JP2007205400A - Disc brake - Google Patents

Abstract

An electric motor and a speed reduction mechanism are reduced in size by improving the efficiency of a rotation / linear motion conversion mechanism, thereby providing a disc brake that contributes to downsizing of the entire caliper.
A rotary shaft 14 driven to rotate by an electric motor and a speed reducer in a housing 13 provided outside the cylinder 8 and a rotation of the rotary shaft 14 in a cylinder 8 provided with a piston 10 are rotated and linearly moved. A screw mechanism 15 that converts and pushes the piston 10 in the propulsion direction is disposed, and the screw mechanism 15 has a structure in which a male screw 20 and a female screw 21 having the same pitch and different effective diameters are engaged with each other. 21 is brought into rolling contact to obtain a minute feed amount obtained by multiplying the relative rotation angle between the male screw 20 and the female screw 21 by the pitch, and the piston 10 driven by hydraulic pressure is fixed at the parking brake position.
[Selection] Figure 1

Description

  The present invention relates to a disc brake used for braking a vehicle.

  A disc brake generally propels a pair of pads arranged on both sides of a disc and a piston slidably arranged in a bottomed cylinder by introducing hydraulic pressure into the cylinder, and The caliper that generates a braking force by pressing the pad against the disc has recently been put into practical use with a parking brake function added thereto.

  Conventionally, as a disc brake to which a parking brake function is added, for example, there is one described in Patent Document 1. This is an electric motor provided outside the cylinder of the caliper, a worm gear mechanism (deceleration mechanism) that increases the rotational torque of the electric motor, and the rotation increased by the worm gear mechanism is converted into a linear motion. A feed screw mechanism (rotation-linear motion conversion mechanism) that presses the piston in the propulsion direction, and the worm moves after releasing the hydraulic pressure in the cylinder after the piston propelled by supplying the hydraulic pressure into the cylinder. The piston functions mechanically to be held at the braking position (parking brake position) by the irreversible action of the gear mechanism and the rotational resistance caused by the friction of the feed screw mechanism.

JP-A-8-244596

  However, since the male screw and female screw having the same effective diameter slide in the feed screw mechanism, the friction loss is large and the efficiency is remarkably lowered. And to operate this low-efficiency rotation-linear motion conversion mechanism. The electric motor and the speed reduction mechanism must be enlarged, and the caliper cannot be increased in size.

  The present invention has been made in view of the above-described conventional problems. The object of the present invention is to reduce the size of the electric motor and the speed reduction mechanism by improving the efficiency of the rotation-linear motion conversion mechanism. The object is to provide a disc brake that contributes to downsizing of the entire caliper.

  In order to solve the above problem, the invention according to claim 1 is characterized in that a pair of pads disposed on both sides of a disk and a piston slidably disposed in a bottomed cylinder are provided in the cylinder. It is driven by a caliper that generates a braking force by pressing the pair of pads against the disc and an electric motor provided outside the cylinder, and the hydraulic pressure into the cylinder In the disc brake having a parking brake mechanism that mechanically holds the piston propelled by supply in the braking position even after the hydraulic pressure in the cylinder is released, the parking brake mechanism increases the torque of the electric motor. A reversible speed reduction mechanism, and a rotation-linear motion conversion mechanism that converts the rotation increased by the speed reduction mechanism into a linear motion and presses the piston in the propulsion direction. Mechanism is characterized in that it consists of a screw mechanism was engaged eccentrically a different male screw and the female screw of the effective diameter pitch is the same.

  According to a second aspect of the present invention, in the first aspect of the present invention, the screw mechanism is configured such that the female screw is disposed coaxially with the cylinder and is movable in the axial direction, and the male screw is disposed on the cylinder. The male screw and the female screw are rotated relative to each other according to the rotation of the rotating shaft by an electric motor, thereby obtaining a feed amount obtained by multiplying the relative rotation angle by a pitch. It is characterized by being able to.

  According to a third aspect of the present invention, in the first aspect of the present invention, the screw mechanism is arranged such that the female screw is disposed so as not to be rotatable coaxially with the cylinder and to be movable in the axial direction, and the male screw is disposed on the cylinder. The internal thread is revolved by an eccentric shaft integrated with a rotating shaft concentric with the shaft, and the male screw rotates according to the rotation of the rotating shaft by the electric motor, thereby multiplying the rotation angle of the male screw by the pitch. The feed amount can be obtained.

