CN106285917A - A kind of diesel engine starting aid system being applicable to high altitude localities and method - Google Patents

Abstract

The invention relates to an auxiliary system and method for starting a diesel engine suitable for high-altitude areas. The system includes an auxiliary booster intake pipe, a fluid machine with a low pressure ratio and a large flow rate, an atmospheric pressure sensor, a coolant temperature sensor and a control unit. The gas diverter valve is respectively connected to the intake end of the turbocharger intake pipe and the intake end of the auxiliary booster intake pipe, and the intake end of the intercooler is respectively connected to the outlet end of the turbocharger intake pipe and the auxiliary booster through the gas confluence valve. At the outlet end of the intake pipe, the low-pressure ratio and high-flow fluid machinery is installed in the auxiliary booster intake pipe, the outlet end of the intercooler is connected to the intake end of the engine, the atmospheric pressure sensor is installed on the air inlet, and the coolant temperature sensor is installed on the sending port. inside the plane. Compared with the prior art, the invention can improve the success rate of starting the engine at high altitude, shorten the start-up time of the diesel engine with low compression ratio, and make the diesel engine enter the stable idling state faster.

Description

A Diesel Engine Starting Assist System and Method Applicable to High Altitude Areas

technical field

The invention relates to the technical field of diesel engines, in particular to a starting auxiliary system and method for diesel engines suitable for high-altitude areas.

Background technique

Low compression ratio diesel engine is an important development trend in the field of diesel engines at present, mainly due to the stricter emission regulations at home and abroad, the diesel engine nitrogen oxide emission and particulate matter emission control technology has been vigorously developed, and the explosion pressure in the cylinder of the diesel engine after reducing the compression ratio The temperature and temperature have dropped, which can greatly reduce the emissions of nitrogen oxides and particulate matter from diesel engines. Another benefit of reducing the compression ratio of the diesel engine is that the mechanical load and heat load of the diesel engine are significantly reduced, which provides the necessary conditions for the diesel engine to be lightweight and high-speed. At the same time, some high power density diesel engines generally adopt high boost technology to increase power density, and also require low compression ratio to reduce mechanical load and thermal load.

However, one of the main problems of low compression ratio diesel engines is that it is difficult to start a cold engine. The main reason is that the turbocharger does not work when the diesel engine starts, and the charging efficiency is low. After the compression ratio is reduced, the temperature and pressure of the intake air in the diesel engine cylinder will decrease Obviously lower than the high compression ratio diesel engine, resulting in poor fuel atomization, and the temperature and pressure are difficult to reach the ignition conditions. This problem is more serious in the plateau environment, because the plateau atmospheric pressure is low, which reduces the quality of the intake air when the diesel engine starts, and the temperature and pressure of the gas in the cylinder drop further when the compression ends, making it more difficult to start.

At present, two technical routes are generally used to improve the starting of diesel engines in plateau cold engines, one is to heat the intake air, cooling water or engine oil, and the other is to use compressed air to start or supplement the engine intake air during start-up. gas. The first technical route needs to wait for a long time to start because it needs to heat the air, coolant or engine oil, which affects work efficiency. At the same time, the energy consumption required for heating is very large. If electric heating is used, the power supply must be taken into account. Use question. The second method does not require heating, such as starting with compressed air. The high-pressure air in the air storage tank is directly passed into the cylinder during the power stroke of the diesel engine to push the piston to do work and increase the speed. This method is widely used in large diesel engines for ships, mainly because ships All are equipped with high-power air compressors, which can continuously replenish compressed air into the air storage tank; while starting air intake is to add air to the intake pipe during the starting and dragging of the diesel engine to increase the quality of intake air, thereby improving the mixing in the cylinder. Air quality, to achieve the purpose of shortening the starting time. At present, there are also two methods for starting the intake air supply, one is that the air storage tank supplies air to the engine intake, and the other is the intake air supply of the electric turbine engine. On vehicles and mobile machinery, the gas storage tank cannot be made larger, so a very high pressure is required to ensure sufficient gas storage capacity. At present, the gas storage tank is as high as 8MPa, which is dangerous, and the gas storage tank needs The air compressor with high power and high compression ratio can be used continuously, otherwise it needs to be replaced frequently, which will bring inconvenience to use. Electric turbines are currently used on gasoline engines, but they are rarely used on diesel engines. The main reason is that electric turbines need to be developed separately for the engine, and require complex control strategies. The cost is very high, and the stability is difficult to guarantee, so it is difficult to large-scale Scale application.

