JP2659017B2 - Vehicle driving force distribution control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a driving force distribution control device for a vehicle that controls front and rear wheels of a four-wheel drive vehicle to an optimum driving force distribution ratio according to a traveling state or the like.

(Prior Art) Conventionally, a driving force distribution control device for a torque split type four-wheel drive vehicle is described in, for example, "Car Graphic September Issue" (issued in September 1987), pp. 100-102. Something like that is known.

According to this conventional source, start control is performed to increase the clutch engagement force and increase the amount of torque transmitted to the rear wheels as the accelerator opening increases in order to prevent drive slip during sudden start at extremely low speeds. A control is described in which, when the vehicle speed reaches a predetermined value, the control shifts from the accelerator opening control to the slip control based on the front and rear wheel rotation ratio and the rotation difference zero control.

(Problems to be Solved by the Invention) However, in such a conventional driving force distribution control device, a control in which the switching from the accelerator opening degree control to the front / rear wheel rotation ratio corresponding control is performed only according to the vehicle speed condition. Therefore, if the accelerator pedal is depressed too much when starting and all four wheels spin, it is determined that the vehicle is running at a high speed even though the absolute vehicle speed on the road surface is low, and the accelerator opening The corresponding control is terminated and the control is shifted to the front / rear wheel rotation ratio corresponding control. With the shift, the driving force distribution is instantaneously switched from the four-wheel drive to the two-wheel drive, and the vehicle behavior becomes unstable. There is a problem that performance is inferior.

Since the vehicle speed information of an automobile is generally obtained from detection signals from a transmission output shaft rotation sensor, a wheel speed sensor, and the like, the propeller shaft and wheels rotate at a high speed regardless of the absolute vehicle speed (body speed). If so, a signal indicating a high vehicle speed is output. When all four wheels idle, it is considered that the front and rear wheel rotation speed difference is zero, that is, the front and rear wheel rotation ratio is 1, despite the occurrence of drive slip.

The present invention has been made in view of the above-described problems, and has been made to prevent the instability of the vehicle behavior at the time of sudden start and the reduction of the drive performance at the time of sudden start while securing the effect of improving the drive performance at the time of slow start. Development of a driving force distribution control device for motor vehicles.

(Means for Solving the Problems) In order to solve the above problems, the present invention also provides a vehicular driving force distribution control device as shown in the claim correspondence diagram of FIG.
A clutch b that is mounted in a transfer that distributes the driving force of the rotary drive source a to the front and rear wheels, and that can continuously change the fastening force between the front wheel side and the rear wheel side of the transfer; Front and rear wheel rotation speed difference control means c for controlling the engagement force of the clutch b based on the wheel rotation speed difference, and accelerator opening degree control means d for controlling the engagement force of the clutch b depending on the degree of accelerator opening; When the vehicle speed exceeds a predetermined vehicle speed, the accelerator opening control is performed.When the vehicle speed exceeds the predetermined vehicle speed, the control is switched to the front and rear wheel rotational speed difference control, and when the control is switched from the accelerator opening control to the front and rear wheel rotational speed difference control, the driving wheel slips. And control mode switching means e for holding the accelerator opening degree control until drive wheel slip is suppressed.

(Operation) When the vehicle speed is equal to or lower than the predetermined vehicle speed, the control mode switching means e selects the accelerator opening corresponding control mode, and the accelerator opening corresponding control means d engages the clutch b based on the magnitude of the accelerator opening. The force is controlled.

When the vehicle speed exceeds the predetermined vehicle speed, the control mode switching means e immediately switches from the accelerator opening degree control mode to the front and rear wheel rotation speed difference control mode by the control mode switching means e on condition that the driving wheel is not in a slip state. The engagement force of the clutch b is controlled by the speed difference corresponding control means c based on the difference between the front wheel rotation speed and the rear wheel rotation speed.

Therefore, at the time of slow start while slowly depressing the accelerator pedal, the driving force distribution is changed to the four-wheel drive side in accordance with the accelerator opening, so that there is no response delay and the drive wheel slip is suppressed. Later, when the vehicle speed exceeds a predetermined vehicle speed while driving while keeping the accelerator operation amount small, the driving force distribution is changed and controlled while monitoring the difference between the front and rear wheel rotational speeds, thereby suppressing the occurrence of excessive drive wheel slip Is done.

