JPH0849782A - Screw shaft turning-stop mechanism for linear-motion converter motor - Google Patents

Abstract

PURPOSE:To provide a screw shaft turning-stop mechanism for a linear-motion converter motor that can reduce the sliding frictional resistance of the screw shaft by a relatively simple and low-priced method without the execution of cutting and polishing. CONSTITUTION:A screw shaft 20 is protrusively provided with a blade like protrusion 25 serving as a shaft side engaging part. The blade like protrusion 25 has a first pressed face 25 serving as a first engaging part, and a second pressed face 25b serving as a second engaging part. A motor side housing 12 forming a stator 9 is provided with a turning-stop member 27 provided with a first guide face 29a and a second guide face 29b. At the normal rotating time of a rotor 10, the first pressed face 25a comes in sliding contact with the first guide face 29a, and at the reverse rotating time, the second pressed face 25b comes in sliding contact with the second guide face 29b. As a result, the rotation of the screw shaft 20 is regulated so as to attain positive turning- stop. There is thereby no need to grind a shaft part 20a into an approximately D-shape cross section.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw shaft detent mechanism in a motor, such as a motor type valve, which converts a rotational motion of a rotor into a linear motion of a screw shaft.

[0002]

2. Description of the Related Art Conventionally, for example, a motor type valve is known as a device using a direct-acting conversion motor. An example of the motor type valve is an electric exhaust gas recirculation valve (electric EGR valve) for removing NOx and the like contained in the exhaust gas of an automobile engine. 14 and 15 exemplify a conventional electric EGR valve 60, and its configuration and operation will be described.

As shown in FIG. 15, this electric EG
The R valve 60 is roughly composed of a stepping motor portion 64 including a stator 61, a rotor 62, a screw shaft 63, and the like, and a valve portion 65.
A rotor 62 having a magnet 66 fixed on the outer peripheral surface.
Are rotatably housed inside a stator 61 having a stator coil 67. A lead screw 69 having a female screw portion 68 is fitted inside the rotor 62 so as to be relatively non-rotatable. A screw shaft 63 as shown in FIG. 14B is screwed into the lead screw 69. A male screw portion 70 that engages with the female screw portion 68 is formed on the peripheral surface of the screw shaft 63. That is, by the female screw portion 68 and the male screw portion 70,
One feed screw mechanism is configured.

In the region of the screw shaft 63 on the projecting end side of the male screw portion 70, as shown in FIG. 14 (b), the shaft portion 63a is cut into a substantially D-shaped cross section by cutting using a milling machine or the like. Missed. On the other hand, FIG.
As shown in (a), an insertion hole 73a having a substantially D-shaped cross section is also formed on the side of the bearing 73 that supports the screw shaft 63. Therefore, the screw shaft 63 is linearly movable with respect to the rotor 62 and is relatively unrotatable with respect to the stator 61 by the rotation stopping mechanism formed by the shaft portion 63a having a substantially D-shaped cross section and the insertion hole 73a. At the tip of the screw shaft 63 protruding toward the valve portion 65, the valve seat 7 provided in the return passage is provided.
A valve element 72 that serves to close the return passage by being in close contact with 1 is fixed.

The operation of the electric EGR valve 60 constructed as above will be briefly described. When the stator coils 67 are sequentially excited, the rotor 62 performs either forward rotation or reverse rotation. As described above, the screw shaft 63
Is movable linearly with respect to the rotor 62 and is relatively non-rotatable with respect to the stator 61 by the action of the rotation stop mechanism. The rotational movement of the rotor 62 is converted into the linear movement of the screw shaft 63 by the rotation stopping mechanism and the feed screw mechanism. As a result, the stator 61
The amount of protrusion of the screw shaft 63 from is changed, and the valve body is opened and closed accordingly.

[0006]

As shown in FIG. 14 (a), in the case of the conventional screw shaft 63 which is cut out in a substantially D-shaped cross section, when the rotor 62 rotates, the peripheral surface of the shaft portion 63a is rotated. Side and the inner wall surface side of the insertion hole 73a are two places P
It comes in contact with 1 and P2. More specifically, P
At the position indicated by 1, the cylindrical surface portion of the peripheral surface of the shaft portion 63a and the cylindrical surface portion of the inner wall surface of the insertion hole 73a contact. At the portion indicated by P2, the edge portion of the peripheral surface of the shaft portion 63a and the flat portion of the inner wall surface of the insertion hole 73a are in contact with each other.

However, in the case of the screw shaft 63 formed by cutting, in addition to the fact that milling lines are formed on the cutting surface and cutting burrs remain on the edge part, in addition to the high contact pressure due to line contact, especially at the point P2. The frictional resistance at becomes large. Therefore, with the structure of the conventional detent mechanism, problems such as increase of load torque of the motor, deterioration of durability, and increase of operation failure occurrence rate are likely to occur.

