A pump and motor design method

Abstract

The application relates to a pump and motor design method, and relates to the technical field of pumps.The pump comprises a motor, and the motor comprises a shell; the shell forms a motor cavity; a cooling medium is filled in the motor cavity; the height of the cooling medium is higher than the height of a rotor of the motor and the motor cavity is not filled full. The application has the advantage that the pressure can be effectively adjusted.

Description

Technical Field

[0001] This application relates to the technical field of pumps, and in particular to a pump and motor design method. Background Technology

[0002] Existing water pumps often use oil-filled motors with pressure regulating diaphragm structures to adjust the pressure during motor temperature rise to avoid excessive internal pressure and thus prevent motor leakage and other problems. In addition, this solution usually requires the motor cavity to be filled with oil for effective heat dissipation. However, for water pumps that are inverted and have the motor built-in, when using a pressure regulating diaphragm structure, the diaphragm is difficult to install and function effectively due to the inversion and the pressure in the flow channel. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, one of the objectives of this application is to provide a pump and motor design method that has the advantage of effectively regulating pressure.

[0004] The above-mentioned objective of this application is achieved through the following technical solution: A pump includes an electric motor, the electric motor including a housing forming an electric motor cavity, the electric motor cavity being filled with a cooling medium, the height of the cooling medium being higher than the height of the rotor of the electric motor and not filling the electric motor cavity.

[0005] In a preferred embodiment, this application may be further configured such that: the housing contains a controller and a rear bearing housing, the rear bearing housing is connected to the housing and located at the end of the motor near the controller, the motor includes a motor shaft, the motor shaft is rotatably connected via the rear bearing and the rear bearing housing, and the rear bearing is at least partially in contact with the cooling medium.

[0006] This application also discloses a motor design method, including the following steps: Initialization steps: Calculate V d V is the total volume of the motor's internal cavity. y V is the volume of the cooling medium in the motor cavity. q The volume of the oil chamber is expressed in cubic meters (m³). 3 Let the reference temperature of the cooling medium inside the motor be T0 (unit: K), and the highest temperature of the cooling medium be T. m Let the unit be K, and let V be the oil filling volume at T0. y0 Initial gas volume V g0 The initial pressure P0 satisfies V y0 + V g0 +V q =V d ;where V y0 V g0 The units are all in meters. 3 P0 is in Pa. Pressure calculation steps: Calculate at T mBelow, the pressure P in the motor cavity m ; Steps for calculating oil filling volume: Assume the maximum bearing pressure of the shell is P. k Unit: Pa, with a safety factor k, then P m ≤kP k , will P m Take the maximum value kP k Substitute and convert, let V d - V q =Vz yields: ,in, ; Verification steps: Verify the minimum filling volume (excluding the volume inside the oil chamber) and determine the obtained V. y0 At that time, the cooling medium should be able to submerge the rotor inside the motor; if not, the structure should be adjusted so that the cooling medium meets the above requirements.

[0007] In a preferred embodiment, this application can be further configured such that the end of the motor shaft away from the rear bearing is rotatably connected to the housing via the front bearing, and also includes a seal verification step, in which the minimum failure pressure differential of the mechanical seal is set to P. e The unit is Pa, and the maximum pressure difference due to oil chamber pressure lag is... ,when Greater than the minimum failure pressure differential P of the mechanical seal e At this time, increase the front bearing clearance or reduce the voltage boost rate in the motor cavity.

[0008] In a preferred example, this application can be further configured as follows: The following calculation was performed. , , , Among them, the rate of change of pressure inside the motor cavity is Units: Pa / s, P A This represents the real-time pressure inside the motor, in Pa. P is the influence coefficient of the cross-section inside the motor cavity, in Pa / K. c The pressure inside the oil chamber is Pa; t is time, in seconds; A e The equivalent flow area of ​​the front bearing is , in square meters. The isothermal compressibility coefficient of the cooling medium is expressed in Pa. -1 ; The density of the cooling medium is expressed in kg / m³. 3 .

[0009] In a preferred embodiment, this application may further be configured to include an oil chamber volume calculation step and a motor cavity pressure rise rate. The transient pressure difference differential equation between the motor cavity and the oil chamber: ,make Find the peak value: Where K is the bulk modulus of the cooling medium, in Pa; Let be the flow coefficient of the cooling medium, dimensionless, let ,but And it needs to be no less than the minimum volume sufficient to install the mechanical seal. .

