an electric drive motor in a vehicle. Such vehicles are usually referred to as hybrid electric vehicles.

[0003] The hybrid electric vehicle has been described in many different configurations. In some hybrid electric vehicle systems The driver must choose between operating the electric motor and operating the combustion engine. In other configurations, the vehicle is driven by... The electric motor drives one set of wheels, and the combustion engine drives another set of wheels. Other, more useful ones were also developed. Configurations developed. A series hybrid electric vehicle is a vehicle with a motor (usually an internal combustion engine) that provides power. The generator drives the vehicle. The generator, in turn, provides electricity for a battery and a motor connected to the vehicle's drive wheels. Ready. There is no mechanical connection between the motor and the drive wheels. A parallel hybrid electric vehicle is a vehicle with a motor (usually an internal combustion engine), a battery, and an electric motor that together provide torque to power the to drive the vehicle's wheels. A parallel / series hybrid electric vehicle has characteristics of both a parallel hybrid electric vehicle and a Series hybrid electric vehicle. The parallel / series hybrid electric vehicle is a powertrain configuration with torque distribution (or... (of the power output). Here, the torque generated by the engine is partly directed to the drive wheels and partly to a power generator. The generator powers a battery and a motor, which also generate torque. In this configuration, the generated torque can be transferred. Torque can come from one source or from both sources simultaneously. The vehicle's braking system can also supply torque to... To drive the generator in order to charge the battery (regenerative braking).

[0004] A desirable result of combining the internal combustion engine with an electric motor is that the fuel consumption and the pollutant emissions of the combustion engine are reduced without a noticeable loss of performance or range of the vehicle. One of the advantages of parallel hybrid electric vehicle configurations is that the motor can be used during times when the driver requires little power. or can be switched off if it has no energy requirement at all (e.g., when waiting at a traffic light), which reduces fuel consumption by No fuel is wasted during idling. The electric motor can then primarily be used to propel the vehicle under these conditions. It can be used with low energy consumption. In some configurations, the motor can be separated from the electric motor and the drivetrain. This is done when the engine is not running by opening a disconnect clutch. As energy demand increases, the engine can be restarted and restarted. They must be connected to provide the required torque.

[0005] The two energy sources in a parallel / serial hybrid electric vehicle operate seamlessly with a common transmission system together to meet the driver's energy needs without exceeding the powertrain's performance limits, including the limits of the to exceed the additional battery system. A vehicle system controller takes over the coordination task for this powertrain with Energy distribution. Under normal operating conditions, the vehicle system controller interprets the driver's energy requirements as a function a required acceleration or deceleration. It then determines how much torque each energy source sends to the transmission and when. must be transferred to meet the driver's energy needs and to achieve the specified vehicle performance (i.e., fuel consumption). to achieve the operating point of the relationship between (engine, exhaust emissions, driving behavior, etc.). The vehicle system controller then determines the operating point of the relationship between Engine torque and speed.

[0006] In a hybrid electric vehicle with the ability to start / stop the engine, the battery can draw the maximum discharge power from This can be limited for various reasons. For example, if the battery discharge limit gets too low, it may be impossible to start the engine. Insufficient battery power is available. Furthermore, when the vehicle is in reverse, the generator operates with a higher engine speed. Under these circumstances, more battery power is required to start the engine.

[0007] According to the present invention, a method and a system for controlling the starting / stopping of an engine in a hybrid- Electric vehicle provided that monitors the battery and, based on the current state of the motor and a parameter of the battery requires a specific engine state. In one embodiment of the invention, the parameter is the discharge power limit (DPL) of the battery. and is displayed in real time as a function of the battery's state of charge (SOC), battery resistance, battery temperature, battery voltage, the The battery's open-circuit voltage (OCV) and lifespan are calculated. The battery's discharge power limit is the amount of energy that can be used from the battery. So, if the battery's discharge power limit is 10 kW, the vehicle can use 10 kW. At In another embodiment, the battery's state of charge (SOC) parameter is monitored instead of the battery's discharge power limit. Assuming that the battery's discharge power limit will decrease as the battery's state of charge (SOC) decreases. In both cases. In some embodiments, the battery parameter is compared with a set of threshold levels, including a MIN level, an ON level, and an The system includes OFF levels, and as a result of the comparison, input signals are transmitted to a state machine. Preferably, Different sets of threshold levels are provided, depending on whether the hybrid electric vehicle's transmission is in a driving position or in neutral. in a reverse driving position to account for the higher battery power required to start the engine in reverse gear.

