Motor-operated valve

Abstract

To provide a motor-operated valve capable of minimizing valve leakage while simplifying a stopper structure in a closing direction of a valve body.SOLUTION: A motor-operated valve comprises a restriction structure that restricts rotation of an operation member 32 with respect to a rotor 60. A screw feeding mechanism 109 is implemented by a first screw 108 provided on a guide member 36 and a second screw 38 provided on the operation member 32. A predetermined radial clearance CL is defined between the first screw 108 and the second screw 38. When a valve body 34 operates in a valve-closing direction, the valve body 34 is rotatable within a predetermined allowable range while remaining in a seated state from a seating point at which the valve body comes into contact with the valve seat 24. The screw feeding mechanism 109 is locked by rotation within the allowable range, and thereby it is stopped at an operational origin. The clearance CL is set to be greater than a tolerance defined as a concentricity between the valve body 34 and the valve seat 24.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a motor-operated valve, and more particularly to a leak-proof structure for a valve portion. [Background technology]

[0002] Automotive air conditioning systems generally consist of a refrigeration cycle that includes a compressor, an external heat exchanger, an expansion device, an evaporator, and other components. The refrigeration cycle includes various control valves, such as an expansion valve, to control the flow of refrigerant. With the recent popularity of electric vehicles, motor-operated valves equipped with a motor as a drive unit have become widely used.

[0003] In this type of motor-operated valve, an actuating rod is connected to the rotor of the motor, and a valve element is provided at the tip of the actuating rod (see Patent Document 1). A screw feed mechanism converts the rotational motion of the rotor into translational motion of the actuating rod, thereby driving the valve element in the opening and closing directions of the valve section. A reference position that serves as the control reference is set on the actuating rod. When the rotor continues to rotate in the valve closing direction and reaches the reference position, also known as the "origin," the rotor's rotation is restricted by a stopper.

[0004] When such a configuration is adopted, parts and mechanisms are required to function as a stopper, which increases manufacturing costs. Therefore, a configuration has been proposed in which the actuating rod is fixed to the rotor and the valve disc is seated on the valve seat to restrict rotor rotation (see Patent Document 2). With this configuration, the valve seat functions as the stopper, so there is no need to provide a separate stopper mechanism. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-204344 [Patent Document 2] International Publication No. 2023 / 203967 Summary of the Invention [Problem to be solved by the invention]

[0006] However, such motor-operated valves do not take into consideration axial misalignment between the valve disc and the valve seat. That is, if the axis of the valve disc and the axis of the valve seat do not coincide due to machining errors, assembly errors, etc. (so-called "axial misalignment"), a gap may form in the valve portion even when the valve disc is seated on the valve seat. This means that the valve portion cannot be closed securely, and refrigerant may leak from the valve portion when the valve is closed (hereinafter also referred to as "valve leakage").

[0007] One object of the present invention is to provide an electrically operated valve that can minimize valve leakage while simplifying the stopper structure for the valve body in the valve closing direction. [Means for solving the problem]

[0008] One embodiment of the motor-operated valve of the present invention includes a body having a first port, a second port, a valve hole provided in a passage connecting the first port and the second port, and a valve seat provided at the open end of the valve hole; a valve element that is detachably attached to the valve seat to open and close a valve portion; a motor including a rotor for driving the valve element in the opening and closing directions of the valve portion; an actuating member that is coaxially connected to the rotor and integral with the valve element; a screw feed mechanism that converts rotational motion of the rotor into translational motion of the actuating member; a guide member that is integral with the body; and a restricting structure that restricts rotation of the actuating member relative to the rotor. The screw feed mechanism is realized by a first screw provided on the guide member and a second screw provided on the actuating member. A predetermined radial clearance is set between the first screw and the second screw. When the valve element operates in the valve closing direction, it can rotate within a certain allowable range from a seating point where it sits on the valve seat while maintaining its seated state. Rotation within the allowable range locks the screw feed mechanism, causing it to stop at the actuating origin. The clearance is set to be larger than the tolerance set for the concentricity between the valve disc and the valve seat.

[0009] According to this aspect, the actuating member provided with the valve disc is connected to the rotor via a rotation restriction structure, so that the rotor's rotation can be restricted by the valve disc seating on the valve seat. Therefore, there is no need to provide a separate stopper mechanism for valve closing operation. Meanwhile, the first screw of the guide member and the second screw of the actuating member form a screw feed mechanism, and the radial clearance between the first screw and the second screw is set larger than the tolerance set for the concentricity between the valve disc and the valve seat. Therefore, even if there is axial misalignment within the tolerance range when the valve disc operates in the valve closing direction, the axial misalignment can be absorbed as the valve disc rotates from the seating point to the actuation origin. This makes it possible to prevent or minimize valve leakage. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an electrically operated valve that can minimize valve leakage while simplifying the stopper structure for the valve body in the valve closing direction. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view illustrating a motor-operated valve according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing the structure of a valve unit. [Figure 3] 10A and 10B are diagrams illustrating a valve leakage prevention structure and a valve closing operation of a valve portion. [Figure 4] 10A and 10B are diagrams illustrating a valve leakage prevention structure and a valve closing operation of a valve portion. [Figure 5] 10A and 10B are diagrams illustrating an example of torque reduction control during valve closing operation. [Figure 6] FIG. 2 is a diagram illustrating basic characteristics of a stepping motor. [Figure 7] 10 is a timing chart showing torque reduction control according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. For convenience, the following description may refer to the positional relationship of each structure based on the illustrated state. In the following embodiments and their modifications, substantially identical components will be designated by the same reference numerals, and their description will be omitted where appropriate.

