SE522900C2 - Arrangement and method for detecting a zero torque in a gearbox - Google Patents

Abstract

The present invention relates to an arrangement and a method for detecting a zero torque in a stepped gearbox. The arrangement comprises a first sensor (15) arranged to sense a first parameter related to the number of revolutions of the input shaft (4) of the gear box, a second sensor (16) arranged to sense a second parameter related to the number of revolutions of the output shaft (6) of the gear box and a control unit (11) arranged to receive measurement values concerning said first and second parameter. The control unit (11) is thereafter arranged to compare if the number of revolutions of the input shaft (4) of the gear box and of the output shaft (6) of the gear box correspond with regard to the gear ratio of the engaged gear in the gear box (5) and for detecting a zero torque in the gear box (5) if a different occurs.

Description

522 900 'SE 504 717 shows a further development of the above-mentioned procedure. In addition to a calculation of the engine torque required for a zero torque to be obtained in the gearbox, a measurement is also made here in connection with each gear shift to evaluate whether the calculated and equipped engine torque in connection with a gear shift was a correct zero torque. If this was not the case, a correction is made at a subsequent shift of the calculated zero torque with a value corresponding to the error at the previous laying of the gear.

SE 507 436 discloses a further method for allowing correction of a calculated and equipped motor torque. Here, the speed of the gearbox's output shaft is measured. If the shaft shows a change in speed immediately after a gear has been disengaged, it is established that no zero torque prevailed in the gearbox when the gear was disengaged.

In such cases, a correction takes place during a subsequent shifting of a calculated engine torque with a value that is related to the amplitude of the gearbox output shaft change in speed.

SE 507 869 discloses a method for controlling engine torque when shifting a vehicle. Here, the torsional rotation of the vehicle's drive shafts is measured as a measure of the current torque in the gearbox.

A current value of the torsional rotation is determined by signal processing of measurement signals regarding the current engine speed and drive wheel speed. The torque of the motor is adjusted here until the torsional rotation is zero, after which a shifting of the engaged gear is performed.

The methods known above are functional but require advanced calculations which include a number of input parameters in order to be able to determine the engine torque corresponding to a zero torque in the gearbox. In addition, it is complicated to supply fuel in such an amount so that an engine receives exactly a calculated engine torque, when e.g. the quality of the fuel may vary. In addition, the known methods are relatively time consuming and it would be desirable to be able to reduce the time it takes for the engine torque to control the engine torque and detect a zero torque in the gearbox so that the engaged gear can be disengaged.

SUMMARY OF THE INVENTION The object of the present invention is to provide a method and an arrangement for detecting a zero torque in a gearbox in a simple and reliable manner. Another object is to provide a detection of a zero torque which allows a fast and uncomplicated control of a motor torque towards a zero torque in the gearbox.

The first stated object is achieved with the initially mentioned arrangement and method which is characterized by what is stated in the characterizing parts of claims 1 and 8. In gear engagement between teeth in a gearbox, there is always a certain gap.

Such a gap means that when a motor supplies a positive torque, the teeth in a gear engagement are in a first rotational position in relation to each other and when the motor supplies a negative torque, the teeth in a gear engagement are in a second rotational position relative to each other. In connection with a transition from a positive torque to a negative torque in the gearbox, the teeth in the gear engagement are rotated between said first and second rotational positions.

This gap usually appears over a short period of time of 0.05 to 0.10 seconds. By comparing the control unit with a frequency of at least 50 Hz, but preferably a higher frequency, the speed of the input and output shafts of the gearbox, said gap in the gearbox can be detected as a speed deviation between said shafts when said rotation takes place. The parameters read are advantageously the speeds of the input shaft in the gearbox and the output shaft in the gearbox. But other parameters that are in relation to these parameters can also be measured. For example, the engine speed can be measured instead of the speed of the input shaft in the gearbox if the engine and the input shaft in the gearbox are firmly connected. 5 15 20 25 30 35 522 '900 According to a preferred embodiment of the present invention, the control unit is arranged to detect a zero torque in the gearbox when such a deviation reaches a certain value. Since disturbances of various kinds can lead to smaller fluctuations of measured parameter values, such a deviation should at least reach a minimum value before it can be detected with certainty that a zero torque prevails in the gearbox. Advantageously, said value of the deviation varies for different gears. Since the gap in the gear lever for low gears is larger than for high gears, it is suitable to let said value be larger for low gears than for high gears.

