CN102556146A - Electric power steering transmission mechanism and electric power steering system - Google Patents

Abstract

The invention relates to an electric power steering transmission mechanism and an electric power steering system. The electric power steering transmission mechanism comprises a motor, a worm-and-gear transmission mechanism, a differential gear train mechanism, a gear-and-rack drive motor, and a steering trapezoidal mechanism, wherein the worm of the worm-and-gear transmission mechanism is driven by the motor; the gear of the worm-and-gear transmission mechanism is coaxially fixedly connected with a large sun gear of the differential gear train; a small sun gear of the differential gear train is coaxially fixedly connected with an automotive steering shaft; the center shaft of a planetary gear of the differential gear train is coaxially fixedly connected with the gear of gear-and-rack drive motor; and the rack of the gear-and-rack drive motor drives automotive wheels to change the direction through the steering trapezoidal mechanism. The electric power steering transmission mechanism solves the technical problems of the existing worm transmission mechanism during power transmission, such as steering lag, timeout, and poor hand feel of the steering wheel. The electric power steering transmission mechanism is good to speed reduction and moment increase by reducing the movement displacement and speed outputted by the rack, and solves the problem of convenient steering for drivers.

Description

A kind of electric power steering transmission device and electric boosting steering system

Technical field

The present invention relates to a kind of electric power steering transmission device and electric boosting steering system.

Background technology

Electric power steering (Electric Power Steering; EPS) system is a kind of brand new power electronics Fu; With respect to conventional hydraulic power steering (Hydraulic Power Steering; HPS) system, it has saving fuel, helps environmental protection, controlledly turn to plurality of advantages such as sensation, and has adapted to New Generation of Electric Vehicle and intelligent vehicle electronization, intelligent requirements.

The size of steering hardware installing space on the servodrive mechanism design considered automobile, it is simple, compact to try one's best on the structure, forward rotation efficient height and backwards rotation efficient is suitable, and guarantee that rotor inertia, friction and gap are as far as possible little.Therefore whether servodrive mechanism rationally directly can influence the performance of whole EPS system.Some at present external makers make the EPS finished product to the worm and gear reduction gearing mechanism.(Electric Control Unit ECU) forms this scheme by electrical motor, magnetic clutch, car speed sensor, torque sensor, worm gearing and electronic control unit.The power-assisted that electrical motor provides acts on steering shaft after amplifying through the worm gearing deceleration, and driver assistance person carries out handling maneuver.When high vehicle speeds does not need power-assisted or servo-steering to break down, can in time break off magnetic clutch and end power-assisted purpose to reach.Because the adhesive of magnetic clutch all needs the regular hour with separating, will inevitably cause the hysteresis that turns to and overtime.When needs provide power-assisted,, cause providing power-assisted to lag behind the steering reaction overlong time owing to need the time in the attracting process.Also there is a problem in this system, and mean speed equals the output behind the motor deceleration when be difficult to guaranteeing wheel steering.This can cause the bearing circle feel poor excessively.

Summary of the invention

The object of the invention provides a kind of electric power steering transmission device and electric boosting steering system; It adopts worm and gear-NGW differential gear train to carry out servodrive, has solved turning to that existing worm gearing carries out that servodrive brought and has lagged behind and technical matters overtime, that the bearing circle feel is poor excessively.

Technical solution of the present invention is:

A kind of electric power steering transmission device is characterized in that: comprise electrical motor, Worm and worm-wheel gearing, differential gear train mechanism, rack-and-gear drive motor, tie rod linkage; The worm screw 1 of said Worm and worm-wheel gearing is driven by electrical motor 9; The worm gear 2 of said Worm and worm-wheel gearing and the big sun wheel of differential gear train 5 coaxial being connected; The small sun gear 3 of said differential gear train and steering axles 8 coaxial being connected; The center shaft of the satellite gear 4 of said differential gear train and the gear of rack and pinion drive mechanism 6 coaxial being connected; The tooth bar 7 of said rack and pinion drive mechanism turns to through turning to ladder type mechanism drive wheels.

