JP2019006267A - Electric booster - Google Patents

Abstract

To provide an electric booster that suppresses an increase in ineffective depressing force while making a difference between depressing force at the initial stage of a brake pedal depressing operation and depressing force at the initial stage of a return operation.SOLUTION: In depressing force at the initial stage of a brake pedal depressing operation, a load required to rotate a nut member 52 is added to a set load of a helical compression spring 53. In depressing force at the initial stage of a brake pedal return operation, the load required to rotate the nut member 52 is subtracted from the set load of the helical compression spring 53. This enables an increase in ineffective depressing force to be suppressed, while making a difference between the depressing force at the initial stage of the brake pedal depressing operation and the depressing force at the initial stage of the return operation.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an electric booster that is incorporated in a vehicle brake device and uses the power of an electric motor as a boosting source.

  Patent Document 1 discloses an electric booster in which the rate of change in resistance force with respect to the stroke of the input rod is changed to reduce the uncomfortable feeling associated with a decrease in pedal reaction force. In this electric booster, since the sliding resistance between the input rod and the sliding member is the same on the stepping side and the return side of the brake pedal, when the initial sliding resistance on the stepping side is increased, the brake pedal It is also necessary to increase the spring force for returning. As a result, the invalid pedaling force of the brake pedal increases, and the initial pedaling force of the brake pedal becomes excessive.

Japanese Unexamined Patent Publication No. 2016-22527

  An object of the present invention is to provide an electric booster that suppresses an increase in an invalid pedaling force while making a difference between a pedaling force at an initial depression of a brake pedal and a pedaling force at an initial return.

  The present invention relates to a booster member driven by an electric motor to propel a piston of a master cylinder, an input rod connected to a brake pedal, and a part of a reaction force from the piston of the master cylinder connected to the input rod. An input plunger that is inserted into the booster member, and the input member includes a screw groove provided on the master cylinder side, A flange portion that is spaced apart from the thread groove toward the brake pedal, and is in axial contact with the boost member on the master cylinder side and rotated by movement of the input member. And a spring member that is supported by the flange portion and biases the nut member toward the master cylinder.

  The electric booster according to the present invention can suppress an increase in invalid pedaling force while making a difference between the initial pedaling force and the initial pedaling force of the brake pedal.

It is sectional drawing by the axial plane of the electric booster which concerns on this embodiment. It is a figure which expands and shows the principal part in FIG.

An embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view of the electric booster 1 according to this embodiment, taken along an axial plane. In the following, for convenience, the left direction and the right direction in FIG. 1 are defined as the front direction (front side) and the rear direction (rear side) in the electric booster 1, and the upward direction and the lower direction in FIG. The upper direction (upper side) and the lower direction (lower side) in FIG.

  Referring to FIG. 1, an electric booster 1 includes an electric motor 2 (electric motor), a housing 3, an input member 4, a hysteresis applying mechanism 5, a rotation / linear motion conversion mechanism 6, a stroke detection device 7, a rotation angle detection device 8, And a controller (not shown). The electric motor 2 is accommodated in the rear housing 23 of the housing 3. The input member 4 includes an input rod 10 and an input plunger 11 and is arranged coaxially with respect to the master cylinder 15. In the input rod 10, the input plunger 11 is connected to the ball joint portion 85 at the front end, and the rear end is connected to the brake pedal 13 via the clevis 90. A part of the reaction force from the primary piston 31 and the secondary piston 32 of the master cylinder 15 is transmitted to the input plunger 11.

  The rotation / linear motion conversion mechanism 6 operates the electric motor 2 in response to the forward movement of the input rod 10 accompanying the operation of the brake pedal 13, thereby thrusting the primary piston 31 and the secondary piston 32 of the tandem master cylinder 15. Assist. The stroke detection device 7 includes a sensor magnet 77 and a hall sensor unit 78, and detects the amount of movement (stroke amount) of the input member 4 (input rod 10 and input plunger 11) relative to the housing 3 as the brake pedal 13 is operated. To do.

  The rotation angle detection device 8 includes a sensor magnet 101 and a sensor unit 102, and detects the rotation angle of the rotation shaft 2A of the electric motor 2. The controller (not shown) is constituted by a microcomputer, and adjusts the relative position between the input member 4 and a propulsion member 110 described later based on detection signals from various sensors such as the stroke detection device 7 and the rotation angle detection device 8. Then, the drive of the electric motor 2 is controlled so that the brake fluid pressure is generated in the primary chamber 37 and the secondary chamber 38 in the master cylinder 15 with a desired boost ratio.

