SPINNING UNIT IN OPEN-END SPINNING MACHINE

Abstract: A spinning unit of an open-end spinning machine is disclo­ sed which comprises a rotor (9) having an inner wall (9a), a bottom portion (9b) and an open end opposite to said bottom portion and arranged to rotate about a center axis perpendicular to said bottom portion; and a stationary closing member (20) projecting into a spinning chamber (10) of said rotor to thereby close the open end of said rotor and provided with a fiber supply duct (11) which opens toward the inner wall of the rotor, and a yarn guide hole (141) which opens in an end surface thereof opposite to the bottom portion of the rotor. The fiber supply duct is arranged in the closing member so that an inner wall of the fiber supply duct located on a side of the rotational cen­ ter of the rotor is extended to be near to the rotational center of the rotor or to be over the rotational center of the rotor. The width of the fiber supply duct is establi­ shed to be not larger than 90 percent of the diameter of the closing member.

Description: FIELD OF THE INVENTION The present invention relates to, in a spinning unit of an open-end spinning machine, a structure of a fiber supply duct and an outlet position of a yarn guide hole for drawing out a bundle of fibers collected in a greatest inner-diameter portion of a rotor in the form of a yarn. BACKGROUND OF THE INVENTION Generally, in the conventional open-end spinning machine shown in Fig. 1, a bundle of fibers, that is, a sliver 3 supplied through an inlet 2 of a spinning unit 1 is transported to a combing roller 6 by means of a feed roller 4 in cooperation with a presser 5 which presses the sliver 3 onto the feed roller 4. Then, the sliver 3 is opened into individual fibers by the combing roller 6 and, at the same time, impurities 7, such as leafage, trash and the like, are expelled through an outlet 8. The opened fibers are transported to a spinning chamber 10 of a high-speed rotor 9 through a fiber supply duct 11 by an airstream Y created by negative pressure in the spinning chamber 10 of the rotor 9 rotating at high speed. The fibers thus transported into the spinning chamber 10 reach an inner wall 9a of the rotor 9 through a circular stream created in the spinning chamber 10 by the working of the rotor 9 rotating at high speed. Then the fibers slide toward a fiber-collecting portion 13 which is a greatest inner-diameter portion. In the fiber-collecting portion 13, the fibers are collected and twisted in the shape of a ribbon. The fiber ribbon is drawn out in the form of a yarn 31 through a yarn guide hole 14 which is provided in the center of a closing member 20. The rotor 9 has the spinning chamber 10 closed by the inner wall 9a and a bottom portion 9b. An open end of the spinning chamber 10 opposite to the bottom portion 9b is substantially closed by the closing member (boss portion) 20 formed by part of the frame of the spinning unit 1. The closing member 20 projects into the spinning chamber 10 of the rotor as a boss portion 20 in which an opening portion 111 of the fiber supply duct 11 and a yarn guide opening portion 141 of the yarn guide hole 14 are provided, respectively. Here, in order to draw the fibers into the spinning chamber 10 through the fiber supply duct 11, it is necessary to provide negative pressure in the spinning chamber 10 to form an airstream toward the spinning chamber 10 from the fiber supply duct 11. There are three kinds of systems for airstream formation. A first system is of the forced exhaustion type in which the air in the spinning chamber 10 is sucked out from an upper-side opening end of the rotor by a suction means (not shown) connected to an exhaust port 16 provided at part of a casing 15 covering the rotor 9. A second system is of the self-exhaustion type in which the air in the spinning chamber 10 is expelled through a plurality of exhaust ports 9c provided radially in the bottom portion 9b of the rotor 9 by centrifugal force imparted by the rotor 9. A third system is of the self-and-forced exhaustion type in which the forced exhaustion and the self-exhaustion are used in combination. On the other hand, a channel system and a separator system are now used as means for supplying fibers into the spinning chamber 10. The channel system is of the type in which the fibers are supplied into the spinning chamber 10 through the opening portion 111 provided on a side wall of the boss portion 20 so that the opening portion 111 directly faces the inner wall 9a of the rotor as shown in Fig. 1. The separator system is of the type in which the fibers are supplied into the spinning chamber 10 through the opening portion 111 provided on an end surface of a semicircular slit 201 (Fig. 20 and Fig. 21) formed in a side wall of the boss portion 20 as shown in Figs. 11 through 13. In those systems of open-end spinning machines, the high-speed revolution of the rotor (about 50,000 to 100,000 rpm) has been progressed. With the progress of the revolution