METHOD FOR CONTROLLING A TORQUE DISTRIBUTION BETWEEN A FRONT AXLE AND A REAR AXLE OF A VEHICLE

Abstract

One aspect of the invention relates to a method 100 for controlling a torque distribution between a front axle and a rear axle of an electric or hybrid vehicle, when a torque requested by a driver is between a determined percentage of a maximum torque of a front electric machine and a determined percentage of a maximum torque of a rear electric machine, the method executes the steps of: Generating 104 a front torque setpoint equal to said determined percentage of a maximum torque of said front electric machine and a rear torque setpoint equal to the requested torque from which said front torque setpoint is subtracted; Applying 105, to the front transmissions of the front axle, said front torque setpoint by means of said front electric machine and, to the rear transmissions of the rear axle, said rear torque setpoint by means of said rear electric machine. Figure 2

Description

Title of the invention: METHOD FOR CONTROLLING A TORQUE DISTRIBUTION BETWEEN A FRONT AXLE AND A REAR AXLE OF A VEHICLE

[0001] The technical field of the invention is that of the distribution of torque between a front axle and a rear axle of an electric or hybrid vehicle comprising at least one front electric machine arranged to rotate the front transmissions of the front axle and at least one rear electric machine arranged to rotate the rear transmissions of the rear axle.

[0002] It is known, in particular from document JP-A-2009278770, electric or hybrid vehicles whose supervisor identifies an engine torque desired by the driver as a function of the pedal depression. As a function of this driver request, the supervisor increases the torque setpoint transmitted to the front electric machine until it reaches a maximum torque that the front electric machine of the vehicle is capable of providing. When the front electric machine reaches its maximum torque and the driver requests even more torque, the supervisor sends as a setpoint to the rear electric machine a torque setpoint equal to the desired driver torque less the torque already achieved by the front electric machine.

[0003] In summary, the rear electric machine is only used when the front electric machine has reached its maximum torque. Thus, as soon as the driver requests a torque which exceeds the maximum torque of the front electric machine, the transverse transmissions of the front axle are subjected to a maximum torque load. This significant load on the transverse transmissions of the front axle causes premature wear of the latter.

[0004] The aim of the invention is to overcome the drawbacks of the prior art by proposing a method for increasing the service life of the front axle transmissions.

[0005] In this context, the invention thus relates, in its broadest acceptance, to a method for controlling a torque distribution between a front axle and a rear axle of an electric or hybrid vehicle, the vehicle comprising at least one front electric machine arranged to rotate the front transmissions of said front axle and a rear electric machine arranged to rotate the rear transmissions of said rear axle.

[0006] The method according to this aspect of the invention is remarkable in that it comprises, when a torque requested by a driver is between a determined percentage of a maximum torque of the front electric machine and a determined percentage of a maximum torque of the rear electric machine, the steps, executed by means of control, of: • Generate a forward torque setpoint equal to the determined percentage of a maximum torque of the forward electric machine and a reverse torque setpoint equal to the requested torque from which the forward torque setpoint is subtracted; • Apply the front torque setpoint to the front transmissions using the front electric machine and the rear torque setpoint to the rear transmissions using the rear electric machine.

[0007] The method according to the invention therefore consists of starting the rear electric machine when the front electric machine is at a certain percentage of its maximum torque, in other words before it reaches its maximum torque. The invention thus makes it possible to reduce fatigue and stress on the transmissions of the front axle of the vehicle. The invention therefore makes it possible to preserve the service life of the front transmissions, and not to oversize the front transmissions for durability, without limiting the performance of the vehicle.

[0008] In addition to the characteristics which have just been mentioned in the preceding paragraph, the method according to the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations.

[0009] According to a non-limiting aspect of the invention, when the requested torque is greater than the addition of the determined percentage of a maximum torque of the front electric machine with the determined percentage of a maximum torque of the rear electric machine, the method comprises the steps of: • Proportionally increase the front torque setpoint and the rear torque setpoint; • Apply the increased front torque setpoint to the front transmissions using the front electric machine and the increased rear torque setpoint to the rear transmissions using the rear electric machine.

[0010] According to a non-limiting aspect of the invention, the determined percentage of a maximum torque of the front electric machine and the determined percentage of a maximum torque of the rear electric machine are equal.

[0011] According to a non-limiting aspect of the invention, the determined percentage of a maximum torque of the front electric machine and the determined percentage of a maximum torque of the rear electric machine are different.

[0012] According to a non-limiting aspect of the invention, • The determined percentage of a maximum torque of the front electric machine is between 60% and 80%, and • The determined percentage of maximum torque of the rear electric machine is between 60% and 80%.

[0013] According to a non-limiting aspect of the invention, • The determined percentage of a maximum torque of the front electric machine is 70%, and • The determined percentage of maximum torque of the rear electric machine is 70%.

[0014] According to a non-limiting aspect of the invention, when the requested torque is equal to the determined percentage of a maximum torque of the front electric machine, the method comprises a step of clutching the rear electric machine to the rear axle of the vehicle.