  A reservoir 16 for supplying brake fluid to the master cylinder 15 is attached to the top of the master cylinder 15. The housing 3 includes a rear housing 23 and a front housing 20 that closes a front end opening of the rear housing 23. The front housing 20 is formed with an opening 21 through which the rear end portion of the master cylinder 15 is inserted. The rear housing 23 accommodates the first rear housing portion 23 </ b> A that accommodates the rotation / linear motion conversion mechanism 6, and the second intermediate gear 133 of the torque transmission portion 131 that transmits the rotation from the electric motor 2 to the rotation / linear motion conversion mechanism 6. A rear housing part 23B and a motor housing part 23C for housing the electric motor 2 are provided.

  A cylindrical portion 24 arranged coaxially with respect to the master cylinder 15 is extended at the rear portion of the first rear housing portion 23A. A mounting plate 27 is fixed around the cylindrical portion 24 of the first rear housing portion 23A. A plurality of stud bolts 28 are attached to the attachment plate 27. The electric booster 1 is disposed in the engine room with the input rod 10 protruding from a dash panel (not shown) that is a partition wall between the engine room and the vehicle compartment of the vehicle into the vehicle compartment, and includes a plurality of stud bolts. 28 to secure the dash panel. The motor housing portion 23C is fixed to the second rear housing portion 23B with bolts (not shown).

  The master cylinder 15 is attached to the front surface of the front housing 20. The primary piston 31 of the master cylinder 15 is arranged in the housing 3 through the opening 21 of the front housing 20 at the rear end. The master cylinder 15 is formed with a bottomed cylinder bore 30. A primary piston 31 is disposed on the opening side of the cylinder bore 30. The primary piston 31 has a front portion disposed in the cylinder bore 30 of the master cylinder 15 and a rear portion extending from the cylinder bore 30 of the master cylinder 15 into the housing 3.

  The front part and the rear part of the primary piston 31 are formed in a cup shape having an H-shaped cross section by an axial plane. A spherical recess 35 is formed on the rear surface of the intermediate wall 34 of the primary piston 31. A spherical tip of a pressing rod 142 of an output rod 137 described later is brought into contact with the spherical recess 35. A cup-shaped secondary piston 32 is disposed on the bottom side of the cylinder bore 30. In the cylinder bore 30, a primary chamber 37 is formed between the primary piston 31 and the secondary piston 32, and a secondary chamber 38 is formed between the bottom of the cylinder bore 30 and the secondary piston 32.

  Although not shown, the primary chamber 37 and the secondary chamber 38 of the master cylinder 15 are communicated from the two hydraulic pressure ports of the master cylinder 15 to the hydraulic pressure control unit through two actuation conduits. The hydraulic pressure control unit is communicated with the wheel cylinder of each wheel via four foundation lines. Then, the braking force is generated by supplying the hydraulic pressure of the brake fluid generated in the master cylinder 15 or the hydraulic pressure control unit to the wheel cylinder of each wheel.

  Referring to FIG. 1, the master cylinder 15 is provided with reservoir ports (not shown) for connecting the primary chamber 37 and the secondary chamber 38 to the reservoir 16. On the inner peripheral surface of the cylinder bore 30, annular piston seals 47, 48, 49, 50 that abut against the primary piston 31 and the secondary piston 32 are provided in the front and rear directions in order to divide the cylinder bore 30 into a primary chamber 37 and a secondary chamber 38. Arranged at intervals in the direction.

  The piston seals 47 and 48 are arranged so as to sandwich one (rear) reservoir port (not shown). When the primary piston 31 is in the non-braking position (see FIG. 1), the primary chamber 37 is communicated with one reservoir port via one piston port (not shown) provided on the side wall of the primary piston 31. The When the primary piston 31 moves forward from the non-braking position and one of the piston ports reaches one (front) piston seal 48, the primary chamber 37 is shut off from the one reservoir port by the piston seal 48. A hydraulic pressure is generated in the chamber 37.