speed of the rotor, the diameter of the rotor has decreased. The necessity of reducing the diameter of the rotor with the progress of the revolution speed of the rotor is due to the following reason. As shown in Fig. 23, the spinning tension F applied to the yarn is represented by the equation: F=(1/2)×ρ(D/2)²ω²e µ(ϑ₁+ϑ₂) where ρ represents the linear density (kg/m) of the yarn, D represents the greatest inner-diameter (m) of the rotor, ω represents the angular velocity (rad/s) of the rotor, µ represents the coefficient of friction between the yarn and the guide, and ϑ ₁ and ϑ ₂ represent the contact angles (rad) between the yarn and the guide when the yarn is drawn out. Let the revolution speed of the rotor now be increased, then the tension F applied to the yarn increases in proportion to a square of the revolution speed of the rotor. When the tension F increases, the end breakage occurs during spinning or the elasticity of the yarn thus produced is lost. The large tension F has a bad influence on the handling of the spinning machine and the quality of the yarn. The diameter of the rotor must be reduced in order to attain high-speed revolution of the rotor. Although the diameter of the rotor has been reduced with the progress of the high-speed revolution of the rotor, over-reduction of the diameter of the rotor to attain higher-speed revolution of the rotor induces yarn unevenness and lowering of yarn strength to deteriorate the quality of the yarn. Investigating the cause, the yarn guide passage (yarn guide hole) in the prior art is arranged in the center of the end surface of the boss portion in the conventional system. Therefore, it is necessary to arrange the fiber supply duct (channel passage) 11 to avert the yarn guide hole 14. Because the diameter of the boss portion 20 decreases as the diameter of the rotor decreases, the size of the fiber supply duct 11 is limited by the size of the boss portion 20. In short, the sectional area of the fiber supply duct must be reduced as the diameter of the rotor decreases as shown in Fig. 24. The same tendency exists both in the case of channel system and in the case of separator system. Accordingly, the following description is made only for the case of channel system. When the sectional area of the channel passage decreases as the diameter of the rotor decreases, air resistance increases, so that the air flow from the channel passage decreases. Consequently, the fibers flying within the channel cannot be placed on the airstream well so that the fibers are bent by collision with the wall of the channel to thereby shorten effective fiber length or the fibers during flying are entangled with each other to thereby produce yarn unevenness. A further known spinning unit of an open-end spinning machine (PATENT ABSTRACT OF JAPAN, Vol. 9, No. 271) comprises a stationary closing member with a fiber supply duct being located on one side of the rotational center of the rotor. The side of the fiber supply duct being adjacent to the rotational center is deviated near the outlet of the fiber supply duct towards a down-stream location with regard to the rotational direction of the rotor. Within the closing member a yarn guide opening is not provided for. SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the problems in the prior art and to provide a spinning unit in which fibers flying within a fiber supply duct can be smoothly supplied into a rotor in spite of reduction in size of the rotor, thereby producing a good quality yarn. According to an aspect of the invention, according to claim 1 the spinning unit of an open-end spinning machine comprising a rotor having an inner wall, a bottom portion and an open end opposite to the bottom portion and being arranged to rotate about a center axis perpendicular to the bottom portion, and a stationary closing member projecting into a spinning chamber of the rotor to thereby close the open end of the rotor and being provided with a fiber supply duct which opens toward the inner wall of the rotor, and a yarn guide hole which opens in an end surface thereof opposite to the bottom portion of the rotor, is characterized in that the fiber supply duct is arranged in the closing member so that an inner wall of the fiber supply duct located on a side of the rotational center of the rotor is extended to be over the rotational center of the rotor, and in that the width of the fiber supply duct is established to be not larger than 90 per cent of the diameter of said closing member. According to a further aspect of the invention, According to claim 2 an inner wall of the fiber supply duct is extended to be near the rotational center of the rotor, and the center of the yarn guide opening is eccentrically arranged by a distance from the rotational center. