Method for controlling NVH performance after range extender is started at low temperature

Abstract

The invention discloses a method for controlling NVH (Noise Vibration and Harshness) performance after a range extender is started at a low temperature, which comprises the following steps that: a vehicle control unit sends a heating request to a thermal management system of an electric vehicle when a starting request exists at the low temperature; the electric vehicle thermal management system starts a heating unit for heating in advance, a vehicle control unit delays for a certain time and requests a generator to drag an engine and ignite to enter power generation work after judging that the working power of the thermal management system reaches a certain value, and the power generation power and the rotating speed of a range extender are rapidly increased. After the new starting strategy is adopted, the operation process is obviously changed; the PTC is activated and works to the preset specific power level, the system starts the range extender only after the PTC operates stably, the improved strategy enables the range extender to rapidly increase the generated power and the rotating speed of the range extender, the problem that the NVH performance is poor in the low-rotating-speed and low-power generating state is effectively solved, and the service life of the system is prolonged. Therefore, the stability and the comfort of the whole operation are obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of extended-range electric vehicles, and in particular to a method for controlling NVH performance after a range extender is started at low temperatures. Background Art

[0002] In the conventional extended-range electric vehicle starting strategy, we can see that when there is a start request, the vehicle control unit (VCU) will issue a work instruction to the generator and engine in the range extender. Subsequently, the generator starts to drag the engine to a specific speed. During this process, the VCU will issue an enable signal to allow the engine to perform fuel injection operations. Once the engine injects fuel and ignites successfully, it completes the starting process and immediately enters the power generation state to provide the required electricity for the vehicle. However, in extremely low temperature environments, due to the adverse effects of low temperature on the engine lubrication system and the negative impact on the charging performance of the high-voltage battery, for a period of time after starting, the engine's operating noise, vibration and harshness (NVH) performance is not ideal during the process of increasing power generation, which may have a certain impact on the driving experience.

[0003] The current startup strategy is executed based on the system startup request. In an extremely low temperature environment, the battery charging power will be limited due to the poor lubrication effect of the lubrication system. Figure 2 As shown, after the range extender is started, attempting to increase power generation may cause the battery to overcharge. Furthermore, in this scenario, the noise, vibration, and harshness (NVH) performance of the low-power generator engine is suboptimal. Once started, the battery initiates a heating request, which increases the load on the PTC (positive temperature coefficient thermistor). Although power generation can be increased in response to the increased PTC load, the system's NVH performance remains poor during this process. Specifically, after starting in extremely low temperatures, the range extender's power generation and speed show a clear trend: increasing with the gradual increase in PTC (positive temperature coefficient) heater power. During this dynamic change, the engine's NVH (noise, vibration, and harshness) performance is relatively poor, negatively impacting the driving experience.

[0004] A low-temperature starting method of a range-extender hybrid vehicle disclosed in patent CN117284267A includes: controlling the engine to operate at a preset power; determining whether the temperature of the engine reaches the minimum temperature when the engine is allowed to operate at the maximum power; if so, controlling the power battery heating, and controlling the range-extender power within a preset range; determining whether the temperature of the power battery has reached the minimum temperature when the vehicle can be driven; if so, controlling the range-extender output power and the vehicle driving power, so that the power battery is discharged within a preset discharge current range until the power battery reaches the minimum temperature when the maximum discharge power is reached; the NVH performance during the starting process is not ideal. SUMMARY

[0005] To overcome the shortcomings of the prior art, the present application provides a control method for the NVH performance of the range-extender after starting at low temperature, which can effectively improve the NVH performance of the engine when generating power at low power and low speed at low temperature.

[0006] To solve the above technical problems, the technical solution adopted by the present application is:

[0007] The control method for the NVH performance of the range-extender after starting at low temperature includes the following steps:

[0008] When there is a starting request at low temperature, the vehicle control unit sends a heating request to the electric vehicle thermal management system;

[0009] The electric vehicle thermal management system opens the heating unit in advance to heat, and the vehicle control unit delays for a certain time and judges that the working power of the thermal management system reaches a certain value, then requests the generator to drive the engine and ignites to enter the power generation work, and quickly increases the power generation power and speed of the range-extender.

[0010] Further:

[0011] When there is a starting request, the vehicle control unit first sends a starting request to the high-voltage battery system BMS, and the BMS sends a heating request to the thermal management system.

