JP2012077796A - Electric drum brake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric drum brake capable of achieving stable power transmission and space saving by expanding brake shoes using a screw mechanism and a link mechanism.SOLUTION: The drum brake includes: a screw shaft 13 of a male screw provided in the radial direction of the brake drum 6 and rotating by a motor 10 via a worm 11 and a worm wheel 12; a holder 14 fixed to a back plate 5 and allowing only the rotation of the screw shaft 13; a slider 15 of a female screw provided on the screw shaft 13; a pivot member 16 provided to a brake shoe 3; a pivot member 17 provided to a brake shoe 4; a link 20 connecting the slider 15 to the pivot member 16; a link 21 connecting the slider 15 to the pivot member 17; a link 22 connecting the holder 14 to the pivot member 16; a link 23 connecting the holder 14 to the pivot member 17; and a shoe expanding mechanism configured by the four links.

Description

  The present invention relates to an electric drum brake including a motor-driven drum brake.

  As a prior art, a drum brake is known in which a pair of brake shoes are expanded to both sides by an electric motor and pressed against a brake drum that rotates with a wheel to generate a braking force. A drum brake that uses an electric motor as a power source rotates a screw (female) through a worm and a worm wheel, and the two screws (male) that are fitted are converted into linear motions in opposite directions. By this, it is a structure which expands a pair of brake shoes to both sides (patent document 1).

  In addition, drum brakes that use an electric motor as a power source transmit power to the planetary gears via a worm and worm wheel, and rotate a ring gear whose outer periphery is cam-shaped, thereby moving a pair of brake shoes to both sides. This is a structure to be expanded (Patent Document 2).

JP 2001-82517 A JP 2006-336868 A

  However, in Patent Document 1, since two screws are coaxially disposed between a pair of shoes, a large space is required. Further, since the protruding member itself that presses the shoe rotates, power transmission from the screw to the shoe becomes unstable.

  In Patent Document 2, since the cam member and the brake shoe slide, it is difficult to obtain a stable power transmission, and there is a concern about a decrease in brake force due to wear of the sliding portion.

  The present invention has been made in view of the above problems, and an object thereof is to provide an electric drum brake capable of realizing space saving, stable power transmission, and stable braking force.

  According to a first aspect of the present invention, there is provided a shoe widening mechanism, a first brake shoe widened by the shoe widening mechanism, a second brake shoe widened by the shoe widening mechanism, A back plate for attaching the shoe spreading mechanism, the first brake shoe, and the second brake shoe; and a brake drum that rotates together with a wheel and presses and brakes the first brake shoe and the second brake shoe. A drum brake, wherein the shoe widening mechanism is provided in a radial direction of the brake drum and is a screw shaft of a male screw that is rotated by a motor; a holder that is fixed to the back plate and allows rotation of the screw shaft; At least one female screw slider provided on the screw shaft and a first pivot for pressing the first brake shoe. The distance between the first pivot member and the second pivot member is varied in conjunction with a change in the relative position of the slider with respect to the screw shaft, the second pivot member pressed against the second brake shoe, and the member. A plurality of links.

  According to a second problem solving means, the plurality of links include a link connecting the slider and the first pivot member, a link connecting the slider and the second pivot member, the holder, and the first A link connecting the pivot member, and a link connecting the holder and the second pivot member.

  According to a third problem-solving means, the plurality of links include a link in which the slider includes two sliders and connects one slider and the first pivot member, and the one slider and the second pivot member. A link for connecting, a link for connecting the other slider and the first pivot member, and a link for connecting the other slider and the second pivot member.

  A fourth problem solving means is that the one slider is a reverse screw with respect to the other slider.

  According to the first problem-solving means of the present invention, the shoe expanding mechanism can be configured in a space-saving manner because the screw shaft is disposed in the radial direction of the brake drum. Further, since the shoe spreading mechanism operates using a link mechanism via a screw mechanism, power can be stably transmitted to the shoe. Further, since the link stroke amount can be set freely, a stable braking force can be maintained.