  Furthermore, an invention according to claim 4 is characterized in that, in the invention according to any one of claims 1 to 3, the outer diameter of the male screw is larger than the inner diameter of the female screw.

  According to the first aspect of the present invention, the friction loss of the rotation-linear motion conversion mechanism is greatly reduced by the partial contact between the male screw and the female screw constituting the screw mechanism. In combination with the effects of motor torque enhancement and motor rotation speed reduction by the screw mechanism, it is not necessary to increase the size of the electric motor and the speed reduction mechanism, and the overall size of the caliper can be reduced.

  According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, there is no need to prevent rotation of the female screw constituting the screw mechanism. Is easy.

  Further, according to the invention of claim 3, in addition to the effect of the invention of claim 1, high speed reduction is obtained by the rotation of the male screw, so that further reduction in size of the speed reduction mechanism can be achieved.

  Furthermore, according to the invention described in claim 4, in addition to the effect of the invention described in any one of claims 1 to 3, the pulling of the male screw and the female screw is performed even if there is a defect around the screw mechanism. Overhead is maintained, the feed function is not lost, and the reliability of the apparatus is improved.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows a first embodiment as a disc brake with an electric parking brake according to the present invention. The disc brake with electric parking brake (hereinafter referred to as a disc brake with PKB) has a pair of pads 2 and 3 disposed on both sides of the disc rotor 1, and the pair of pads 2 and 3 on both sides of the disc rotor 1. A caliper 4 is provided that generates a braking force by being pressed onto the caliper. The disc brake with PKB is configured as a caliper floating type, and the pair of pads 2 and 3 and the caliper 4 are discs on a carrier (not shown) fixed to a non-rotating portion (for example, a knuckle) of the vehicle. The rotor 1 is supported so as to be movable in the axial direction.

  The caliper body 5 which is the main body of the caliper 4 has a cylinder portion 6 on the base end side facing the pad (inner pad) 2 on the vehicle inner side and a claw portion 7 on the distal end side facing the pad (outer pad) 3 on the vehicle outer side. Each has. A cylinder 8 is formed in the cylinder portion 6 of the caliper body 5, and the opening of the cylinder 8 on the side opposite to the side facing the inner pad 2 is formed by a lid member 9 that is firmly fixed to the rear end of the cylinder portion 6. Closed. The lid member 9 includes a bottom plate portion 9 a that closes the opening of the cylinder 8 and a cylindrical portion 9 b that extends from the bottom plate portion 9 a, and the cylindrical portion 9 b is inserted sufficiently deep into the cylinder 8. . A predetermined gap is formed between the cylindrical portion 9b of the lid member 9 and the inner surface of the cylinder 8, and the piston 10 is slidably disposed in the cylinder 8 using the gap. ing. The piston 10 has a cup shape here, and is housed in the cylinder 8 so that the bottom plate portion 10 a faces the inner pad 2. The space between the cylindrical portion 10b of the piston 10 and the cylinder 8 is sealed by a piston seal 11 disposed on the inner surface of the cylinder 8, whereby the space between the piston 10 and the bottom plate portion 9a of the lid member 9 is liquid. A pressure chamber 12 is defined. The hydraulic pressure chamber 12 is supplied with hydraulic pressure from a hydraulic pressure source (not shown) through a port (not shown) provided in the cylinder portion 6, and the hydraulic pressure is supplied to the hydraulic pressure chamber 12. Accordingly, the piston 10 advances (promotes).

  In the first embodiment, a housing 13 that houses an electric motor and a speed reducer (not shown) constituting the parking brake mechanism is fixed to the back surface of the bottom plate portion 9 b of the lid member 9. Are provided with a rotating shaft 14 and a screw mechanism (rotation-linear motion conversion mechanism) 15 that also constitute a parking brake mechanism. The rotating shaft 14 rotates about the axis C2 eccentric from the axis C1 of the cylinder 8 by δ, and the large-diameter portion 14a at the middle in the axial direction is connected to the lid member via the radial bearing 16 and the thrust bearing 17. 9 is supported. The small-diameter shaft portion 14 a on the proximal end side of the rotating shaft 14 passes through the bottom plate portion 9 a of the lid member 9 and is operatively connected to the speed reducer in the housing 13. The speed reducer includes an irreversible speed reducing mechanism such as a worm gear mechanism, and the rotational torque of the electric motor is increased by the speed reducer and transmitted to the rotating shaft 14.