[0013] FIG. 1 is a cross-sectional view showing a motor-operated valve according to an embodiment. The motor-operated valve 1 is applied to the refrigeration cycle of an automotive air conditioner (not shown). The refrigeration cycle is equipped with a compressor, an external heat exchanger, an expansion valve, an evaporator, etc., and the refrigerant circulation passage is switched depending on the operating state of the air conditioner. The high-temperature, high-pressure refrigerant compressed by the compressor is cooled by passing through the external heat exchanger. The refrigerant then adiabatically expands as it passes through the expansion valve, becoming low-temperature and low-pressure, and is then guided to the evaporator where it evaporates. The air inside the vehicle cabin is cooled by the latent heat of evaporation. The motor-operated valve 1 functions as this expansion valve.

[0014] In this embodiment, a condenser is provided as an external heat exchanger because a condensable refrigerant such as HFO-1234yf is used. However, if carbon dioxide, which has a high operating pressure, is used as the refrigerant, a gas cooler is provided instead of the condenser.

[0015] The motor-operated valve 1 is configured by assembling a valve unit 100 and a passage body 200. The valve unit 100 includes a rotor unit 90 and a stator unit 92. The rotor unit 90 and the stator unit 92 are each fixed to the passage body 200. The stator unit 92 is fixed to the passage body 200 via a connecting member 101. The connecting member 101 includes a metal plate fixed to the stator unit 92 and a screw for fixing the metal plate to the passage body 200.

[0016] The passage body 200 is made of a metal such as an aluminum alloy and has a generally rectangular prism shape. An inlet port 202, an outlet port 204, an inlet port 206, and an outlet port 208 are provided on the side of the passage body 200. A pipe extending from the condenser side is connected to the inlet port 202, and a pipe leading to the inlet of the evaporator is connected to the outlet port 204. A pipe leading to the outlet of the evaporator is connected to the inlet port 206, and a pipe extending to the compressor side is connected to the outlet port 208.

[0017] The passage body 200 is formed with a first passage 210 connecting the inlet port 202 and the outlet port 204, and a second passage 212 connecting the inlet port 206 and the outlet port 208. The first passage 210 and the second passage 212 are separated vertically by a partition wall 214. An attachment hole 216 opens upward at the top of the passage body 200. The attachment hole 216 communicates with the first passage 210. A female thread portion 218 is formed near the open end of the attachment hole 216.

[0018] The valve unit 100 has a valve body 5 that houses a valve portion. A seal ring 20 (O-ring) is attached to the outer peripheral surface of the lower end of the valve body 5. A male thread portion 10 that can be threaded into a female thread portion 218 is formed on the outer peripheral surface of the upper part of the valve body 5. When assembling the valve unit 100 to the passage body 200, the valve body 5 is inserted into the mounting hole 216. The male thread portion 10 is threadedly engaged with the female thread portion 218, and the valve body 5 is fastened to the passage body 200. The valve body 5 and the passage body 200 can also be collectively interpreted as "the body of the motor-operated valve 1."

[0019] An annular seal receiving portion 222 (annular groove) is provided on the upper surface of the passage body 200 so as to surround the mounting hole 216, and a seal ring 220 (O-ring) is fitted into the annular groove. When the valve body 5 is fastened to the passage body 200, the seal ring 220 is interposed between the upper surface of the passage body 200 and the valve body 5. The seal ring 220 prevents refrigerant from leaking from the inside of the passage body 200 to the outside. The seal ring 220 seals between an upstream passage 230 and a downstream passage 232 of the valve portion.

[0020] FIG. 2 is a cross-sectional view showing the structure of the valve unit 100. As shown in FIG. The valve unit 100 is configured by coaxially assembling a rotor unit 90 and a stator unit 92. The rotor unit 90 and the stator unit 92 are not directly fixed to each other, but are indirectly fixed to each other by being fixed to a passage body 200 (see FIG. 1).

[0021] The rotor unit 90 has a valve body 5. The valve body 5 includes a valve housing 6 and a valve seat member 8. The valve housing 6 has a large diameter portion 7 and a small diameter portion 9 integrally formed therewith, and is shaped like a stepped cylinder whose outer diameter decreases downward. A male thread portion 10 is formed on the outer peripheral surface of the small diameter portion 9.

[0022] The valve housing 6 is obtained by cutting a material made of stainless steel (hereinafter referred to as "SUS"). As shown in Figure 1, when the small diameter portion 9 is threaded into the mounting hole 216, the large diameter portion 7 abuts against the passage body 200 in the axial direction, thereby restricting the insertion amount of the valve body 5 into the mounting hole 216.

