JP2007098969A - Electric booster - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric booster capable of supplying working fluid to a load from a master cylinder in accordance with necessary condition of the load. <P>SOLUTION: A speed reducing mechanism 9A to increase a speed reducing ratio when load torque to be transmitted to a booster piston 8 from an output piston 6 is lower than standard torque (1.0) and to decrease the speed reducing ratio when it is higher is provided between a motor and the booster piston 8. It is possible to speedily supply brake fluid to the master cylinder 4 at an initial pressing stage of a piston 5 and to adjust moving speed and a pressing degree of the piston 5 of the master cylinder 4 in accordance with the load torque as large torque is applied on the piston 5 at a later pressing stage. Consequently, it is possible to perform supply of the brake fluid (working fluid) to the load (wheel cylinder) from the master cylinder 4 in accordance with the necessary state of the load. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric booster used for a brake mechanism of an automobile.

  As an example of a conventional electric booster, there is an electric booster 1 shown in FIG. 6A (see Patent Document 1). 6A, the electric booster 1 includes an input member 3 that moves forward and backward by operating the brake pedal 2, and a piston 5 (primary piston 5a and secondary piston) of the master cylinder 4 as the input member 3 moves forward and backward. An output piston 6 that presses the piston 5 b), and a booster piston 8 that presses the output piston 6 by the motor 7 according to the forward and backward movement of the input member 3 are provided. Between the motor 7 and the booster piston 8, a reduction mechanism 9 having a constant reduction ratio using gears and a rotation / linear motion conversion mechanism 10 are interposed.

In the electric booster 1, when an input from the brake pedal 2 is applied to the input member 3, the motor 7 rotates (forward) in one direction according to the input from the input member 3. The rotation of the motor 7 is decelerated by the speed reduction mechanism 9, converted to a linear motion by the rotation / linear motion conversion mechanism 10, applies thrust to the master cylinder 4, and generates brake fluid pressure. The brake fluid pressure generated in the master cylinder 4 is transmitted to the wheel cylinder 12 of the wheel brake 11 to generate a braking force.
At this time, the rotational speed of the motor 7 is reduced using the speed reduction mechanism 9 to increase the torque transmitted to the output piston 6.

Further, the wheel cylinder 12 and the master cylinder 4 of the wheel brake 11 generate a nonlinear reaction force (thrust, load torque) as shown in FIG. 6B, for example, with the generation of the braking force. As shown in FIG. 6B, this non-linear reaction force (thrust) is relatively small in the small stroke range (initial press of the master cylinder 4), and is in the large stroke range (late stage of the master cylinder 4 press). ) Will be bigger.
The motor 7 is required to generate a torque commensurate with the nonlinear reaction force (thrust force, load torque) shown in FIG. 6B, for example.
JP-A-6-183330

By the way, when the master cylinder 4 (piston 5) is pressed, it is necessary to move the piston 5 quickly to send a large amount of brake fluid to the wheel cylinder 12 at the initial pressing stage. In this case, the rotational speed of the motor 7 is not decelerated (the reduction ratio is set to a large value), and the output torque of the motor 7 is transmitted to the output piston 6 (output member) side (the rotational speed is large). desired.
On the other hand, as shown in FIG. 6B, it is necessary to apply a large thrust to the wheel cylinder 12 so that a large reaction force can be dealt with in the latter half of pressing. In this case, it is desired that the rotational speed of the motor 7 is reduced (the reduction ratio is set to a small value), and the output torque of the motor 7 is transmitted to the output piston 6 side (the supplied torque is large). .
For this reason, in the above prior art using the speed reduction mechanism 9 with a constant damping ratio, the above-mentioned matters (the rotation speed is large) desired at the initial pressing of the master cylinder 4 and the above-mentioned matters (supplied at the latter half of the pressing) are supplied. It was not possible to respond to the large torque).

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electric booster capable of supplying a working fluid from a master cylinder to a load according to a necessary condition of the load.

