JPS6311441A - Control device for four wheel drive vehicle - Google Patents

Abstract

PURPOSE:To continue a four-wheel driving condition even when a vehicle speed is increased and ensure stable traveling by setting vehicle speed control starting number of revolutions to a high speed side on a low friction road surface, in the captioned vehicle which is automatically shifted to two-wheel driving when a vehicle speed becomes above a set value by a vehicle speed control. CONSTITUTION:The captioned control device controls solenoids S1, S2 based on the output signals of front and rear rotation sensors 29', 29, a steering sensor 255, etc., thereby, shifting a transfer device to direct coupled four-wheel driving, differentially movable four-wheel driving, or two-wheel driving. In this case, it is detected whether a road surface is a high friction road surface or a low friction road surface based on a slip ratio which is operated from a defined formula. And, a reference vehicle speed value at the time of automatically shifting from a four-wheel driving to a two-wheel driving in accordance with a vehicle speed, is set to a low speed side at the time of high friction road surface, whereas, setting to a high speed side at the time of low friction road surface. Thereby, a four-wheel driving is continued on a low friction road surface even when the vehicle speed is increased, maintaining stable traveling.

Description

[Detailed Description of the Invention] (Industrial Application Field) In a four-wheel drive vehicle that automatically switches from four-wheel drive to two-wheel drive when the width exceeds a set vehicle speed value, the set vehicle speed value for switching this drive is reduced. The present invention relates to a control device that sets the speed to the high speed side on a friction road surface (low μ road surface) and to the low speed side when on a high friction road surface (high μ road surface).

(Prior art) Conventionally, four-wheel drive vehicles switch to four-wheel drive immediately after starting or when driving at low speeds on low-μ roads, and automatically switch to two-wheel drive when driving at high speeds exceeding a set vehicle speed. Various control devices have been proposed (for example, Japanese Patent Laid-Open No. 56-4303
No. 1).

(Problem to be solved by the invention) However, if the set vehicle speed value for switching from four-wheel drive to two-wheel drive is constant, there is a risk of spin-out with acceleration on low μ road surfaces. There is a risk that the vehicle will switch to two-wheel drive regardless of the road surface, and conversely, even if four-wheel drive is no longer necessary on a high μ road surface, the switch to two-wheel drive may not occur and four-wheel drive may continue. This causes a decrease in fuel efficiency and noise generation.

The present invention was made in order to solve the problems in a control device that automatically switches from four-wheel drive to two-wheel drive through vehicle speed control as described above.

(Means for Solving the Problems) In order to achieve the objective of -1-1, the present invention automatically switches from four-wheel drive to two-wheel drive when the vehicle speed becomes equal to or higher than a reference vehicle speed value by vehicle speed control. In four-wheel drive vehicles,
road surface condition detection means for detecting whether the road surface is a high friction road surface or a low friction road surface; and when the road surface condition detection means detects a high friction road surface, the reference vehicle speed value is set to the low speed side, and a reference vehicle speed value setting means for setting the reference vehicle speed value to a higher speed than in the case of a high-friction road surface when detecting this.

(Function) 1] - Note: In this invention, when a high friction road surface is detected by the road surface condition detection means, the reference vehicle speed value is set to the low speed side, and when a low friction road surface is detected, the reference vehicle speed value is set to the low speed side. The timing of switching to two-wheel drive is delayed by setting the vehicle to a higher speed than usual, effectively preventing spin-outs on low-friction roads, improving fuel efficiency and preventing noise generation on high-friction roads. be done.

(Example) This invention will be described in more detail below based on an example shown in nine drawings.

1 and 2 show a four-wheel drive switching device that performs switching control by a control device according to the present invention, in which 1 is an engine, 2 is a transmission, and the engine 1 and the transmission 2 are
and are connected by a clutch 3.

11 is an input shaft that is integrally coupled with an output shaft (not shown) of the transmission, 12 is an input gear for a low gear, and 13 is an input gear for a high gear, which are rotatably supported by the input shaft 11. A synchronizer 14 is also provided on the input shaft 11 to facilitate switching while the vehicle is running.

Reference numeral 15 denotes an idler gear, in which an idler gear 15a that meshes with the input gear 12 and an idler gear 15b that meshes with the input gear 13 are integrally formed, and are rotatably supported on the idler shaft 16. Reference numeral 17 denotes an output gear, which meshes with the idler gear 15b and is fixedly fitted with the output rear shaft 18. A lever flange 20 is fixedly fitted to a spline 19 of the output rear shaft 18, and power is transmitted to a rear tire 22 via a propeller shaft 21 and a differential (not shown).

