Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D7/00—Steering linkage; Stub axles or their mountings
  • B62D7/06—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins
  • B62D7/14—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering
  • B62D7/142—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering specially adapted for particular vehicles, e.g. tractors, carts, earth-moving vehicles, trucks
  • B62D7/144—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering specially adapted for particular vehicles, e.g. tractors, carts, earth-moving vehicles, trucks for vehicles with more than two axles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D7/00—Steering linkage; Stub axles or their mountings
  • B62D7/06—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins
  • B62D7/14—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering
  • B62D7/148—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering provided with safety devices

Definitions

• the present invention relates to the technical field of the steering systems and more particularly to a steering system for a trailing axle of a vehicle and a corresponding method for steering a vehicle.
• the NLA can thereby be forcibly steered or adhesion-controlled, ie steered by the return movement of the wheels themselves.
• This additional NLA steering allows for smaller curve radii, resulting in greater maneuverability.
• the slip angle is reduced to the tire, causing the Tire wear of the vehicle is reduced.
• NLA active steering of the NLA is desired only at low speeds. At higher vehicle speeds, no steering of the NLA is desired, as this negatively affects stable driving.
• the NLA must be fixed at a certain vehicle-dependent speed, so as not to cause an unstable driving condition.
• the state of the art is that the NLA is articulated via a hydraulic cylinder.
• the oil is pumped into one or the other cylinder chamber via a pump that is driven by the internal combustion engine, depending on how the valves are switched.
• German patent application DE 103 51 482 AI shows a steering system in which a hydraulic hinged vehicle rear axle is held with an additional locking device in the current position or hinged back to a center position and then arrested adhesion-controlled.
• this requires more components and is therefore expensive;
• a lot of space is needed.
• the pump is also firmly flanged to the engine so that it is always operated. Therefore, especially in the straight-ahead driving, in which the vehicle is a long time, the hydraulic pump would be constantly driven, although this is not required. In this operating condition, the hydraulics generate losses that are not countered by added value. This is the demand for a lower fuel consumption of the vehicle opposite.
• German patent application DE 10 2006 008 436 AI shows a mechanically coupled multi-axle steering system, in which only a steering force is applied to the additional steering axle, if this is active - ie when steering lock - is needed.
• this system can only be implemented with great effort for a rear-axle steering, which is to be locked in straight ahead driving from a certain speed range.
• German patent DE 4414161 Cl a multi-axle steering system is described, in which a master cylinder is controlled. Depending on the position of the master cylinder on the front axle, the slave cylinder reacts on the rear axle.
• a disadvantage of this system is the direct dependence on the respective position of the master cylinder. Thus, there is no possibility of a speed-dependent influence on the rear axle with this system.
• the object of the present invention is to provide an improved steering system for a trailing axle of a vehicle, which as far as possible takes into account its current driving condition, which works energy-efficiently and reliably, and which is simple and inexpensive to implement.
• a trailing axle is to be understood in the following to mean any axle which follows the deflection of a steered axle and which can be arranged behind or ahead of a rigid rear or front axle, ie also as a leading axle.
• a steering system for at least one trailing axle of a vehicle, comprising: a steering angle sensor for detecting a steering angle of wheels of a front axle of the vehicle; a vehicle speed sensor for detecting a vehicle speed; an electric motor for driving a hydraulic pump, which is in turn connected to at least one working cylinder for articulating the wheels of the trailing axle; a control unit, which on the one hand communicates with or communicates with the steering angle sensor and the vehicle speed sensor, and on the other hand with the electric motor, and is adapted to determine from the steering angle and the vehicle speed a caster angle of wheels on the trailing axle of the vehicle, and to switch the engine based on this caster angle, the cylinder having a position sensor for detecting a center position of the piston thereof in which the caster wheels are in a straight-ahead position, and a pulse valve from a working position in response to the detected center position of the piston.
• an electro-hydraulic steering system for a trailing axle available, in which the steering wheel is not mechanically connected to the axis to be steered, ie its articulation of the trailing axle can take place independently of the front axle.
• this steering system is decoupled from the internal combustion engine, so that a needs-based control is guaranteed. Due to the few components at the same time minimizes the error rate of the steering system and also given a high spatial flexibility in their installation.
