WO2000074968A1

WO2000074968A1 - Method and apparatus for controlling a diesel engine during gear change

Info

Publication number: WO2000074968A1
Application number: PCT/SE2000/001112
Authority: WO
Inventors: Anders Eskilson
Original assignee: Scania Cv Aktiebolag (Publ)
Priority date: 1999-06-04
Filing date: 2000-05-30
Publication date: 2000-12-14
Also published as: SE9902062D0; SE512728C2; DE10084647T1; SE9902062L

Abstract

A method and an arrangement for controlling the speed of an engine (10) of a heavy vehicle during gear changing in a mechanical gearbox (12, 13, 14) in cases where a manually operable clutch (11) is incorporated in the driveline between the engine and the gearbox are distinguished by the fact: that running parameter data of the vehicle are observed and recorded, that breaking of the driveline upon disengagement of the clutch (11) is detected and a first signal indicative thereof is generated, that a gear signal indicating the intended gear position is generated, that a desired engine speed intended to prevail upon completion of the gear change is determined, in response to the first signal, on the basis of said running parameter data and the gear signal, and that a control signal is generated which acts upon the engine control system so that the engine speed is adjusted towards said desired speed.

Description

METHOD AND APPARATUS FOR CONTROLLING A DIESEL ENGINE DURING GEAR CHANGE

TECHNICAL FIELD The present invention relates to a method and an arrangement in accordance respectively with the preambles to patent claims 1 and 6.

STATE OF THE ART

When operating a heavy vehicle which is driven by diesel engine and is of the kind which has a mechanical gearbox and a mechanical clutch, e.g. of the disc type, gear changes at high gas mobilisation are particularly problematical, since depressing the clutch pedal in order to change gear or gears in the gearbox unit causes the engine speed to rise quickly if the accelerator pedal is held down, which is difficult to avoid, particularly during gear changing on uphill runs or, in general, when the vehicle is heavily laden. In such situations, racing of the engine at the time of clutch disengagement may quickly cause a considerable increase in the speed of the clutch half connected to the engine, resulting in substantial clutch wear. A similar situation occurs when the clutch has to be re-engaged on completion of gear changing, since here again clutch wear is caused by differences in speed between the clutch halves and, of course, between the rotating masses whose speed has to be adapted at the time of the re-engagement. The engine speed adaptation is achieved by means of the sliding clutch in combination with the gearbox, the final gear and the driving wheels. The situation is particularly difficult for untrained drivers, since gas mobilisation compensation with a reasonable result is difficult to achieve and calls for long experience of driving heavy vehicles in general and the specific vehicle in particular.

Thus a disadvantage of the state of the art is the fact that the sometimes large speed differences and masses that require speed adaptation cause considerable clutch wear and that this even occurs in "normal" gear changing during "normal" driving. There is also loading of other parts of the driveline and on the tyres, and oscillations are induced in the driveline, resulting in discomfort due to disturbing noise and physical shaking of the vehicle, which is a particular problem if the heavy vehicle is a bus for passenger traffic. Excessive clutch wear also means extra expenditure on clutch replacement and considerable extra costs due to vehicle immobilisation.

OBJECTS OF THE INVENTION One object of the present invention is to eliminate or alleviate the problems of the state of the art. This object is achieved with a method and an arrangement of the kind mentioned in the introduction by means of the features indicated respectively in the characterising parts of patent claims 1 and 6.

The result is the achievement by simple means of elimination of the undesirable difference in speed between the clutch halves at the time of their disengagement and re- engagement, while at the same time the loading on and wear of the clutch can be substantially reduced, as also the corresponding loading of other components of the driveline. Further advantages which may be mentioned include simplified driving of a vehicle equipped in accordance with the invention, and greater comfort, which is particularly perceptible in buses carrying passengers but may also be significant for other types of heavy vehicles.

Regarding the indication of clutch disengagement, it may be mentioned that sensors for providing such signals are already known but are conventionally designed, for example, to communicate with a vehicle speed maintainer and/or to make gear changes possible in a split gearbox, where the case arises. Such conventional sensors may nevertheless be used with the invention.

The invention is applicable to both purely mechanical gearboxes with mechanical linkages and to servo-assisted gearboxes. The gearboxes concerned include a main gearbox and also, where applicable, a split and/or range gearbox or the like.