23 is a hydraulic clutch device, and when the hydraulic piston 24 is moved, power is transmitted to the output front shaft 25, and the front flange 26. Power is transmitted to front tires 28 via a propeller shaft 27 and a front differential (not shown). 29 is a rotational speed detection sensor for the output rear shaft 18.

FIG. 3 shows a hydraulic circuit for controlling engagement and disengagement of the hydraulic clutch 23 of the switching device.

111 is a manual valve, the other end of which is integrally formed with the shift shaft 30 that operates the synchronizer 14;
The illustrated state is a high-speed shift state in which the oil pressure is maintained at medium pressure. When the manual valve 111 moves to the left, a low speed shift state is entered and the oil pressure is switched to a high pressure.

112 is a regulator valve, 113 is a modulator valve, and 114 is a check valve.

Reference numeral 115 denotes a change valve, which is composed of solenoid valves S1 and S2 and the manual valve 111.

Next, to explain the operation of the hydraulic circuit described in -1-, the motor 15
The oil discharged from the oil pump 180 driven by the oil pump 180 fills the communicating oil passage, and the pressure increases. Since solenoid S2 is in the closed state, orifice 130
The passed pressure oil moves the spool 120 to the right by overcoming the spring 125 (as shown in the figure), flows into the piston chamber 24a of the pressure oil clutch 23, moves the piston 24 to the left, and moves the clutch 120 to the left. 23a.

In addition, to regulate the rising pressure of the pressure oil, the spool 121 is moved to the right by the pressure oil passing through the orifices 131 and 132, and the state in which it is balanced with the load of the spring 122 (the state shown in the figure) is the preset pressure regulation state. As the pressure increases due to collapse of the spool 121, the spool 121 is moved further to the right.

When the pressure oil in the oil passage 170 flows from the pressure regulating part 121a to the oil drain passage 171, the oil pressure will decrease.

Pressure oil is kept constant. Note that the spool 123 of the modulator valve 113 in this state.

It is in a state where it is pushed leftward by the spring 124.

This is because when the solenoid S1 is in an open state, the pressure oil that has passed through the orifice 133 flows into the oil drain path and cannot overcome the force of the spring 124.

Next, in order to switch from the medium pressure state shown in the figure to the low pressure state, by switching the solenoid S1 from the open state to the closed state, the spool 123 of the modulator valve 113 moves to the right, and the pressure oil in the oil passage 172 is transferred to the drain passage. 171, the pressure oil in one circuit is reduced from medium pressure and switched to low pressure.

The above is the four-wheel drive state in the high speed gear, and changing from this state to the two-wheel drive state is possible by changing the solenoid S2 from the closed state to the open state. When the solenoid S2 is opened, the pressure oil that has passed through the orifice 130 is drained, so the pressure in the oil passage 135 drops and the spring 12
The spool 120 moves to the left due to the load of
34 is closed, and the oil passage that was engaging the hydraulic clutch 23a disappears, so the clutch is disengaged and the system becomes two-wheel drive rather than four-wheel drive. Solenoid S1 in the two-wheel drive state is
By keeping it in the closed state, the pressure oil in the nine circuits is maintained at a low pressure state by the modulator valve 113, so the time lag when switching from two-wheel drive to four-wheel drive can be shortened. In addition, since the pressure is low, the motor 150 that drives the oil pump 180 requires low power, resulting in low power consumption.

Next, when the hydraulic clutch requires high pressure (high transmission capacity is required), it is when the gear is changed to a low gear, but in that case, the manual valve is moved to the left, so
The pressure oil flowing into the orifice 131 is shut off, and the pressure of the regulator valve 112 is regulated between the pressure oil that has passed through the orifice 132 and the spring 122, so that a high pressure is maintained. In this case, the solenoid S2 is only in the closed state, so that four-wheel drive is always performed.

Table 1 shows a matrix of gears, hydraulic conditions, and opening/closing states of solenoids.

Table 1 Next, the electric circuit for controlling the hydraulic circuit configured as above will be explained based on Fig. 4.Batch-〇-81
- The microcomputer 210 is connected to the ignition switch 211 and VCC via the regulator section 259.
50 Vcc. Output signals from various sensor forces are input to the input side of the microcomputer 250. The types of input sensors are, from top to bottom, front rotation sensor 29', rear rotation sensor 29. Steering sensor 255. These are a climbing plate sensor 23o and a throttle sensor 231. Switches start from ]2.

Fixed mode switch 258. ) Transfer position manual switch 256. This is the brake switch 257. Fixed mode switch 258 H2 is 2WD, A4 is auto, Hs is differential 4WD, and H is lock 4WD.
are shown respectively. The rotation sensors 29', 29 output a frequency proportional to the number of rotations induced in the coil as a pulse signal. Brake switch 257 is input to microcomputer 250 via level converter 251.