[0010] This application has the following advantages: 1. Since the internal space of the built-in motor is fixed, the semi-oil filling solution avoids the problem of the voltage regulating diaphragm not being able to adapt, while meeting the needs of the motor's internal cooling medium to expand due to temperature rise. 2. By designing an appropriate amount of oil, a balance between motor temperature rise and structural strength can be ensured. Furthermore, by rationally allocating the amount of oil and air, the structural dimensions can be optimized, excessive redundant design can be avoided, and the water pump can be made lighter. 3. By designing the oil chamber of the mechanical seal, excessive pressure difference between the motor cavity and the oil chamber can be avoided, which could lead to mechanical seal failure. Attached Figure Description

[0011] Figure 1 This is a cross-sectional structural diagram of this application.

[0012] Reference numerals: 1. Housing; 11. Motor cavity; 2. Stator; 3. Rotor; 4. Motor shaft; 5. Mechanical seal; 6. Front cover; 7. Rear cover; 8. Oil chamber. Detailed Implementation

[0013] The present application will be further described in detail below with reference to the accompanying drawings.

[0014] Reference Figure 1This application discloses a pump, including a motor. The motor includes a housing 1, which forms a motor cavity 11. The motor cavity 11 is filled with a cooling medium, the height of which is higher than the height of the motor rotor 3 but does not completely fill the motor cavity 11. A stator 2, a motor shaft 4, and a controller are disposed within the motor cavity 11 inside the housing 1. A front cover 6 and a rear cover 7 are respectively disposed at both ends of the motor. A front bearing seat and a rear bearing seat are respectively disposed between the housing 1 and the front cover 6 and the rear cover 7. The controller is disposed between the rear bearing seat and the rear cover 7. A mechanical seal 5 is also provided at the front bearing seat where the rotor 3 shaft is located. An oil chamber 8 is disposed at the front bearing seat corresponding to the mechanical seal 5. A front bearing and a rear bearing for mounting the motor shaft 4 are disposed on the front bearing seat and the rear bearing seat, respectively. The rear bearing is at least partially in contact with the cooling medium. In this embodiment, the height of the cooling medium is higher than the height of the rear bearing. The cooling medium can be insulating oil or other media with cooling function and insulation, such as propylene glycol. In some embodiments, when the conductive components are properly insulated, the cooling medium may not be insulated. The following description uses insulating oil as the cooling medium.

[0015] This application also discloses a motor design method, including the following steps: Initialization steps: Calculate V d V is the total volume of the motor's internal cavity. y V is the volume of the cooling medium in motor cavity 11. q The volume of the oil chamber is expressed in m³. 3 Let the reference temperature of the cooling medium inside the motor be T0 (unit: K), and the highest temperature of the cooling medium be T. m Let the unit be K, and let V be the oil filling volume at T0. y0 Initial gas volume V g0 The initial pressure P0 satisfies V y0 + V g0 +V q =V d ;where V y0 V g0 The units are all in meters. 3 P0 is in Pa. Pressure calculation steps: Calculate at T m Below, the pressure P in the cavity formed by shell 1 m ; Oil filling calculation steps: Assume the maximum bearing pressure of the motor housing is P. k Unit: Pa, with a safety factor k, then P m ≤kP k , will P m Take the maximum value kP k Substitute and convert, let V d - V q =Vz yields: ,in, ; Verification steps: Verify the minimum oil filling amount (excluding the volume inside oil chamber 8), and determine the obtained V. y0 At that time, the cooling medium should be able to submerge the rotor 3 inside the motor; if not, the structure should be adjusted so that the cooling medium meets the above requirements.