• the use of a pulse valve only a single control line is necessary to effect switching between its positions. Because the reversal of a pulse valve takes place by a pulse such as an electrical signal. The valve then remains in the switched position for so long, until a new impulse reverses the valve again.
• the generation of the pulse requires only a very small amount of energy, and both valve positions can be maintained without additional energy.
• an active steering is thus possible depending on the steering angle of the wheels of the front axle and the driving speed of the vehicle.
• the wheels of the trailing axle are at any time automatically, ie adhäsungsgetrieben from each deflection angle in their straight-ahead driving position and there also reliably blocked even without a complex electronics and / or hydraulics would be necessary even with a complete failure of the pump.
• the hydraulic fluid is discharged from one cylinder chamber of the working cylinder, while in the other cylinder chamber - without pump insert - liquid is sucked.
• the control unit of the steering system can be designed to switch the pulse valve in its normal position when a predeterminable driving speed is exceeded, and to switch the pulse valve into its working position when the predefined driving speed is undershot. In straight ahead at high speed, ie above the predetermined speed, so that the trailing axle is reliably durable and their control at low speed, ie below the predetermined speed, still possible, which increases the flexibility, safety and reliability of the steering system.
• the control unit of the steering system can also be designed to detect malfunctions, and, in the presence of a fault and in straight-ahead driving position of the wheels of the trailing axle to switch the pulse valve in its normal position. In the event of malfunctions that do not affect the position sensor and the triggering capability of the pulse valve, the steering system can thus be brought into a safe state at any speed. If the pulse valve is e.g. is at a trouble-free working pump, deflected wheels of the trailing axle and low speed in its working position, a fluid flow between the pump and cylinder is released, and the piston is movable via the pump.
• the piston is moved under adhesion-driven displacement of hydraulic fluid in the direction of its center position, in which the wheels of the trailing axle are in the straight-ahead driving position.
• the reaching of this center position is detected by the position sensor and subsequently a pulse is triggered by the control unit, which switches the pulse valve in its normal position, which interrupts any further exchange of hydraulic fluid to the working cylinder.
• This basic position of the impulse valve is also maintained if the vehicle should accelerate despite the failure of the pump in the sequence and should record a high driving speed.
• the control unit of the steering system can moreover be designed to activate the electric motor when a predeterminable driving speed is exceeded, so that the wheels of the trailing axle are brought into straight-ahead driving position, and after reaching the straight-ahead driving position, to switch the impulse valve to keep the trailing axle.
• the control unit of the steering system can further be designed to switch the electric motor de-energized when a predeterminable travel speed and a straight-ahead position of the wheels of the trailing axle is exceeded and to bring the pulse valve into its basic position.
• the Trailing axle is thus held in its center position, so that the wheels are in straight-ahead driving position. With an electric motor switched off in this position and the impulse valve in its basic position, the steering system no longer requires any further power consumption, which makes it extremely energy-efficient to operate.
• the at least one working cylinder can be designed as a single-acting cylinder whose hydraulic line to the pump requires only one control valve.
• the at least one working cylinder can also be designed as a double-acting cylinder or as a double-acting combination of two individual cylinders, which results in an improved power transmission, and at the same time a spatially flexible shoring is possible.
• a respective control valve is used to allow or to prevent an exchange of hydraulic fluid at each cylinder space.
• the volume compensation of different cylinder chambers of the at least one cylinder is preferably carried out via a combination of a 2-pressure valve and a fluid tank.
• a hydraulic fluid can be sucked in and conveyed, in order to effect a corresponding fluid compensation.
• the hydraulic fluid can be sucked in via the intake valves or the hydraulic fluid can be pumped back into the tank.
• two cylinders are used with identical volumes of the cylinder chambers, which does not necessarily a fluid tank is needed.
• the pump is designed as a reversibly operable pump or as a combination of a one-way operable pump with a valve block.
• a reversibly operable pump makes the least demands on the space requirements of the steering system, while a one-way operable pump requires a simpler electric drive.
• the valve can in principle be electromagnetically and / or hydraulically actuated in order to ensure high reliability.
