Dot-matrix structure-based cooling structure of electric spindle of numerical control machine tool

Abstract

The application discloses a kind of based on dot matrix structure's numerical control machine tool electric main shaft cooling structure, to improve the cooling efficiency of electric main shaft, improve temperature uniformity and reduce the flow resistance of cooling medium.The cooling structure includes a motor sleeve, and the cylindrical side wall is configured to form an annular interlayer space.A ring baffle is provided in the interlayer space, which divides the space into several subspaces, and each subspace is distributed with a dot matrix structure.The porosity of the dot matrix structure gradually changes along the flow direction of the cooling medium, achieving an optimized balance between flow resistance and heat exchange efficiency.The cooling medium enters through the central inlet, forms a circulating flow path through the staggered baffle opening section, and finally discharges from both ends of the outlet.The structure is also equipped with a temperature control system, and the flow of the cooling medium is dynamically adjusted through the PID method, thereby achieving optimized control of the cooling process.The application significantly improves the cooling performance and temperature uniformity of the electric main shaft through innovative structural design and control strategy.

Description

Technical Field

[0001] This invention belongs to the field of electric spindle cooling and temperature control technology, and relates to the heat management of electric spindles during high-speed operation. Specifically, it is a cooling structure for CNC machine tool electric spindles based on a dot matrix structure, which aims to improve the temperature uniformity of the electric spindle and reduce the flow resistance of the cooling medium. Background Technology

[0002] Electric spindles are core components of modern CNC machine tools and precision machining equipment, primarily used to convert electrical energy into mechanical energy to achieve efficient rotary motion. The design of electric spindles typically integrates the motor with the machine tool spindle, replacing the traditional transmission system with a direct drive method, enabling the machine tool to achieve higher precision and faster response speeds. As a core functional component of precision machining tools, electric spindles not only need to withstand high-speed operation but also need to maintain good stability during high-precision machining. Electric spindles are widely used in various CNC machine tools, machining centers, and other equipment requiring high-precision and high-efficiency machining; their performance directly determines the working efficiency and product quality of the entire machining system.

[0003] The rapid development of industrial machine tools has placed increasingly stringent demands on electric spindles. The increasing requirements for higher speeds, speed control, low vibration levels, and high power necessitate the use of high-speed motors in electric spindles. As a core functional component of precision machine tools, the high-speed electric spindle optimizes transmission and improves work efficiency by coordinating the motor with the spindle and mounting it within a motor sleeve. During operation, the high-speed electric spindle generates heat primarily through motor heating, bearing friction, hydraulic friction, and electromagnetic heating. If this heat cannot be dissipated effectively and promptly, it will cause the internal temperature of the electric spindle to rise, leading to thermal expansion and resulting in thermal deformation of parts and machining errors.

[0004] To control the temperature of electric spindles, existing technologies widely employ cooling systems for thermal management. Current cooling methods often involve creating flow channels in the motor sleeve, with the cooling medium flowing around the sleeve from one end to the other. The temperature of the cooling medium gradually increases during this flow, leading to uneven temperature distribution within the motor sleeve and creating a significant temperature gradient. This temperature gradient can generate thermal stress within the electric spindle, affecting its stability and machining accuracy. Furthermore, to improve cooling efficiency, existing cooling designs often increase the number of baffles to extend the flow path of the cooling medium and prolong the cooling time, thereby improving heat removal efficiency. However, increasing the number of baffles increases the flow resistance of the cooling medium, leading to increased energy consumption of the cooling system and potentially causing instability in the cooling medium flow, further impacting the cooling effect.

