GB2157856A

GB2157856A - Control unit for automotive vehicles

Info

Publication number: GB2157856A
Application number: GB08507758A
Authority: GB
Inventors: Manfred Kahrs
Original assignee: Alfred Teves GmbH
Current assignee: Continental Teves AG and Co oHG
Priority date: 1984-04-09
Filing date: 1985-03-26
Publication date: 1985-10-30
Also published as: GB8507758D0; FR2562379A1; DE3413435A1; IT1184397B; IT8520260A0

Abstract

A control unit for an automotive vehicle, in particular for a tractor (1) used in agriculture, whereby, in use, the drawing resistance of a cultivating device (9) coupled to the tractor (1) is variable, the cultivating device (9) being influencable such as to bring about a roughly constant traction. Measuring devices (4, 5) for ascertaining the wheel speeds are arranged in use at the vehicle axles (2, 3) and, when a predefinable wheel speed difference is exceeded, the cultivating device (9) can be influenced with a view to reducing the drawing resistance. Thus the tractor (1) can be permanently operated in a relatively favourable slip range, whereby a considerably improved efficiency and, respectively, a more favourable energy consumption will be accomplished. Furthermore, there will be attained higher working speed and hence, per time unit, a greater unit of area when ploughing. <IMAGE>

Description

SPECIFICATION Control unit for automotive vehicles The present invention relates to a control unit for an automotive vehicle, in particular for a tractor used in agriculture, whereby, in use, the drawing resistance of a cultivating device coupled to the vehicle is variable, the cultivating device being influencable such as to bring about a roughly constant traction.

A unit featuring the above characteristics is known from Bosch publication "Control Hydraulics Equipment for Tractors", edition March 1, 1962. In the control unit known from this publication, the respective resistance the cultivating device exerts is measured by a tension spring, the spring travel of said tension spring serving in each case to activate a hydraulic unit which enables reduction of the drawing resistance of the cultivating device.

This known control unit is suitable in particular for the operation of agricultural tractors for ploughing, which is the hardest traction work entailing great time consumption.

It is generally aimed at in respect of such agricultural operations to control the traction in order to make optimum use of the installed engine power of the tractor, on the one hand, and to prevent the driving wheel slip from becoming too great, on the other hand. In the known unit called a lift regulator-the cultivating device (for instance a plough) is attached to the tractor via a rod system and is held by hydraulic cylinders, via corresponding deviation devices, in a depth position which is variable. Disposed at the tension spring arranged between the tractor and the plough is a force-measuring element supplying corresponding control signals to a hydraulic control unit.Owing to the output signals of the hydraulic control unit, a hydraulic cylinder can be acted upon by pressure oil so that the traction of the tractor is permitted to be kept constant approximately as a function of the changed depth of immersion of the plough.

It has to be considered a particular disadvantage in this known control unit that often there is soil cultivation during which the driving axle of the tractor has relatively high slip values, from which poor efficiency of cultivation as well as unfavourable energy consumption result as a whole.

It is therefore an object of the present invention to improve upon a control unit of the kind initially referred to such as to accomplish an optimum traction in wide ranges, the slip being correspondingly low.

According to the present invention there is provided a control unit for an automotive vehicle, in particular for a tractor used in agriculture, whereby, in use, the drawing resistance of a cultivating device coupled to the vehicle is variable, the cultivating device being influencable such as to bring about a roughly constant traction, characterised in that the control unit includes measuring devices for ascertaining wheel speeds which, in use, are arranged at axles of the vehicle the cultivating device being influencable with a view to reducing the drawing resistance when a predeterminable wheel speed difference is exceeded.

Such a control unit permits to attain in a favourable manner that slip can be kept comparatively low while optimum traction prevails. This has a direct consequence that there is higher efficiency compared to known units and that favourable energy consumption is obtained, on the other hand. In comparison with an operation with higher slip values, furthermore, there results the advantage that the working speed of the tractor will be increased so that a greater unit of area per time unit is attainable.

According to one embodiment, the rotational speed signals are supplied to a monitoring electronics, the said monitoring electronics permitting to activate a hydraulic adjusting device. However, advantageously, said hydraulic adjusting device will not be activated until a specific rotational speed difference has been exceeded. It is furthermore arranged for in an expedient fashion that the hydraulic adjusting device assumes a stationary condition between two rotational speed differences.

