Cold start method, system and motor vehicle for a methanol range extender

Abstract

The present application relates to a methanol range extender cold start method, system and motor vehicle, according to the current temperature of methanol, control control generator enters or exits the state of '' locked rotor heating '', the heat generated is respectively transmitted to the engine and methanol heater through the cooling liquid circulation loop, and methanol in the engine cooling liquid and methanol heater is heated respectively;Methanol is heated to the set temperature range, and the '' locked rotor heating '' state is exited and the engine is reversed, if the generator speed and engine output torque all exceed the corresponding set value, it represents that lubrication is finished, and the engine is started by using starter / generator. Through the cooling liquid with temperature, methanol is heated through the methanol heater, and the engine is reversed by using the generator to rotate, the lubrication effect of cylinder oil is improved, and the starting success rate is improved.

Description

Technical Field

[0001] This invention relates to the field of engine control technology, specifically to a cold start method, system, and motor vehicle for a methanol range extender. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] A methanol range extender consists of a methanol engine and a generator. The methanol engine burns methanol to drive the generator and produce electricity. The electricity can directly drive the motor or charge the battery, indirectly extending the vehicle's range. It is a type of hybrid technology.

[0004] Cold start of a methanol range extender refers to the process of starting a methanol engine from a standstill in a low-temperature environment (usually below 0°C). Because the physical and chemical properties of methanol differ from those of traditional gasoline or diesel, preheating of components such as the cooling circuit of the methanol engine is necessary.

[0005] In the prior art, the cooling circuits of the engine and the generator can be independent or connected. Regardless of the method used, the heat generated by the stalled generator can be transferred through the coolant, thereby preheating the engine.

[0006] The heat requirements of methanol fuel differ from those of the methanol engine itself. Current technologies only consider heating the engine coolant, which, while enabling rapid engine warm-up and improving start-up speed, fails to account for the difference in heat requirements between methanol fuel and the methanol engine. This results in unsatisfactory cold-start performance, easily leading to start-up failures or excessive emissions. Some existing technologies employ additional heating devices (such as heaters) to address this issue, but this method incurs higher start-up costs.

[0007] Furthermore, existing technologies only preheat the engine coolant. As the coolant circulates, it gradually raises the temperature of the engine block. However, since the engine is not running at this time, the lubricating oil in the engine block is concentrated at the bottom of the housing, which is difficult to be covered by the coolant. This results in the lubricating oil heating up slowly. When the engine starts, the lubricating oil that has not been properly preheated is not easy to form good lubrication in the engine block, which can easily cause damage to the cylinder block. Summary of the Invention

[0008] To address the technical problems mentioned above, this invention provides a cold start method, system, and vehicle for a methanol range extender. The method utilizes the heat generated by a stalled generator as a heat source during cold start. During this period, based on the methanol temperature, coolant at a certain temperature is passed through a methanol heater to heat the methanol. Simultaneously, based on the current coolant temperature, the generator reverses the engine rotation to improve the lubrication effect of the engine oil in the cylinder. After lubrication, the engine is started using a starter motor / generator.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] The first aspect of the present invention provides a cold start method for a methanol range extender, comprising the following steps:

[0011] When the current temperature of methanol is obtained and it is lower than the first set value T1, the generator is controlled to enter the "stalled rotor heating" state. The heat generated is transferred to the engine and methanol heater through the coolant circulation loop, respectively, to heat the methanol in the engine coolant and the methanol heater.

[0012] During heating, the current temperature of the engine coolant in the coolant circulation loop is obtained. When it is lower than the second set value T2, the generator maintains the "stalled rotor heating" state to raise the temperature of the engine coolant.

[0013] When the current temperature of the engine coolant is between the second set value T2 and the third set value T3, the generator is controlled to reverse the engine rotation at a set speed n. During this period, the current of the generator is controlled to change the ratio of electrical energy to heat energy, so that the generator speed is not 0 and heating continues.

[0014] When both the generator speed and the engine output torque exceed the corresponding set values, lubrication ends, and a "start engine" command is sent to the starter motor / generator.

[0015] Furthermore, when the current temperature of methanol is not lower than the first set value T1, the process of cutting off the flow of coolant through the methanol heater is initiated.