In order to make the diesel engine start conveniently and smoothly in the plateau environment, and at the same time minimize the modification of the diesel engine, it is necessary to improve the method of starting air supplement. How to make the low compression ratio diesel engine start quickly and smoothly in the plateau environment, minimize the modification of the diesel engine, and at the same time ensure high stability, is an urgent problem to be solved in the cold start of the low compression ratio diesel engine plateau.

Contents of the invention

The purpose of the present invention is to provide a diesel engine starting assist system and method suitable for high altitude areas in order to overcome the above-mentioned defects in the prior art, which can improve the success rate of engine starting at high altitudes and shorten the starting liter of low compression ratio diesel engines. The speed time is shortened, so that the diesel engine enters the stable idle state faster, and solves the problem that the current diesel engine is difficult to start on a plateau.

The purpose of the present invention can be achieved through the following technical solutions:

A diesel engine start assist system suitable for high altitude areas, used to assist the start of a diesel engine, the diesel engine includes an air intake, a turbocharged intake pipe, an intercooler and an engine, the system includes an auxiliary supercharged intake pipe, a low pressure Relatively large flow fluid machinery, atmospheric pressure sensor, coolant temperature sensor and control unit, the air inlet is respectively connected to the intake end of the turbocharged intake pipe and the intake end of the auxiliary supercharged intake pipe through the gas diverter valve, so The inlet end of the intercooler is respectively connected to the outlet end of the turbocharger inlet pipe and the outlet end of the auxiliary supercharger inlet pipe through the gas confluence valve. The air outlet end of the cooler is connected to the intake end of the engine, the atmospheric pressure sensor is arranged on the air inlet, the coolant temperature sensor is arranged in the engine, and the control unit is respectively connected to a low-pressure ratio large-flow fluid machine, a gas confluence valve, gas diverter valve, barometric pressure sensor, coolant temperature sensor and engine.

In the initial state, the gas diverter valve and the gas confluence valve open the air inlet to enter the first channel of the intercooler through the turbocharged intake pipe and close the air inlet to enter the second channel of the intercooler through the auxiliary supercharged intake pipe, and at the same time The low-pressure ratio and high-flow fluid machinery does not work. After the control unit receives the start signal of the engine, it receives the coolant temperature collected by the cooling water temperature sensor and the atmospheric pressure at the air inlet collected by the atmospheric pressure sensor. When it is judged that the current coolant temperature is lower than the current At the temperature setting value under atmospheric pressure, the control unit outputs auxiliary start commands to the gas diverter valve and gas confluence valve respectively, and at the same time outputs work commands to the low-pressure ratio and high-flow fluid machinery. At this time, the first channel is closed and the second channel is opened. Until the engine speed reaches the set speed, the gas diverter valve, the gas confluence valve and the low-pressure ratio high-flow fluid machinery reset back to the initial state.

The compression ratio of the low-pressure ratio and high-flow fluid machine ranges from 1.2 to 1.6.

The flow rate of the low-pressure ratio high-flow fluid machine is related to the engine displacement and idle speed, and satisfies the following formula:

Q＝0.036×P×V

In the formula, Q represents the flow rate, the unit is m ³ /h, P represents the engine displacement, the unit is L, V represents the idle speed, the unit is r/min.

The fluid machine with low pressure ratio and high flow rate adopts a centrifugal compressor, a vortex air pump or an axial flow compressor.

The fluid machine with low pressure ratio and high flow rate is powered by a storage battery.

The control unit stores an atmospheric pressure-coolant temperature MAP map containing the temperature setting values of the current diesel engine at different atmospheric pressures, and the atmospheric pressure and coolant temperature in the atmospheric pressure-coolant temperature MAP map satisfy the following formula :

T _c =0.083P _a ² -1.897P _a +349.841

In the formula, T _c represents the coolant temperature in K, and _Pa represents the atmospheric pressure in kPa.

