RU213326U1 - Dust and moisture-proof electric motor for sea-based unmanned complex - Google Patents

Abstract

The utility model relates to the field of electrical engineering, namely to electrical machines, and can be used as aircraft engines, in particular as engines of sea-based multi-rotor aircraft designed for search, rescue, measuring and other tasks in fresh water bodies. and salt water. SUBSTANCE: dust-and-moisture-proof electric motor for sea-based unmanned complex contains a housing, a stator installed inside the housing and a rotor of the electric motor installed in the housing on bearings with the possibility of axial rotation. In this case, the rotor of the electric motor is connected by means of a key to the shaft. The housing is hermetically sealed from the side of the shaft by a cover. A flange is made in the cover, inside of which two oil-resistant seals are installed, closed, in turn, by a seal fixing cover. The outer surface of the engine housing is made with longitudinal cooling fins located downstream. The use of the claimed technical solution makes it possible to provide engine cooling while maintaining its tightness. 6 w.p. f-ly, 12 ill.

Description

Field of technology to which the utility model belongs

The utility model relates to the field of electrical engineering, namely to electric machines, and can be used as aircraft engines, in particular as engines of sea-based multi-rotor aircraft designed for search, rescue, measuring and other tasks in freshwater reservoirs. and salt water.

State of the art

The engine housing is known from the prior art (EP 0048213, publ. 06.02.1985). Motor housing in the form of a tubular jacket (3), assembled in cross section from at least two parts of the shell (4, 5) surrounding the stator (1), on the outer side (8) of which the radial ribs of the shell (9, 19) protrude, into while the adjacent edges of the shell parts and they are held on the stator by connecting elements (6), characterized in that at least one edge of the shell part (4 or 5) is formed transversely by a hook section with a nose strip (12) directed away from the axis (M ) of the jacket, and this nose strip is inserted into the channel (11) of the adjacent part of the shell (5 or 4), while on the inside of the jacket, the radial ribs (10) resting on the stator are connected to the radial ribs (9, 19).

This technical solution is suitable for motors with an internal rotor (inrunner). Ribs on the inside of the cooling jacket reduce the heat transfer contact patch on the stator. Heat transfer is difficult in the joint area of the shell parts. The jackets are made of an extruded profile and do not form a hermetic casing, but serve only for additional cooling.

Also known from the prior art is a universal cooling jacket for an electric motor (US 98755474, publ. 09/05/2017). The body contains an inner surface configured to interface in the central part with a multilayer magnetic package of the electrical device; an outer surface comprising, in a central portion, cooling fins, each cooling fin extending in a radially outward direction and generally perpendicular to the axis of rotation of the shaft, and a cover plate having an inlet receiving liquid cooling from the intake manifold and an outlet opening supplying liquid cooling to the exhaust manifold, while the cooling fins are alternatively located higher and smaller near the intake manifold, and vice versa, progressively smaller and higher, near the exhaust manifold, the cooling fins being spatially located along the axis of rotation of the shaft, with all upper cooling fins having the same height, while the cover is supported onto and supported by the upper cooling fins, wherein the cover and cooling fins create a liquid cooling path between alternating higher cooling fins and smaller cooling fins from the inlet to the outlet, the liquid cooling path extending through liquid cooling from the first of the cooling fins, in a path formed between alternating cooling fins along the length of the rotation axis to the last of the cooling fins.

This technical solution is used with liquid cooling, which entails an increase in mass due to the introduction of a radiator, coolant and pump into the system. The reliability of the system decreases due to the appearance of additional elements.

Also known from the prior art is an electric motor with surface cooling (DE 2406014 A1, publ. 08/14/1976). The stator of a surface-cooled motor is in thermal contact with the housing. The housing has external radial cooling fins.

This technical solution uses passive cooling of the body fins without active airflow.

The essence of the utility model

The task solved by the claimed technical solution is to solve the problem of motor overheating in a completely sealed environment, due to the tight fit of the motor stator on the radiator housing.

