Drive system

Abstract

The present application aims to more appropriately control the torque distribution to the front and rear wheels, thereby further improving the stability of the vehicle. A drive system includes: a first power source provided to a vehicle; a transfer that distributes a drive torque generated by the first power source to a first wheel device and a second wheel device at a fixed distribution ratio; a cut mechanism that can transmit and cut the drive torque generated by the first power source to the transfer; a second power source provided between the transfer and the second wheel device; and a control device that controls the first power source and the second power source in such a manner that a first drive torque transmitted to the first wheel device and a second drive torque transmitted to the second wheel device become a target torque ratio. The control device instructs the cut mechanism to transmit the drive torque generated by the first power source to the transfer when it is determined that the transmission of the driving force of the second wheel device to the road surface is in an incomplete state.

Description

Technical Field

[0001] This invention relates to a drive system. Background Technology

[0002] Patent Document 1 disclosed a control method for slippage in a hybrid vehicle in which an engine is located upstream of the transfer case and an electric motor is located downstream of the transfer case.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2020-168971 Summary of the Invention

[0004] Patent document 1 disclosed a method of reducing motor torque when front wheel slippage is detected, but did not disclose a more appropriate control of torque distribution to the front and rear wheels to further improve vehicle stability.

[0005] In this invention, the torque distribution to the front and rear wheels is more appropriately controlled, thereby further improving vehicle stability.

[0006] This invention provides a drive system comprising: a first power source disposed in a vehicle having a first wheel assembly and a second wheel assembly arranged front-to-back along a direction of travel; a transfer case that distributes the drive torque generated by the first power source to the first wheel assembly and the second wheel assembly through a fixed distribution ratio; a cut-off mechanism capable of transmitting and cutting off the drive torque generated by the first power source to the transfer case; a second power source disposed between the transfer case and the second wheel assembly; and a control device that controls the first power source and the second power source in such a way that the first drive torque transmitted to the first wheel assembly and the second drive torque transmitted to the second wheel assembly are a target torque ratio. When the control device determines that the transmission of the drive force from the second wheel assembly to the road surface is incomplete, it instructs the cut-off mechanism to transmit the drive torque generated by the first power source to the transfer case.

[0007] Invention Effects

[0008] According to the present invention, the torque distribution to the front and rear wheels can be controlled more appropriately, thereby further improving the stability of the vehicle. Attached Figure Description

[0009] Figure 1 This is a diagram illustrating a structural example of the drive system in this embodiment.

[0010] Figure 2 This is an example Figure 1 The diagram shows a schematic of the transfer case.

[0011] Figure 3 It is used for explanation Figure 1 The flowchart shows the operation of the control device. Detailed Implementation

[0012] Hereinafter, this embodiment will be described with reference to the accompanying drawings. To facilitate understanding, the same components in each figure will be labeled with the same symbols as much as possible, and repeated descriptions will be omitted.

[0013] like Figure 1 As shown, the drive system 2 involved in this embodiment includes a control device 21, a transfer case 22, a front wheel assembly 23f, a rear wheel assembly 23r, a transmission 24, a generator 25, an engine 26, and a generator 27.

[0014] The front wheel assembly 23f and the rear wheel assembly 23r are drive wheels used to propel the vehicle forward or backward. The front wheel assembly 23f has a right front wheel and a left front wheel connected to each end of the front axle. The rear wheel assembly 23r has a right rear wheel and a left rear wheel connected to each end of the rear axle.

[0015] Engine 26 is, for example, a mechanism for extracting driving force by burning fuel internally. Generator 25 functions as both an electric motor that generates driving force and a generator.

[0016] The driving force generated by the engine 26 and the driving force generated by the electric motor generator 25 are transmitted to the transfer case 22 via the transmission 24. The transmission 24 is provided with a cut-off mechanism (not shown) capable of transmitting and cutting off the driving force generated by the engine 26 and the electric motor generator 25 to the transfer case 22. The cut-off mechanism need only be a mechanism capable of engaging and releasing the output shaft (not shown) of the transfer case 22 from which the driving force generated by the engine 26 and the electric motor generator 25 are transmitted; a known power transmission / cut-off mechanism can be used.

[0017] Transfer case 22 is a mechanism that distributes the driving force generated by the electric motor generator 25 and the engine 26 to the front wheel assembly 23f and the rear wheel assembly 23r. Transfer case 22 distributes the driving force to the front wheel assembly 23f and the rear wheel assembly 23r, for example, by a fixed distribution ratio.

[0018] The generator 27 is located between the transfer case 22 and the rear wheel assembly 23r. Alternatively, the generator 27 can be located between the transfer case 22 and the front wheel assembly 23f.

[0019] The control device 21 includes a microcomputer (hereinafter referred to as a microcontroller) as an electrical component, a data transmission circuit, a power supply circuit, and a power detection circuit. The microcontroller includes a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and flash memory.