A kind of electric boosting steering system comprises electric power steering transmission device and control system, and said control system comprises the speed of a motor vehicle, moment of torsion and rotary angle transmitter and electronic control unit ECU; It is characterized in that: said electric power steering transmission device comprises electrical motor 9, Worm and worm-wheel gearing, differential gear train mechanism and rack and pinion drive mechanism; The worm screw 1 of said Worm and worm-wheel gearing is driven by electrical motor 9; The worm gear 2 of said Worm and worm-wheel gearing and the big sun wheel of differential gear train 5 coaxial being connected; The small sun gear 3 of said differential gear train and steering axles 8 coaxial being connected; The center shaft of the satellite gear 4 of said differential gear train and the gear of rack and pinion drive mechanism 6 coaxial being connected; The tooth bar 7 of said rack and pinion drive mechanism is used for drive wheels and turns to; Said electronic control unit ECU according to the speed of a motor vehicle, moment of torsion and and the vehicle data that provides of rotary angle transmitter, one of control motor 9 output turn to identical auxiliary torque with the bearing circle hand-power.

The present invention has following advantage:

1, it is consistent or approaching need not satisfy the rotating speed of rotating speed and bearing circle behind the motor deceleration.Differential gear train mechanism has two degree of freedom, and promptly given two input motions can have definite output movement.When chaufeur turned to, the mean speed that different people acts on the bearing circle was different, and different road conditions when turning to mean speed also different.And the electrical motor of selecting can only provide the rotating speed of confirming numerical value according to fixing transmitting ratio.When directly adopting the worm gearing power-assisted, then preferably require two tachometer values equal or approaching, otherwise the steering shaft life-span is reduced.Lift a simple example: people pulls a cart harder, if a guy's help is drawn together, the muscle power that then everyone paid can obviously reduce.But precondition must let two people act in agreement, and promptly will guarantee that still the degree of freedom of car is 1 after two people's combineds action.

2, electrical motor not during power-assisted differential gear train be converted into planet circular system, reduce from moving displacement and the speed of tooth bar output, help deceleration and increase square, solved and make chaufeur turn to light problem.

3, worm and gear-NGW differential gear train (EPS) relies on to rotate in the train and compares α ₁, α ₂Design, make chaufeur can predict motor force shared percentum in whole load, electrical motor has overcome the load that differential gear train separates.Therefore the EPS system can improve manoeuvereability of automobile well.

When 4, the power-assisted input being arranged, under the identical bearing circle angular transposition input, rack displacement, speed are all bigger.The chaufeur problem of steering wheel rotation significantly in the time of can solving urgent big corner like this and turn to.

5, it is big to have an alerting ability, can be prone to satisfy the motor turning performance demands, thereby have comparatively wide application prospect.

Feed back to the moment of bearing circle when 6, mechanism of the present invention can effectively reduce non helping hand, hired roughneck's phenomenon under the power-assisted failure conditions on the actv. solution potted road surface, and make that the hand-power that feeds back on the bearing circle is level and smooth, can not cause sense of fatigue to chaufeur.

Description of drawings

Fig. 1 is a structural principle scheme drawing of the present invention;

Fig. 2 is a structural representation of the present invention;

Fig. 3 is a bearing circle angular transposition change curve in time;

Fig. 4 is for affacting the corner change curve of sun wheel 5 behind the motor deceleration;

Fig. 5 is for having the power-assisted hour rack along X axial translation and speed change curve in time;

Fig. 6 is the non helping hand hour rack along X axial translation and speed change curve in time;

Fig. 7 is the structural representation after the present invention and the Ackerman steering mechanism combination.