[0016] Furthermore, the current temperature of the engine coolant is between the second set value T2 and the third set value T3, and remains there for a set time, controlling the generator to exit the "stalled rotor heating" state.

[0017] Furthermore, when the current temperature of the engine coolant exceeds the third set value T3, the generator is controlled to exit the "stalled rotor heating" state.

[0018] A second aspect of the present invention provides a cold start system for a methanol range extender, including a coolant outlet pipe and a coolant inlet pipe, wherein the coolant outlet pipe is connected to a generator, an engine and a methanol heater respectively, and the coolant inlet pipe is connected to the generator, the engine and the methanol heater respectively.

[0019] Furthermore, corresponding control valves are installed between the coolant outlet pipe and the methanol heater, between the coolant outlet pipe and the engine, between the coolant inlet pipe and the methanol heater, and between the coolant inlet pipe and the engine.

[0020] Furthermore, by controlling the opening and closing of the control valve, the flow of coolant through the methanol heater and / or through the engine is controlled.

[0021] Furthermore, the methanol heater uses heated coolant as the working medium to transfer heat to the methanol through heat exchange.

[0022] A third aspect of the present invention provides a methanol range extender that performs the steps in the above-described methanol range extender cold start method.

[0023] A fourth aspect of the present invention provides a motor vehicle having a methanol range extender, the methanol range extender performing the steps in the above-described methanol range extender cold start method.

[0024] Compared with existing technologies, one or more of the above technical solutions have the following beneficial effects:

[0025] 1. Considering the difference between the heat requirements of methanol fuel and the engine itself, controlling the flow of coolant through the methanol heater allows for independent control of methanol heating and engine coolant heating, which helps improve the start-up success rate of methanol engines and reduce start-up costs.

[0026] 2. During startup, when the engine coolant temperature reaches the set value, the generator is used to reverse-drive the engine to lubricate it. At this time, the engine is not injected with fuel and is not running. The crankshaft rotation allows the heat in the lubricating oil to be evenly distributed, thereby improving the lubrication effect and reducing the damage to the engine caused by insufficient lubrication during low-temperature startup. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0028] Figure 1 This is a schematic diagram of the cold start process of a methanol range extender provided in one or more embodiments of the present invention;

[0029] Figure 2 This is a schematic diagram of the cold start principle of a methanol range extender provided in one or more embodiments of the present invention;

[0030] Figure 3 This is a schematic diagram of the working process of a methanol range extender during cold start provided in one or more embodiments of the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] It should be noted that the following detailed description is exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0033] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the scope of exemplary embodiments of the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0034] In existing technologies (such as CN115263519B), the cooling circuits of the engine and generator can be independent or interconnected. Regardless of the method used, the heat generated by the stalled generator can be transferred through the coolant, thereby preheating the engine.

[0035] "The generator generates heat when stalled." Range extenders typically consist of an engine (internal combustion engine) and a generator (the engine drives the generator to produce electricity). When operating normally, the generator is driven by the engine to generate electricity. If it is forcibly stalled (the rotor stops rotating), it becomes a "purely resistive load," generating heat. The generator in a range extender is a more suitable heat source than the drive motor because it may still operate when the vehicle is stationary (e.g., for battery charging). Therefore, the heat generated by the stalled generator can be directly used to heat the adjacent coolant or methanol fuel. The drive motor also generates heat when stalled (e.g., when the vehicle is stationary but the motor is energized), but this heat is usually not used for heat recovery due to its low efficiency and potential for motor damage.

[0036] The heat requirements of methanol fuel differ from those of the methanol engine itself. For methanol fuel, due to the high latent heat of vaporization of methanol (1100kJ / kg, which is 3 times that of gasoline), it is difficult to evaporate at low temperatures, resulting in an overly lean air-fuel mixture and difficulty in ignition.

[0037] Secondly, methanol has a low flame propagation speed, and incomplete combustion when the engine is cold may cause flameout or worsening of emissions (such as increased formaldehyde emissions).

[0038] Secondly, methanol has a diluting effect on engine oil, which may affect engine lubrication during cold starts.