  The piston seals 49 and 50 are arranged so as to sandwich the other (front side) reservoir port (not shown). When the secondary piston 32 is located at the non-braking position (see FIG. 1), the secondary chamber 38 is communicated with the other reservoir port via the other piston port (not shown) provided on the side wall of the secondary piston 32. The When the secondary piston 32 moves forward from the non-braking position and the other piston port reaches one (front) piston seal 50, the secondary chamber 38 is blocked from the reservoir port by the piston seal 50, thereby the secondary chamber 38. Hydraulic pressure is generated.

  A primary spring assembly 41 is provided between the primary piston 31 and the secondary piston 32 to determine the distance (interval) between the pistons 31 and 32 in the non-braking state (see FIG. 1). The primary spring assembly 41 includes a compression coil spring 65 that urges the primary piston 31 and the secondary piston 32 in a direction in which they are separated from each other. Inside the compression coil spring 65, an expansion / contraction member 66 whose expansion / contraction length is regulated is provided. The telescopic member 66 includes a retainer guide 67 that is in contact with the intermediate wall 34 of the primary piston 31 and a retainer that has a front end that is in contact with the secondary piston 32 and can move in the retainer guide 67 in the axial direction (front-rear direction). It consists of a rod 68.

  A secondary spring assembly 42 is provided between the bottom of the cylinder bore 30 and the secondary piston 32 to determine the distance (interval) between the bottom of the cylinder bore 30 and the secondary piston 32 in the non-braking state (see FIG. 1). The secondary spring assembly 42 includes a compression coil spring 71 that urges the bottom of the cylinder bore 30 and the secondary piston 32 in a direction to separate them from each other. Inside the compression coil spring 71, there is provided an expansion / contraction member 72 whose expansion / contraction length is restricted. The telescopic member 72 includes a retainer guide 73 whose front end is in contact with the bottom of the cylinder bore 30, and a retainer whose rear end is in contact with the secondary piston 32 and movable in the retainer guide 73 in the axial direction (front-rear direction). Rod 74.

  Inside the cylindrical portion 24 of the first rear housing portion 23A, the input plunger 11 and the propelling member 110 are disposed in order from the radially inner side. The input rod 10 includes a small diameter rod portion 80 and a large diameter rod portion 81 that continuously extends rearward from the small diameter rod portion 80. The small diameter rod portion 80 is reduced in diameter toward the ball joint portion 85 at the front end. The ball joint portion 85 is connected to the spherical recess 100 at the rear end of the input plunger 11. A rear end portion of the large diameter rod portion 81 is connected to the clevis 90. Thereby, when the brake pedal 13 is operated, the input rod 10 moves in the front-rear direction.

  The input plunger 11 includes a first rod portion 91, a small-diameter second rod portion 92 extending forward from the first rod portion 91, and a cylindrical caulking portion 93 extending rearward from the first rod portion 91. On the outer peripheral surface of the first rod portion 91, an annular groove portion 97 to which a stopper 122 described later is attached is formed. A pin member 185 extending from the sensor magnet 77 of the stroke detection device 7 is press-fitted into the input plunger 11. The ratio plate 105 is in contact with the front end face of the second rod portion 92. The ratio plate 105 includes a pressing portion 106 (see FIG. 2) and a rod portion 107 (see FIG. 2) having a smaller diameter than the pressing portion 106. The rear end of the rod portion 107 is in contact with the front end surface of the second rod portion 92 of the input plunger 11. In the ratio plate 105, the rod portion 107 is slidably supported by a cylinder surface 125 (see FIG. 2) formed at the front end portion of the third shaft hole 113 of the propulsion member 110.

  A propelling member 110 (a booster member) is disposed on the outer periphery (radially outer side) of the input plunger 11. The propelling member 110 is supported so as to be movable in the front-rear direction with respect to the cylindrical portion 24 of the first rear housing portion 23A on the radially outer side of the input plunger 11. The propelling member 110 includes a small diameter portion 117 disposed in the cylindrical portion 24 and a large diameter portion 118 extending forward from the small diameter portion 117. The propulsion member 110 includes a first shaft hole 111 that opens to the rear end surface, a second shaft hole 112 that extends forward from the first shaft hole 111 and has a smaller diameter than the first shaft hole 111, and the second shaft hole 112. A third shaft hole 113 extending forward and having a smaller diameter than the second shaft hole 112, a fourth shaft hole 114 extending forward from the third shaft hole 113 and having a larger diameter than the third shaft hole 113, and the fourth A fifth shaft hole 115 that is continuous with the shaft hole 114 and a sixth shaft hole 116 that is continuous with the fifth shaft hole 115 and opens at the front end surface of the propelling member 110 are provided.