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional view for explaining a spinning unit in an open-end spinning machine; Figs. 2 through 9 are views for explaining essential points of the present invention, in which: Figs. 2 and 3 show the relation in position between the fiber supply duct and the yarn guide opening portion, Fig. 2 being a vertical sectional view thereof, Fig. 3 being a sectional view taken along the line III-III of Fig. 2; and Fig. 4 is a view showing the relation in position between the fiber supply duct and the yarn guide opening portion; Fig. 5 is a view showing the relation between the diameter of the rotor and the percentage in width of the fiber supply duct; Fig. 6 is a view showing the relation between the diameter of the rotor and the magnification in area of the fiber supply duct; Fig. 7 is a view showing the eccentric condition of the yarn guide opening portion in the upper end of the closing member; and Figs. 8 and 9 are views showing the relation between the eccentricity of the yarn guide opening portion and the strength of a single yarn and the relation between the eccentricity of the yarn guide opening portion and the irregularity of thickness, respectively; Fig. 10 through 13 show a first embodiment according to the present invention, in which: Fig. 10 is a vertical sectional view thereof, Fig. 11 is a sectional view taken along the line F-F of Fig. 10, Fig. 12 is a vertical sectional view; and Fig. 13 is a sectional view taken along the line G-G of Fig. 12; Fig. 14 is a partly sectional view of the closing member showing a second embodiment according to the invention; Figs. 15 through 18 show a third embodiment according to the invention, in which: Fig. 15 is a view showing the eccentric of the yarn guide opening portion and the area of the upper end of the closing member; Fig. 16 is a partly sectional view of the closing member; Fig. 17 is a view showing the angle of rotation of the yarn; and Fig. 18 is a view showing the relation between the angle of rotation of the yarn and the tension thereof; Fig. 19 is a partly sectional view of the closing member showing a fourth embodiment according to the present invention; Figs. 20 through 24 show a conventional separator-type spinning unit, in which: Fig. 20 is a partly sectional view thereof, Fig. 21 is a sectional view taken along the line X-X of Fig. 20, Fig. 22 is a view showing the position of the yarn guide opening portion in the upper end of the closing member; Fig. 23 is a view showing the condition that the yarn is drawn out; and Fig. 24 is a view showing the relation between the diameter of the rotor and the sectional area of the fiber supply duct. DETAILED DESCRIPTION OF THE INVENTION In the foregoing conventional spinning unit of an open-end spinning machine, the spinning unit according to another aspect of the invention is characterized in that the yarn guide hole has a yarn guide opening portion which opens toward the bottom portion of the rotor, the center of the yarn guide opening portion being eccentrically arranged at a distance from the rotational center of the rotor. The present inventors have made investigation and analysis of a method for avoiding reducing the sectional area of the fiber supply duct in spite of reduction in size of the rotor or in other words a method for enlarging the ratio of the sectional area of the fiber supply duct to the diameter of the rotor. Then the investigation and analysis have reached the present invention as follows. As described above, it is found that the size of the fiber supply duct in the prior art is limited by the yarn guide opening portion arranged in the center of the end portion of the closing member. According to various examinations about the method for enlarging the fiber supply duct opening toward the inner wall or bottom portion of the rotor, the aforementioned problems are solved by providing a side wall 11b (which is near the center of the end portion 201 of the closing member 20 opposite to the bottom portion of the rotor or in other words near the center of the rotor) of the fiber supply duct 11 near to or over the rotational center of the rotor as shown in Fig. 10 and Fig. 11, compared with the conventional case where the fiber supply duct 11 is arranged to avert the yarn guide hole 14 as shown in Figs. 2 and 3. Let ℓs be the width of the fiber supply duct as shown in Fig. 4, then the sectional area Sℓ of the fiber supply duct is considered to be a function of ℓs. In the drawing, the width ℓs₁ of the fiber supply duct in the conventional case where the fiber supply duct is arranged to avert the yarn guide hole is represented by the equation: ℓs₁=(1/2) (R-r)-2t where R is the diameter of the boss portion, r is the diameter of the yarn guide hole opening at the center of the end surface of the boss portion, and t is the thickness at least necessary for making the fiber supply duct open. When the side wall of the fiber supply duct near to the rotational center of the rotor is extended over the rotational center of the rotor, the width ℓs₂ of the fiber supply duct can be enlarged to ℓs₂=R-r₀-2t at maximum. Accordingly, though ℓs₁ in the conventional case is within the following