JP5875310B2 - Electric booster - Google Patents

Description

  The present invention relates to an electric booster.

  In Patent Document 1, when the brake pedal is operated, the input piston and the booster piston move forward together, and the input thrust applied from the brake pedal to the input piston and the booster thrust applied from the electric motor to the booster piston An electric booster that generates a brake fluid pressure corresponding to the pressure in a pressure chamber in the master cylinder is disclosed.

JP 2008-302725 A

However, since the electric booster described in Patent Document 1 uses an expensive resolver (rotational position detection device) for detecting the rotational displacement of the electric motor, high mounting accuracy and electrical adjustment are required. ing. For this reason, assembly and adjustment work have become complicated, which has been a factor of reducing the production efficiency of the electric booster.
Accordingly, the present invention has been made in view of the above circumstances, and an object thereof is to provide an electric booster capable of improving manufacturing efficiency.

In order to solve the above-described problems, an electric booster according to the present invention includes an electric motor controlled in accordance with an operation of an input rod connected to a brake pedal, a master cylinder provided in a housing and driven by the electric motor. A piston propelling member that propels the piston, a control device that feedback-controls the electric motor based on a current value of the electric motor that changes according to a resistance applied to the piston propelling member, and an initial position during non- braking moved in contact with said piston propulsion member when said piston propulsion member is moved to a predetermined position immediately before the hydraulic pressure generating position for generating a hydraulic pressure by the piston of the master cylinder, than before moving to the predetermined position And a resistance applying mechanism that applies a large predetermined resistance.

  According to the present invention, since a rotational position detection device for an electric motor such as a resolver is not used, the manufacturing efficiency of the electric booster can be improved.

It is the schematic of the electric actuation in 1st Embodiment, and is a figure which shows the state at the time of non-braking especially. It is the schematic of the electric actuation in 1st Embodiment, and is a figure which shows the state at the time of the assist part reaching | attaining the position immediately before a hydraulic pressure generation position especially. It is explanatory drawing of 1st Embodiment and is a figure which shows the relationship between the piston position of a master cylinder, and the load concerning a piston. It is a block diagram of the control apparatus in 1st and 2nd embodiment. It is a flowchart of control by the control apparatus in 1st and 2nd embodiment. It is the schematic of the electric actuation in 1st Embodiment, and is a figure which shows the state at the time of non-braking especially. It is the schematic of the electric actuation in 1st Embodiment, and is a figure which shows the state at the time of the assist part reaching | attaining the position immediately before a hydraulic pressure generation position especially.

A first embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a schematic diagram of an electric actuation 1 incorporated in a brake control device of an automobile. The electric actuation 1 includes an electric booster 2 and a master cylinder 3 according to the present invention. The master cylinder 3 is generally configured by a cylinder body S in which the piston 4 slides and a reservoir R that stores brake fluid discharged from the master cylinder 3. Inside the cylinder body S, a pressure chamber SA defined by the piston 4 is formed. The cylinder body S is formed with a reservoir port 26 that allows the pressure chamber SA and the reservoir R to communicate with each other. The brake hydraulic pressure generated in the master cylinder 3 is supplied to the hydraulic circuit 27 and then supplied to each wheel cylinder 28 provided for each vehicle wheel. The hydraulic circuit 27 controls the behavior of the vehicle by controlling the brake hydraulic pressure to each wheel cylinder 28. The master cylinder 3 in FIGS. 1 and 2 is a single master cylinder with one piston 4, but a tandem master cylinder in which two pistons 4 are arranged in the axial direction is applied. be able to.

  The electric booster 2 includes a housing 5, a part of which is shown in each figure, an electric motor 6 attached to the housing 5, an input mechanism 8 driven by operation of a brake pedal 7, and a master cylinder at one end. 3 and an output rod 9 abutted on the piston 4 and a piston propulsion mechanism 10 driven by the electric motor 6 to advance and retract the output rod 9 in the axial direction (left-right direction in FIG. 1). The input mechanism 8 includes an input rod 11, a cup 12 with which one end of the input rod 11 (the end on the master cylinder 3 side and the left end in FIG. 1) is engaged, the housing 5, and the input rod. 11, and a stroke simulator 13 that provides a reaction force to the brake pedal 7.

  The piston propulsion mechanism 10 includes a nut member 14, a screw shaft member 15, and a plurality of balls 16 that can roll between the nut member 14 and a ball screw mechanism. The nut member 14 is rotatably supported by a pair of bearings 17 provided in the housing 5 and is rotationally driven by the electric motor 6 via the belt 18. In this embodiment, the screw shaft member 15 is a hollow cylindrical member having a spiral groove formed on the outer peripheral surface. A shaft member 20 having a shaft hole 19 is slidably fitted to the inner peripheral side of one end of the screw shaft member 15 (the end on the master cylinder 3 side and the left end in FIG. 1). .

