JP5257639B2 - Electric booster - Google Patents

Description

  The present invention relates to a booster used for a brake mechanism of an automobile, and more particularly to an electric booster that uses an electric actuator as a booster source.

  Conventionally, as this type of electric booster, there is one described in Patent Document 1. An input member that moves forward and backward by the operation of the brake pedal, an output member that is disposed so as to be relatively movable with the input member, and is driven by an electric actuator, and a neutral position of relative displacement when the brake is not operated. It has a structure provided with a pair of spring members to hold. In such an electric booster, the input member and the output member are relatively displaced to generate a brake fluid pressure in the master cylinder, thereby enabling a brake assist operation and a regenerative cooperative operation.

JP 2007-191133 A

  By the way, in the above-described electric booster, the brake fluid pressure generated in the master cylinder changes nonlinearly with respect to the relative displacement amount between the input member and the output member. On the other hand, the spring force generated by the pair of spring members that hold the input member and the output member at the neutral positions of the relative displacements changes linearly with respect to the relative displacement amount. For this reason, the hydraulic pressure fluctuation in the master cylinder described above is directly transmitted as a reaction force to the brake pedal via the input member, causing the pedal pedal fluctuation and vibration (pedal vibration) to give the driver a sense of incongruity. there were.

  The present invention has been made in view of the above-described problems, and the problem is to effectively suppress the pedal pedal force fluctuation and the pedal vibration accompanying the hydraulic pressure fluctuation in the master cylinder, and to improve the pedal performance. An object of the present invention is to provide an electric booster capable of ensuring a feeling.

In order to solve the above problems, an electric booster of the present invention includes an input member that moves forward and backward by an operation of a brake pedal, an output member that is arranged to be relatively movable with the input member, and is driven by an electric actuator , master by the pair of spring members which the input member and the output member is held at the neutral position of relative displacement when the brake is inoperative, comprises a, to control the relative displacement of the output member with respect to the movement of said input member In the electric booster that generates a desired brake fluid pressure in the cylinder, any one of the pair of spring members is relatively displaced between the input member and the output member, and the output is performed by the input member. The free length is reached in the process until the movement of the member is restricted .

According to the present invention , the reaction force fluctuation accompanying the hydraulic pressure fluctuation in the master cylinder can be canceled out by the non-linear fluctuation of the spring force of the pair of spring members. And a good pedal feel can be secured. Further, since only a slight change is made to the pair of spring members that hold the input member and the output member at the neutral positions of the relative displacements, the apparatus cost does not increase specially .

It is sectional drawing which shows the whole structure of the electric booster as one Embodiment of this invention. It is sectional drawing which expands and shows the principal part of this electric booster. It is a conceptual diagram for demonstrating the pressure balance in this electric booster. It is a schematic diagram which shows the Example which employ | adopted the nonlinear spring for one of a pair of spring member with which this electric booster is equipped. It is a schematic diagram which shows the Example which employ | adopted the nonlinear spring as both of a pair of spring member. It is a schematic diagram which shows the other Example which employ | adopted the nonlinear spring for one side of a pair of spring member. It is a schematic diagram which shows the further another Example which employ | adopted the nonlinear spring for one side of a pair of spring member. It is a schematic diagram which shows the Example which employ | adopted the different kind of nonlinear spring for both of a pair of spring members. It is a schematic diagram which shows the other Example which employ | adopted the nonlinear spring of a different kind to both of a pair of spring member. It is a schematic diagram which shows the further another Example which employ | adopted the non-linear spring of a different kind to both of a pair of spring member. It is a schematic diagram which shows the Example which designs the free length of a pair of spring member with which this electric booster is equipped, and provides nonlinearity. It is a schematic diagram which shows the other Example which designs the free length of a pair of spring member, and provides nonlinearity.

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

  1 and 2 show one embodiment of an electric booster according to the present invention. An electric booster 10 according to the present embodiment includes an apparatus main body 11 having a rear end portion fixed to a vehicle compartment wall W that partitions an engine room and a vehicle compartment, and a tandem master cylinder 1 described later at the front end portion. A piston assembly 20 which will be described later and is used as a primary piston of the master cylinder 1, and a booster piston which is provided inside and outside the device body 11 and constitutes the piston assembly 20. (Output member) 21 is provided with an electric actuator 30 (described later) that applies thrust to the output member. The apparatus body 11 includes a large-diameter cup member 12 fixed to the casing wall W, a cylindrical member 13 to which the master cylinder 1 is consolidated, and a cylinder connecting the cup member 12 and the cylindrical member 13. The connecting member 14 is integrated with the cup member 12 via a support plate 15 fixed to the open end of the cup member 12. A hollow boss portion 12a is provided at the bottom of the cup member 12, and the tip end portion of the boss portion 12a extends through the vehicle interior wall W into the vehicle interior.