The auxiliary pressurized intake pipe is provided with an automatic pressure relief valve, and the automatic pressure relief valve is opened when the pressure in the auxiliary pressurized intake pipe is greater than the maximum working pressure of the fluid machine.

An air filter is provided at the air inlet.

A method for assisting starting of a diesel engine applicable to high-altitude areas by using the above-mentioned system, comprising the following steps:

1) The temperature of the coolant and the atmospheric pressure at the air inlet are collected, and the engine air intake mode is initially set as follows: open the air inlet and enter the first channel of the intercooler through the turbocharged air intake pipe, and close the air inlet through the auxiliary booster The intake pipe enters the second channel of the intercooler;

2) Judging whether the current coolant temperature is lower than the temperature setting value under the current atmospheric pressure, if so, then perform step 3), if not, then perform step 4);

3) Close the air inlet and enter the first channel of the intercooler through the turbocharged air intake pipe and open the air inlet and enter the second channel of the intercooler through the auxiliary supercharged air intake pipe, and all the engine intake air flows through the low pressure ratio and large flow For fluid machinery, perform step 5);

4) Maintain the initial setting of the engine air intake mode, and perform step 5);

5) Determine whether the engine speed reaches the set speed, if yes, the engine starts successfully, and the engine intake mode is set to the initial setting mode, if not, skip to step 2).

Compared with the prior art, the present invention has the following advantages:

1) The present invention realizes the complete automatic control of the cold start of the engine, does not require a separate air filter, can meet the requirements of the diesel engine for air supply pressure and air supply volume under the premise of relatively low power consumption, and significantly improves the performance of the engine at high temperatures. The success rate of starting at altitude, shortening the start-up time of low compression ratio diesel engines, can make the diesel engine enter a stable idle state faster, and solve the problem of difficult starting of diesel engines at high altitudes.

2) The present invention can judge whether auxiliary starting is needed according to ambient atmospheric pressure and engine coolant temperature, and the MAP map for starting auxiliary judgment of the engine is stored in the control unit, and the coolant temperature limit values under different atmospheric pressures are also different. If the temperature is lower than the coolant temperature limit under the current atmospheric pressure, it is auxiliary start, otherwise normal start does not need assistance, this judgment method ensures the accuracy of start auxiliary judgment, and involves few parameters, which is conducive to reducing the complexity of control , without negatively affecting the control strategy.

3) The start assist judgment MAP map in the control unit of the present invention can be calibrated according to different engines and has flexibility. The performance of different diesel engines is different, and the starting performance requirements of diesel engines are also different in different working situations, which makes the starting assistance judgment of different diesel engines different. The starting assistance judgment MAP map in the control unit can be flexibly calibrated according to different engines to ensure that Applied to all diesel engines, where the MAP map uses a quadratic function to best reflect the relationship between atmospheric pressure and coolant temperature.

4) The present invention adopts low-pressure ratio and high-flow fluid machinery for air supply, which has the characteristics of large air supply volume, high efficiency, and low energy consumption. Compared with the previous gas storage tank, the low-pressure ratio large-flow fluid machine has a larger air supply volume, and does not require additional air storage tank layout space. Under the same air supply conditions, the low-pressure ratio large-flow fluid machine volume is smaller Small size facilitates placement on vehicles and mobile machinery. At the same time, the compression ratio and air supply flow rate of low-pressure ratio and high-flow fluid machinery can be selected according to the needs of diesel engines, so as to ensure that various types of diesel engines can have appropriate air supply pressure and air supply volume when starting, and at the same time reduce power consumption as much as possible. quantity. Low-pressure ratio and high-flow fluid have higher mechanical efficiency and do not require a lot of power, so they are especially suitable for vehicles and mobile machinery that use batteries as power sources to meet the needs of rapid air intake.

5) The present invention proposes an optimal scheme for the selection of low-pressure ratio and high-flow fluid machinery, wherein the low-pressure ratio refers to the compression ratio range of 1.2-1.6, and the flow of the fluid machinery is related to the engine displacement and idle speed, with Guaranteed to make up for the intake demand of high altitude and low pressure, it is convenient for users to improve the engine structure according to the standardized optimization scheme, and it has strong practicability.