range: 0<ℓs₁≦(1/2) (R-r)-2t ℓs₂ in the present invention can be enlarged to be within the following range: 0<ℓs₂≦(R-r₀-2t). Particularly, the widening factor ℓ R represented by the equation: ℓ R =ℓ s₂ -ℓs₁ is within the following range: (1/2) (R-r)-2t<ℓ R ≦(R-r₀-2t). Fig. 5 shows the ratio of the width ℓs of the fiber supply duct to the diameter R of the boss portion when the diameter D of the rotor varies for t=0.5 mm and r=5 m or in other words Fig. 5 shows ℓs₁/R and ℓs₂/R. It is apparent from the drawing that the width ℓs in the case of the present invention as shown by the oblique line is relatively widened compared with that in the conventional case as shown by the broken line. As ℓs is widened, the sectional area Sℓ of the fiber supply duct is enlarged. Fig. 6 shows the magnification of the sectional area of the fiber supply duct in the present invention relative to that in the conventional one, with respect to various values of the diameter of the rotor. The sectional area of the fiber supply duct can be enlarged twice at maximum by widening the width thereof. Particularly, the magnification increases as the diameter of the rotor decreases. This is advantageous to the reduction in size of the rotor as one object of the present invention. Further, in the present invention, the aforementioned problems are solved by moving the center of the yarn guide opening portion to an outer portion and arranging it eccentrically by a distance from the rotational center of the rotor, compared with the conventional case where the yarn guide opening portion opens in the center of the end portion of the closing member. Describing in detail as shown in Fig. 7 and Fig. 14, the yarn guide opening portion 141 which, in the conventional case, opens in the center position O₁ (which is located on the rotational center axis of the rotor) of the end portion 201 of the closing member 20 is moved to an outer position O₂ by a distance h from the center, so that the fiber supply duct can be widened corresponding to the displacement h of the yarn guide opening portion. When the yarn guide opening portion is arranged eccentrically by h with respect to the rotational center of the rotor, the tension F applied to the yarn, however, changes periodically with time as represented by the following equation. Accordingly it has been considered in the conventional case that the yarn guide opening portion must be located on the rotational center axis of the rotor. Therefore, the inventors have thoroughly investigated the influence of the tension variations on the quality (irregularity of thickness and yarn strength) of the yarn and the production of the yarn to make an examination as to whether the aforementioned condition is essential or not. First, the relation between the eccentricity of the yarn guide opening portion and the quality of the yarn has been examined experimentally. The results of examination are shown in Figs. 8 and 9. In the drawings, the x-distance represents the eccentricity [h(D/2)] of the yarn guide opening portion. When h/(D/2)=0, the center of the yarn guide opening portion coincides with the rotational center of the rotor as in the conventional case. It is found from the drawings that the quality of the yarn is not affected by eccentrically providing the yarn guide opening portion with the sectional area of the fiber supply duct being kept constant. Further, it has been confirmed by other experiments that the quality of the yarn is little affected by the eccentricity of the yarn guide opening portion. It is apparent from the results that the quality of the yarn is not affected by variations in tension. Further, considering that variations in tension may relate to the end breakage, the same spinning test as described above has been conducted. As the results of examination, it has been found that the end breakage is little affected by the eccentricity of the yarn guide opening portion. The present invention is based on the aforementioned investigation. As an embodiment according to the invention, the yarn guide opening portion is arranged eccentrically with respect to the rotational center axis of the rotor to thereby make it possible to reduce the variation in tension. As another embodiment as shown in Fig. 15, the end portion of the closing member is separated into a small-area region A and a large-area region B by a line m drawn to pass through the center O₂ of the yarn guide opening portion perpendicularly to a line n which is drawn to connect the center of the yarn guide opening portion with the rotational center O₁ of the rotor, so that the frictional resistance of the small-area region A is established to be larger than that of the large-area region B. Means for increasing the frictional resistance of the yarn at the region A are considered corresponding to the surface roughness, material and the like. For example, the surface roughness is provided by forming grooves or fine lines on the surface of the region. According to the aforementioned