The technical result of the claimed technical solution is to improve engine cooling while maintaining its tightness.

The technical result of the claimed technical solution is achieved due to the fact that the dust and moisture-proof electric motor for an unmanned sea-based complex includes a housing, a stator installed inside the housing and an electric motor rotor mounted in the housing on bearings with the possibility of axial rotation, while the motor rotor is connected by means of a key to the shaft, and the housing from the side of the shaft it is hermetically sealed with a cover, while the flange is made in the cover, inside which two oil-resistant seals are installed, closed, in turn, by a seal fixing cover, while the outer surface of the motor housing is made with longitudinal cooling ribs, made equal in height to the housing and located along the air flow from the fan blades located on the motor shaft.

In a particular case of implementation of the claimed technical solution, the motor housing is made of aluminum alloy.

In a particular case of the implementation of the claimed technical solution, the gland fixing cover is made of aluminum sheet 2 mm thick.

In a particular case of implementation of the claimed technical solution, the motor shaft is made of stainless steel.

In a particular case of the implementation of the claimed technical solution, the motor stator is installed inside the housing by means of a thermal fit using a heat-conducting compound.

In a particular case of the implementation of the claimed technical solution, the motor housing cover is made of aluminum alloy.

In a particular case of implementation of the claimed technical solution, the cover of the electric motor housing is fixed on the said housing by means of screws using an anaerobic thread locker.

Brief description of the drawings

Details, features, and advantages of this utility model follow from the following description of the embodiments of the claimed technical solution using the drawings, which show:

Fig. 1 - motor installation, sectional view;

Fig. 2 - stator;

Fig. 3 - stator winding;

Fig. 4 - engine housing;

Fig. 5 - engine housing cover;

Fig. 6 - motor shaft;

Fig. 7 - a specific example of the implementation of the claimed technical solution. Motor 1100W, 60 fins;

Fig. 8 - a specific example of the implementation of the claimed technical solution. Motor 1100 W, 44 fins;

Fig. 9 - a specific example of the implementation of the claimed technical solution. Motor 1100W, 30 fins;

Fig. 10 - a specific example of the implementation of the claimed technical solution. Motor 1100W, 20 fins;

Fig. 11 - a specific example of the implementation of the claimed technical solution. Motor 1100W, no fins;

Fig. 12 - a specific example of the implementation of the claimed technical solution. Motor 1700 W, 60 fins.

The figures indicate the following positions:

1 - body; 2 - stator; 3 - rotor; 4 - shaft; 5 - key; 6 - stuffing box; 7 - cover; 8 - seal fixing cover; 9 - bearings.

Utility Model Disclosure

A dust and moisture-proof electric motor for an unmanned aerial vehicle includes an aluminum housing (1) that acts as a radiator, a stator (2) of the electric motor installed inside the housing (1) of the power plant and a rotor (3) of the electric motor installed in the housing (1) on bearings (9) with the possibility of axial rotation .

The rotor (3) of the electric motor is connected by means of a key (5) to the shaft (4).

The housing (1) on the side of the shaft (4) is hermetically sealed with a cover (7). At the same time, a hole is made in the cover (7) for the mentioned shaft (4) and a flange is made, inside which two oil-resistant seals (6) are installed, ensuring the tightness of the shaft (4) exit through the cover (7), closed in turn by the cover (8) seal fixings.

In this case, the shaft (4) of the electric motor is made of AISI 304 stainless steel.

The cover (7) of the body (1) of the electric motor is made of aluminum alloy grade d16t, provides a tight connection with the body (1) of the electric motor and retains two oil-resistant seals (6).

Fixing the cover (7) of the body (1) of the motor unit is carried out using 11 screws m2x6 DIN 912 using an anaerobic thread lock. Fig. 5 (for clarity, the cover is shown in section).