[0005] In summary, existing electric spindle cooling technologies have many shortcomings in terms of temperature uniformity, flow resistance, and flow path design. These problems not only affect the performance and machining accuracy of the electric spindle but may also lead to equipment failure and increased energy consumption. Therefore, optimizing the cooling structure of the electric spindle to achieve a more uniform temperature distribution and lower flow resistance is an urgent technical problem to be solved. Summary of the Invention

[0006] (I) Purpose of the Invention

[0007] To address the shortcomings and deficiencies of existing electric spindle cooling technologies, such as poor temperature uniformity, high flow resistance, and unreasonable flow path design, this invention proposes a CNC machine tool electric spindle cooling structure based on a lattice structure. This cooling structure primarily utilizes a rational arrangement of baffles and a lattice structure on the motor sleeve. The cooling medium flows through the lattice structure with gradually changing porosity to cool the electric spindle, thereby improving the temperature uniformity of the motor sleeve and reducing the flow resistance of the cooling medium, thus achieving more efficient thermal management. This cooling structure not only improves the temperature uniformity inside the motor sleeve but also reduces energy consumption caused by flow resistance through optimized flow path design, ensuring that the electric spindle maintains good thermal stability and working efficiency during high-speed, high-precision machining.

[0008] (II) Technical Solution

[0009] To achieve the objective of this invention and solve its technical problems, the present invention adopts the following technical solution:

[0010] A cooling structure for a CNC machine tool electric spindle based on a dot matrix structure, used to improve the cooling efficiency of the electric spindle, improve temperature uniformity, and reduce the flow resistance of the cooling medium, includes at least a motor sleeve, wherein a spindle, a motor rotor, and a motor stator are disposed within the motor sleeve, and the spindle is concentrically fixedly sleeved within the motor rotor, characterized in that:

[0011] The motor sleeve is an axially extending annular cylindrical structure. Its cylindrical sidewall is integrally constructed as an axially extending annular interlayer space for the circulation of cooling medium. The outer wall of the annular interlayer space is provided with at least one cooling medium inlet and two cooling medium outlets communicating with it. The cooling medium inlet is located near the center of the outer wall in the axial direction, and the two cooling medium outlets are respectively located at both ends of the outer wall in the axial direction. The cooling medium inlet is connected to the outlet of an external cold source that provides cooling medium through a pipe, and the cooling medium outlet is connected to the inlet of the external cold source through a pipe, thereby forming a cooling medium circulation path.

[0012] The annular interlayer space is provided with several annular baffles arranged around it along the axial direction. The baffles are designed to divide the annular interlayer space into several independent subspaces along the axial direction. The subspace located at the center along the axial direction is connected to the cooling medium inlet, and the two subspaces located at both ends along the axial direction are connected to the cooling medium outlet. Each baffle is provided with an opening section for the cooling medium to pass through, and the opening sections of two adjacent baffles are arranged vertically and vertically in the circumferential direction to form a circulating flow path for the cooling medium.

[0013] Each subspace of the annular interlayer space is provided with a lattice structure, and in each subspace, the porosity of the lattice structure gradually changes along the flow direction of the cooling medium. The lattice structure near the initial position has a larger porosity to reduce the initial flow resistance, while the lattice structure near the termination position has a smaller porosity to increase the heat exchange area and obtain a higher Reynolds number.

[0014] (III) Technical Effects

[0015] Compared with the prior art, the CNC machine tool electric spindle cooling structure based on a dot matrix structure of the present invention has the following beneficial and significant technical effects:

[0016] (1) This invention, by setting baffles arranged in a ring around the motor sleeve and a lattice structure with gradually varying porosity, allows the cooling medium to fully contact the lattice structure throughout the cooling path and effectively remove heat. The porosity of the lattice structure gradually decreases along the flow direction of the cooling medium. The initial section uses a larger porosity to reduce flow resistance, while the terminal section uses a smaller porosity to increase the heat exchange area. This ensures the heat exchange efficiency of the cooling medium throughout the process, significantly reduces the temperature gradient, ensures the uniformity of temperature distribution of the electric spindle, and thus improves machining accuracy and product quality.

[0017] (2) By reducing the number of baffles and the reasonable layout of the lattice structure, the present invention enables the cooling medium to maintain a sufficient flow path while greatly reducing the flow resistance of the cooling medium. Especially in the initial section, the large porosity of the lattice structure effectively reduces the initial flow resistance of the cooling medium, allowing the cooling medium to flow smoothly, thereby reducing the additional energy consumption caused by the flow, improving the overall efficiency of the cooling system, and reducing the operating energy consumption of the electric spindle cooling system.