[0016] Sealing verification steps: Set the minimum failure differential pressure of the mechanical seal 5 to P. e The unit is Pa. The maximum pressure difference lag of oil chamber 8 is... (That is, because the temperature rises faster in the motor cavity 11 than in the oil chamber 8, and a hysteresis pressure difference is generated due to the obstruction of bearings, etc.), when Greater than the minimum failure pressure difference P of the mechanical seal. e At the same time, increase the front bearing clearance (i.e., the clearance that exists in the bearing itself) or reduce the voltage boosting rate in the motor cavity 11; The following calculation was performed. , , , The rate of change of pressure inside motor cavity 11 is... Units: Pa / s, P A This represents the real-time pressure inside the motor, in Pa. P is the influence coefficient of the cross-section inside the motor cavity 11, in Pa / K. c The pressure inside oil chamber 8 is Pa; t is time, s; A e The equivalent flow area of ​​the front bearing is , in square meters. The isothermal compressibility coefficient of the cooling medium is expressed in Pa. -1 ; The density of the cooling medium is expressed in kg / m³. 3 ; Oil chamber 8 volume calculation steps: Pressure rise rate inside motor cavity 11 The transient pressure difference differential equation between motor cavity 11 and oil chamber 8: ,make Find the peak value: Where K is the bulk modulus of the cooling medium, in Pa; Let be the flow coefficient of the cooling medium, dimensionless, let ,but And it needs to be no less than the minimum volume sufficient to install the mechanical seal 5. .

[0017] To further illustrate, the following description follows the steps in S10-S60. It should be noted that the step numbers are only for the purpose of understanding the process and do not necessarily imply a specific order of steps.

[0018] S10: V calculationd V is the total volume of the motor's internal cavity. y V is the volume of the cooling medium in motor cavity 11. q The volume of the oil chamber is expressed in m³. 3 ; Set the reference temperature (T0, in K) and the maximum allowable temperature (T) of the cooling medium inside the motor. m (Unit: K), T0 can be set approximately based on the ambient temperature; T m The upper limit is based on the motor failure temperature combined with a safety factor; Let the oil filling volume at T0 be V. y0 Initial gas volume V g0 The initial pressure P0 satisfies V y0 + V g0 +V q =V d ; Where V y0 V g0 Unit m 3 P0 is in Pa; S20: Calculate the pressure inside motor cavity 11 under the highest temperature condition: Since the maximum temperature rise ΔT=T m -T0, then the cooling medium V after expansion at the highest temperature ym =V y0 ·(1+βΔT), where β is the volumetric thermal expansion coefficient of the cooling medium, in Kelvin. -1 V ym Unit m 3 ; Then the gas volume V in this state gm = V g0 -(V ym - V y0 );V gm Unit m 3 ; Let P be the internal pressure of the motor at the highest temperature. m Unit: Pa; expanded from the gas equation: P0·V g0 / T0= P m ·V gm / T m ,but S30: Calculate the maximum initial fill volume: Maximum pressure bearing capacity of motor housing (P) k (unit: Pa), set a safety factor k, then P m ≤kP k ; P m Take the maximum value kPk Substitute and convert, let V d - V q =Vz yields: in, , S40: Verify the minimum oil filling amount (excluding the volume inside oil chamber 8), and determine the obtained V. y0 At that time, the cooling medium can submerge the rotor 3 or stator 2 inside the motor; if not, the structure is adjusted so that the cooling medium meets the above requirements; S50: Safety verification of mechanical seal 5; S51: Due to the presence of the front bearing, during the rapid temperature rise of the cooling medium in the motor cavity 11, the pressure and temperature transfer of the cooling medium in the oil chamber 8 are blocked by the front bearing, which may cause a pressure difference in the operating environment of the mechanical seal 5 and lead to the failure of the mechanical seal 5; according to the specifications and characteristics of the mechanical seal 5, the minimum failure pressure difference (P) of the mechanical seal 5 is set by referring to a table or based on experience. e (unit: Pa) S52: Since the oil chamber 8 is closed and filled with cooling medium, the dynamic flow of cooling medium and oil chamber 8 within the motor cavity 11 is dominated by the front bearing. Among them, P c The pressure inside oil chamber 8 is Pa; t is time, s; A e The equivalent flow area of ​​the front bearing is , in square meters. The isothermal compressibility coefficient of the cooling medium is expressed in Pa. -1 ; The density of the cooling medium is expressed in kg / m³. 3 ; S53: The relationship between pressure and temperature rise inside motor cavity 11 is obtained through experimental testing or simulation. Among them, P A This represents the real-time pressure inside the motor, in Pa. The influence coefficient of the cross-section inside motor cavity 11, in Pa / K; The rate of change of pressure inside motor cavity 11 can be obtained. The unit is Pa / s; S54: Calculate the maximum pressure difference due to pressure hysteresis in oil chamber 8. but Greater than the minimum failure pressure difference P of the mechanical seal. e At the same time, increase the front bearing clearance or reduce the voltage boost rate in the motor cavity 11; Furthermore, the minimum failure pressure difference P of the mechanical seal can also be used. eThe oil chamber is designed with an 8-volume volume to meet the pressure differential; S60: Calculate the volume of oil chamber 8; S61: Pressure rise rate inside motor cavity 11 ; S62: Transient pressure difference differential equation between motor cavity 11 and oil chamber 8: make Find the peak value: Where K is the bulk modulus of the cooling medium, in Pa; The flow coefficient of the cooling medium (considering contraction and friction) is dimensionless. S63: Order ,but S64: And it must be no less than the minimum volume sufficient to install mechanical seal 5. The implementation principle of this embodiment is as follows: by not completely filling the cooling medium, the problem of the pressure regulating diaphragm not being able to adapt is avoided, and the balance between motor temperature rise and structural strength can be guaranteed. In addition, the oil filling amount and air volume can be reasonably allocated, the structural size can be optimized, excessive redundant design can be avoided, and the water pump can be made lighter.