According to another preferred embodiment of the invention, the control unit is arranged to calculate a function which comprises a relationship between the first parameter and the second parameter. The relationship between the mentioned parameters shows a constant relationship when a positive or a negative moment prevails in the gearbox. Such a function advantageously also contains a correction factor which includes the gear ratio engaged in the gearbox in the gearbox. With a suitable such correction factor, the value of the function becomes at least in theory exactly equal to 1.00 when a positive or a negative moment prevails in the gearbox. If the engine is regulated so that a transition from a positive torque to a negative torque is obtained in the gearbox, the input shaft of the gearbox will, due to said gap, during a transition stage obtain a lower speed in relation to the output shaft.

The said function thus receives a value that is a couple of percent lower than 1.00. Correspondingly, if the engine is regulated so that a transition from a negative torque to a positive torque in the gearbox is obtained, the input shaft of the gearbox will during a transition stage receive a higher speed in relation to the output shaft. Said function thus receives a value which is a few percent higher than 1.00. By calculating the value of such a function, it can be determined in a relatively uncomplicated way when a transition takes place in the gearbox between a positive and a negative element. During said transition, there is thus a zero torque in the gearbox. According to another preferred embodiment of the invention, when a shift is desired to be performed, the control unit is arranged to regulate the output torque of the motor so that it is adjusted in such a direction so that zero torque is allowed to be indicated in the gearbox. For example, the fuel supply to the engine is controlled to adjust the engine's output torque. If there is a positive torque in the gearbox, the fuel supply to the engine is reduced until a negative torque is obtained so that a zero torque can be detected during the transition phase. If there is a negative torque in the gearbox instead, the fuel supply to the engine is increased until a positive torque is obtained so that a zero torque can be detected during the transition phase. Here it is not necessary to calculate exactly how much fuel is to be supplied to the engine, but the amount of fuel can be increased or decreased in a substantially arbitrary but functional manner. A zero torque can thus be obtained and detected relatively quickly.

According to another preferred embodiment of the invention, when a shift is desired to be performed, the control unit is arranged to activate a shift mechanism which shuts off the engaged gear when a zero torque is detected in the gearbox. As soon as a deviation is detected regarding the speed of the gearbox's input and output shafts, the engaged gear is disengaged. As the torque-free state of the gearbox usually only lasts for a time period of 0.05 to 0.10 seconds, a relatively fast activation of the gear mechanism is required.

According to another preferred embodiment of the invention, the output shaft of the gearbox is arranged to deliver a torque to a driveline in a vehicle. The arrangement and procedure described above are advantageously used in a vehicle. Parameters that are related to the gearbox's output shaft speed can in principle be measured anywhere on the driveline. BRIEF DESCRIPTION OF THE DRAWINGS In the following, a preferred embodiment of the invention is described by way of example with reference to the accompanying drawing, in which: Fig. 1 schematically shows an arrangement according to the present invention and Fig. 2 shows in curve shape a zero torque detecting function value with time during operation of a vehicle.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION Fig. 1 shows schematically selected parts of a vehicle. The vehicle is driven by a motor 1. The motor 1 drives, via an output shaft 2 and a clutch 3, an input shaft 4 of a step gearbox 5. The step gearbox 5 comprises a plurality of gears with varying gears. Extending from the gearbox 5 is an output shaft 6 which engages a driveline of the vehicle. The drive line comprises a cardan shaft 7, an end gear 8 and drive shafts 9 which are connected to the drive wheels 10 of the vehicle. In this exemplary embodiment, the clutch 3 is intended to be operated substantially only at start and stop of the vehicle. When shifting between different gears in the gearbox 5 while driving, the clutch 3 is not intended to be operated. The shifting thus takes place with the clutch 3 in engagement as a propulsion-transmitting rigid connection between the output shaft 2 of the engine 1 and the input shaft 4 of the gearbox.

The vehicle's shifting system comprises an electric control unit 11 which is arranged to receive information from a driver by means of a shift lever 12 when a shift is desired to be performed. The control unit 11 thereby activates a fuel injection unit 13 to control the torque of the engine 1 so that a zero torque can be obtained in the gearbox 5. When a zero torque is obtained in the gearbox 5, the control unit 11 activates a shift mechanism 14 which disengages it 10 15 20 25 30 35 522 900 'existing gear. Thereafter, the control unit 11 regulates the amount of fuel injection through the fuel injection unit 13 so that the engine 1 obtains a speed so that the shift mechanism 14 can engage in a new gear.

The arrangement for detecting a zero moment in the gearbox 5 comprises a first sensor 15 which is arranged to sense the speed of the input shaft of the gearbox 4 and a second sensor 16 which is arranged to sense the speed of the output shaft of the gearbox 6.

