FR3081790A1 - CENTRALIZED SYNCHRONIZATION GEARBOX - Google Patents

Abstract

Gearbox comprising two primary shafts (AP1, AP2), two secondary shafts (AS1, AS2), and pinion pairs (CP1-CP6), each of said pairs having more than one coupling means (C1-C6) a crazy gear. The box includes an electric machine (MEL) comprising an output shaft (AO) coupled to the secondary shafts (AS1, AS2) by pairs of pinions for synchronization (CP10, CP20), including, within each pair of pinions for synchronization, one pinion is mounted idly on the output shaft of the machine and the other is fixedly mounted on the primary shaft. First and second synchronizers (S10, S20) are each associated with one of said idler gears and control means (110) of the electric machine and said synchronizers brings, during the transition between two gear ratios, the primary shaft corresponding to a speed suitable for closing the clutch.

Description

"CENTRALIZED SYNCHRONIZATION GEARBOX" The invention is in the field of discrete ratio gearboxes for motor vehicles with an internal combustion engine. This heat engine can be the sole engine of a purely thermal engine, or be inserted in a hybrid thermal and electric engine, in which depending on road conditions, it takes over from an electric machine, is relayed by such machine, or participate simultaneously with it in setting and keeping the vehicle moving. In particular, the vehicle can be a conventional hybrid ("full hybrid") or rechargeable hybrid ("plug-in hybrid electric vehicle", PHEV).

The gearboxes concerned are double clutch gearboxes, controlled by a control system. They include pairs of pinions, each defining a gear ratio, distributed over two pairs of shafts, two of them being primary shafts driven by the heat engine, and the other two secondary shafts connected to the drive train.

Conventionally, the gear ratios are engaged using synchronizers which allow, when engaging a gear, to gradually change the rotation speed of the primary shaft to bring it to the corresponding speed at current wheel speed, close to the gear to be engaged. Once the shaft speed has been adjusted, the corresponding clutch is closed.

Synchronizers avoid jolts by the use of friction surfaces, called friction cones. But friction induces a loss of energy, which leads to unnecessarily high fuel consumption.

In addition, the synchronizers are bulky in the axial direction of the shafts. The length of the gearbox is therefore adversely affected, especially since the number of reports is now often high - up to 8 reports often, and the lengths occupied by the synchronizers add up.

Finally, each synchronizer requires a control actuator, which complicates the control of the switching of reports.

Document FR3056157_A1 describes a dual-clutch gearbox installed on a hybrid thermal and electric motor, but including as many synchronizers as there are ratios, which lengthens the system in the direction of the shafts, and complicates control.

To solve these problems, there is proposed a gearbox for a power chain comprising two primary shafts each provided with a clutch for receiving the power of an engine, two secondary shafts for transmitting the power to a train of wheels drive, and to transmit the power from the primary shafts to the secondary shafts with different gear ratios, pairs of driven pinions, one of the pinions of each pair being fixedly mounted on the associated primary shaft, and the other pinion of the pair being idly mounted on the associated secondary shaft, each of said pairs of pinions having more than one means of coupling the idler pinion to the associated secondary shaft to engage the corresponding gear ratio.

The gearbox is remarkable because it further comprises an electric machine comprising an output shaft coupled to the two primary shafts respectively by pairs of pinions driven for synchronization, of which, within each pair of pinions for synchronization , one pinion is mounted idler on the output shaft of the electric machine and the other is fixedly mounted on the associated primary shaft, the gearbox further comprising a first and a second synchronizers each associated with one of said idler pinions mounted on the output shaft of the electric machine and a control means of the electric machine and said synchronizers to bring, during the transition between two contiguous gear ratios, the primary shaft corresponding to the gear to be engaged, at a speed suitable for closing the corresponding clutch.

Thanks to this principle of centralized synchronization, friction losses are reduced: the number of synchronizers can be limited to two and the number of friction cones per synchronizer can be reduced because the electric motor is controlled so as to synchronize the speeds , the two synchronizers mounted on the output shaft of the electric machine being used so as not to have to set up an electric machine control which is too complex.

Still thanks to this principle, the gearbox is shorter in the direction of the trees, since there is no need to set up a relative synchronizer.

In addition, manufacturing costs and fuel consumption are reduced.

The electric machine only serves to synchronize the speed of the primary shafts. It can be a small machine, which only applies its torque for a few milliseconds.

