Cold start control system and method based on vehicle 48V integrated power supply system

Abstract

The present invention discloses a cold start control system based on a vehicle 48V integrated power supply system, which is connected to a vehicle starting system, wherein the vehicle starting system comprises: an engine, an ISG motor arranged at the crankshaft end of the engine, a BSG motor connected to the engine through a belt, and a vehicle controller; the cold start control system comprises: a 12V battery pack, a 36V battery pack, a bidirectional DC / DC converter, a first switch K1, a second switch K2, a third switch K3, a fourth switch K4, a battery management unit, and a temperature sensor. The vehicle controller controls the working mode of the bidirectional DC / DC converter and the off state of the linkage switch group, the third switch K3, and the fourth switch K4 through the battery management unit based on the real-time ambient temperature to adjust the vehicle starting mode. Accordingly, the present invention also discloses a control method of the above-mentioned cold start control system, and a vehicle to which the above-mentioned cold start control system is applied.

Description

Technical Field

[0001] The invention relates to a vehicle control system, and in particular to a cold start control system of a vehicle power supply system. Background Art

[0002] As we all know, the engines of current fuel vehicles generally suffer from ignition failure in winter, especially in northern regions where the temperature is below zero or even below minus 10 degrees for nearly one-third of the year. This situation occurs frequently, greatly affecting the user experience of various types of vehicles and causing trouble to people's normal travel.

[0003] Research has found that the main reasons why the engine is difficult to start in a low-temperature environment are as follows: First, in severe cold climates, the intake temperature in the engine cylinder is low, and the heat dissipates quickly, resulting in problems such as air leakage, which will cause the temperature and pressure in the cylinder to fail to meet the requirements; second, the high viscosity of the engine oil and increased resistance at low temperatures also make the engine difficult to start; third, the pressure in the engine cylinder is small at low temperatures, and the speed and resistance torque required are greater. At this time, the BSG starter pulley is more likely to slip due to the low temperature, resulting in lower transmission efficiency and increasing the pressure of low-temperature starting of the engine.

[0004] The above phenomenon not only causes trouble for ordinary car users, but also brings greater challenges to some special equipment facing harsh environments, such as engineering vehicles and military vehicles, so there is an urgent need to find a solution. In summary, it is necessary to propose a way to solve the problem of fuel vehicles being difficult to start at low temperatures, so as to further improve the vehicle's adaptability and user experience in multiple climates.

[0005] The inventors found that although the traditional 12V battery system can drive the ISG starter (gear transmission) at low temperatures, the battery discharge power decreases at low temperatures and the charging capacity is weak. In extreme cases, a single system 12V battery often cannot fully guarantee the start of the engine. Therefore, in order to meet the requirements of low-temperature starting, the low-temperature rate requirement is extremely high. Often, small-capacity batteries need to withstand a large rate discharge of 20C (about 400A). Therefore, the existing 12V battery capacity is generally greater than 40Ah, which will increase the system cost and volume, but except for cold starting, the 12V battery capacity is basically redundant.

[0006] Therefore, in order to solve the above problems, the present invention proposes a cold start control system and a control method thereof based on a vehicle's 48V integrated power supply system, which can realize intelligent environmental recognition and optimize the vehicle's engine ignition in various situations. Summary of the invention

[0007] One of the purposes of the present invention is to provide a cold start control system based on a vehicle's 48V integrated power supply system. The cold start system can intelligently monitor and feedback in real time and convert the engine's starting mode. It realizes engine drive under multiple working conditions, improves the vehicle's ignition capability in harsh environments, and can improve user experience. At the same time, it provides a solution for special vehicles working in extremely cold environments.

[0008] In order to achieve the above object, the present invention proposes a cold start control system based on a vehicle 48V integrated power supply system, which is connected to a vehicle starting system, wherein the vehicle starting system comprises: an engine, an ISG motor arranged at the crankshaft end of the engine, a BSG motor connected to the engine through a belt, and a vehicle controller; the cold start control system comprises:

[0009] 12V battery pack;

[0010] A 36V battery pack, which is connected to a 12V battery pack via a linkage switch group, wherein the linkage switch group includes a first switch K1 and a second switch K2 with opposite switching actions, wherein when the first switch K1 is closed, the 12V battery pack and the 36V battery pack are connected in series to form a 48V battery pack, and when the second switch K2 is closed, the series connection between the 12V battery pack and the 36V battery pack is disconnected;

[0011] The 12V battery pack is connected to the ISG motor via a third switch K3;

[0012] The 48V battery pack is connected to the BSG motor via a fourth switch K4;

[0013] A bidirectional DC / DC converter, whose ground terminal is connected to the ground terminal of the 12V battery pack, and the ground terminal of the bidirectional DC / DC converter is also connected to the ground terminal of the 36V battery pack through the second switch K2, the low voltage end of the bidirectional DC / DC converter is connected to the ISG motor and the 12V battery pack, and the high voltage end of the bidirectional DC / DC converter is connected to the BSG motor and the 48V battery pack;

[0014] A battery management unit, which is data-connected to the vehicle controller, and is respectively connected to the bidirectional DC / DC converter and the linkage switch group, the third switch K3, and the fourth switch K4;

[0015] A temperature sensor is connected to the vehicle controller, and the temperature sensor collects the real-time ambient temperature and transmits it to the vehicle controller;

[0016] The vehicle controller controls the working mode of the bidirectional DC / DC converter and the off state of the linkage switch group, the third switch K3 and the fourth switch K4 through the battery management unit based on the real-time ambient temperature to adjust the vehicle starting mode.