  The tandem master cylinder 1 includes a cylinder body 2 with a bottom and a reservoir (not shown), and a secondary piston that forms a pair with the piston assembly 20 as the primary piston on the inner side of the cylinder body 2. 3 is slidably arranged. In the cylinder body 2, two pressure chambers 4, 5 are defined by the piston assembly 20 and the secondary piston 3, and the pressure chambers 4, 5 correspond to the advance of the pistons 20, 3. The brake fluid sealed inside is pressure-fed from a discharge port (not shown) to a corresponding wheel cylinder. In each of the pressure chambers 5 and 6, return springs 6 and 7 for urging the piston assembly 20 as the primary piston and the secondary piston 3 rearward are disposed. The cylinder body 2 is provided with a relief port that communicates the inside of the pressure chambers 4 and 5 with the reservoir 11, but this is not shown.

  The piston assembly 20 constituting the electric booster 10 is composed of the booster piston 21 and an input piston (input member) 22 disposed in the booster piston 21 so as to be movable relative thereto. An input rod 23 interlocked with a brake pedal B (FIG. 3), which will be described later, is connected to the rear end portion of the input piston 22 via a joint 24. The input piston 22 operates the brake pedal B (pedal operation). As a result, the booster piston 21 moves forward and backward.

  The booster piston 21 constituting the piston assembly 20 has a partition wall 25 at an intermediate portion in the longitudinal direction therein, and the input piston 22 extends through the partition wall 25. The front end side of the booster piston 21 is inserted into the pressure chamber (primary chamber) 4 in the master cylinder 1, while the front end side of the input piston 22 is positioned inside the booster piston 21 in the same pressure chamber 13. Yes. The booster piston 21 and the input piston 22 are sealed by a seal member 26 fitted to the partition wall 25, and the booster piston 21 and the apparatus main body 11 are sealed by a seal member 27, respectively. The brake fluid is prevented from leaking out from the master cylinder 1.

  The electric actuator 30 is located outside the cylindrical member 13 constituting the apparatus main body 11 and fixed to the support plate 15. The electric actuator 30 is also connected to the input piston 22 inside the connecting member 14 constituting the apparatus main body 11. And a rotation transmitting mechanism 33 that decelerates the rotation of the electric motor 31 and transmits the rotation to the ball screw mechanism 32. The ball screw mechanism 32 includes a nut member (rotating member) 35 rotatably supported by the connecting member 14 via a bearing (angular contact bearing) 34 and a hollow member engaged with the nut member 35 via a ball 36. It consists of a screw shaft (linear motion member) 37. The rear end portion of the screw shaft 37 is non-rotatably and slidably fitted to the hollow boss portion 12 a of the cup member 12 constituting the apparatus main body 11, whereby the screw shaft 37 is screwed according to the rotation of the nut member 35. The shaft 37 moves linearly.

  On the other hand, the rotation transmission mechanism 33 constituting the electric actuator 30 includes a first pulley 38 attached to the output shaft 31a of the electric motor 31 and a second pulley 39 fitted non-rotatably to the nut member 35. And a belt (timing belt) 40 wound around the two pulleys 38 and 39. The second pulley 39 has a larger diameter than the first pulley 38, whereby the rotation of the electric motor 31 is decelerated and transmitted to the nut member 35 of the ball screw mechanism 32. The rotation transmission mechanism 33 is not limited to the pulleys and belts described above, and may be a reduction gear mechanism or the like.

  A flange member 41 that also functions as a guide for slidingly guiding the input piston 22 is fitted and fixed to a front end portion of a hollow screw shaft 37 constituting the ball screw mechanism 32. The flange member 41 comes into contact with a lid 42 fitted to the rear end of the booster piston 21 as the screw shaft 37 advances in the left direction in the drawing. The booster piston 21 is also advanced in accordance with the advance. In addition, one end of the cylindrical member 13 constituting the apparatus body 11 is locked to an annular protrusion 13 a formed on the cylindrical member 13 via a spring receiver 43, and the other end is opposed to the flange member 41. A return spring 44 is provided, and the screw shaft 37 is positioned at the original position shown in the drawing by the return spring 44 when the brake is not operated.