[0023] A valve seat member 8 is coaxially assembled to the lower opening of the valve housing 6. The valve seat member 8 is cylindrical, with its upper portion press-fitted and fixed into the small diameter portion 9. To increase the fixing force, the lower opening of the small diameter portion 9 may be crimped inward. An inlet port 26 is provided on the side surface of the axial center of the valve seat member 8. A seal ring 20 is fitted onto the outer peripheral surface of the lower part of the valve seat member 8.

[0024] The inner diameter of the lower part of the valve seat member 8 is reduced to form a valve hole 22, and a valve seat 24 is formed at the upper opening of the valve hole 22. In this embodiment, the valve seat member 8 is made of stainless steel, but a material with excellent wear resistance, such as brass, may also be selected. In other words, the valve housing 6 may be made of a material that is more weldable than the valve seat member 8, and the valve seat member 8 may be made of a material that is more machinable than the valve body 5.

[0025] An outlet port 28 is provided at the bottom of the valve seat member 8. The inlet port 26 communicates with the introduction port 202, and the outlet port 28 communicates with the discharge port 204 (see FIG. 1). An internal passage that communicates the inlet port 26 and the outlet port 28 is formed inside the valve body 5. A valve chamber 30 is formed inside the valve seat member 8. The inlet port 26 and the outlet port 28 communicate with each other via the valve chamber 30. In this embodiment, the inlet port 26 corresponds to the "first port," and the outlet port 28 corresponds to the "second port."

[0026] An actuating rod 32 extending from the rotor 60 of the rotor unit 90 is inserted into the interior of the valve body 5. The actuating rod 32 passes through the valve chamber 30. The actuating rod 32 is obtained by cutting a rod made of a non-magnetic metal, and a needle-shaped valve element 34 is integrally provided at the bottom. The actuating rod 32 functions as an "actuating member." The valve element 34 is attached to and detached from the valve seat 24 from the valve chamber 30 side to open and close the valve portion.

[0027] A guide member 36 is erected inside the large-diameter portion 7 of the valve housing 6. That is, the guide member 36 is provided integrally with the valve body 5. The guide member 36 is obtained by cutting a tube made of a non-magnetic metal (brass in this embodiment) into a stepped cylindrical shape. The lower end of the guide member 36 has a large diameter, and its large-diameter portion 40 is press-fitted into the large-diameter portion 7 of the valve housing 6 and fixed coaxially. A female thread 108 is provided on the upper inner peripheral surface of the guide member 36 to support the operating rod 32 so that it can rotate and slide. A spring 37 (functioning as a "biasing member") is interposed between the operating rod 32 and the guide member 36 to bias the valve disc 34 in the valve-closing direction.

[0028] The actuation rod 32 is a stepped cylindrical member, and an external thread 38 is formed on the outer peripheral surface of its upper half, which meshes with an internal thread 108 of the guide member 36. In this embodiment, the internal thread 108 functions as a "first screw," and the external thread 38 functions as a "second screw." A screw feed mechanism 109 using these screws converts the rotational motion of the rotor 60 into translational motion (axial motion) of the actuation rod 32. This causes the valve element 34 to move (raise and lower) in the axial direction, i.e., in the opening and closing direction of the valve portion.

[0029] Meanwhile, the rotor 60 of the rotor unit 90 and the stator 64 of the stator unit 92 constitute a two-phase stepping motor. The rotor unit 90 has a cylindrical can 66 with a bottom, and the rotor 60 is disposed inside the can 66. The stator 64 is disposed outside the can 66. The can 66 is a cylindrical member with a bottom that covers the space in which the valve body 34 and its drive mechanism are disposed and that contains the rotor 60, and defines an inner pressure space (internal space) where the pressure of the refrigerant acts and an outer non-pressure space (external space) where the pressure of the refrigerant does not act.

[0030] The can 66 is made of a non-magnetic metal (e.g., stainless steel), and its lower end is fitted onto the upper end of the valve housing 6. The valve body 5 and the can 66 are fixed together by welding (full-circumference welding) along the boundary between the can 66 and the valve housing 6 (not shown), ensuring airtightness (sealing) between them. The space surrounded by the valve body 5 and the can 66 forms the above-mentioned pressurized space.

[0031] The stator 64 is constructed by assembling a bobbin 70, around which a coil 68 is wound, to a yoke 72 having a plurality of pole teeth. The stator 64 is housed in a case 76. The case 76 is obtained by injection molding (also called "insert molding" or "mold molding") of a corrosion-resistant resin material. The stator 64 is covered with the molded resin produced by the injection molding. The case 76 is made of the molded resin. The stator unit 92 is an integrated part (a molded product in this embodiment) of the stator 64 and the case 76.