[0018] (3) This invention, through a reasonable lattice structure layout, selects an appropriate porosity for the initial size of the lattice structure based on the viscosity of the cooling medium, ensuring better heat transfer while maintaining stable flow. The size of the lattice structure gradually changes along the flow direction, while the relative position remains unchanged. This reduces porosity to achieve a higher Reynolds number; simultaneously, it increases the lateral area of ​​the lattice structure, resulting in a larger heat exchange area, thereby reducing the adverse effects of a smaller temperature difference on heat transfer capacity.

[0019] (4) This invention transmits signals to the temperature controller via temperature sensors in the motor stator and bearing housing, and uses a PID method to transmit electrical signals to the flow regulating valve to control the flow rate of the cooling medium, thereby reducing excessive waste of cooling energy. The temperature control system combines multiple temperature sensors, a temperature controller, and a flow regulating valve, enabling real-time monitoring of temperature changes inside the electric spindle. Based on preset temperature thresholds and the PID control algorithm, it precisely adjusts the flow rate of the cooling medium, ensuring that the electric spindle maintains optimal cooling under different operating conditions. This avoids decreased machining accuracy due to excessive temperature fluctuations and also reduces the waste of cooling energy. Attached Figure Description

[0020] Figure 1 This is a cross-sectional schematic diagram of the CNC machine tool electric spindle cooling structure based on a dot matrix structure in this invention;

[0021] Figure 2 This is a schematic diagram of the flow channel of the cooling structure in this invention;

[0022] Figure 3 This is a schematic diagram of some of the lattice structures used in this invention, wherein: (A) is a body-centered cubic (BCC) structure, (B) is a face-centered cubic (FCC) structure, (C) is an arched lattice structure, and (D) is a needle-wing structure.

[0023] Figure 4 This is an enlarged view of the flow channel of the cooling structure in this invention;

[0024] Figure 5 This is a schematic diagram of the temperature control system of the cooling structure in this invention.

[0025] Explanation of reference numerals in the attached figures:

[0026] 1 is the main shaft, 2 is the rear bearing housing, 3 is the front bearing housing, 4 is the motor rotor, 5 is the motor stator, 6 is the motor sleeve, 7 is the baffle plate, 8 is the dot matrix structure, 9 is the cooling medium inlet, 10 is the cooling medium outlet, 11 is the temperature controller, 12 is the flow regulating valve, and 13 is the external cold source (cooling unit). Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be described in more detail below with reference to the accompanying drawings. The described embodiments are some, but not all, of the embodiments of this invention. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] To address the shortcomings and deficiencies of existing electric spindle cooling technologies, such as poor temperature uniformity, high flow resistance, and unreasonable flow path design, this invention aims to propose a CNC machine tool electric spindle cooling structure based on a dot matrix structure, which can improve the cooling efficiency of the electric spindle, enhance temperature uniformity, and reduce flow resistance.

[0029] As a specific example, such as Figures 1-5 As shown, the CNC machine tool electric spindle cooling structure based on a dot matrix structure of the present invention mainly includes baffles, dot matrix structures, and other structures arranged on the motor sleeve. Specifically, the CNC machine tool electric spindle cooling structure based on a dot matrix structure of the present invention includes a motor sleeve 6, in which a spindle 1, a motor rotor 4, and a motor stator 5 are provided. The spindle 1 is concentrically fixed in the motor rotor 4. The motor sleeve 6 has a front bearing chamber 3 and a rear bearing chamber 2 at its two axial ends, respectively. The spindle 1 is concentrically and rotatably supported in the motor sleeve 6 by bearing components in the front bearing chamber 3 and the rear bearing chamber 2, and both ends of the spindle 1 extend axially out of the motor sleeve 6.

[0030] The motor sleeve 6 is an axially extending annular cylindrical structure. Its cylindrical sidewall is integrally constructed as an axially extending annular interlayer space for the circulation of cooling medium. The outer wall of the annular interlayer space is provided with at least one cooling medium inlet 9 and two cooling medium outlets 10 communicating with it. The cooling medium inlet 9 is located near the center of the outer wall in the axial direction, and the two cooling medium outlets 10 are respectively located at both ends of the outer wall in the axial direction. The cooling medium inlet 9 is connected to the outlet of an external cold source 13 (e.g., a cooling unit) that provides cooling medium through a pipeline, and the cooling medium outlets 10 are connected to the inlet of the external cold source 13 through a pipeline, thereby forming a cooling medium circulation path.

