JP2008222069A - Electric brake - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric brake capable of accurately controlling a piston pressing force to a brake disc. <P>SOLUTION: The electric brake comprises a rotation brake disc 6 rotating with wheels, a non-rotation brake disc 9 supported so as to be displaced toward the rotation brake disc 6 and so as not to rotate, a piston 1 opposing the non-rotation brake disc 9, a ball screw 15 rotatably coupled to the piston 1, a ball screw nut mechanism moving forward and backward the piston 1 to and from the non-rotation brake disc 9 by rotation of the ball screw 15, and an electric motor 11 rotatively driving the ball screw 15. According to a motor rotation angle θm of the electric motor 11, an estimated value of the pressing force fp of the piston 1 is calculated. A control command value to the electric motor 11 is feed-back controlled so as to bring the estimated value of the piston pressing force fp close to a piston pressing force command value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an improvement of an electric brake that drives a braking member of a wheel with an electric motor.

  In recent years, in order to reduce or eliminate the hydraulic pressure source mounted on an aircraft, there is a tendency to change a brake for braking a wheel from a hydraulic brake to an electric brake.

Patent Document 1 discloses an electric brake that generates a braking force by converting a rotary motion of an electric motor into a reciprocating motion of a piston.
Japanese Patent Laying-Open No. 2005-069398

  However, in such a conventional electric brake, a friction torque loss occurs in the process of transmitting the generated torque of the electric motor to the piston. Therefore, the piston pressing force against the brake disc is accurately determined due to the friction torque loss. There was a problem that it could not be controlled.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an electric brake capable of accurately controlling a piston pressing force against a brake disk.

The present invention relates to a rotating brake disc that rotates together with a wheel, a non-rotating brake disc that is displaceable and non-rotatable toward the rotating brake disc, a piston that faces the non-rotating brake disc, and a rotation that rotates against the piston. A motor of this electric motor, comprising: a ball screw that can be connected, a ball screw / nut mechanism that causes the piston to move forward and backward by rotation of the ball screw, and an electric motor that rotationally drives the ball screw An estimated value of the piston pressing force fp for the non-rotating brake disc of the piston is calculated according to the rotation angle θ _m, and the control command value for the electric motor is set so that the estimated value of the piston pressing force fp approaches the piston pressing force command value It was characterized by feedback control.

  According to the present invention, feedback control of the operation of the electric motor is performed so that the estimated value of the piston pressing force fp approaches the piston pressing force command value, so that hysteresis caused by friction torque loss of the ball screw / nut mechanism or the like is eliminated, The actual piston pressing force can be accurately controlled, and the control response and accuracy of the braking force generated by the electric brake can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  The electric brake for aircraft shown in FIG. 1 is a multi-plate disc type provided inside the wheel of the wheel.

  The electric brake includes a disc-shaped rotating brake disc 6 that rotates together with wheels, a disc-shaped non-rotating brake disc 9 attached to a body shaft (axle), a piston 1 that faces the non-rotating brake disc 9, and a piston 1 And an electric actuator 5 that drives the non-rotating brake disk 9 to move forward and backward.

  The three rotary brake discs 6 are arranged so as to be sandwiched between the four non-rotary brake discs 9. The non-rotating brake disk 9 is supported so as to be displaceable in the axle direction via a torque tube or the like with respect to a body shaft (not shown). The rotary brake disc 6 rotates integrally with a wheel (not shown) and is supported so as to be displaceable in the axle direction with respect to the wheel.

  When the electric actuator 5 is actuated, the non-rotating brake disc 9 and the rotating brake disc 6 are pressed against each other by the pressing force of each piston 1, and a frictional force is generated at the sliding portion to obtain a braking torque. Yes.

  The piston 1 is slidably supported on the housing 7. A ball screw 15 protruding from the base end portion of the piston 1 is provided, and the piston 1 is provided with a ball nut that is screwed to each ball screw 15 via a large number of balls, thereby interposing a ball screw / nut mechanism. Is done. This ball screw / nut mechanism is configured to convert the rotation of the ball screw 15 into a linear motion of the piston 1 and to move the piston 1 forward and backward with respect to the non-rotating brake disc 9.

  The housing 7 includes two electric motors 11, four pistons 1, and two speed reduction mechanisms 10 that transmit the rotation of one electric motor 11 to two ball screws 15. The four pistons 1 are arranged at equal intervals in the rotational circumferential direction of the wheel. In addition, each piston 1 does not necessarily need to be arrange | positioned at equal intervals about the rotation peripheral direction of a wheel.

