GB2227079A

GB2227079A - Method for the supplementary hydraulic drive of wheels on a vehicle

Info

Publication number: GB2227079A
Application number: GB8928472A
Authority: GB
Inventors: Udo Teske; Uwe Rathje; Horst Limberg; Herbert Ziplies
Original assignee: O&K Orenstein and Koppel GmbH
Current assignee: CNH Industrial Baumaschinen GmbH
Priority date: 1988-12-16
Filing date: 1989-12-18
Publication date: 1990-07-18
Anticipated expiration: 2009-12-18
Also published as: DE3842405C2; GB8928472D0; FR2640558A1; JPH02237818A; SE8902893L; CA2005691C; CA2005691A1; SE466301B; GB2227079B; FR2640558B1; SE8902893D0; DE3842405A1

Description

C.

Vehicle and method for the supplementary hydrsiulic drive of wheels on a vehicle The invention relates to a vehicle and a method for the supplementary hydraulic drive of wheels on a vehicle.

s DE-OS 36 20 163 describes a method for the control or regulation of a hydrostatic drive for the front wheels of a vehicle having a combustion piston engine and a mechanical, hydrodynamic or hydrostatic transmission for the rear wheel drive. An electronic/electrohydraulic device is used to control the torque of the front wheels through regulation of the in-pump pressure, by means of a pressure regulating adjustment and in response to the revolution rate of the front and rear wheels. The vehicle has revolution rate measured-value pick-ups associated with at least the rear wheels, an electronic device, optionally with a final attack-control element, a torque setting device, a travel direction switch and a pressure regulating valve connected to a hydraulic pump. The measured revolution rate of the rear wheels is compared, in the electronic device, with an adjustable control characteristic contained in a programmable module. A control magnitude for the pressure regulating valve of the hydraulic pump is derived from the respec tive measured value comparison, and is fed as a control current to the pressure pilot valve of the pressure regulating valve, and the pressure in the hydrostatic drive for the front wheels., consisting of the pump and U the wheel motors, is regulated accordingly.

A disadvantage of the above-mentioned method is that considerable cost is involved in the regulation of the front wheel drive of the construction vehicle. Further, a controlled distribution of the driving forces to the front and rear axles is not possible.

DE-PS 33 31 651 describes a method for the selective supplementary hydraulic drive of wheels on a vehicle, in addition to the main drive wheels driven by an eng-Ine through a torque converter or gearbox, by the automated control of a closed hydraulic operating circuit, with -wheel motors fed by a adjustable pump, and with a control pump, the flow or pressure of the operating fluid being controlled by the switchable control pump flow.

Superimposed on the operating fluid flow control, the operating fluid pressure is regulated according to the curve of a predetermined function selectable in response to the ratio between the output revolution rate of the engine and the output revolution rate of the converter or the gearbox.

According to a regulating method of this type, the operating pressure of the operating circuit is determined by means of a predetermined step-like function. The disadvantage of this is that as a result of the regulation not being sharply-tunable, the additionally driven front wheels either lead or trail the rear wheels.

The problem on which the invention is based is that of providing, at low cost, a supplementary drive for the 21 r, _ 1 '. -1. ' front wheels of vehicles, which is capable of withstand ing the rough operation of construction vehicles and also ensures a controlled distribution of the drive load to the front and rear axles.

According to the present invention, there is provided a method for the additional hydraulic drive of wheels on a vehicle, to main drive wheels actuated by a combustion engine by way of a torque converter and a transmission, with front wheel motors fed by means of automatic control of a closed hydraulic operating circuit by an adjusting pump and with the adjusting and control pump likewise driven directly by the combustion engine, wherein superimposed on the operating fluid flow control the operating fluid pressure is regulated according to the course of functions which are electronically stored in and can be called up from a function former in response to the ratio N AE of the converter output revolution rate NA or transmission output revolution rate N GA to the converter input revolution rate NE, charac- terised in that the front axle moment MV is adjusted as A a selectable proportion X%, proportionally to the instantaneously calculated tractive force of the rear axle, the rear axle moment MHAO with account additionally being taken of factors K which are constant and inherent in the drive system, being represented as the instantaneously formed product of the factors, on the one hand of the function M AE f(N AE), as a quotient of converter output moment MA to converter input moment ME, ( C) and on the other hand of the converter input moment ME, represented firstly from the likewise electronically stored function value, which can be called up, from the family of characteristics of the transducer input moment at a particular, constant revolution rate ME at N = const =-f(NAE) and secondly multiplied by the square of the quotient of the real input revolution rate NE and of the selected constant revolution rate Nconst' so that:

ME = ME at N = const X ( N NE 2 const and combined produces for the rear axle moment:

MHA = ME at N = const X N NE)2 X MAE const and the front axle moment is calculated to MVA = MHA x X% and, with the interposition of a hydraulic proportional valve, the front axle moment is controlled in a manner which is known per se by means of the hydraulic operating circuit.