[0015] According to a non-limiting aspect of the invention, when the requested torque is less than the determined percentage of a maximum torque of the front electric machine, the method comprises the steps of: • Generate a forward torque instruction equal to the requested torque; • Apply the front torque setpoint to the front transmissions using the front electric machine.

[0016] Another aspect of the invention relates to an electric or hybrid vehicle comprising at least one front electric machine arranged to rotate the front transmissions of a front axle and a rear electric machine arranged to rotate the rear transmissions of a rear axle of the vehicle, said vehicle being remarkable in that it comprises control means arranged to execute the steps of the method according to any one of the aforementioned aspects of the invention.

[0017] According to a non-limiting aspect of the invention, the control means are formed by: • A vehicle control computer; • A front engine control computer; and • A rear engine control computer.

[0018] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures.

[0019] [[Fig.l] illustrates, schematically, a vehicle according to a non-limiting aspect of the invention.

[0020] [Fig.2] schematically represents a non-limiting mode of implementation of the method according to the invention.

[0021] [Fig.3] schematically represents a torque distribution graph between a front axle and a rear axle of a vehicle according to a non-limiting aspect of the invention.

[0022] [Fig.l] illustrates an electric vehicle 1 arranged to implement the method according to the invention. The electric vehicle 1 comprises in particular: • A front electric machine 2 arranged to rotate the front transmissions 3 of a front axle 4, • A rear electric machine 5 arranged to rotate the rear transmissions 6 of a rear axle 7, and • Control means 8 arranged to execute the steps of the method according to the invention illustrated in [Fig.2].

[0023] According to a non-limiting implementation, the control means 8 are formed by: • An 8i vehicle control computer; • An engine control computer before 82; and • A rear engine control computer 83.

[0024] [Fig. 2] illustrates a non-limiting implementation of a control method 100 of a torque distribution between the front axle 4 and the rear axle 7 of the vehicle 1.

[0025] When the torque requested by the driver of the vehicle 1 is less than a determined percentage of a maximum torque of the front electric machine 2, the method 100 comprises a step of generating 101, by means of the vehicle control computer 8i, a front torque setpoint equal to the requested torque.

[0026] The torque requested by the driver is determined by the vehicle control computer 8i based on the information it receives from a sensor measuring the pressure on the accelerator pedal.

[0027] According to a non-limiting implementation of the invention, the determined percentage of a maximum torque of the front electric machine 2 can be between 60% and 80%, for example 70%.

[0028] The method 100 then comprises a step of applying 102, to the front transmissions 3, the front torque setpoint by means of the front electric machine 2.

[0029] To this end, the vehicle control computer 8i transmits the generated front torque setpoint to the front engine control computer 82. The front engine control computer 82 then controls the front electric machine 2 so as to apply the front torque setpoint.

[0030] In [Fig. 3], the white bars represent the torque supplied by the front electric machine 2 and the gray bars represent the torque supplied by the rear electric machine 5. Thus, as can be seen in [Fig. 3], as long as the torque requested by the driver of the vehicle 1 is less than the determined percentage of 70% of the maximum torque of the front electric machine 2, the torque supplied by the front electric machine 2 is equal to the requested torque. In other words, the rear electric machine 5 is not used.

[0031] According to a non-limiting example, when the torque requested by the driver reaches the determined percentage, namely 70% in the example, of the maximum torque of the front electric machine 2, the method 100 comprises a step of coupling 103 the rear electric machine 5 to the rear axle 7 of the vehicle 1.

[0032] To this end, the vehicle control computer 8 transmits a dog clutch instruction to the rear engine control computer 83.

[0033] Then, when the torque requested by the driver is between the determined percentage of the maximum torque of the front electric machine 2 and a determined percentage of a maximum torque of the rear electric machine 5, the method 100 comprises a step of generating 104, by means of the vehicle control computer 8b, a front torque setpoint equal to the determined percentage of the maximum torque of the front electric machine, namely 70% in the example, and a rear torque setpoint equal to the requested torque from which said front torque setpoint is subtracted.

[0034] According to a non-limiting implementation of the invention, the determined percentage of a maximum torque of the rear electric machine 5 may be between 60% and 80%, for example 70%.

[0035] The method 100 then comprises a step 105 of applying, to the front transmissions 4, the front torque setpoint by means of the front electric machine 2 and, to the rear transmissions 7, the rear torque setpoint by means of the rear electric machine 5.

[0036] More particularly, the vehicle control computer 8i transmits the generated front torque setpoint to the front engine control computer 82 and the generated rear torque setpoint to the rear engine control computer 83. The front engine control computer 82 then controls the front electric machine 2 so as to apply the front torque setpoint and the rear engine control computer 83 controls the rear electric machine 5 so as to apply the rear torque setpoint.

[0037] As can be seen in [Fig.3], when the torque requested by the driver of the vehicle 1 is greater than the determined percentage of 70% of the maximum torque of the front electric machine 2, the rear electric machine 5 is requested to provide the additional torque.

[0038] Then, when the driver torque is greater than the addition of the determined percentage of a maximum torque of the front electric machine 2 with the determined percentage of a maximum torque of the rear electric machine 5, the method 100 comprises a step 106 of proportionally increasing the front torque setpoint and the rear torque setpoint.