The cover for fixing the oil seals of the motor unit is made of 2 mm sheet of aluminum grade d16t. It must ensure the tightness of the assembly of the power plant and be fixed with six screws m2x6 DIN 7991.

The motor stator is installed inside the housing by heat fit using a heat-conducting compound.

The motor housing acts as a stator cooling radiator and a bearing assembly for the motor rotor. The engine housing is made of aluminum alloy grade d16t. The motor housing acts as a stator cooling radiator and a bearing assembly for the motor rotor. Fig 4.

The engine housing is made with longitudinal cooling ribs made equal in height to the housing with an amount selected depending on the power and heat dissipation, located along the incoming air flow from the fan blades located on the motor shaft, i.e. the ribs are located on the outer surface of the cylindrical housing parallel to the motor shaft.

The propeller blows air onto the motor housing, cooling it. When the motor is sealed in a protective glass, heat exchange with the external environment worsens, which leads to overheating of the motor and its failure. To improve heat transfer and cooling of the engine, the said ribs are made. The height of the ribs is limited by the height of the motor housing.

The following are specific examples of the implementation of the claimed technical solution:

As part of the overheating solution for a sealed motor, a numerical thermal calculation was made, with a graphical simulation of the heat distribution over the motor housing. Thus, iteratively found the most suitable design of the engine housing, with longitudinal cooling fins located downstream.

The brushless motor as part of the propeller group of the UAV ensures the rotation of the propeller, creating a thrust force. The required motor power to create a thrust of 6.5 kgf paired with a 30' × 10.5' propeller is 746 W, while the maximum thrust required to reliably control a 25 kg vehicle can reach 9 kgf, the power consumption will be 1100 W. The determining factors for determining the size of the ribs and their number are: the dimensions of the engine that provides the necessary thrust; the speed of air movement through the radiator fins; maximum allowable engine operating temperature; thermal power of the engine.

Heat removal can be carried out by placing the radiator fins on the cylindrical surface of the engine housing. Due to this, the air forced by the propeller passes through the fins, providing forced cooling. The height of the ribs is limited by the height of the motor housing. In the 3D model, the length and number of ribs are specified, a thermal calculation is performed, and the model is corrected based on the results of the analysis. Consider finning options in the range from 20 to 60 ribs.

The boundary conditions for determining the parameters of the ribs are the maximum temperature at which irreversible changes in the properties of the magnets of the electric motor occur, and the mass-dimensional characteristics of the motor, which depend on the size and number of ribs. Thus, it is necessary to determine the minimum possible number of ribs and their length, providing a constant engine temperature of less than 120°C at an ambient temperature of 30°C.

The input parameters for the calculation are the thermal power of the motor and the coefficient of convective heat transfer.

The initial data for the calculation are:

λ - coefficient of thermal conductivity of the coolant, 0.0259 W/(m⋅K);

ν - kinematic coefficient of viscosity, 1.51⋅10 ^-5 m ² /s;

L - characteristic size, 43⋅10 ^-3 m (wall length along the coolant flow).

F - thrust force of the propeller, 89 N;

ρ - air density, 1.205 kg / m ³ ;

S is the area of the propeller disk, 0.265 ^m2 .

P _H - rated motor power, 1100 W;

η - motor efficiency, 0.85;

k _load - motor load factor, 1;

l - rib length, 20 mm.

Let us determine the speed of movement of the coolant according to the formula (3):

Next, we calculate the Reynolds number to determine the type of coolant flow (laminar Re<100000 or turbulent Re>100000):

To determine the Nusselt number, we use formula (5) for the laminar flow of the coolant:

Nu=0.66 (3.37⋅10 ⁴ ) ^0.5 =1.21⋅10 ²

Let us substitute the obtained value into (1) to calculate the convective heat transfer coefficient:

Let's enter the obtained value as the initial data in the thermal calculation in the Simulation environment to set the convection parameters.

We determine the thermal power of the motor using formula (6)

Let's enter the obtained value as initial data in the thermal calculation in the Simulation environment to set the engine heat release parameters.