Wherein: the 1-worm screw; The 2-worm gear; The 3-small sun gear; The 4-satellite gear; The big sun wheel of 5-internally toothed annulus structure; Gear in the 6-rack and pinion steering gear; Tooth bar in the 7-rack and pinion steering gear; The 8-steering axles; The 9-electrical motor, the H-pinion carrier.

The specific embodiment

Electric boosting steering system comprises electric power steering transmission device and control system, and control system comprises the speed of a motor vehicle, moment of torsion and rotary angle transmitter and electronic control unit ECU; The electric power steering transmission device is made up of electrical motor, a cover Worm and worm-wheel gearing, a cover differential gear train mechanism, set of gears rack mechanism and steering trapezium.Propulsion source is respectively electrical motor 9 and affacts the actuating force on the bearing circle.The small sun gear 3 of differential gear train is contained in and turns on the input shaft, promptly on the steering axles.Big sun wheel 5 is coaxial with worm gear 2.Therefore electrical motor drives big sun wheel 5 motions through the one-level worm gear box.Two inputs of differential gear train are respectively bearing circle moment from small sun gear 5 inputs, and electrical motor power-assisted square is from big sun wheel 5 inputs, and synthetic motion is exported by pinion carrier H.Its principle of work is according to vehicle data such as the speed of a motor vehicle, moment of torsion and wheel steering angle sizes; Electronic control unit ECU provides one to turn to identical auxiliary rotating torque with the bearing circle hand-power according to depositing definite control policy driving motor in advance in, and utilizes the synthetic front-wheel steering angle that obtains of motion of differential gear train.Adopt this scheme, reduced the transmitting ratio of steering swivel system indirectly, thereby reduced the manual steering angle, and then reduce the merit that turns to of chaufeur consumption.When electric weight not enough, in the time of promptly need adopting the manual steering condition because worm gearing is designed to the reversing sense self-locking mechanism, so the time big sun wheel 5 take turns fixing.Worm gearing is not worked in such cases, and differential gear train mechanism is converted into planetary wheel mechanism.Handling maneuver drives small sun gear 5 from bearing circle and rotates as input, and big sun wheel 5 is motionless, and motion is still exported from pinion carrier H.

The principle of the invention:

1, worm and gear-NGW differential gear train motion analysis

If the rotating speed of small sun gear 5 is n ₃, the rotating speed of big sun wheel 5 is n ₅, the rotating speed of pinion carrier H is n _H, the number of teeth of small sun gear 5,5 is respectively Z ₃, Z ₅, moving by the differential gear system than having:

$i_{35}^H=\frac{n_3-n_H}{n_5-n_H}=-\frac{Z_5}{Z_3}---\left(1\right)$

Put in order:

$n_H=\frac{Z_3}{Z_3+Z_5}{n}_3+\frac{Z_5}{Z_3+z_5}{n}_5---\left(2\right)$

Know that from formula (2) rotating speed of pinion carrier H is that the steering shaft rotating speed is arrived in the front-wheel equivalence in this scheme, its value is synthetic for manual steering speed and motor speed, and obviously, this scheme has two degree of freedom, as manual steering rule n ₃Confirm, and motor speed is when changing, the front-wheel steering speed that obtains after synthetic also changes thereupon, therefore can obtain different steering swivel system output speed n through the rotating speed of adjusting electrical motor independently _H, be adjustable so turn to sensitieness under the scheme.When electrical motor power-assisted not, during promptly pure manual steering, big sun wheel 5 is motion (n not ₅=0), at this moment:

$n_H=\frac{Z_3}{Z_3+Z_5}{n}_3---\left(3\right)$

Can know that from formula (3) because the deceleration effort of differential gear train, transmitting ratio was less than 1: 1 when making pure manual steering; Thereby the manual steering sensitieness descends; This is unfavorable to the safety of high vehicle speeds lower-pilot, and this solves through the output speed of adjustment electrical motor with regard to requiring, so can increase energy consumption.Make in the formula (2):