  On the other hand, the small-diameter shaft portion on the distal end side of the rotating shaft 14 is shared as the male screw 20 constituting the screw mechanism 15. The screw mechanism 15 further includes a female screw 21 that meshes with the male screw 20, and the outer periphery of the female screw 21 rotates around the axis C <b> 1 of the cylinder 8. Are supported via bearings 22. As described above, the rotation center of the male screw 20 is the same as the axis C2 of the rotary shaft 14. Therefore, the rotation center C1 of the female screw 21 and the rotation center C2 of the male screw 20 are set at positions shifted by the eccentric amount δ. Will be. The female screw 21 has an outer diameter set so that the tip of the female screw 21 abuts against the bottom surface of the bottom plate portion 10a of the piston 10, and a thrust bearing 23 is disposed at the tip.

  Here, the male screw 20 and the female screw 21 constituting the screw mechanism 15 are selected to have the same pitch and different effective diameters. More specifically, as shown in FIGS. 2 to 4, the effective radius Rne of the female screw 21 is set larger than the effective radius Rbe of the male screw 20 by the eccentric amount δ (δ = Rne−Rbe). In this case, since the male screw 20 and the female screw 21 rotate without contacting and sliding with a portion of the effective radius, it is the same as the cylinder with the outer radius Rbe rolling and contacting the inner surface of the cylinder with the inner radius Rne. .

  In this case, as shown in FIG. 3, when the male screw 20 makes one rotation, the contact point on the male screw 20 side moves 2πRbe and returns to the original position, but the contact point on the female screw 21 side moves only 2πRbe. Therefore, the rotation is insufficient by 2π (Rne−Rbe). Considering this as a relative rotation angle, it becomes (Rne−Rbe) / Rne, and therefore, the female screw 21 advances with respect to the male screw 20 only by a pitch P × (Rne−Rbe) / Rne. That is, when a male screw and a female screw having the same effective diameter are meshed with each other, the moving amount (feed amount) per rotation is equal to the pitch P, whereas the male screw 20 and the female screw 21 are eccentrically meshed with each other. The feed amount of the mechanism 15 (movement amount of the female screw 21) is a value obtained by multiplying the pitch P by (Rne−Rbe) / Rne, and fine feed is obtained. Further, the rotation of the rotary shaft 14 is decelerated by the relative angle.

  By the way, when a male screw of M11P1.5 and a female screw of M12P1.5 are selected in a metric screw of JIS B0205-1 and meshed with an eccentric amount δ = 0.5 mm, the relative rotation angle (Rne−Rbe) / Rne = 1/11, and the feed amount of the main screw mechanism 15 is reduced to 1/11 as compared with the case where the male screw and the female screw having the same effective diameter are engaged with each other. In this case, when the rotation / linear motion conversion ratio is expressed by (movement amount of female screw 21: L) / (number of rotations of male screw 20: N), the rotation / linear motion conversion ratio L / N is reduced to about 0.091.

  In the main screw mechanism 15, the outer diameter Dbo of the male screw 20 is set larger than the inner diameter Dni of the female screw 21 (Dbo> Dni). FIG. 4 shows the engagement of the male screw 20 and the female screw 21 from the axial direction. As described above, when (Dbo> Dni), the engagement is not caused even when the eccentricity δ is zero (δ = 0). It will remain.

The operation of the disc brake configured as described above will be described below.
When operating as a normal brake, when the hydraulic pressure is supplied from the hydraulic pressure source to the hydraulic pressure chamber 12 in the caliper 4 in response to depression of a brake pedal (not shown), the piston 10 propels and the inner pad 2 is moved to the disc. Press against the rotor 1. On the other hand, the caliper body 5 moves to the inside of the vehicle by the reaction force at this time, and the claw portion 7 presses the outer pad 3 against the other surface of the disk disk rotor 1, whereby the disk rotor 1 is moved by the pair of pads 2, 3. A braking force corresponding to the fluid pressure is generated. Further, when the hydraulic pressure in the hydraulic chamber 12 is released by releasing the brake pedal from this state, the piston 10 is retracted by the elastic restoring force of the piston seal 11, and the pair of pads 2 and 3 are moved to the disc rotor accordingly. The brake is released away from 1.