[0032] The stator unit 92 has a hollow structure, and is assembled to the rotor unit 90 with the stator 64 coaxially inserted through the can 66. The welded portion between the can 66 and the valve body 5 is located inside the case 76. A seal ring 44 (O-ring) is fitted onto the outer peripheral surface of the upper part of the valve body 5. The seal ring 44 is interposed between the valve body 5 and the case 76, preventing the external atmosphere (such as water) from entering the gap between the can 66 and the stator 64.

[0033] The rotor 60 includes a stepped cylindrical rotor core 102, a rotor magnet 104 provided on the outer peripheral surface of the rotor core 102, and a sensor magnet 106 provided on the upper end surface of the rotor core 102. The rotor magnet 104 is cylindrical, and its upper end is fixed so as to fit into the outer peripheral surface of the rotor core 102. With this configuration, a relatively large annular space S is formed between the inner peripheral surface of the rotor magnet 104 and the outer peripheral surface of the operating rod 32.

[0034] The sensor magnet 106 has an annular shape and is coaxially attached to the rotor core 102. The rotor magnet 104 is magnetized (magnetized) with multiple poles in its circumferential direction. The sensor magnet 106 is also magnetized (magnetized) with multiple poles.

[0035] A reduced diameter portion 110 is provided at the top of the actuation rod 32 and is press-fitted along the axis of the rotor core 102. This causes the actuation rod 32 and the rotor 60 to be coaxially fixed. This structure in which the actuation rod 32 is integrally provided with the rotor 60 functions as a "restriction structure" that restricts the rotation of the actuation rod 32 relative to the rotor 60. The actuation rod 32 functions as the rotation axis of the rotor 60.

[0036] The stator unit 92 has a circuit board 118 on the outside of the can 66. The circuit board 118 is fixed inside the case 76. Various circuits that function as a control unit and a communication unit are mounted on the underside of the circuit board 118. Specifically, a drive circuit for driving the motor, a control circuit (microcomputer) that outputs control signals to the drive circuit, a communication circuit for the control circuit to communicate with an external device, a power supply circuit for supplying power to each circuit and the motor (coil), etc. are mounted on the circuit board 118. The upper end of the case 76 is closed by a resin lid 77. The circuit board 118 is disposed in the space below the lid 77 of the case 76.

[0037] A magnetic sensor 119 is provided on the surface of the circuit board 118 facing the sensor magnet 106. The magnetic sensor 119 faces the sensor magnet 106 in the axial direction via the bottom end wall of the can 66. The magnetic flux generated by the sensor magnet 106 changes as the rotor 60 rotates. The magnetic sensor 119 detects the amount of displacement of the rotor 60 (the rotation angle of the rotor 60 in this embodiment) by detecting this change in magnetic flux. The control unit calculates the axial position of the valve disc 34, and therefore the valve opening, based on the amount of displacement of the rotor 60.

[0038] Terminals 120 connected to coil 68 extend from bobbin 70 and are connected to circuit board 118. A power terminal, a ground terminal, and a communication terminal (collectively referred to as "connection terminals 122") extend from circuit board 118 and are each drawn out to the outside through the side wall of case 76. A connector section 124 is integrally provided on the side of case 76, and connection terminals 122 are arranged inside connector section 124.

[0039] 1, when assembling the motor-operated valve 1, the passage body 200, the rotor unit 90, and the stator unit 92 are each produced separately. Then, the rotor unit 90 and the stator unit 92 are each fixed to the passage body 200.

[0040] First, the seal ring 220 is fitted into the seal accommodating portion 222 of the passage body 200. The seal ring 20 is fitted into the rotor unit 90. Next, the rotor unit 90 is inserted into the mounting hole 216 from the tip side of the valve body 5. At this time, the male thread portion 10 is threaded into the female thread portion 218, and the rotor unit 90 is assembled to the passage body 200 while being rotated.

[0041] By fastening the rotor unit 90 to the passage body 200, the seal ring 220 is appropriately crushed, and the sealing function is effectively exhibited. The sealing function of the seal ring 20 is also effectively exhibited. Then, the stator unit 92 is assembled to the rotor unit 90 while being coaxially inserted around the can 66. Prior to this assembly, the metal plate of the connecting member 101 is fixed to the case 76 of the stator unit 92 by welding or the like.

[0042] The metal plate is fastened to the passage body 200 by screws (not shown), thereby fixing the stator unit 92 to the passage body 200. As a result, the rotor unit 90 and the stator unit 92 are also indirectly fixed.

[0043] The motor-operated valve 1 configured as described above functions as an electric expansion valve whose valve opening can be adjusted by controlling the drive of the rotor unit 90. That is, based on commands from an external device (not shown), the control unit sets a control amount (number of motor drive steps) for achieving a target opening and outputs a drive signal to the drive circuit to achieve this. The drive circuit supplies two-phase drive currents (drive pulses) to each coil 68 at a set timing. This causes the rotor 60 to rotate with high resolution. At this time, the actuating rod 32, and therefore the valve element 34, move integrally with the rotor 60.