[0031] Several annular baffles 7 are arranged axially in the annular interlayer space. The baffles 7 are designed to divide the annular interlayer space into several independent subspaces axially. The subspace located at the center axially is connected to the cooling medium inlet 9, and the two subspaces located at either end axially are connected to the cooling medium outlet 10. Each baffle 7 has an opening for the cooling medium to pass through, and the openings of adjacent baffles 7 are arranged in a staggered vertical arrangement circumferentially to form a circulating flow path for the cooling medium. Figure 2 As shown, the baffles 7 are arranged around the motor sleeve. Each baffle 7 has a section cut off to facilitate the passage of the cooling medium. The openings of two adjacent baffles 7 are opposite, i.e., arranged one above the other. The number of baffles is reasonably selected according to the length of the motor sleeve 6 to appropriately increase the flow of the cooling medium and allow it sufficient time to cool.

[0032] In each subspace of the annular interlayer space, lattice structures 8 are distributed. In each subspace, the porosity of the lattice structures 8 gradually changes along the flow direction of the cooling medium. The lattice structures 8 near the initial position have a larger porosity to reduce the initial flow resistance, while the lattice structures 8 near the termination position have a smaller porosity to increase the heat exchange area and obtain a higher Reynolds number.

[0033] By setting the cooling structure described above in this invention, stable flow and efficient cooling of the cooling medium within the motor sleeve are achieved, significantly reducing flow resistance and ensuring uniform temperature distribution of the electric spindle during high-load, high-precision machining, thereby further improving the working stability and machining accuracy of the electric spindle.

[0034] In a preferred embodiment of the present invention, the number of baffles 7 can be optimized based on the axial length of the annular interlayer space of the motor sleeve 6 and the flow characteristics of the cooling medium. This ensures that the cooling medium can fully contact the lattice structure 8 and dissipate heat uniformly as it flows through the path between the baffles 7, ensuring sufficient flow time for heat exchange while maintaining flow resistance within an acceptable range. This achieves optimal cooling effect and prevents excessive energy loss. Furthermore, the baffles 7 can also employ a variable cross-section design, with their thickness and the shape of the opening gradually changing along the axial direction. The baffles near the cooling medium inlet 9 are thinner and have larger openings to reduce initial flow resistance; while the baffles near the cooling medium outlet 10 are thicker and have smaller openings to increase fluid turbulence and heat exchange. The specific geometric parameters of the baffles 7 can be determined through topology optimization algorithms combined with thermal-fluid coupling analysis to achieve the optimal balance between flow resistance and heat exchange efficiency.

[0035] In a preferred embodiment of the present invention, in each subspace, the porosity of the lattice structure 8 at its initial position is determined according to the viscosity of the cooling medium to achieve a better heat transfer effect while ensuring stable flow. Furthermore, the porosity of the lattice structure 8 gradually decreases along the flow direction of the cooling medium to obtain a higher Reynolds number and increase the heat exchange area by changing the porosity. In addition, the lattice structure is made of a material with high thermal conductivity and corrosion resistance, and its geometry is set according to the flow characteristics of the cooling medium and the heat exchange requirements. Figure 3 The possible lattice structure forms used in this invention include, for example, at least one of the following: body-centered cubic (BCC) structure, face-centered cubic (FCC) structure, hexagonal close-packed (HCP) structure, diamond structure, arched lattice structure, needle-fin structure, honeycomb structure, and skeleton structure. Furthermore, this invention selects a suitable porosity for the lattice structure 8 based on the viscosity of the cooling medium. The porosity of the lattice structure 8 varies in different baffles 7, decreasing along the flow direction. For example... Figure 4 Taking the needle-fin shape as an example, at the initial position, the cooling medium temperature is low, and using a large porosity can further reduce flow resistance. During the flow process, the temperature of the cooling medium gradually increases, so a small porosity is used to increase the heat exchange area and minimize the adverse effects of the decreasing temperature difference on heat exchange capacity. As a preferred option, the porosity of the lattice structure ranges from 30% to 90%, with a larger porosity at the initial position maintained at 70% to 90% to reduce flow resistance, and a smaller porosity at the terminal position maintained at 30% to 50% to increase the heat exchange area and improve the cooling effect, thereby ensuring the uniformity of temperature distribution and cooling efficiency throughout the motor sleeve.