On the other hand, the output side of the microcomputer 250 includes various indicator lamps and solenoid valves.

Connected to DC motor and buzzer. Namely.

To explain from top to bottom, 253 is a 4WD indicator lamp, 254 is a differential 4WD indicator lamp, Sl
, S2 is a solenoid valve, 213 is a DC motor, and 252 is a buzzer.

In the electronic circuit configured as described above, the microcomputer 250 receives input signals from the climbing board sensor and others.
edits and processes the data internally, and outputs it to the output sides 101 to 106 as a drive level. The output drive level is
Indicator lamp drive circuits 253a and 254a, in order from -1-, respectively,
Solenoid valve drive circuits Sla and S2a,
Buzzer drive circuit 252a and DC motor drive circuit 2
13a, and is input to each device to operate the device.

When there is no output to 103 and 104, solenoid valve 81. S2 is in the closed state, and when the solenoid drive level is output from the output side 103, the solenoid valve S1 changes from closed to open.

Also, when output to 104, solenoid valve S
2 goes from closed to open. When the solenoid valve S2 is energized, the drive level output to 106 causes the freewheel hub drive motor 213 to rotate in the opposite direction, thereby disengaging the hub.

For switches, for example, when the fixed mode switch 258 HL (Lock 4WD) is turned on.

It passes through the level converter 251 and is output to the output side 103 of the microcomputer 250, but not to the output side 104, and the solenoid valve S1 is energized and the solenoid valve S2 is energized.

Next, the microcomputer 250 of the electronic circuit controls the two-wheel drive (2WD) and four-wheel drive (
4WD) switching control.

The explanation will be given based on the flowcharts shown in FIGS. 5 to 8.

In FIG. 5, initial settings (a) such as RAM clear check and flag setting are performed, and at this time the manual switch 256 is set to automatic. And reading Jf of manual switch 256 in level converter 251
fs(b).

After chattering removal (C), the brake 257,
Climbing board sensor 230. Throttle sensor 231, steering sensor 255. The wheel rotation sensors 29, 29' are read (d) and chattering is removed (e).

Next, calculate the vehicle speed (f) and determine whether the vehicle is stopped (g). If the vehicle is stopped, turn on the vehicle stop 1 flag (h), and at this time the slip rate η is 0. (i
), the parameter (P'ARM) and the parameter (BPARM) of the -generation before are set to 0, that is, "continuation of conventional control" (j). After determining whether the vehicle stop flag is on or off (X), the process proceeds to vehicle stop control (D).

If the vehicle is not stopped, calculate the tire angle β1 (
k), and if β1 is less than 10 degrees, the theoretical rotational difference η due to steering of the front and rear wheels is calculated as O(m), that is, this η
2 is ignored, and if β1 is 10 degrees, η2 is expressed as r)2=2 (1-cosβI)/(
1+cosβl).

Next, calculate the actual rotational difference η1 between the front and rear wheels as η! ÷1- (NFI/NR6) NFI: Front propeller shaft rotation speed NR6: Calculated using rear propeller shaft rotation speed (o)L, and slip rate η as η-1η
−η21+: Calculate (p) using the correction coefficient.

Next, as shown in Figure 9, each flag is set corresponding to bits (0) to (7), and the parameter (
1, 2, 4, 8, 16) to represent each control content. Then, create a parameter word (q). Arithmetic sum of parameter values and each parameter value (1, 2, 4, 8, 1
The correspondence relationship between each flag represented by 6) and the control contents is as shown in Table 2. That is, each flag (corresponding bit)
Each parameter is set corresponding to 1 (on) or 0 (off), and the arithmetic sum of the predetermined combination of parameters is established depending on whether each flag is on or off, and the value of θ to 31 is established as shown in Table 2. There are cases in which each corresponds to .

Parameter word creation (q) will be explained using the subroutine shown in FIG. Here, an explanation of the parameters (PARM) is shown in FIG. 9, and the control contents of each parameter value are shown in Table 2 below.

(Left below) FIG. 10 shows the parameters (B P A RM ) of one generation ago, and in FIGS. 9 and 10, F represents the meaning of a flag.

In Fig. 8, the tire (front wheel) angle βl is compared with the tire angle α1 (reference value) at the start of steering control.
If ≧β1, the PA whose content is to continue the conventional control
Set RM=0 (all flags cleared) (mouth). Also α
In the case of β1, further compare the vehicle speed (rear wheel rotation speed) NR with the medium speed (rear wheel rotation speed) NR3 (reference value) at the start of steering control I5n (c) L, if NR3≧NR The PAR
Set M=0 (all flags cleared) (mouth). And N.R.
If 3<NR, PARM= whose content is steering control
1 (only bit (0) is turned on and the others are O (off)) (FR3) is created (2).