${\mathrm{\&alpha;}}_1=\frac{Z_3}{Z_3+{\mathrm{<figure-callout\; id="5"\; label="Z"\; filenames="HDA0000039333390000032.png"\; state="\{\{state\}\}">Z</figure-callout>}}_5}$ ${\mathrm{\&alpha;}}_2=\frac{Z_5}{Z_3+{\mathrm{<figure-callout\; id="5"\; label="Z"\; filenames="HDA0000039333390000032.png"\; state="\{\{state\}\}">Z</figure-callout>}}_5}$

And be that 0 integration gets to the following formula initialization:

θ _H＝α ₁θ ₃+α ₂θ ₅ (4)

Know by the front input: θ ₃=θ _h, θ ₅=θ ₂=θ _m/ G gets its substitution formula (4):

θ _H＝α ₁θ _h+α ₂θ _m (5)

Can get the statics equation by the principle of virtual displacement:

$\left\{\begin{array}{c}{\mathrm{\&tau;}}_H={\mathrm{\&tau;}}_h+{\text{\&tau;}}_m\\ {\mathrm{\&tau;}}_m={\mathrm{\&alpha;}}_2{\mathrm{\&tau;}}_H\\ {\mathrm{\&tau;}}_h={\mathrm{\&alpha;}}_1{\mathrm{\&tau;}}_H\end{array}\right.---\left(6\right)$

Can see that from kinematical equation formula (4) angular transposition of output pivoted arm H is the stack of small sun gear and motor angle position.Here α ₁, α ₂Be that gear rotates ratio, they are determined by the sun wheel number of teeth, the satellite gear number of teeth and the center gear number of teeth jointly.θ _HBe the output corner of differential gear train, θ ₃, θ ₅, θ ₂Represent sun wheel 3 respectively, the corner of sun wheel 5 and worm gear 2, θ _h, θ _mBe respectively bearing circle and electrical motor input corner.τ _h, τ _mAnd τ _HThe virtual displacement of representing bearing circle, electrical motor and pinion carrier H respectively.With the electrical motor rotational angle theta _mAs the function of the chaufeur corner and the speed of a motor vehicle, establishing the electrical motor DC current gain is K _h, it is following to get the stable state equation of change:

θ _m＝K _b·f(θ _h)·f(V) (7)

Quiet equation (6) by gear train can know that there is similar statics characteristic in system with the manual steering system.Differential gear train relies on and rotates transmitting ratio α in the train as a moment of torsion disengagement gear ₁, α ₂Design, make the chaufeur can predict motor force shared percentum in whole load, electrical motor has overcome the load that differential gear train separates, and makes it turn to definite position.Therefore, differential gear train is actually another kind of work-saving device, and it reduces the load transmitted from rack pinion, thereby it is light to make that chaufeur turns to.

2, dynamics analysis

Make the center gear of wheel steering axle and differential gear train as a whole, front-wheel and pinion carrier are done as a whole, and to steering shaft it are carried out dynamics analysis to the cornering resistance of front-wheel and rotor inertia equivalence, can obtain following kinetic model:

Formula (8) but be the non-secondly differential equation of the second order of a depression of order, wherein do not contain θ _h, in addition

Then the following formula deformable does

Utilize the non-secondly differential equation general solution of single order to get:

$X=e^{-\frac{(b_1+b_2)\mathrm{<figure-callout\; id="1"\; label="t\; J"\; filenames="HDA0000039333390000011.png"\; state="\{\{state\}\}">t</figure-callout>}}{J_{}}}(\&Integral;\frac{T_h\left(t\right)-{\mathrm{\&alpha;}}_1{T}_r\left(t\right)}{{\mathrm{<figure-callout\; id="1"\; label="J"\; filenames="HDA0000039333390000011.png"\; state="\{\{state\}\}">J</figure-callout>}}_1+J_2}\&CenterDot;e^{\frac{(b_1+b_2)\mathrm{<figure-callout\; id="1"\; label="t\; J"\; filenames="HDA0000039333390000011.png"\; state="\{\{state\}\}">t</figure-callout>}}{J_{}}}\mathrm{dt}+C)---\left(11\right)$