According to the first aspect of the present invention, there is provided an input member that moves forward and backward by operating a brake pedal, an output member that presses a piston of a master cylinder as the input member moves forward and backward, and an output member that moves the input member forward and backward. In the electric booster comprising a transmission member that is pressed by an electric rotary actuator in accordance with movement, a load torque transmitted from the output member to the transmission member is between the electric rotary actuator and the transmission member. A speed reduction mechanism that changes the speed reduction ratio accordingly is provided.
According to a second aspect of the present invention, in the electric booster according to the first aspect, the speed reduction mechanism performs the operation of changing the speed reduction ratio so that the speed reduction ratio decreases when the load torque increases. It is characterized by that.

According to a third aspect of the present invention, in the electric booster according to the first or second aspect, the reduction mechanism includes a planetary gear mechanism that receives torque input from the electric rotary actuator and outputs the input to the transmission member side. And a torque limiter that performs the operation of changing the reduction ratio in cooperation with the planetary gear mechanism.
According to a fourth aspect of the present invention, in the electric booster according to the third aspect, the reduction mechanism is provided with a one-way clutch on the driven side of the planetary gear mechanism.

  According to the first to fourth aspects of the present invention, the speed reduction mechanism that changes the speed reduction ratio according to the load torque transmitted from the output member to the transmission member is provided between the electric rotary actuator and the transmission member. Therefore, the moving speed and the degree of pressing of the piston of the master cylinder can be adjusted according to the load torque, whereby the working fluid can be supplied from the master cylinder to the load according to the required load condition.

Hereinafter, an electric booster according to a first embodiment of the present invention will be described with reference to FIGS. In addition, the member equivalent to the member shown in FIG. 6 attaches | subjects the same code | symbol, and abbreviate | omits the description suitably.
1 to 3, an electric booster 1 </ b> A includes an input member 3 that is slidably guided by a case 16 held on a front wall 15 of a passenger compartment of an automobile by operation of a brake pedal 2, and an input member 3. Is provided between the output piston 6 (output member) that presses the piston 5 (primary piston 5a and secondary piston 5b) of the master cylinder 4 (tandem master cylinder), and the input member 3 and output piston 6. And a reaction disc 17 having elasticity.

The electric booster 1 </ b> A further drives a booster piston 8 (transmission member) that presses the output piston 6 via the reaction disk 17 by receiving the force generated by the motor 7 (electric rotary actuator), and the motor 7. And a potentiometer 18 that obtains a detection signal used for calculating the drive signal by detecting the relative movement between the booster piston 8 and the input member 3.
The input member 3 is roughly composed of an input shaft 20 connected to the brake pedal 2 and a substantially shaft-shaped input piston 21 whose base end side is connected to the input shaft 20. The tip end of the input piston 21 is in contact with the center portion of the end face of the reaction disk 17. The input piston 21 has a smaller diameter on the distal end side (hereinafter referred to as the input piston distal end shaft portion 22) than on the proximal end side (hereinafter referred to as the input piston proximal end shaft portion 23).

  The reaction disk 17 transmits the reaction force (load torque) from the primary piston 5a to the input member 3 and the booster piston 8. The reaction force (load torque) transmitted to the booster piston 8 is transmitted to the speed reduction mechanism output shaft 26 via the feed screw mechanism 25. The reaction force (load torque) transmitted to the speed reduction mechanism output shaft 26 is used to adjust the speed reduction ratio GH of the speed reduction mechanism 9A. In the present embodiment, as described above, the reaction force (load torque) transmitted from the primary piston 5a to the speed reduction mechanism output shaft 26 via the feed screw mechanism 25 is transmitted from the output member to the transmission member. Load torque ".

  In the booster piston 8, a hole 27 having an inner peripheral shape substantially conforming to the outer peripheral shape of the reaction disk 17 is formed in the surface portion on the output piston 6 side (the surface portion on the left side in FIG. 3). Contains a reaction disk 17. On the opening side of the hole 27, a large-diameter portion (hereinafter, referred to as an output piston large-diameter portion 28) formed at one end of the output piston 6 is stored side by side with the reaction disk 17. The output piston large-diameter portion 28 has an outer peripheral shape that substantially conforms to the inner peripheral shape of the hole 27.