[0017] The technical solution designed by the present invention realizes engine driving under multiple working conditions through an intelligent implementation detection feedback, namely the engine start mode conversion strategy, which can improve the ignition ability of the whole vehicle in harsh environments, improve the user experience, and provide a solution for special vehicles working in extremely cold environments. The implementation of this technical solution depends on the intelligent start mode conversion strategy designed by the present invention and the new cooperation mode of the battery pack in the 48V integrated power supply system.

[0018] Compared with traditional fuel vehicles that use a single 12V battery system for ignition, the 48V integrated power supply system proposed in this technical solution includes: a 12V battery pack and a 36V battery pack, wherein the 48V battery system formed by connecting the 12V battery pack and the 36V battery pack in series can drive a 48V BSG motor to start the engine using a belt.

[0019] In addition to the above starting mode, the present invention can also use only a 12V battery pack to drive a 12VISG motor to start the engine, which can be applied in multiple working conditions through an intelligent control strategy. Compared with the traditional ignition method, the technical solution proposes to use the real-time monitoring environment signal fed back by the whole vehicle and the corresponding engine starting efficiency and the corresponding preferred starting method to form a mapping relationship to improve the adaptability of the whole vehicle engine to the environment.

[0020] In addition, in the cold start control system designed by the present invention, the 12V battery pack can also work in conjunction with the 36V battery pack to power the 12V ISG motor to start the engine, and its capacity requirement is reduced, which can save about 50% of the 12V battery pack cost and optimize the space layout of the entire vehicle.

[0021] Furthermore, in the cold start control system described in the present invention, the vehicle starting mode includes a 48V driving mode. In the 48V driving mode, the vehicle controller controls the first switch K1 and the fourth switch K4 to be closed, the second switch K2 and the third switch K3 to be disconnected, and the bidirectional DC / DC converter does not work, so that the 48V battery pack formed in series supplies power to the BSG motor, and the BSG motor starts the engine.

[0022] Furthermore, in the cold start control system described in the present invention, the vehicle starting mode includes a 12V driving mode. In the 12V driving mode, the vehicle controller controls the first switch K1 and the fourth switch K4 to be disconnected, the second switch K2 and the third switch K3 to be closed, and the bidirectional DC / DC converter does not work, so that the 12V battery pack alone powers the ISG motor, and the ISG motor starts the engine.

[0023] Furthermore, in the cold start control system described in the present invention, the vehicle starting mode includes a 12V and 36V collaborative driving mode. In this driving mode, the vehicle controller controls the first switch K1 and the fourth switch K4 to be disconnected, and the second switch K2 and the third switch K3 to be closed through the battery management unit, so that the 12V battery pack powers the ISG motor, and the 36V battery pack converts the voltage into 12V through the bidirectional DC / DC converter to power the ISG motor, and the ISG motor starts the engine.

[0024] Correspondingly, another object of the present invention is to provide a control method for a cold start control system of the vehicle 48V integrated power supply system described in the present invention. The control method can intelligently monitor and feedback in real time and convert the start mode of the engine. It can not only eliminate the cold start of the engine in an extremely cold environment, but also realize engine driving under multiple working conditions to enhance the ignition ability of the entire vehicle in harsh environments, thereby improving the user experience.

[0025] In order to achieve the above object, the present invention proposes a control method for a cold start control system of a vehicle 48V integrated power supply system, which comprises the steps of:

[0026] The temperature sensor collects the real-time ambient temperature and transmits it to the vehicle controller;

[0027] The vehicle controller compares the real-time ambient temperature T with the critical temperature t0 at which the BSG motor drives the engine to fail:

[0028] If T ≥ t0, and the real-time driving power P of the 48V battery pack 48V ≥BSG motor minimum starting power P starter，48v , then the vehicle controller controls the vehicle start mode to adopt the 48V drive mode. In the 48V drive mode, the first switch K1 and the fourth switch K4 are closed, the second switch K2 and the third switch K3 are disconnected, the bidirectional DC / DC converter does not work, and the 48V battery pack formed in series supplies power to the BSG motor, which starts the engine;

[0029] If T<t0, the vehicle controller obtains the minimum starting power P of the ISG motor at low temperature based on the real-time ambient temperature T starter，12v and compare it with the real-time driving power P of the 12V battery pack 12V For comparison:

[0030] If P 12V ≥P starter，12v, then the vehicle start mode is controlled to adopt the 12V drive mode. In the 12V drive mode, the first switch K1 and the fourth switch K4 are disconnected, the second switch K2 and the third switch K3 are closed, the bidirectional DC / DC converter does not work, the 12V battery pack alone supplies power to the ISG motor, and the ISG motor starts the engine;

[0031] If P 12V <P starter，12v , the vehicle starting mode is controlled to adopt a 12V and 36V collaborative driving mode. In this driving mode, the first switch K1 and the fourth switch K4 are disconnected, the second switch K2 and the third switch K3 are closed, the 12V battery pack powers the ISG motor, and the 36V battery pack converts the voltage into 12V through a bidirectional DC / DC converter to power the ISG motor, and the ISG motor starts the engine.

[0032] In the above technical solution of the present invention, the minimum starting power P of the BSG motor is starter，48v This parameter is currently known and will not be described in detail here.