Further, if the polishing process is carried out after the cutting process in order to remove milling lines and cutting burrs, the processing cost will inevitably increase. Further, when the shaft portion 63a has a small diameter, it is necessary to take special measures to prevent the shaft portion 63a from bending during milling and polishing. For this reason, not only the processing cost becomes higher, but also the processing operation itself becomes troublesome.

The present invention has been made to solve the above problems, and an object thereof is to perform a sliding frictional resistance of a screw shaft by a relatively simple and low cost method without performing cutting or polishing. It is an object of the present invention to provide a rotation preventing mechanism for a screw shaft of a direct conversion motor that can reduce

[0010]

In order to solve the above problems, according to the invention of claim 1, a rotor rotatably housed in a stator and having an internal thread portion formed therein, and the internal thread portion. A screw shaft having a male screw part that engages with, and in a motor that converts the rotational motion of the rotor into a linear motion of the screw shaft, a shaft side having a first engaging part and a second engaging part. An engaging portion is provided on the screw shaft, and a rotation stopping portion is provided on the stationary side, and the first guide surface with which the first engaging portion can slidably contact when the rotor rotates forward, and the rotation guide portion when the rotor rotates reversely. The gist of the present invention is a screw shaft rotation stopping mechanism of a direct-acting conversion motor, which is provided in the rotation stopping portion with a second guide surface with which a second engaging portion can slide.

According to a second aspect of the present invention, in the first aspect, the shaft side engaging portion has a forging surface formed by partially upset and forging the screw shaft.

According to a third aspect of the present invention, in the first aspect, the shaft side engaging portion is a part of a pin protruding from the peripheral surface of the screw shaft. In the invention described in claim 4, any one of claims 1 to 3
In the above paragraph, the detent portion is a detent member fixed to the inner wall surface of the motor-side housing that constitutes the stator.

According to a fifth aspect of the present invention, in any one of the first to third aspects, the rotation stopping portion is integrally formed with a resin motor-side housing that constitutes the stator, and It is supposed to project from the inner wall surface of the motor-side housing.

According to a sixth aspect of the present invention, in the fourth or fifth aspect, a tubular protruding portion is formed on the rotation preventing portion, and the shaft side engaging portion can slide on the tubular protruding portion. A slit having a certain width and having the first guide surface and the second guide surface on both sides is formed.

According to a seventh aspect of the present invention, in the sixth aspect, the cylindrical shape is formed at an angle such that at least one of the guide surfaces comes into surface contact with the engaging portion. It is formed by notching the protrusion.

According to an eighth aspect of the present invention, in the sixth or seventh aspect, the tip end surface of the cylindrical protrusion is inclined from the first guide surface to the second guide surface in the circumferential direction. are doing.

[0017]

According to the first aspect of the present invention, the first engaging portion abuts on the first guide surface when the rotor rotates forward, and the second engaging portion contacts the second guide surface when the rotor rotates reversely. Abut. Therefore, the rotation of the screw shaft is restricted by the detent portion. As a result, the rotational movement of the rotor is converted into the linear movement of the screw shaft. That is, even if the shaft portion of the screw shaft is not cut into a substantially D-shaped cross section, a reliable detent is achieved. Further, the shaft side engaging portion of the moving screw shaft slides while being guided by the guide surface.

According to the second aspect of the present invention, since the forging surface and the guide surface are in a state close to surface contact when the rotor rotates, the surface pressure becomes smaller. As a result, the sliding friction resistance of the screw shaft is also reduced.

According to the third aspect of the present invention, since the shaft side engaging portion and the screw shaft are separate bodies, even if the shaft side engaging portion is worn or deformed, it is replaced with a new pin. be able to.

According to the invention described in claim 4, since the motor-side housing and the rotation preventing member are separate bodies, even if the guide surface is worn or deformed, it can be replaced with a new one. In addition, the guide surface can be positioned during assembly.

According to the fifth aspect of the present invention, a part of the motor side housing serves as a rotation preventing portion, so that the number of parts can be reduced. According to the invention described in claim 6, when the screw shaft moves linearly, the shaft side engaging portion slides in each slit while slidingly contacting the guide surface.

According to the invention described in claim 7, when the rotor rotates, at least one of the engaging portions and the guide surface come into substantially complete surface contact, and the surface pressure becomes smaller. As a result, the sliding friction resistance of the screw shaft also becomes extremely small.

According to the eighth aspect of the present invention, when the screw shaft is assembled to the tubular projecting portion, the shaft side engaging portion of the screw shaft is brought into contact with the tip end surface of the tubular projecting portion. Then, when the screw shaft is rotated in this state, the shaft side engaging portion is smoothly inserted into the slit of the cylindrical protruding portion.

[0024]

【Example】

[Embodiment 1] An embodiment in which the present invention is embodied in a screw shaft rotation stopping mechanism of an electric EGR valve will be described in detail with reference to FIGS. 1 to 3.

