Electronic expansion valve and assembling method thereof
Technical Field
The invention belongs to the field of fluid control, and particularly relates to an electronic expansion valve and an assembly method thereof.
Background
The electronic expansion valve is an element for regulating the flow of refrigerant in air conditioning system and consists of mainly driving part, driving part and flow regulating part. Generally, the power unit includes a stepping motor composed of a stator and a rotor, and a circuit board for controlling the stepping motor; the transmission part comprises a screw mechanism and a related limiting mechanism; the flow regulating component comprises a flow regulating mechanism consisting of a valve core and a valve seat and a valve body which can lead in and out fluid and can contain and fix the parts.
The working principle of an electronic expansion valve is generally as follows: the motor control chip on the circuit board can give a certain pulse to the motor stator according to the command of the superior controller, the motor rotor rotates under the driving of the pulse and drives the moving part in the screw mechanism to rotate around the fixing part in the screw mechanism, under the action of the thread pair, the moving part can also move axially while rotating around the fixing part, and meanwhile, the valve core connected to the moving part can approach or leave the valve seat and simultaneously change the flow area of the valve port on the valve seat, thereby realizing the purpose of regulating the flow of the refrigerant flowing through the valve port.
It should be added that the valve core and the moving part in the screw mechanism are connected by a spring, that is, the two are not rigidly connected but transmit the force by the spring, and a part with low surface friction coefficient is arranged at the relevant contact surface. The advantages of the design are as follows: in the valve closing process, after the valve core closes the valve port on the valve seat, the rotor and the moving part in the screw mechanism are allowed to continue rotating according to the original rotating direction and compress the spring, but the valve core can keep static relative to the valve seat at the moment (the friction coefficient of the valve core and the valve seat contact surface is greater than that of the part with the low surface friction coefficient), so that the rigid extrusion and friction of the valve core and the valve seat are avoided, the design ensures the service life of the valve seat and the valve core, and the sealing reliability in the valve closing process can be improved.
The limiting mechanism works in a mode that when the valve core contacts with the valve port on the valve seat in the valve closing process, the rotor and the moving part in the screw mechanism are allowed to rotate for a certain angle α according to the original rotating direction, then the limiting mechanism acts and limits the moving part in the screw mechanism to rotate continuously, but the moving part in the screw mechanism is allowed to do valve opening movement in the opposite direction, and the acting point of the limiting mechanism is recorded by the control chip and is used as the adjusting zero point.
The flow characteristic curve is a characteristic curve of the typical flow of the electronic expansion valve, wherein the abscissa represents the number of pulses and the ordinate represents the percentage of flow through the electronic expansion valve, it can be seen from the figure that the flow characteristic curve has a dead zone of regulation starting from the zero point, i.e. the electronic expansion valve remains closed and cannot regulate the flow, the cause of the dead zone has been described above, i.e. the rotor and the moving element in the screw mechanism continue to rotate at an angle α after the valve port is closed, and when the motor parameters are determined, the dead zone angle α can be converted to the corresponding number of pulses.
Disclosure of Invention
The invention aims to provide an electronic expansion valve and an assembling method thereof aiming at the defects of the prior art