construction, the frictional resistance of the yarn becomes large at the region A where the rotational radius of the yarn is reduced, so that the tension F of the yarn at the region A increases in spite of the reduction of the rotational radius of the yarn. The same effect can be attained even when the frictional resistance of the region B is established to be smaller than that of the region A. Accordingly, as shown in Fig. 18, the amplitude of the tension variations of the yarn is relatively reduced compared with the case where the end portion of the closing member is formed uniformly (the broken line of Fig. 18), so that the tension variations can be reduced. As a further embodiment as shown in Fig. 19, an upper end member having the guide yarn opening portion disposed near the rotational center of the rotor is provided in the end portion of the closing member opposite to the bottom portion of the rotor, and the yarn guide opening portion is communicated with the yarn guide hole which is shaped like an inclined hole pointing to the rotational center of the rotor through the yarn guide opening portion. According to the aforementioned construction, the center of yarn guide opening portion is arranged to point to a position near the rotational center axis of the rotor, so that the rotational radius of the yarn becomes substantially constant to thereby reduce the amplitude of the tension variations. In the case where the rotor is changed in shape, the relation between the greatest inner-diameter portion of the rotor and the yarn guide opening portion can be freely established only by changing the size or the like, of the upper end member. According to the embodiment, the distance h between the rotational center axis of the rotor and the center of the yarn guide opening portion of the upper end member and the distance h′ between the rotational center axis of the rotor and the center of the yarn guide hole which passes through the boss portion can be freely changed as long as the relation: 0≦h≦h' can be satisfied. When, for example, h=0, the center of the yarn guide opening portion and the rotational center of the rotor are aligned, so that the rotational radius of the yarn becomes constant. Consequently, an advantage exists in that the tension applied to the yarn can be kept constant. Although the embodiment has shown the case where the upper end member is provided so that the center of the yarn guide opening portion can point to a position near the rotational center axis of the rotor, it is to be understood that the invention is not limited to the specific embodiment and that the center of the yarn guide opening portion may be arranged to point to the position near the rotational center axis of the rotor without use of the upper end member. Accordingly, the amplitude of the tension variations can be reduced. It is a matter of course that the aforementioned embodiments may be used in combination suitably. In the spinning unit of an open-end spinning machine according to the present invention, fibers supplied into a spinning chamber of a rotor rotating at high speed through an enlarged fiber supply duct are collected and twisted in the form of a ribbon at a collecting portion of the rotor. The fiber ribbon thus collected is drawn out in the form of a yarn through a yarn guide hole from a yarn guide opening portion eccentrically arranged in the end portion of a closing member with respect to the rotational center of the rotor. As another method, the yarn guide opening portion may be arranged in the rotational center of the rotor so that the yarn can be drawn out through the yarn guide hole from the yarn guide opening portion. According to the present invention, a side wall (which is near the center of the end surface of the closing member opposite to the bottom portion of the rotor or in other words near the center of the rotor) of the fiber supply duct piercing the closing member is arranged to be near to or over the rotational center of the rotor, so that the fiber supply duct is widened. Further, the center of the yarn guide opening portion which opens in the end surface of the closing member opposite to the bottom portion of the rotor is arranged eccentrically at a distance from the rotational center of the rotor. Accordingly, freedom can be given to the position and size of the fiber supply duct which opens toward the inner wall of the rotor. In spite of reduction of the diameter of the rotor with the progress of high-speed revolution of the rotor, it is unnecessary to reduce the fiber supply duct in size. Therefore, air resistance in the fiber supply duct does not increase, so that the fibers flying within the fiber supply duct can be smoothly supplied into the rotor. Consequently, in accordance with the invention, a good-quality yarn can be produced. In order words, the rotor can be reduced in size and diameter by the aforementioned reason to thereby attain an remarkable improvement in high-speed revolution of the