The potentiometer 18 detects the relative displacement amount of the input piston 21 and the booster piston 8 by a voltage output having a magnitude corresponding to the relative displacement amount, and outputs it to the controller 29 as a detection signal.
The controller 29 estimates an input thrust applied to the input member 3 based on the detection signal of the potentiometer 18 and obtains a drive signal based on the input thrust. The controller 29 outputs the drive signal to the motor 7 to drive it, and controls the booster piston 8 to generate a booster thrust having a magnitude corresponding to the drive signal via the feed screw mechanism 25 shown in FIG. Like to do.
Between the motor 7 and the booster piston 8, there is a speed reduction mechanism 9A in which the speed reduction ratio GH changes according to the load torque transmitted from the output piston 6 to the booster piston 8, and a feed screw mechanism 25 that performs rotation / linear motion conversion. Intervened.

  The feed screw mechanism 25 includes a male screw portion 25a provided on the distal end side of the speed reduction mechanism output shaft 26, and a nut portion 25b screwed into the male screw portion 25a. The nut portion 25 b is fixed to the booster piston 8. When the speed reduction mechanism output shaft 26 is rotated in one direction (when viewed from the left side in FIGS. 1 and 2, the feed screw mechanism 25 rotates in the clockwise direction, hereinafter referred to as the forward rotation direction), the nut portion 25 b is moved leftward in FIG. 2. When the speed reduction mechanism output shaft 26 is reversed, the nut portion 25b is moved rightward in FIG.

As shown in FIGS. 1 and 2, the speed reduction mechanism 9A receives an input of torque generated by the motor 7 from a rotation shaft of the motor 7 (hereinafter referred to as a motor rotation shaft 7a), and inputs the input to the speed reduction mechanism output shaft 26. A planetary gear mechanism 30 that outputs to the feed screw mechanism 25 (transmission member side), a torque limiter 31 that cooperates with the planetary gear mechanism 30 to change the reduction ratio GH, and a one-way clutch 32. Yes.
The speed reduction mechanism 9 </ b> A has a housing 33 that is fixed to the case 16. A planetary gear mechanism 30 and a one-way clutch 32 are disposed in the housing 33.
The housing 33 has a substantially plate-like housing substrate portion 33a that rotatably supports the motor rotation shaft 7a via a bearing 34, and a substantially U-shaped cross section, and forms a space portion between the housing substrate portion 33a. And a housing hat portion 33b held by the housing substrate portion 33a. A hole 35 is formed in the housing hat portion 33b at a portion facing the bearing 34 of the housing substrate portion 33a, and a bearing 36 is disposed in the hole 35. The speed reduction mechanism output shaft 26 is rotatably supported by the housing hat portion 33b via a bearing 36.

  The planetary gear mechanism 30 includes a small gear 37 fixed to the tip of the motor rotating shaft 7a, four planetary gears 40 supported by a shaft member 39 fixed to the planetary ring 38, and an internal gear. And an annular large gear 41 that is screwed so that the planetary gear 40 can revolve. The planetary ring 38 includes an annular wall portion 42 and a bottom plate portion 43 that closes one opening (right side in FIG. 1) of the annular wall portion 42 and has a substantially U-shaped cross section together with the annular wall portion 42. Yes. On the outside of the bottom plate portion 43, the speed reduction mechanism output shaft 26 is connected upright.

  A one-way clutch 32 is provided between the housing hat portion 33b and the large gear 41 (corresponding to the driven side in the planetary gear mechanism of claim 4). The one-way clutch 32 has a function of allowing rotation of the large gear 41 in the clockwise direction while prohibiting rotation in the opposite direction (counterclockwise direction) when viewed from the left side in FIG.

  A torque limiter 31 including a friction plate 44 and a spring member 45 is interposed between the small gear 37 and the bottom plate portion 43 of the planetary ring 38. In the torque limiter 31, a reference torque TL0 is set in advance. The torque limiter 31 changes the degree of connection between the small gear 37 and the planetary ring 38 in accordance with the difference in magnitude between a load torque Ts and a reference torque TL0, which will be described later, and according to this, cooperates with the planetary gear mechanism 30. The speed reduction ratio GH of the speed reduction mechanism 9A is changed. In the present embodiment, when the load torque Ts is less than the reference torque TL0 (Ts <TL0), the reduction ratio GH is set to 1.0. In other words, the speed reduction mechanism output shaft 26 rotates at the same speed as the small gear 37 (motor rotation shaft 7a). Further, when the torque is not less than the reference torque TL0 (Ts ≧ TL0), the reduction ratio GH is reduced (reduction ratio GH = 1 / α, α> 1, α: coefficient). That is, the speed reduction mechanism output shaft 26 rotates at a lower speed than the small gear 37 (motor rotation shaft 7a), and an output corresponding to a large load torque Ts is output from the speed reduction mechanism output shaft 26.