The purpose of the invention is realized by the following technical scheme: an electronic expansion valve comprises a first assembly, a second assembly, a connecting seat 18, a sleeve 19, a drop-proof spring 20, a spring seat 21, a locking nut 22, a valve body 23 and a stator 26; the first combination body comprises a nut 10, a rotor 11, a valve core 12, a connecting spring 13, a connecting sleeve 14, a first gasket 15 and a second gasket 29; the second assembly comprises a screw 16 and a valve seat 17; the nut 10 is composed of a guide portion 101, an internal thread portion 102, and a first stopper portion 103; the rotor 11 is composed of permanent magnets 112 and a connecting plate 111; the valve core 12 is formed by a connecting section 121, a matching section 122 and a flow regulating section 123 in sequence; the diameter of the connecting section 121 is smaller than that of the matching section 122 to form a shaft shoulder; the screw 16 is provided with an external thread 161, an external circle 162 and an internal through hole 163; the valve seat 17 is provided with a valve port 171, an inner cavity 172 and a radial hole 173; the connecting base 18 is provided with a second limiting part 181, a flange part 182 and an inner hole; the valve body 23 is provided with a main cavity 231 and a fluid inlet and outlet 232; the first limiting part 103 is positioned on the lower end surface of the internal thread part 102, and the guide part 101 is fixedly connected with the connecting plate 111; the connecting spring 13 is sleeved on the connecting section 121, the connecting section 121 penetrates through a through hole at the upper end of the guide part 101, one end of the connecting spring 13 in a compressed state props against a shaft shoulder of the valve core 12, and the other end props against the guide part 101 through a second gasket 29; the connecting sleeve 14 is fixedly connected with the connecting section 121, and the lower end of the connecting sleeve 14 abuts against the guide part 101 through the first gasket 15; the external thread 161 is screwed with the internal thread 102 by inserting the external circle 162 into the guide part 101; the valve core 12 is inserted into the inner cavity 172 through the inner through hole 163; the screw 16 passes through the inner hole of the connecting seat 18 and is inserted into the inner cavity 172 and fixedly connected with the valve seat 17; the second limiting part 181 is located on the upper end surface of the connecting seat 18, and the connecting seat 18 is fixedly connected with the valve seat 17; the valve seat 17 is inserted into the main cavity 231; one end of a sleeve 19 is open, the other end of the sleeve is closed, the sleeve is sleeved outside the rotor 11, the closed end of the sleeve 19 is connected with a first assembly through a spring seat 21, a release-preventing spring 20 in a compressed state and a first gasket 15 in sequence, and the open end of the sleeve 19 is fixedly connected with a connecting seat 18; a lock nut 22 is sleeved on the connecting seat 18 and is screwed with the valve body 23 to press the connecting seat 18 in the main cavity 231; the stator 26 is arranged outside the sleeve 19.
Further, the guide portion 101 is made of a metal material; the internal thread portion 102 and the first stopper portion 103 are both made of a modified synthetic resin material.
Further, the internal thread portion 102 and the first limiting portion 103 are integrally formed on the guide portion 101 by insert injection molding; the permanent magnet 112 is obtained by injection molding on the outer side of the connecting plate 111 through an insert injection molding process.
Further, the first combination, the second combination, the connecting seat 18 and the main cavity 231 are coaxial; the nut 10, the rotor 11, the valve core 12, the connecting spring 13, the connecting sleeve 14, the first washer 15 and the second washer 29 are coaxial; the screw 16 and the valve seat 17 are coaxial; the guide part 101 and the internal thread part 102 are coaxial; the permanent magnet 112 and the connecting plate 111 are coaxial; the connecting section 121, the matching section 122 and the flow regulating section 123 are coaxial; the external thread 161, the external circle 162 and the internal through hole 163 are coaxial; the valve port 171 and the inner cavity 172 are coaxial; the flange portion 182 and the inner bore of the connecting socket 18 are coaxial.
Further, the connecting sleeve 14 is in interference fit with the connecting section 121; the outer circle 162 is in clearance fit with the guide part 101; the fitting section 122 is in clearance fit with the inner through hole 163; the screw 16 is in interference fit with the inner cavity 172; the inner hole of the connecting seat 18 is in clearance fit with the screw 16.
Further, the acting force of the connecting spring 13 is between 10N and 15N.
Further, the radial holes 173 are in communication with the inner cavity 172; the radial holes 173 communicate with the main chamber 231.
Further, a first O-ring 24 and a second O-ring 25 are included, the first O-ring 24 being located between the flange portion 182 and the main cavity 231; the second O-ring 25 is located between the valve seat 17 and the main chamber 231; the first O-ring 24 and the second O-ring 25 are both rubber rings for sealing.
Further, the stator 26 drives the rotor 11 to rotate by receiving a pulse signal.