  A caulking portion 93 of the input plunger 11 is disposed in the first shaft hole 111 of the propelling member 110. The first rod portion 91 of the input plunger 11 and the base side portion of the second rod portion 92 are disposed in the second shaft hole 112. In the third shaft hole 113, the tip end portion of the second rod portion 92 of the input plunger 11 and the rod portion 107 of the ratio plate 105 are disposed. The pressing portion 106 of the ratio plate 105 is disposed in the fourth shaft hole 114. A reaction disk 135 (to be described later) is disposed in the fifth shaft hole 115. A flange portion 123 is formed on the outer periphery of the front end of the large-diameter portion 118 of the propelling member 110. The propelling member 110 is formed with a stopper groove 120 for inserting a stopper 122 attached to the annular groove portion 97 of the input plunger 11. Thus, the input plunger 11 can move relative to the propelling member 110 in the front-rear direction by the clearance in the front-rear direction between the stopper 122 and the stopper groove 120.

  The entire length (front-rear direction length) of the fourth shaft hole 114 of the propelling member 110 is formed longer than the front-rear direction length of the pressing portion 106 of the ratio plate 105. In a non-braking state (see FIG. 1), a so-called jump-in clearance is provided between the rear end surface of the reaction disk 135 and the top of the pressing portion 106 of the ratio plate 105. A compression coil spring 130 is provided between the front housing 20 and the flange portion 123 of the propulsion member 110 to urge the propulsion member 110 backward. The fifth shaft hole 115 of the propelling member 110 is provided with a substantially disc-shaped reaction disk 135 made of an elastic body such as rubber.

  The output rod 137 includes a disc portion 139 having the same diameter as the reaction disc 135, a rod portion 138 extending from the center of the front end surface of the disc portion 139, and a pressing rod 142 connected to the front end portion of the rod portion 138. . The disc portion 139 is slidably fitted into the fifth shaft hole 115 of the propelling member 110, and the rear end surface is in contact with the reaction disk 135. The front end of the pressing rod 142 formed in a spherical shape is brought into contact with a spherical concave portion 35 provided on the rear surface of the intermediate wall 34 of the primary piston 31.

  The rotation / linear motion conversion mechanism 6 has a function of converting a rotational motion from the electric motor 2 into a linear motion of the sun shaft 147 and applying a thrust to the primary piston 31 via the propelling member 110. The rotation / linear motion converting mechanism 6 includes the above-described sun shaft 147, nut member 145, and a plurality of planetary shafts 146. The nut member 145 is rotatably supported by a bearing 150 provided between the nut member 145 and the housing 3. An inner groove portion 154 that extends in the circumferential direction and is continuously provided at intervals along the axial direction is formed on the rear inner circumferential surface of the nut member 145. A sun shaft 147 is coaxially arranged inside the nut member 145.

  The sun shaft 147 is formed in a cylindrical shape and is supported by the outer periphery of the large-diameter portion 118 of the input plunger 11 so as not to rotate relative to the housing 3 and to be relatively movable in the axial direction (front-rear direction). The front end surface of the sun shaft 147 is in contact with the rear end surface of the flange portion 123 of the propulsion member 110. On the outer peripheral surface of the sun shaft 147, an outer groove portion 155 is formed that extends in the circumferential direction and is continuously provided at intervals along the axial direction. Between the nut member 145 and the sun shaft 147, a plurality of planetary shafts 146 are arranged along the circumferential direction. A plurality of groove portions 156 that are engaged with the inner groove portion 154 of the nut member 145 and the outer groove portion 155 of the sun shaft 147 are formed on the outer peripheral surface of the planetary shaft 146.

  Then, the inner groove portion 154 of the nut member 145 and the groove portion 156 of each planetary shaft 146 are engaged, and the groove portion 156 of each planetary shaft 146 and the outer groove portion 155 of the sun shaft 147 are engaged. As a result, when the nut member 145 rotates, each planetary shaft 146 rotates around its own axis while performing a planetary motion revolving around the axis of the sun shaft 147, and the planetary movement of each planetary shaft 146 causes a sun motion. The shaft 147 moves linearly relative to the housing 3 along the axial direction (front-rear direction).