6) The present invention has little changes to the structure of the original engine and realizes automatic control. The start assist system does not need to install an additional air filter, but takes air from the intake pipe behind the air filter of the original machine, and the fluid is mechanically compressed and sent to the intercooler, so there is no need for major changes to the original machine. The start assist system has a control unit, which is connected with the engine ECU control unit, and can automatically control the start assist system without manual operation, which reduces the workload of the driver.

Description of drawings

Fig. 1 is the structural representation of the system of the present invention;

Fig. 2 is a schematic diagram of the control unit and its input and output signals;

Figure 3 is the atmospheric pressure-coolant temperature MAP diagram.

In the figure: 1. Air filter, 2. Gas diverter valve, 3. Low pressure ratio and large flow fluid machinery, 4. Automatic pressure relief valve, 5. Gas confluence valve, 6. Intercooler, 7. Engine intake pipe, 8 , engine, 9, coolant temperature sensor, 10, engine exhaust pipe, 11, turbocharger, 12, atmospheric pressure sensor, 13, battery, 14, control unit, 15, air intake, 16, turbocharger Air intake pipe, 17, auxiliary supercharging air intake pipe.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is carried out on the premise of the technical solution of the present invention, and detailed implementation and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

As shown in Figure 1, a diesel engine starting assistance system suitable for high altitude areas is used to solve the problem of difficult starting of diesel engines, especially low compression ratio diesel engines at plateaus, and can calibrate the starting assistance control strategy according to different engines , the diesel engine comprises an air intake 15, a turbocharger intake pipe 16, an intercooler 6 and an engine 8, one end of a turbocharger 11 is set in the turbocharger intake pipe 16, and the other end of the turbocharger 11 is arranged on the engine On the engine exhaust pipe 10 of 8, an air filter 1 is provided at the air inlet 15, and the system includes an auxiliary supercharging air intake pipe 17, a low-pressure ratio large-flow fluid machine 3, an atmospheric pressure sensor 12, a coolant temperature sensor 9 and In the control unit 14, the air inlet 15 is respectively connected to the intake end of the turbocharged intake pipe 16 and the intake end of the auxiliary supercharged intake pipe 17 through the gas diverter valve 2, and the intake end of the intercooler 6 passes through the gas confluence valve 5 Respectively connect the outlet end of the turbocharged air inlet pipe 16 and the air outlet end of the auxiliary supercharged air inlet pipe 17, the low-pressure ratio large flow fluid machine 3 is arranged in the auxiliary supercharged air inlet pipe 17, and the air outlet end of the intercooler 6 is connected to the engine 8 At the air intake end, the atmospheric pressure sensor 12 is located at any position outside the pipe at the air intake 15 where the atmospheric pressure can be accurately measured, the coolant temperature sensor 9 is located in the cooling water jacket of the engine, and the low-pressure ratio large-flow fluid machine 3 is powered by the battery 13 For power supply work, the control unit 14 is respectively connected to the fluid machine 3 with a low pressure ratio and large flow rate, the gas confluence valve 5, the gas diversion valve 2, the atmospheric pressure sensor 12, the coolant temperature sensor 9 and the engine 8, and the air is cooled by the intercooler 6 and then supplied by the engine. The intake pipe 7 enters the engine 8, and the exhaust gas generated by the engine 8 enters the turbocharger 11 through the engine exhaust pipe 10, and then is discharged into the atmosphere.

The gas diverter valve 2 is used to control the air flow direction from the air filter 1. The gas diverter valve 2 has only two valve positions. The first position is to close the passage leading to the fluid machinery, and all the air flows into the turbocharger 11; the second position To close the passage to the turbocharger 11, all air flows into the fluid machine. Similarly, the gas confluence valve 5 is used to control the incoming flow direction of the air entering the intercooler 6. The gas confluence valve 5 has only two valve positions. The first position is to close the passage of the fluid machinery to the intercooler 6, and only the air from the turbine The air from the supercharger 11 flows into the intercooler 6; the second position is to close the passage leading to the turbocharger 11, and only the air from the fluid machine flows to the intercooler 6. Both the gas confluence valve 5 and the gas diversion valve 2 are electronically controlled valves.