The assembling method of the electronic expansion valve comprises the following steps:
(1) first assembling the first assembly, then sleeving the second assembly on the connecting seat, screwing the first assembly into the second assembly through the internal thread portion 102 and the external thread 161, after the flow-rate adjusting section 123 contacts the valve port 171, continuing to rotate the first assembly by the dead zone angle α, and finally adjusting the connecting seat 18 to make the first limiting portion 103 contact with the second limiting portion 181 at the contact height H1L/2, comprising the following substeps:
(1.1) after assembling the first assembly, insert case 12 into the interior through-hole of profile modeling frock 28, make flow control section 123 contact valve port 171 and form the sealing line, push down adapter sleeve 14, make the terminal surface in internal thread portion 102 support profile modeling frock 28 up end, and the perpendicular distance between the terminal surface in internal thread portion 102 to the sealing line is:
H2=H3+H4+H5-(180-α)*L/360
wherein H3For sealing the vertical distance of the line to the bottom surface of the connecting socket 18, H4Is the vertical distance H from the bottom surface of the connecting seat 18 to the upper end surface of the second limiting part 1815L is the height of the first stopper 103, and L is the pitch of the internal thread 102 or the external thread 161; at this time, the connecting sleeve 14 and the connecting section 121, the connecting plate 111 and the guide part 101 are fixedly connected to complete the assembly of the first combination; the profiling tool 28 is provided with a coaxial inner through hole and a valve port which have the same shape and size with the inner through hole 163 of the screw 16 and the valve port 171 of the valve seat 17;
(1.2) assembling the first combination, the second combination and the coupling socket 18 according to the rotation moment of the first combination and the coupling socket 18, comprising the substeps of:
(1.2.1) fixing the valve seat 17, sleeving the connecting seat 18 on the second assembly, screwing the first assembly assembled in the step (1.1) into the second assembly, detecting the rotation torque of the first assembly, when the rotation torque of the first assembly is changed from being smaller than a first judgment threshold to being larger than the first judgment threshold and being smaller than a second judgment threshold, indicating that the flow regulating section 123 is in contact with the valve port 171, continuing to screw the first assembly into the second assembly, and stopping after rotating the dead zone angle α;
(1.2.2) fixing the valve seat 17 and the rotor 11, rotating the connecting seat 18 and detecting the rotating moment of the connecting seat 18, when the rotating moment of the connecting seat 18 is suddenly increased and is greater than a second judgment threshold value, indicating that the second limiting part 181 is in contact with the first limiting part 103, stopping rotating the connecting seat 18 at the moment, and fixing the connecting seat 18 on the valve seat 17;
(2) an upper stop spring 20 and a spring seat 21 are arranged on the connecting sleeve 14, a sleeve 19 is sleeved on the connecting sleeve, and the opening end of the sleeve 19 is fixed on the connecting seat 18;
(3) fitting the lock nut 22 over the coupling socket 18, inserting the valve seat 17 into the main cavity 231, and tightening the lock nut 22 downwardly to seat the coupling socket 18 in the main cavity 231;
(4) the stator 26 is arranged outside the sleeve 19.
The electronic expansion valve has the advantages that the electronic expansion valve comprises a spiral mechanism, a flow regulating mechanism, a limiting mechanism, a driving part and a valve body capable of introducing and guiding out fluid and accommodating and fixing the parts, wherein a guide part made of metal has high machining precision so that the guide part can smoothly rotate around an outer circle part of a screw rod, the guide part made of metal and a rotor connecting plate made of metal can be fixedly connected together through laser welding, an internal thread part made of modified synthetic resin materials can reduce the friction coefficient between internal threads and external threads, improve the transmission efficiency between the internal threads and the external threads, and reduce the noise between the internal threads and the external threads.
Drawings
The invention is further illustrated with reference to the following figures and examples:
FIG. 1 is a schematic illustration of an electronic expansion valve flow characteristic curve;
FIG. 2 is a general block diagram of the present invention;
FIG. 3 is a schematic structural view of a first assembly of the present invention;
FIG. 4 is a schematic structural diagram of a second assembly and a connecting socket of the present invention;
FIG. 5 is a schematic diagram showing the vertical sectional views of the first combination, the second combination and the connecting seat and the position relationship of the position-limiting mechanism when the valve port is just closed;
FIG. 6 is a schematic structural view of a profiling fixture of the present invention;
FIG. 7 is a graphical illustration of the rotational moment as a function of rotational angle during the determination of the position of the first combination;
FIG. 8 is a schematic view of a curve of a rotation moment varying with a rotation angle in determining the position of the connecting seat;
FIG. 9 is a flow chart of assembling the first combination, the second combination and the connecting socket;
in the figure, 10 nuts, 101 guide parts, 102 internal thread parts, 103 first limit parts, 11 rotors, 111 connecting plates, 112 permanent magnets, 12 valve cores, 121 connecting sections, 122 matching sections, 123 flow regulating sections, 13 connecting springs, 14 connecting sleeves, 15 first gaskets, 16 screws, 161 external threads, 162 outer circles, 163 internal through holes, 17 valve seats, 171 valve ports, 172 internal cavities, 173 radial holes, 18 connecting seats, 181 second limit parts, 182 flange parts, 19 sleeves, 20 anti-release springs, 21 spring seats, 22 locking nuts, 23 valve bodies, 231 main cavities, 232 fluid inlet and outlet ports, 24 first O-shaped rings, 25 second O-shaped rings, 26 stators, 27 circuit boards, 28 profiling tools and 29 second gaskets.