The electric EGR valve 1 is a device used in an EGR system that recirculates exhaust gas containing unburned gas discharged from an automobile engine or the like into an intake system to reduce harmful components such as NOx. In a general EGR system, an electric EGR valve 1 is arranged on the way of a passage for recirculating exhaust gas in order to control an EGR amount in response to an operating state of an engine (for example, a throttle opening degree). .

First, the overall structure of the electric EGR valve 1 will be described. As shown in FIG. 1, the electric EGR valve 1 is roughly classified into a stepping motor unit 2
And valve part 3. The valve-side housing 4 that constitutes the valve portion 3 has a return passage 5 inside. An inlet port 6 communicating with the exhaust system of the engine is formed at one end of the return passage 5. At the other end of the return passage 5, an outlet port 7 that communicates with the intake system of the engine is formed. Therefore, the exhaust gas discharged from the engine returns to the intake system after passing through the inlet port 6, the recirculation passage 5 and the outlet port 7. Further, in the middle of the return passage 5, a valve body 2 for controlling the flow rate of exhaust gas is provided.
A valve seat 8 with which 3 closely contacts is arranged.

As shown in FIG. 1, the stepping motor section 2 is mainly composed of a stator 9, a rotor 10 and a screw shaft 20. Stator 9
The motor-side housing 12 and the lid member 13 constituting the
It is fixed to the valve-side housing 4 via the connecting housing 14. Motor side housing 12 and lid member 13
A stator coil 11 is arranged in the internal space formed by. Further, the rotor 10 is rotatably accommodated in the internal space via a bearing 15.

The sleeve 16 constituting the rotor 10 is formed of a non-magnetic material into a hollow cylindrical shape. A multi-pole magnetized magnet 17 is fixed to the outer peripheral surface of the sleeve 16 at a position corresponding to the stator coil 11. A resin-made cylindrical lead screw 18 is fitted into the sleeve 16 so as not to rotate relative to the sleeve 16. Lead screw 18
A female screw portion 19 is formed in a hole penetrating the central portion of the. The sleeve 16, the magnet 17 and the lead screw 18 are integrally rotated as one rotor 10.

As shown in FIG. 1, the lead screw 18 has a screw shaft 20 made of a metal material.
Is screwed in. As shown in FIG. 2A, a male screw portion 21 that engages with the female screw portion 19 is formed on the peripheral surface of the screw shaft 20. In FIG. 1, the lower end side (protruding end side in this embodiment) of the screw shaft 20 penetrates the lid member 13 and projects toward the valve portion 3 side.

In the screw shaft 20, the shaft portion 20a on the projecting end side of the male screw portion 21 has a circular cross section. The shaft portion 20a has an insertion hole 2 having a circular cross section.
It is supported by an oil-impregnated bearing 22 having 2a. The oil-impregnated bearing 22 is fixed to the lid member 13. The tip end of the screw shaft 20 on the protruding side reaches the return passage 5 of the valve-side housing 4. A valve element 23 that serves to close the return passage 5 by being in close contact with the valve seat 8 is fixed to the tip portion. The valve body 23 and the valve seat 8 are arranged in close proximity to each other.

Next, the structure of the rotation stopping mechanism for the screw shaft 20 will be described. As shown in FIGS. 2A and 2C, the non-projecting end of the screw shaft 20 is
The forging portion 24 is formed by swaging. The forging portion 24 includes the wing-shaped projection 2 as a shaft-side engaging portion.
It has two 5. The two wing-shaped projections 25 have a substantially rotationally symmetrical positional relationship with respect to the axis of the screw shaft 20. Each of these wing-shaped projections 25 has a first forging surface 25a as a first engaging portion and a second forging surface 25b as a second engaging portion. Also,
The first pressing surface 25a and the second pressing surface 25b are parallel to the axial direction of the screw shaft 20.

When the wing-shaped projection 25 is formed on the screw shaft 20, compression molding is carried out with the non-projecting end, which is the portion to be pressed, being arranged between the molds. Then, the wing-shaped projection 25 having a predetermined shape is formed by plastically deforming the portion on the non-projecting end side of the constricted portion 20b.

As shown in FIGS. 2 (b) and 3, the rotation preventing member 27 as a rotation preventing portion includes a disc-shaped base portion 28 and a cylindrical protruding portion 29 protruding from the base portion 28. It is configured. The detent member 27 is made of, for example, a copper-based sintered oil-impregnated metal or the like. Two slits 30 extending along the axial direction of the tubular projecting portion 29 are formed in the tubular projecting portion 29. The two slits 30 are substantially rotationally symmetric with respect to the axis of the tubular protrusion 29. By forming these slits 30, as shown in FIG. 3, a first guide surface 29a is provided on the side surface of the cylindrical protruding portion 29,
A second guide surface 29b is provided. The first guide surface 29a has the first press surface 2 when the rotor 10 rotates in the normal direction.
5a is in sliding contact. On the other hand, the second guide surface 29b has a second press surface 25 when the rotor 10 rotates in the reverse direction.
b is in sliding contact. The first guide surface 29a and the second guide surface 29b are set to be longer than the linear movement distance of the screw shaft 20. Further, the first guide surfaces 29a facing each other
And the second guide surface 29b are parallel to each other,
Both extend along the axial direction of the cylindrical protrusion 29.