  In the case of operating as a parking brake, an electric motor (not shown) is rotated in a state where a normal brake is operated (a state in which a braking force is generated) by supplying hydraulic pressure to the hydraulic chamber 12 described above. The rotation of the electric motor is increased by a reduction gear (worm gear mechanism) (not shown) and transmitted to the rotary shaft 14, and the male screw 20 of the screw mechanism 15 rotates together with the rotary shaft 14. Is relatively rotated, and the female screw 21 is finely fed by an amount corresponding to the relative rotation angle (Rne−Rbe) / Rne as described above. Thereby, the front-end | tip of female screw 21 contact | abuts to the inner bottom of piston 10 via the thrust bearing 23, and pushes piston 10 to a propulsion direction. At this time, since the rotation / linear motion conversion ratio of the screw mechanism 15 is small, a large pressing force (thrust) can be obtained even with a small motor torque. Further, since the male screw 20 and the female screw 21 constituting the screw mechanism 15 rotate relative to each other while being in rolling contact with each other, the friction loss of the screw mechanism 15 is greatly reduced, and the efficiency is improved.

  Thereafter, the hydraulic pressure in the hydraulic chamber 12 is released, and at the same time, the electric motor is stopped. Then, the female screw 21 and the male screw 20 constituting the screw mechanism 15 try to rotate relative to each other by the axial force received from the piston 10. However, in this state, the male screw 20 and the female screw 21 are in frictional contact, and the rotation of the rotary shaft 14 integral with the male screw 20 is restricted by a speed reducer (deceleration mechanism). The relative rotation of the internal thread 21 is restricted, so that the backward movement of the female screw 21 is restricted. As a result, the piston 10 is mechanically held at the braking position (parking brake position) as it is.

  To release the parking brake, the hydraulic pressure is once supplied to the hydraulic pressure chamber 12, the piston 10 is added, and the electric motor is rotated in the reverse direction in this state. Then, the female screw 21 and the male screw 20 constituting the screw mechanism 15 are rotated relative to each other in the opposite directions to return to the original position, and then the piston 10 is retracted according to the release of the hydraulic pressure, and the parking brake is released.

  In the first embodiment, the thrust of the screw mechanism 15 as the rotation-linear motion conversion mechanism is increased and the efficiency of the screw mechanism 15 is remarkably improved. Therefore, the electric motor that is a drive source is downsized. Thus, the caliper as a whole can be reduced in size. Moreover, since the screw mechanism 15 also has a speed reduction function, the reduction gear (speed reduction mechanism) on the electric motor side can be downsized. Further, since there is no need to prevent the female screw 21 constituting the screw mechanism 15 from rotating, the structure of the screw mechanism 15 as the rotation-linear motion conversion mechanism is simplified. Furthermore, since the external diameter (diameter between tooth tips) Dbo of the male screw 20 constituting the screw mechanism 15 is set to be larger than the internal diameter (distance between tooth tips) Dni of the female screw 21, the bearings 16, 22 should be used. Even if there is a malfunction, etc., the catch of the screw mechanism 15 remains and the feed function is not lost.

  By the way, when the male screw 20 and the female screw 21 are JIS B0205-1 standard metric screws, as shown in FIG. 5, the screw thread has a mountain shape with an apex angle of 60 degrees. In this case, the virtual height H = √3 / 2 × P, the center of the height is an effective diameter, the outer radius of the male screw 20 is an effective radius + 3/8 × H, and the inner radius of the female screw 21 is an effective radius−1 / 4 ×. H, the nominal diameter of the screw is defined as the outer diameter of the male screw 20. In such an angle screw, not only the apex angle is large, but also the catch height is 5/8 × H, and the center radius of the catch is 1/8 × H larger than the effective radius. For this reason, when the male screw 20 and the female screw 21 are eccentrically engaged with each other as described above, a component force in the radially outward direction (upward in FIG. 2) is generated at the contact point between the two.

