Methanol range extender cold starting method and system and motor vehicle

Abstract

The invention relates to a methanol range extender cold start method and system and a motor vehicle, a generator is controlled to enter or exit a locked-rotor heating state according to the current temperature of methanol, and generated heat is respectively transmitted to an engine and a methanol heater through a cooling liquid circulation loop to respectively heat engine cooling liquid and methanol in the methanol heater; and when the methanol is heated to a set temperature range, quitting a locked-rotor heating state and reversely dragging the engine, and if the rotating speed of the generator and the output torque of the engine exceed corresponding set values, representing that lubrication is finished, and starting the engine by utilizing a starter / generator. The cooling liquid with temperature heats methanol through the methanol heater, and meanwhile, the engine is reversely dragged to rotate by utilizing the generator, so that the lubricating effect of engine oil in a cylinder is improved, and the starting success rate is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of engine control, and in particular to a cold start method and system for a methanol range extender and a motor vehicle. Background Art

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

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

[0004] A cold start of a methanol range extender is the process of starting a methanol engine from a standstill in a low-temperature environment (typically below 0°C). Because the physical and chemical properties of methanol differ from those of conventional gasoline or diesel, components such as the engine's cooling circuit must be preheated.

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

[0006] Methanol fuel requires different amounts of heat than a methanol engine. Existing technologies only consider heating the engine coolant. While this allows for rapid engine warm-up and improved startup speeds, it fails to account for the different heat requirements of methanol fuel and the methanol engine, resulting in suboptimal cold start performance, which can easily lead to start failures or excessive emissions. To address this issue, some existing technologies employ additional heating devices (such as air heaters), but this approach incurs high startup costs.

[0007] In addition, since the existing technology only preheats the engine coolant, the coolant can gradually increase the temperature of the engine body as it circulates. However, since the engine is not running at this time, the lubricating oil in the engine cylinder is concentrated at the bottom of the shell which is difficult to be covered by the coolant, resulting in slow heating of the lubricating oil. When the engine is started, the lubricating oil that has not been well preheated is not easy to form good lubrication in the engine cylinder, which can easily cause damage to the cylinder. Summary of the Invention

[0008] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a methanol range extender cold start method, system and motor vehicle, which utilize the heat generated by the generator stall as the heat source during the cold start period. During this period, according to the temperature of the methanol, the coolant with a certain temperature is passed through the methanol heater to heat the methanol. At the same time, according to the current temperature of the coolant, the generator is used to reversely drag the engine to rotate, thereby improving the lubrication effect of the engine oil in the cylinder. After the lubrication is completed, the starter / generator is used to start the engine.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

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

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

[0012] During the heating period, the current temperature of the engine coolant in the coolant circulation loop is obtained. When the current temperature is lower than the second set value T2, the generator maintains the "locked rotor heating" state to increase 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 reversely rotate the engine at the set speed n. During this period, the current of the generator is controlled to change the ratio of electrical energy to thermal energy, so that the generator speed is not zero and heating is continued;

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

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

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

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

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

[0019] Furthermore, 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.

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

[0021] Furthermore, the methanol heater uses the heated coolant as a working medium and transfers 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-mentioned 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 executing the steps of the above-mentioned methanol range extender cold start method.

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

[0025] 1. Considering the difference between the heat demand of methanol fuel and the engine body, by controlling the coolant flow through the methanol heater, the methanol heating and the engine body coolant heating can be controlled independently, which is beneficial to improve the success rate of methanol engine starting and reduce starting costs.

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

[0027] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

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

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

[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 descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0033] It should be noted that the terms used herein are intended only to describe specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0034] In the prior art (eg CN115263519B), the cooling circuits of the engine and the generator can be independent of each other or interconnected. Regardless of the method, the heat generated by the generator stalling can be transferred through the coolant, thereby preheating the engine.

[0035] "Generator stalling generates heat." The range extender usually consists of an engine (internal combustion engine) and a generator (the engine drives the generator to generate electricity). When the generator is working normally, it is driven by the engine to rotate and generate electricity. If it is forcibly stalled (the rotor stops rotating), it will become a "pure resistance load" and generate heat. The generator in the range extender is a more suitable heat source than the drive motor because it may still run when the vehicle is stationary (such as battery charging needs). Therefore, the heat generated by the stalled generator can be used directly to heat the adjacent coolant or methanol fuel. The drive motor will also generate heat when it is stalled (such as when the vehicle is stationary but the motor is powered), but it is usually not used for heat recovery because the efficiency is too low and it may damage the motor.