  The numbers of the piston 1, the electric motor 11, the rotating brake disc 6, and the non-rotating brake discs 9 are not limited to this, and are arbitrarily set.

  The speed reduction mechanism 10 is configured to transmit the rotation of one electric motor 11 to two ball screws 15. A drive gear 14 is connected to the motor shaft 13 of the electric motor 11, and a driven gear 16 is connected to the base end portion of the ball screw 15, and the rotation of one drive gear 14 is transmitted to the two driven gears 16.

  The controller 20 (see FIG. 2) controls the drive current of the electric motor 11 in accordance with the piston pressing force command value signal sent from the aircraft control system. When the electric motor 11 rotates in the forward direction, each piston 1 abuts against the non-rotating brake disk 9 and presses each non-rotating brake disk 9 against each rotating brake disk 6 to obtain a braking torque. When the electric motor 11 rotates in the returning direction, each piston 1 is separated from the non-rotating brake disc 9, and the non-rotating brake disc 9 is not pressed against each rotating brake disc 6, and the braking is released.

  In principle, since the pressing force of each piston 1 is proportional to the current of the electric motor 11, the pressing force of each piston 1 can be adjusted by controlling the current of the electric motor 11. However, in actuality, in the process of transmitting the generated torque of the electric motor 11 to each piston 1, friction torque loss occurs when the speed reduction mechanism 10 and the ball screw / nut mechanism are operated. Therefore, hysteresis caused by this friction torque loss is generated. Is generated between the piston pressing force command value and the actual piston pressing force.

  FIG. 3 shows how the piston pressing force by the conventional open control based on the piston pressing force command value changes. When the piston pressing force command value changes periodically, the actual piston pressing force includes the deceleration mechanism 10. Hysteresis due to friction torque loss of the ball screw / nut mechanism occurs. For this reason, with the conventional open control method, the piston pressing force cannot be accurately controlled.

In response to this, the present invention calculates an estimated value of the pressing force fp of the piston 1 in accordance with the motor rotation angle θ _m of the electric motor 11, and approximates the estimated value of the piston pressing force fp to the piston pressing force command value. The control command value for the electric motor 11 is feedback-controlled.

FIG. 2 is a block diagram showing a configuration for generating a piston pressing force by controlling the drive current of the electric motor 11. The controller 20 inputs a detection signal of the motor rotation angle θ _m of the electric motor 11 and calculates an estimated value of the pressing force fp of the piston 1, and the estimated value of the piston pressing force fp is determined by the piston pressing. A piston pressing force controller 22 that calculates a control command value so as to approach the force command value, a pressing force current conversion gain 23 that outputs a current command value for the electric motor 11 in accordance with the control command value, and the current command value And a motor driver 24 that inputs a detection signal of the motor rotation angle θ _m of the electric motor 11 and a detection signal of the motor current of the electric motor 11 to control the driving power of the electric motor 11.

  In this way, the control command value for the electric motor 11 is feedback-controlled so that the estimated value of the piston pressing force fp approaches the piston pressing force command value, thereby eliminating the hysteresis caused by the friction torque of the speed reduction mechanism 10 and the ball screw / nut mechanism. In addition, the actual piston pressing force can be accurately controlled, and the control response and accuracy of the braking force generated by the electric brake can be improved.

  FIG. 1 shows a model diagram of an electric brake composed of Nm electric motors 11 and Np pistons 1. The equation of motion of the equivalent inertia mass Me composed of the rotor of the electric motor 11 and the inertia moment of the speed reduction mechanism 10 and the mass of the rotary brake disc 6 is expressed by the following equation.

However,
M _c : Equivalent inertia mass C _e : Equivalent viscous resistance coefficient K _e : Spring constant of brake structure R _g : Reduction ratio L _b of reduction mechanism 10 _B k: Lead of ball screw / nut mechanism K _T : Torque constant of electric motor 11 y _p: stroke of the piston 1 theta _m: rotation angle f _a of the electric motor 11: theoretical thrust per one piston 1 f _f: frictional force per one piston 1 i _m: 1 per electric motor 11 Current τ _f : friction torque per one speed reduction mechanism 10 The sum of the viscosity term and the spring term in equation (1) is the total pressing force fp of the piston 1, and this total pressing force fp is expressed by the following equation: .

As described above, if the rotation angle θ _m of the electric motor 11 is detected and the rotation speed dθ _m / dt is calculated, the total pressing force fp of the piston 1 can be estimated from the equation (5).