In the case of this embodiment, the width T of the slit 30 is
Has a dimension slightly larger than the wall thickness t of the wing-shaped projection 25. Therefore, a width is ensured between the first guide surface 29a and the second guide surface 29b to such an extent that the wing-shaped projection 25 can slide. Also, the forging unit 24
The diameter D of the central hole 32 that guides the head 31 is also slightly larger than the diameter d of the head 31.

As shown in FIG. 1, the anti-rotation member 27 as described above is press-fitted and fixed in the concave portion of the upper inner wall surface of the motor-side housing 12 with the tubular projecting portion 29 facing downward. There is. That is, in this embodiment, the screw shaft 20 having the first and second forging surfaces 25a and 25b is provided.
And the detent member 27 having the first and second guide surfaces 29a, 29b constitute one detent mechanism.

Further, as shown in FIG. 1, a convex portion 26 is formed on the upper end surface of the lead screw 18.
The height of the convex portion 26 is set to be slightly shorter than the distance that the screw shaft 20 linearly moves when the rotor 10 makes one rotation. Therefore, the screw shaft 20
When it is fully rotated, the lower region of one of the two wing-shaped projections 25 comes into circumferential contact with the side surface of the convex portion 26 instead of the upper end surface of the lead screw 18. That is, in this embodiment, the lead screw 18 having the convex portion 26 and the screw shaft 20 having the wing-shaped protrusion 25 are provided.
The reference position determination mechanism is constituted by and. The reference position determining mechanism also serves as a mechanism for preventing the screw shaft 20 from coming off.

The electric EGR valve 1 is assembled in the following order, for example. First, after assembling the rotor 10, attach the screw shaft 20 to the lead screw 1
The screw shaft 20 is screwed in from the upper end surface side of 8 and the screw shaft 20 is rotated until the lower region of the wing-shaped projection 25 contacts the side surface of the convex portion 26. After the non-rotatable state due to the abutment (that is, after the reference position is determined), the screw shaft 20 is inserted into the insertion hole 22a to cover the lid member 13.
Attach. Next, the valve body 23 is attached to the tip of the screw shaft 20 on the protruding side. And the rotor 10
Are housed in the motor-side housing 12. At this time, the detent member 27 is positioned with respect to the motor-side housing 12 so that the positions of the wing-shaped protrusions 25 and the positions of the slits 30 coincide with each other.

Next, the electric EG constructed as described above
The function and effect of the R valve 1 will be described. Electric EGR
A computer provided outside the valve 1 detects the vehicle speed, the engine speed, the engine temperature, etc., which indicate the operating state of the engine, in addition to the opening of the throttle described above. The computer outputs an electric signal calculated based on the detection result to the stepping motor unit 2 to sequentially excite the stator coil 11. In this case, the rotor 10
It makes a stepwise rotational movement in the forward or reverse direction by an angle corresponding to the supplied electric signal.

When the rotor 10 is rotationally controlled in the clockwise direction (here, the positive direction) as viewed from the direction of arrow A1 in FIG.
The screw shaft 20 also tries to rotate in the same direction as the screw shaft 20 rotates. However, at this time, the first forging surface 25
The rotation of the screw shaft 20 is restricted by the line contact or the surface contact between the a and the first guide surface 29a. In this case, the screw shaft 20 moves upward, that is, toward the non-projecting end side by the action of the feed screw mechanism described above. At that time, the first pressed surface 25a of the wing-shaped projection 25 slides smoothly while being guided by the first guide surface 29a. As a result, the distance between the valve body 23 provided at the protruding end of the screw shaft 20 and the valve seat 8 increases. Therefore, the return passage 5 is displaced to the open state, and the EGR amount increases.

On the contrary, when the rotor 10 is rotationally controlled in the counterclockwise direction (here, the opposite direction) as viewed from the direction of the arrow A1 in FIG. 1, the screw shaft 20 also tries to rotate in the same direction along with the rotation. However, at this time the second
Due to the line contact or surface contact between the forging surface 25b and the second guide surface 29b, the rotation of the screw shaft 20 is restricted. In this case, the action of the feed screw mechanism causes the screw shaft 20 to move downward, that is, toward the protruding end side. At that time, the second pressed surface 25b of the wing-shaped projection 25 slides smoothly while being guided by the second guide surface 29b. As a result, the distance between the valve body 23 and the valve seat 8 is reduced. Therefore, the return passage 5 is displaced to the closed state, and the EGR amount is reduced.