The X integration is got:

${\mathrm{\&theta;}}_h=\&Integral;e^{-\frac{({\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA0000039333390000011.png"\; state="\{\{state\}\}">b</figure-callout>}}_1+b_2)\mathrm{<figure-callout\; id="1"\; label="t\; J"\; filenames="HDA0000039333390000011.png"\; state="\{\{state\}\}">t</figure-callout>}}{J_{}}}(\&Integral;\frac{T_h\left(t\right)-{\mathrm{\&alpha;}}_1{T}_r\left(t\right)}{{\mathrm{<figure-callout\; id="1"\; label="J"\; filenames="HDA0000039333390000011.png"\; state="\{\{state\}\}">J</figure-callout>}}_1+J_2}\&CenterDot;e^{\frac{(b_1+b_2)\mathrm{<figure-callout\; id="1"\; label="t\; J"\; filenames="HDA0000039333390000011.png"\; state="\{\{state\}\}">t</figure-callout>}}{J_{}}}\mathrm{dt}+C)\mathrm{dt}---\left(12\right)$

In like manner equation (9) but also be the differential equation of a depression of order, solve top

Substitution can obtain θ _mExpression formula:

Wherein, J ₁Be rotary inertia of steering wheel, J ₂Be sun wheel 3 rotor inertias, J ₃Rotor inertia for satellite gear.b ₁Be bearing circle damping coefficient, b ₂Be sun wheel 3 damping coefficients, b ₃Be satellite gear damping coefficient, b ₄Damping coefficient, θ for pinion carrier _hBe steering wheel angle, θ _mThe corner of electrical motor, T _hFor turning to hand-power square, T _mElectrical motor power-assisted square, T _rBe the wheel steering resisting moment.Can know that by formula (8), (9) power-assisted that electrical motor provides must overcome α ₂Steering resisting torque doubly could change self cireular frequency and angular acceleration, and then the steering handwheel hand-power is exerted an influence, and this influence is at J ₂, b ₂Under the less situation and not really remarkable, and always some cornering resistance according to fixing α ₁Multiple is assigned on the hand-power.So under this transmission device scheme, vehicle can both guarantee to turn to the existence of hand-power when any speed of a motor vehicle is gone, promptly turn to the existence of " feel " ^{[5] [6]}The electrical motor rotational angle theta has further been verified in formula (12), (13) _mShould be with steering wheel angle θ _hChange this rule, visible θ _h, θ _mTwo parameters not only and T _h, T _rTwo variablees are relevant with the constant of decision such as system architecture about also.

Fig. 3 of the present invention and Fig. 4 have provided bearing circle at given input motion, electrical motor have assist exercise and with non helping hand when motion, the moving displacement of output tooth bar and the change curve of speed.Displacement in the straight-line motion on the emergency turn hour rack and velocity curve, getting direction, to fold the rank time be 0.2 second, maximum angular displacement 72 degree, it is 0.4 second that electrical motor plays the rank time, maximum angular displacement is 186 degree, variation in angular displacement curve such as Fig. 3 and shown in Figure 4.Fig. 3, the equal express time unit of abscissa second of 4, ordinate is all represented the angular unit radian.

Above-mentioned input representes that bearing circle received the input of corner suddenly in preceding 0.2 second, and corner is 0 degree in the time of the 0th second, corner 72 degree in the time of the 0.2nd second, and not input At All Other Times is not so the angular transposition curve changed promptly parallel and abscissa after 0.2 second.In like manner affact the corner on the sun wheel 5 behind the motor deceleration, in preceding 0.4 second, receive a corner input suddenly, the 0th second corner is 0 degree, and corner reached 186 degree in the 0.4th second.Tooth bar output displacement and velocity curve such as Fig. 5 and shown in Figure 6.Solid line among Fig. 5 representes that rack displacement changes in time, and dotted line representes that tooth bar speed changes in time.When electrical motor not during power-assisted, with above-mentioned Step function input, the displacement and the velocity curve that affact on the tooth bar are as shown in Figure 6 equally for bearing circle.