  However, the above-mentioned component force in the radial direction can be reduced by selecting a trapezoidal screw having a small apex angle. The one shown in FIG. 6 is a trapezoidal screw of JIS B0216, which is frequently used as a feed screw for machine tools. This trapezoidal screw has an apex angle of 30 degrees, a hook height H1 of 1/2 × P, an external radius of the male screw 20 is an effective radius + 1/2 × H1, and an internal radius of the female screw 21 is an effective radius −1. / 2 × H1, the nominal diameter of the screw is defined as the outer diameter of the male screw 20. When such a trapezoidal screw is employed, the component force in the radial outward direction is reduced to about 1/3 compared to the angle screw shown in FIG.

  On the other hand, when the trapezoidal screw described above is selected, the width on the tip side and the base side is reduced by the amount of the reduced apex angle, and the rigidity is lowered. Considering these points, an asymmetric screw as shown in FIG. 7 is advantageous. This type of asymmetric screw is conventionally used in an adjuster mechanism for a manual parking brake, and the slope on the side that pushes the piston 10 is set to 15 degrees, which is the same as the trapezoidal screw, and the slope on the opposite side is set to 45 degrees. When such an asymmetric screw is employed, the slope on the side that pushes the piston 10 is 15 degrees, which is the same as the trapezoidal screw, so that the above-described component force in the radially outward direction is reduced. Further, since the opposite side slope is set at 45 degrees, in addition to increasing the tip strength, the width of the root is expanded, and the shear strength and rigidity are sufficient.

  FIG. 8 shows a second embodiment of the present invention. In addition, since the whole structure of the disc brake with an electric parking brake as this 2nd Embodiment is the same as what was shown in FIG. 1, the same code | symbol is attached | subjected to the same component and the overlapping description is abbreviate | omitted. . In the second embodiment, the rotating shaft 14 constituting the parking brake mechanism has a small-diameter shaft portion 14a on the base end side via the bearing 30 so that the rotating shaft 14 rotates about the axis C1 of the cylinder 8. It is supported by. In addition, an eccentric shaft 31 that is eccentric by δ from the rotation center C1 is provided in a crank shape on the distal end side of the rotation shaft 14. On the other hand, the male screw 20 of the screw mechanism 15 that also constitutes the parking brake mechanism is formed in a hollow independently of the rotary shaft 14 and supported by the eccentric shaft 31 via a bearing 32 and an angular bearing 33. In the second embodiment, the cylindrical portion 9b of the lid member 9 is formed in a short length so that the tip thereof is located at an intermediate portion of the cylinder 8, and the tip of the cylindrical portion 9b, the male screw 20, A thrust bearing (thrust ball bearing) 34 is interposed between them. The male screw 20 is urged toward the lid member 9 by the angular bearing 33 and restrained in the axial direction, while the thrust bearing 34 ensures free rotation.

  The female screw 21 meshed with the male screw 20 is slidably fitted to the cylindrical portion 9b of the cover member 9 whose base end is formed in the short length. A pin hole 35 is provided in the base end portion of the female screw 21 in the radial direction, and a pin 36 is inserted into the pin hole 35. The tip of the pin 36 is fitted in a guide groove 37 formed by extending in the axial direction on the outer peripheral surface of the cylindrical portion 9b of the lid member 9, so that the female screw 21 cannot rotate and moves in the axial direction. It is supported by the lid member 9 as possible. Further, a bearing 38 is interposed between the tip of the female screw 21 and the tip of the rotary shaft 14, and the deflection of the eccentric shaft 31 integral with the rotary shaft 14 is prevented by this bearing 38.

  As the male screw 20 and the female screw 21 constituting the screw mechanism 15, those having different effective diameters at the same pitch are selected as in the first embodiment, and both are meshed in a rolling contact state. In the second embodiment, when the rotating shaft 14 rotates, the male screw 20 revolves while contacting the female screw 21. At this time, since the rotation of the female screw 21 is restricted, the contact point of the male screw 20 is on the circumference of the radius Rbe by 2π (Rne−Rbe) contrary to the relative movement shown in FIG. The male screw 20 rotates in the direction of rotation by the rotation angle (Rne−Rbe) / Rbe. By the rotation of the male screw 20, the female screw 21 advances by P × (Rne−Rbe) / Rbe.