The compression ratio of the fluid machine 3 with low pressure ratio and high flow rate ranges from 1.2 to 1.6. At the same time, the flow rate of the fluid machine 3 with low pressure ratio and high flow rate is related to the displacement and idle speed of the engine 8, satisfying the following formula:

Q＝0.036×P×V

In the formula, Q represents the flow rate, the unit is m ³ /h, P represents the engine displacement, the unit is L, V represents the idle speed, the unit is r/min. Low-pressure ratio and high-flow fluid machinery 3 can choose different types and different compression ratios and flow rates according to engine requirements, such as centrifugal compressors, vortex air pumps, axial flow compressors, etc., to meet the needs of engine starting assistance.

The auxiliary pressurized intake pipe 17 is provided with an automatic pressure relief valve 4, which is close to the fluid machinery and located behind the fluid machinery along the air flow direction. The maximum working pressure of the fluid machinery is preset. The pressure in the intake pipe 17 is opened when the pressure is greater than the maximum working pressure of the fluid machine, and the pressure is reduced to the set pressure and then closed.

The engine atmospheric pressure-coolant temperature MAP figure is prestored in the control unit 14, and the corresponding coolant temperature setting values under each atmospheric pressure are different (such as: when the atmospheric pressure is low, the engine 8 needs a higher coolant temperature to be normal. start, and when the atmospheric pressure is high, the engine 8 can start normally at a lower coolant temperature), and the MAP adopts different calibrations according to the engine 8, as shown in Figure 3, the atmospheric pressure-coolant temperature MAP in the Atmospheric pressure and coolant temperature satisfy the following formula:

T _c =0.083P _a ² -1.897P _a +349.841

In the formula, T _c represents the coolant temperature in K, and _Pa represents the atmospheric pressure in kPa. After the signals from the atmospheric pressure sensor 12 and the coolant temperature sensor 9 in the engine water jacket are transmitted to the control unit 14, the control unit 14 compares them with the pre-stored MAP map, and if the temperature is lower than the set value under the current atmospheric pressure temperature value, it is considered as a cold engine start, and starting assistance is required.

The input and output terminals of the control unit 14 are as shown in Figure 2, the Input1 of the control unit 14 is the engine starting signal, Input2 is the atmospheric pressure signal signal, Input3 is the coolant temperature signal, Input4 is the engine speed signal, and the Output1 signal is the control gas diverter valve 2 signal, the Output2 signal is the signal to control the gas confluence valve 5, and the Output3 signal is the signal to control the switch of the fluid machine 3 with a low pressure ratio and a large flow rate. The control unit 14 can be controlled by the engine ECU strategy. When starting, the intake air is pressurized by fluid machinery to optimize the charging efficiency of the diesel engine when starting, and solve the problem that the engine 8 cannot start due to insufficient intake air. The engine starting environment is judged by the atmospheric pressure-coolant temperature MAP map pre-stored in the control unit 14. The stored atmospheric pressure-coolant temperature MAP map can be specifically calibrated according to the engine starting performance requirements. At the same time, the working pressure and air supply of the fluid machinery The quantity can be selected according to the engine demand, so that it can meet the requirements of all diesel engines.

Working principle of auxiliary starting:

In the initial state, both the gas diverter valve 2 and the gas confluence valve 5 are located at position 1, the air inlet 15 is opened to enter the first passage of the intercooler 6 through the turbocharged air intake pipe 16, and the air inlet 15 is closed to enter the first channel of the intercooler 6 through the auxiliary pressurization. The air pipe 17 enters the second channel of the intercooler 6, while the fluid machine 3 with low pressure ratio and high flow rate does not work. After receiving the start signal of the engine 8, the control unit 14 receives the coolant temperature collected by the cooling water temperature sensor and the atmospheric pressure sensor 12 respectively. Atmospheric pressure at the air inlet 15, when it is judged that the current coolant temperature is lower than the temperature setting value under the current atmospheric pressure, the control unit 14 outputs auxiliary start instructions to the gas diverter valve 2 and the gas confluence valve 5 respectively, and at the same time sends an auxiliary start command to the low pressure The fluid machinery 3 with a larger flow rate outputs work instructions. At this time, the gas diverter valve 2 and the gas confluence valve 5 are both located at position 2, the first channel is closed and the second channel is opened until the engine 8 speed reaches the set speed, and the control unit 14 receives After the speed signal from the engine electronic control unit ECU, it will automatically switch the engine intake from the start assist system to the normal route from the turbocharger 11 to the intercooler, that is, the gas diverter valve 2, the gas confluence valve 5 and the low pressure ratio large flow The fluid machine 3 resets back to the initial state, and at this time all intake air flows through the turbocharger 11 and enters the intercooler 6 .