  When the load torque Ts <the reference torque TL0, the degree of connection between the small gear 37 and the planetary ring 38 is strong, and when the motor 7 is rotating forward, the small gear 37, the planetary gear 40, the large gear 41, and the planetary ring 38 (including the speed reduction mechanism output shaft 26) are integrally rotated at the same speed as the motor rotation shaft 7a in the forward rotation direction, that is, the speed reduction ratio GH is 1.0. In this case, the planetary gear 40 does not rotate. Further, the planetary gear 40 rotates integrally with the small gear 37 as described above and does not revolve accurately.

When the load torque Ts gradually increases and exceeds the reference torque TL0, the torque limiter 31 slips, and a force in the reverse direction acts on the large gear 41. Further, when the load torque Ts exceeds the reference torque TL0, the one-way clutch 32 prohibits the large gear 41 from rotating in the reverse direction, and the large gear 41 is stopped.
Therefore, the planetary gear 40 rotates and has a reduction ratio GH (reduction ratio GH = 1 / α, α> 1) determined by the gear ratio of each gear, and the planetary ring 38 and the reduction mechanism output shaft 26 are in the same direction (normal Rotation direction). The rotational speed of the speed reduction mechanism output shaft 26 is decelerated at the moment when the torque limiter 31 starts to slip, but the slip torque of the torque limiter 31 is also transmitted to the speed reduction mechanism output shaft 26, so that the output from the speed reduction mechanism output shaft 26 continues. Done. In this state, when the current supplied to the motor 7 is made constant, the output torque of the motor 7 and the load torque Ts are balanced [(output torque of the motor 7) × α = load torque Ts]. The rotation of the motor rotating shaft 7a) stops.

  In the electric booster 1A having the above configuration, the brake pedal 2 is stepped on, and the thrust from the input rod 20 (the input thrust Fi) is transmitted to the output piston 6 via the reaction disk 17. On the other hand, at this time, the controller 29 rotates the motor 7 in accordance with the detection signal from the potentiometer 18 and the drive signal obtained based on the input thrust estimated from the detection signal, whereby the feed screw mechanism 25 is driven and the booster is driven. The booster thrust is transmitted to the output piston 6 via the reaction disk 17 by the piston 8. Accordingly, the output piston 6 applies (presses) the total thrust (output thrust) obtained by adding the input thrust and the booster thrust to the primary piston 5a of the tandem master cylinder 4.

  In the initial pressing stage where the output piston 6 presses the primary piston 5a, the load torque Ts is less than the reference torque TL0 (Ts <TL0). At this stage, the small gear 37 and the planetary ring 38 are strongly connected. As described above, the rotation of the motor rotation shaft 7a is performed from the reduction mechanism output shaft 26 at a reduction ratio GH of 1.0. Accordingly, the output piston 6 is rapidly moved forward. For this reason, the brake fluid is quickly supplied to the wheel cylinder 12 by the primary piston 5 a of the master cylinder 4 pressed by the output piston 6.

Further, the pressing against the primary piston 5a proceeds, and in the latter half of the pressing, the load torque Ts becomes equal to or higher than the reference torque TL0 (Ts ≧ TL0). Then, as described above, the speed reduction mechanism 9A decreases the speed reduction ratio GH (speed reduction ratio GH = 1 / α, α> 1) and rotates the speed reduction mechanism output shaft 26 at a low speed to meet the increased load torque Ts. In addition, a large torque is generated from the output shaft 26 of the speed reduction mechanism so that a good brake operation can be performed. In this state, when the current supplied to the motor 7 is set to a certain magnitude, the rotation of the motor 7 (motor rotating shaft 7a) is stopped in balance with the output torque of the motor 7 × α = the load torque Ts.
As described above, the brake fluid can be quickly supplied to the master cylinder 4 in the initial stage of pressing the piston, and a large torque is applied to the piston 5 (primary piston 5a and secondary piston 5b) in the latter stage of pressing. The moving speed and the degree of pressing of the piston 5 of the master cylinder 4 can be adjusted according to the torque, whereby the supply of brake fluid (working fluid) from the master cylinder 4 to the load [wheel cylinder 12 (see FIG. 6)] Can be fulfilled according to the required situation.