  The rotating shaft 2A of the electric motor 2 is rotatably supported by a pair of bearings 82 and 83. A torque transmission part 131 that transmits the rotational torque of the electric motor 2 is provided on the rotary shaft 2A. The torque transmission unit 131 is engaged with the external teeth 132 formed at the front end portion of the rotating shaft 2A, the intermediate gear 133 meshed with the external teeth 132, and the intermediate gear 133. And a main gear 134 fixed to the outer peripheral surface of the nut member 145. The rotational torque of the rotating shaft 2A of the electric motor 2 is transmitted to the nut member 145 of the rotation / linear motion converting mechanism 6 via the torque transmission unit 131, that is, the external teeth 132, the intermediate gear 133, and the main gear 134. .

  The controller (not shown) propels the propulsion member 110 of the rotation / linear motion conversion mechanism 6 based on the detection signals of the stroke detection device 7, the rotation angle detection device 8, and various sensors, and achieves a master with a desired boost ratio. It has a function of controlling the operation of the electric motor 2 so as to generate a brake fluid pressure in the primary chamber 37 and the secondary chamber 38 in the cylinder 15.

  With reference to FIG. 2, the hysteresis imparting mechanism 5 will be described. The hysteresis imparting mechanism 5 of the present embodiment has a function of imparting hysteresis to the pedaling force when the brake pedal 13 is depressed (initially depressed) and when it is returned (initially returned). In other words, the hysteresis imparting mechanism 5 changes the resistance force that acts on the input member 4 between the initial stage of advance and the initial stage of reverse of the input member 4 (input rod 10 and input plunger 11). By changing the direction of the resistance force applied to the plunger 11, the electric booster 1 has a function of giving hysteresis characteristics.

  The hysteresis applying mechanism 5 includes a screw portion 51 (screw groove) formed on the master cylinder 15 side (left side in FIG. 2) of the input member 4, a nut member 52 screwed into the screw portion 51, and the nut member. And a compression coil spring 53 (spring member) that urges 52 toward the master cylinder 15. The screw part 51 is formed on the outer peripheral surface of the second rod part 92 of the input plunger 11. The rear end of the compression coil spring 53 is formed between the first rod portion 91 and the second rod portion 92 of the input plunger 11 and is provided apart from the screw portion 51 toward the brake pedal 13. (Flange) can be received. The front end of the compression coil spring 53 is received by the rear end surface 56 of the nut member 52.

  Thereby, the front end surface 55 of the nut member 52 is pressed against the annular surface 57 formed between the second shaft hole 112 and the third shaft hole 113 of the propulsion member 110 with the set load of the compression coil spring 53. The input member 4 starts moving forward when the thrust (depressing force of the brake pedal 13) exceeds the load obtained by adding the set load of the compression coil spring 53 and the load necessary to rotate the nut member 52. Strictly speaking, a force that compresses the compression coil spring 53 acts on the nut member 52 at the initial stage of advancement and backward movement of the input member 4, but here, the force that compresses the compression coil spring 53 in the system is ignore.

  When the input member 4 moves (advances / retreats), the threaded portion 51 has a thread shape, leads, etc. so that the nut member 52 moves relative to the input member 4 in the axial direction while rotating. Specifications are established. When the input member 4 (input plunger 11) moves forward, the nut member 52 rotates while sliding the front end surface 55 on the annular surface 57 of the propulsion member 110. At this time, the nut member 52 is interposed between the nut member 52 and the propulsion member 110. Sliding resistance is generated. Strictly speaking, when the nut member 52 rotates, sliding resistance is also generated between the rear end surface 56 of the nut member 52 and the compression coil spring 53, but here, the nut member 52 and the compression coil spring 53 in the system concerned. Ignore the sliding resistance. For the nut member 52, for example, an oil-free nut made of synthetic resin is used.

Next, the operation of the electric booster 1 described above will be described with reference to FIG.
When the brake pedal 13 is depressed from a non-operating state (see FIG. 1), the input member 4 (the input rod 10 and the input plunger 11) moves forward, and the ratio plate 105 that contacts the input plunger 11 presses the reaction disk 135. . On the other hand, the controller (not shown) is based on the detection result of the movement amount (displacement) of the input member 4 by the stroke detection device 7 and the detection result of the rotation angle of the rotating shaft 2A of the electric motor 2 by the rotation angle detection device 8. The operation of the electric motor 2 (electric motor) is controlled.