[0020] The speed information of each wheel is input from the front wheel assembly 23f and the rear wheel assembly 23r to the control device 21. The throttle opening information is input to the control device 21 as the driver's requested torque Td. The control device 21 performs calculations based on the input information and outputs control information to the motor generator 25, the engine 26, and the motor generator 27.

[0021] refer to Figure 2 The schematic diagram of transfer case 22 illustrates the torque distribution of transfer case 22. In transfer case 22, the output torque To of transmission 24 is used as ATOUT input and distributed to the front differential output FrDF and the rear differential output RrDF. The torque distribution ratio between the front differential output FrDF and the rear differential output RrDF is fixed.

[0022] The front differential output FrDF is output as the front wheel torque Tfr towards the front wheel assembly 23f and directly transmitted to the front wheel assembly 23f as the front wheel drive torque Tfrd. The rear differential output RrDF is output as the rear wheel torque Trr towards the rear wheel assembly 23r. In the rear wheel assembly 23r, the drive torque output by the generator 27 overlaps with the rear wheel torque Trr and is transmitted as the rear wheel drive torque Trrd. The torque distribution ratio of the transfer case 22 is fixed, but in the rear wheel assembly 23r, the drive torque output by the generator 27 overlaps with the rear wheel torque Trr and is transmitted accordingly. Therefore, the torque distribution ratio transmitted to the front wheel assembly 23f and the rear wheel assembly 23r varies depending on the operating conditions of the generator 27.

[0023] For example, from an efficiency point of view, it is preferable to drive the vehicle from the power source by power transmission without using gears or the like as much as possible. From this point of view, it is preferable to transmit only the drive torque output by the electric motor generator 27 to the rear wheel assembly 23r. The upstream side of the transfer case 22 is preferably set to the optimal operating state. For example, the output torque To of the transmission 24 is set to 0, the output torque of the engine 26 is set to 0, and the electric motor generator 25 outputs torque to compensate for the losses of the engine 26 and the transmission 24. In this state, regardless of the output torque of the electric motor generator 27, the front wheel torque Tfr and the rear wheel torque Trr are both 0. In the case of this embodiment, since a cut-off mechanism is provided in the transmission 24, the optimal operation is when the output torque of the engine 26 is set to 0, the output torque of the electric motor generator 25 is also set to 0, and the cut-off mechanism is in the state of releasing the output shaft.

[0024] In high-μ road driving with little wheel slippage, the impact of this torque output state is small. However, in low-μ road driving with relatively large wheel slippage, the driving force of the front wheel assembly 23f cannot be adjusted, which may damage the driving force. The purpose of this invention is to avoid this state, balancing high-efficiency operation and driving stability on low-μ roads.

[0025] refer to Figure 3 The control method that balances high-efficiency operation and low-μ road driving stability is explained.

[0026] In step S01, the control device 21 calculates the speed difference between the front and rear wheels, spdif. The speed difference between the front and rear wheels, spdif, is calculated by subtracting the speed of the rear wheel, sprr, from the speed of the front wheel, Fr, of the front wheel assembly 23f, spfr, from the speed of the rear wheel, Rr, of the rear wheel assembly 23r.

[0027] In step S02 following step S01, the control device 21 determines whether the absolute value of the speed difference spdif between the front and rear wheels is greater than the speed difference threshold spth. If the absolute value of the speed difference spdif between the front and rear wheels is greater than the speed difference threshold spth (step S02: Yes), the process proceeds to step S03. If the absolute value of the speed difference spdif between the front and rear wheels is not greater than the speed difference threshold spth (step S02: No), the process proceeds to step S04.

[0028] In step S03, the control device 21 outputs a control signal to the cut-off mechanism of the transmission 24, instructing the output shaft to engage. After the output shaft is engaged, the control device 21 drives the engine 26 and the generator 25 to generate the required front wheel torque Tfr. In the relationship between the output torque To of the transmission 24 and the front wheel torque Tfr, the gear ratio (torque distribution ratio) of the transfer case 22 is set to ρ, becoming Tfr = ρ / (1+ρ)·To. While driving the engine 26 and the generator 25, the control device 21 also adjusts the drive of the generator 27 to achieve the required rear wheel drive torque Trrd. By driving the engine 26 and the generator 25, the rear wheel torque Trr = 1 / (1+ρ)·To is generated; therefore, the drive of the generator 27 is adjusted so that it, together with the rear wheel torque Trr, becomes the required rear wheel drive torque Trrd.

[0029] In step S04, the control device 21 outputs a control signal to the cutting mechanism of the transmission 24, instructing the output shaft to be released.