• the above object is also achieved by a method for steering wheels of at least one trailing axle of a vehicle, in which a driving speed and a steering angle of wheels of a front axle of the vehicle are detected and from a caster angle of the wheels of the trailing axle is determined, the wheels of the trailing axle be articulated via a working cylinder having a position sensor which detects a center position of the piston in which the wheels of the trailing axle are in a straight-ahead position, and in response to this center position of the piston, a pulse valve from a working position in which a fluid flow between the working cylinder and the pump is released, is switched to a basic position in which a fluid flow between the working cylinder and the pump is prevented, so that the piston is hydraulically blocked in the straight-ahead position of the wheels of the trailing axle ,
• the position sensor can not only necessarily detect a center position, but each position of the piston, and it can be provided a controller that is in communication with the position sensor or can connect to this.
• the control unit can be designed so that it causes a straight-ahead of the wheels of the trailing axle, for example by activating the pump when exceeding a predetermined speed, and by switching the pulse valve and thus blocking the trailing axle when the piston of the working cylinder in its center position is, in which the straight-ahead position of the wheels of the trailing axle is reached.
• the center position of the piston does not necessarily have to correspond to its center position in the working cylinder.
• This initially provides an electro-hydraulically decoupled steering method for a trailing axle, in which the trailing axle can be articulated independently of the front axle.
• each articulated to the current driving situation articulation of the trailing axle is possible, which also opens energy saving potential and guarantees high reliability.
• a simple and reliable automatic, ie adhesion-controlled return of the wheels of a trailing axle in their straight-ahead position is possible, ie even if there is a fault in the pump or motor.
• the method may provide that when a predeterminable driving speed is exceeded, the pulse valve is switched to its basic position, and the pulse valve is switched to its working position when it falls below the predefinable driving speed.
• the trailing axle is reliably durable in straight ahead at high speed, ie above the predetermined speed and their control at low speed, ie below the predetermined speed still possible, which increases the safety and reliability of the steering system.
• a reliable, adhesion-driven return of the wheels of a trailing axle from any deflected position and their safe holding in a straight-ahead driving position without any energy expenditure is possible.
• the method may also provide that when a fault is detected and the trailing axle wheels are in the straight-ahead position, the pulse valve is switched to its home position. If there is a fault that does not affect the position sensor and the driving capability of the pulse valve, the steering system can thus be transferred to a safe state at high as well as at low speed.
• the method may also provide that, when a predeterminable travel speed is exceeded, the electric motor is activated, so that the wheels of the trailing axle are brought into the straight-ahead driving position and held there by the switching of the pulse valve.
• a more stable driving state can be realized when the vehicle is traveling at a higher speed than the predetermined speed.
• the method can also provide that when a specifiable vehicle speed is exceeded, and the straight-ahead position of the wheels of the trailing axle is reached, the electric motor is de-energized and the pulse valve is brought into its normal position.
• the energy efficiency of a corresponding steering system increases because at high speeds, neither the adhesion-driven return of the wheels of the trailing axle, nor their blockade in the straight-ahead driving position, nor the electric motor require an energy supply.
• the steering system according to the invention should preferably be used in a motor vehicle, in particular in a commercial vehicle.
• Fig. 1 is a functional diagram of a vehicle with an inventive
• FIG 2 is the functional diagram of the steering system according to the invention of Figure 1.
• a steering angle sensor Sa is provided for detecting a steering angle ⁇ of wheels Rv of a front axle Av
• a vehicle speed sensor Sv is provided for detecting a vehicle speed v.
• Their signals are transmitted via a signal line Wl a control unit C, which is designed for driving an electric motor M and thus directly operated reversible hydraulic pump P.
• the steering angle ⁇ can alternatively or additionally also picked up directly on the steering wheel and transmitted via a signal line W2 to the control unit C.
• control unit C is connected via a signal line W3 to a position sensor Sp of a double-acting cylinder Z which can move the running wheels Rn of a trailing axle An of the vehicle F to a trailing angle ⁇ .
• the steering system L is driven by the motor M only when active steering movement is required.
• the exporting cylinder Z is here a double-acting cylinder, which can also be designed as a synchronous or differential cylinder.