In the rotation preventing mechanism of this embodiment, which has the wing-shaped projection 25 formed by the swaging press as a constituent element, the shaft portion 20a does not need to be cut out in a substantially D-shaped cross section.
A detent can be achieved. Therefore, unlike the case of the conventional detent mechanism, it is not necessary to perform the cutting process on the shaft portion 20a of the screw shaft 20. Therefore, milling creases and cutting burrs that cause an increase in the sliding friction resistance of the screw shaft 20 do not occur, and the sliding friction resistance can be reduced. Therefore, reduction of the load torque of the motor, downsizing of the motor, improvement of durability, reduction of operation failure occurrence rate, etc. are surely achieved. In this embodiment, both forging surfaces 25a, 25b and both guide surfaces 29a, 2
9b and the surface contact state are close to each other, so that the surface pressure is relatively small.

Further, in this embodiment, as the means for forming the wing-shaped projections 25, swaging forging which does not cause burrs or the like is adopted. Therefore, it is not necessary to polish the first and second pressed surfaces 25a and 25b, and the processing cost can be kept low. Moreover, since it is not necessary to take any special measures to prevent the deformation of the shaft portion 20a during the upsetting, the manufacturing becomes easier as compared with the case where the grinding process is performed.

Further, in this embodiment, since the motor side housing 12 and the rotation stopping member 27 are separate bodies, even if the guide surfaces 29a and 29b are worn or deformed,
Only the detent member 27 can be replaced with a new one. Therefore, the repair cost is lower than when the entire motor-side housing 12 is replaced. Furthermore, the guide surface 2
Since the 9a and 29b can be positioned, it is advantageous in assembling.

Further, in this embodiment, the rotation stopping member 27 and the wing-shaped projection 25 constituting the rotation stopping mechanism are provided on the non-projecting end side. Therefore, the screw shaft 20 can be screwed from the upper end surface side of the lead screw 18 at the time of assembly. If it is desired to provide the wing-shaped projections 25 on the protruding end side, it may be difficult to screw the screw shaft 20 depending on the configuration. Considering the above points, it can be said that the configuration in which the wing-shaped projections 25 and the like are provided on the non-projecting end side is superior in terms of ease of assembly. Further, since a part of the wing-shaped projections 25 forming the rotation stopping mechanism forms part of the reference position determining mechanism and the retaining mechanism, the structure can be simplified as compared with the case where they are provided separately. it can. [Embodiment 2] Next, a rotation stopping mechanism of Embodiment 2 will be described with reference to FIG. The detent member 35 of this embodiment has a configuration slightly different from that of the detent member 27 of the first embodiment. Since the configuration other than the rotation stopping member 35 is basically the same as that of the first embodiment, detailed description thereof will be omitted.

The detent member 2 of the first embodiment shown in FIG.
7, the first guide surface 29a and the second guide surface 29b
The slits 30 were formed so that and were parallel to each other. On the other hand, in the detent member 35 of the present embodiment shown in FIGS. 4A and 4B, the slit 36 is formed by a method different from that.

That is, the slit 36 is formed at a predetermined angle θ so that the first guide surface 29a and the second guide surface 29b facing each other are in a non-parallel relationship. In addition,
In FIG. 4A and FIG. 4B, the size of the slit 36 is emphasized compared to the actual configuration.

With the above structure, when the rotor 10 rotates in the normal direction, as shown in FIG.
The rotation of the screw shaft 20 is restricted by the surface contact of the 9a with the first forging surface 25a almost completely.

Similarly, when the rotor 10 rotates in the reverse direction, as shown in FIG.
As shown in (b), the second guide surface 29b is the second
The rotation of the screw shaft 20 is regulated by making almost full surface contact with the forging surface 25b. Since the surface contact can be achieved almost completely as described above, the surface pressure becomes smaller than that in the first embodiment. Therefore, it is possible to more reliably achieve the reduction of the load torque of the motor, the downsizing of the motor, the improvement of the durability, and the reduction of the malfunction occurrence rate. [Third Embodiment] Next, a rotation preventing mechanism of a third embodiment will be described with reference to FIG. In this embodiment, a screw shaft 37 having a different structure from that of the first embodiment is used. The configuration other than the screw shaft 37 is basically the same as that of the first embodiment.
Since there is no difference, the detailed description will be omitted.

As shown in FIG. 5, three through holes 38 having a circular cross section are formed in a portion of the screw shaft 37 which is on the non-projecting end side of the male screw portion 21. Each of these through holes 38 extends through the axis and along the radial direction. Spring pins 39 having a circular cross section and having slits are fitted into the through holes 38 with both ends thereof protruding. That is, in this embodiment, both ends of each spring pin 39 provided separately from the screw shaft 37 serve as shaft-side engaging portions 40.

A specific portion on the peripheral surface of the end of the spring pin 39 is the first guide surface 29 when the rotor 10 rotates in the normal direction.
It comes into contact with a. That is, in this detent mechanism, the portion functions as the first engagement portion 40a. The part 180 ° away from the specific part comes into contact with the second guide surface 29b when the rotor 10 rotates in the reverse direction. That is, in this detent mechanism, this portion functions as the second engagement portion 40b. The spring pin 39 located closest to the male screw portion 21 comes into contact with the convex portion 26 when the rotor 10 is fully rotated counterclockwise. Therefore, the spring pin 39 also constitutes a part of the reference position determining mechanism and the retaining mechanism.