Alternatively, existing sensors in the vehicle can advantageously be used which, for example, sense the speed of the engine 1 which corresponds to the speed of the input shaft of the gearbox 4 and the speed of the cardan shaft 7 which corresponds to the speed of the output shaft of the gearbox 6. The first 15 and second 16 sensors send a signal related to the measured speeds of the respective shafts 4, 6 to the control unit 11. The control unit 11 calculates at a frequency of, for example, 100 Hz a zero torque detecting function f. The control unit 11 calculates the function f at least when a shift signal has been obtained from the shift lever 12 but can also advantageously calculate the function f substantially continuously. The function f indicates the ratio between the gearbox input shaft 4 speed and the gearbox output shaft 6 speed corrected with the gear ratio of the engaged gear. The value f of the function becomes at least completely theoretical at a completely rigid connection in the gearbox when a positive or a negative moment is transmitted in the gearbox 5.

Fig. 2 shows a curve describing how the value f of the function varies with the time t while driving a vehicle. During a first period of time in the engine, the vehicle is braked and it is thus driven with a negative torque in the gearbox 5. In gear engagement between teeth in a gearbox 5 there is always at least a small play. Such a gap means that when the motor 1 applies a positive torque, the teeth in a gear engagement are located in a first rotational position relative to each other and when the motor 1 applies a negative torque, the teeth in a gear engagement are located in a second rotational position in relation to eachother. During the first time period I when a negative torque is transmitted in the gearbox 5, the teeth are in the second rotational position and the input shaft 4 and output shaft 5 of the gearbox 5 have a completely corresponding speed taking into account the gear engaged in the gearbox. . The function f here is thus substantially constant 1.00. The minor variations of the function f that occur result from vibrational movements between the teeth in engagement and measuring disturbances. At the end of the first time period I, the driver of the vehicle decides to put in a new gear. A control signal is sent from the gear lever 12 to the control unit 11 which activates the fuel injection unit 13. so that the motor 1 receives an increased fuel supply. The torque delivered by the engine 1 to the input shaft 4 of the gearbox increases and a positive torque is obtained in the gearbox 5. In connection with a transition from a negative torque to a positive torque, the teeth in the gear lever are rotated from the second to the first rotary position. Such a gap usually appears during a short time period II of 0.05 to 0.10 seconds. During such a gear rotation, a zero torque is obtained in the gearbox. Because the control unit 11 with at least a frequency of 100 Hz receives information about the speeds of the gearbox input 4 and output 6 shafts, said gap in the gearbox 5 can be detected as a speed deviation between the shafts 4, 6 when said rotation takes place. The input shaft 4 obtains in the gap, during the time period II, a higher speed than the output shaft 6. The function value f calculated by the control unit 11 therefore receives a higher value of 1.00 during the time period II. In order to detect with certainty that a torque-free state prevails, the control unit 11 detects a zero torque in the gearbox 5 only when a deviation from the value 1.00 reaches a certain value a1. The value of the deviation a1 can vary for different gears. In Fig. 2, the deviation a is about 1%. When said deviation is obtained, the control unit 11 activates the shift mechanism 14 which shuts off the engaged gear. Thereafter, the control unit 11 activates the injection unit 13 to control the engine 1 speed so that a new gear can be engaged. 10 15 20 25 30 35 522 '900 During the subsequent time period III, the vehicle is driven with a positive torque in the gearbox 5. During the third time period III are the teeth in the first rotary position and the input shaft 4 and the output shaft 5 of the gearbox 5 have a corresponding speed with regard to the gear engaged in the gearbox 5. The function f here is substantially constant 1.00. At the end of the third time period III, the driver initiates a new gear to be engaged. A control signal is sent from the gear lever 12 to the control unit 11 which activates the fuel injection unit 13 so that the amount of fuel supplied to the engine 1 is reduced. The torque delivered by the engine 1 to the input shaft 4 of the gearbox decreases and a negative torque is obtained in the gearbox 5. In connection with the transition from a positive torque to a negative torque in the gearbox 5, the teeth in the gear engagement are rotated from the first to the second rotary position. During said rotation, the input shaft 4 obtains a lower speed than the output shaft 6. The functional value f calculated by the control unit 11 therefore receives a lower value than 1.00 during the time period IV. In order to establish with certainty that a torque-free state prevails, the control unit 11 detects a zero torque in the gearbox 5 only when such a deviation reaches a certain value az. The value of the deviation az varies for different gears and essentially corresponds to the value a1 for the corresponding gear. In Fig. 2, the deviation az is about 1%. When a function value f is obtained which corresponds to the deviation az, the control unit 11 activates the shift mechanism 14 which disengages the engaged gear. Thereafter, the control unit 11 activates the injection unit 13 to adjust the amount of fuel injection in order to control the engine speed 1 so that a new gear can be engaged.