[0044] The rotor 60 moves up and down by a screw feed mechanism 109 between the actuation rod 32 and the guide member 36. The valve element 34 moves in a translational manner in the opening and closing direction of the valve section, and the opening degree of the valve section is adjusted to a set opening degree. The screw feed mechanism 109 converts the rotational movement of the rotor 60 around its axis into axial movement (linear movement) of the actuation rod 32, and drives the valve element 34 in the opening and closing direction of the valve section. When the motor-operated valve 1 functions as an expansion valve, the valve section is controlled to a small opening degree. The control unit detects the rotational angle of the sensor magnet 106 (the rotational angle of the rotor 60) based on the detection signal of the magnetic sensor 119, and can calculate the valve opening degree.

[0045] Figures 3 and 4 are diagrams showing the valve leakage prevention structure and the valve closing operation of the valve section. Figures 3(A) to (C) show the valve closing operation process when there is no axial misalignment. Figures 4(A) and (B) show the valve closing operation process when there is axial misalignment. The upper part of each figure corresponds to an enlargement of part A in Figure 2 (enlargement of the screw section of the screw feed mechanism), and the lower part corresponds to an enlargement of part B (enlargement of the valve section).

[0046] When the motor-operated valve 1 is operated to close, the rotation of the rotor 60 activates the screw feed mechanism 109, and the valve element 34 is displaced downward while rotating integrally with the operating rod 32 (FIG. 3(A)). Between the male screw 38 and the female screw 108 that constitute the screw feed mechanism 109, a radial clearance CL (= CL1 + CL2: first clearance) and an axial clearance CL3 (second clearance) are set.

[0047] At this time, even when the valve disc 34 is seated on the valve seat 24, it maintains its seated state and rotates within a certain allowable range ( FIG. 3(B) ). The rotation within this allowable range causes the screw feed mechanism 109 to lock, stopping the valve disc 34 ( FIG. 3(C) ). This "allowable range" varies depending on the axial clearance CL3. In this embodiment, the male thread 38 and the female thread 108 are metric threads (threads with inclined threads). Therefore, if the radial clearance CL increases, the inclined threads of both threads will move away from each other, and the axial clearance CL3 will also increase. Therefore, the "allowable range" in this embodiment depends on the radial clearance CL. Here, the position where the valve disc 34 is seated on the valve seat 24 is referred to as the "seating point," and the position where the screw feed mechanism 109 locks and stops the rotation of the valve disc 34 is referred to as the "operation origin."

[0048] When there is no axial misalignment between the valve disc 34 and the valve seat 24, at the operating origin, the first surface 108a of the female thread 108 facing the valve seat 24 and the second surface 38b of the male thread 38 facing the opposite side from the valve seat 24 are in contact over the entire circumference. Meanwhile, a clearance CL3 is formed between the third surface 108b of the female thread 108 facing the opposite side from the valve seat 24 and the fourth surface 38a of the male thread 38 facing the valve seat 24.

[0049] On the other hand, if there is an axial misalignment between the valve body 34 and the valve seat 24 (Figure 4(A)), depending on the magnitude of the misalignment, it is possible that at the operating origin, the first surface 108a of the female thread 108 and the second surface 38b of the male thread 38 will not abut over the entire circumference, resulting in so-called partial contact (Figure 4(B)).

[0050] However, in this embodiment, as described below, the clearance CL between the male thread 38 and the female thread 108 is set larger than the tolerance set for the concentricity between the valve disc 34 and the valve seat 24. This allows the actuation rod 32 to self-align from the time the valve disc 34 seats on the valve seat 24 at the seating point until it reaches the actuation origin, thereby preventing valve leakage. This tolerance includes the sum of the processing tolerance and assembly tolerance.

[0051] Specifically, referring to FIG. 2, the tolerance for concentricity between the valve disc 34 and the male thread 38 in the operating rod 32, the tolerance for concentricity between the female thread 108 and the large diameter portion 40 in the guide member 36, the tolerance for concentricity between the fitting portion of the valve housing 6 with the guide member 36 and the fitting portion of the valve seat member 8, and the tolerance for concentricity between the fitting portion of the valve seat member 8 with the valve housing 6 and the valve seat 34 are taken into consideration, and the tolerance for concentricity between the fitting portion of the valve seat member 8 with the valve housing 6 and the valve seat 34 is set as the sum of these.

[0052] Additionally, as an assembly tolerance, the tolerance of concentricity between the guide member 36 and the valve housing 6 and the tolerance of concentricity between the valve housing 6 and the valve seat member 8 are taken into consideration, and the tolerance of concentricity between the valve disc 34 and the valve seat 24 is set as the sum of these. The tolerance of concentricity between the valve disc 34 and the valve seat 24 is set by combining these processing tolerances and assembly tolerances. The clearance CL is set larger than this tolerance.

[0053] In other words, the tolerance set for the concentricity between the valve disc 34 and the valve seat 24 includes the sum of the machining tolerances and assembly tolerances between multiple components that affect the concentricity between the valve disc 34 and the valve seat 24. In this embodiment, the "multiple components" include the actuating rod 32, the guide member 36, the valve housing 6, and the valve seat member 8. The clearance CL is set larger than this tolerance. With this configuration, even if the concentricity between the valve disc 34 and the valve seat 24 deviates within this tolerance range, the actuating rod 32 can autonomously align itself, thereby preventing or suppressing valve leakage.