The following characteristics are optional and advantageous:

- The coupling means of the idler gears to the associated primary shaft are dog clutch;

- the control means closes the dog associated with the gear ratio to be engaged after the corresponding primary shaft has reached the speed adapted to the closure of the corresponding clutch, and then closes said corresponding clutch;

- The first and second synchronizers are with a single friction cone;

- each of the two primary shafts is connected to the associated secondary shaft by three pairs of pinions defining as many gear ratios;

- The control means receives the wheel speeds, the driver's command and the speeds of the primary shafts.

The invention also relates to a power chain for a motor vehicle comprising a gearbox according to the above characteristics, which comprises a heat engine for applying power to one or the other of the primary shafts.

The invention also relates to a motor vehicle comprising such a power chain for its rolling.

The invention also relates to a method for changing from a gear ratio to a contiguous gear ratio within a gearbox for a power chain comprising two primary shafts each provided with a clutch for receiving the power of a motor, two secondary shafts to transmit power to a train of driving wheels, and to transmit power from primary shafts to secondary shafts with different gear ratios, pairs of driven sprockets, one of the sprockets of each torque being fixedly mounted on the associated primary shaft, and the other pinion of the torque being idly mounted on the associated secondary shaft, each of said pairs of pinions having more than one means of coupling the idler pinion to the secondary shaft associated to engage the corresponding gear ratio.

The method is remarkable in that it includes bringing the primary shaft corresponding to the gear to be engaged, at a speed adapted to the closing of the corresponding clutch by the control of an electric machine and synchronizers carried by an output shaft of the electric machine, said output shaft being coupled to the two primary shafts respectively by pairs of pinions driven for synchronization, of which, within each pair of pinions for synchronization, a pinion is mounted idler on the output shaft of the electric machine and associated with one of the two synchronizers and the other is fixedly mounted on the associated primary shaft.

The method can also include in this order, once the primary shaft brought to said speed, closing the coupling means to the secondary shaft of the idler gear associated with the gear to be engaged, then closing the corresponding clutch.

The invention will be better understood, and other objects, characteristics, details and advantages thereof will appear more clearly in the explanatory description which follows, made with reference to the appended drawings given solely by way of example illustrating a embodiment of the invention and in which:

- Figure 1 is a view of a power transmission chain according to the prior art;

- Figure 2 is a view of a power transmission chain according to the invention;

- Figure 3 is a representation of the steps implemented in the power transmission chain.

In Figure 1 there is shown a power transmission chain of a motor vehicle according to the prior art. The vehicle concerned is a vehicle with an internal combustion engine and a dual-clutch gearbox. Such a gearbox is controlled by a control means 100 which receives information from various sensors, in particular wheel speed sensors 105, and which also receives commands from the driver, in the form of commands 106.

The power transmission chain transmits the power generated by the MTH heat engine to the drive wheel train R. The drive wheel train R receives the power via a bridge P coupled by pairs of pinions driven by two secondary shafts AS1 and AS2.

The heat engine MTH provides its power to two primary shafts AP1 and AP2 which are coupled to it via two clutches EMB1 and EMB2, controlled by the control means 100. The primary shafts AP1 and AP2 are generally concentric , as well as the associated clutches.

The primary shaft AP1 and the secondary shaft AS1 can be coupled to one another by one or the other of three pairs of pinions CP1, CP2 and CP3, and the primary shaft AP2 and the secondary shaft AS2 can be coupled to one another by one or the other of three pairs of driven pinions CP4, CP5 and CP6.

Each of the pinion pairs CP1 to CP6 defines a different speed ratio between the speed of rotation of the output shaft of the heat engine MTH and the speed of rotation of the drive wheel set R.

Each of the pairs of pinions CP1 to CP6 is made up as follows: a pinion fixedly mounted on the corresponding primary shaft, and a pinion idly mounted on the corresponding secondary shaft.

In the prior art, the engagement of a gear ratio is carried out by the use of a synchronizer associated with the corresponding pair of pinions, the synchronizers being referenced S1 to S6, with a numbering which follows the numbering of pairs of sprockets CP1 to CP6, the synchronizer coming, under the control of the control means 100, causing the drive of the idler mounted sprocket by the secondary shaft on which it is mounted.

The use of a synchronizer allows, by allowing friction, to ensure that the rotational speeds of the primary shaft and the secondary shaft are brought into coincidence without the mechanism being abrupt. In fact, when the synchronizer is closed, the secondary shaft rotates at a speed which is proportional to that of the speed of rotation of the driving wheel set R while the corresponding primary shaft is generally stopped, the corresponding clutch, being open.