[0033] Furthermore, in the control method of the present invention, the real-time driving power P of the 48V battery pack is 48V Based on the following formula:

[0034] P 48V =f 48 (T, SOC, C) × U 48 ×η belt

[0035] Among them, η belt represents the belt transmission efficiency between the BSG motor and the engine, f 48 (T, SOC, C) represents the mapping relationship between the power that the 48V battery pack can provide and the real-time ambient temperature T, the battery charge SOC and the discharge rate C. 48 Indicates the real-time voltage of the monitored 48V battery pack.

[0036] Furthermore, in the control method of the present invention, the minimum starting power P of the ISG motor at low temperature is starter，12v Based on the following formula:

[0037]

[0038] Among them, n engine Indicates the minimum starting speed of the engine, M engine represents the starting resistance torque, η is the transmission efficiency, and k is a constant.

[0039] In the above technical solution of the present invention, the minimum starting power P of the ISG motor at low temperature is calculated. starter，12v The n to be usedengine 、M engine , k and η are all known quantities that can be obtained, and will not be described in detail here.

[0040] Furthermore, in the control method of the present invention, the real-time driving power P of the 12V battery pack is 12V Based on the following formula:

[0041] P 12V =f 12 (T, SOC, C) × U 12 ×η gear

[0042] Among them, f 12 (T, SOC, C) represents the mapping relationship between the power that the 12V battery pack can provide and the real-time ambient temperature T, the battery charge SOC and the discharge rate C. 12 Indicates the real-time voltage of the monitored 12V battery pack, η gear Indicates the gear transmission efficiency.

[0043] Furthermore, in the control method of the present invention, in the 12V and 36V cooperative driving mode, the conversion efficiency η of the bidirectional DC / DC converter is controlled. DCDC , so that the real-time driving power (P 12V +P 36V )≥P starter，12v , where the conversion efficiency of the bidirectional DC / DC converter is DCDC Control based on the following relationship:

[0044] P 12V +P 36V =f 12 (T, SOC, C) × U 12 ×η gear +f 36 (T, SOC, C) × U 36 ×η gear ×η DCDC

[0045] Among them, f 12 (T, SOC, C) represents the mapping relationship between the power that the 12V battery pack can provide and the real-time ambient temperature T, the battery charge SOC and the discharge rate C. 12 Indicates the real-time voltage of the monitored 12V battery pack, f 36 (T, SOC, C) represents the mapping relationship between the power that a 36V battery pack can provide and the real-time ambient temperature T, the battery charge SOC, and the discharge rate C. 36 Indicates the real-time voltage of the 36V battery pack monitored, η gear Indicates the gear transmission efficiency.

[0046] In addition, the present invention also discloses a vehicle having the above-mentioned cold start control system based on the vehicle 48V integrated power supply system of the present invention.

[0047] Compared with the prior art, the cold start control system based on the vehicle 48V integrated power supply system and the control method thereof according to the present invention have the following advantages:

[0048] (1) The present invention provides a new cold start control system and designs its own control method accordingly, which can intelligently switch the cold start mode of the vehicle engine according to different working conditions to meet the engine driving requirements in different situations. The system can drive the 48V BSG motor and the 12V ISG motor respectively. Under this design concept, it is necessary to have a modular working requirement for the 48V battery system so as to control the 12V battery pack and the 36V battery pack separately or coordinately, thereby designing different driving modes.

[0049] (2) The cold start control system and control method described in the present invention can select a driving mode that matches the engine operation according to different working conditions to obtain the best energy efficiency. For example, when the engine is driven at room temperature, the energy consumption of directly using a 48V BSG motor is less than that of a 12V ISG motor. In this case, the 48V driving mode can be specifically selected; when the engine is driven at low temperature, the 12V battery pack can be preferably driven alone, that is, the 12V driving mode, which can save the loss generated by the bidirectional DCDC converter converting 36V to 12V.

[0050] (3) In addition, in actual application, the strategy process of the control method of the cold start control system described in the present invention can further define the battery charge at the lowest predetermined operating temperature for engine start-up. Adding this operating condition to the battery charging and discharging strategy can effectively avoid the situation where the vehicle cannot be started due to insufficient battery charge. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A control schematic diagram of a cold start control system based on a vehicle 48V integrated power supply system according to the present invention in one implementation is shown.

[0052] Figure 2 A control flow chart schematically shows a cold start control system according to the present invention for switching start modes for a specific application scenario in one implementation.

[0053] Figure 3 The flowchart of implementing the intelligent charging request under the cold start strategy of the control method of the cold start control system according to the present invention is schematically shown. DETAILED DESCRIPTION

[0054] The cold start control system and control method thereof based on the vehicle 48V integrated power supply system described in the present invention will be further explained and illustrated below in conjunction with the drawings in the specification and specific embodiments. However, such explanation and illustration do not constitute an improper limitation on the technical solution of the present invention.

[0055] Figure 1 A control schematic diagram of a cold start control system based on a vehicle 48V integrated power supply system according to the present invention in one implementation is shown.

[0056] like Figure 1 As shown, in this embodiment, in the current vehicle, the vehicle starting system may specifically include: an engine 106; a 12V ISG motor 105 provided at the crankshaft end of the engine; a 48V BSG motor 104 connected to the engine 106 via a belt 107, and a vehicle controller. The belt 107 can connect the engine 106 and the BSG motor 104, so that the movement of the two can be linked.