  In the shaft hole 19 of the shaft member 20, the other end of the output rod 9 is slidably fitted on one end side (on the master cylinder 3 side and on the left side in FIG. 1), and the other end side is input. The cup 12 of the mechanism 8 is slidably fitted. A flange 21 having an outer diameter larger than the outer diameter of the screw shaft member 15 is formed at one end of the shaft member 20. As shown in FIG. 1, the flange 21 has a large-diameter portion 22 of the output rod 9 in contact with a radially inner end surface 21 </ b> A on one end side of the shaft member 20, and the other end side of the shaft member 20. The end surface 15A of the one end portion side of the screw shaft member 15 is brought into contact with the flange 21 of the shaft member 20 on the end surface 21B. In the present embodiment, a piston propulsion member that propels the piston 4 of the master cylinder 3 by driving the electric motor 5 is constituted by the screw shaft member 15 and the shaft member 20 having the flange 21.

One end of the housing 5 (the end on the master cylinder 3 side and the left end in FIG. 1) is fixed to the housing 5, and a ring-shaped seat 23 is attached to the other end. A spring 24 is provided. The return spring 24 is provided so as to bias the shaft member 20 in the backward direction when the shaft member 20 moves forward by a predetermined amount or more and propels the piston 4. The return spring 24 is a brake that is generated in the pressure chamber SA of the master cylinder 3 by retracting the shaft member 20 when the electric motor 6 fails while the piston 4 is being driven by the shaft member 20. The hydraulic pressure is released to prevent vehicle brake lock. Seat 23 is opposed to the receiving surface 25 to the outer peripheral side is formed in the housing 5 is arranged to pair toward the outward radial direction side edge surface 21C of the one end side of the shaft member 20 the inner peripheral side of the flange 21 ing. When the brake pedal 7 shown in FIG. 1 is not operated (hereinafter referred to as non-braking), the return spring 24 is bent toward the compression side by the outer peripheral side of the seat 23 being received by the receiving surface 25 of the housing. It is in a state and has a so-called set load. Here, the axial distance (the distance in the left-right direction in FIG. 1) between the seat portion 23 of the return spring 24 and the radially outer end surface 21C of the flange 21 of the shaft member 20 is A, and the piston 4 in the master cylinder 3 When the distance A in the non-braking state is A0 and the distance B in the non-braking state is B0, where A0 = B0, The distance A0 and the distance B0 are configured to be equal. With this configuration, when the ineffective stroke of the master cylinder ends, the seat portion 23 of the return spring 24 and the radially outer end surface 21C of the flange 21 of the shaft member 20 come into contact with each other. A predetermined resistance is applied to the shaft member 20.

  Accordingly, the nut member 14 is rotated in one direction by driving the electric motor 6 from the non-braking state shown in FIG. 1, and the screw shaft member 15, the shaft member 20, the output rod 9, and the piston of the master cylinder 3. 4 is propelled (moved to the left in FIG. 1), as shown in FIG. 2, when the distance A becomes 0, that is, the radially outer end face 21C of the flange 21 of the shaft member 20 returns. When the spring 24 comes into contact with the inner peripheral side of the seat portion 23, the distance B becomes zero. When the flange 21 of the shaft member 20 comes into contact with the seat portion 23 of the return spring 24, the piston propulsion mechanism 10 is in a position immediately before the piston 4 closes the reservoir port 26, that is, the master cylinder 3 is hydraulic. Is reached immediately before the position where the pressure is generated (hereinafter referred to as the hydraulic pressure generation position).

  The resistance applying mechanism according to the first embodiment is configured by providing the above-described distance A0 (A0 = B0) between the return spring 24 (seat portion 23) and the flange 21 of the piston propulsion mechanism 10 in the non-braking state. To establish. Then, as can be easily understood from the above description, the resistance applying mechanism immediately before reaching the hydraulic pressure generation position shown in FIG. 2 from the initial position of the piston propulsion mechanism 10 at the time of non-braking shown in FIG. A predetermined resistance can be applied to the shaft member 20 when the shaft member 20 is moved to the position.

Next, the control of the control device 29 that feedback-controls the electric motor 6 based on the current value of the electric motor 6 that changes according to the resistance received by the piston propulsion mechanism 10 is shown in the block diagram shown in FIG. 4 and FIG. This will be described based on a flowchart.
When the brake pedal 7 is operated, the displacement amount of the brake pedal 7 is measured by the pedal displacement sensor 30 (step S1 in FIG. 5). Next, based on the measurement result of the pedal displacement sensor 30 by the control mode selection unit 31, whether or not the pedal displacement amount is an invalid stroke region, that is, whether or not the pedal displacement amount does not lead to generation of a braking force. It is determined whether or not (step S2 in FIG. 5).