[0012] The vehicle control unit determines whether to send a heating request according to the battery charging power and the battery cell temperature as the judgment condition.

[0013] After the electric vehicle thermal management system receives the heating request demand of the battery BMS, the heating unit is opened to heat.

[0014] After the engine of the range-extender is ignited to complete the starting, the power generation work at a large power and high speed is immediately performed.

[0015] The specific power of the heating unit in the electric vehicle thermal management system is pre-set, and the power of the heating unit increases from 0 to the specific power when it starts working.

[0016] The heating unit is a PTC heater, and the battery and engine reach a certain temperature to restart by the PTC heater power reaching a certain value.

[0017] The vehicle control unit will take the ambient temperature and engine water temperature as the judgment condition.

[0018] The vehicle control unit will control the power generation speed of the range extender between 1300-1500 rpm to avoid the starting problem speed range.

[0019] The vehicle control unit will control the range extender to reach a certain power generation power, and the certain power generation power is the electric vehicle thermal management system load power divided by the system power generation efficiency, plus the DC-DC converter power and the heating unit power.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] The low-temperature range extender starting NVH performance control method is reasonable in design, and after adopting the new starting strategy, the operation process has changed significantly; the PTC is activated and works to a certain power level, and after stable operation, the system starts the range extender. This improved strategy enables the range extender to quickly increase its power generation power and speed, effectively avoiding the problem of poor NVH performance at low speed and low power generation state, thereby significantly improving the overall running stability and comfort. BRIEF DESCRIPTION OF DRAWINGS

[0022] The content expressed by each figure in the specification and the marks in the figure are briefly described as follows:

[0023] Figure 1 It is a low-temperature starting power generation strategy diagram of the present application.

[0024] Figure 2 It is a low-temperature starting power generation strategy diagram of the present application. DETAILED DESCRIPTION

[0025] Although the present application is shown and described herein in accordance with a specific embodiment, the present application is not intended to be limited to the details of the illustrated construction. Rather, various modifications can be made in the details within the scope and range of equivalents of the claims without departing from the application. The specific embodiments of the application will be further described in detail by reference to the drawings, which are described below, and the description of the embodiments.

[0026] As Figure 1As shown, the control method for NVH performance of the range extender after starting at low temperature is a specially designed low-temperature starting strategy and the corresponding control method; effectively solve the problem that the noise, vibration and harshness (NVH) performance of the range extender of the hybrid vehicle with the range extender is not ideal during the starting process in the low-temperature environment; thereby significantly improving the stability and comfort of the overall operation.

[0027] The control strategy for NVH performance of the range extender after starting at low temperature includes the following steps:

[0028] At low temperature (environmental temperature and engine water temperature below-25℃ and battery cell temperature below-20℃), the vehicle control unit determines whether to send a heating request according to the battery charging power, cell temperature, environmental temperature and engine water temperature as the judgment condition; when there is a starting request, the vehicle control unit sends a heating request to the electric vehicle thermal management system;

[0029] The electric vehicle thermal management system opens the heating unit in advance to heat, and the vehicle control unit delays for a certain time and judges that the thermal management system working power reaches a certain value (3-10kw) before requesting the generator to drive the engine and ignite to enter the power generation work, and quickly increasing the power generation power and speed of the range extender.

[0030] And the electric vehicle thermal management system receives the battery BMS heating request or heating demand, and opens the heating unit to heat; the heating unit is a PTC heater, which ensures that the battery and engine reach a certain temperature to start through the PTC heater.

[0031] The battery BMS system continuously monitors the temperature of the battery pack, and the environmental temperature and engine water temperature are detected by setting corresponding temperature sensors, and each temperature sensor transmits the detected temperature data to the vehicle control unit for processing and judgment, and determines whether to open the heating structure to heat and improve the temperature when starting.

[0032] When the environmental temperature and engine water temperature are below-25℃ and the battery cell temperature is below-20℃, the vehicle control unit will send a heating request to the electric vehicle thermal management system after processing and judgment, and the electric vehicle thermal management system will control the heating structure to heat the battery and the engine of the range extender, and when the battery and the engine of the range extender reach a certain temperature, the generator is requested to drive the engine and ignite to enter the power generation work, and the engine of the range extender is ignited to start, and immediately performs power generation work with large power and high speed. Preferably, the vehicle control unit controls the power generation speed of the range extender to be between 1300-1500rpm, avoiding the starting problem speed range.