At the initial stage of starting, due to the low engine speed, the demand for air intake per unit time is also small. At this time, because the fluid machinery continuously supplies air to the intercooler 6, the pressure in the intake pipe behind the air pump may exceed the set value (such as 30kPa), at this time, the automatic pressure relief valve 4 behind the fluid machine is opened under the action of the internal and external pressure difference, and part of the air is discharged from the pressure relief valve until the pressure in the pipe returns to within the set value, and then the automatic pressure relief valve 4 is closed.

The gas diverter valve 2 and the gas confluence valve 5 are changed from position one to position two when assisting cold start, and air will not leak out from the turbocharger 11 at this moment. In the same way, the gas diverter valve 2 and the gas confluence valve 5 are simultaneously changed from position two to position one after the engine 8 is successfully started, and the air intake leading to the fluid machine is closed to prevent the high-pressure air formed by the turbine from converging from the gas when the engine 8 is working normally. Valve 5 and automatic pressure relief valve 4 leaked.

A method for assisting starting of a diesel engine applicable to high-altitude areas by using the above-mentioned system, comprising the following steps:

1) Collect the temperature of the coolant and the atmospheric pressure at the air inlet 15, and the initial setting of the air intake mode of the engine 8 is: open the air inlet 15 and enter the first channel of the intercooler 6 through the turbocharged air intake pipe 16 and close the air intake The port 15 enters the second channel of the intercooler 6 through the auxiliary supercharged intake pipe 17;

2) Judging whether the current coolant temperature is lower than the temperature setting value under the current atmospheric pressure, if so, then perform step 3), if not, then perform step 4);

3) Close the air inlet 15 and enter the first passage of the intercooler 6 through the turbocharged air intake pipe 16 and open the air inlet 15 and enter the second passage of the intercooler 6 through the auxiliary supercharged air inlet pipe 17, and the engine air intake is all Flow through the low-pressure ratio high-flow fluid machine 3, perform step 5);

4) Maintain the initial setting of the air intake mode of the engine 8, and perform step 5);

5) Determine whether the engine speed reaches the set speed, if so, the engine 8 starts successfully, and the engine air intake mode is set to the initial setting mode, if not, then skip to step 2).

In step 5), when the engine 8 continuously judges that the number of times that the engine 8 has not reached the set speed exceeds the set number of times in the mode of initial setting, then directly jump to step 3), wherein the set number of times can be 2 to 3 times , this step can effectively avoid the dead loop special situation of starting failure in the continuous initial setting mode, and further improve the success rate of engine cold starting.

It can be seen from the steps of the diesel engine start assist method that when the ambient temperature is higher than the temperature setting under the current atmospheric pressure, it can be started normally through the control of the control unit 14, reducing the consumption of electric energy of the battery 13; when the ambient temperature is low, The control unit 14 automatically adopts the auxiliary system to start the engine 8, shortens the starting time of the engine 8, and improves the success rate of starting the engine 8. When the engine 8 starts successfully, it enters the idling stage, and the intake air flows through the turbocharger 11 through the control of the control unit 14. , and turn off the fluid machinery.

Specifically, when the driver turns the key to the "ON" gear, the engine 8 is powered on, the control unit 14 detects the Input2 signal of the atmospheric pressure sensor 12, compares it with the pre-stored atmospheric pressure-coolant temperature MAP, and obtains the current atmospheric pressure Lower the minimum normal starting temperature limit, compare this limit with the detected coolant temperature Input3 signal, if the coolant temperature is lower than the limit, the control unit 14 will respectively send the gas diverter valve 2 through the Output1 signal and Output2 signal The gas confluence valve 5 is placed in the second position, and the fluid machine 3 with a low pressure ratio and a large flow rate is started by the Output3 signal.