  When it is determined that the pedal displacement amount is outside the invalid stroke region (No in step S2 in FIG. 5), the control mode selection unit 31 selects the hydraulic pressure control mode. In the hydraulic pressure control mode, the target hydraulic pressure / current calculation unit 32 calculates the target hydraulic pressure to be generated in the master cylinder 3 based on the displacement amount of the brake pedal 7 (step S3 in FIG. 5). Then, the control unit 33 operates the electric motor so that the target hydraulic pressure calculated in step S4 in FIG. 5 is equal to the brake hydraulic pressure in the master cylinder 3 measured by the hydraulic pressure sensor 34 in step S4 in FIG. The motor 6 is controlled (step S5 in FIG. 5). In other words, the electric motor 6 is controlled such that the current value of the electric motor 6 measured by the current sensor 35 (the load applied to the piston propulsion mechanism 10) becomes a value corresponding to the target hydraulic pressure.

  On the other hand, when it is determined that the pedal displacement amount is within the invalid stroke region (Yes in step S2 in FIG. 5), the control mode selection unit 31 selects the current control mode. In the current control mode, the electric motor 6 is controlled based on the current value of the electric motor 6 detected by the current sensor 35, in other words, the resistance applied to the piston propulsion mechanism 10. More specifically, the target hydraulic pressure / current calculation unit 32 exceeds the resistance L1 (see FIG. 3) by the return spring 36 of the master cylinder 3 and is applied to the shaft member 20 and the screw shaft member 15. A resistance L (L2> L> L1) that does not satisfy L2 (see FIG. 3), that is, a resistance L1 by the return spring 36 of the master cylinder 3 and a resistance L1 by the return spring 36 of the master cylinder 3 The electric motor 6 generates a torque corresponding to the resistance L that does not satisfy the total load L2 (L2 = L1 + L3) with the resistance L3 (see FIG. 3) by the return spring 24 that is in contact with the flange 21 of the shaft member 20. The generated current value is set as the target current value (step S6 in FIG. 5). Next, the control unit 33 reads the target current value (step S7 in FIG. 5), and controls the electric motor 6 so that the measured value of the current sensor 35 becomes equal to the target current value (step S8 in FIG. 5). .

  Here, in the conventional electric booster as described in Patent Document 1, in order to propel the piston of the master cylinder, the piston corresponding to the rotational position is detected by detecting the rotational position of the electric motor with a resolver. The position of the electric motor is calculated and the electric motor is position-controlled so that the target piston position for generating the brake hydraulic pressure corresponding to the operation amount of the brake pedal is obtained. Further, since the conventional electric booster is provided with a hydraulic pressure sensor for detecting the brake hydraulic pressure of the master cylinder, the detected value of the hydraulic pressure sensor is feedback controlled without using the resolver. The hydraulic pressure control can be performed so as to generate the brake hydraulic pressure corresponding to the operation amount of the brake pedal. However, when hydraulic pressure control is performed, no hydraulic pressure is generated in the invalid stroke area of the piston of the master cylinder, so feedback control by the hydraulic pressure sensor cannot be performed, and the hydraulic pressure generation start time according to the brake pedal operation is accurate. I couldn't control it well. From this point of view, it is necessary to control the position of the electric motor by the resolver in the invalid stroke region.

  According to the first embodiment, when the electric motor 6 is driven, the piston propulsion mechanism 10 moves from the initial position during non-braking (see FIG. 1) to the position immediately before the hydraulic pressure generation position (see FIG. 2). Thus, when the flange 21 of the shaft member 20 contacts the return spring 24, a predetermined resistance is applied to the shaft member 20. As a result, a predetermined resistance applied to the shaft member 20 is transmitted to the electric motor 6 via the screw shaft member 15, the nut member 14, and the belt 18, and the predetermined resistance is detected by the current value of the electric motor 6. In this way, it is possible to detect the position of the shaft member 20, that is, that the piston 4 of the master cylinder 3 reaches the hydraulic pressure generation position. This eliminates the need for a resolver for detecting the rotational displacement of the electric motor 6 employed in the conventional electric booster for detecting the axial direction position of the shaft member 20, the screw shaft member 15, and the piston 4. Become. Therefore, when the resolver is not used, complicated assembly and adjustment work at the time of manufacturing the electric booster 2 is eliminated, and the manufacturing efficiency of the electric booster 2 can be improved. If the rotational position detection device does not require complicated assembly and adjustment work, this rotational position detection device may be provided in the electric booster to detect the rotational displacement of the electric motor 6.