  The power of the electric motor 2 is transmitted to the nut member 145 of the rotation / linear motion conversion mechanism 6 via the torque transmission unit 131, that is, the external teeth 132, the intermediate gear 133, and the main gear 134. When the nut member 145 rotates, each planetary shaft 146 revolves around the sun shaft 147 while rotating in a planetary motion, that is, rotating, whereby the sun shaft 147 moves forward. When the sun shaft 147 moves forward, the propelling member 110 moves forward against the spring force of the compression coil spring 130. As a result, the propelling member 110 follows the input member 4 (the input rod 10 and the input plunger 11) and moves forward while maintaining a relative displacement with the input member 4, and the reaction disk via the ratio plate 105. 135 is pressed.

  Thereby, the propulsive force of the input member 4 accompanying the operation of the brake pedal 13 and the propulsive force of the propelling member 110 from the electric motor 2 are transmitted to the output rod 137 via the reaction disk 135. As a result, the output rod 137 moves forward, and the primary piston 31 and the secondary piston 32 of the master cylinder 15 move forward. Thereby, hydraulic pressure is generated in the primary chamber 37 and the secondary chamber 38 of the master cylinder 15, and the brake hydraulic pressure generated in each primary chamber 37 and the secondary chamber 38 is applied to the wheel cylinder of each wheel via the hydraulic pressure control unit. Supplied to generate braking force by friction braking.

  When hydraulic pressure is generated in the master cylinder 15, the hydraulic pressure in the primary chamber 37 and the secondary chamber 38 is received by the ratio plate 105 via the reaction disk 135, and a part of the reaction force due to the hydraulic pressure is input to the input member 4 (input It is transmitted to the brake pedal 13 via the rod 10 and the input plunger 11). At this time, the ratio between the pressure receiving area of the front end surface of the propelling member 110 and the pressure receiving area of the pressing portion 106 of the ratio plate 105 becomes a boost ratio (ratio of hydraulic pressure output to operation input of the brake pedal 13), and is desired. The braking force can be generated.

  When the operation of the brake pedal 13 is released, a controller (not shown) controls the electric motor 2 based on the displacement of the input rod 10 and moves the propelling member 110 backward via the rotation / linear motion conversion mechanism 6. Accordingly, the primary piston 31 and the secondary piston 32 are retracted via the propulsion member 110, the reaction disk 135, and the output rod 137, and the braking force is released by reducing the hydraulic pressure of the master cylinder 15.

  Next, the operation of the hysteresis applying mechanism 5 for making a difference between the initial depression force of the brake pedal 13 (see FIG. 1) and the initial depression force of the return will be described mainly with reference to FIG. When the brake pedal 13 is not operated, the input member 4 is biased toward the brake pedal 13 (the right side in FIG. 2) by the spring force of the compression coil spring 53 (spring member), and is positioned at the initial position with respect to the propulsion member 110. . On the other hand, the nut member 52 is biased toward the master cylinder 15 (left in FIG. 2) by the spring force of the compression coil spring 53, and the front end surface 55 is pressed against the annular surface 57 of the propulsion member 110. In FIG. 2, only the input plunger 11 among the input members 4 including the input rod 10 and the input plunger 11 is displayed.

In the initial stage of depression of the brake pedal 13, the input member 4 has an input load (F1) applied to the input member 4 and a set load (F2) of the compression coil spring 53 and a load (F3) required to rotate the nut member 52. ) And the load (F2 + F3) added to the head, the head moves from the initial position with respect to the propelling member 110 toward the master cylinder 15 and moves forward. In other words, the depression force (F1) of the brake pedal 13 required to advance the input member 4 from the initial position relative to the propelling member 110 is required to rotate the nut member 52 to the set load (F2) of the compression coil spring 53. This is the load with the load (F3) added. That is, (Formula 1) is established.
F1 = F2 + F3 (Formula 1)

Here, the load (F3) required to rotate the nut member 52 in the initial step of depression, in other words, the sliding resistance between the front end surface 55 of the nut member 52 and the annular surface 57 of the propelling member 110 is expressed by (Equation 2). Calculated.
F3 = 2π (T1 / η) (Formula 2)
However,
T1: Torque required to rotate the nut member 52 in the initial step η: Reverse efficiency between the nut member 52 and the threaded portion 51 of the input plunger 11

Here, the torque (T1) required to rotate the nut member 52 is calculated by (Equation 3).
T1 = (F2 + F3) μ × r (Formula 3)
However,
μ: Friction coefficient between the front end surface 55 of the nut member 52 and the annular surface 57 of the propelling member 110 r: Distance from the axis of the input member 4 where the frictional force acts