  On the other hand, an annular chamber 45 is defined between the booster piston 21 and the input piston 22. One end of each of the annular chambers 45 is locked to a flange portion 22 ′ provided in the input piston 22. A pair of spring members 46 (46A, 46B) whose other ends are locked to the partition wall 25 and the lid body 42 of the booster piston 21 are disposed. The pair of spring members 46 function as balance springs that hold the input piston 22 and the booster piston 21 at a neutral position relative to each other when the brake is not operated. Here, the pair of spring members 46 are arranged on the front side (master cylinder 1 side). As the other spring member 46A, a conical coil spring which is a kind of a non-linear spring is selected, and as the other spring member 46B disposed on the rear side (brake pedal B side), the same linear coil spring as that of the prior art is selected. The relative movement range between the booster piston 21 and the input piston 22 is regulated by the interference between the front step 22a and the rear step 22b provided on the input piston 22 and the booster piston 21 (FIG. 2). .

  A displacement detector (potentiometer) 48 for detecting the absolute displacement of the input piston 22 relative to the vehicle body is disposed between the cup member 12 constituting the apparatus main body 11 and the input rod 23, and the electric motor 31. Includes a rotation detector (resolver) 49 for detecting a rotation angle. The signals of the displacement detector 48 and the rotation detector 49 are sent to a controller (control device) 50. The controller 50 is based on the signals from the displacement detector 48 and the rotation detector 49. The rotation of the electric motor 31 is controlled.

  Hereinafter, the operation of the electric booster 10 configured as described above will be described.

  When the brake pedal B is operated, the input piston 22 moves forward, and its movement is detected by the displacement detector 48. Then, the controller 50 receives a signal from the displacement detector 48 and outputs a start command to the electric motor 31, whereby the electric motor 31 rotates and the rotation is transmitted to the ball screw mechanism 32 via the rotation transmission mechanism 33. As a result, the screw shaft 37 advances. Then, the booster piston 21 is pushed forward by the screw shaft 37, and the brake hydraulic pressure corresponding to the input thrust applied from the brake pedal B to the input piston 22 and the booster thrust applied from the electric actuator 30 to the booster piston 21. Is generated in the pressure chambers 4 and 5 in the master cylinder 1.

  At this time, based on the detection signals of the displacement detector 48 and the rotation detector 49, the relative displacement amount of both pistons can be determined from the difference between the absolute displacement of the input piston 22 and the absolute displacement of the booster piston 21. Therefore, when the rotation of the electric motor 31 is controlled so that relative displacement does not occur between the input piston 22 and the booster piston 21, the pair of spring members 46 interposed between the pistons 22 and 21 have a neutral position. maintain. The boost ratio at this time is uniquely determined by the area ratio between the pressure receiving area of the booster piston 21 and the pressure receiving area of the input piston 22 because the relative displacement amount is 0, and is the same as that of a general-purpose vacuum booster. Become.

  On the other hand, when the booster piston 21 is relatively displaced from the neutral position in the direction (forward) in which the brake fluid pressure is increased by the booster thrust, the boost ratio (braking force) increases, and the electric motor 31 works as a boost source. Brake assist operation is realized. Conversely, when the booster piston 21 is relatively displaced from the neutral position in the direction (rearward) in which the brake hydraulic pressure is reduced by the booster thrust, the boost ratio (braking force) is reduced, and regenerative cooperative operation during regenerative braking is realized. . Further, since the communication between the pressure chambers 4 and 5 in the master cylinder 1 and the reservoir is blocked by the advance of the booster piston 21, automatic braking operations such as adaptive control (ACC) and hill start assist are also possible.

  Here, the input / output relationship in the electric booster 10 will be described with reference to the conceptual diagram shown in FIG.

The force (input) Fi applied by the driver to the input piston 22 via the brake pedal B is expressed by the following equation (1) where Fp is the force (pedal pressing force) the driver steps on the brake pedal B and n is the pedal ratio. Become.
Fi = n × Fp (1)

At this time, the reaction force Fs received from the spring member 46 (46A, 46B) and the reaction force Fm received from the hydraulic pressure Pm in the master cylinder 1 are applied to the input piston 22 and are balanced with the input Fi. Therefore, the balance of this force is expressed by the following equation (2).
Fi = Fm + Fs (2)

The reaction force Fm received from the hydraulic pressure Pm in the master cylinder 1 described above is a force generated when the input piston 22 enters the master cylinder 1, and when the area of the tip of the input piston 22 is Ai, the following (3 ).
Fm = Ai × Pm (3)