Engine speed control systems are known per se and will not be described here.

Advanced control systems which have recently been developed adapt the engine speed to the input speed to a gearbox unit and consist of a number of sensors situated at various points in the driveline. Such systems are employed, however, in such a way that the clutch is not used during normal driving and that the speed adaptation is designed to be so accurate that gear changing can be initiated directly without operating the clutch. With the system according to the present invention, however, engine speed adaptation or maintenance is initiated by the driver's operating an entirely manual or a servo-assisted clutch, but with the clutch otherwise being used in a conventional manner. The gain by using the present invention is thus that the speed difference which occurs in conventional systems is avoided, and hence also the associated problems.

The running data which it may be relevant to observe and record include the vehicle speed, the engine speed, the speed of the gearbox output shaft, the gas mobilisation (the accelerator pedal position) and the current gear position. Depending on the application, the system may be designed to observe some or possibly all of these running parameters in order to generate relevant signals for use by the engine control system when the driver disengages the clutch. The gear position which the driver intends to change to is also detected. This may be achieved in different ways in different applications and may apply to gear changes in all the constituent portions of the gearbox, e.g. split, main and range gearboxes, or in one or two of them. The invention is thus, for example, easy to apply in a two-part gearbox incorporating split and main gearboxes when changing gear in only the split gearbox by means of an ordinary control device arranged in the form of a movable collar on the gear lever. In such cases, shifting the collar in a particular direction results in an unambiguous signal indicating the driver's intention to change gear in the split gearbox.

Regarding gear changes in a main gearbox with joystick control (e.g. Scania' s Comfort Shift), systems already exist for predicting which gear the driver intends to change to. In such cases the lever is locked by a solenoid lock until sensors in the gearbox acknowledge that the gear has been changed. Such a system is easy to extend to working according to the invention, since the signals relevant for the invention are readily available and can be used for engine control. It is also relatively easy to provide other types of gearbox controls with equipment for enabling the system to receive an indication of which gear the driver intends to engage. Examples include sensors on the gear lever, in the linkage or even in the gearbox itself. Further advantages are achieved by the features in the various patent claims and will be described below.

DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail against the background of embodiments and with reference to the attached drawings, in which: Fig. 1 depicts schematically a flow diagram of a method according to the invention, and Fig. 2 depicts schematically the control system, including a system according to the invention, in a driveline for a heavy vehicle.

DESCRIPTION OF EMBODIMENTS

Thus Fig. 1 depicts a flow diagram of a method according to the invention, in which reference 1 denotes the start of the sequence. Reference 2 indicates observation of running parameters such as vehicle speed, engine speed, gearbox output shaft speed, gas mobilisation (accelerator pedal position) and current gear position, and reference 3 denotes detection of breaking of the driveline, e.g. in the form of disengagement of a disc clutch and the generating and delivery of a first signal indicative thereof. Reference 4 denotes indication of the driver's intended gear position for the relevant portion or portions of the vehicle's gearbox, and reference 5 denotes calculation of a desired engine speed for the intended gear position on the basis of relevant observed running parameters from which, in combination with stored input and output speed data for each gear combination, an equivalent speed can easily be calculated for each gear combination and each output shaft speed. A control signal which describes said desired engine speed and is delivered to a system for controlling the engine is also generated and emitted. Reference 6 denotes the action of the engine control system on the engine to achieve the desired engine speed, such as gas mobilisation modification to achieve the desired speed. Reference 7 denotes detection of driveline reconnection, and reference 8 the end of the sequence.

Fig. 2 depicts schematically the control system 9, which with advantage includes also a system according to the invention incorporated in or connected to the normal engine control system. Reference 16 denotes a memory for recording the running parameters and speed situations for different gears etc. which are relevant in connection with the present invention. In the driveline, reference 10 denotes the engine, reference 11 the clutch operable by the driver manually via a clutch pedal, and references 12, 13 and 14 the gearbox, comprising in this example three portions, namely split, main and range gearboxes, and reference 15 denotes a speed sensor for the output speed. Reference 17 denotes the final gear. The gearbox is thus a mechanical gearbox with a number of specified steps (gear ratios) which the driver can choose by means of a gear selector, e.g. in the form of a gear lever which directly or via servo devices changes the position of the gears in the gearbox. This diagram shows the control system communicating with the engine, with the clutch, with the output shaft sensor 15 and with the memory 16. It may also communicate with the gearbox, as indicated by discontinuous lines.