  Incidentally, if a trapezoidal screw having an outer diameter of 25P2 is selected as the male screw 20 and a trapezoidal screw having an inner diameter of 24P2 is selected as the female screw 21, and they are meshed with an eccentricity δ = 0.5, Rbe = 12, Rne = 12.5. Yes, the rotation angle of the male screw 20 is (Rne−Rbe) / Rbe = 1/24. As a result, the advancement amount of the female screw 21, that is, the feed amount becomes 1/12, and the rotation / linear motion conversion ratio S / N defined as described above becomes as small as about 0.083.

  The operational effects of the second embodiment are the same as those of the first embodiment, but the rotation of the male screw 29 is extremely slow, so that high deceleration can be obtained. Since the high speed reduction is obtained, the reduction gear (speed reduction mechanism) that transmits the rotation of the electric motor to the rotary shaft 14 can be reduced in size.

  The screw mechanism 15 can be applied to a device other than a disc brake (for example, an electric booster) as a rotation-linear motion conversion mechanism, and a decompression mechanism is incorporated even when used for other devices. Therefore, the rotational force of the input can be reduced, the motor and the speed reducer can be downsized, and the equipment can be reduced in size and cost.

It is sectional drawing which shows the whole structure of the disc brake as the 1st Embodiment of this invention. It is typical which shows the meshing structure of the screw mechanism in this disc brake. It is explanatory drawing which shows the rotation-linear motion conversion principle of this screw mechanism. It is a schematic diagram which shows the meshing structure of this screw mechanism from an axial direction. It is a schematic diagram which shows the shape and meshing state of a screw thread when a metric screw is adopted as the male screw and the female screw constituting the main screw mechanism. It is a schematic diagram which shows the shape and meshing state of the thread when a trapezoidal screw is adopted as the male screw and the female screw constituting the main screw mechanism. It is a schematic diagram which shows the shape of a thread and a meshing state when an asymmetrical screw is adopted as a male screw and a female screw constituting the main screw mechanism. It is sectional drawing which shows the whole structure of the disc brake as the 2nd Embodiment of this invention.

Explanation of symbols

1 Disc rotor 2, 3 Pad 4 Caliper 8 Cylinder 10 Piston 13 Housing (for electric motor and reducer interior)
14 Rotating shaft 15 Screw mechanism 20 Male screw 21 Female screw

Claims (4)

  A pair of pads disposed on both sides of the disk and a piston slidably disposed in the bottomed cylinder are propelled by introducing hydraulic pressure into the cylinder, and the pair of pads are used as a disk. A caliper that generates a braking force when pressed and an electric motor provided outside the cylinder operate as a drive source, and a piston that is propelled by supplying hydraulic pressure into the cylinder is mechanically released after the hydraulic pressure in the cylinder is released. In the disc brake having a parking brake mechanism for holding the brake at a braking position, the parking brake mechanism linearly moves the irreversible reduction mechanism that increases the torque of the electric motor and the rotation increased by the reduction mechanism. And a rotation-linear motion conversion mechanism that presses the piston in the propulsion direction, and the rotation-linear motion conversion mechanism has the same pitch and different effective diameters. Disc brake characterized by comprising bets a screw mechanism engaged allowed to eccentrically.   The screw mechanism is arranged such that the female screw can be rotated coaxially with the cylinder and can move in the axial direction, and the male screw is provided on a rotating shaft arranged eccentrically from the axis of the cylinder. 2. A disc brake according to claim 1, wherein the disc brake rotates relative to the rotating shaft of the electric motor in accordance with rotation, thereby obtaining a feed amount obtained by multiplying the relative rotation angle by a pitch.   The screw mechanism is arranged so that the female screw cannot rotate coaxially with the cylinder and can move in the axial direction, and the male screw revolves in the female screw by an eccentric shaft that is integral with a rotation shaft concentric with the cylinder shaft. 2. The disc brake according to claim 1, wherein the male screw rotates in accordance with rotation of a rotating shaft by an electric motor, thereby obtaining a feed amount obtained by multiplying the rotation angle of the male screw by a pitch. The disc brake according to any one of claims 1 to 3, wherein an outer diameter of the male screw is larger than an inner diameter of the female screw.

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