[0057] In the present invention, the designed cold start control system can be connected to the vehicle's starting system. In this embodiment, the cold start control system of the present invention is specifically provided with: 12V battery pack 101, 36V battery pack 102, bidirectional DC / DC converter 103, battery management unit and temperature sensor. Among them, the designed vehicle controller, temperature sensor and battery management unit are not in the above Figure 1 It is shown in .

[0058] From the above Figure 1 It is not difficult to see that in this embodiment, the engine in the vehicle starting system will be driven to work in two situations: one is through the 48V BSG motor 104 through the belt 107; the other is through the traditional 12V ISG motor 105 using gear transmission.

[0059] The 48V BSG motor 104 integrates the functions of a traditional generator and a starter. When the engine 106 in the vehicle starting system is in a stagnant state, the BSG motor 104 can drive the generator 106 to work through the belt 107 and the pulley, thereby playing the role of a traditional starter; when the engine 106 is in a working state, the engine can use the belt 107 to drive the BSG motor 104 to generate electricity, thereby charging the battery, and at this time the BSG motor 104 plays the role of a traditional generator.

[0060] The 12V ISG motor (starter) 105 is directly connected to the crankshaft output end of the engine 106. When the engine 106 needs to be started, the ISG motor 105 can directly drive its crankshaft end to start the engine 106. Conversely, when the engine 106 is in operation, the engine 106 can also drive the ISG motor 105 through the crankshaft end to charge the battery.

[0061] Accordingly, see further Figure 1 It can be seen that in this embodiment, in the cold start control system designed by the present invention:

[0062] The 12V battery pack 101 specifically adopts a 1-in-parallel 4-in-series structure, which can provide energy for the 12V ISG motor 105 to drive the engine 106 .

[0063] The 36V battery pack 102 specifically adopts a 1-in-10 series structure, which can provide energy to the 12V ISG motor 105 through the DC / DC converter 103 alone, or it can be connected in series with the 12V battery pack 101 to form a 48V battery to provide power to the 48V BSG motor 104, thereby driving the start of the vehicle engine 106 through the belt 107.

[0064] The bidirectional DCDC converter 103 can realize bidirectional conversion, which can convert the 48V / 36V voltage into 12V, and can also convert the 12V / 36V voltage into 48V.

[0065] In addition, in the cold start control system, four switches are correspondingly provided, namely the first switch K1 (i.e. Figure 1 As shown in K1), the second switch K2 (ie Figure 1 K2), the third switch K3 (i.e. Figure 1 K3) and the fourth switch K4 (ie Figure 1 K4). The first switch K1 and the second switch K2 can cooperate to form a linkage switch group. The first switch K1 and the second switch K2 are a pair of linkage switches, and the actions of the two are opposite. When the first switch K1 is closed, the second switch K2 is open, and vice versa.

[0066] Accordingly, for the convenience of analysis, the connection relationship between the various components in the cold start control system designed by the present invention is described below.

[0067] In the technical solution designed by the present invention, the 36V battery pack 102 can be connected to the 12V battery pack 101 through the first switch K1 and the second switch K2. When the first switch K1 is closed, the 12V battery pack 101 and the 36V battery pack 102 are connected in series to form a 48V battery pack, and when the second switch K2 is closed, the series connection between the 12V battery pack 101 and the 36V battery pack 102 is disconnected.

[0068] Correspondingly, the 12V battery pack 101 of the present invention is also connected to the ISG motor 105 via the third switch K3; the 48V battery pack formed by the 12V battery pack 101 and the 36V battery pack 102 being connected in series can be connected to the BSG motor 104 via the fourth switch K4.

[0069] In addition, the ground terminal of the bidirectional DC / DC converter 103 designed in the present invention can be connected to the ground terminal of the 12V battery pack 101, and the ground terminal of the converter is also connected to the ground terminal of the 36V battery pack 102 through the second switch K2. The low voltage end of the bidirectional DC / DC converter 103 is connected to the ISG motor 105 and the 12V battery pack 101, and the high voltage end of the bidirectional DC / DC converter 103 can be connected to the BSG motor 104 and the 48V battery pack.

[0070] In addition, it should be noted that in the cold start control system designed by the present invention, a battery management unit and a temperature sensor are also provided. The battery management unit can be connected to the vehicle controller data, and is connected to the bidirectional DC / DC converter 103 and the linkage switch group (including the first switch K1 and the second switch K2 with opposite actions), the third switch K3 and the fourth switch K4 respectively.

[0071] The designed temperature sensor can also be connected to the vehicle controller in the vehicle starting system, and the temperature sensor can collect the real-time ambient temperature and transmit it to the vehicle controller. The designed vehicle controller can control the working mode of the bidirectional DC / DC converter 103 and the off state of the linkage switch group, the third switch K3 and the fourth switch K4 through the battery management unit based on the real-time ambient temperature to adjust the vehicle starting mode.

[0072] In summary, the vehicle starting system designed by the present invention can specifically include three starting modes, including: 48V driving mode, 12V driving mode and 12V and 36V coordinated driving mode:

[0073] (1) 48V drive mode:

[0074] In the 48V driving mode, the vehicle controller controls the first switch K1 and the fourth switch K4 to close, the second switch K2 and the third switch K3 to open through the battery management unit, the 12V battery pack 101 and the 36V battery pack 102 form a series circuit, and the bidirectional DC / DC converter 103 does not work, so that the 48V battery pack formed in series supplies power to the BSG motor 104, the BSG motor 104 drives the belt 107 to rotate, and the engine 106 connected to the belt 107 moves accordingly, thereby starting the engine 106.