Further, even when the vehicle speed is higher than the predetermined vehicle speed, even when the vehicle speed is in the driving wheel slip state, the control mode switching means e maintains the accelerator opening degree control until the driving wheel slip is controlled. Is suppressed, the control mode is switched from the accelerator opening control mode to the front and rear wheel rotational speed difference control mode.

Therefore, at the time of a sudden start in which all of the four wheels idle due to excessive depression of the accelerator pedal, even if it is determined that the vehicle speed is higher than the predetermined vehicle speed, the control mode transition waits until the wheel idle, which is a drive wheel slip, is suppressed. The instantaneous switching from the four-wheel drive to the two-wheel drive drive force distribution prevents instability in vehicle behavior and occurrence of excessive drive wheel slip.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

In describing this embodiment, a driving force distribution control device for a four-wheel drive vehicle based on rear wheel drive will be described as an example.

 First, the configuration will be described.

As shown in FIG. 2, the drive system of the four-wheel drive vehicle to which the driving force distribution control device of the embodiment is applied includes an engine 1, a transmission 2, a transfer input shaft 3, a transfer clutch device A, a rear propeller shaft 4, The vehicle includes a rear differential 5, a rear wheel 6, a transfer output shaft 7, a front propeller shaft 8, a front differential 9, and a front wheel 10. The engine driving force passing through the transmission 2 is directly transmitted to the rear wheel 6, and the front wheel 10 Is transmitted through a transfer clutch device A provided between the transfer input / output shafts 3 and 7.

The control hydraulic pressure Pc is provided outside the transfer clutch device A based on predetermined input information and control contents.
Hydraulic control device as clutch engagement force control means that creates
20 are provided.

The hydraulic control device 20 includes a motor 22 that is driven or stopped by a relief switch 21, a hydraulic pump 24 that is operated by the motor 22 and draws up from a reservoir tank 23, and a pump discharge pressure (primary pressure) from the hydraulic pump 24. An accumulator 26 that is stored via a check valve 25, and an electromagnetic proportional pressure valve 28 that adjusts a line pressure (secondary pressure) from the accumulator 26 to a predetermined control oil pressure Pc by a control current i from a control unit 27, It is supplied to the control hydraulic port 30 through the control hydraulic valve 29.

The control unit 27 has an electronic control circuit configuration, and is connected to a front wheel rotation speed sensor 31, a rear wheel rotation speed sensor 32, an accelerator opening sensor 33, a longitudinal acceleration sensor 34, a lateral acceleration sensor 35, and the like as information input sensors. The detection signals nf, nr, [theta] _a , Yg, Xg from these sensors 31 to 35 are input, and a control current i for obtaining an optimum front / rear wheel driving force distribution ratio according to a vehicle running state or the like is output.

As shown in FIG. 3, the transfer clutch device A includes a multi-plate friction clutch 60 which is engaged by a hydraulic mechanism 40 operated by a control hydraulic pressure Pc from an external hydraulic control device 20,
A lubricating oil 15 for cooling the clutch provided in the transfer input shaft 3 and in the transfer case 11 and the case cover 12.
To remove the lubricating oil 15 inside the multi-plate friction clutch 60.
And a lubrication pump 70 that guides the

The pressing mechanism 40 of the multi-plate friction clutch 60 includes a cylinder block 41, a piston chamber 42, a piston 43, a piston rod 44, a swing plate 45, a swing pin 46, a fixed pressure plate 47, a bearing 48, and a rotary pressure plate. 49, a pressure block 50, and a return spring 51 are provided.

The multi-plate friction clutch 60 includes a clutch drum 61 that is spline-coupled to the transfer input shaft 3, a drive plate 62 that is spline-fitted to the clutch drum 61,
A driven plate 63 sandwiched between the drive plates 62, and the driven plate 63 is spline-fitted,
Needle bearing 64 for transfer input shaft 3
And a clutch hub 65 rotatably supported by the clutch hub 65.

The clutch hub 65 is provided with a first sprocket 66
The drive torque is transmitted to the transfer output shaft 7 via the chain 67 and the second sprocket 68.

The lubricating pump 70 is of a trochoid pump type provided in a pump housing 71 and a pump cover 72 at the inlet of the transfer input shaft 3, and has a suction port 73.
Communicates with a suction tube 75 having a suction port 74, and its discharge port 76 is connected to a radial oil passage 77, an axial oil passage 78, a radial oil passage 79, and a clutch hub 65 formed on the transfer input shaft 3. The lubricating oil 15 for cooling the clutch in the transfer case 11 is drawn up to communicate with the formed oil holes 80 and 81, the lubricating oil 15 is guided to the multi-plate friction clutch 60, and discharged from the oil hole 82.