[0039] Existing technology CN115263519B provides a thermal management system for a hybrid engine, which connects the motor cooling circuit to the engine cooling circuit, using the heat generated by the motor's stall-rotor heating to heat the engine. However, it only considers heating the engine coolant. While this achieves rapid engine warm-up and improves start-up speed, it fails to consider the difference in heat requirements between methanol fuel and methanol engines, resulting in unsatisfactory cold-start performance and a tendency to cause start-up failures or excessive emissions. Some existing technologies employ additional heating devices (such as heaters) to address this issue, but this approach incurs higher start-up costs.

[0040] Furthermore, existing technologies only preheat the engine coolant. As the coolant circulates, it gradually raises the temperature of the engine block. However, since the engine is not running at this time, the lubricating oil (engine oil) in the engine cylinder block is concentrated at the bottom of the housing, which is difficult to be covered by the coolant circulation loop. This results in the lubricating oil heating up slowly. When the engine is started, the lubricating oil that has not been properly preheated is prone to causing damage to the cylinder block.

[0041] Therefore, the following embodiments provide a cold start method, system, and vehicle for a methanol range extender. The coolant circulation loops of the methanol engine and generator are connected to the methanol heater. The heat generated by the generator during stall is used as the heat source during cold start. During this period, based on the temperature of the methanol, a control valve is used to allow coolant at a certain temperature to pass through the methanol heater to heat the fuel methanol. At the same time, based on the current temperature of the coolant, the generator is used to reverse the rotation of the engine to improve the lubrication effect of the engine oil in the cylinder. After a period of time, the engine is started using a starter motor / generator.

[0042] The engines mentioned in the following examples are all engines in methanol range extenders. They can be engines that use methanol as fuel, or engines that use multiple media such as gasoline, diesel and methanol as fuel.

[0043] In the following examples, "motor" and "generator" refer to the generator in the methanol range extender. The generator is preferably directly connected to the engine (such as the P1 hybrid architecture) to ensure sufficient torque to slowly drive the engine crankshaft, help the oil pump build up oil pressure, and lubricate the cylinder walls.

[0044] In a methanol range extender, the engine and generator are directly connected mechanically (usually located on the same shaft or fixedly connected by gears), and 100% of the mechanical energy generated by the engine burning methanol is used to drive the generator (no mechanical transmission to the wheels).

[0045] In this architecture, the engine's sole function is to drive the generator to produce electricity; it does not directly participate in vehicle propulsion (unlike the P1 hybrid where the engine can drive the wheels).

[0046] In this architecture, the generator is driven by the methanol engine, which converts mechanical energy into electrical energy and outputs high-voltage AC power. After rectification, the AC power is preferentially supplied to the drive motor (to reduce battery charging and discharging losses), and excess electrical energy is stored in the power battery.

[0047] Example 1:

[0048] The "stalled-rotor heating" state given in this embodiment refers to the use of a power battery or storage battery to supply power to the generator, and the generator is maintained at a speed of 0 through mechanical devices or control circuits. In this state, all the electrical energy received by the generator is converted into heat energy.

[0049] In this embodiment, the state of the generator driving the engine refers to the generator speed not being 0. By controlling the generator current, in order to increase the generator loss, some electrical energy is converted into heat energy. That is, by changing the ratio of generator electrical energy to heat energy, the generator is kept in a state that can both drive the engine to rotate and generate heat.

[0050] like Figure 1 As shown, the cold start method for a methanol range extender includes the following steps:

[0051] The current temperature of methanol is obtained. When it is lower than the first set value T1, heat is generated by the generator stalling. The heat is transferred to the engine and methanol heater through the coolant circulation loop, respectively, to heat the methanol in the engine coolant and methanol heater. When the current temperature of methanol exceeds T1, the process of coolant flowing through the methanol heater is cut off.

[0052] During heating, the current temperature of the engine coolant in the coolant circulation loop is obtained. If it is lower than the second set value T2, the generator continues to stall and heat the engine coolant.

[0053] When the current temperature of the engine coolant is between the second set value T2 and the third set value T3, the generator reverse-drives the engine at a set speed n to improve the lubrication of the engine oil. During the reverse-drive, the generator current is controlled to increase the motor loss, that is, to increase the proportion of electrical energy converted into heat energy, so that the generator can maintain a non-zero speed and continue to heat.

[0054] If the current engine coolant temperature remains between T2 and T3 for a set period of time, or exceeds T3, the generator heating will end.

[0055] When the generator speed and engine output torque exceed the set values, lubrication ends. The engine is then started using a starter motor / generator according to the driver's needs, and the cold start is successful.