During the starting process of the engine 8, if the control unit 14 detects that the input4 signal of the engine 8 speed reaches the idle speed, the control unit 14 respectively places the gas diverter valve 2 and the gas confluence valve 5 in position one through the Output1 signal and the Output2 signal, and through the Output3 Signal to close low pressure ratio high flow fluid machinery 3.

If the engine 8 is in a hot state when starting, the control unit 14 will accept the Input3 signal, and the start assist system will not be used.

In summary, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value. The advantages of the present invention specifically include:

1) The prior art system is complicated, the installation cost is high, and the engine 8 has been greatly changed, which may increase the failure rate of the engine 8 . And more parts also need a lot of space to arrange. On vehicles and mobile machinery, the space is very limited, and it is very difficult to arrange so many parts in practice. And the system of the present invention is mainly composed of low-pressure ratio fluid machinery, control unit 14 and some valves, so it takes up little space, and is light in weight, and the engine 8 is changed very little, so as to reduce the modification of the original diesel engine by the starting auxiliary system as far as possible, and reduce the cost. At the same time, it can also reduce the probability of malfunction after installing the start assist system, and will not cause damage to the stability and durability of the engine 8;

2) In terms of control methods, this application does not need to measure the ambient temperature, and the engine coolant temperature is used as the main influencing factor for judging whether assistance is needed for engine startup. As long as the engine coolant temperature is higher than the set value, even if the ambient temperature is low (i.e. low gas temperature), it will not have a significant impact on engine starting performance. Therefore, the present invention involves few measurement parameters, which is beneficial to reduce the complexity of control, and at the same time does not have negative impact on the control strategy.

3) The prior art requires a separate electric high-pressure air pump to replenish the high-pressure gas to the high-pressure air storage tank, and the high-pressure air pump consumes more power than the air pump. On vehicles and mobile machines, the electric energy is supplied by the battery 13, and the electric energy is limited. And the present invention adopts low-pressure ratio high-flow fluid machine 3, because the pressure ratio is low, so the advantages of high efficiency and low energy consumption, even if it runs simultaneously with the diesel engine starter motor, the battery power can also be satisfied. At the same time, the low-pressure ratio fluid machinery has a large flow rate, which can fully meet the start-up air demand of large diesel engines of heavy machinery and vehicles.

4) Due to the large difference in atmospheric pressure at different altitudes, the starting performance of diesel engines is also very different. For example, a diesel engine that can be started normally at an altitude of -40°C at an altitude of 0m and at a temperature of -15°C at an altitude of 4500m It has been unable to start normally. The temperature, pressure and other set values in the control strategy of the prior art are fixed values, and there is a lack of start-up control measures for altitude changes. In the control strategy of the present invention, for different altitudes, there is a pre-stored atmospheric pressure-coolant temperature MAP, that is, the set value of the coolant temperature changes with changes in atmospheric pressure, and the lower the atmospheric pressure (the higher the altitude) , the coolant temperature setting value is also higher. The prestored atmospheric pressure-coolant temperature MAP can be calibrated according to the starting performance requirements of different engines 8 . Through this MAP, the application can accurately control the start assist system under all altitude conditions, taking into account the two aspects of starting performance and battery power saving.

Claims (9)