  According to the second problem solving means of the present invention, the shoe expanding mechanism includes a link connecting the slider and the first pivot member, a link connecting the slider and the second pivot member, a holder and the first pivot. The link that connects the members and the link that connects the holder and the second pivot member form a quadrangle, and the shoe spreading mechanism determines the distance between the first pivot member and the second pivot member relative to the screw shaft. Stable power can be transmitted by varying the relative position of the slider.

  According to the third problem solving means of the present invention, the shoe spreading mechanism includes a link that connects the first slider and the first pivot member, a link that connects the first slider and the second pivot member, The link connecting the two sliders and the first pivot member and the link connecting the second slider and the second pivot member form a quadrangle, and the shoe spreading mechanism includes the first pivot member and the second pivot member. Can be transmitted in conjunction with a change in the relative position of the first slider and the second slider with respect to the screw shaft.

  According to the fourth problem-solving means of the present invention, when the screw shaft is rotated in one direction, the first slider, the second slider, and the screw shaft to which each slider is screwed are rotated at the same pitch. The first slider and the second slider can be moved in different directions.

Sectional drawing seen from the vehicle side surface of the drum brake which concerns on 1st Embodiment of this invention AA sectional view of a drum brake concerning a 1st embodiment of the present invention. BB sectional drawing of the drum brake which concerns on 1st Embodiment of this invention. Sectional drawing seen from the vehicle side surface of the drum brake which concerns on 1st Embodiment of this invention CC sectional drawing of the drum brake which concerns on 1st Embodiment of this invention. Sectional drawing seen from the vehicle side of the drum brake which concerns on 2nd Embodiment of this invention DD sectional view of a drum brake according to a second embodiment of the present invention. Sectional drawing seen from the vehicle side of the drum brake which concerns on 2nd Embodiment of this invention EE sectional drawing of the drum brake which concerns on 2nd Embodiment of this invention.

(First embodiment)
FIG. 1 is a cross-sectional view of a drum brake 1 according to a first embodiment of the present invention when the brake is off. The drum brake 1 includes a shoe expansion mechanism 2, a brake shoe 3 and a brake shoe 4 that are expanded by the shoe expansion mechanism 2, and a back plate 5 that includes the shoe expansion mechanism 2, the brake shoe 3, and the brake shoe 4. A brake drum 6 that surrounds the shoe expansion mechanism 2, the brake shoe 3, and the brake shoe 4 together with the back plate 5, a shoe return spring 7 that retracts the brake shoe 3 and the brake shoe 4 that are expanded when the brake is released, and a brake shoe Anchor pin 8 for fixing 3 to the back plate 5 and anchor pin 9 for fixing the brake shoe 4 to the back plate 5.

  The shoe spreading mechanism 2 is provided in the radial direction of the brake drum 6 and is fixed to a screw shaft 13 of a male screw that rotates from a motor 10 (see FIG. 2) via a worm 11 and a worm wheel 12, and a back plate 5. And a holder 14 that allows only rotation of the screw shaft 13, a female screw slider 15 provided on the screw shaft 13, a pivot member 16 provided on the brake shoe 3, and a pivot member provided on the brake shoe 4. 17, a link 20 connecting the slider 15 and the pivot member 16, a link 21 connecting the slider 15 and the pivot member 17, a link 22 connecting the holder 14 and the pivot member 16, and connecting the holder 14 and the pivot member 17. And the four links 23 to be linked. The links 20 and 21 have the same length, and the slider 15, the pivot member 16, and the pivot member 17 form an isosceles triangle. Similarly, the lengths of the link 22 and the link 23 are equal, and the holder 14, the pivot member 16, and the pivot member 17 form an isosceles triangle.

  FIG. 2 is a cross-sectional view taken along line AA of the drum brake 1 according to the first embodiment of the present invention when the brake is off. The motor 10 is attached to the vehicle body side from the back plate 5 and transmits power from the connected worm 11 to the worm wheel 12 to rotate the screw shaft 13. The holder 14 holds the screw shaft 13 so that it can rotate and does not move in the axial direction.