The advantage of the invention lies in that fact that it is possible, using a control device of simple construction, to set the supplementary driving front axle moment, and to ensure not only synchronous running, but in addition an optimum distribution of the operating forces between the front and rear axles in accordance with the axle loads.

I 1 r ' The front axle moment may be selectably predetermined, at the rear axle moment M,,,, in the ratio of the front axle load to the rear axle load.

The front axle moment, proportionally derived from the calculated rear axle moment, may be converted into an electrical signal for the control pressure nominal value of the front wheel motors and fed to the proportional valve.

The type of motion switched in, forward or reverse motion, may be superimposed on the electrical signal for the control of the proportional valve.

The converter output revolution rate may be represented as the product of the rear axle revolution rate and the gear number.

The invention further provides a vehicle having main drive wheels driven by a combustion engine through a torque converter and a gearbox, and supplementarily driven wheels driven by hydraulic motors through a closed hydraulic operating circuit including a control pump and an adjustable pump driven directly by the combustion engine, the supplementary hydraulic drive being controlled by a method as described above.

The invention yet-further provides a method for the supplementary hydraulic drive of wheels on a vehicle, in addition to the main drive wheels driven by an engine through a torque converter and a gearbox, with front wheel motors fed by automated control of a closed hydraulic operating circuit by an adjustable pump, the ( C31.

adjustable pump and a control pump being driven directly by the engine, wherein superimposed on the operating fluid flow control the operating fluid pressure is regulated according to the form of functions which are electronically stored in and can be called up from a function former in response to the ratio N AE of the converter output revolution rate NA or transmission output revolution rate N GA to the converter input revolution rate NE characterised in that the front axle moment M VA is adjusted in accordance with the instantaneously calculated tractive force of the rear axle, during the course of which calculation the ratio N AE is fed to an electronic store containing the characteristics of the function is M E at N = const = f(NAE) and a value M E at N = const of the converter input moment ME at a selected constant revolution rate Nconst is called up, the called up value M E at N = const is multiplied by the square of the ratio of the real input 20 revolution NE to the selected constant revolution rate N const' to produce a value for the converter input moment:

ME = ME at N = const X N NE 2 ( const the ratio NAE is fed to an electronic store containing the characteristics of the function MAE = f(N AE) and a value MAE Of the ratio of the converter output moment MA to the converter input moment ME is called up, the ( C11 called-up value MAE is combined with the value ME for the converter input moment, with account also being taken of factors K n which are constant and inherent in the drive system, to product a value M HA for the rear axle moment, where:

MHA = ME at N = const x N NE) 2 X ( const MAE X K,... n the front axle moment MVA is calculated as a selected proportion X% of the rear axle moment MHA, such that: MVA = MHA x X9-, and the front axle moment is controlled through the hydraulic operating circuit by means of a hydraulic proportional valve.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing, which is a diagrammatic representation of the drive arrangement of a vehicle.

In the Figure, an operating circuit corresponding to the arrangement in German Patent 33 31 651 is taken as the starting point. The engine (1), preferably a combustion engine, but which may be some other type of engine such as an electric motor, drives the main drive wheels (4) of a vehicle through a torque converter (2) including its converter stages and a gearbox (3). At the same time, an adjustable pump (5) and a control pump (6) are driven directly by the engine (1) through a shaft. The two units, mentioned above, of an automated control system operate in a closed hydraulic operating circuit (: C - a which feeds the wheel motors (7, 8) and thus sets the supplementarily driven wheels (9, 10) in rotation. Hydraulically actuated clutches (11, 12) are provided between the wheels (9, 10) and the motors (7, 8). The wheel motors (7, 8) are protected by two pressure limiting valves (13, 14).

The control angle of the adjustable pump (5) is set by means of an increasing element (15) and a decreasing element (16), according to how they are fed by a propor- tional valve (17). An overpressure valve (21) limits the control pressure to an adjustable fixed value in the control circuit. The operating circuit is topped-up with fluid from the fluid flow of the control pump (6) through one-way valves (22, 23).

To the known arrangement so far described, there are now provided in the measuring points (28, 29) of the torque converter, actual-value sensors which emit signals representing the converter input revolution rate NE and the converter output revolution rate NA. In a ratio former (25), the ratio NAE of the converter output- to input revolution rate is formed. This value is fed as an abscissa, to a store (26), and, from the family of characteristics representing the function of the ratio of converter output moment MA to converter input moment ME stored therein, an ordinate value M AE is called up and processed further.

The converter input moment ME is determined in a manner which is known per se by means of a curve, t y ( 0 registered in a function store (27), representing the measured converter input moment ME at a constant converter input revolution rate N E const to the ratio of the converter output to input revolution rate N AE. The value delivered in each case by the function store (27) is multiplied in a multiplier (24) by the square of the ratio of the converter input revolution rate NE to the above-mentioned constant converter input revolution rate N const' and fed to a main multiplier (20). The product formed therein with the above-mentioned value MAE called up from the store (26), taking into consideration also factors K 1 n inherent in the drive system which are constant or at least interval-constant, and represent the gear which is engaged, the rear axle transmission ratio and the efficiency of the rear drive, represents a computer-produced measurement for the rear axle moment m HA This value is fed to a divider (19), from which there is obtained, as a selectable proportion X% of the rear axle moment MHA, a rating value for the front axle moment MVA- During normal, continuous operation, this proportion of the front axle moment MVA, relative to the rear axle moment MHA will correspond to the ratio of the respective axle loads,- that is to say, approximately 1/3 to 1. However, under special conditions, for example on slopes or when ice forms, the proportion of the front axle moment MVA may be adjusted by the driver of the vehicle.