[0075] (2) 12V drive mode:

[0076] In the 12V driving mode, the vehicle controller controls the first switch K1 and the fourth switch K4 to be disconnected, the second switch K2 and the third switch K3 to be closed through the battery management unit, the series circuit of the 12V battery pack 101 and the 36V battery pack 102 is disconnected, and the bidirectional DC / DC converter 103 does not work, so that the 12V battery pack 101 alone powers the ISG motor 105, and the ISG motor 105 starts the engine 106.

[0077] (3) 12V and 36V collaborative driving mode:

[0078] In this driving mode, the vehicle controller controls the first switch K1 and the fourth switch K4 to be disconnected and the second switch K2 and the third switch K3 to be closed through the battery management unit, so that the 12V battery pack 101 supplies power to the ISG motor 105, and the 36V battery pack 102 converts the voltage into 12V through the bidirectional DC / DC converter 103 to supply power to the ISG motor 105, and the ISG motor 105 starts the engine.

[0079] Based on the designed three engine driving modes, the cold start control system designed by the present invention can intelligently select the above three modes for switching under different environments and different working conditions to improve the environmental adaptability of vehicle startup and the user experience.

[0080] Figure 2 A control flow chart schematically shows a cold start control system according to the present invention for switching start modes for a specific application scenario in one implementation.

[0081] The present invention is designed Figure 2 This is the specific implementation process of the cold start strategy intelligent switching mode. In this embodiment, after receiving the user's request to start the whole vehicle, the cold start control system can make a strategy judgment based on the real-time environmental monitoring results and automatically switch to the optimal mode to start the engine.

[0082] like Figure 2 As shown, in this embodiment, the control method of the cold start control system may specifically include the following steps:

[0083] S1001: The cold start control system starts.

[0084] S1002: The passenger performs a starting operation through the vehicle controller to input a vehicle starting demand to the cold start control system, and the engine receives a starting command.

[0085] S1003, S1004: The temperature sensor monitors the real-time ambient temperature T and transmits it to the vehicle controller. The temperature sensor's measurement range is generally between -55°C and 160°C.

[0086] S1005: The vehicle controller compares the real-time ambient temperature T with the critical temperature t0 of the BSG motor-driven engine failure; if T≥t0, proceed to the subsequent step S1006; if T<t0, proceed to the subsequent step S1011.

[0087] S1006-S1010: Real-time ambient temperature T ≥ t0, and real-time driving power P of 48V battery pack 48V ≥BSG motor minimum starting power P starter，48v (this parameter is currently known), the vehicle controller controls the vehicle starting mode to adopt the 48V drive mode. In the 48V drive mode, the first switch K1 and the fourth switch K4 are closed, the second switch K2 and the third switch K3 are disconnected, the bidirectional DC / DC converter does not work, and the 48V battery pack formed by the 12V battery pack and the 36V battery pack in series can power the BSG motor. The BSG motor drives the engine through belt drive, thereby driving the engine to start normally (i.e., the subsequent step S1020).

[0088] It should be noted that in the present invention, the calculation of the driving power of the 48V battery needs to consider the maximum release power of the battery under specific conditions and the belt transmission efficiency ηbelt between the starter and the engine. The power that the battery can provide under specific conditions is affected by the external temperature, the battery charge (SOC) and the discharge rate (C), and the corresponding relationship satisfies the f(T, SOC, C) mapping table. Under specific temperature and SOC conditions, the maximum battery rate C can be retrieved in real time through the traversal method, and the real-time voltage U is detected under the discharge rate C.

[0089] The maximum output power P1 of the battery is calculated as follows:

[0090] P1=f 48 (T,SOC,C)×U 48

[0091] Accordingly, the real-time driving power P of the 48V battery pack is 48V The calculation method is:

[0092] P48V =f 48 (T,SOC,C)×U 48 ×η belt

[0093] Among them, η belt represents the belt transmission efficiency between the BSG motor and the engine (it is a fixed value related to the device, for example, it can be 0.96), f 48 (T, SOC, C) represents the mapping relationship between the power that the 48V battery pack can provide and the real-time ambient temperature T, the battery charge SOC and the discharge rate C. 48 Indicates the real-time voltage of the monitored 48V battery pack.

[0094] S1011: If the real-time ambient temperature T is less than t0, the second-level judgment strategy is entered. The vehicle controller uses the real-time ambient temperature T as an input value and obtains the minimum starting power P of the ISG motor at low temperature based on the real-time ambient temperature T. starter，12v , and set the minimum starting power P starter，12v Real-time driving power P with 12V battery pack 12V When P 12V ≥P starter，12v , then proceed to the subsequent step S1012; when P 12V <P starter，12v , then proceed to the subsequent step S1017.

[0095] In the above step S1011, in order to obtain the minimum starting power P of the ISG motor at low temperature starter，12v , we can first calculate the engine start real-time power P engine , P engine Depends on the minimum starting speed of the engine n engine (unit parameter is r / min) and starting resistance torque M engine (Unit parameter is Nm), which are all known quantities that can be obtained.

[0096] Engine start real-time power P engine The calculation formula is as follows:

[0097] P engine =(M engine ×n engine ) / k

[0098] Generally, once the engine is selected, its minimum starting speed n engine And starting resistance torque M engine is a fixed value. In the range of 0-20℃, the minimum starting speed n engine It can be 35r / min-50r / min. At lower temperatures, more losses need to be considered. The minimum starting speed is n engineRefer to 50r / min-100r / min. Correspondingly, the starting resistance torque M of the engine at low temperature engine It increases with the decrease of temperature. It can be tested according to the actual situation. Here, the starting resistance torque M is given as the temperature decreases by 5℃ below 0℃. engine Capable of increasing up to 2.5Nm.