[0008] If the battery's discharge power limit falls below a certain level, it may be necessary to start the engine to recharge the battery. The battery needs to be charged, as otherwise it may not be possible to start the engine at all. However, in many circumstances it can It would be desirable to charge the battery, but not as critically as in the example above. Under these circumstances, it is desirable to... There are other reasons to wait before starting the engine, for example, if the driver's demand is greater than the battery can supply. With the engine running, it may be desirable to prevent the engine from switching off so that the battery can be brought back to a high charge level. or can be brought to a high discharge power limit. This "wait and see" strategy, or this opportunistic operating mode. is included in the present invention and results in a reduction of engine work, thereby reducing fuel consumption, while At the same time, it is ensured that the battery always has enough energy to bring the engine up to its desired speed when the The engine does not generate positive torque (for example, in stop-and-go traffic).

[0009] Further problems and features of the present invention will become apparent in view of the following detailed description of a preferred The embodiment can be seen in conjunction with the attached drawings and the accompanying claims.

[0010] Fig. 1 is a schematic representation of the system configuration of a parallel / serial drive train with the features of the invention;

[0011] Fig. 2 is a state diagram using the discharge power level of the battery compared to a set of Threshold levels for bringing about changes in the state of an implementation of a state machine according to the invention;

[0012] Fig. 3 shows the relative positions of the threshold levels as they are used in the present invention for the driving position and the The reverse gear position of the transmission can be used; and

[0013] Fig. 4 is a state diagram using the state of charge of the battery (SOC) compared to a set of threshold levels. to bring about changes in the state of an implementation of a state machine according to the invention.

[0014] With reference to the drawings and initially with reference to Fig. 1, a hybrid electric vehicle is now generally shown at 10 and comprises a powertrain that can have one of the well-known configurations for hybrid electric vehicles. One example is the configuration for a Parallel / serial hybrid electric vehicle as depicted and described in US patent application No. 10 / 248,886, filed on February 27, 2003 filed and transferred to the legal successor of the present invention and is included therein. The drive train comprises a gearbox 12 connected to an internal combustion engine 14 and a high-voltage battery 16, which serve as energy supply sources can have an effect. It is understood that source 14 is represented as an internal combustion engine, but other sources such as, for example, a Fuel cell systems are used, as is known in engineering. Likewise, source 16 is depicted as a battery, but other types are also possible. Sources such as an ultracapacitor are used, as is known in engineering. A torque output shaft 18 of the gearbox. 12 is connected to the vehicle's drive wheels 20 via a differential and axle mechanism 22. Naturally, the present inventor This also applies to four-wheel drive systems where all wheels are driven.

[0015] A system controller of the vehicle, designated in total by 24, as disclosed in the above-mentioned application, interprets The driver's energy requirements are determined, and it establishes how much torque each energy source must transmit to the transmission and when. to meet the driver's energy needs and achieve a predetermined vehicle performance. According to the present invention The controller 24 also includes a battery controller 26, which responds to battery sensor input signals and outputs signals such as for the For example, the battery's state of charge (SOC) and discharge power limit (DPL) are transferred to a state machine in which a The motor ON / OFF request algorithm specified in point 28 is implemented and is described in more detail below. A motor ON / OFF Decision unit 30 receives requests from a state machine as well as from various other sources and issues a motor ON / OFF command based on a priority scheme that evaluates the various requests.

[0016] Figure 2 now shows a flowchart of the operation of the motor ON / OFF request algorithm as a function of the The discharge power limit (DPL) of the battery is shown. The state machine has three states: ON, OFF, and OPPORTUNISTIC, as shown. These are indicated by reference numbers 32, 34, and 36, respectively. In the ON state 32, the machine sends a request to the decision unit. 30, that the motor should be switched on. In the OFF state 34, the machine sends a request to the decision unit, that the engine should be switched off, or alternatively, it can be requested that it is acceptable to switch off the engine. In the In opportunistic state 36, the machine sends a request to the decision unit 30 that the motor remain switched on. This should occur when the engine is already switched on. If the engine is switched off and the machine is in the OPPOR-TUNISTIC state 36 If the state is in the "on" position, a DON'T CARE request is sent to decision unit 30. The transition between the different states The machine's performance depends on the battery's discharge power limit (DPL) value compared to three threshold levels and the current state. Machine status. The three threshold levels and their relative positions are shown in Fig. 3. The three threshold levels are designated MIN, ON, and OFF. The levels MIN and OFF are located below and above the ON level, respectively.