[0036] In a preferred embodiment of the present invention, the electric spindle cooling structure further includes a temperature control system, such as... Figure 5 As shown, the temperature control system includes at least a temperature controller 11 and a temperature sensor and a flow regulating valve 12 that are communicatively connected to the temperature controller 11. The temperature sensor is installed at the motor stator, front bearing chamber, rear bearing chamber, cooling medium inlet and / or cooling medium outlet to monitor the temperature changes of each key part in real time. The flow regulating valve 12 is installed on the connecting pipe between the cooling medium inlet and / or cooling medium outlet in the annular interlayer space and the external cold source 13. The temperature controller 11 adjusts the flow rate of the cooling medium by controlling the flow regulating valve 12 based on the real-time temperature data of each temperature measuring point, thereby realizing dynamic control of the electric spindle cooling process and ensuring the uniformity of temperature distribution and the optimization of cooling efficiency.

[0037] Furthermore, the temperature control system may also include a cooling medium flow detection device communicatively connected to the temperature controller 11. This device is installed on the connecting pipe between the cooling medium inlet and / or outlet of the annular interlayer space and the external cold source. It is used to detect the flow velocity and flow rate of the cooling medium in the annular interlayer space in real time, ensuring that the flow of the cooling medium is optimal throughout the cooling system. The temperature controller further refines the control of the flow regulating valve, ensuring temperature stability and uniformity. In addition, the temperature controller 11 can combine a preset temperature threshold and a PID control algorithm to adjust the cooling medium flow rate in real time based on real-time temperature data from various temperature sensors and / or the electric spindle load parameters. The temperature threshold is dynamically adjusted according to the electric spindle's operating state, environmental conditions, and the flow characteristics of the cooling medium to adapt to cooling requirements under different operating conditions. This achieves precise control of the electric spindle temperature, avoiding thermal deformation due to excessively high temperatures or energy waste due to excessively low temperatures, ultimately optimizing cooling efficiency and ensuring the efficient and stable operation of the electric spindle.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cooling structure for a CNC machine tool electric spindle based on a dot matrix structure, comprising at least a motor sleeve, wherein a spindle, a motor rotor, and a motor stator are disposed within the motor sleeve, and the spindle is concentrically fixedly sleeved within the motor rotor, characterized in that: The motor sleeve is an axially extending annular cylindrical structure. Its cylindrical sidewall is integrally constructed as an axially extending annular interlayer space for the circulation of cooling medium. The outer wall of the annular interlayer space is provided with at least one cooling medium inlet and two cooling medium outlets communicating with it. The cooling medium inlet is located near the center of the outer wall in the axial direction, and the two cooling medium outlets are respectively located at both ends of the outer wall in the axial direction. The cooling medium inlet is connected to the outlet of an external cold source that provides cooling medium through a pipe, and the cooling medium outlet is connected to the inlet of the external cold source through a pipe, thereby forming a cooling medium circulation path. The annular interlayer space is provided with several annular baffles arranged around it along the axial direction. The baffles are designed to divide the annular interlayer space into several independent subspaces along the axial direction. The subspace located at the center along the axial direction is connected to the cooling medium inlet, and the two subspaces located at both ends along the axial direction are connected to the cooling medium outlet. Each baffle is provided with an opening section for the cooling medium to pass through, and the opening sections of two adjacent baffles are arranged vertically and vertically in the circumferential direction to form a circulating flow path for the cooling medium. Each subspace of the annular interlayer space is provided with a lattice structure, and in each subspace, the porosity of the lattice structure gradually changes along the flow direction of the cooling medium. The lattice structure near the initial position has a larger porosity to reduce the initial flow resistance, while the lattice structure near the termination position has a smaller porosity to increase the heat exchange area and obtain a higher Reynolds number.