In the present embodiment, a rotating brake disc 6 that rotates together with a wheel, a non-rotating brake disc 9 that is displaceable and non-rotatable toward the rotating brake disc 6, and a piston that faces the non-rotating brake disc 9. 1, a ball screw 15 rotatably connected to the piston 1, a ball screw / nut mechanism for moving the piston 1 forward and backward with respect to the non-rotating brake disk 9 by rotation of the ball screw 15, and rotating the ball screw 15. And an electric motor 11 for driving. The piston pressing force fp of the piston 1 against the non-rotating brake disk 9 is estimated according to the motor rotation angle θ _m of the electric motor 11, and the estimated value of the piston pressing force fp is determined as the piston pressing force. The control command value for the electric motor 11 is fed to the force command value so Because the back-back control is performed, the hysteresis caused by the friction torque loss of the ball screw / nut mechanism, etc. can be eliminated, the actual piston pressing force can be controlled accurately, and the control response of the braking force generated by the electric brake can be controlled accurately. Increases sex. Moreover, since it is not necessary to provide the load sensor which measures the pressing force fp of piston 1 by the said structure, the cost increase of a product can be avoided.

In the present embodiment, as shown in FIG. 2, a piston pressing force estimator 21 that inputs a detection signal of the motor rotation angle θ _m of the electric motor 11 and calculates an estimated value of the pressing force fp of the piston 1, A piston pressing force controller 22 that calculates a control command value so that the estimated value of the piston pressing force fp approaches the piston pressing force command value, and a pressing force that outputs a current command value for the electric motor 11 in accordance with the control command value A motor driver 24 that controls the drive power of the electric motor 11 by inputting the current conversion gain 23, the current command value, the detection signal of the motor rotation angle θ _m of the electric motor 11, and the detection signal of the motor current of the electric motor 11. Therefore, the operation of the electric motor 11 can be feedback-controlled so that the estimated value of the piston pressing force fp approaches the piston pressing force command value.

  In the present embodiment, a plurality of pistons 1 that face the non-rotating brake disk 9, a ball screw 15 that is rotatably connected to the piston 1, and the rotation of one electric motor 11 are transmitted to the plurality of ball screws 15. Therefore, the hysteresis caused by the friction torque loss of the speed reduction mechanism 10 and the ball screw / nut mechanism can be eliminated, and the actual piston pressing force can be accurately controlled. In addition, the number of electric motors used is halved compared to conventional devices, and the number of electric motor drivers and cables is reduced. Thereby, the reliability of the product can be improved and the cost of the product can be reduced.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The electric brake of the present invention can be used not only for braking aircraft wheels but also for other vehicles.

The block diagram of the electric brake which shows embodiment of this invention. The block diagram of a controller similarly. The diagram which shows a mode that the piston pressing force command value by the conventional control and an actual piston pressing force change.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piston 5 Electric actuator 6 Rotating brake disk 9 Non-rotating brake disk 10 Deceleration mechanism 11 Electric motor 15 Ball screw 21 Piston pushing force estimator 22 Piston pushing force controller 23 Pushing force current conversion gain 24 Motor driver

Claims (3)

A rotating brake disc that rotates with the wheels,
A non-rotating brake disc that is displaceable and non-rotatable toward the rotating brake disc;
A piston facing this non-rotating brake disc;
A ball screw rotatably connected to the piston;
A ball screw and nut mechanism for moving the piston forward and backward with respect to the non-rotating brake disc by rotation of the ball screw;
An electric motor that rotationally drives the ball screw;
Calculating an estimated value of the piston pressing force fp of the piston against the non-rotating brake disc according to the motor rotation angle θ _m of the electric motor;
An electric brake, wherein a control command value for the electric motor is feedback-controlled so that an estimated value of the piston pressing force fp approaches a piston pressing force command value. A piston pressing force estimator that inputs a detection signal of a motor rotation angle θ _m of the electric motor and calculates an estimated value of the pressing force fp of the piston;
A piston pressing force controller that calculates the control command value so that the estimated value of the piston pressing force fp approaches the piston pressing force command value;
A pressing force current conversion gain that outputs a current command value for the electric motor in accordance with the control command value;
Characterized in that a motor driver for controlling the driving power of the electric motor by inputting the detection signal of the detection signal and a motor current of said electric motor of the motor rotational angle theta _m of the electric motor and the current command value The electric brake according to claim 1. A plurality of the pistons facing the non-rotating brake disc;
The ball screw rotatably connected to the piston;
The electric brake according to claim 1, further comprising a speed reduction mechanism that transmits rotation of one electric motor to the plurality of ball screws.

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