[0033] After the new starting strategy is adopted, the operation flow has changed significantly; the PTC is activated and works to a specific power level set in advance, and the range extender is started only after the system is stably running, this improved strategy enables the range extender to quickly increase its power generation and speed, effectively avoiding the problem of poor NVH performance in the low-speed and low-power generation state, thereby significantly improving the overall running stability and comfort.

[0034] Further,

[0035] When there is a starting request, the vehicle control unit first sends a starting request to the high-voltage battery system BMS, and the BMS sends a heating request to the thermal management system, which can set the corresponding system architecture according to the actual situation of the vehicle. The BMS system is both the executor of high-voltage power-on (control contactor) and the judge of thermal demand. When the BMS receives the starting instruction of the VCU, if it detects that the battery temperature is lower than the set value, it will immediately delay the closing of the high-voltage contactor (because at this time it cannot directly discharge large current) and send a heating request to the thermal management controller.

[0036] The specific power of the heating unit in the electric vehicle thermal management system is set in advance, and the power of the heating unit increases from 0 to a specific power when it starts working. The vehicle control unit will control the range extender to reach a specific power generation, and the specific power generation is the load power of the electric vehicle thermal management system divided by the system power generation efficiency, plus the DC-DC converter power and the heating unit power.

[0037] The range extender is started only after the heating unit has been stably running for a period of time; this improved strategy enables the range extender to quickly increase its power generation and speed, effectively avoiding the problem of poor NVH performance in the low-speed and low-power generation state.

[0038] The preferred specific examples of the present application are:

[0039] The present application proposes an innovative control strategy for optimizing the starting of a range-extender electric vehicle under extremely low temperature conditions and its implementation method, solving the problem of noise, vibration and harshness (NVH) performance after the engine starts in extremely cold environments.

[0040] At extremely low temperatures, the VCU (Vehicle Control Unit) determines the battery charging power and the battery cell temperature (judges the extremely low temperature condition). When the system has a start request, the VCU first sends a start request to the high-voltage battery system BMS, and the BMS sends a heating request to the TMS (Electric Vehicle Thermal Management System). Or the VCU sends a heating request to the thermal management TMS system (according to the system architecture). The TMS opens the PTC heating in advance (sometimes the user forgets to turn on the air conditioning heating, or some traditional fuel vehicle users do not turn on the air conditioning heating at low temperature, and wait until the engine is hot before turning on the air conditioning heating). The PTC works to increase the system load power, and the VCU delays for a certain time and judges that the TMS working power reaches a certain value, and then requests the generator to drive the engine and ignites to enter the power generation state, and quickly increases the power generation power and speed. In this way, the VCU can quickly increase the power generation power and speed of the range extender, and can generate power at a large power and high speed after starting, which improves the NVH performance of the engine at low power and low speed during power generation at low temperature.

[0041] Specifically:

[0042] Under extreme low temperature environmental conditions, the vehicle control unit (VCU) will comprehensively judge multiple key parameters, including environmental temperature, engine water temperature, battery cell temperature, and battery charging power, to determine whether the extremely low temperature condition required for starting is met. This series of judgments is to ensure that the vehicle can start safely and effectively in a low temperature environment.

[0043] When the system detects a start demand, the VCU will first send a start request state to the battery management system (BMS). After receiving the start request, the BMS will send a heating state request to the thermal management system (TMS). After receiving the request, the TMS will start and enable the PTC (Positive Temperature Coefficient Thermistor) heater to work to a certain power level. This step is to ensure that the battery and engine can start at a suitable temperature.

[0044] After the PTC heater reaches a certain power, the VCU will perform a start action and request the ISG (Integrated Starter Generator) to drive the engine. The ISG will drive the engine to rotate, and when the speed reaches the required speed for fuel injection, the system will enable fuel injection and ignition. The engine management system (EMS) will complete the starting process and turn the engine into a series power generation state.

[0045] After the engine starts and turns into the state of generating electricity, the VCU requests a higher generating speed (for example, 1400 rpm) to avoid the speed range that may cause noise, vibration and harshness (NVH) problems. At the same time, the VCU also requests a higher generating power, which is determined by dividing the system load power by the system generating efficiency, and adding the DCDC (Direct Current-Direct Current Converter) power and the PTC power. Such a setting is to ensure that the system does not overcharge or continuously discharge during the generating process, thereby ensuring the stability and safety of the system.