The invention is in no way limited to the described embodiment but can be varied freely within the scope of the claims.

The invention is not limited to being used only to allow a torque-free laying of a gear in a gearbox but can be used in a substantially arbitrary context where it is desirable to detect a zero torque in a gearbox. Fig. 1 describes a manual shifting procedure in which the driver shifts into the desired gear by means of the shift lever 12. The invention is of course also applicable in connection with automatic and semi-automatic shifting procedures, ie when the control unit 11 decides when shifting is to take place and which gear is to be engaged.

Claims (14)

10 15 20 25 30 35 @ u u n en o 522 900 11 Patent claim An arrangement for detecting a zero torque in a gearbox, the gearbox (5) comprising an input shaft (4) adapted to receive a torque from a motor (1) and an output shaft (6) adapted to delivering a torque to an object (7-9), and the arrangement comprising a first sensor (15) adapted to sense a first parameter related to the speed of the input shaft (4) of the gearbox, a second sensor (16) which is arranged to sense a second parameter which is related to the speed of the output shaft (6) of the gearbox and a control unit (11) which is arranged to receive measured values relating to said first and second parameters, characterized in that the control unit (11) is arranged to compare whether the speed of the gearbox input shaft (4) and output shaft (6) corresponds with regard to the gear ratio of the gearbox engaged in the gearbox (5) and to detect a zero torque in the gearbox (5) in the event of a deviation between oc h The speed of the output shaft (6) occurs. Arrangement according to claim 1, characterized in that the control unit (11) is arranged to detect a zero torque in the gearbox (5) when such a deviation reaches a certain value (a1, az). Arrangement according to claim 2, characterized in that said determined value of the deviation (a1, ag) varies for different gears. Arrangement according to one of the preceding claims, characterized in that the control unit (11) is arranged to calculate a function (f) which comprises the ratio between the first parameter and the second parameter. Arrangement according to one of the preceding claims, characterized in that when a shift is desired to be carried out, the control unit (11) is arranged to regulate the output torque of the motor (1) so that it is adjusted in a 5 10 15 20 25 30 35 522 9 o year in fl ëilši - II = - “12 such direction so that a zero torque is allowed to be indicated in the gearbox (5). Arrangement according to one of the preceding claims, characterized in that when a shift is desired to be carried out, the control unit (11) is arranged to activate a shift mechanism (14) which shuts off the engaged gear when a zero torque is detected in the gearbox (5). Arrangement according to one of the preceding claims, characterized in that the output shaft (6) of the gearbox is arranged to deliver a torque to a driveline (7-9) in a vehicle. A method for detecting a zero torque in a gearbox, the gearbox (6) comprising an input shaft (4) arranged to receive a torque from a motor (1) and an output shaft (6) arranged to delivering a torque to an object (7-9), and wherein the method comprises the steps of sensing a first parameter related to the input shaft (4) of the gearbox, sensing a second parameter related to the output shaft (6 of the gearbox); ) speed and to receive measured values relating to said first and second parameters, k_'aj_r¿ characterized in that the method also includes the steps of comparing whether the input shaft (4) and output shaft (5) of the gearbox correspond with regard to the gear ratio of the engaged gear in the gearbox and to detect a zero moment in the gearbox (5) if a deviation occurs between the input shaft (4) of the gearbox and the output shaft (6) of the output shaft (6). Method according to claim 8, characterized by detecting a zero torque in the gearbox (5) when such a deviation reaches a certain value (a1, az). Method according to claim 9, characterized by varying said determined value of the deviation (a1, az) for different gears. 10 15 u ,, u nu u. N »I I"., ",, N. O I z f, ,, av I fi,, u u. '".. z: o o 00' °. u. o nu: ß v _ Q, _ .nu: _ _",,,. . . , v. ". - I I I 5 13 Method according to one of the preceding claims 8-10, characterized by calculating a function (f) which comprises the relationship between the first parameter and the second parameter. Method according to one of the preceding claims 8 to 11, characterized in that when a changeover is desired, the output motor torque is controlled so that it is adjusted in such a direction that a zero torque is allowed to be indicated in the gearbox (5). Method according to one of the preceding claims 8 to 12, characterized in that when a shift is desired to be carried out, a shifting mechanism (14) is activated which shuts off the engaged gear when a zero torque is detected in the gearbox (5). Method according to one of the preceding claims 8 to 13, characterized in that the output shaft (6) of the gearbox delivers a torque to a driveline (7-9) in a vehicle.