  FIG. 3 is a BB cross-sectional view of the drum brake 1 according to the first embodiment of the present invention when the brake is off. The pivot member 16 is provided with a recess and is in contact with the brake shoe 3, and the pivot member 17 is provided with a recess and is in contact with the brake shoe 4. The screw shaft 13 is disposed so as to be surrounded by the pivot member 16, the pivot member 17, the link 20, the link 21, the link 22, and the link 23. In addition, the link 20, the link 21, the link 22, and the link 23 have connecting holes at both ends in the longitudinal direction, and these connecting holes serve as the holder 14, the slider 15, the pivot member 16, and the pivot member 17. As a result of the movement of the slider 15 relative to the holder 14, the pivot member 16 and the pivot member 17 can be linked.

  4 is a cross-sectional view of the drum brake 1 according to the first embodiment of the present invention when the brake is on, and FIG. 5 is a CC cross-sectional view of the drum brake 1 according to the first embodiment of the present invention when the brake is on. is there. The motor 10 transmits power from the connected worm 11 to the worm wheel 12 to rotate the screw shaft 13. Compared with FIGS. 1 and 2, the slider 15 moves downward in the drawing, and in conjunction with this, the pivot member 16 and the pivot member 17 move downward in the drawing and left and right in the drawing, The brake shoe 4 is expanded in the horizontal direction of the drawing. The pivot member 16 and the pivot member 17 press the brake shoe 3 and the brake shoe 4 against the brake drum 6 by expanding the brake shoe 3 and the brake shoe 4. Further, the pivot member 16 and the pivot member 17 move downward in the drawing with respect to FIG.

  The operation of the first embodiment of the present invention will be described. When shifting from the brake-off state to the brake-on state, the motor 10 is rotated, the worm 11 is decelerated from the worm wheel 12 to increase the torque, and the screw shaft 13 is rotated. When the screw shaft 13 rotates, the slider 15 screwed with the screw shaft 13 moves downward in the drawing. When the slider 15 moves, the distance between the holder 14 and the slider 15 decreases, and the link 20, the link 21, the link 22, and the link 23 expand the pivot member 16 and the pivot member 17 in the horizontal direction in the drawing in conjunction with each other. . The pivot member 16 generates a braking force by moving the brake shoe 3 in the left direction of the drawing about the anchor pin 8 and pressing the brake drum 6. Further, the pivot member 17 generates braking force by moving the brake shoe 4 in the right direction of the drawing around the anchor pin 9 and pressing it against the brake drum 6.

  When shifting from the brake-on state to the brake-off state, the motor 10 is reversely rotated to reversely rotate the screw shaft 13. When the screw shaft 13 rotates in the reverse direction, the slider 15 screwed with the screw shaft 13 moves upward in the drawing. When the slider 15 moves, the distance between the holder 14 and the slider 15 increases, and the distance between the pivot member 16 and the pivot member 17 decreases in conjunction with the link 20, the link 21, the link 22, and the link 23. Therefore, due to the rotational force of the motor 10 and the biasing force of the return spring 7, the pivot member 16 moves the brake shoe 3 to the right in the drawing around the anchor pin 8 and separates it from the brake drum 6. Further, the pivot member 17 moves the brake shoe 4 about the anchor pin 9 in the left direction in the drawing and moves away from the brake drum 6. When the brake shoe 3 and the brake shoe 4 are separated from the brake drum 6, the brake is turned off.

  In the drum brake 1 of the present invention, since the screw shaft 13 is disposed in the radial direction of the brake drum 6, the shoe expanding mechanism 2 can be configured in a space-saving manner. The shoe expanding mechanism 2 includes a link 20 that connects the slider 15 and the pivot member 16, a link 21 that connects the slider 15 and the pivot member 17, a link 22 that connects the holder 14 and the pivot member 16, and a holder. The link 23 connecting the pivot member 17 and the pivot member 17 forms a rhombus (square), and the distance between the pivot member 16 and the pivot member 17 is varied in conjunction with the change in the relative position of the slider 15 with respect to the screw shaft 13. It works stably. Further, since the link stroke amount can be set freely, a stable braking force can be maintained.

