FR2523057A1 - METHOD FOR AVOIDING SKATING OR SLIDING BETWEEN POWER WHEELS AND GROUND IN DRIVING SYSTEMS OF MULTI AXIS TYPE VEHICLES WITH HYDROSTATIC POWER TRANSMISSION - Google Patents

Abstract

PROCESS FOR AVOIDING SLIDING OR SLIDING BETWEEN DRIVE WHEELS AND THE GROUND IN DRIVE SYSTEMS OF VEHICLES OF THE MULTI-AXLE TYPE WITH HYDROSTATIC POWER TRANSMISSION. THE PROCESS IS CHARACTERIZED BY THE STEPS CONSISTING OF CONTINUOUSLY CALCULATING THE SPEED OF THE WHEELS OF EACH AXLE BASED ON THE INSTANTANEOUS VALUES OF THE CONTROL PARAMETERS NECESSARY FOR THE TRANSMISSION OF HYDROSTATIC POWER, SUCH AS THE SPEED OF THE MOTOR AT THE NUMBER MINUTE), THE STROKE A OF THE PUMP, THE DISPLACEMENT A OF THE MOTOR AND OR THE HYDRAULIC PRESSURE P REIGNING IN THE POWER TRANSMISSION, TO COMPARE THIS CALCULATED SPEED WITH THE SPEED OF AN AXLE OF THE VEHICLE WHICH IS NOT DRIVEN OR TURNS FREELY AND CREATE, WHEN A DIFFERENCE IN SPEED EXCEEDS A DETERMINED MINIMUM LIMIT AND LASTS LONGER THAN A PREDETERMINED MINIMUM, IS SENT, AN OUTPUT SIGNAL SENT TO THE CONTROL SYSTEM TO REDUCE THE HYDRAULIC PRESSURE IN THE TRANSMISSION, POWER A PREDETERMINED PERIOD OF TIME.

Description

252305 '

  1. The present invention relates to a method for

  avoid slippage or slippage between the drive wheels.

  these and the soil or support, used in

  vehicle train, particularly of the multi-axle type with hydrostatic power transmission, comprising at least one hydraulic pump driven by a drive power source such as an internal combustion engine running at a predetermined speed and at least one hydraulic motor, the hydraulic pressure of

  said hydrostatic power transmission being

  By a control system for changing the driving pulse of said hydraulic motor In vehicle driving systems, it may happen that the driving wheels slide or skid on the surface or the drive carrier if the power of drive or the braking force which is applied to the wheels or axles is too great compared to the grip force against said drive surface In particular when it is a steel-against-steel friction, as it is the case for railway vehicles, adhesion is

  weak and can easily slip or

  Naturally, skidding, when braking these railway vehicles, means a reduction in safety and high wear of the wheels, resulting in a high cost of maintaining said wheels. Many suggestions have been made to avoid slip or slip between the driving wheels and the support but they

  have been either insufficiently effective or implied

  very complex control systems and this

  expensive Electric traction motors for

  railroad vehicles, such as those of the ASEA thyristor locomotives, were equipped with a load cell device called "PRESSDUKTOR" cooperating with a

  wheel bogie reaction In the limit zone where the

  The bogie begins to oscillate in a characteristic manner and these oscillations are transmitted to the reaction rod and can therefore be detected by the load cell With regard to the hydrostatic power transmissions for drive systems. of

  vehicles covered by the present invention, no proposals

  However, it was not done to prevent slippage or

  slip between the driving wheels and the support

  whether it is hydrostatic power transmissions of this type, it is actually even more important to avoid

  slip or slip only in the case of

  traction drives because fluctuations in drive or braking power could be

very important.

  The main object of the present invention is to

  a procedure to prevent slippage or

  wheel and drive wheel slip and according to the invention

  This goal is achieved by means of the steps of continuously calculating the wheel speed of each axle on the basis of the instantaneous values of control parameters necessary for the transmission of hydrostatic power, such as engine speed, travel speed, and

  the pump, the displacement of the motor and / or the heat

  hydraulic system in the transmission of power, to compare this calculated speed with the speed of an axle of the vehicle which is not driven or turns freely and

  create, when there is a difference in speed exceeding

  a fixed minimum limit and of longer duration than a predetermined minimum duration, an

  sent to the control system to reduce the heat pressure

  hydraulics in power transmission, during a

predetermined period of time.

  Thanks to the invention, the safety is clearly increased.

  when braking vehicles with driving systems

  hydrostatic power transmission, and at the same time the acceleration and

  traction force while making them more regular.

  Thanks to the improvement of the braking capacity, the

  your wheels is less expensive, especially with regard to

  railway vehicles, and overall

  This process can be applied to control systems

  of hydrostatic power transmissions having 3.

  recourse to very simple measures and therefore inexpen-

  teuses. By way of example, the invention will be described in more detail with reference to the accompanying drawings, which

  part of the description, and in which:

  Fig 1 is a schematic perspective view of a hydrostatically driven train,

  Fig 2 is a block diagram of the commands of a system

  hydrostatic drive system used in the above-mentioned train, and Fig 3a and 3b finally represent the time relationship of the control parameters necessary to

  the hydrostatic power transmission according to the invention

tion.

  As can be seen from the drawings,

  assigned according to the invention will be described essentially then

  applied to a hydrostatic drive system

  In this system, the drive power is constituted by a combustion engine, in particular an internal combustion engine 1 which is connected in such a way that

  suitable for a pair of hydraulic pumps 2

  2 each drive a hydraulic motor 3, which motors each drive an axle 5 through gears 4 In the illustrated embodiment, the

  hydraulic pumps 2 are axial piston pumps con-

  where the stroke O Cp can be modified by setting the

  rotation, while the hydraulic motors 3 have a constant stroke C Lm (although a variable stroke

  engines is perfectly possible).