This has an immediate result that the control unit operates relatively smoothly and that there is obtained constant ploughing depth in wide ranges. Besides, there is provision that the differential values can be selected and adjusted by the operator, the said operator being able to derive them from practical values in respect of field areas ploughed already.

For the exact measurement of the numbers of revolutions of the wheels, each vehicle wheel can be equipped with a rotational speed sensor. It is likewise possible that in the case of a tractor whose driven axle has a locking differential, that the rotational speed of the driven axle can be sensed by one single sensor. Simplification of the unit is effected owing to such an embodiment.

An embodiment of the present invention will now be described in more detail hereinbelow with reference to the view of a tractor illustrated in the accompanying drawing.

In the drawing, reference numeral 1 designates a tractor having a non-driven front axle 2 and a driven rear axle 3. Sensors 4 and 5 serving to measure the rotational speeds of the axles 2 and 3 are arranged at both the front axle 2 and the rear axle 3. The output signals of the sensors 4 and 5 are supplied via corresponding electrical lines to an electronic monitoring circuit 6 which evaluates the output signals of the sensors, which determines the difference between the numbers of revolutions of the vehicle axles 2 and 3 and which, when a predetermined difference is exceeded, will actuate an electrohydraulic control unit 7 serving to actuate a hydraulic cylinder 8.

Arranged at the tractor 1 is a plough 9 coupled to the tractor via a lever system 10.

The working depth of the plough 9, in turn, is dependent on the position of the hydraulic cylinder 8.

The mode of function of the control unit described will be explained hereinbelow.

During operation of the tractor 1, normally a constant working depth of the plough 9 is adjusted via the level system 10, the normal mode of operation referring to a condition in which the advance movement of the plough and, respectively, of the tractor 1 is not influenced considerably by outward circumstances. The numbers of revolutions of the axles 2 and 3 are permanently measured by the sensors 4 and 5 and supplied to the monitoring circuit 6. When the monitoring circuit 6 recognises that the difference of the numbers of revolutions of the axles 2 and 3 has exceeded a pre-adjustable threshold value, a corresponding control signal will be issued to the electrohydralic control unit 7. In response thereto, the hydraulic cylinder 8 will be furnished with pressure oil from an auxiliary pressure source 11 so that a lever 1 2 connected to the hydraulic cylinder 8 will move to the right, when viewing the drawing, and, via a deviation device 1 3 and the lever system 10, will act on the plough 9 such as to cause reduction of the working depth, that is reduce the drawing resistance. Ensuing therefrom is likewise that the predefined nominal slip value will occur at the driven rear axle 3 of the tractor 1.

The monitoring circuit 6 may involve both analog and digital processing of the signals it is supplied with. It is likewise possible alterntively that the electrohydraulic control unit 7 involves alalog or pulsating operation.

Claims

1. A control unit for an automotive vehicle, in particular for a tractor used in agriculture, whereby, in use, the drawing resistance of a cultivating device coupled to the vehicle is variable, the cultivating device being influencable such as to bring about a roughly constant traction, characterised in that the control unit includes measuring devices (4, 5) for ascertaining wheel speeds which, in use, are arranged at axles (2, 3) of the vehicle the cultivating device (9) being influencable with a view to reducing the drawing resistance when a predeterminable wheel speed difference is exceeded.

2. A control unit as claimed in claim 1, characterised in that the rotational speed signals are delivered to a monitoring electronics (6), and in that an hydraulic adjusting device (7) can be activated by said monitoring electronics (6).

3. A control unit as claimed in claim 1 or claim 2, characterised in that the rotational speed difference required for issuing a control signal is adjustable.

4. A control unit as claimed in claim 2 or claim 3, as appendant to claim 2, characterised in that the hydraulic adjusting device (7) assumes a stationary condition between two rotational speed differences.

5. A control unit as claimed in claim 4, characterised in that the difference values can be selected and adjusted by the vehicle's operator.

6. A control unit as claimed in any one of the preceding claims, characterised in that a rotational speed sensor (4, 5) is, in use, arranged at each vehicle wheel.

7. A control unit as claimed in claim 6 and for use with a tractor having a driven axle (3) with a locking differential, characterised in that the number of revolutions of the driven axle (3) can be sensed by one single rotational speed sensor (5).

8. A control unit for an automotive vehicle substantially as herein described with reference to the accompanying drawing.