On the other hand, the reaction force Fs received from the spring member 46 is a force generated when the input piston 22 and the output piston 21 undergo relative displacement, and is now a spring constant of the spring member 46A on the front side (master cylinder 1 side). Is Ks1, the spring constant of the rear spring member 46B is Ks2, and the value obtained by subtracting the displacement amount Xb of the booster piston 21 from the displacement amount Xi of the input piston 22 is the relative displacement amount Xr (Xr = Xi−Xb). It is given by equation (4).
Fs = (Ks1 + Ks2) × Xr (4)

  Incidentally, the fluctuation of the hydraulic pressure Pm in the master cylinder 1 is non-linear with respect to the relative displacement amount Xr between the input piston 22 and the booster piston 21, and as described above, this hydraulic pressure fluctuation is braked via the input piston 22. It is transmitted to the pedal B and causes pedaling force fluctuation and pedal vibration. However, in the present embodiment, among the pair of spring members 46 that hold the input piston 22 and the booster piston 21 at the neutral positions of relative displacement, a conical coil spring that is a kind of nonlinear spring is used as the front spring member 46A. Therefore, the reaction force Fs received by the input piston 22 from the pair of spring members 46 is nonlinear with respect to the relative displacement amount Xr. As a result, the reaction force fluctuation caused by the fluid pressure fluctuation in the master cylinder 1 is offset by the nonlinear spring force fluctuation of the pair of spring members 46, and as a result, the pedaling force fluctuation and pedal vibration of the brake pedal B are suppressed. It is possible to ensure a good pedal feel. Further, since only one of the pair of spring members 46A is changed to a conical coil spring which is a non-deformation spring as compared with the conventional apparatus, the apparatus cost does not increase specially.

  Here, in the above embodiment, the front spring member 46A is a conical coil spring. However, as shown in FIG. 4, in the present invention, the front spring member 46A is a conventional linear spring, and the rear spring is used. The member 46B may be a conical coil spring, or both the front and rear spring members 46A and 46B may be conical coil springs as shown in FIG. In any of the examples, similarly to the above embodiment, the pedal force fluctuation and pedal vibration of the brake pedal are suppressed, and a good pedal feel can be ensured. Further, the conical coil spring has the advantage that it can be designed to have an arbitrary non-linearity in addition to the fact that the contact length can be increased and contact with the surroundings can be easily avoided, and the degree of freedom in design is improved.

  The conical coil spring may be replaced with another non-deformable spring of a different type. FIG. 6 shows an embodiment in which a barrel coil spring is used as one (front spring member) 46A of the pair of spring members 46, and FIG. 7 shows an example in which an unequal pitch coil spring is used as the other spring member 46A. However, as shown in FIGS. 4 and 5, the rear spring member 46B or both the front and rear spring members 46A and 46B may be used. In any case, as in the case of using the conical coil spring, the pedal force fluctuation and pedal vibration of the brake pedal are suppressed, and a good pedal feel can be ensured. In particular, when a barrel coil spring is used, there is an advantage that the length of the device can be shortened because the deflection with respect to the displacement is small. On the other hand, when an unequal pitch coil spring is used, a nonlinear characteristic is given at low cost. There are advantages that can be made.

  Further, the pair of spring members 46 (46A, 46B) may be a combination of different types of nonlinear springs as shown in FIGS. More specifically, FIG. 8 shows an embodiment in which a conical coil spring is used as the front spring member 46A and a barrel coil spring is used as the rear spring member 46B, and FIG. 9 shows a cone as the front spring member 46A. FIG. 10 shows an example in which a coil spring is used as an unequal pitch coil spring as the rear spring member 46B. FIG. 10 shows a barrel coil spring as the front spring member 46A and an unequal pitch coil as the rear spring member 46B. This is an embodiment using springs. Of course, these different types of non-linear springs may be arranged in the reverse direction of the illustration. When combining different types of non-linear springs in this way, the pair of spring members 46 can have arbitrary non-linearity while taking advantage of the respective springs.

  In the above embodiment and each example, a pair of spring members 46 (46A, 46B) that hold the input piston 22 and the booster piston 21 in a neutral position of relative displacement are used with one or both of the pair of spring members 46 (46A, 46B). Although the spring member 46 is made to have non-linearity, the present invention may make the pair of spring members 46 have non-linear characteristics while using the same linear coil spring as the conventional one.