[0030] The above description of this embodiment is based on specific examples. However, the present invention is not limited to these specific examples. Any invention obtained by the artisan through appropriate design modifications to these specific examples, as long as they possess the features of the present invention, is also included within the scope of the present invention. The elements, their configurations, conditions, shapes, etc., of the aforementioned specific examples are not limited to the illustrated elements and can be appropriately modified. The elements of the aforementioned specific examples can be appropriately combined as long as they do not create technical contradictions.

[0031] [Postscript]

[0032] [Postscript 1]

[0033] A drive system comprising:

[0034] The first power source is provided in a vehicle having a first wheel assembly and a second wheel assembly arranged front to back along the direction of travel.

[0035] The transfer case distributes the driving torque generated by the first power source to the first wheel assembly and the second wheel assembly through a fixed distribution ratio.

[0036] A cutting-off mechanism that can transmit and cut off the drive torque generated by the first power source to the transfer case;

[0037] A second power source, which is located between the transfer case and the second wheel assembly; and

[0038] The control device controls the first power source and the second power source in such a way that the first driving torque transmitted to the first wheel assembly and the second driving torque transmitted to the second wheel assembly are a target torque ratio.

[0039] When the control device determines that the transmission of the driving force from the second wheel assembly to the road surface is incomplete, it instructs the cutting-off mechanism to transmit the driving torque generated by the first power source to the transfer case.

[0040] The first wheel assembly and the second wheel assembly mentioned in Appendix 1 can be arranged front and rear along the direction of travel of the vehicle. For example, the first wheel assembly can be arranged in front of the direction of travel, and the second wheel assembly can be arranged in rear of the direction of travel.

[0041] In the embodiments described above, a front wheel assembly 23f is exemplified as the first wheel assembly, and a rear wheel assembly 23r is exemplified as the second wheel assembly. An engine 26 and a generator 25 are exemplified as the first power source. A generator 27 is exemplified as the second power source. The first and second power sources are not limited to the elements exemplified above, as long as they can generate driving torque.

[0042] According to Appendix 1, if the control device determines that the transmission of the driving force from the second wheel assembly to the road surface is incomplete, it instructs the cut-off mechanism to transmit the driving torque generated by the first power source to the transfer case. This allows for more appropriate control of the torque distribution to the front and rear wheels, thereby further improving vehicle stability.

[0043] In this embodiment, an example is given of the control device determining whether the transmission of the driving force from the second wheel device to the road surface is incomplete based on whether the absolute value of the difference between the front and rear wheel speeds exceeds a certain threshold. Figure 3 Step S02). The determination of whether the transmission of the driving force of the second wheel device to the road surface is incomplete is not limited to this.

[0044] For example, it can also be estimated based on the difference between the actual gradient of wheel speed and the estimated gradient of wheel speed that can be estimated from the applied torque. It can be determined that the greater the difference between the actual gradient and the estimated gradient, the greater the slip condition.

[0045] For example, the vehicle acceleration can also be estimated based on the difference between the estimated vehicle acceleration, calculated from the actual gradient of wheel speed, and the measurement value from the acceleration sensor installed on the vehicle. It can be determined that the greater the difference between the estimated and measured vehicle acceleration, the greater the slip condition.

[0046] For example, the transmittable driving force of the drive wheels can also be used to determine this. By using transmittable driving force as a criterion, the front wheel torque Tfr can be increased before excessive tire slippage occurs. This allows the output shaft to engage during periods of low rotational difference between the front and rear wheels, reducing engagement shock and achieving good driving performance.

[0047] The transmittable driving force can be calculated by estimating the road surface μ based on the tire slip. The road surface μ can be estimated based on the tire slip during travel, using the reference road surface μ as a reference, and the actual tire slip.

[0048] Symbol Explanation

[0049] 2-Drive system, 21-Control device, 22-Transfer transfer case, 23f-Front wheel assembly (first wheel assembly), 23r-Rear wheel assembly (second wheel assembly), 24-Transmission, 25-Motor generator (first power source), 26-Engine (first power source), 27-Motor generator (second power source).

Claims

1. A drive system, characterized in that, have: The first power source is provided in a vehicle having a first wheel assembly and a second wheel assembly arranged front to back along the direction of travel. A transfer case distributes the driving torque generated by the first power source to the first wheel assembly and the second wheel assembly through a fixed distribution ratio. A cutting-off mechanism that can transmit and cut off the drive torque generated by the first power source to the transfer case; The second power source is located between the transfer case and the second wheel assembly; and A control device controls the first power source and the second power source in such a way that the first driving torque transmitted to the first wheel assembly and the second driving torque transmitted to the second wheel assembly are a target torque ratio. When the control device determines that the transmission of the driving force from the second wheel device to the road surface is incomplete, it instructs the cutting-off mechanism to transmit the driving torque generated by the first power source to the transfer case.

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