The transfer output shaft 7 and the chain 67 to the front wheel 10 provided offset from the transfer input shaft 3 are immersed in the clutch cooling lubricating oil 15 stored in the lower portion of the transfer case 11, Lubrication pump
70 inlets 74 are arranged.

In FIG. 3, 90 is a joint flange, 91, 92, 93 are seals, and 94, 95, 96, 97, 98 are bearings.

 Next, the operation will be described.

First, the flow of the driving force distribution control operation performed by the control unit 27 will be described with reference to the flowchart shown in FIG.

In step 100, the front wheel rotation number nf is the detection signal, the rear wheel rotation speed nr, accelerator opening theta _a, lateral acceleration Yg, the longitudinal acceleration Xg read.

In step 101, the front wheel rotational speed Nf and the rear wheel rotational speed Nr is determined by computation by the loaded wheel rotational speed nf and the rear wheel rotational speed nr and tire radius at step 100, the absolute vehicle speed V _t by the longitudinal acceleration Xg It is obtained by calculation.

The absolute vehicle speed V _t can be obtained by the following formula for integrating the longitudinal acceleration Xg.

However, the initial value of V _t is zero.

In step 102, the front and rear wheel rotation speed difference ΔN is calculated based on the front wheel rotation speed Nf and the rear wheel rotation speed Nr obtained in step 101.
(= Nr-Nf) is calculated.

In step 103, the vehicle speed V _W is calculated by the calculation formula by the front wheel rotational speed Nf and the rear wheel rotational speed Nr calculated in step 101.

In _{V W = K · (Nf +} Nr) / 2 Step 104, the absolute vehicle speed V _t is whether a predetermined absolute vehicle speed V _t 'less is determined.

In step 105, a predetermined value accelerator opening theta _a is theta _a '
It is determined whether or not this is the case.

Then, when V _t ≦ V _t ′ and θ _a ≧ θ _a ′,
Proceeding to step 106, the accelerator opening correspondence control is selected.

Further, _{'a, θ a <θ a' V} t ≦ V t when the proceeds rear wheel rotational speed difference corresponding control to step 107 is selected.

In step 108, it is determined whether the lateral acceleration Yg is equal to or greater than a predetermined value Yg '.

In step 109, whether the vehicle speed V _W exceeds the absolute vehicle speed V _t is determined.

Then, _{'a, Yg ≧ Yg' V t>} V t when the proceeds rear wheel rotational speed difference corresponding control to step 107 is selected.

Further, _{'a, Yg <Yg' V t>} V t when and V _t <V _W is an accelerator opening degree corresponding control proceeds to step 106 is selected.

Further, _{'a, Yg <Yg' V t>} V t when and V _t ≧ V _W proceeds rear wheel rotational speed difference corresponding control to step 107 is selected.

Next, the driving force distribution control operation will be described separately for a slow start and a sudden start.

(B) a time slow start while gradually depresses slowly slow start when the accelerator pedal, the absolute vehicle speed V _t is less than the predetermined absolute vehicle speed V _t ',
And on the conditions accelerator opening theta _a is a predetermined value theta _{a 'above,} is selected accelerator opening corresponding control mode, as shown in FIG. 6, the front wheel-side transmission in accordance with the increase in the accelerator opening theta _a Control is performed to increase the torque Tf so that the drive distribution is set to the four-wheel drive side.

That is, the driving force distribution in accordance with the accelerator opening theta _a is generated prediction information of the drive wheel slip by being changed to four-wheel drive side, there is no response delay drive wheel slip is suppressed.

Then, 'by weight, lateral acceleration Yg predetermined value Yg' absolute vehicle speed V _t after the start of a predetermined absolute vehicle speed V _t in a time substantially straight running below, the vehicle speed V _W is not less drive wheel slip state absolute vehicle speed V _t Under the condition, the control mode is immediately switched from the control mode corresponding to the accelerator opening to the control mode corresponding to the front and rear wheel rotation speed difference, and as shown in FIG. 5, the front wheel side transmission torque Tf is increased in accordance with the increase in the front and rear wheel rotation speed difference ΔN. Is controlled such that the drive distribution is increased to the four-wheel drive side.