1. A diesel engine start-up assist system applicable to high altitude areas, used to assist the start of the diesel engine, the diesel engine includes an air inlet, a turbocharged intake pipe, an intercooler and an engine, and it is characterized in that the system includes an auxiliary Supercharged intake pipe, low-pressure ratio and high-flow fluid machinery, atmospheric pressure sensor, coolant temperature sensor and control unit, the air inlet is respectively connected to the intake end of the turbocharged intake pipe and the auxiliary supercharged intake pipe through a gas diverter valve The inlet end of the intercooler is connected to the outlet end of the turbocharger inlet pipe and the outlet end of the auxiliary supercharger inlet pipe respectively through the gas confluence valve. The air outlet of the intercooler is connected to the air intake of the engine, the atmospheric pressure sensor is installed on the air inlet, the coolant temperature sensor is installed in the engine, and the control unit is respectively connected to a large Flow fluid machinery, gas confluence valve, gas diversion valve, atmospheric pressure sensor, coolant temperature sensor and engine; In the initial state, the gas diverter valve and the gas confluence valve open the air inlet to enter the first channel of the intercooler through the turbocharged intake pipe and close the air inlet to enter the second channel of the intercooler through the auxiliary supercharged intake pipe, and at the same time The low-pressure ratio and high-flow fluid machinery does not work. After the control unit receives the start signal of the engine, it receives the coolant temperature collected by the cooling water temperature sensor and the atmospheric pressure at the air inlet collected by the atmospheric pressure sensor. When it is judged that the current coolant temperature is lower than the current At the temperature setting value under atmospheric pressure, the control unit outputs auxiliary start commands to the gas diverter valve and gas confluence valve respectively, and at the same time outputs work commands to the low-pressure ratio and high-flow fluid machinery. At this time, the first channel is closed and the second channel is opened. Until the engine speed reaches the set speed, the gas diverter valve, the gas confluence valve and the low-pressure ratio high-flow fluid machinery reset back to the initial state. 2. A diesel engine starting assist system suitable for high-altitude regions according to claim 1, wherein the compression ratio of the low-pressure ratio and high-flow fluid machine ranges from 1.2 to 1.6. 3. A diesel engine start-up assist system suitable for high-altitude areas according to claim 1, wherein the flow rate of the low-pressure ratio large-flow fluid machine is related to engine displacement and idle speed, and satisfies the following formula: Q＝0.036×P×V In the formula, Q represents the flow rate, the unit is m ³ /h, P represents the engine displacement, the unit is L, V represents the idle speed, the unit is r/min. 4. A diesel engine starting assist system suitable for high-altitude areas according to claim 1, characterized in that the low-pressure ratio high-flow fluid machine adopts a centrifugal compressor, a vortex air pump or an axial flow compressor. 5 . The method for assisting diesel engine startup suitable for high-altitude areas according to claim 1 , wherein the fluid machine with low pressure ratio and high flow rate is powered by a battery. 6 . 6. A diesel engine starting assist system suitable for high altitude areas according to claim 1, wherein the control unit stores atmospheric pressure-cooling system which contains the current diesel engine temperature setting value under different atmospheric pressures. Liquid temperature MAP map, the atmospheric pressure and coolant temperature in the atmospheric pressure-coolant temperature MAP map satisfy the following formula: T _c =0.083P _a ² -1.897P _a +349.841 In the formula, T _c represents the coolant temperature in K, and _Pa represents the atmospheric pressure in kPa. 7. A diesel engine starting assist system suitable for high-altitude areas according to claim 1, wherein an automatic pressure relief valve is provided on the auxiliary booster intake pipe, and the automatic pressure relief valve is It opens when the pressure in the trachea is greater than the maximum working pressure of the fluid machine. 8 . The diesel engine start assist system suitable for high altitude areas according to claim 1 , wherein an air filter is provided at the air inlet. 9 . 9. A method for assisting diesel engine start-up suitable for high-altitude regions by using the system according to any one of claims 1-8, characterized in that it comprises the following steps: 1) The temperature of the coolant and the atmospheric pressure at the air inlet are collected, and the engine air intake mode is initially set as follows: open the air inlet and enter the first channel of the intercooler through the turbocharged air intake pipe, and close the air inlet through the auxiliary booster The intake pipe enters the second channel of the intercooler; 2) Judging whether the current coolant temperature is lower than the temperature setting value under the current atmospheric pressure, if so, then perform step 3), if not, then perform step 4); 3) Close the air inlet and enter the first channel of the intercooler through the turbocharged air intake pipe and open the air inlet and enter the second channel of the intercooler through the auxiliary supercharged air intake pipe, and all the engine intake air flows through the low pressure ratio and large flow For fluid machinery, perform step 5); 4) Maintain the initial setting of the engine air intake mode, and perform step 5); 5) Determine whether the engine speed reaches the set speed, if yes, the engine starts successfully, and the engine intake mode is set to the initial setting mode, if not, skip to step 2).