2. The cooling structure for the CNC machine tool electric spindle based on a dot matrix structure according to claim 1, characterized in that, The number of baffles is optimized based on the axial length of the annular interlayer space of the motor sleeve and the flow characteristics of the cooling medium, so as to ensure that the cooling medium can fully contact the lattice structure and dissipate heat evenly when flowing through the path between each baffle, and to ensure that the cooling medium has enough flow time for heat exchange, while keeping the flow resistance within an acceptable range.

3. The cooling structure for the CNC machine tool electric spindle based on a dot matrix structure according to claim 2, characterized in that, The baffle plate adopts a variable cross-section design, and its thickness and the shape of the opening section gradually change along the axial direction. The baffle plate near the inlet of the cooling medium is thinner and has a larger opening section to reduce the initial flow resistance, while the baffle plate near the outlet of the cooling medium is thicker and has a smaller opening section to increase heat exchange.

4. The cooling structure for the CNC machine tool electric spindle based on a dot matrix structure according to claim 1, characterized in that, In each subspace, the porosity of the lattice structure at the initial position is determined according to the viscosity of the cooling medium, so as to obtain a better heat transfer effect while ensuring stable flow. Furthermore, the porosity of the lattice structure gradually decreases along the flow direction of the cooling medium, so as to obtain a higher Reynolds number by changing the porosity, while increasing the heat transfer area.

5. The cooling structure for the CNC machine tool electric spindle based on a dot matrix structure according to claim 1, characterized in that, The lattice structure is made of a material with high thermal conductivity and corrosion resistance. Its geometry is selected from at least one of BCC structure, FCC structure, HCP structure, diamond structure, arched lattice structure, needle-fin structure, honeycomb structure and skeleton structure, and is set according to the flow characteristics of the cooling medium and the heat exchange requirements.

6. The cooling structure for the CNC machine tool electric spindle based on a dot matrix structure according to claim 5, characterized in that, The porosity of the lattice structure ranges from 30% to 90%, with a larger porosity at the initial position and maintained at 70% to 90% to reduce flow resistance, and a smaller porosity at the termination position and maintained at 30% to 50% to increase the heat exchange area and improve the cooling effect.

7. The cooling structure for the CNC machine tool electric spindle based on a dot matrix structure according to claim 1, characterized in that, The motor sleeve has a front bearing chamber and a rear bearing chamber at its two axial ends, respectively. The main shaft is concentrically and rotatably supported in the motor sleeve by bearing components in the front and rear bearing chambers, and both ends of the main shaft extend out of the motor sleeve in the axial direction.

8. The cooling structure for the CNC machine tool electric spindle based on a dot matrix structure according to claim 7, characterized in that, The electric spindle cooling structure also includes a temperature control system. The temperature control system includes at least a temperature controller and a temperature sensor and a flow regulating valve that are communicatively connected to the temperature controller. The temperature sensor is installed at the motor stator, front bearing chamber, rear bearing chamber, cooling medium inlet and / or cooling medium outlet to monitor the temperature changes of each key part in real time. The flow regulating valve is installed on the connecting pipe between the cooling medium inlet and / or cooling medium outlet of the annular interlayer space and the external cold source. The temperature controller adjusts the flow rate of the cooling medium by controlling the flow regulating valve based on the real-time temperature data of each temperature measuring point.

9. The cooling structure for the CNC machine tool electric spindle based on a dot matrix structure according to claim 8, characterized in that, The temperature control system also includes a cooling medium flow detection device that is communicatively connected to the temperature controller. The cooling medium flow detection device is installed on the connecting pipe between the cooling medium inlet and / or cooling medium outlet of the annular interlayer space and the external cold source. It is used to detect the flow velocity and flow rate of the cooling medium in the annular interlayer space in real time, and to further refine the control of the flow regulating valve through the temperature controller.

10. The cooling structure for the CNC machine tool electric spindle based on a dot matrix structure according to claim 9, characterized in that, The temperature controller combines a preset temperature threshold and a PID control algorithm to adjust the flow rate of the cooling medium in real time based on the real-time temperature data fed back by each temperature sensor and / or the load parameters of the electric spindle. The temperature threshold is dynamically adjusted according to the working state of the electric spindle, environmental conditions, and the flow characteristics of the cooling medium to adapt to the cooling requirements under different working conditions.

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