Next, a second embodiment of the present invention will be described with reference to FIGS.
The electric booster 42 of the second embodiment is different from the electric booster 2 of the first embodiment described above only in the structure of the resistance applying mechanism, and has the same basic structure. Therefore, in the following description, the same or corresponding components as those in the first embodiment are given the same name and reference numerals, and redundant description is omitted for the purpose of simplifying the description of the specification.

  As described above, in the first embodiment, the driving of the electric motor 6 causes the piston propulsion mechanism 10 to move from the initial position during non-braking (see FIG. 1) to the position immediately before the hydraulic pressure generation position (see FIG. 2). At the time of movement, the flange 21 of the shaft member 20 is brought into contact with the return spring 24 to give a predetermined resistance. On the other hand, in 2nd Embodiment, as FIG. 6 shows, the receiving part 25 of the housing 5 of 1st Embodiment is not provided, but the other end part of return spring 24 'is shaft member 20'. Is always in contact with the flange 21 '. Thus, a load is applied to the piston propulsion mechanism 10 by the return spring 24 in a state where the piston propulsion mechanism 10 is located at the initial position (see FIG. 6) at the time of non-braking.

  In the second embodiment, a protrusion 43 made of an elastic body is provided on the housing 5 so as to face the flange 21 'of the shaft member 20' in the axial direction. This projection 43 is driven by the electric motor 6 so that the flange 21 'of the shaft member 20' is moved from the initial position during non-braking (see FIG. 6) to the position just before the hydraulic pressure generation position (see FIG. 7). At this point, it comes into contact with the flange 21 'of the shaft member 20'. Thus, in the second embodiment, a predetermined resistance is applied to the shaft member 20 when the flange 21 ′ contacts the protrusion 43, and this resistance is detected by the current value of the electric motor 6, thereby The position 20 ′, that is, the piston 4 of the master cylinder 3 can be detected to reach the hydraulic pressure generation position. In addition, the protrusion 43 can be comprised by one member formed in the ring shape. Moreover, the protrusion 43 may arrange a plurality of conical protrusions 43, for example, on the same circumference.

  According to the second embodiment, when the electric motor 6 is driven, the shaft member 20 ′ moves from the initial position during non-braking (see FIG. 6) to the position immediately before the hydraulic pressure generation position (see FIG. 7). Thus, the flange 21 of the shaft member 20 contacts the protrusion 43 and gives a predetermined resistance to the shaft member 20 ′. By detecting this predetermined resistance based on the current value of the electric motor 6, the shaft member 20 ′ It can be detected that the piston 4 of the master cylinder 3 reaches the hydraulic pressure generation position. This eliminates the need for a rotational position detection device such as a resolver for detecting the rotational displacement of the electric motor 6 employed in the conventional electric booster for detecting the position of the piston 4 of the master cylinder 3. When the electric booster 42 is manufactured, complicated assembly and adjustment work is eliminated, and the manufacturing efficiency of the electric booster 42 can be improved.

2 electric booster, 3 master cylinder, 4 piston, 5 housing, 6 electric motor, 7 brake pedal, 10 piston propulsion mechanism, 11 input rod, 15 screw shaft member (piston propulsion member), 20 shaft member (piston propulsion member) ), 21 Flange (piston propulsion member), 24 Return spring (resistance imparting mechanism)

Claims (3)

An electric motor controlled in accordance with the operation of an input rod connected to the brake pedal;
A piston propulsion member that is provided in the housing and propels the piston of the master cylinder by driving the electric motor;
A control device that feedback-controls the electric motor based on a current value of the electric motor that changes in accordance with a resistance applied to the piston propulsion member;
It said piston propulsion member when said piston propulsion member is moved is moved to a predetermined position immediately before the hydraulic pressure generating position for generating a hydraulic pressure by the piston of the master cylinder from an initial position of non-braking contact, the predetermined A resistance applying mechanism that applies a predetermined resistance larger than that before moving to a position ;
An electric booster comprising:   The resistance applying mechanism has a return spring having one end attached to the housing, and the piston propelling member that has moved to the predetermined position is brought into contact with the other end of the return spring to thereby provide resistance to the piston propelling member. The electric booster according to claim 1, wherein the electric booster is applied.   The resistance applying mechanism includes a protrusion provided on the housing, and applies resistance to the piston propelling member by bringing the piston propelling member moved to the predetermined position into contact with the protrusion. Item 2. The electric booster according to Item 1.

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