With the above structure, the spring pin 39
Since the screw shaft 37 and the screw shaft 37 are separate bodies, even if the shaft side engaging portion 40 is worn or deformed, it can be replaced with a new one. Therefore, there is an advantage that the entire screw shaft 37 does not need to be replaced and repair can be partially performed. Further, since the two shaft side engaging portions 40 can be formed by using one spring pin 39, the structure becomes relatively simple. In addition to this, elastic spring pin 39
Because of the use of, it is unlikely that the position shift or the through-hole 38 comes off. [Embodiment 4] Next, a detent mechanism of Embodiment 4 will be described with reference to FIGS. In this embodiment, the location of the detent mechanism is different from that of the first embodiment. As shown in FIGS. 7 and 8, the lid member 13 has a cylindrical housing portion 13
a is provided. An oil-impregnated bearing 22 having an insertion hole 22a having a circular cross section is fixed to the opening of the accommodation portion 13a. In the upper region of the oil-impregnated bearing 22, the detent member 27 described in the first embodiment is press-fitted and fixed with the cylindrical protrusion 29 facing upward.

As shown in FIGS. 6 and 8, in the screw shaft 42 of this embodiment, a forging portion 43 having two wing-like projections 44 is formed in a region on the projecting end side of the male screw portion 21. . Each wing-shaped protrusion 44 includes a first forging surface 44a as a first engaging portion and a second forging surface 44b as a second engaging portion.

One through hole 38 is formed in a region on the non-projecting end side of the male screw portion 21. The through hole 38
A spring pin 39 shorter than that used in the third embodiment is fitted therein. The end portion of the spring pin 39 engages with the convex portion 26 to determine the reference position and prevent the stopper from coming off.

With the above construction, the first forging surface 44a and the first guide surface 29a make a line contact with each other when the rotor 10 rotates in the normal direction, and the second forging surface 44b and the second guide surface 29a when the rotor rotates in the reverse direction. Line contact is made with the surface 29b. As a result, rotation prevention of the screw shaft 42 is achieved. [Fifth Embodiment] Next, a rotation preventing mechanism of a fifth embodiment will be described with reference to FIG. In this embodiment, the rotation stopping portion 46 formed integrally with the motor side housing 45 by using resin as a molding material is used as a part of the rotation preventing mechanism. In the rotation preventing portion 46, the cylindrical protruding portion 29 is provided so as to protrude downward from the inner wall surface of the motor side housing 45. The cylindrical protrusion 29 has two slits (not shown) similar to those of the first embodiment.

With the above construction, since the motor-side housing 45 partially serves as the detent portion 46, the detent members 27 and 35 made of sintered oil-impregnated metal can be omitted. Therefore, the number of parts can be reduced,
It will also be cheaper. Further, in this embodiment, since the whirl-stop mechanism is formed by the combination with the wing-shaped projection 25 capable of reducing the surface pressure, even if the whirl-stop portion 46 is made of resin, abrasion and deformation are less likely to occur. This means that the range of materials that can be used for the detent portion 46 is wider than in the conventional configuration.

The present invention is not limited to the above embodiment, but can be modified as follows. (1) FIGS. 10 (a) and 10 (b) show a rotation stopping mechanism of the first modification. Here, a shaft side engaging portion 48 having a flat shape as a whole is formed on a part of the screw shaft 47 by upsetting, and a part of the shaft side engaging portion 48 is formed on the first engaging portion 48a and the second engaging portion 48b. I am trying. The screw shaft 47 having the above structure is shown in FIG.
It is used in combination with the anti-rotation member 27 of the first embodiment shown in 0 (b).

(2) FIGS. 11 (a) and 11 (b) show a rotation stopping mechanism of the second example. here,
A semicircular arc-shaped protrusion 50 is provided on the base portion 28 that constitutes the rotation stopping member 49, and the semicircular arc-shaped protrusion 50 is provided with one first guide surface 50a and one second guide surface 50b. . The detent member 49 having the above-described configuration is shown in FIG.
The screw shaft 20 of the first embodiment shown in FIG.
Used in combination with etc.

(3) FIGS. 12 (a) and 12 (b) show a rotation stopping mechanism of the third example. here,
Three through holes 38 are formed in the screw shaft 51,
Three shorter spring pins 39 are fitted in them. The end portion of each spring pin 39 serves as a shaft-side engaging portion 40 having a first engaging portion 40a and a second engaging portion 40b. In the detent member 52 used in combination with the screw shaft 51, for example, the slit 54 is formed only at one location of the cylindrical protruding portion 53. The cylindrical protrusion 53 has a first guide surface 53a and a second guide surface 53b, respectively.
Have one each.