[0099] Minimum starting power P of ISG motor at low temperature starter，12v Obtained by the following formula:

[0100]

[0101] Among them, n engine Indicates the minimum starting speed of the engine; M engine represents the starting resistance torque; η is the transmission efficiency, which can be 0.85-0.90; k is a constant, and the general value of k is 9550. η and k are also known quantities that can be obtained.

[0102] In addition, in the above step S1011, it is also necessary to calculate the real-time driving power P of the 12V battery pack. 12V The calculation method is similar to the above, the difference is: in addition to considering the battery factor, the 12V battery pack starting the engine also needs to consider the conversion efficiency between the starter and the ISG motor crankshaft gear.

[0103] Therefore, in this technical solution, the real-time driving power P of the 12V battery pack is 12V Obtained by the following formula:

[0104] P 12V =f 12 (T,SOC,C)×U 12 ×η gear

[0105] Among them, f 12 (T, SOC, C) represents the mapping relationship between the power that a 12V battery pack can provide and the real-time ambient temperature T, the battery charge SOC, and the discharge rate C; U 12 Indicates the real-time voltage of the monitored 12V battery pack; η gear Indicates the gear transmission efficiency, which is generally 0.94 to 0.99.

[0106] S1012-S1016: Determine P 12V ≥P starter，12v, then the second-level strategy determines that the power of the 12V battery pack is sufficient to drive the engine alone, and needs to enter the 12V driving mode. In this driving mode, the vehicle start mode is controlled to adopt the 12V driving mode. In the 12V driving mode, the first switch K1 and the fourth switch K4 are disconnected, the second switch K2 and the third switch K3 are closed, the bidirectional DC / DC converter does not work, and the 12V battery pack alone supplies power to the ISG motor. The ISG motor starts to work, thereby driving the crankshaft connected to it to move, the engine crankshaft moves, and the engine starts normally (i.e., the subsequent step S1020).

[0107] S1017-S1019: Determine P 12V <P starter，12v , then the second-level strategy determines that the power of the 12V battery pack is not enough to drive the engine alone, and it is necessary to enter the 12V and 36V collaborative drive mode. At this time, the system receives a mode switching instruction and enters the 12V and 36V collaborative drive ignition preparation mode. In this drive mode, the first switch K1 and the fourth switch K4 are disconnected, the second switch K2 and the third switch K3 are closed, the 12V battery pack supplies power to the ISG motor, the bidirectional DC / DC converter starts working, and the 12V battery pack and the 36V battery pack form a closed loop with the ISG motor respectively. At this time, the 12V battery pack supplies power to the ISG motor, and the 36V battery pack converts the voltage to 12V in another loop through the bidirectional DC / DC converter to power the ISG motor. The ISG motor starts working, thereby driving the crankshaft connected to it to move, the engine crankshaft moves, and the engine starts normally.

[0108] In the 12V and 36V collaborative driving mode, the power released by the battery in this working mode is provided by both the 12V battery pack and the 36V battery pack. The 12V battery pack can directly power the load, and the 36V battery pack needs to be converted through a bidirectional DC / DC converter to convert 36V to 12V to power the load. The DCDC conversion efficiency needs to be considered here.

[0109] Controlling the conversion efficiency η of a bidirectional DC / DC converter DCDC , so that the real-time driving power (P 12V +P 36V )≥P starter，12v , where the conversion efficiency of the bidirectional DC / DC converter is DCDC Control based on the following relationship:

[0110] P 12V +P 36V =f 12 (T,SOC,C)×U 12 ×η gear +f 36 (T,SOC,C)×U 36 ×ηgear ×η DCDC

[0111] Among them, f 12 (T, SOC, C) represents the mapping relationship between the power that a 12V battery pack can provide and the real-time ambient temperature T, the battery charge SOC, and the discharge rate C; U 12 Indicates the real-time voltage of the monitored 12V battery pack; f 36 (T, SOC, C) represents the mapping relationship between the power that a 36V battery pack can provide and the real-time ambient temperature T, the battery charge SOC, and the discharge rate C; U 36 Indicates the real-time voltage of the monitored 36V battery pack; η gear Indicates the gear transmission efficiency, which is generally 0.94 to 0.99; η DCDC Indicates the DCDC conversion efficiency, which is generally 95% to 97%.

[0112] S1020: After the engine is successfully started, the entire process ends.

[0113] To sum up, the cold start system designed by the present invention based on the vehicle's 48V integrated power supply system can intelligently monitor feedback in real time and convert the engine's starting mode, which realizes engine drive under multiple working conditions, improves the vehicle's ignition ability in harsh environments, and can improve user experience.

[0114] Accordingly, from the above Figure 2 It is not difficult to see from the technical solution shown that, based on the above working conditions, the cold start control system of the vehicle 48V integrated power supply system of the present invention is based on at least the environmental condition of the real-time ambient temperature T≥t0, so as to meet the BSG motor starting engine power, thereby requiring the battery system to meet the minimum SOC under this working condition, which can be achieved through P 48V ≥P starter，48v The required battery SOC value can be inferred from the relationship.