That is, while monitoring the front and rear wheel rotation speed difference ΔN, the driving force distribution is changed and controlled to suppress the increase in the front and rear wheel rotation speed difference ΔN, thereby suppressing the occurrence of excessive driving wheel slip.

Therefore, when the vehicle slowly starts, the drive wheel slip is effectively suppressed from immediately after the vehicle starts until the vehicle travels at a constant speed, so that the vehicle can start and travel while maximizing drive performance.

Further, in the front-rear wheel rotational speed difference control mode, as shown in FIG. 5, by increasing the front-wheel-side transmission torque Tf as the lateral acceleration Yg is smaller, it is possible to achieve both driving performance and turning performance.

(B) at the time of sudden acceleration to idle four wheels both too depressing the sudden acceleration when the accelerator pedal and are identified as the absolute vehicle speed V _t exceeds a predetermined absolute vehicle speed V _t ', the vehicle speed V _W absolute vehicle speed V in step 109
_As long as the driving wheel step state exceeds _t , the control mode corresponding to the accelerator opening is held, and the transition from the control mode corresponding to the accelerator opening to the control mode corresponding to the front and rear wheel rotational speed difference is caused by wheel slippage, which is a driving wheel slip. Wait until suppressed.

Therefore, at the time of a sudden start, it is possible to avoid instantaneously switching from the four-wheel drive to the rear-wheel drive drive power distribution by shifting the control mode only under the vehicle speed condition as in the prior art. It is possible to prevent a decrease in drive performance caused by allowing excessive drive wheel slip as it is.

Hereinafter, the embodiment has been described with reference to the drawings. However, the specific configuration is not limited to this embodiment, and even if there is a change or addition of control content without departing from the gist of the present invention, the present invention is not limited to this embodiment. Included in the invention.

For example, in the embodiment, an example of application to a four-wheel drive vehicle based on a rear wheel drive has been described, but it is needless to say that the invention can be applied to a four-wheel drive vehicle based on a front wheel drive.

(Effects of the Invention) As described above, in the vehicle driving force distribution control device according to the present invention, the accelerator opening degree control is performed at a predetermined vehicle speed or lower, and the front and rear wheel rotational speed difference control is performed at a predetermined vehicle speed. When switching to the control, and when switching from the accelerator opening control to the front and rear wheel rotational speed difference control, if the driving wheel is in a slip state, a control mode switching means for holding the accelerator opening control until the driving wheel slip is suppressed is provided. With this arrangement, it is possible to obtain an effect that it is possible to prevent the instability of the vehicle behavior at the time of a sudden start and the reduction of the drive performance while securing the effect of improving the drive performance at the time of slow start.

[Brief description of the drawings]

FIG. 1 is a claim correspondence diagram of a vehicle driving force distribution control device of the present invention, FIG. 2 is a diagram showing a driving system and a control system of a four-wheel drive vehicle to which the driving force distribution control device of the embodiment is applied, Third
FIG. 4 is a cross-sectional view showing a transfer clutch device used in the embodiment device. FIG. 4 is a flowchart showing a flow of a driving force distribution control operation in a control unit of the embodiment device. FIG. 6 shows a control map in the control mode in the control mode. a ... Rotary drive source b ... Clutch c ... Control means corresponding to front and rear wheel rotational speed difference d ... Control means corresponding to accelerator opening degree e ... Control mode switching means

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-61829 (JP, A) JP-A-62-191225 (JP, A) JP-A-63-61635 (JP, A) JP-A-63-61835 106138 (JP, A) JP-A-62-12422 (JP, A) JP-A-63-96937 (JP, U)

Claims (1)

(57) [Claims] 1. A clutch mounted in a transfer for distributing a driving force of a rotary drive source to front and rear wheels and capable of continuously changing a fastening force between a front wheel side and a rear wheel side of the transfer; A front-rear wheel rotation speed difference control means for controlling the clutch engagement force based on a difference between the speed and the rear wheel rotation speed; an access opening degree control means for controlling the clutch engagement force depending on the degree of accelerator opening; When the vehicle speed is lower than the vehicle speed, the accelerator opening control is performed, and when the vehicle speed exceeds a predetermined vehicle speed, the control is switched to the front and rear wheel rotational speed difference control. A driving mode distribution control device for a vehicle, comprising: a control mode switching means for holding the accelerator opening degree control until the driving wheel slip is suppressed.