rotor. EMBODIMENT 1 In this embodiment the spinning unit was constructed as shown in Figs. 10 and 11, in which the fiber supply duct 11 piercing the closing member 20 opposite to the bottom portion of the rotor 9 was arranged as follows. The side wall 11b of the fiber supply duct 11, which was near the center of the end surface of the closing member opposite to the bottom portion of the rotor or in other words near the rotational center O₁ of the rotor, was extended to be across the rotational center of the rotor to thereby widen the fiber supply duct 11. The opening portion 111 of the fiber supply duct 11 was provided on the side surface of the closing member 20. The size of those portions was determined as shown in Fig. 4. In Figs. 10, 11 and 4, D represents the greatest diameter of the spinning chamber 10 of the rotor 9, R represents the diameter of the root portion of the closing member, r represents the diameter of the yarn guide opening portion, and t represents the thickness between the side wall of the yarn guide hole communicated with the yarn guide opening portion 141 and the outer wall of the closing member. In this embodiment, the thickness t was not smaller than 0.5 mm and the widening factor ℓ R was within a range represented by the relation: (1/2)(R-r)-2t<ℓ R ≦(R-r)-2t. In practice, the thickness t of 0.5 m is required at minimum. In the spinning unit of this embodiment, the inner diameter of the fiber supply duct and its opening portion can be enlarged by the range of ℓ R in spite of the reduction of the diameter of the rotor, compared with the conventional spinning unit. Accordingly, the fibers flying within the fiber supply duct can be smoothly supplied into the rotor without the increase of air resistance, so that the quality of the yarn thus produced can be improved. Accordingly, the rotor can be operated at higher speed. Because the yarn guide hole member 14a (Fig. 10) exists in the middle of the fiber supply duct 11 in this embodiment, the fibers flying within the fiber supply duct 11 may be caught by or may collide with the member 14a so that the fibers may be bent. To cope with this defect, as shown in Figs. 12 and 13, a separator member 14b extended to the upstream of the fiber supply duct 11 or in other words extended near to the upper side of the combing roller can be provided on the side of the yarn guide hole member 14a to thereby separate the fiber supply duct 11 into two parts. According to the aforementioned construction, the fibers released from the combing roller and flying within the fiber supply duct can be prevented from hitching or colliding. EMBODIMENT 2 In this embodiment the spinning unit was constructed as shown in Fig. 14. In the closing member 20 opposite to the bottom portion of the rotor 9, the center of the yarn guide opening portion 141 was eccentrically arranged at a distance h from the rotational center o₁ of the rotor to thereby enlarge the opening portion of the fiber supply duct within a range corresponding to the eccentricity. The opening portion 111 of the fiber supply duct 11 was provided on the side surface of the closing member 20. Fig. 7 shows the relation in position between the yarn guide opening portion 141 and the fiber supply duct 11 in the end surface of the closing member 20 opposite to the bottom portion of the rotor 9. In the drawings, D represents the greatest diameter of the spinning chamber 10 of the rotor 9, R represents the diameter of the root portion of the closing member, r represents the diameter of the yarn guide opening portion, and t represents the thickness between the side wall of the yarn guide hole communicated with the yarn guide opening portion 141 and the outer wall of the closing member. In this embodiment, the thickness t was not smaller than 0.5 mm and the distance h was within a range represented by the relation: 0<h≦(1/2) (R-r)-t In practice, the thickness t of 0.5 mm is required at minimum. By use of the spinning unit of this embodiment, yarn samples of 20S of cotton 100% were produced in the same spinning condition except that the distance h between the center O₂ of the yarn guide opening portion and the rotational center O₁ of the rotor and the area of the opening portion 111 of the fiber supply duct were changed variously. Then the quality of the yarn samples was measured. The result of measurement is shown in Table. As shown in Table, the eccentricity was represented by h/(D/2). In this embodiment, D was 28 mm and the distance h in Sample Nos. 1, 2 and 3 took values of 0.16, 0.86 and 1.53 mm, respectively (in which the revolution speed of the rotor was 120,000 rpm). The term "Area of fiber supply" used in Table means an area of the opening portion 111 of the fiber supply duct. In Table, No. C having the eccentricity of 0 shows the prior art (in which the revolution speed of the rotor is 80,000 rpm). It is apparent from Table that in accordance with the present invention, a spinning excellent in the strength of the yarn and the irregularity of