[0017] The set of threshold levels, shown in Fig. 3 with solid lines, represents calibratable values ​​of the discharge power limit. (DPL) when the vehicle transmission is in the driving position, while the set of threshold levels shown with dashed lines These values ​​are displayed when the vehicle transmission is in reverse. The respective levels of the threshold values. The values ​​for the reverse gear position of the transmission are greater than the corresponding values ​​for the driving gear position in order to compensate for the... The reverse driving position requires higher values ​​for the discharge power limit (DPL) or the state of charge (SOC). The three threshold levels are calibratable, and their values ​​depend on the energy storage device used and the configuration of the Vehicle. For example, a 10kW battery might require setpoints of 2, 4, 6 for the MIN, ON, and OFF levels, while a 50kW battery might require... For example, target values ​​of 30, 35, and 40 might be needed. For the battery's state of charge (SOC), these numbers would express percentages. For the The discharge power limit (DPL) of the battery would be represented by these numbers, which would express the power output.

[0018] Returning to Fig. 2 and assuming the machine is in the OFF state 34, then the machine remains in the OFF state. 34 , if the discharge power limit (DPL) is greater than the ON threshold level, as determined by the NO branch of decision block 38 As indicated, in the OFF state, the state machine sends a request to decision unit 30 to switch off the motor. It should. If, on the other hand, the machine is in the OFF state and the discharge power limit (DPL) is lower than the ON threshold level, then The machine transitions from the OFF state to the OPPOR-TUNISTIC state 36, as through the YES branch of decision block 38. hinted at.

[0019] When the state machine is in the ON state 32 and the discharge power limit (DPL) is less than the ON- If the threshold level is reached, the machine remains in the ON state 32, as indicated by the NO branch of decision block 40. If, on the other hand, the discharge power limit (DPL) is greater than the ON threshold level, then the machine switches from ON state 32 to the OPPORTUNISTIC state 36, as indicated by the YES branch of decision block 40.

[0020] If the discharge power limit (DPL) falls below the MIN level while the machine is in the OPPORTUNIST state When the machine is in state 36, it transitions from OPPORTUNISTIC state 36 to ON state 32, and a request is made to the Decision unit 30 sent a signal that the engine should be switched on, as indicated by the YES branch of the decision. blocks 42 indicated. If, instead, the discharge power limit (DPL) is greater than the MIN level, as indicated by the NO branch of the Decision block 42 is indicated, and if the discharge power limit (DPL) is greater than the OFF level, then the machine goes into OFF mode. The state is as indicated by the YES branch of decision block 44, and a request is made to the decision unit. 30 sent that the motor should be shut down. If the discharge power limit (DPL) is greater than the MIN threshold level, but If the level is smaller than the OFF threshold, as indicated by the NO branch of decision block 44, then the machine remains in the OPPORTUNISTIC state 36 .

[0021] In Fig. 4, the operation of the state machine in response to changes in the state of charge (SOC) of the battery is shown and follows the same data flow as in Fig. 2. The blocks corresponding to the blocks of Fig. 2 in the flowchart of Fig. 4 are marked with blocked numbers. This means the machine remains in the ON state and requires the motor to be switched on as long as the state of charge (SOC) is low. than the ON level. The machine transitions from the ON state to the OPPORTUNIST state when the state of charge (SOC) is greater than the ON level. Likewise, the machine remains in the OFF state and requires the motor to be switched off as long as the state of charge (SOC) is higher. than the ON level. The machine transitions from the OFF state to the OPPORTUNISTIC state when the state of charge (SOC) falls below the ON level. The level drops. The machine will remain in opportunistic mode as long as the state of charge (SOC) is greater than the minimum level, but less than the minimum level. than the OFF level, and will transition from the OPPORTUNIST state to the ON state when the state of charge (SOC) is greater than the OFF level.

[0022] It will be obvious to the person skilled in the art that modifications are made to the embodiment of the disclosed invention. can, without deviating from the scope of the invention. All such modifications and their equivalents shall be defined by the following claims. be covered.