On the other hand, the pedaling force at the initial return of the brake pedal 13, in other words, the input load (F 4) to the input member 4 required to keep the input member 4 immediately before returning to the initial position with respect to the propelling member 110 is a compression coil spring. The load obtained by subtracting the load (F5) required to rotate the nut member 52 from the set load (F2) of 53. That is, (Formula 4) is established.
F4 = F2-F5 (Formula 4)

Here, the load (F5) required to rotate the nut member 52 in the initial stage of return, in other words, the sliding resistance between the front end surface 55 of the nut member 52 and the annular surface 57 of the propelling member 110 is expressed by (Equation 5). Calculated.
F5 = 2π (T2 / η) (Formula 5)
However,
T2: Torque required to rotate the nut member 52 at the initial stage of return The torque (T2) required to rotate the nut member 52 is calculated by (Equation 6).
T2 = F2 × μ × r (Formula 6)

  Thus, the initial depression force (F1) of the depression of the brake pedal 13 is a load obtained by adding the load (F3) required to rotate the nut member 52 to the set load (F2) of the compression coil spring 53. On the other hand, the pedaling force (F4) at the time of returning the brake pedal 13 is a load obtained by subtracting the load (F5) required to rotate the nut member 52 from the set load (F2) of the compression coil spring 53. Therefore, the load (F3) required to rotate the nut member 52 in the initial depression and the nut member 52 in the initial return are rotated according to the initial depression force (F1) and the initial return force (F4) of the brake pedal 13. It is possible to add a difference (F3 + F5) by adding the load (F5) required for the operation, and to provide hysteresis even in the initial depression of the brake pedal 13 where the hydraulic reaction force of the master cylinder 13 does not act. Is possible.

  In the normal control in which the electric motor 2 operates, the input member 4 (the input rod 10 and the input plunger 11) does not move relative to the propelling member 110 in the axial direction (front-rear direction), so the nut member 52 does not rotate. .

Although the details of the present embodiment have been described above, the operational effects of the present embodiment are described below.
According to the present embodiment, a booster member that is driven by an electric motor to propel the piston of the master cylinder, an input rod that is coupled to the brake pedal, and a reaction force that is connected to the input rod from the piston of the master cylinder. An electric booster comprising: an input plunger that is partially transmitted; and an input member that is inserted inside the booster member, wherein the input member includes a screw groove provided on the master cylinder side, A flange portion that is spaced apart from the thread groove toward the brake pedal, and the thread groove is provided with a nut member that abuts the booster member in the axial direction on the master cylinder side and rotates when the input member moves. The spring member is supported by the flange portion and biases the nut member toward the master cylinder.

  As a result, the initial depression force of the brake pedal is a load obtained by adding the load required to rotate the nut member to the set load of the spring member. On the other hand, the initial depression force of the brake pedal is equal to the set load of the spring member. Therefore, the load obtained by subtracting the load required to rotate the nut member is obtained. Therefore, the sliding resistance at the initial stage of return can be reduced with respect to the sliding resistance at the initial stage of depression of the brake pedal. It is not necessary to increase the load for returning the pedal (spring force), and it is possible to suppress an increase in invalid pedaling force while making a difference between the initial pedaling force and the initial pedaling force of the brake pedal.

DESCRIPTION OF SYMBOLS 1 Electric booster, 2 Electric motor (electric motor), 4 Input member, 10 Input rod, 11 Input plunger, 13 Brake pedal, 15 Master cylinder, 31 Primary piston, 32 Secondary piston, 51 Thread part (thread groove), 52 Nut member, 53 compression coil spring (spring member), 54 spring receiving portion (flange portion), 110 propulsion member (boost member)

Claims (1)

A booster member driven by an electric motor to propel the piston of the master cylinder;
An input rod connected to the brake pedal, and an input plunger connected to the input rod to which a part of the reaction force from the piston of the master cylinder is transmitted, and is inserted through the booster member Members,
An electric booster comprising:
The input member has a thread groove provided on the master cylinder side, and a flange portion provided spaced from the thread groove toward the brake pedal side,
The screw groove is provided with a nut member that abuts on the master cylinder side in the axial direction with the boost member and rotates by movement of the input member,
An electric booster comprising a spring member supported by the flange portion and biasing the nut member toward the master cylinder.

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