[0054] Next, the torque reduction control executed during the valve closing operation will be described. In this embodiment, as described above, the actuation rod 32 is fixed to the rotor 60. Therefore, the thrust force in the axial direction by the screw feed mechanism 109 is transmitted directly to the valve element 34 via the actuation rod 32. If this thrust force is excessive, there is a risk that the valve element 34 will bite into the valve seat 24 when the valve is closed (when the screw feed mechanism 109 is locked), wear on the valve seat 24, or the threads of the screw feed mechanism 109 will become stuck.

[0055] Therefore, the occurrence of the above-mentioned problems is suppressed by reducing the driving torque of the stepping motor (also simply referred to as "motor") from a predetermined timing when the valve element 34 is closed.

[0056] FIG. 5 shows an example of torque reduction control during valve closing. FIG. 5(A) is a timing chart showing torque reduction control, and FIG. 5(B) is an enlarged view of part A in FIG. 5(A). The horizontal axis in the figure shows the passage of time from when the valve starts to open until it closes. The vertical axis shows the drive steps from the operation origin (solid line), the flow rate of refrigerant flowing through the valve (chain double-dashed line), the current value supplied to the motor (current magnitude: dotted line), and the drive frequency (pulse frequency: dashed line). FIG. 6 shows the basic characteristics of a stepping motor (the relationship between rotor rotation speed and drive torque). The horizontal axis in the figure shows rotation speed, and the vertical axis shows drive torque.

[0057] As shown in Figure 5(A), the control unit controls the drive of the motor based on this actuation origin, controlling the position of the valve element 34 (i.e., the valve opening). The control unit pre-stores the motor drive steps from the actuation origin to the seating point, and sequentially stores and updates the current drive steps when controlling the motor. In particular, when the valve element 34 is operating to close, the motor drive torque is reduced when the drive steps reach a predetermined torque switching step. Torque reduction is achieved by lowering the supply current value and increasing the drive frequency. Increasing the motor drive frequency increases the rotational speed, thereby reducing torque.

[0058] It is known that stepping motors generally have a basic characteristic between rotor rotation speed and drive torque, as shown in Figure 6. When the rotor rotation speed is increased, the torque reaches a peak (maximum torque Tp) at a certain rotation speed, and as the rotation speed is further increased, the drive torque gradually decreases.

[0059] In this embodiment, with regard to the control of the motor-operated valve 1, a rotational speed range in which a drive torque at or near the maximum torque Tp is obtained is set as the "normal control region." Then, when the motor-operated valve 1 operates to open, the drive frequency of the motor is set so that a rotational speed within this normal control region is obtained. In other words, by changing the rotational speed to be higher or lower than that within the normal control region, the motor-operated valve 1 can be operated in the valve closing direction while reducing the motor drive torque to be lower than that in the normal control state. In this embodiment, by increasing the motor drive frequency when the drive step reaches the torque switching step, the rotor rotational speed is increased above that of the normal control region, thereby achieving the aforementioned torque reduction.

[0060] As shown in Figure 5(B), in this embodiment, the torque switching step is set to a point a predetermined number of steps before the reference step corresponding to the seating point in the valve closing direction. This reduces the torque almost simultaneously when the valve element 34 begins to seat on the valve seat 24. This reduces the surface pressure generated between the valve element 34 and the valve seat 24 after seating.

[0061] The control unit calculates the axial position of the valve body 34 and therefore the valve opening degree based on the displacement of the rotor 60 detected by the magnetic sensor 119, and outputs a control command in the form of the number of steps (driving steps) from the operating origin when controlling the valve opening degree.

[0062] 2, in this embodiment, a spring 37 is provided to bias the valve element 34 in the valve closing direction, and a differential pressure in the valve closing direction also acts on the valve element 34, so a relatively high torque is required for the valve opening operation, but a relatively low torque is sufficient for the valve closing operation. Therefore, even if such a torque reduction is performed during the valve closing operation, it does not impede the valve closing operation.

[0063] As described above, in this embodiment, the actuation rod 32 provided with the valve disc 34 is connected to the rotor 60 via a rotation restriction structure. Therefore, the valve disc 34 is seated on the valve seat 24, thereby restricting rotation of the rotor 60. Therefore, a separate stopper mechanism is not required for valve-closing operation. Meanwhile, the radial clearance CL between the internal thread 108 of the guide member 36 and the external thread 38 of the actuation rod 32 is set larger than the tolerance set for the concentricity between the valve disc 34 and the valve seat 24. Therefore, even if the valve disc 34 experiences axial misalignment within the tolerance range when operating in the valve-closing direction, the axial misalignment can be absorbed as the valve disc 34 rotates from the seating point to the actuation origin. This prevents or minimizes valve leakage.

[0064] Although the preferred embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to this specific embodiment, and various modifications are possible within the scope of the technical concept of the present invention.