After entering the input parameters, we will calculate and analyze the result.

The result is shown in Fig. 7-11, which show examples of implementation, namely:

in FIG. 7 shows a motor with a power of 1100 W, with a thermal power of 194 W of heat, the housing of this motor is made with 60 ribs, the mass of the stator housing is 526 g.

On FIG. 8 shows a motor with a power of 1100 W, with a thermal power of 194 W of heat, the housing of this motor is made with 44 ribs, the mass of the stator housing is 477 g.

On FIG. 9 shows an engine with a power of 1100 W, with a thermal power of 194 W of heat, the body of this engine is made with 30 ribs, the mass of the stator body is 427 g.

On FIG. 10 shows a motor with a power of 1100 W, with a thermal power of 194 W of heat, the housing of this motor is made with 20 ribs, the mass of the stator housing is 394 g.

On FIG. 11 shows a motor with a power of 1100 W, with a thermal power of 194 W of heat, this motor is made without fins, the mass of the stator housing is 325 g.

The highest temperature is observed in the contact zone of the motor stator with the housing. When analyzing the results obtained, a decrease in the maximum stator temperature with an increase in the number of ribs is observed. Also, with an increase in the number of fins, the decrease in the maximum temperature becomes less significant. Thus, when a certain value is reached, an increase in the number of fins will not have a significant effect on cooling with a significant increase in mass.

With the number of ribs equal to 60, the maximum stator temperature is 107°C, while the mass of the stator housing is 526 g.

Reducing the number of ribs to 44 leads to an increase in the stator temperature to 115°C, while the weight is reduced to 477 g. With such values, the safe operation of the electric motor is ensured, while the temperature margin is slightly more than 5%.

A further decrease in the number of fins leads to a significant increase in temperature. With the number of ribs equal to 30, the temperature rises to 128°C, with 20 ribs 143°C. It should be noted that with a smaller number of fins, the temperature is distributed more evenly over the body (this is evidenced by a smoother transition of colors on the color map of the calculation).

Indicative is the calculation of the hull without ribs. The stator temperature reaches 281°C, heat removal in this case is difficult.

The above study was carried out for a particular case of an electric motor used on a specific UAV, however, this design can be scaled and applied to electric motors with different power and sizes.

So, by varying the parameters of the number and length of the ribs, it is possible to determine the rational type of fins for a motor with a higher power (Fig. 12, a motor with a power of 1700 W):

Motor thrust with propeller 30'×10.5' is 11 kg;

Motor power - 1700 W;

Thermal power - 300 W.

Fin parameters to meet maximum temperature requirements: 60 fins 40 mm long.

Claims (7)

1. A dust and moisture-proof electric motor for a sea-based unmanned complex, including a housing, a stator installed inside the housing and an electric motor rotor mounted in the housing on bearings with the possibility of axial rotation, while the motor rotor is connected by means of a key to the shaft, and the housing is hermetically sealed from the side of the shaft by a cover, with At the same time, a flange is made in the cover, inside of which two oil-resistant seals are installed, closed, in turn, by a cover for fixing seals, while the outer surface of the engine housing is made with longitudinal cooling ribs, made equal in height to the housing and located along the air flow from the fan blades placed on the motor shaft. 2. The motor according to claim 1, characterized in that the motor housing is made of aluminum alloy. 3. The electric motor according to claim 1, characterized in that the gland fixing cover is made of aluminum sheet 2 mm thick. 4. Electric motor according to claim 1, characterized in that the motor shaft is made of stainless steel. 5. The electric motor according to claim 1, characterized in that the stator of the electric motor is installed inside the housing using a thermal fit using a heat-conducting compound. 6. The electric motor according to claim 1, characterized in that the motor housing cover is made of aluminum alloy. 7. Electric motor according to claim 1, characterized in that the motor housing cover is fixed on said housing by means of screws using an anaerobic thread lock.

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