• a pulse valve I is arranged, which can be switched by an example electrical pulse between a closed basic position N and an open working position A back and forth.
• the pulse valve I remains in the switched position until a renewed pulse reverses the pulse valve I again. Both valve positions N, A can be held without further energy consumption.
• the hydraulic lines XI, X2 enter a connection with the pump P, and a position of the piston K and thus an articulation of the wheels Rn the trailing axle An is possible by means of the pump P.
• the position sensor Sp constantly detects the position of the piston K. If this is the case Position of the piston K reached in straight ahead, which is also referred to here as the center position G of the piston K, so can eg the control unit C, the pulse valve I switch to the normal position N. By this switching, the hydraulic lines XI, X2 are now closed to the cylinder chambers of the working cylinder Z. The piston K can be held without further external energy.
• the control unit C is connected via a signal line W4 with a valve control D of the pulse valve I in conjunction or can get in touch with this depending on the position of the piston K and thus the caster angle ß of the wheels Rn, and depending on a driving condition of the vehicle F , comprising, for example, steering angle, driving speed v, presence of an error case uA the pulse valve I to switch from its working position A to its normal position N, and vice versa.
• a driving condition of the vehicle F comprising, for example, steering angle, driving speed v, presence of an error case uA the pulse valve I to switch from its working position A to its normal position N, and vice versa.
• FIG. 2 shows the functional diagram of the steering system L of FIG. 1 on a larger scale. Drive at high speed
• the electric motor M When driving at high speed, the electric motor M can remain switched off and the axis An remains hydraulically, since pulse valve I is in its normal position N, and the piston K is thus hydraulically blocked.
• the electric motor M is driven by the controller C and the pulse valve I is in the working position A, i. It is a fluid flow between the pump P and cylinder Z possible.
• the steering angle ⁇ of the wheels Rv of the front axle Av or the steering angle of the steering wheel is detected by measurement and transmitted via the signal line Wl or W2 to the control unit C. With these and other values, e.g. of the vehicle speed v, the target displacement of the wheels Rn on the trailing axle An is calculated.
• the motor M which in turn is connected to the pump P, which conveys the oil through the hydraulic lines XI, X2 in the corresponding cylinder chamber is controlled by the control unit C, whereby a piston movement is triggered.
• the control takes place via a corresponding control algorithm until the setpoint at the trailing axle An is reached.
• the pulse valve I for example by means of an electro-magnetic valve control D connected to the holding the trailing axle An in the straight-ahead position of the wheels Rn as follows.
• the pulse valve I initially remains in the working position A and the motor M is switched off. If the wheels Rn of the trailing axle are deflected to, the axle forces act on the wheels Rn according to the radius of curvature, which is also referred to as AdPSsionsienken. If the vehicle F is brought out of cornering in a straight ahead, try the Achsschreibstell concept to move the steering in the direction of straight ahead. This movement is made possible by the pulse valve I located in operating position A until the piston K reaches the central position G, then the pulse valve I is switched over.
• a compensation of the hydraulic oil between the two cylinder chambers of the working cylinder Z can be done via the inactive pump P.
• the control unit C gives a pulse to the pulse valve I, so that this switches and locks the hydraulic oil in the working cylinder Z, thus preventing a movement of the piston K. If the error also affects the position sensor Sp and / or the valve control D, the trailing axle is linked to adhesion.
• other concrete technical embodiments of the steering system according to the invention are conceivable, which are in the knowledge and skill of the expert. It is important that the automatic mechanical return of the trailing axle is ensured in its center position in case of failure.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Transportation (AREA)
• Mechanical Engineering (AREA)
• Vehicle Body Suspensions (AREA)
• Steering Control In Accordance With Driving Conditions (AREA)
• Power Steering Mechanism (AREA)

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• 2012
  • 2012-08-23 DE DE102012107777.0A patent/DE102012107777B4/de active Active
• 2013
  • 2013-07-10 CN CN201380049528.1A patent/CN104661900B/zh active Active
  • 2013-07-10 WO PCT/EP2013/064587 patent/WO2014029555A1/de active Application Filing
  • 2013-07-10 BR BR112015003174-9A patent/BR112015003174B1/pt not_active IP Right Cessation

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