  To control the training pulse as it

  is developed by hydraulic motors, there are also

  This system comprises a number of suitable and known but not illustrated detectors for the purpose of detecting the control parameters necessary for the transmission of the hydrostatic power, such as, for example, a control system which is housed to a large extent in a control unit.

  the speed of the drive motor N, the running of the pumps

  pes% Op, the stroke of motors "C and also the pressure p m 4,

  hydraulic P of the power transmission if it is

  In addition, a rotation detector is

  illustrated, intended for an axle 7 of the train which is not

dragged and turns freely.

  On the basis of the instantaneous values of said control parameters which are recorded by the detectors, the speed of the wheels of each axle 5 is calculated continuously in the control unit 6 according to the invention, and

  compare it to the speed of the untrained axle and

  freely 7 If there is a difference between these

  speeds in the control unit 6, this difference de-

  during the fact that one or more of the driving axles rotate either at a higher speed than the non-driven axle 7, that is to say, slip during acceleration, or at a lower speed than that of this axle , i.e., slide in the locked state along the support

  during braking, and when we notice that this diffi-

  exceeds the limit value which has been predetermined and lasts, moreover, for a duration exceeding a predetermined minimum duration, an output signal is triggered

  by the control unit 6 to reduce the hydraulic pressure

  sufficiently to prevent slippage or slippage, that is, in order to achieve equality between

  In other words, it can be said that the equi-

  free of currents in the hydrostatic drive system

  The value Pl of the pressure in the system is restored.

  hydrostatic drive system which prevailed when this difference in speed was detected and the reduction of the primed pressure is stored in a memory unit of the control unit 6, and after a predetermined duration,

  the latter emits a new output signal to increase

  Maintain the hydraulic pressure P, but up to a level Pr located substantially below the initial value Pi Then we have the assurance that said slip or slip condition is not immediately canceled After another

  predetermined period of time, the control units pro-

  finally duet a new exit signal to bring back

  the hydraulic pressure at the value Pi.

  5. To give practical examples of the values that are found with the control method according to the present invention, reference is made to FIG.

  and the diagrams that these represent and which concern

  the most important control parameters, and it is clear from this figure that a comparison is made between the actual speed and the calculated wheel speed at 64 millisecond intervals, and when there are differences exceeding a predetermined minimum value, the hydraulic pressure P prevailing in the power transmission is reduced so as to terminate the slippage or slip between the axles of the drive wheels and the support After a predetermined period of time, the control system increases again the hydraulic pressure, but only up to a level Pr representing about 80% of Pi This reduced pressure is maintained for a predetermined period, in the

  this case for 10 seconds, after which a new

  The output signal from the control system reduces the

  hydraulic pressure at the value Pi.

  The advantages of the control method according to the present

  Invention First, it is sufficient to have one

  that measuring value, namely the speed of a single axle not driven or rotating freely 7 to perform the command In other words, a single speed detector is necessary, which implies significant reductions

  compared to the pre-order control methods

  Previously used and requiring the measurement of the speed on each drive axle These speed measuring equipment are relatively expensive in themselves and also fragile, and they require regular maintenance With particular regard to the application of the system to road vehicles Many of the axles are motors, the method of the invention makes it possible to achieve a significant reduction in costs. In addition, it is desirable for the speed of the combustion engine 1 to be kept constant, and this result can easily be achieved. By substantially eliminating slippage or slippage between the wheels and the support, the maintenance costs of the wheels of the vehicle are also substantially reduced, these costs being in many cases relatively high. As mentioned in the preamble, security is also increased during the

  braking and more acceleration can be achieved

  aunt and more regular of the vehicle.

  Those skilled in the art will also understand that

  is not limited to the above description and

  that it can be modified in various ways without going out

  of the scope of the appended claims Thus,

  a single hydraulic pump can result in several

  In addition, the method is also not limited to railroad vehicles and can be used in other types of vehicles with hydrostatic power transmission, such as buses. 7

R E V E N D I CA T IO N S

  1 Method to prevent slippage or

  between the driving wheels and the ground or support,

  in vehicle drive systems, particularly in

  specifically of the multi-axle type with transmission

  hydrostatic power, comprising at least one heat pump

  hydraulics driven by a driving power source

  such as an internal combustion engine running at a predetermined speed (N) and at least one hydraulic motor,

  the hydraulic pressure (P) of said power transmission

  hydrostatic system being controlled by a

  to change the driving pulse of said motor

  characterized by the steps of calculating

  continuously check the wheel speed of each axle

  based on the instantaneous values of comm parameter

  necessary for the transmission of hydrostatic power

  such as the engine speed (rpm), the stroke (ce) of the pump, the displacement (W) of the engine and / or the hydraulic pressure (P) in the power transmission, to compare this calculated speed to the speed of an axle of the vehicle that is not driven

  or turns freely and create, when there is a difference

  speed limit exceeding a specified minimum limit and having a duration longer than a predetermined minimum duration,

  an output signal sent to the control system to re-

  the hydraulic pressure (P) in the transmission of

  power, for a predetermined period of time.

  Process according to Claim 1, characterized in that

  the value (Pi) of the hydraulic pressure of the trans-

  power mission that reigns when the reduction begins

  pressure is stored in a memory unit.

  of the control unit (6) and that the heat pressure

  hydraulic system, after being reduced for a predetermined period of time, is again increased, but up to a value (Pr) lower than the initial pressure (Pi), this intermediate pressure value being maintained during

  another predetermined period of time before the pres-

  hydraulic pressure is increased again to its value

initial (Pi).