Detailed Description
For convenience of the text, the upper, lower, left and right appearing hereinafter merely represent the upper, lower, left and right in the drawings, and do not necessarily represent the actual spatial relationship of the product.
Fig. 2 is a general structural view of the present invention, which includes a first assembly, a second assembly, a connection socket 18, a sleeve 19, a drop-off prevention spring 20, a spring seat 21, a lock nut 22, a valve body 23, a first O-ring 24, a second O-ring 25, a stator 26, and a circuit board 27.
As shown in fig. 3, the first combination includes a nut 10, a rotor 11, a spool 12, a connection spring 13, a connection sleeve 14, and first and second washers 15 and 29.
The nut 10 is composed of a guide part 101, an internal thread part 102 and a first limiting part 103, wherein the guide part 101 is made of metal material; an internal thread part 102 and a first limiting part 103 are injected on a guide part 101 by adopting an insert injection molding process, the guide part 101 and the internal thread part 102 are coaxial, and the first limiting part 103 is a boss positioned on the lower end face of the internal thread part 102; the internal thread portion 102 and the first limiting portion 103 are formed by integral injection molding, and the material is modified synthetic resin with high strength, wide temperature resistance range, low friction coefficient and good wear resistance, such as PPS (polyphenylene sulfide) added with a modified material or PEEK (polyether-ether-ketone) added with the modified material.
The rotor 11 is composed of permanent magnets 112 and a connecting plate 111, and coaxial tubular permanent magnets 112 are molded outside the annular connecting plate 111 by an insert molding process. The connecting plate 111 is laser-welded to the outside of the annular boss on the upper end surface of the guide 101 of the nut 10, and rigidly fixes the rotor 11 to the outside of the nut 10.
The valve core 12 is composed of a connecting section 121, a matching section 122 and a flow regulating section 123 which are coaxial in sequence; wherein, the diameter of the connecting section 121 is smaller than that of the matching section 122 to form a shaft shoulder, and the flow regulating section 123 is in a conical pen head shape.
The connecting spring 13 is sleeved on the connecting section 121 of the valve core 12, and the connecting section 121 is inserted into the nut 10 and penetrates out of a through hole on the upper end surface of the guide part 101 of the nut 10; one end of the connecting spring 13 is abutted against the shaft shoulder of the valve core 12, and the other end is abutted against the guide part 101 through a second gasket 29 which has a low surface friction coefficient; the connecting sleeve 14 is sleeved at the upper end of the connecting section 121, and the connecting sleeve 14 is in interference fit with the connecting section 121 and ensures the reliability of connection through laser welding; the lower end of the connecting sleeve 14 is abutted against the upper end surface of the guide part 101 through a first gasket 15, so that the connecting spring 13 is in a compressed state, and the valve core 12 is elastically connected inside the nut 10 under the action of the spring force; the rigidity and the compression amount of the connecting spring 13 are designed so that the spring force accumulated by the connecting spring 13 at this time is set between 10N and 15N.
As shown in fig. 4, the second assembly is composed of a screw 16 and a valve seat 17.
The screw 16 is externally provided with a section of external thread 161 and a section of external circle 162, and is internally provided with an axial internal through hole 163; the external thread 161, the external circle 162 and the internal through hole 163 are all coaxial. The outer circle 162 is positioned at the upper end of the screw 16, and the external thread 161 is positioned below the outer circle 162; the outer circle 162 is inserted into the guide part 101 of the nut 10 and is in clearance fit with the guide part 101; the external thread 161 is threadedly engaged with the internal thread portion 102 of the nut 10 to allow the nut 10 to move axially by rotating about the screw 16; the fitting section 122 of the spool 12 is inserted into the inner through hole 163 to be clearance-fitted with the inner through hole 163.