thickness thereof can be made. Figs. 8 and 9 show the results measured in the same manner as described above. In the spinning unit of this embodiment, the inner diameter of the fiber supply duct and its opening portion can be enlarged by the range of h in spite of the reduction of the diameter of the rotor, compared with the conventional spinning unit. Accordingly, the fibers flying within the fiber supply duct can be smoothly supplied into the rotor without the increase of air resistance, so that the quality of the yarn thus produced can be improved. Accordingly, the rotor can be operated at higher speed. EMBODIMENT 3 In this embodiment, as shown in Fig. 15, the region of the end surface of the closing member opposite to the bottom portion of the rotor was separated into two parts, a small area and a large area with respect to the yarn guide opening portion 141, so that the frictional resistance of the former against the yarn was made larger than that of the latter. More particularly, as shown in the drawing, a line n was drawn between the rotational center O₁ of the rotor and the center O₂ of the yarn guide opening portion in the upper end surface of the closing member, and a line m was drawn perpendicularly to the line n through the center O₂ of the yarn guide opening portion, so that the end surface of the closing member was separated by the line m into a small-area region A and a large-area region B. The frictional resistance of the small-area region A was established to be larger than that of the large-area region B. As shown in Fig. 16, an umbrella-like member 202 was provided in the yarn guide opening portion of the closing member so that the difference in coefficient of friction between the regions A and B was established. More particularly, the difference in coefficient of friction was constructed by forming the umbrella-like member 202 of S45C material and by providing a plurality of fine grooves with depth of about 100 µm only in the region A. According to this embodiment, the frictional resistance of the region A is larger than that of the region B, so that the tension F of the yarn in the region A can be increased in spite of the reduction of the rotational radius of the yarn. Therefore, the amplitude of tension variations is reduced compared with the case where the plurality of fine grooves are not provided. Figs. 17 and 18 which relate to the variations in tension as described above, show the relation between the rotational angle (rad β) of the yarn and the tension F thereof. The tension F of the yarn changes with the progress of the rotational angle β thereof as shown in Fig. 18, when the rotational angle β of the yarn is set clockwise and µ₁ and µ₂ represent the coefficients of friction of the regions A and B, respectively, as shown in Fig. 17. In the case of µ₁>µ₂, the tension F changes as represented by the solid line. In the case of µ₁=µ₂, the tension F changes as indicated by the broken line. In short, the amplitude Fa in the former case is smaller than that (Fb) in the latter case. Although this embodiment has shown the case where the difference in frictional resistance between the regions A and B is established by providing the umbrella-like member 202, it is to be understood that the invention is not limited to the specific embodiment and that the difference in frictional resistance may be established directly in the end surface of the closing member without use of the umbrella-like member. EMBODIMENT 4 In this embodiment as shown in Fig. 19, an upper end member 203 in which the center O₂ of the yarn guide opening portion 141 was eccentrically arranged by a distance h from the rotational center O₁ of the rotor 9 was provided in the upper end of the closing member 20. Then the center O₃ of the yarn guide hole piercing the closing member 20 was eccentrically arranged by a distance h′ from the rotational center O₁ of the rotor so that the yarn guide opening portion 141 was communicated with the yarn guide hole 14. The yarn guide opening portion 141 thus arranged on the upper end member 203 was provided in the form of an inclined hole pointing to the rotational center of the rotor. The opening portion 111 of the fiber supply duct 11 was provided to be enlarged compared with the prior art. In this embodiment, the values of respective constants are as follows: h 1.53 m, h′ 3 mm, the diameter of the yarn guide opening portion 2 mm, the diameter of the yarn guide hole 5 mm, and the area of the opening portion of the fiber supply duct 15.62 mm². The upper end member 203 was fixed to the upper end of the closing member 20 by screwing (no shown). According to this embodiment, the center of the yarn guide opening portion points to the rotational center of the rotor, so that the rotational radius of the yarn is kept substantially constant to thereby reduce variations in amplitude of tension. Further, only replacement of the upper end member 203 suffices to cope with the case where the shape of the rotor is changed.