[0019] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A motor design method applied to a pump, the pump including a motor, the motor including a housing forming a motor cavity, the motor cavity being filled with a cooling medium, the height of the cooling medium being higher than the height of the motor rotor but not completely filling the motor cavity, characterized in that: Includes the following steps: Initialization steps: Calculate V d V is the total volume of the motor's internal cavity. y V is the volume of the cooling medium in the motor cavity. q Let T be the volume of the oil chamber, in m³; let T0 be the reference temperature of the cooling medium inside the motor, in K, and T be the highest temperature of the cooling medium. m The unit is K, and the volume of the cooling medium at T0 is denoted as V. y0 Initial gas volume V g0 The initial pressure P0 satisfies V y0 + V g0 +V q =V d ;where V y0 V g0 All units are in m³, and P0 is in Pa. Pressure calculation steps: Calculate at T m Below, the pressure P in the motor cavity m ; Steps for calculating oil filling volume: Assume the maximum bearing pressure of the shell is P. k Unit: Pa, with a safety factor k, then P m ≤kP k , will P m Take the maximum value kP k Substitute and convert, let V d - V q =Vz yields: ,in, ; Verification steps: Verify the obtained V y0 At that time, the cooling medium should be able to submerge the rotor inside the motor; if not, the structure should be adjusted so that the cooling medium meets the above requirements.

2. The motor design method according to claim 1, characterized in that: The housing contains a controller and a rear bearing housing. The rear bearing housing is connected to the housing and is located at the end of the motor closer to the controller. The motor includes a motor shaft, which is rotatably connected to the rear bearing and the rear bearing housing. The rear bearing is at least partially in contact with the cooling medium.

3. The motor design method according to claim 2, characterized in that: The end of the motor shaft furthest from the rear bearing is rotatably connected to the housing via the front bearing. The process also includes a seal verification step, in which the minimum failure pressure differential of the mechanical seal at the front bearing is set to P. e The unit is Pa, and the maximum pressure difference due to oil chamber pressure lag is... ,when Greater than the minimum failure pressure differential P of the mechanical seal e At this time, increase the front bearing clearance or reduce the voltage boost rate in the motor cavity.

4. The motor design method according to claim 3, characterized in that: The following calculation was performed. , Among them, the rate of change of pressure inside the motor cavity is Units Pa / s, P A This represents the real-time pressure inside the motor, in Pa. P is the influence coefficient of the cross-section inside the motor cavity, in Pa / K. c The pressure inside the oil chamber is Pa; t is time, in seconds; A e The equivalent flow area of ​​the front bearing is , in square meters. The isothermal compressibility coefficient of the cooling medium is expressed in Pa. -1 ; This refers to the density of the cooling medium, expressed in kg / m³.

5. The motor design method according to claim 1, characterized in that: It also includes the oil chamber volume calculation step, and the maximum pressure difference of the oil chamber pressure hysteresis is... Rate of pressure rise in motor cavity The transient pressure difference differential equation between the motor cavity and the oil chamber is as follows: Calculate the peak value: Where K is the bulk modulus of the cooling medium, in Pa; Let be the flow coefficient of the cooling medium, dimensionless, let ,but And it needs to be no less than the minimum volume required to install the mechanical seal. .

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