  FIG. 11 shows an embodiment in which a pair of spring members 46 are made nonlinear while using a linear coil spring. In this embodiment, the non-operating state shown in (a) is set as the original position (relative displacement amount Xr = 0), and the booster piston 21 is moved backward as shown in (b) while the input piston 22 is fixed from this state. When the relative displacement amount Xr changes to Xr1 (Xr = Xr1), the rear spring member 46B reaches the free length, and is designed so that no spring load is generated. The relative movement range between the booster piston 21 and the input piston 22 is restricted by the interference between the booster piston 21 and the front step 22a and the rear step 22b provided on the input piston 22, as described above. When the booster piston 21 is further retracted from the state shown in b), the rear spring member 46B is completely free as shown in (c). In the figure, Ls2 represents the set length of the rear spring member 48B, and Lf2 represents the free length of the spring member 48B.

  With the above design, the rear spring member 46B becomes free in the range of Xr1 ≦ Xr ≦ Xrmax, and no spring load is generated during this period. On the other hand, the spring constants of the pair of spring members 46 are Ks1 + Ks2 in the range of 0 ≦ Xr ≦ Xr1, and Ks1 in the range of Xr1 ≦ Xr ≦ Xrmax, which makes the pair of spring members 46 non-linear with respect to the relative displacement amount Xr. Become. Therefore, as in the above-described embodiment in which a non-linear spring is used for one or both of the pair of spring members 46, the reaction force fluctuation accompanying the hydraulic pressure fluctuation in the master cylinder 1 is offset by the non-linear spring force fluctuation, and the brake pedal B As a result, the pedaling force fluctuation and pedal vibration are suppressed, and a good pedal feel can be secured.

  FIG. 12 shows another embodiment in which a pair of spring members 46 are made nonlinear while using a linear coil spring as it is. In this embodiment, the non-operating state shown in (a) is set as the original position (relative displacement amount Xr = 0), and the booster piston 21 is moved forward as shown in (b) while the input piston 22 is fixed from this state. When the relative displacement amount Xr changes to Xr2 (Xr = Xr2), the front spring member 46A reaches the free length and no spring load is generated. In this case, when the booster piston 21 is further retracted from the state shown in (b), the front spring member 46A is completely free as shown in (c).

  In the embodiment shown in FIG. 12, the front spring member 46A is free in the range of Xrmin ≦ Xr ≦ Xr2, and no spring load is generated during this period. On the other hand, the spring constants of the pair of spring members 46 are Ks1 + Ks2 in the range of Xr2 ≦ Xr ≦ 0, and Ks2 in the range of Xrmin ≦ Xr ≦ Xr2, thereby making the pair of spring members 46 nonlinear with respect to the relative displacement amount Xr. Become. As a result, similar to the embodiment shown in FIG. 11, the reaction force fluctuation accompanying the hydraulic pressure fluctuation in the master cylinder 1 is canceled by the nonlinear spring force fluctuation, and the pedal force fluctuation and pedal vibration of the brake pedal B are suppressed. It is possible to ensure a good pedal feel.

As shown in FIGS. 11 and 12, when the free length of the pair of spring members 46 is designed to give non-linearity, the same linear coil spring as the conventional one is used, so that the design is easy and the cost does not change. is there. In the embodiment shown in FIG. 12, the spring member 46 is a linear coil spring, but it may be a conical coil spring, a barrel coil spring, or an unequal pitch coil spring. Can be granted .

DESCRIPTION OF SYMBOLS 1 Tandem type master cylinder 10 Electric booster 20 Piston assembly 21 Booster piston (output member)
22 Input piston (input member)
30 Electric Actuator 31 Electric Motor 32 Ball Screw Mechanism (Rotational Linear Motion Conversion Mechanism)
46 A pair of spring members 46A Front side spring member 46B Rear side spring member B Brake pedal

Claims (5)

An input member that moves forward and backward by operating the brake pedal;
An output member that is arranged to be movable relative to the input member and is driven by an electric actuator ;
And a pair of spring members for holding the neutral position of relative displacement between the output member and the input member when the brake is not actuated,
The electric booster for generating a desired brake fluid pressure within the master cylinder by controlling the relative displacement of the output member with respect to the movement of said input member,
Either one of the pair of spring members reaches a free length in a process until the input member and the output member are relatively displaced and movement of the output member is restricted by the input member. Electric booster characterized by. The electric booster according to claim 1, wherein both of the pair of spring members are linear springs.   The electric booster according to claim 1, wherein at least one of the pair of spring members is a non-linear spring.   The electric booster according to claim 1, wherein the pair of spring members is a combination of different types of nonlinear springs. Said nonlinear spring is a conical coil spring, electric booster according to claim 3 or 4, characterized in that the one selected from the barrel spring and irregular pitch coil spring.

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