[0056] In this embodiment, the generator is an integrated motor that can be driven by the engine to generate electrical energy. It is also connected to the power battery to receive electrical energy from the power battery, generate heat through stalling, or drive the engine in the reverse direction.

[0057] like Figure 2 As shown in the control principle, in this embodiment, the generator and engine share a coolant circulation loop, and the methanol heater is also connected to the coolant circulation loop.

[0058] As a further embodiment, the coolant circulation loop includes a coolant outlet pipe and a coolant inlet pipe. The coolant outlet pipe is connected to the generator, the engine, and the methanol heater, respectively, and the coolant inlet pipe is connected to the generator, the engine, and the methanol heater, respectively.

[0059] As a further embodiment, valve 1 is provided at the connection point between the coolant outlet pipe and the methanol heater, valve 2 is provided at the connection point between the coolant outlet pipe and the engine, valve 3 is provided at the connection point between the coolant inlet pipe and the methanol heater, and valve 4 is provided at the connection point between the coolant inlet pipe and the engine.

[0060] As a further implementation, the generator is stalled, and the heat generated is carried away by the circulating coolant. When valves 4 and 2 are open, the coolant carrying heat heats the engine, and when valves 1 and 3 are open, the coolant carrying heat heats the methanol in the methanol heater.

[0061] As a further embodiment, the methanol heater uses coolant as the working medium to heat the methanol fed into it, and the heated methanol is then sent into the engine.

[0062] As a further implementation, the specific structure of the methanol heater is not limited. For example, it can be based on the principle of a heat exchanger, which heats the methanol by exchanging heat from the coolant to the methanol.

[0063] As a further implementation method, the heat generated by the generator stall can be generated by mechanical stall or electrical stall, and there are no restrictions on the specific type, as long as the generator safety is ensured.

[0064] As a further implementation, mechanical stall can be achieved by fixing the generator rotor with a mechanical device (such as an electromagnetic brake or ratchet) so that it cannot rotate.

[0065] As a further implementation, an electrical stall mechanism can be implemented by short-circuiting the generator output terminal using a controller, preventing the rotor from rotating due to electromagnetic resistance (similar to "dynamic braking" of an electric motor).

[0066] As a further implementation method, the energy flow during the heating process by the generator through stalling is as follows: the power battery supplies power to the generator → the generator stalls → all electrical energy is converted into heat energy → the coolant / methanol is heated through the heat exchanger.

[0067] During heating, the engine cannot be driven due to the low temperature. Heat is generated by injecting current and controlling the generator to stall (target speed is 0), during which time the generator does not output kinetic energy.

[0068] As a further implementation method, the core of stall-rotor heating is to generate more heat energy from electrical energy, thereby increasing the copper and iron losses of the generator to obtain heat. This method can generate tens of kilowatts of thermal power in a short time (such as 50kW+ motor of a range extender), which is far higher than ordinary PTC (usually 5-10kW) heating method. It can quickly heat up in extremely cold environments and shorten the cold start time.

[0069] Stall-rotor heating is suitable for temperatures between -40°C and -20°C, and can be extended to -50°C in extremely cold environments, but the performance of materials at -50°C needs to be considered. For example, the discharge capacity of lithium batteries drops sharply below -40°C, insulating materials (such as enameled wire) may become brittle below -50°C, the high current during stall can easily lead to insulation breakage, and permanent magnets (such as neodymium iron boron) are at risk of demagnetization at extremely low temperatures, requiring the use of low-temperature resistant magnets (such as samarium cobalt).

[0070] Whether it's a mechanical stall or an electrical stall, both generate heat by forcing the generator to operate at zero speed.

[0071] During stall heating, the excitation current and load are adjusted by a control algorithm to make the generator output the maximum current but the speed is zero. The specific control algorithm can be a mature existing technology, and the specific details are not described in this embodiment.

[0072] like Figure 3 As shown, the cold start process of the methanol range extender includes the following steps:

[0073] 1) Determine the current temperature of methanol. If the temperature is lower than T1, the generator will stall and generate heat to raise the methanol temperature. Once the temperature meets the threshold, close valves 1 and 3 to prevent the methanol temperature from becoming too high.