Thus the use of the synchronizer allows the progressive rotation of the primary shaft, smoothly, until the primary shaft rotates at the speed corresponding to the speed of the vehicle, taking into account the ratio that is being engaged. From then on, the corresponding clutch can be closed. Naturally the closing of the corresponding clutch is carried out simultaneously with the opening of the other clutch, so that the change of gear ratio takes place smoothly.

This arrangement has the disadvantage that the synchronizers are bulky devices, and that their control is complex, in particular because they are in large number, here six in number.

In Figure 2 there is shown an embodiment of the invention. This is an evolution of the system shown in Figure 1. As before, the power of an MTH heat engine is transferred to a set of drive wheels R.

Again the power passes through one or the other of two primary shafts AP1 and AP2 and one or the other of the two secondary shafts AS1 and AS2. The primary shafts are connected to the output of the MTH heat engine and the secondary shafts are connected to the P axle of the drive wheel set R.

As before, pairs of pinions CP1 to CP6 define gear ratios. The pinion pairs CP1 to CP3 are carried by the primary and secondary shafts AP1 and AS1, and the pinion pairs CP4 to CP6 are carried by the primary and secondary shafts AP2 and AS2.

Unlike the prior art, the idler pinions carried by the secondary shafts AS1 and AS2, and forming with a fixed pinion carried by the primary shaft AP1 and AP2 corresponding to the pairs of pinions defining a gear ratio, are, for engaging the gear ratio, fixed, reversibly, to the corresponding secondary shaft by means of dogs referenced C1 to C6.

Thus, there is no provision for an individual rotation speed synchronization function for each pair of pinions defining a gear ratio.

On the other hand, the primary shaft AP1 can be coupled with a tertiary shaft A0 using a pair of driven pinions CP10 and the primary shaft AP2 can be coupled with the same tertiary shaft A0 using of a couple of CP20 driven pinions.

The tertiary shaft A0 is the output shaft of an MEL electric machine. The pinion pairs CP10 and CP20 consist of a fixed pinion mounted on the corresponding primary shaft and a idler pinion mounted on the tertiary shaft A0.

Two synchronizers S10 and S20 make it possible to create a drive between the tertiary shaft AO and the idler pinion of the pair of pinions CP10, respectively, or the idler pinion of the pair of pinions CP20. Thus, these synchronizers S10 and S20 make it possible to transmit a movement from the electric machine MEL to the primary shaft AP1 or the primary shaft AP2 respectively, and to bring these at a speed defined by the control system 110, to from a zero speed, the corresponding clutch being open and all the dogs carried by the associated secondary shaft being also open.

The control system 110 receives wheel speed information 105, acceleration control information by the driver 106 and speed information from the primary shafts 107.

Thus we have a set of two centralized synchronizers which are controlled in rotation speed by the electric machine MEL, which can be small, and only operate for a few milliseconds. The dogs C1 to C6 are actuated after the synchronization phase carried out by one of the synchronizers S10 or S20, depending on the gear to be engaged.

We will for example describe here a gear shift between the ratios 3 and 2. It is therefore a demotion.

First the vehicle drives with the dog corresponding to the gear ratio 3 engaged. This is the C4 dog clutch. The EMB1 clutch is open, and the EMB2 clutch is closed.

The control means 110 determines the synchronization speed for the synchronizer S10, so as to engage the dog corresponding to the gear ratio 2 without cracking. The dog corresponding to the gear ratio 2 is the dog C3.

To obtain the correct synchronization speed, the control means 110 takes into account the speed of the wheels, supplied by the sensors 105 and the speed of the primary shafts AP1 and AP2 supplied by the sensors 107. Naturally the control means 110 also takes into account the structural characteristics of the gearbox which are the characteristics of the P-axle, the gear reduction ratio of the pinion pair CP3 corresponding to the gear ratio 2, and the characteristics of the synchronizer S10.

Once the primary shaft AP1 brought to the correct rotation speed thanks to the electric machine MEL and to the synchronizer S10, as well as to the pair of pinions CP10, during a step E1, the control means 110 controls the dog clutch C3, during a step E2.

Once the gear ratio engaged by the dog clutch C3 can be crossed the clutches during a step E3, that is to say open the clutch EMB2 and 5 close the clutch EMB1 and perform thus the change of gear ratio.