(Second Embodiment)
FIG. 6 is a cross-sectional view of the drum brake 101 according to the second embodiment of the present invention when the brake is off. The drum brake 101 includes a shoe widening mechanism 102, a brake shoe 3 and a brake shoe 4 widened by the shoe widening mechanism 102, and a back plate 5 having the shoe widening mechanism 102, the brake shoe 3, and the brake shoe 4. And a brake drum 6 that surrounds the shoe spreading mechanism 102, the brake shoe 3, and the brake shoe 4 together with the back plate 5, a brake shoe 3 that is widened when the brake is released, a shoe return spring 7 that pulls back the brake shoe 4, and a brake shoe Anchor pin 8 for fixing 3 to the back plate 5 and anchor pin 9 for fixing the brake shoe 4 to the back plate 5.

  The shoe spreading mechanism 102 is provided in the radial direction of the brake drum 6, and is fixed to the male screw shaft 113 that rotates from the motor 10 (see FIG. 7) via the worm 11 and the worm wheel 12, and the back plate 5. And a holder 114 that allows only rotation of the screw shaft 113, a female screw slider 115A provided above the screw shaft 113, and a female screw provided below the screw shaft 113 on the screw shaft 113 by a reverse screw to the slider 115A. The slider 115B, the pivot member 116 provided on the brake shoe 3, the pivot member 117 provided on the brake shoe 4, the link 120 connecting the slider 115A and the pivot member 116, and the slider 115A and the pivot member 117 are connected. Link 121, slider 115B and pivot member 116 And link 122 for binding, the link 123 for coupling the slider 115B and the pivot member 117, composed of four links. The links 120 and 121 have the same length, and the slider 115A, the pivot member 116, and the pivot member 117 form an isosceles triangle. Similarly, the links 122 and 123 have the same length, and the slider 115B, the pivot member 116, and the pivot member 117 form an isosceles triangle.

  FIG. 7 is a DD cross-sectional view of the drum brake 101 according to the second embodiment of the present invention when the brake is off. The motor 10 is attached to the vehicle body side from the back plate 5, and transmits the power from the connected worm 11 to the worm wheel 12 to rotate the screw shaft 113. The holder 114 holds the screw shaft 113 so that it can rotate and does not move in the axial direction.

  8 is a cross-sectional view of the drum brake 101 according to the second embodiment of the present invention when the brake is on, and FIG. 9 is an EE cross-sectional view of the drum brake 101 according to the second embodiment of the present invention when the brake is on. is there. The motor 10 transmits power from the connected worm 11 to the worm wheel 12 to rotate the screw shaft 113. Compared with FIGS. 6 and 7, the slider 115A moves downward in the drawing, the slider 115B moves upward in the drawing, and the pivot member 116 and the pivot member 117 are interlocked with the brake shoe 3 and the brake shoe, respectively. 4 is expanded in the horizontal direction of the drawing. The pivot member 116 and the pivot member 117 press the brake shoe 3 and the brake shoe 4 against the brake drum 6 by expanding the brake shoe 3 and the brake shoe 4.

  The operation of the second embodiment of the present invention will be described. When shifting from the brake-off state to the brake-on state, the motor 10 is rotated, the worm 11 is decelerated from the worm wheel 12 to increase the torque, and the screw shaft 113 is rotated. When the screw shaft 113 rotates, the slider 115A screwed with the screw shaft 113 moves downward in the drawing, and the slider 115B moves upward in the drawing. When the slider 115A and the slider 115B move, the distance between the slider 115A and the slider 115B decreases, and the link 120, the link 121, the link 122, and the link 123 move in conjunction with the pivot member 116 and the pivot member 117 in the horizontal direction of the drawing. To expand. The pivot member 116 generates a braking force by moving the brake shoe 3 in the left direction of the drawing about the anchor pin 8 and pressing the brake drum 6. The pivot member 117 generates a braking force by moving the brake shoe 4 about the anchor pin 9 in the right direction of the drawing and pressing the brake shoe 4 against the brake drum 6.