(4) The method for forming the wing-shaped projections 25 is as follows.
It is not limited only to swaging. For example, as long as the processing method does not allow burrs or the like on the surfaces of the engaging protrusions, of course, other conventionally known forging processing may be adopted. Alternatively, the wing-shaped projections 25 may be formed as separate members, and the wing-shaped projections 25 may be fixed to the screw shaft 20 by a method such as press fitting, welding, or adhesion. Furthermore, the pterygium 2
5 may be formed by resin molding or the like and then fixed to the screw shaft 20 by outsert molding.

(5) The anti-rotation portion is not always the first to the first embodiment.
It does not need to be the cylindrical protruding portion 29 such as 5. For example, the side surfaces of the plurality of pins protruding from the base portion 28 may be used as the guide portion. However, the structure of each embodiment is more advantageous in terms of strength and surface contact.

(6) In Examples 1 and 2, the number of wing-shaped projections 25 provided on the forging portion 24 may be three or more. As the number of wing protrusions 25 formed increases, each wing protrusion 2
5, the surface pressure applied to each of the guide surfaces 29a and 29b is further reduced, and wear and deformation can be prevented. It is also possible to adopt a configuration in which only one wing-shaped projection 25 is provided.

(7) Instead of the configuration shown in the first embodiment,
The position of the valve body 23 is below the valve seat 8, that is, the return passage 5
It may be configured to be arranged on the inlet port 6 side in. (8) Like the rotation stopping member 55 shown in the other example 4 of FIG. 13, the distal end surface 56c of the cylindrical protruding portion 56 extends from the first guide surface 56a to the second guide surface 56b along the circumferential direction. You may incline. Assembly when the above configuration is adopted will be described. First, each wing-shaped protrusion 25 of the screw shaft 20 is brought into contact with each tip surface 56c of the cylindrical protrusion 56. Then, in this state, the screw shaft 20 is rotated in a predetermined direction. Then, the upper portions of the wing-shaped projections 25 are guided to the tip surface 56c, and finally both the wing-shaped projections 25 are smoothly inserted into the slits 57 of the tubular protruding portion 56. Therefore, according to this configuration, the blade-shaped projection 25 of the screw shaft 20 and the slit 57 of the cylindrical projection 56 are different from those in the case where the tip end surface of the cylindrical projection 29 is flat as in the first embodiment. Assembleability is surely improved.

(9) Spring pin 39 of Embodiment 3 etc.
Instead of this, for example, a simple pin may be press-fitted. (10) In place of the press-fitting fixing method shown in the first embodiment or the like, the fixing member 27 is fixed to the recess of the upper inner wall surface of the motor side housing 12 by another fixing method such as assembling or insert molding. Good.

(11) The present invention is not limited to those in which the screw shafts 20, 42, etc. directly drive the valve element 23, but can be embodied in those which indirectly drive the valve element 23. Is also possible. Of course, it is also possible to embody a valve other than the electric EGR valve 1. Furthermore, it is possible to embody not only the valve but also various actuators, for example.

Here, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-described embodiments and other examples will be listed below together with their effects. (1) In any one of claims 4 and 5, it is a detent without a slit having a semi-circular protrusion. With this configuration, the configuration becomes simpler, and easy assembly and cost reduction can be achieved.

(2) In claim 7, both end portions of the plurality of spring pins fitted in the through holes formed along the radial direction of the screw shaft are used as shaft side engaging portions. With this configuration, it is possible to provide the first and second engagement portions at two positions on one pin.

The technical terms used in this specification are defined as follows. -Upset forging: A processing method of performing compression molding in a state where a metal material is placed between molds, for example, hot forging, warm forging, cold forging, and the like.

[0068]

As described above in detail, according to the inventions described in claims 1 to 7, the moving friction of the screw shaft can be performed by a relatively simple and low cost method without performing cutting or polishing. The resistance can be reduced. Therefore, it is possible to reduce the load torque of the motor, reduce the size of the motor, improve the durability, and reduce the operation failure occurrence rate.

According to the second aspect of the present invention, since the surface pressure of the sliding contact portion becomes smaller, the moving frictional resistance of the screw shaft can be further reduced. Claim 3
According to the invention described in (1), the screw shaft can be replaced with a new pin even when wear or the like occurs, so that the screw shaft can be partially repaired.

According to the fourth aspect of the present invention, repair costs can be kept low even when wear or the like occurs, and the assembling work can be facilitated. According to the invention as set forth in claim 5, the number of parts can be small, so that cost reduction can be achieved.

According to the invention described in claim 7, since the engaging portion and the guide surface can be brought into almost completely surface contact with each other, the moving frictional resistance of the screw shaft can be made extremely small.

According to the invention described in claim 8, the assembling property of the shaft side engaging portion of the screw shaft and the slit of the cylindrical protruding portion can be improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view generally showing an electric EGR valve according to a first embodiment.