The rating value for the front axle moment MVA is C.1 converted in a transformer (18), in accordance with the characteristics of the proportional valve (17), which are known pgr ge, into electrical actuating signals i reverse or i forward to set the magnetic valve inputs (32, 33).

The proportional valve (17) is connected hydrauli cally in a known manner by way of the lines (34,35) to the operating circuit and by way of the connections (36, 37) to the increasing element (15) and the decreasing element (16). The proportional valve (17) is fed by the control pump (6) through an infeed (38).

An alternative method for representing the output revolution rate NA consists in multiplying the rear wheel revolution rate N GA by a gear parameter i gear in a factor former (40) to provide the transmission output revolution rate N GA, and then introducing it into the computing operation, as indicated by the broken lines in the drawing. The gear parameter i gear also delivers alternative signals (30 and 31) through an Or-section (39) to the transformer (18), depending on whether the rear axle is in forward or reverse operation.

The control arrangement described above has a low cost and advantageously represents a method for the supplementary drive of wheels on a vehicle which can be carried out sensitively and is adjustable with regard to the distribution of the operating forces.

t ( - 11

Claims

Claims:

1. Method for the supplementary hydraulic drive of wheels on a vehicle, in addition to the main drive wheels driven by an engine through a torque converter and a gearbox, with front wheel motors fed by automated control of a closed hydraulic operating circuit by an adjustable pump, the adjustable pump and a control pump being driven directly by the engine, wherein superimposed on the operating fluid flow control the operating fluid pressure is regulated according to the form of functions which are electronically stored in and can be called up from a function former in response to the ratio N AE of the converter output revolution rate NA or transmission output revolution rate N GA to the converter input revolution rate NE characterised in that the front axle moment MVA is adjusted in accordance with the instan taneously calculated tractive force of the rear axle, during the course of which calculation the ratio N AE is fed to an electronic store containing the characteristics of the function m E at N = const = f(N AE) and a value M of the converter input moment E at N = const ME at a selected constant revolution rate N const is called up, the called up value ME at N = const is multiplied by the square of the ratio of the real input revolution NE to the selected constant revolution rate (.. C-1, - 12 - N const' to produce a value for the converter input moment:

NE 2 ME ME at N = const X ( N const _ the ratio 'AE is fed to an electronic store containing the characteristics of the function M AE = f(NAE) and a value MAE of the ratio of the converter output moment MA to the converter input moment ME is called up, the called-up value "AE is combined with the value ME for the converter input moment, with account also being taken of factors K which are constant and inherent in the drive system, to product a value M HA for the rear axle moment, where:

MHA = M E at N = const N NE 2 X M AE! const) the front axle moment MVA is calculated as a selected proportion X% of the rear axle moment MHA, such that:

MVA = MHA X X-' and the front axle moment is controlled through the hydraulic operating circuit by means of a hydraulic proportional valve.

2.

Method according to claim 1, characterised in that the front axle moment MVA is adjusted as a proportion of the rear axle moment MHA, the proportion being selected in accordance with the ratio of the front axle load to the rear axle load.

3.

Method according to claim 1 or claim 2, characterised in that the front axle moment, 4 proportionally derived from the calculated rear axle moment is converted into an electrical signal representing a desired value for the control pressure of the front wheel motors, and is fed to the proportional valve.

4. Method according to claim 3, characterised in that a signal representing the type of motion selected, being forward and reverse motion, is superimposed on the electrical signal for the control of the proportional valve.

5. Method according to any one of claims 1 to 4, characterised in that the converter output revolution rate is determined from the product of the rear axle revolution rate and the selected gear ratio.

6. A method for the supplementary hydraulic device of wheels on a vehicle, the method being substantially as described herein with reference to, and as illustrated by, the accompanying drawing.

7. A vehicle having main drive wheels driven by an engine through a torque converter and a gearbox, and supplementarily driven wheels driven by hydraulic motors through a closed hydraulic operating circuit including a control pump and an adjustable pump driven directly by the engine, the supplementary hydraulic drive being arranged to be controlled by a method in accordance with any one of the preceding claims.

8. A vehicle substantially as described herein with reference to, and as illustrated by, the accompanying drawings.

Published 1990 at The Patent Office. State House. 6671 High Holborn. LondonWC1R4TP. Further copies maybe obtained from The Patent Office. Sales Branch. St Mary Cray. orping.c..-...Kent BR5 3Rr Printed by Multiplex techniques ltd. St Wary Crajy Kent. Con 1'87