  When shifting from the brake-on state to the brake-off state, the motor 10 is reversely rotated and the screw shaft 113 is reversely rotated. When the screw shaft 113 rotates in the reverse direction, the slider 115A screwed with the screw shaft 113 moves upward in the drawing, and the slider 115B moves downward in the drawing. When the slider 115A and the slider 115B move, the distance between the slider 115A and the slider 115B increases, and the distance between the pivot member 16 and the pivot member 17 decreases in conjunction with the link 120, the link 121, the link 122, and the link 123. Become. Therefore, due to the rotational force of the motor 10 and the biasing force of the return spring 7, the pivot member 116 moves the brake shoe 3 in the right direction in the drawing around the anchor pin 8 and separates it from the brake drum 6. Further, the pivot member 17 moves the brake shoe 4 about the anchor pin 9 in the left direction in the drawing and moves away from the brake drum 6. When the brake shoe 3 and the brake shoe 4 are separated from the brake drum 6, the brake is turned off.

  In the drum brake 101 of the present invention, since the screw shaft 113 is arranged in the radial direction of the brake drum 6, the shoe expanding mechanism 102 can be configured with a small space. The shoe spreading mechanism 102 includes a link 120 that connects the slider 115A and the pivot member 116, a link 121 that connects the slider 115A and the pivot member 117, a link 122 that connects the slider 115B and the pivot member 116, and a slider. 115B and the link 123 connecting the pivot member 117 and a rhombus (square) are formed, and the shoe widening mechanism 102 determines the distance between the pivot member 116 and the pivot member 117 to the relative position of the slider 115 with respect to the screw shaft 113. By changing in conjunction with the change, it can operate stably. Further, since the left and right stroke amounts of the link can be freely set, a stable braking force can be maintained.

DESCRIPTION OF SYMBOLS 1 ... Drum brake 2 ... Shoe expansion mechanism 3 ... Brake shoe 4 ... Brake shoe 5 ... Back plate 6 ... Brake drum 7 ... Shoe Return spring 8 ... Anchor pin 9 ... Anchor pin 10 ... Motor 13 ... Screw shaft 14 ... Holder 16 ... Pivot member 17 ... Pivot member 101 ... Drum brake 102 ... Shoe spreading mechanism 113 .. screw shaft 114.. Holder 116.. Pivot member 117.

Claims (4)

Shoe expansion mechanism;
A first brake shoe that is expanded by the shoe expansion mechanism;
A second brake shoe expanded by the shoe expansion mechanism;
A back plate for attaching the shoe spreading mechanism, the first brake shoe, and the second brake shoe;
A brake drum that rotates with a wheel and presses and brakes the first brake shoe and the second brake shoe;
A drum brake comprising:
The shoe spreading mechanism is
A screw shaft of a male screw provided in the radial direction of the brake drum and rotated by a motor;
A holder fixed to the back plate and allowing rotation of the screw shaft;
At least one female screw slider provided on the screw shaft;
A first pivot member provided on the first brake shoe;
A second pivot member provided on the second brake shoe;
A plurality of links that vary the distance between the first pivot member and the second pivot member in conjunction with a change in the relative position of the slider with respect to the screw shaft;
A drum brake characterized by comprising: The plurality of links are:
A link connecting the slider and the first pivot member;
A link connecting the slider and the second pivot member;
A link connecting the holder and the first pivot member;
A link connecting the holder and the second pivot member;
The drum brake according to claim 1, comprising: The plurality of links are:
The slider includes two sliders, a link connecting one slider and the first pivot member,
A link connecting the one slider and the second pivot member;
A link connecting the other slider and the first pivot member;
A link connecting the other slider and the second pivot member;
The drum brake according to claim 1, comprising:   The drum brake according to claim 3, wherein the one slider is a reverse screw with respect to the other slider.

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