[0074] 2) Determine the current engine coolant temperature. If the temperature is lower than T2, the generator stalls and generates heat to quickly raise the engine coolant temperature. When the engine coolant temperature is higher than T2 but lower than T3, the generator drives the engine at speed n, causing the engine oil to lubricate the engine block. At the same time, the generator current is controlled to continue generating heat and raising the engine coolant temperature. When the engine coolant temperature is higher than T2 but lower than T3 for a set time, or higher than T3, the generator stops heating. The lubrication is determined based on the generator speed and torque.

[0075] 3) After lubrication, start the engine using a starter motor / generator as needed by the driver.

[0076] As a further implementation method, the target speed n needs to be determined based on the engine coolant temperature and engine oil temperature, which can be determined by bench testing or simulation.

[0077] As a further implementation, the three temperature setpoints T1, T2, and T3 can be determined through bench testing or simulation.

[0078] For example, T1 is the critical temperature at which methanol can be easily ignited; T2 is the engine's thermal threshold temperature, below which misfire or knocking is likely to occur during engine ignition. T3 is a temperature after T2, meaning T3 is higher than T2. ​​T3 is determined based on the operating temperature range of the engine oil to ensure adequate lubrication.

[0079] As a further implementation method, lubrication can be completed by measuring the generator speed and engine output torque. When the generator speed and engine output torque exceed the set values, lubrication is considered to be completed and the engine can be started.

[0080] During startup, the generator actively drives the engine. The generator has four working quadrants, one of which can be used for reverse starting.

[0081] The four quadrants of a generator are used to describe the torque-speed relationship of the motor under different operating conditions, covering two modes: electric (drive) and generator (braking), as well as two directions of rotation: forward and reverse.

[0082] Specifically:

[0083] (1) Quadrant 1: Forward electric mode (drive): speed > 0, torque > 0, generator draws power from battery and outputs mechanical energy, reverse start.

[0084] (2) Quadrant 2: Forward power generation mode (braking / energy recovery): speed > 0, torque < 0, used for range extender power generation (engine drives motor to generate electricity).

[0085] (3) 3-quadrant: Reverse electric mode (reverse drive): speed < 0, torque < 0, used for generator to rotate in reverse.

[0086] (4) Quadrant 4: Reverse generation mode (reverse braking): speed < 0, torque > 0.

[0087] In this solution, considering the stringent requirements of methanol engines for fuel temperature, and the fact that the temperature requirements of methanol differ from those of engine oil, independent control of methanol heating and engine coolant heating is achieved through valve switching during the engine oil warming process, using engine coolant as the heat transfer medium. This improves the success rate of methanol engine start-up.

[0088] During startup, when the engine coolant temperature reaches a certain threshold, the drive battery powers the generator, which in turn lubricates the engine, reducing damage caused by insufficient lubrication during low-temperature startup.

[0089] Using a stalled rotor method allows for the reuse of existing hardware, directly utilizing the generator in the range extender as a heater, eliminating the need for an additional PTC module, reducing system complexity, saving costs, and reducing weight.

[0090] On the other hand, the heat generation process of a stalled generator has a relatively high power density and generates heat faster instantaneously. When the generator is designed with stalled thermal management in mind (such as strengthening the cooling of the windings), it can be more efficient than an independent PTC. However, considering that this method will cause additional losses to the generator, it is suitable for extreme emergency scenarios, such as rapid heating in extremely cold environments.

[0091] Example 2:

[0092] The methanol range extender cold start system includes a coolant outlet pipe and a coolant inlet pipe. The coolant outlet pipe is connected to the generator, engine and methanol heater respectively, and the coolant inlet pipe is connected to the generator, engine and methanol heater respectively.

[0093] As a further implementation, corresponding control valves are provided between the coolant outlet pipe and the methanol heater, between the coolant outlet pipe and the engine, between the coolant inlet pipe and the methanol heater, and between the coolant inlet pipe and the engine.

[0094] As a further implementation, the flow of coolant through the methanol heater and / or through the engine is controlled by opening and closing the control valve.

[0095] As a further embodiment, the methanol heater uses heated coolant as the working medium and transfers heat to methanol through heat exchange.