[0039] It then comprises a step of applying 107, to the front transmissions 3, the front torque setpoint increased by means of the front electric machine 2 and, to the rear transmissions 6, the rear torque setpoint increased by means of the rear electric machine 5.

[0040] More particularly, the vehicle control computer 8i transmits the instruction of increased front torque to the front engine control computer 82 and the increased rear torque setpoint to the rear engine control computer 83. Then, the front engine control computer 82 controls the front electric machine 2 so as to apply the increased front torque setpoint to the front transmissions 3 and the rear engine control computer 83 controls the rear electric machine 5 so as to apply the increased rear torque setpoint to the rear transmissions 6.

[0041] Thus, as can be seen in [Fig. 3], when the torque requested by the driver of the vehicle 1 is greater than the addition of the determined percentage of 70% of the maximum torque of the front electric machine 2 and the determined percentage of 70% of the maximum torque of the rear electric machine 5, the torque supplied by the front electric machine 2 and the torque supplied by the rear electric machine 5 are increased proportionally.

[0042] It should be noted that in the example described, the determined percentage of a maximum torque of the front electric machine 2 and the determined percentage of a maximum torque of the rear electric machine 5 are equal, but it is understood that the latter may, according to a variant of the invention, be different.

[0043] The various aspects of the invention mentioned above have numerous advantages. Among these, we can cite: • Reduce stress on front transmissions; • Improve the handling of front transmissions by reducing fatigue on these transmissions; • Avoid having to oversize the front transmissions; and • Reduce the cost and mass of front transmissions.

Claims

Claims

1. Method (100) for controlling a torque distribution between a front axle (4) and a rear axle (7) of an electric or hybrid vehicle (1), said vehicle (1) comprising at least one front electric machine (2) arranged to rotate front transmissions (3) of said front axle (4) and one rear electric machine (5) arranged to rotate rear transmissions (6) of said rear axle (7), said method (100) being characterized in that it comprises, when a torque requested by a driver is between a determined percentage of a maximum torque of said front electric machine (2) and a determined percentage of a maximum torque of said rear electric machine (5), the steps, executed by control means (8), of: • Generate (104) a forward torque setpoint equal to said determined percentage of a maximum torque of said forward electric machine (2) and a reverse torque setpoint equal to the requested torque from which said forward torque setpoint is subtracted; • Apply (105), to said front transmissions (3), said front torque setpoint by means of said front electric machine (2) and, to said rear transmissions (7), said rear torque setpoint by means of said rear electric machine (5).

2. Method (100) according to the preceding claim, characterized in that when the driver torque is greater than the addition of the determined percentage of a maximum torque of the front electric machine (2) with the determined percentage of a maximum torque of the rear electric machine (5), the method (100) comprises the steps of: - Proportionally increase (106) the front torque setpoint and the rear torque setpoint; - Apply (107), to the front transmissions (4), said increased front torque setpoint by means of the front electric machine (2) and, to the rear transmissions (7), said increased rear torque setpoint by means of the rear electric machine (5).

3. Method (100) according to any one of the preceding claims, characterized in that the determined percentage of a maximum torque of the front electric machine (2) and the determined percentage of a maximum torque of the rear electric machine (5) are equal.

4. Method (100) according to any one of claims 1 or 2, characterized in that the determined percentage of a maximum torque of the front electric machine (2) and the determined percentage of a maximum torque of the rear electric machine (5) are different.

5. Method (100) according to any one of the preceding claims, characterized in that: - The determined percentage of a maximum torque of the front electric machine (2) is between 60% and 80%, and - The determined percentage of a maximum torque of the rear electric machine (5) is between 60% and 80%.

6. Method (100) according to the preceding claim, characterized in that: - The determined percentage of a maximum torque of the front electric machine (2) is 70%, and - The determined percentage of a maximum torque of the rear electric machine (5) is 70%.

7. Method (100) according to any one of the preceding claims, characterized in that when the requested torque is equal to the determined percentage of a maximum torque of the front electric machine (2), the method (100) comprises a step of clutching (103) the rear electric machine (5) to the rear axle (7) of the vehicle (1).

8. Method (100) according to any one of the preceding claims, characterized in that when the requested torque is less than the determined percentage of a maximum torque of the front electric machine (2), the method (100) comprises the steps of: - Generating (101) a front torque setpoint equal to the requested torque; - Applying (102), to the front transmissions (4), said front torque setpoint by means of said front electric machine (2).

9. Electric or hybrid vehicle (1) comprising at least one front electric machine (2) arranged to rotate front transmissions (3) of a front axle (4) and a rear electric machine (5) arranged to rotate rear transmissions (6) of a rear axle (7) of said vehicle (1), said vehicle (1) being characterized in that it comprises control means (8) arranged to execute the steps of the method (100) according to any one of the preceding claims.

10. Vehicle (1) according to the preceding claim, characterized in that the control means (8) are formed by: - ​​A vehicle control computer (8i); - A front engine control computer (82); and - A rear engine control computer (83).

Images