Claims (10)

1. Gearbox for power chain comprising two primary shafts (AP1, AP2) each provided with a clutch (EMB1, EMB2) to receive engine power (MTH), two secondary shafts (AS1, AS2) for transmit the power to a train of driving wheels (R), and to transmit the power from the primary shafts (AP1, AP2) to the secondary shafts (AS1, AS2) with different gear ratios, pairs of pinions (CP1-CP6) , one of the pinions of each pair being fixedly mounted on the associated primary shaft, and the other pinion of the couple being idly mounted on the associated secondary shaft, each of said pairs of pinions having more than one coupling means (C1-C6) from the idler gear to the associated secondary shaft for engaging the corresponding gear ratio, characterized in that the gearbox further comprises an electric machine (MEL) comprising an output shaft (AO) coupled to the two primary trees (AP1, AP2) by resp ectively pairs of pinions driven for synchronization (CP10, CP20), of which, within each pair of pinions for synchronization (CP10, CP20), a pinion is mounted idly on the output shaft (AO) of the machine electric (MEL) and the other is fixedly mounted on the associated primary shaft (AP1, AP2), the gearbox further comprising first and second synchronizers (S10, S20) each associated with one of said idler gears mounted on the output shaft (AO) of the electric machine and a control means (110) of the electric machine (MEL) and of said synchronizers (S10, S20) to bring, during the transition between two contiguous gear ratios, l primary shaft (AP1, AP2) corresponding to the gear to be engaged, at a speed adapted to the closing of the corresponding clutch (EMB1, EMB2). 2. Gearbox according to claim 1, characterized in that the coupling means (C1-C6) of the idler gears to the associated secondary shaft (AS1, AS2) are dog dogs. 3. Gearbox according to claim 2, characterized in that the control means (110) closes the dog clutch (C-C6) associated with the gear ratio to be engaged after the corresponding primary shaft (AP1, AP2) has reached the speed adapted to the closure of the corresponding clutch (EMB1, EMB2), and then closes said corresponding clutch (EMB1, EMB2). 4. Gearbox according to one of claims 1 to 3, characterized in that the first and second synchronizers (S10, S20) are with single friction cone. 5. Gearbox according to one of claims 1 to 4, characterized in that each of the two primary shafts (AP1, AP2) is connected to the secondary shaft (AS1, AS2) associated by three pairs of pinions defining as many gear ratios. 6. Gearbox according to one of claims 1 to 5, characterized in that the control means receives the speeds of the wheels (105), the driver's command (106) and the speeds of the primary shafts (107). 7. Power chain for a motor vehicle comprising a gearbox according to one of claims 1 to 6, characterized in that it comprises a heat engine (MTH) for applying power to one or the other of the primary trees. 8. Motor vehicle comprising a power chain according to claim 7. 9. Method for changing from a gear ratio to a contiguous gear ratio within a gearbox for a power chain comprising two primary shafts (AP1, AP2) each provided with a clutch (EMB1, EMB2) for receive the power from a motor (MTH), two secondary shafts (AS1, AS2) to transmit power to a train of drive wheels (R), and to transmit power from the primary shafts (AP1, AP2) to the secondary shafts ( AS1, AS2) with different gear ratios, pairs of driven pinions (CP1-CP6), one of the pinions of each pair being fixedly mounted on the associated primary shaft, and the other pinion of the pair being idly mounted on the associated secondary shaft, each of said pairs of pinions having more than one coupling means (C1-C6) of the idler pinion to the associated secondary shaft for engaging the corresponding gear ratio, characterized in that the method comprises the bringing the primary tree (AP1, AP2) corresponding to the gear to be engaged, at a speed suitable for closing the clutch (EMB1, EMB2) corresponding by the control (110) of an electric machine (MEL) and synchronizers (S10, S20) carried by an output shaft (A0) of the electric machine, said output shaft (A0) being coupled to the two primary shafts (AP1, AP2) by pairs of pinions respectively driven for synchronization (CP10, CP20), of which, within each pair of pinions for synchronization (CP10, CP20), a pinion is mounted idly on the output shaft (A0) of the electric machine (MEL) and associated with one of the two synchronizers and the other is mounted fixed on the associated primary shaft (AP1, AP2). 10. A method of passing a gear ratio according to claim 9, characterized in that it comprises the fact, in this order, once the primary shaft brought to said speed, close (E2) the coupling means (C1-C6) to the secondary shaft (AS1, AS2) of the idler gear associated with the gear to be engaged, then the fact of closing (E3) the corresponding clutch (EMB1, EMB2).