The valve seat 17 is internally provided with a valve port 171 and an inner cavity 172, and is also provided with a plurality of radial holes 173 communicated with the inner cavity 172 and uniformly distributed along the circumference of the valve seat; the valve port 171 is coaxial with and communicates with the internal cavity 172. The lower end of the screw 16 is inserted into the cavity 172 of the valve seat 17, and is in interference fit with the cavity 172 and is laser welded to ensure the reliability of connection, so that the valve port 171 is coaxial with the through hole 163 in the screw 16, and the flow regulating section 123 of the valve element 12 is inserted into the cavity 172 through the through hole 163, can move axially along the through hole 163, and smoothly and freely approaches or leaves the valve port 171.
A boss is provided on the upper end surface of the connecting seat 18 as the second limiting portion 181, and the connecting seat 18 and the second limiting portion 181 are integrally formed. An inner hole is formed in connecting seat 18, and the second assembly is inserted into the inner hole of connecting seat 18; the inner hole of connecting seat 18 is in clearance fit with the lower end of screw 16, so that connecting seat 18 can rotate around the second assembly, the lower end face of connecting seat 18 is welded on the shaft shoulder at the upper end of valve seat 17 through laser, and connecting seat 18 and valve seat 17 are coaxial. Connecting section 18 is also externally provided with a flange portion 182.
The valve body 23 is provided with a main cavity 231 and a fluid inlet and outlet 232 which are communicated, the main cavity 231 is communicated with an inner cavity 172 of the valve seat 17 and is coaxial, and is also communicated with a radial hole 173 of the valve seat 17, and can introduce and guide fluid and contain and fix the parts;locking nut22 is sleeved outside the connecting seat 18, and the flange part 182 of the connecting seat 18 below the connecting seat 18 is fixed in the main cavity 231 of the valve body 23 through screwing with the valve body 23, and a first O-shaped ring 24 for sealing is arranged between the flange part 182 of the connecting seat 18 and the main cavity 231; the second assembly is inserted into the main cavity 231 through the inner hole of the connecting seat 18, and a second O-ring 25 for sealing is also arranged between the valve seat 17 and the main cavity 231; the first and second O- rings 24 and 25 are both rubber rings.
One end of the sleeve 19 is open and the other end is closed, and the sleeve is sleeved outside the first assembly; the open end of sleeve 19 is laser welded to the shoulder of coupling housing 18 above flange 182 of coupling housing 18. The closed end of the sleeve 19 is connected with the first combination body through a slip-off prevention spring 20 and a spring seat 21, the slip-off prevention spring 20 is sleeved outside the connecting sleeve 14, one end of the slip-off prevention spring abuts against the first gasket 15 below the connecting sleeve 14, and the other end of the slip-off prevention spring abuts against the closed end of the sleeve 19 through the spring seat 21 above the slip-off prevention spring.
The stator 26 is arranged outside the sleeve 19 and fixed on the valve body 23; the circuit board 27 is electrically connected to the stator 26 and fixed to the stator 26, and the circuit board 27 has a control chip for applying a pulse signal to the stator 26, and drives the rotor 11 to rotate via the stator 26. The model of the control chip in this embodiment is MLX 81315.
FIG. 9 is a flow chart of the assembly process of the first assembly, the second assembly and the connecting seat of the present invention, the core idea is that firstly, the dimension chain is shortened by the assembly reference on the profiling fixture 28 to ensure that the actual contact height of the spacing mechanism meets the design requirement, thereby improving the assembly qualification rate of the product, secondly, the assembly position is determined by comparing the numerical relationship of the rotation moment value and the set threshold value, the size of the dead zone angle α can be arbitrarily set, and the consistency of the dead zone angle α is very good, the assembly process of the present invention includes the following steps:
(1) assemble first combination, second combination and connecting seat 18 together, assemble first combination at first, then the connecting seat is sheathe in to the second combination, screw in the second combination at the uniform velocity through internal thread portion 102 and external screw thread 161 with first combination, after flow control section 123 contacted valve port 171, first combination continued at the uniform velocity turned angle α (dead zone angle), adjust connecting seat 18 at last and make first spacing portion 103 contact with second spacing portion 181 (stop gear), stop gear's contact height is H1(ii) a The method specifically comprises the following substeps:
(1.1) determining the vertical distance H from the lower end surface of the threaded part 102 of the first combination nut 10 to the sealing line formed by the contact of the flow regulating section 123 and the valve port 171 through the profiling tool 282Solving the contact height H of the limiting mechanism1The purpose of this is to shorten the dimension chain by the assembly reference on the profiling tool 28, thereby improving the assembly yield of the product.