[0115] Similarly, in the 12V and 36V cooperative driving modes, the engine driving power should at least meet the real-time ambient temperature T at the preset minimum ambient temperature, which can be obtained by P 12V+36V ≥P starter12v The relationship is used to derive the battery SOC requirement at a preset ultra-low temperature, thereby ensuring the environmental adaptability of the battery system under multiple working conditions.

[0116] Figure 3 The flowchart of implementing the intelligent charging request under the cold start strategy of the control method of the cold start control system according to the present invention is schematically shown.

[0117] S100: Real-time SOC identification and intelligent charging strategy process based on cold start requirements.

[0118] S101: Start the process.

[0119] S102: Starter (motor) power P under preset minimum temperature limit starter As input, the minimum battery power required to power the starter must meet this starting power.

[0120] S103: The vehicle controller compares the real-time ambient temperature T with the critical temperature t0 of the BSG motor-driven engine failure, and enters the subsequent step S104 when T≥t0, and enters the subsequent step S110 when T<t0.

[0121] S104: T ≥ t0, then the real-time driving power P of the 48V battery pack 48V ≥BSG motor minimum starting power P starter，48v .

[0122] S105: Under the conditions of real-time ambient temperature T and the multiple C when the minimum speed is met, the real-time power of the 48V battery pack is based on f 48 The (T, SOC, C) mapping table traversal result must meet the minimum starting power P of the BSG motor. starter，48v In this case, the battery pack meets the requirement of SOC of 30%.

[0123] S106: To meet the minimum SOC requirement, the battery SOC needs to be monitored in real time to facilitate early identification of low battery status.

[0124] S107: Identify and diagnose the real-time SOC of the 48V battery pack to determine whether the power level is less than 30%. If the power level is greater than or equal to 30%, proceed to the subsequent step S109; if the power level is less than 30%, proceed to the subsequent step S108.

[0125] S108: When the real-time SOC of the 48V battery pack is less than 30%, the 48V battery system requests charging of the battery.

[0126] S109: When the real-time SOC of the 48V battery pack is ≥30%, the 48V battery system meets the minimum starting requirements and does not need to be charged temporarily.

[0127] S110: T<t0, then the 12V and 36V battery packs must meet the starting power requirements under low temperature conditions when working together, that is, P 12V+36V ≥P starter，12v .

[0128] S111: Under the conditions of real-time ambient temperature T and the multiple C when the minimum speed is met, the real-time power of the 12V and 36V battery packs is calculated based on f 12 (T, SOC, C) and f 36(T, SOC, C) mapping table traversal, the 12V and 36V battery superposition power in this state must meet the starting power P starter，12v In this case, the battery pack meets the requirement of SOC of 30%.

[0129] S113: Identify and diagnose the real-time SOC of the 12V and 36V battery packs to determine whether the power level is less than 30%. If the power level is greater than or equal to 30%, proceed to the subsequent step S115; if the power level is less than 30%, proceed to the subsequent step S114.

[0130] S114: At this time, SOC < 30%, and the 48V battery system requests to charge the battery.

[0131] S115: At this time, SOC ≥ 30%, and the 48V battery system meets the minimum starting requirements and does not need to be charged temporarily.

[0132] S116: Through the above-mentioned diagnostic identification steps and intelligent charging behavior, it can be ensured that the battery SOC state meets the real-time starting requirements.

[0133] S117: The process ends.

[0134] In addition, the combination of the various technical features in this case is not limited to the combination described in the claims of this case or the combination described in the specific embodiments. All technical features recorded in this case can be freely combined or combined in any way unless there is a contradiction between them.

[0135] It should also be noted that the above-listed embodiments are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made therewith can be directly derived or easily associated with by those skilled in the art from the contents disclosed in the present invention, and all should belong to the protection scope of the present invention.