Comparison diagram 5 can be known with Fig. 6, imports with definite movement relation when bearing circle, and the displacement and the speed generation significant change of tooth bar under two kinds of situation of power-assisted and non helping hand are arranged.Bearing circle and electrical motor movement relation are as previously mentioned in the literary composition; By figure (5) know when electrical motor with the jump function power-assisted, and reach maximum 186 when spending at 0.4 second assisted electric machine corner, maximum displacement is 31mm on the tooth bar; Do not move since 0.4 second tooth bar, its displacement does not change in time.Become big gradually and then be reduced to 0mm/s from little earlier at whole process medium velocity, know that by Fig. 6 speed is maximum at 0.15s, its value is 116.7mm/s.Known when electrical motor power-assisted not by Fig. 6, and the bearing circle rule is when constant, tooth bar reaches maximum displacement in 0.2 second, and its maximum displacement is 3.8mm only.Maximum speed appears at 0.1s, and maxim is 29.1mm/s.Relatively two kinds of situation can obviously be seen, according to input mode in the literary composition, and not about 1/8 when not having the displacement of power-assisted hour rack to be merely power-assisted, speed is about 1/4 when power-assisted is arranged.Know that by above analysis when the bearing circle characteristics of motion was constant, the variation of electrical motor assist exercise rule directly influenced the time that the moving velocity maxim occurs on the tooth bar.Therefore in practical application, can obtain the different rack speed change curves, thereby satisfy the various requirement [8] in the steering procedure through the assist exercise rule of adjustment electrical motor input.Above-mentioned curve shows is introduced differential gear train mechanism in transmission device; Can not only accomplish the displacement that the wheel steering hour rack should move in a short period of time, and can adjust electrical motor assist exercise rule through control system and reach the requirement that turns to that adapts to flexibly under the different situations.

Claims (2)

1. an electric power steering transmission device is characterized in that: comprise electrical motor, Worm and worm-wheel gearing, differential gear train mechanism, rack-and-gear drive motor, tie rod linkage; The worm screw of said Worm and worm-wheel gearing is by direct motor drive; Coaxial being connected of big sun wheel of the worm gear of said Worm and worm-wheel gearing and differential gear train; The small sun gear of said differential gear train is connected with steering axles is coaxial; The center shaft of the satellite gear of said differential gear train is connected with the gear of rack and pinion drive mechanism is coaxial; The tooth bar of said rack and pinion drive mechanism turns to through turning to ladder type mechanism drive wheels.

2. an electric boosting steering system comprises electric power steering transmission device and control system, and said control system comprises the speed of a motor vehicle, moment of torsion and rotary angle transmitter and electronic control unit; It is characterized in that: said electric power steering transmission device comprises electrical motor, Worm and worm-wheel gearing, differential gear train mechanism and rack and pinion drive mechanism; The worm screw of said Worm and worm-wheel gearing is by direct motor drive; Coaxial being connected of big sun wheel of the worm gear of said Worm and worm-wheel gearing and differential gear train; The small sun gear of said differential gear train is connected with steering axles is coaxial; The center shaft of the satellite gear of said differential gear train is connected with the gear of rack and pinion drive mechanism is coaxial; The tooth bar of said rack and pinion drive mechanism is used for drive wheels and turns to; Said electronic control unit according to the speed of a motor vehicle, moment of torsion and and the vehicle data that provides of rotary angle transmitter, one of control motor output turns to identical auxiliary torque with the bearing circle hand-power.

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