Claims: A spinning unit of an open-end spinning machine comprising: a rotor (9) having an inner wall (9a), a bottom portion (9b) and an open end opposite to said bottom portion (9b) and being arranged to rotate about a center axis perpendicular to said bottom portion (9b); and a stationary closing member (20) projecting into a spinning chamber (10) of said rotor (9) to thereby close the open end of said rotor (9) and being provided with a fiber supply duct (11) which opens toward said inner wall of said rotor (9), and a yarn guide hole (14) which opens in an end surface thereof opposite to said bottom portion (9b) of said rotor (9); characterized in that said fiber supply duct (11) is arranged in said closing member (20) so that an inner wall (11b) of said fiber supply duct (11) located on a side of the rotational center of said rotor (9) is extended to be over the rotational center of the rotor (9), and in that the width of said fiber supply duct (11) is established to be not larger than 90 per cent of the diameter of said closing member (20). A spinning unit of an open-end spinning machine comprising: a rotor (9) having an inner wall (9a), a bottom portion (9b) and an open end opposite to said bottom portion (9b) and being arranged to rotate about a center axis perpendicular to said bottom portion (9b); and a stationary closing member (20) projecting into a spinning chamber (10) of said rotor (9) to thereby close the open end of said rotor (9) and being provided with a fiber supply duct (11) which opens toward said inner wall of said rotor (9), said fiber supply duct (11) is arranged in said closing member (20) so that an inner wall (11b) of said fiber supply duct (11) located on a side of the rotational center of said rotor (9) is extended to be near to the rotational center of said rotor (9), and a yarn guide hole (14) which opens in an end surface thereof opposite to said bottom portion (9b) of said rotor (9); characterized in that the width of said fiber supply duct (11) is established to be not larger than 90 per cent of the diameter of said closing member (20) and in that said yarn guide hole (14) has a yarn guide opening portion (141) which opens toward said bottom portion (9b) of said rotor (9), the center of said yarn guide opening portion (141) being eccentrically arranged by a distance from the rotational center of said rotor (9). A spinning unit of an open-end spinning machine according to claim 1, characterized in that said yarn guide hole (14) has a yarn guide opening portion (141) which opens toward said bottom portion (9b) of said rotor (9), the center of said yarn guide opening portion (141) being eccentrically arranged by a distance from the rotational center of said rotor (9). A spinning unit of an open-end spinning machine according to Claim 2 or 3, characterized in that the thickness between said yarn guide opening portion (141) and the side wall of said closing member (20) is at least 0.5 mm. A spinning unit of an open-end spinning machine according to Claim 3, characterized in that an end portion of said closing member (20) is separated into a small-area region (A) and a large-area region (B) by a line (m) drawn to pass through the center (O₂) of said yarn guide opening portion (141) perpendicularly to another line (n) drawn to connect the center (O₂) of said yarn guide opening portion with to the rotational center axis (O₁) of said rotor (9), so that the frictional resistance of said small-area region is established to be larger than that of said large-area region. A spinning unit of an open-end spinning machine according to any of Claims 2 to 5, characterized in that an upper end member (203) having said guide yarn opening portion (141) disposed near the rotational center of said rotor (9) is provided in the end portion of said closing member (20) opposite to said bottom portion (9b) of said rotor (9), and in that said yarn guide opening portion (141) is communicated with said yarn guide hole (14) which is shaped like an inclined hole pointing to the rotational center of said rotor (9) through said yarn guide opening portion (141).

Inventors: INOUE, TETSUZO, KAWABATA, SUSUMU, NIIMI, HIROSHI
Applicants: KABUSHIKI KAISHA TOYOTA CHUO KENKYUSHO
Application year: 1988
Main classification: D01H4
IPC codes: D01H4