  As described above, the current supplied to the motor 7 is made constant, and the output torque and load torque Ts of the motor 7 are balanced [(output torque of the motor 7) × α = load torque Ts]. When the rotation of the motor rotating shaft 7a) is stopped and the pedal 2 (input member 3) is returned by detecting the detection signal of the potentiometer 18 and the current supplied to the motor 7 is slightly reduced, the wheel cylinder 11 The reduction mechanism output shaft 26 and the planetary ring 38 are urged in the reverse direction by the return force of the brake pad on the side and the return of caliper elastic deformation and the load torque Ts such as a return spring (both not shown) in the master cylinder 4. . However, since the large gear 41 cannot be reversed by the one-way clutch 32, both the motor rotation shaft 7a and the speed reduction mechanism output shaft 26 remain stopped by the frictional force of the torque limiter 31. When the supply current to the motor 7 is further reduced, the motor 7 is forcibly increased by the load torque Ts to the rotational speed xα of the speed reduction mechanism output shaft 26 and reversely rotated, so that the load torque Ts is the reference of the torque limiter 31. Stops when torque is less than α. For this reason, the primary piston 5a is gradually returned to the initial position direction. Further, in order to return the primary piston 5a to the initial position direction, if a small reverse current is supplied to the motor 7, the reduction mechanism output shaft 26 rotates reversely while the torque limiter 31 slips, so that the primary piston 5a is moved to the initial position. It can be returned to (no load position).

Next, an electric booster according to a second embodiment of the present invention will be described with reference to FIG.
The electric booster 1B according to the second embodiment has the following items (1) to (6) as compared to the electric booster 1A (FIGS. 1 to 3) according to the first embodiment. Mainly different.
(1) A speed reduction mechanism 9B is provided instead of the speed reduction mechanism 9A.
(2) The large gear 41 is fixed to the housing 33.
(3) The planetary ring 38B is configured by eliminating the bottom plate portion 43 of the electric booster 1A, so that the four planetary gears 40 can rotate on the shaft member 50 fixed to the annular wall portion 42 of the planetary ring 38B. Be supported.
(4) The speed reduction mechanism output shaft 26 is connected to the ring member 51 instead of the planetary ring 38 of the first embodiment, and the ring member 51 is connected to the ring member annular wall 51a and the ring member annular wall 51a. And a ring member bottom plate portion 51b connected to the ring member annular wall portion 51a so as to cover one of the openings.
(5) The one-way clutch 32 is moved between the annular wall portion 42 of the planetary ring 38B and the ring member annular wall portion 51a (the speed reduction mechanism output shaft 26).
(6) The torque limiter 31 (the friction plate 44 and the spring member 45) is provided between the small gear 37 and the ring member bottom plate portion 51b in place of the small gear 37 and the bottom plate portion 43 of the planetary ring 38. thing.

In the electric booster 1B according to the second embodiment, similarly to the electric booster 1A according to the first embodiment, the reduction ratio GH is switched, and the master cylinder 4 is in the initial stage of piston pressing. Brake fluid can be supplied quickly, and a large torque is applied to the piston in the latter stage of pressing, so that the moving speed and pressing degree of the piston 5 of the master cylinder 4 can be adjusted according to the load torque. Brake fluid (working fluid) can be supplied to the load [wheel cylinder 12 (see FIG. 6)] according to the required load condition. Further, when the load is low, the motor rotating shaft 7a and the speed reduction mechanism output shaft 26 Rotates at a constant speed, the planetary gear 40 rotates, and the planetary ring 38A rotates at a reduced speed. This point is different from the electric booster according to the first embodiment.