Screw mechanism (inner)Thread part 102 and external thread 161) determines the contact height H by the operation mode of spiral lifting1Less than the pitch L if the contact height H1The design is larger, and is close to the thread pitch L, so that the risk of contact of the limiting mechanism in advance by one circle exists in the assembly process; if the contact height H1The design is small, so that the risk of contact of the limiting mechanism after one circle of lag exists in assembly; so that the contact height H1Which is half the pitch L of the internal thread 102 or the external thread 161. Influence the contact height H of the stop gear1Including the vertical dimension on the connecting socket 18, the vertical dimension on the valve seat 17, the diameter of the valve port 171, the diameter of the flow regulating section 123, the vertical dimension on the valve core 12, the thickness of 2 washers, the height of the connecting sleeve 14 and the vertical dimension on the nut 10, at least 9 dimensions of 7 parts are involved, so that the assembly in the conventional way will result in the actual contact height H1Fluctuating over a relatively large interval, with the risk of the stop mechanism making contact one revolution ahead or behind.
Fig. 5 is a schematic diagram of the vertical sectional view (fig. 5a), the top view (fig. 5b) and the position relationship of the limiting mechanism (fig. 5c) of the first combination body, the second combination body and the connecting seat 18 just after the valve port 171 is closed by the flow regulating section 123. When the flow regulating section 123 contacts the valve port 171, the vertical distance between the lower end surface of the nut 10 and the sealing line formed by the contact between the flow regulating section 123 and the valve port 171 is H2The vertical distance from the sealing line of the valve port 171 to the shoulder at the upper end of the valve seat 17 is H3The vertical distance from the bottom surface of the connecting seat 18 to the upper end surface of the second limiting part 181 is H4The height of the first position-limiting portion 103 is H5At the moment, the coincidence height of the limiting mechanism in the vertical direction is H6From the movement of the first position-limiting part 103, the vertical distance corresponding to the dead zone angle α is α × L/360, and then H is6=H1-α*L/360=L/2-α*L/360=(180-α)*L/360。
Correspondingly, as shown in fig. 6, the inside of the copying tool 28 is provided with an inner through hole and a valve port which have the same shape and size as the inner through hole 163 of the screw 16 and the valve port 171 of the valve seat 17 and are used for accommodating and limiting the valve core 12, and the inner through hole and the valve port of the copying tool 28 are coaxial(ii) a The vertical distance from the upper end surface of the profiling tool 28 to the valve port sealing line is H2=H3+H4+H5-H6=H3+H4+H5-(180-α)*L/360。
Inserting the first combined valve core 12 into the through hole in the profiling tool 28, so that the valve core 12 reaches the theoretical position when the valve port 171 is just closed by the flow regulating section 123, applying a proper pressing force F to the connecting sleeve 14, forcing the nut 10 and the rotor 11 to move downwards, and the lower end surface of the internal thread part 102 of the nut 10 abuts against the upper end surface of the profiling tool 28; at the moment, the first assembled body is obtained by laser welding the connecting section 121 of the connecting sleeve 14 and the valve core 12, the connecting plate 111 of the rotor 11 and the guiding part 101 of the nut 10; thereby eliminating the vertical dimension on the valve core 12, the thickness of 2 washers and the vertical dimension on the connecting sleeve 14 versus the contact height H1Significantly shortening the dimensional chain and thereby improving the assembly yield of the product.