[0065] [Variations] FIG. 7 is a timing chart showing torque reduction control according to a modified example. In this modification, torque reduction control is executed at the timing when the operation of the valve element 34 switches from a valve-opening operation to a valve-closing operation. In this way, as in the above embodiment, it is possible to prevent or suppress the valve element 34 from biting into the valve seat 24 when the valve is closed, wear on the valve seat 24, and jamming of the screws in the screw feed mechanism 109.

[0066] However, in this modified example, the rate of change in flow rate changes between when the valve is opened and when it is closed, and this must be taken into consideration when controlling the flow rate in the open state. In other words, in the above embodiment, the rate of change in flow rate can be kept almost constant between when the valve is opened and when it is closed (see FIG. 5), which has the advantage of making flow rate control easier.

[0067] In another modification, the torque reduction control may be executed at a predetermined timing after the operation of the valve element 34 switches from the valve-opening operation to the valve-closing operation. For example, the torque reduction control may be executed at or around the timing when the change in the flow rate becomes small as shown in FIG. 5(A).

[0068] [Other variations] In the above embodiment, the operating member and the rotor are fixed by press-fitting. In a modified example, they may be fastened by a screw structure. Alternatively, they may be fixed by welding or the like.

[0069] In the above embodiment, a configuration has been exemplified in which the actuation rod 32 functions as the rotation shaft of the rotor 60. In a modified example, as described in, for example, JP 2020-204344 A (Patent Document 1), a rotation shaft (cylindrical shaft) made of a non-magnetic metal may be provided inside the rotor, and the rotation shaft and the actuation rod may be fixed together. A screw feed mechanism may be configured between the rotation shaft and the guide member. Specifically, a male thread (first thread) is formed on the outer peripheral surface of the guide member, and a female thread (second thread) is formed on the inner peripheral surface of the rotation shaft. The inner peripheral surface of the guide member does not have a female thread, and the actuation rod is inserted therethrough so as to be slidable in the axial direction.

[0070] With this configuration, the first screw of the guide member and the second screw of the rotary shaft form a screw feed mechanism. When the rotor is driven, the rotary shaft and the actuation rod rotate together and are displaced in the axial direction. The configurations of the above embodiments can also be applied to this configuration. In this case, the rotary shaft and the actuation rod form the "actuation member."

[0071] In the above embodiment, metric threads with inclined threads are used as the first and second threads that make up the screw feed mechanism. In a modified example, trapezoidal threads with inclined threads may also be used. In this case, the allowable range within which the valve disc can rotate while remaining seated also depends on the radial clearance between the first and second screws. Therefore, by setting the radial clearance to be larger than the tolerance set for the concentricity between the valve disc and the valve seat, the same effect as in the above embodiment can be achieved.

[0072] Alternatively, a square thread with no beveled thread may be used. When a square thread is used, even if the radial clearance increases, the axial clearance does not change. Therefore, the allowable range within which the valve disc can rotate while remaining seated does not necessarily correspond to the radial clearance between the first and second threads. However, by setting the radial clearance to be larger than the tolerance established for the concentricity between the valve disc and the valve seat, it is possible to promote autonomous alignment of the actuating rod 32 and minimize valve leakage.

[0073] In the above embodiment, torque reduction control is achieved by reducing the supply current value and increasing the drive frequency, as shown in Fig. 5 etc. In a modified example, torque reduction control may be achieved by reducing the supply current value and, conversely, lowering the drive frequency. That is, by lowering the drive frequency of the motor to make the rotor rotation speed lower than in the normal control region, the drive torque of the motor may be reduced below that in the normal control state when the valve is open.

[0074] In another modification, torque reduction control may be achieved by switching the excitation method of the stepping motor. For example, torque may be reduced by using half-step drive (1-2 phase excitation) during normal control such as when opening the valve, and micro-step drive (W1-2 phase excitation) during torque reduction control. Note that half-step drive is a drive method that rotates the motor at half the original step angle (the step angle of full-step drive such as 1-phase excitation or 2-phase excitation), and micro-step drive is a drive method that reduces the step angle compared to half-step drive.

[0075] In the above embodiment, the rotor unit 90 and the stator unit 92 are respectively assembled to the passage body 200, thereby indirectly fixing the two together. In a modified example, the rotor unit may be directly fixed to the stator unit to form a valve unit, and the valve unit may be assembled to the passage body. The rotor unit and the stator unit may also be fixed via a connecting member. In this case, the valve unit may be considered as an "electric valve." The passage body may be the body or housing of the device to which the electric valve is attached.

[0076] In the above embodiment, the spring 37 is exemplified as the biasing member that biases the valve element 34 in the valve closing direction, but rubber or other elastic bodies may also be used.

[0077] In the above embodiment, the stator includes a yoke having pole teeth. In a modified example, the stator may include a laminated core.

[0078] In the above embodiment, the stator unit 92 is a two-phase stepping motor, but it may also be configured as a three-phase stepping motor.

[0079] In the above embodiment, the motor-operated valve is configured as an expansion valve, but it may also be configured as an on-off valve without an expansion function.