Next, an electric booster according to a third embodiment of the present invention will be described with reference to FIG.
The electric booster 1C according to the third embodiment is mainly different from the electric booster 1B (FIG. 4) according to the second embodiment in the following items (11) to (14). ing.
(11) A speed reduction mechanism 9C is provided instead of the speed reduction mechanism 9B.
(12) The electromagnet 55 is provided on the outer peripheral portion of the housing 33, and the electromagnet 55 operates the plunger 55a inserted into the housing 33, thereby fixing (locking) the large gear 41 to the housing 33 and releasing it. What I did.
(13) The motor rotating shaft 7a is inserted into the small gear 37 and fixed to the small gear 37, the tip is inserted inside the output shaft side annular wall portion 42, and the annular body 56 is connected to the tip.
(14) A torque limiter 31C instead of the torque limiter 31 of the second embodiment is interposed between the annular body 56 and the output shaft side annular wall portion 42, and the torque limiter 31C is wound around the annular body 56. It is constituted by an annular body mounting spring 57 and a spring engaging shaft 58 which is fixed to the ring member annular wall portion 51 a and provided so that the tip portion reaches the annular body 56.

In the electric booster 1C according to the third embodiment, similarly to the electric boosters 1A and 1B according to the first and second embodiments, the reduction ratio GH is switched, and the master cylinder 4 has a piston. In the initial stage of pressing, brake fluid can be supplied quickly, and in the latter stage of pressing, a large torque is applied to the piston 5 (primary piston 5a and secondary piston 5b). The moving speed and the degree of pressing can be adjusted, whereby the brake fluid (working fluid) can be supplied from the master cylinder 4 to the load [wheel cylinder 12 (see FIG. 6)] according to the load necessary condition.
Further, when the electric booster 1C fails or when power is not supplied, the large gear 41 is unlocked by the electromagnet 55 with respect to the housing 33 and the large gear 41 is idled, so that the reduction mechanism output shaft 26 rotates. Since it is not transmitted to the motor 7, even when the booster piston 8 is operated together with the input member 3 by an operation by human power, the motor 7 can be prevented from becoming a load. Further, in the electric booster 1C, the torque limiter 31C is changed to a type using a spring (annular body mounting spring 57) and a shaft (spring engagement shaft 58), and the rotation of the input shaft 20 is rotated in one direction. Then, the diameter of the spring (annular body mounting spring 57) is reduced and wraps around the shaft (spring engaging shaft 58), and the spring (annular body mounting spring 57) is rotated in the other direction. Since it slides on the shaft 58), the slip start torque can be switched by forward and reverse rotation. Although illustration is omitted, if the torque limiter 31C is electromagnetically released, the speed reduction mechanism output shaft 26 can be rotated completely freely.

It is sectional drawing which shows typically the reduction device of the electric booster which concerns on 1st Embodiment of this invention. FIG. 2 is a sectional view schematically showing the electric booster of FIG. 1 including a master cylinder, a brake pedal, and a controller. It is sectional drawing which shows typically the booster piston used for the electric booster of FIG. 1 and its vicinity part. It is sectional drawing which shows typically the electric booster which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows typically the electric booster which concerns on 3rd Embodiment of this invention. An example of a conventional electric booster is shown, (a) is a cross-sectional view schematically showing the electric booster, and (b) is a diagram showing thrust-stroke characteristics of the electric booster. .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A-1C ... Electric booster, 3 ... Input member, 6 ... Output piston (output member), 7 ... Motor (electric rotary actuator), 8 ... Booster piston (transmission member), 9A ... Deceleration mechanism, 30 ... Planetary gear Mechanism, 31 ... torque limiter, 32 ... one-way clutch.

Claims (4)

An input member that moves forward and backward by operating the brake pedal;
An output member that presses the piston of the master cylinder as the input member moves forward and backward;
An electric booster comprising: a transmission member that presses the output member with an electric rotary actuator in accordance with advancing and retreating movement of the input member;
An electric booster characterized in that a reduction mechanism is provided between the electric rotary actuator and the transmission member so that a reduction ratio changes according to a load torque transmitted from the output member to the transmission member.   2. The electric booster according to claim 1, wherein the speed reduction mechanism performs the changing operation of the speed reduction ratio so that the speed reduction ratio decreases when the load torque increases.   The reduction mechanism includes a planetary gear mechanism that receives an input of torque from the electric rotary actuator and outputs the input to the transmission member side, and a torque limiter that performs a change operation of the reduction ratio in cooperation with the planetary gear mechanism. The electric booster according to claim 1 or 2, characterized by comprising: 4. The electric booster according to claim 3, wherein the speed reduction mechanism is provided with a one-way clutch on the driven side of the planetary gear mechanism.

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