Claims

1. A control method for a cold start control system of a 48V integrated power supply system of a vehicle, characterized in that: It is implemented based on the cold start control system of the vehicle's 48V integrated power supply system, and the cold start control system is connected to the vehicle starting system, and the vehicle starting system includes: an engine, an ISG motor arranged at the crankshaft end of the engine, a BSG motor connected to the engine through a belt, and a vehicle controller; the cold start control system includes: 12V battery pack; A 36V battery pack, which is connected to a 12V battery pack via a linkage switch group, wherein the linkage switch group includes a first switch K1 and a second switch K2 with opposite switching actions, wherein when the first switch K1 is closed, the 12V battery pack and the 36V battery pack are connected in series to form a 48V battery pack, and when the second switch K2 is closed, the series connection between the 12V battery pack and the 36V battery pack is disconnected; The 12V battery pack is connected to the ISG motor via a third switch K3; The 48V battery pack is connected to the BSG motor via a fourth switch K4; A bidirectional DC / DC converter, whose ground terminal is connected to the ground terminal of the 12V battery pack, and the ground terminal of the bidirectional DC / DC converter is also connected to the ground terminal of the 36V battery pack through the second switch K2, the low voltage end of the bidirectional DC / DC converter is connected to the ISG motor and the 12V battery pack, and the high voltage end of the bidirectional DC / DC converter is connected to the BSG motor and the 48V battery pack; A battery management unit, which is data-connected to the vehicle controller, and is respectively connected to the bidirectional DC / DC converter and the linkage switch group, the third switch K3, and the fourth switch K4; A temperature sensor is connected to the vehicle controller, and the temperature sensor collects the real-time ambient temperature and transmits it to the vehicle controller; The vehicle controller controls the working mode of the bidirectional DC / DC converter and the off state of the linkage switch group, the third switch K3 and the fourth switch K4 through the battery management unit based on the real-time ambient temperature to adjust the vehicle start mode; The control method comprises the steps of: The temperature sensor collects the real-time ambient temperature and transmits it to the vehicle controller; The vehicle controller compares the real-time ambient temperature T with the critical temperature t0 at which the BSG motor drives the engine to fail: If T ≥ t0, and the real-time driving power P of the 48V battery pack 48V ≥BSG motor minimum starting power P starter，48v , then the vehicle controller controls the vehicle start mode to adopt the 48V drive mode. In the 48V drive mode, the first switch K1 and the fourth switch K4 are closed, the second switch K2 and the third switch K3 are disconnected, the bidirectional DC / DC converter does not work, and the 48V battery pack formed in series supplies power to the BSG motor, which starts the engine; If T<t0, the vehicle controller obtains the minimum starting power P of the ISG motor at low temperature based on the real-time ambient temperature T starter，12v and compare it with the real-time driving power P of the 12V battery pack 12V For comparison: If P 12V ≥P starter，12v , then the vehicle start mode is controlled to adopt the 12V drive mode. In the 12V drive mode, the first switch K1 and the fourth switch K4 are disconnected, the second switch K2 and the third switch K3 are closed, the bidirectional DC / DC converter does not work, the 12V battery pack alone supplies power to the ISG motor, and the ISG motor starts the engine; If P 12V <P starter，12v , the vehicle starting mode is controlled to adopt a 12V and 36V collaborative driving mode. In this driving mode, the first switch K1 and the fourth switch K4 are disconnected, the second switch K2 and the third switch K3 are closed, the 12V battery pack powers the ISG motor, and the 36V battery pack converts the voltage into 12V through a bidirectional DC / DC converter to power the ISG motor, and the ISG motor starts the engine.

2. The control method according to claim 1, characterized in that: The real-time driving power P of the 48V battery pack 48V Based on the following formula: P 48V =f 48 (T,SOC,C)×U 48 ×η belt Among them, η belt represents the belt transmission efficiency between the BSG motor and the engine, f 48 (T, SOC, C) represents the mapping relationship between the power that the 48V battery pack can provide and the real-time ambient temperature T, the battery charge SOC and the discharge rate C. 48 Indicates the real-time voltage of the monitored 48V battery pack.

3. The control method according to claim 1, characterized in that: The minimum starting power P of ISG motor at low temperature starter，12v Based on the following formula: Among them, n engine Indicates the minimum starting speed of the engine, M engine represents the starting resistance torque, η is the transmission efficiency, and k is a constant.

4. The control method according to claim 1, characterized in that: The real-time driving power P of the 12V battery pack 12V Based on the following formula: P 12V =f 12 (T,SOC,C)×U 12 ×η gear Among them, f 12 (T, SOC, C) represents the mapping relationship between the power provided by the 12V battery pack and the real-time ambient temperature T, the battery charge SOC and the discharge rate C. 12 Indicates the real-time voltage of the monitored 12V battery pack, η gear Indicates the gear transmission efficiency.

5. The control method according to claim 1, characterized in that: Controlling the conversion efficiency η of the bidirectional DC / DC converter in 12V and 36V cooperative driving mode DCDC , so that the real-time driving power (P 12V +P 36V )≥P starter，12v , where the conversion efficiency of the bidirectional DC / DC converter is DCDC Control based on the following relationship: P 12V +P 36V =f 12 (T,SOC,C)×U 12 ×η gear +f 36 (T,SOC,C)×U 36 ×η gear ×η DCDC Among them, f 12 (T, SOC, C) represents the mapping relationship between the power provided by the 12V battery pack and the real-time ambient temperature T, the battery charge SOC and the discharge rate C. 12 Indicates the real-time voltage of the monitored 12V battery pack, f 36 (T, SOC, C) represents the mapping relationship between the power provided by the 36V battery pack and the real-time ambient temperature T, the battery charge SOC and the discharge rate C. 36 Indicates the real-time voltage of the 36V battery pack monitored, η gear Indicates the gear transmission efficiency.

6. The control method according to claim 1, characterized in that: The vehicle start mode includes a 48V drive mode. In the 48V drive mode, the vehicle controller controls the first switch K1 and the fourth switch K4 to be closed, the second switch K2 and the third switch K3 to be disconnected, and the bidirectional DC / DC converter does not work, so that the 48V battery pack formed in series supplies power to the BSG motor. The BSG motor starts the engine.

7. The control method according to claim 1, characterized in that: The vehicle starting mode includes a 12V driving mode. In the 12V driving mode, the vehicle controller controls the first switch K1 and the fourth switch K4 to be disconnected, the second switch K2 and the third switch K3 to be closed, and the bidirectional DC / DC converter does not work, so that the 12V battery pack alone powers the ISG motor, and the ISG motor starts the engine.

8. The control method according to claim 1, characterized in that: The vehicle starting mode includes a 12V and 36V collaborative driving mode. In this driving mode, the vehicle controller controls the first switch K1 and the fourth switch K4 to be disconnected and the second switch K2 and the third switch K3 to be closed through the battery management unit, so that the 12V battery pack powers the ISG motor, and the 36V battery pack converts the voltage into 12V through the bidirectional DC / DC converter to power the ISG motor, and the ISG motor starts the engine.

9. A vehicle, characterized in that: It implements the control method as described in any one of claims 1-8.

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