[0036] There is a difference between the heat demand of methanol fuel and the methanol engine itself. For methanol fuel, due to the high latent heat of vaporization of methanol (1100kJ / kg, three times that of gasoline), it is difficult to evaporate at low temperatures, resulting in the mixture being too lean and difficult to ignite.

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

[0038] Again, methanol has a diluting effect on engine oil and may affect engine lubrication when starting at low temperatures.

[0039] Prior art CN115263519B provides a hybrid engine thermal management system that connects the motor cooling circuit with the engine cooling circuit, using the heat generated by the motor's stalled-rotor heating to heat the engine. This system only considers heating the engine coolant. While this allows for rapid engine warm-up and improved startup speed, it fails to account for the different heat requirements of methanol fuel and methanol engines, resulting in suboptimal cold start performance, which can easily lead to startup failures or excessive emissions. To address this issue, some prior art technologies employ additional heating devices (such as heaters), but this approach carries high startup costs.

[0040] In addition, since the existing technology only preheats the engine coolant, the coolant can gradually increase the temperature of the engine body as it circulates. However, since the engine is not running at this time, the lubricating oil (engine oil) in the engine cylinder is concentrated at the bottom of the shell which is difficult to be covered by the coolant circulation loop, resulting in slow heating of the lubricating oil. When the engine is started, the lubricating oil that has not been well preheated can easily cause damage to the cylinder.

[0041] Therefore, the following embodiments provide a methanol range extender cold start method, system, and motor vehicle, in which the coolant circulation loops of the methanol engine and generator are connected to a methanol heater, and the heat generated by the generator stalling is used as a heat source during the cold start. During this period, according to the temperature of the methanol, a control valve is used to allow coolant with a certain temperature to pass through the methanol heater to heat the fuel methanol. At the same time, according to the current temperature of the coolant, the generator is used to reversely drag the engine to rotate, thereby improving the lubrication effect of the engine oil in the cylinder. After a period of time, the starter / generator is used to start the engine.

[0042] The engines appearing in the following embodiments are all engines in a methanol range extender, and may be engines using methanol as fuel, or engines using gasoline, diesel, methanol and other media as fuel.

[0043] The "motor" and "generator" appearing in the following embodiments are all generators in the methanol range extender, and it is preferred to directly connect the generator 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 wall.

[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 (without mechanical transmission to the wheels).

[0045] Under this architecture, the engine's only function is to drive the generator to generate electricity and does not directly participate in vehicle propulsion (unlike the P1 hybrid where the engine can drive the wheels).

[0046] Under this architecture, the generator is driven by the methanol engine, converting mechanical energy into electrical energy and outputting it as high-voltage AC power. After rectification, it is supplied to the drive motor first (reducing battery charging and discharging losses), and the excess electrical energy is stored in the power battery.

[0047] Example 1:

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

[0049] In this embodiment, the state in which the generator reversely drags the engine means that the speed of the generator is not 0. By controlling the current of the generator, part of the electrical energy is converted into heat energy in a manner that increases the loss of the generator. That is, by changing the ratio of the generator's electrical energy converted into heat energy, the generator is maintained in a state where it can both drag the engine to rotate and generate heat at the same time.

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

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

[0052] During the heating period, the current temperature of the engine coolant in the coolant circulation loop is obtained. When the current temperature is lower than the second set value T2, the generator continues to perform stall heating to increase the temperature of 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 reverses the engine rotation at the set speed n to improve the oil lubrication condition in the engine. During the reverse rotation, the generator current is controlled to increase the loss of the motor, that is, to increase the ratio of electrical energy converted into thermal energy, so that the generator maintains a non-zero speed and can still continue heating.

[0054] When the current temperature of the engine coolant is between T2 and T3 for the set time, or exceeds T3, the generator heating ends;

[0055] When the generator speed and engine output torque exceed the set values, lubrication ends and the starter / generator is used to start the engine according to the driver's demand, and the cold start is successful.

[0056] The generator in this embodiment is an all-in-one motor that can be driven by the engine to generate electricity. It is also connected to the power battery to receive electricity from the power battery, generate heat by stalling, or drag the engine in reverse.