[0096] The coolant circulation loops of the methanol engine and generator are connected to the methanol heater. The heat generated by the generator during stall is used as the heat source during cold start. During this period, the coolant with a certain temperature is passed through the methanol heater by the control valve according to the temperature of the methanol to heat the fuel methanol. At the same time, according to the current temperature of the coolant, the generator is used to drive the engine to rotate in the reverse direction to improve the lubrication effect of the oil in the cylinder. After a period of time, the engine is started by the starter motor / generator.

[0097] Considering the difference between the heat requirements of methanol fuel and the engine itself, controlling the flow of coolant through the methanol heater allows for independent control of methanol heating and engine coolant heating, which helps improve the start-up success rate of methanol engines and reduce start-up costs.

[0098] During startup, when the engine coolant temperature reaches the set value, the generator is used to back-drive the engine for lubrication. At this time, the engine is not injected with fuel and is not running. The crankshaft rotation allows the heat in the lubricating oil to be evenly distributed, thereby improving the lubrication effect and reducing the damage to the engine caused by insufficient lubrication during cold starts.

[0099] Example 3:

[0100] A methanol range extender, performing the steps in the above-mentioned methanol range extender cold start method, specifically:

[0101] When the current temperature of methanol is obtained and it is lower than the first set value T1, the generator is controlled to enter the "stalled rotor heating" state. The heat generated is transferred to the engine and methanol heater through the coolant circulation loop, respectively, to heat the methanol in the engine coolant and the methanol heater.

[0102] During heating, the current temperature of the engine coolant in the coolant circulation loop is obtained. When it is lower than the second set value T2, the generator maintains the "stalled rotor heating" state to raise the temperature of the engine coolant.

[0103] When the current temperature of the engine coolant is between the second set value T2 and the third set value T3, the generator is controlled to reverse the engine rotation at a set speed n. During this period, the current of the generator is controlled to change the ratio of electrical energy to heat energy, so that the generator speed is not 0 and heating continues.

[0104] When both the generator speed and the engine output torque exceed the corresponding set values, lubrication ends, and a "start engine" command is sent to the starter motor / generator.

[0105] As a further implementation, when the current temperature of methanol exceeds T1, the process of cutting off the flow of coolant through the methanol heater is carried out.

[0106] As a further implementation, the generator heating ends when the current temperature of the engine coolant is at T2 to T3 for a set time.

[0107] As a further implementation, generator heating ends when the current temperature of the engine coolant exceeds T3.

[0108] The coolant circulation loops of the methanol engine and generator are connected to the methanol heater. The heat generated by the generator during stall is used as the heat source during cold start. During this period, the coolant with a certain temperature is passed through the methanol heater by the control valve according to the temperature of the methanol to heat the fuel methanol. At the same time, according to the current temperature of the coolant, the generator is used to drive the engine to rotate in the reverse direction to improve the lubrication effect of the oil in the cylinder. After a period of time, the engine is started by the starter motor / generator.

[0109] Considering the difference between the heat requirements of methanol fuel and the engine itself, controlling the flow of coolant through the methanol heater allows for independent control of methanol heating and engine coolant heating, which helps improve the start-up success rate of methanol engines and reduce start-up costs.

[0110] During startup, when the engine coolant temperature reaches the set value, the generator is used to back-drive the engine for lubrication. At this time, the engine is not injected with fuel and is not running. The crankshaft rotation allows the heat in the lubricating oil to be evenly distributed, thereby improving the lubrication effect and reducing the damage to the engine caused by insufficient lubrication during cold starts.

[0111] Example 4:

[0112] A motor vehicle includes a methanol range extender, which performs the steps in the above-described methanol range extender cold start method, specifically:

[0113] When the current temperature of methanol is obtained and it is lower than the first set value T1, the generator is controlled to enter the "stalled rotor heating" state. The heat generated is transferred to the engine and methanol heater through the coolant circulation loop, respectively, to heat the methanol in the engine coolant and the methanol heater.

[0114] During heating, the current temperature of the engine coolant in the coolant circulation loop is obtained. When it is lower than the second set value T2, the generator maintains the "stalled rotor heating" state to raise the temperature of the engine coolant.

[0115] When the current temperature of the engine coolant is between the second set value T2 and the third set value T3, the generator is controlled to reverse the engine rotation at a set speed n. During this period, the current of the generator is controlled to change the ratio of electrical energy to heat energy, so that the generator speed is not 0 and heating continues.