Claims

Method for controlling a hybrid electric vehicle with a drive unit, an energy storage device and a controller with a state machine having multiple states, wherein the method comprises a sequence of the following steps: (a) the value of a parameter of the storage device is determined; (b) if the machine is in an OFF state which requires that the drive unit be switched off, and the parameter is less than An ON level causes the machine to transition from the OFF state to an OPPORTUNISTIC state, which requires that the engine remains switched on if it is already switched on; (c) if the machine is in an ON state which requires the drive unit to be switched on, and the parameter is greater than the At the ON level, the machine is caused to transition from the ON state to the OPPORTUNIST state; (d) when the machine is in the OPPORTUNIST state and the parameter is less than a MIN level, where the MIN level If the level is lower than the ON level, the machine is caused to transition from the OPPORTUNIST state to the ON state; and (e) if the machine is in the opportunistic state and the parameter is greater than an off level, wherein the If the OFF level is greater than the ON level, the machine is caused to switch from the OPPORTUNIST state to the OFF state. to proceed. Method according to claim 1, wherein the storage device is a battery. Method according to claim 2, wherein the drive unit a combustion engine. Method according to claim 3, wherein the parameter is the state of charge (SOC) of the battery. Method according to claim 3, wherein the parameter is the real-time calculated discharge power limit (DPL) of the battery. Method according to claim 3, wherein the Levels depend on the position of a vehicle transmission. Method for controlling a hybrid electric vehicle with a drive unit, a Energy storage device, a gearbox and a controller with a state machine that has multiple states, including an ON- A state that requires the drive unit to be switched on, an OFF state that requires the drive unit to be switched off, and an OPPORTUNISTIC condition requiring that the engine remain switched on if it is already switched on, the procedure comprising a sequence of the following steps: (a) the value of a parameter of the storage device is determined; (b) if the machine is in the ON state and the parameter is greater than an ON parameter gel, the machine is caused to switch from the ON state to the OPPORTUNIST state; (c) if the machine is in the OFF state and the parameter is less than an ON level, the machine will be caused to switch from the to transition from the OFF state to the OPPORTUNIST state; (d) when the machine is in the OPPORTUNIST state and the parameter is less than a MIN level, where the MIN level If the level is lower than the ON level, the machine is caused to transition from the OPPORTUNIST state to the ON state; and (e) if the machine is in the opportunistic state and the parameter is greater than an off level, wherein the If the OFF level is greater than the ON level, the machine is caused to switch from the OPPORTUNIST state to the OFF state. to transition. Controller for a hybrid electric vehicle with a drive unit and an energy storage device, wherein the controller: includes: a state machine with multiple states including an ON state that requires the drive unit to be switched on, a An OFF state, which requires that the drive unit be switched off, and an OPPORTUNISTIC state, which requires that the motor It will remain switched on if it is already switched on; Means for determining the value of a parameter of the storage device; Means of requesting a transition of the machine from the OFF state to the OPPORTUNIST state when the parameter falls below a certain threshold. The input level drops; Means of requesting a transition of the machine from the ON state to the OPPORTUNIST state when the parameter exceeds the The input level increases; Means of requesting a transition of the machine from the OPPORTUNIST state to the ON state when the parameter falls below a certain threshold. The MIN level drops, which is lower than the ON level; Means of requesting a transition of the machine from the OPPORTUNIST state to the OFF state when the parameter exceeds a OFF level rises, which is greater than the ON level. Controller according to claim 8, wherein the vehicle has a transmission and the MIN level, which The ON level and the OFF level are a set of values ​​when the transmission is in a driving position, and a different or higher set of values ​​when the transmission is in a driving position. Values ​​when the transmission is in reverse. Method for controlling the starting and stopping of the drive unit of a Hybrid electric vehicle with an energy storage device and a controller that has a decision unit to control the drive unit to order the start or stop based on an evaluation of the requirements of the decision unit, whereby the procedure is a sequence of The following steps are included: (a) the value of a parameter of the storage device is determined; (b) if the motor is switched off and the parameter level is greater than an ON level, a command to the decision unit is issued. Engine shutdown discontinued; (c) if the motor is switched off and the parameter level falls below the ON level, a command is issued to the decision unit that the engine should remain switched on if the engine is currently switched on; (d) if the level of the parameter is less than a MIN level, a command is issued by the decision unit to turn on the motor. The motor should remain switched on until the parameter level reaches the ON level, and then a command is issued to keep the motor switched on. when the motor is currently switched on. Method according to claim 9, wherein the ON level has a value between the MIN level and the OFF level. Method according to claim 10, wherein the vehicle has a transmission and the controller contains a first and a second set stored from MIN, ON and OFF levels, with the first set being used when the transmission is in a driving position, and the The second set is used when the transmission is in a reverse driving position. Method according to claim 12, wherein the values ​​of the second The values ​​of the first set are higher than the respective values ​​of the first set. Method for controlling a vehicle with a primary energy source and a Energy storage device, wherein the method comprises the following steps: Determining one or more operating parameters of the energy storage device; Transition to a new operating state of a state machine due to at least the operating parameter of the energy storage device and of the current state of the state machine; Requirement that the operation of the primary energy source be changed to ON or OFF, or remain ON, depending on the state of the State machine. Method for controlling a vehicle with a primary energy source and an energy storage device, wherein the The following procedures The steps include: Determining an operating parameter of the energy storage device; Transferring the value of the parameter as an input signal to a state machine with an ON state, wherein the state machine has a issues a command to turn on a primary energy source, with an OFF state, where the state machine issues a command to turn off a primary energy source, and with an OPPORTUNISTIC state, wherein the state machine issues a command that The primary power source should remain switched on if it is already switched on, and a DON'T CARE command is issued if the primary power source is switched off. The power source is switched off; Transition of the state machine from the opportunistic state to the ON state or the OFF state based on the value of the Operating parameters. Two drawing sheets follow.

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