[0057] like Figure 2 As shown in the control principle, in this embodiment, the generator and the 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 respectively connected to the generator, engine and methanol heater, and the coolant inlet pipe is respectively connected to the generator, engine and methanol heater.

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

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

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

[0062] As a further embodiment, the specific structural type of the methanol heater is not limited. For example, it can be based on the principle of a heat exchanger, and the heating of the methanol is achieved by exchanging heat in the coolant into the methanol.

[0063] As a further implementation method, the heat generated by the generator stalling can be generated by mechanical stalling or electrical stalling. The specific type is not limited as long as the safety of the generator is ensured.

[0064] As a further implementation, mechanical stalling can fix the generator rotor by a mechanical device (such as an electromagnetic brake, a ratchet) so that it cannot rotate.

[0065] As a further implementation method, electrical stalling can be achieved by short-circuiting the generator output terminal through the controller, so that the rotor cannot rotate due to electromagnetic resistance (similar to the "dynamic braking" of the motor).

[0066] As a further embodiment, the energy flow during the heating period of the generator through stalling is: the power battery supplies power to the generator → the generator stalls → all electrical energy is converted into thermal energy → the coolant / methanol is heated through the heat exchanger.

[0067] During the heating period, the engine is not allowed to be driven due to the low temperature. Heat is generated by injecting current and controlling the generator to be locked (target speed is 0). During this period, the generator does not output kinetic energy.

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

[0069] Locked-rotor heating is suitable for temperatures between -40°C and -20°C, and can be extended to -50°C for extremely cold environments. However, material performance at -50°C must 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, and high current during locked-rotor heating can easily cause insulation cracking. Permanent magnets (such as neodymium iron boron) are at risk of demagnetization at extremely low temperatures, necessitating the use of low-temperature-resistant magnetic steel (such as samarium cobalt).

[0070] Whether it is mechanical stall or electrical stall, heating is achieved by forcing the generator to operate in zero speed mode.

[0071] During the locked-rotor heating period, the excitation current and load are adjusted by a control algorithm so that the generator outputs maximum current but the speed is zero. The specific control algorithm can be a mature existing technology, and the specific details are not repeated in this embodiment.

[0072] like Figure 3 As shown in the figure, 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 is blocked to generate heat and increase the methanol temperature. When the temperature reaches the threshold, valves 1 and 3 are closed to prevent the methanol temperature from being too high.

[0074] 2) Determine the current engine coolant temperature. If the temperature is below T2, the generator stalls and generates heat, rapidly raising the engine coolant temperature. When the engine coolant temperature is above T2 and below T3, the generator rotates the engine at a speed n, allowing the engine oil to lubricate the engine cylinder. At the same time, the generator current is controlled to continue generating heat, raising the engine coolant temperature. When the engine coolant temperature is above T2 and below T3 for a set time, or is above T3 for a set time, the generator stops heating, and lubrication is determined to be complete based on the generator speed and torque.

[0075] 3) After lubrication, use the starter / generator to start the engine according to the driver's needs.

[0076] As a further implementation manner, the target speed n needs to be determined based on the engine coolant temperature and the engine oil temperature, and can be determined based on bench tests or simulations.

[0077] As a further embodiment, the three temperature setting values ​​T1 , T2 and T3 may be determined through bench testing or simulation.

[0078] For example, T1 is the critical temperature at which methanol readily ignites; T2 is the engine warm-up threshold, below which engine ignition is prone to misfire or knock. T3 is a temperature after T2, meaning that T3 is higher than T2. ​​T3 is determined based on the oil's operating temperature range to ensure adequate lubrication.

[0079] As a further embodiment, the end of lubrication can be judged by the generator speed and the engine output torque. When the generator speed and the engine output torque exceed the set value, it is considered that lubrication is completed and can be started.

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

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

[0082] Specifically:

[0083] (1) Quadrant 1: Forward electric mode (drive): Speed ​​> 0, torque > 0, the generator draws power from the battery, outputs mechanical energy, and starts in reverse.

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

[0085] (3) 3rd quadrant: reverse electric mode (reverse drive): speed < 0, torque < 0, used for reverse rotation of the generator.