2A is a partial perspective view showing a screw shaft used in the electric EGR valve shown in FIG. 1, FIG. 2B is a perspective view showing a rotation stopper member, and FIG.
It is sectional drawing in the B line.

FIG. 3 is a partial schematic cross-sectional view taken along the line AA of FIG.

4A and 4B are schematic cross-sectional views showing a rotation stopping mechanism of the second embodiment.

FIG. 5 is a partial perspective view showing a screw shaft according to a third embodiment.

FIG. 6 is a partial perspective view of a screw shaft according to a fourth embodiment.

FIG. 7 is a partial vertical sectional view showing an electric EGR valve according to a fourth embodiment.

8 is a schematic cross-sectional view taken along the line CC of FIG.

FIG. 9 is a partial vertical sectional view showing an electric EGR valve according to a fifth embodiment.

10A is a partial perspective view showing a screw shaft of another example 1, and FIG. 10B is a perspective view showing a detent member used in combination therewith.

FIG. 11 (b) is a perspective view showing a rotation preventing member of Modification 2, and FIG. 11 (a) is a partial perspective view showing a screw shaft used in combination therewith.

FIG. 12 (a) is a partial perspective view showing a screw shaft of Modification 3, and FIG. 12 (b) is a perspective view showing a rotation stopping member of the same.

FIG. 13 is a perspective view showing a rotation stopping member of Modification 4.

FIG. 14A is a schematic cross-sectional view of a main part of a conventional screw shaft rotation preventing mechanism, and FIG. 14B is a partial perspective view of the screw shaft.

FIG. 15 is a vertical cross-sectional view generally showing a conventional electric EGR valve.

[Explanation of symbols]

9 ... Stator, 10 ... Rotor, 12, 45 ... Motor side housing, 19 ... Female screw part, 21 ... Male screw part, 20, 4
2, 47, 51 ... Screw shafts, 25, 44 ... Wing-shaped projections as shaft-side engaging portions, 25a, 44a ... First forging surface as first engaging portions, 25b, 44b ...
Second forging surface as a second engaging portion, 27, 35, 4
9, 52, 55 ... Anti-rotation member as anti-rotation portion, 2
9, 53, 56 ... Cylindrical protrusions, 29a, 50a, 53
a, 56a ... First guide surface, 29b, 50b, 53
b, 56b ... second guide surface, 30, 36, 54, 57
… Slits, 39… Spring pins as pins, 40
... Ends of spring pins as shaft side engaging portions, 4
0a ... 1st engaging part, 40b ... 2nd engaging part, 46
… Rotation stop.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuzuru Ikeda 2-chome Toyota-cho, Kariya city, Aichi Prefecture Toyota Industries Corporation

Claims (8)

[Claims] 1. A rotor, which is rotatably accommodated in a stator and has a female screw portion formed therein, and a screw shaft having a male screw portion that engages with the female screw portion. In a motor for converting linear movement of a screw shaft, a shaft side engaging portion having a first engaging portion and a second engaging portion is provided on the screw shaft, and a rotation stopping portion is provided on a stationary side, A first guide surface with which the first engaging portion can slide in the normal rotation of the rotor and a second guide surface with which the second engaging portion can slide in the reverse rotation of the rotor as the detent portion. A rotation stop mechanism for the screw shaft of the direct conversion motor provided. 2. The screw shaft of a direct-acting conversion motor according to claim 1, wherein the shaft-side engaging portion has a forging surface formed by partially upsetting the screw shaft. Non-rotating mechanism. 3. The shaft side engaging portion is a part of a pin protruding from a peripheral surface of the screw shaft.
Non-rotating mechanism for the screw shaft of the direct-drive conversion motor described in. 4. The screw for a direct-acting conversion motor according to claim 1, wherein the detent portion is a detent member fixed to an inner wall surface of a motor-side housing that constitutes the stator. Shaft rotation prevention mechanism. 5. The rotation preventing portion is formed integrally with a resin-made motor-side housing that constitutes the stator, and projects from an inner wall surface of the motor-side housing. 2. A rotation preventing mechanism for a screw shaft of a direct conversion motor according to item 1. 6. A cylindrical protrusion is formed on the rotation preventing portion, and the cylindrical protrusion has a width that allows the shaft side engaging portion to slide, and the first guide is provided on both sides. 5. A slit having a surface and a second guide surface is formed.
Alternatively, a rotation preventing mechanism for the screw shaft of the direct-acting conversion motor described in 5 above. 7. The slit is formed by cutting out the cylindrical protrusion at an angle such that at least one of the two guide surfaces comes into surface contact with the engaging portion. 6. A rotation preventing mechanism for a screw shaft of a direct conversion motor according to item 6. 8. The direct-acting conversion motor according to claim 6, wherein the tip end surface of the cylindrical protruding portion is configured to be inclined from the first guide surface to the second guide surface along the circumferential direction. Screw shaft rotation stop mechanism.