[0116] When both the generator speed and the engine output torque exceed the corresponding set values, lubrication ends, and a "start engine" command is sent to the starter motor / generator.

[0117] As a further implementation, when the current temperature of methanol exceeds a first set value T1, the process of cutting off the flow of coolant through the methanol heater is carried out.

[0118] As a further implementation, the current temperature of the engine coolant is between the second set value T2 and the third set value T3 and remains there for a set time, at which point the generator heating ends.

[0119] As a further implementation, the generator heating ends when the current temperature of the engine coolant exceeds the third set value T3.

[0120] The coolant circulation loops of the methanol engine and generator are connected to the methanol heater. The heat generated by the generator during stall is used as the heat source during cold start. During this period, the coolant with a certain temperature is passed through the methanol heater by the control valve according to the temperature of the methanol to heat the fuel methanol. At the same time, according to the current temperature of the coolant, the generator is used to drive the engine to rotate in the reverse direction to improve the lubrication effect of the oil in the cylinder. After a period of time, the engine is started by the starter motor / generator.

[0121] Considering the difference between the heat requirements of methanol fuel and the engine itself, controlling the flow of coolant through the methanol heater allows for independent control of methanol heating and engine coolant heating, which helps improve the start-up success rate of methanol engines and reduce start-up costs.

[0122] During startup, when the engine coolant temperature reaches the set value, the generator is used to back-drive the engine for lubrication. At this time, the engine is not injected with fuel and is not running. The crankshaft rotation allows the heat in the lubricating oil to be evenly distributed, thereby improving the lubrication effect and reducing the damage to the engine caused by insufficient lubrication during cold starts.

[0123] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A cold start method for a methanol range extender, characterized in that, Includes the following steps: When the current temperature of methanol is obtained and it is lower than the first set value T1, the generator is controlled to enter the "stalled rotor heating" state. The heat generated is transferred to the engine and methanol heater through the coolant circulation loop, respectively, to heat the methanol in the engine coolant and the methanol heater. During heating, the current temperature of the engine coolant in the coolant circulation loop is obtained. When it is lower than the second set value T2, the generator maintains the "stalled rotor heating" state to raise the temperature of the engine coolant. When the current temperature of the engine coolant is between the second set value T2 and the third set value T3, the generator is controlled to reverse the engine rotation at a set speed n. When both the generator speed and the engine output torque exceed the corresponding set values, lubrication ends, and a "start engine" command is sent to the starter motor / generator.

2. The cold start method for a methanol range extender as described in claim 1, characterized in that, The process of cutting off the flow of coolant through the methanol heater when the current temperature of methanol is not lower than the first set value T1.

3. The cold start method for a methanol range extender as described in claim 1, characterized in that, The engine coolant temperature is between the second set value T2 and the third set value T3, and remains between these values ​​for a set time, controlling the generator to exit the "stalled rotor heating" state.

4. The cold start method for a methanol range extender as described in claim 1, characterized in that, When the current temperature of the engine coolant exceeds the third set value T3, the generator is controlled to exit the "stalled rotor heating" state.

5. A methanol range extender cold start system, used to implement the methanol range extender cold start method according to any one of claims 1-4, characterized in that, It includes a coolant outlet pipe and a coolant inlet pipe. The coolant outlet pipe is connected to the generator, engine and methanol heater respectively, and the coolant inlet pipe is connected to the generator, engine and methanol heater respectively.

6. The methanol range extender cold start system as described in claim 5, characterized in that, Each of the following is equipped with a corresponding control valve: between the coolant outlet pipe and the methanol heater, between the coolant outlet pipe and the engine, between the coolant inlet pipe and the methanol heater, and between the coolant inlet pipe and the engine.

7. The methanol range extender cold start system as described in claim 5, characterized in that, By controlling the opening and closing of the control valve, the flow of coolant through the methanol heater and / or through the engine is controlled.

8. The methanol range extender cold start system as described in claim 5, characterized in that, The methanol heater uses heated coolant as the working medium and transfers heat to methanol through heat exchange.

9. A methanol range extender, characterized in that, Perform the steps in the methanol range extender cold start method as described in any one of claims 1-4.

10. A motor vehicle, characterized in that, It has a methanol range extender that performs the steps in the methanol range extender cold start method as described in any one of claims 1-4.

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