(1.2) the assembling method for determining the assembling position by comparing the numerical relationship between the rotating torque values of the first assembling body and the connecting seat 18 and the set threshold value solves the assembling problem of the dead zone angle α. the conventional assembling method can cause poor consistency of products or even can not close valves due to the long dimension chain influencing the dead zone angle α. the method can arbitrarily control the size of the dead zone angle α, has very good consistency, and comprises the following specific steps:
(1.2.1) fixing the valve seat 17 in the second assembly, sleeving the connecting seat 18 on the second assembly, and screwing the first assembly assembled in the step (1.1) into the second assembly at a constant speed clockwise (the screw thread of the screw mechanism in the embodiment is right-handed) under the action of a small axial force, wherein at the moment, the flow regulating section 123 of the valve core 12 continuously approaches and finally closes the valve port 171 of the valve seat 17. Fig. 7 is a graph illustrating a rotation moment of the first assembly as a function of a rotation angle during the assembly of the first assembly. Before the valve port 171 is completely closed, since the acting force between the friction pairs (the internal thread portion 102 and the external thread 161) of the first combination body and the second combination body is small, the detected rotation torque of the first combination body is also small and smaller than the set first judgment threshold; after the valve port 171 is completely closed, the elastic force of the connecting spring 13The force between the friction pairs is increased, the detected rotation moment of the first combination body is increased and is larger than a set first judgment threshold but smaller than a set second judgment threshold, after the valve port 171 is closed (namely the rotation moment curve of the first combination body is crossed with the first judgment threshold), the first combination body continues to rotate clockwise at a constant speed until the first combination body stops rotating at a dead zone angle α, at the moment, the position of the first combination body is determined, and the superposition height of the limiting mechanism in the vertical direction is H1But contact has not necessarily occurred. In this embodiment, the first determination threshold is 10N · mm, and the second determination threshold is 30N · mm.
During the assembly of step (1.2.1), the following three cases may occur: firstly, before the first assembly rotates to the set position, the first assembly is in side contact with the connecting seat 18 and drives the connecting seat 18 to rotate together, and as the connecting seat 18 can rotate around the second assembly, the detected rotating moment of the first assembly is basically not influenced; before the first assembly rotates to the set position, the first assembly is not in contact with the connecting seat 18, and the detected rotating moment of the first assembly is not influenced; thirdly, before the first combination body is rotated to the set position, the first limiting part 103 and the second limiting part 181 have certain probability of end surface contact (the lower end surface of the first limiting part 103 contacts the upper end surface of the second limiting part 181) due to the width of the first limiting part 103 and the second limiting part 181, and the detected rotation moment of the first combination body is suddenly increased and is larger than the set second judgment threshold, and the solution at this time is as follows: stopping rotating the first combination body, then rotating the first combination body half-circle anticlockwise to enable the first combination body half-circle and the first combination body half-circle to be separated, then rotating the connecting seat 18 half-circle clockwise, and finally repeating the assembling process in the step (1.2.1).
(1.2.2) simultaneously fixing the valve seat 17 of the second assembly and the rotor 11 of the first assembly, and rotating the connecting seat 18 which is arranged on the shaft shoulder at the upper end of the valve seat 17 at a constant speed anticlockwise under the action of a small axial force; fig. 8 is a schematic view of a curve of the rotation torque of the connection seat 18 changing with the rotation angle during the assembly process of the connection seat 18, when the second limiting portion 181 contacts the first limiting portion 103, the detected rotation torque of the connection seat 18 may suddenly increase and be greater than a set second determination threshold, at this time, the connection seat 18 stops rotating, the position of the connection seat 18 is determined, the lower end surface of the connection seat 18 is welded to the shoulder at the upper end of the valve seat 17 by laser, and the connection seat 18 and the second assembly are fixed together.
(2) After the first combination body, the second combination body and the connecting base 18 are assembled together, an upper stop spring 20 and a spring seat 21 are arranged on a connecting sleeve 14 of the first combination body, then a sleeve 19 with one closed end and one open end is sleeved on the connecting sleeve, the stop spring 20 is in a compressed state, the upper end of the spring seat 21 props against the closed end of the sleeve 19, and finally the open end of the sleeve 19 and a shaft shoulder of the connecting base 18 are hermetically connected in a laser welding mode.
(3) Arranging a first O-ring 24 in the main cavity 231 of the valve body 23, sleeving a second O-ring 25 on an annular groove at the lower end of the valve seat 17, sleeving a locking nut 22 on the flange part 182 of the connecting seat 18, inserting the assembled components in the steps (1) to (2) into the main cavity 231 of the valve body 23, and screwing the locking nut 22 downwards to press the connecting seat 18 in the main cavity 231 of the valve body 23; the first O-ring 24 is located between the flange portion 182 and the main chamber 231, the second O-ring 25 is located between the valve seat 17 and the main chamber 231, and both the first O-ring 24 and the second O-ring 25 are rubber rings for sealing.
(4) The stator 26 is arranged outside the sleeve 19 and fixed to the valve body 23, and the circuit board 27 is fixed to the stator 26 and electrically connected.