All in all, the invention results in substantially easier driving, which means that a vehicle equipped according to the invention can be driven even by an untrained driver so that in practice very advanced driving can be achieved in a very simple manner. Significant cost reduction due to less maintenance may be expected. An important advantage of the invention is that the system is inexpensive and can be applied to vehicles which are selected by the haulier in order to be as inexpensive as possible for minimised running costs and which are not equipped with sophisticated but expensive automatic gear systems. Another advantage is that the driver need not hesitate to engage a more optimum gear, since gear changing becomes significantly less problematical, so a certain amount of improvement in vehicle running economics is to be expected. Gearchange times may also be shortened.

As this system allows gear changing at full gas mobilisation, driving with the system connected may be said to represent a "high-performance driving mode" whereby more efficient driving with large loads can be achieved. For example, the system may possibly be connected as such a high-performance driving mode when the driver depresses the clutch pedal and at the same time the gas mobilisation is at least about 70%.

The system also causes reduced noise, as high-performance driving results in a lower no- load speed during gear changing. The invention may be varied within the scope of the claims and, as indicated above, it may also be applied, for example, to merely one out of a number of constituent portions of the gearbox.

Claims

PATENT CLAIMS

1. Method for controlling the speed of an engine (10) of a heavy vehicle during gear changing in a mechanical gearbox (12,13,14) in cases where a manually operable clutch (11) is incorporated in the driveline between the engine and the gearbox, characterised

-in that running parameter data of the vehicle are observed and recorded,

-that breaking of the driveline upon disengagement of the clutch (11) is detected and a first signal indicative thereof is generated, -that a gear signal is generated from the gearbox or its control devices, indicating which gear the driver intends to engage,

-that a desired engine speed intended to prevail upon completion of the gear change is determined, in response to the first signal, on the basis of said running parameter data and the gear signal, and -that a control signal is generated which acts upon the engine control system so that the engine speed is adjusted towards said desired speed.

2. Method in accordance with claim 1, characterised in that said running parameter data are taken from the group consisting of vehicle speed, engine speed, gearbox output shaft speed, gas mobilisation and current gear position(s) in the gearbox.

3. Method in accordance with claim 1 or 2, characterised in that the gear change is downwards and that the engine speed is increased in a controlled manner.

4. Method in accordance with claim 1 or 2, characterised in that the gear change is upwards and that the engine speed is reduced in a controlled manner.

5. Method in accordance with claim 1 or 2, characterised in that the system is connected when the driver disengages the clutch, provided that the gas mobilisation is at least about 70%.

6. Method for controlling the speed of an engine (10) of a heavy vehicle during gear changing in a mechanical gearbox (12,13,14) in cases where a manually operable clutch (11) is incorporated in the driveline between the engine and the gearbox, characterised -by a control system (9) which is designed to observe and record running parameter data of the vehicle,

-by devices for detecting breaking of the driveline upon disengagement of the clutch and for generating a first signal indicative thereof,

-by devices for detecting the new gear position intended by the driver and for generating a gear signal indicating that position,

-in that the control system (9), in response to said first signal, is arranged to determine a desired engine speed intended to prevail upon completion of the gear change, on the basis of said running parameter data and the gear signal, and

-in that the control system (9) is arranged to generate a control signal which is designed to act upon the engine control system so that the engine speed is adjusted towards said desired speed.

7. Method in accordance with claim 6, characterised in that said running parameter data are taken from the group consisting of vehicle speed, engine speed, gearbox output shaft speed, gas mobilisation and current gear position(s) in the gearbox.

8. Method in accordance with claim 6 or 7, characterised in that the gear change is downwards and that the engine speed is increased in a controlled manner.

9. Method in accordance with claim 6 or 7, characterised in that the gear change is upwards and that the engine speed is reduced in a controlled manner.

10. Method in accordance with claim 6 or 7, characterised by devices for connecting the system when the driver disengages the clutch, provided that the gas mobilisation is at least about 70%.