[0080] In the above embodiment, the motor-operated valve is applied to the refrigeration cycle of an automotive air conditioner, but the motor-operated valve may be applied to any air conditioner equipped with an electric expansion valve, not limited to vehicles. The motor-operated valve may also be configured as a motor-operated valve for controlling the flow of fluids other than refrigerants, such as in a hot water supply system or a hydraulic control system.

[0081] In the above embodiment, torque reduction control is executed from a predetermined timing during valve closing operation until the valve disc stops at the actuation origin. This prevents or suppresses problems that may arise when the actuation member and rotor are fixed, such as the valve disc biting into the valve seat when the valve is closed, wear on the valve seat, and jamming of the screw in the screw feed mechanism. In other words, the problem of preventing or suppressing the occurrence of such problems can be solved.

[0082] Such motor-operated valves can be specified, for example, as follows: a body having a first port, a second port, a valve hole provided in a passage that connects the first port and the second port, and a valve seat provided at an open end of the valve hole; a valve body that is attached to and detached from the valve seat to open and close the valve portion; a stepping motor including a rotor for driving the valve body in the opening and closing directions of the valve portion; an actuating member coaxially connected to the rotor and integrally provided with the valve body; a guide member integrally provided on the body; a screw feed mechanism that is realized by a first screw of the guide member and a second screw of the actuating member, and that converts the rotational motion of the rotor into the translational motion of the actuating member; a restricting structure that restricts rotation of the operating member relative to the rotor; a control unit that controls the driving of the stepping motor; Equipped with When the valve element operates in the valve closing direction, the valve element can rotate within a certain allowable range while maintaining a seated state from a seating point where the valve element seats on the valve seat, and the screw feed mechanism is locked by rotation within the allowable range, thereby stopping the valve element at the operating origin, The control unit reduces the drive torque of the motor at a predetermined timing when the valve body is operating to close the valve.

[0083] The present invention is not limited to the above-described embodiments and modifications, and the components can be modified without departing from the spirit of the invention. Various inventions can be formed by appropriately combining multiple components disclosed in the above-described embodiments and modifications. Furthermore, some components can be omitted from all the components shown in the above-described embodiments and modifications. [Explanation of symbols]

[0084] 1 Electric valve, 5 Valve body, 6 Valve housing, 8 Valve seat member, 22 Valve hole, 24 Valve seat, 26 Inlet port, 28 Outlet port, 30 Valve chamber, 32 Actuating rod, 34 Valve body, 36 Guide member, 37 Spring, 38 Male thread, 38b Second surface, 60 Rotor, 64 Stator, 90 Rotor unit, 92 Stator unit, 100 Valve unit, 101 Connecting member, 102 Rotor core, 104 Rotor magnet, 108 Female thread, 108a First surface, 109 Screw feed mechanism, 118 Circuit board, 200 Passage body, 202 Inlet port, 204 Outlet port.

Claims

1. a body having a first port, a second port, a valve hole provided in a passage that connects the first port and the second port, and a valve seat provided at an open end of the valve hole; a valve body that is attached to and detached from the valve seat to open and close the valve portion; a motor including a rotor for driving the valve body in the opening and closing directions of the valve portion; an actuating member coaxially connected to the rotor and integrally provided with the valve body; a screw feed mechanism that converts the rotational motion of the rotor into the translational motion of the actuating member; a guide member integrally provided on the body; a restricting structure that restricts rotation of the operating member relative to the rotor; Equipped with the screw feed mechanism is realized by a first screw provided in the guide member and a second screw provided in the actuation member, a predetermined radial clearance is set between the first screw and the second screw; When the valve element operates in the valve closing direction, the valve element can rotate within a certain allowable range while maintaining a seated state from a seating point where the valve element seats on the valve seat, and the screw feed mechanism is locked by rotation within the allowable range, thereby stopping the valve element at the operating origin, The motor-operated valve is characterized in that the clearance is set to be larger than a tolerance set for the concentricity between the valve body and the valve seat.

2. 2. The motor-operated valve according to claim 1, wherein the tolerances include the sum of machining tolerances and assembly tolerances between a plurality of members that affect the concentricity between the valve body and the valve seat.

3. a stepping motor as the motor; a control unit that controls the driving of the motor; Equipped with The control unit 2. The motor-operated valve according to claim 1, wherein the drive torque of the motor is reduced at a predetermined timing when the valve body is closing.

4. The control unit storing a drive step from the operation origin when controlling the motor; A torque switching step set based on the step corresponding to the seating point is held, 4. The motor-operated valve according to claim 3, wherein the drive torque of the motor is reduced when the drive step reaches the torque switching step during the valve closing operation of the valve body.

5. 4. The motor-operated valve according to claim 3, wherein the control unit reduces the drive torque of the motor at a timing when the operation of the valve element switches from a valve-opening operation to a valve-closing operation.

6. The motor-operated valve according to any one of claims 3 to 5, characterized in that the control unit achieves the reduction in the drive torque by at least one or all of changing the drive frequency of the motor from a normal control state when the valve is open, reducing the supply current value, and switching the excitation method to a method that reduces the step angle.

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