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

[0087] This solution takes into account the strict fuel temperature requirements of methanol engines, as well as the different temperature requirements of methanol and engine oil. Using engine coolant as the heat transfer medium, this approach achieves independent control of methanol heating and engine coolant heating during oil heating by switching valves, which helps improve the success rate of methanol engine starts.

[0088] During startup, when the engine coolant temperature reaches a certain threshold, the drive battery is used to power the generator, which then reverses the engine to lubricate it, reducing damage to the engine caused by insufficient lubrication during low-temperature startup.

[0089] On the one hand, the use of the blocked rotor method can reuse existing hardware and directly use the generator in the range extender as a heater without 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-rotor generator has a relatively high power density and faster instantaneous heat generation. If the generator is designed with stalled-rotor heat management in mind (such as strengthening winding heat dissipation), it can be more efficient than an independent PTC. However, considering that this method will cause additional losses to the generator, it is only 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, the engine and the methanol heater respectively, and the coolant inlet pipe is connected to the generator, the engine and the methanol heater respectively.

[0093] As a further embodiment, 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 embodiment, the coolant is controlled to flow through the methanol heater and / or the engine by opening and closing a control valve.

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

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

[0097] Taking into account the difference between the heat demand of methanol fuel and the engine body, by controlling the coolant flow through the methanol heater, the methanol heating and the engine body coolant heating can be controlled independently, which is beneficial to improve the success rate of methanol engine starting and reduce starting costs.

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

[0099] Example 3:

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

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

[0102] During the heating period, the current temperature of the engine coolant in the coolant circulation loop is obtained. When the current temperature is lower than the second set value T2, the generator maintains the "locked rotor heating" state to increase 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 reversely rotate the engine at the set speed n. During this period, the current of the generator is controlled to change the ratio of electrical energy to thermal energy, so that the generator speed is not zero and heating is continued;

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

[0105] As a further embodiment, when the current temperature of methanol exceeds T1, the flow of coolant through the methanol heater is cut off.

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

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

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

[0109] Taking into account the difference between the heat demand of methanol fuel and the engine body, by controlling the coolant flow through the methanol heater, the methanol heating and the engine body coolant heating can be controlled independently, which is beneficial to improve the success rate of methanol engine starting and reduce starting costs.

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

[0111] Example 4:

[0112] A motor vehicle having a methanol range extender, wherein the methanol range extender performs the steps of the above-mentioned methanol range extender cold start method, specifically:

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

[0114] During the heating period, the current temperature of the engine coolant in the coolant circulation loop is obtained. When the current temperature is lower than the second set value T2, the generator maintains the "locked rotor heating" state to increase 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 reversely rotate the engine at the set speed n. During this period, the current of the generator is controlled to change the ratio of electrical energy to thermal energy, so that the generator speed is not zero and heating is continued;

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

[0117] As a further embodiment, when the current temperature of methanol exceeds a first set value T1, the process of the coolant flowing through the methanol heater is cut off.

[0118] As a further embodiment, the current temperature of the engine coolant is between the second set value T2 and the third set value T3 and lasts for a set time, and the generator heating is completed.

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

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

[0121] Taking into account the difference between the heat demand of methanol fuel and the engine body, by controlling the coolant flow through the methanol heater, the methanol heating and the engine body coolant heating can be controlled independently, which is beneficial to improve the success rate of methanol engine starting and reduce starting costs.

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

[0123] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

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

2. The cold start method of the methanol range extender according to claim 1, characterized in that: When the current temperature of methanol is not lower than the first set value T1, the process of cutting off the coolant flowing through the methanol heater.

3. The cold start method of a methanol range extender according to claim 1, characterized in that: The current temperature of the engine coolant is between the second set value T2 and the third set value T3 and lasts for the set time, controlling the generator to exit the "locked rotor heating" state.

4. The cold start method of a methanol range extender according to claim 1, wherein: When the current temperature of the engine coolant exceeds the third set value T3, the generator is controlled to exit the "locked 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 to 4, characterized in that: It 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. The coolant inlet pipe is connected to the generator, the engine and the methanol heater respectively.

6. The methanol range extender cold start system according to claim 5, characterized in that: 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.

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

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

9. A methanol range extender, characterized in that: Execute 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: A methanol range extender is provided, and the methanol range extender performs the steps in the methanol range extender cold start method as described in any one of claims 1 to 4.

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