[0046] After starting in an extremely low temperature environment, the generating power and speed of the range extender show a clear trend of increasing with the gradual increase of the PTC (Positive Temperature Coefficient Heater) power according to the traditional starting strategy. Due to the high power demand of the PTC heater, the generating power and speed of the range extender will increase sharply to meet the huge power demand of the PTC. In this dynamic change process, the NVH (Noise, Vibration and Harshness) of the engine performs relatively poorly. Even sudden roaring and violent shaking may occur, which is in sharp contrast to the quiet and smooth pure electric driving, and destroys the high-end feel of the electric vehicle.

[0047] After adopting the new starting strategy, during the low-temperature starting and generating process, when the system has a starting request, the VCU first requests the BMS (or directly requests the TMS according to the system architecture) to start the PTC. After the PTC works to a certain power, the battery and the engine reach a certain temperature, and then the range extender is started and directly generates a large power and a high speed. This effectively improves the NVH performance of low power and low speed generating at low temperature, significantly improves the quietness and ride comfort in the vehicle, and the driver and passengers almost feel the abrupt start and operation of the range extender, which is closer to the smooth experience of pure electric driving.

[0048] The above only describes the preferred embodiments of the present application, and the above technical features can be arbitrarily combined to form multiple embodiments of the present application.

[0049] The above describes the present application in conjunction with the drawings, and it is obvious that the specific implementation of the present application is not limited by the above manner. Any non-essential improvement or direct application of the concept and technical solution of the present application to other occasions is within the protection scope of the present application.

Claims

1. A method for controlling NVH performance after starting a range extender at low temperatures, characterized by: The control method comprises the following steps: At low temperatures, when there is a start request, the vehicle control unit sends a heating request to the electric vehicle thermal management system; The electric vehicle thermal management system turns on the heating unit in advance for heating. The vehicle control unit delays for a certain period of time and determines that the working power of the thermal management system has reached a certain value. It then requests the generator to drag the engine and ignite to start power generation, and quickly increase the range extender's power generation power and speed.

2. The method for controlling NVH performance after starting a range extender at low temperatures according to claim 1, characterized in that: When there is a start request, the vehicle control unit first sends the start request to the high-voltage battery system BMS, and the BMS then sends a heating request to the thermal management system.

3. The method for controlling NVH performance after starting the range extender at low temperatures as claimed in claim 1, characterized in that: The vehicle control unit determines whether to send a heating request based on the battery charging power and the battery cell temperature as judgment conditions.

4. The method for controlling NVH performance after starting a range extender at low temperatures as claimed in claim 1, characterized in that: After receiving the battery BMS heating request, the electric vehicle thermal management system turns on the heating unit for heating.

5. The method for controlling NVH performance after starting the range extender at low temperature according to claim 1, characterized in that: After the engine of the range extender is ignited and started, it immediately starts generating electricity at a relatively high power and high speed.

6. The method for controlling NVH performance after starting the range extender at low temperatures as claimed in claim 1, characterized in that: The electric vehicle thermal management system pre-sets a specific power for the heating unit, and the power of the heating unit increases from 0 to the specific power when it starts working.

7. The method for controlling NVH performance after starting a range extender at low temperatures as claimed in claim 1, characterized in that: The heating unit is a PTC heater, which is restarted when the power of the PTC heater reaches a certain value and the battery and the engine reach a certain temperature.

8. The method for controlling NVH performance after starting the range extender at low temperatures as claimed in claim 3, characterized in that: The vehicle control unit also uses the ambient temperature and the engine water temperature as judgment conditions.

9. The method for controlling NVH performance after starting a range extender at low temperatures as claimed in claim 5, characterized in that: The vehicle control unit will control the range extender's power generation speed to be between 1300-1500 rpm to avoid the startup problem speed range.

10. The method for controlling NVH performance after starting the range extender at low temperature as claimed in claim 9, characterized in that: The vehicle control unit controls the range extender to achieve a specific power generation power, which is the load power of the electric vehicle thermal management system divided by the system power generation efficiency, plus the DC-DC converter power and the heating unit power.

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