Next, compare the vehicle speed NR with the vehicle speed control starting rotation speed NR5 (reference value) (E) L. If NR5≧NR, directly compare α1 and β1 (G), and if NR5<NR, set the vehicle speed control as the content. Set PARM pin 1-(1) to 1 (on). Create and add (FR5). 8th
In the figure, this is indicated as PARMtJ2. (Hereinafter, the U symbol will not affect the previous bit and will only set the corresponding bit.
(on) means to stand up. ) Then compare α and β1 again (g).

When α1≧β1, the next step is to compare the slip ratio ηI and the slip ratio ηX (reference value) at the start of slip control, and when α1 minus β1, bit (2) of PARM containing steering control is performed. is set to 1 (on), and after turning on the flag Fα, η1 and η are compared.

When ηl≦η8, the brake switch 2 is
Make 57 on/off decisions (ru).

When β1>β8, PAR includes slip control
Bit (3) of M is set to 1 (on), flag Fη is turned on and added (nu), and then it is determined whether the brake switch 257 is on or off.

- If the brake switch 257 is off, the slip control flag (
Determine whether or not BF4) is on, and if the brake switch 257 is on, set bit (4) of PARM containing brake control to 1 (on) and add flag Fα as on. After (wo), flag (BF)
4) Determine whether or not it is on.

When the previous generation flag (BF4) is off, the current parameter (PARM) is immediately changed to - the previous generation parameter (BP).
When the flag (BF4) is on, it is next determined whether or not the steering control flag (Fα) is on in the current parameter (PARM).
do.

When the flag (Fα) is off, the current parameter (PARM) is immediately changed to the previous generation parameter (BPA) as described above.
When the flag (Fα) is on, it is then determined whether or not the steering control flag (FR3) is on in the current parameter (PARM).

When the flag (FR3) is off, the current parameter (PARM) is immediately replaced with the parameter -18- (BPARM) as described above, and when the flag (FR3) is on, the previous state is changed. Regardless of whether the flag (Fη) is on or off, the parameter (PA
RM) with the parameter (BPARM).

When the parameter word creation (Q) is completed as described in (2) below, it is determined (r) whether or not the drop sensor 230b is off in FIG. If the drop-off sensor 230b is on, then the drop-off flag is turned on (V), and if the drop-off sensor 230b is off, it is determined whether the elapsed timer T1 after the drop-off sensor is turned off has started (
s) do. If T1 has started, then a comparison (U) is made with the histimer T Tl during the transition to control after T1 and the exit sensor are turned off, and if TI has not started, T1 is started ( t) After T1 and T
Compare (u) with Tl.

T If Tl>TI, turn off the withdrawal flag and T
1 is cleared (w)L, and when TTI≦T1, the withdrawal flag is turned on (v').

Then, vehicle stop 1 - determine whether the flag is on or off (x
) L, vehicle stop 1 - If the flag is on, move to vehicle stop side gtI (D), in FIG.

Determine whether the pitching sensor 230a is on or off (F),
If it is on, then the vehicle speed NR is compared with the reference vehicle speed value NR2 (G), and when NR2>NR, the step-down control (C) is performed.
7, turn on the solenoid valve S1,
Turn off S2, switch to direct four-wheel drive (L/C4WD) (L), and return to ■ in the flowchart. Also, NR2≦N
When it is R, the process moves to (2) in FIG. 7 and the parameter search (1) is performed.

Furthermore, if the climbing sensor 230a is off, the next step is to determine whether the climbing flag is on or off (I(), and if it is on, the stepping down control (C) is performed in the same manner as described above, and the direct connection four-wheel drive (L/
(C4WD) (L) If the withdrawal flag is off, the process moves to (2) in FIG. 7 and a parameter search (I) is performed.

If the vehicle stop flag is off, it is determined whether the uphill sensor 230a is on or off (y). If the climbing sensor 230a is on, the process moves to climbing control (E), and in FIG. 6, the vehicle speed NR is compared with the reference vehicle speed value NR2 (G) L, and if NR2>NR, the climbing control is performed. Move to control (C), turn on solenoid valve S1, turn off S2, and switch to direct four-wheel drive (L/C4WD) (L
), return to ■ in the flowchart.

If the boarding sensor 230a is off, then it is determined whether the boarding flag is on or off (2), and if the boarding flag is on, the process moves to boarding control (C), and the direct connection four is activated as described above. After switching to wheel drive (L/C4WD) (L), return to step (2) in the flowchart. If the withdrawal flag is off, the parameter (PARM) is searched (I).

In parameter (PARM) search (1).

When the parameters are (0, 1, 4), the process returns to step (2) in the flowchart and starts from the manual switch reading program (b).

When the parameter is (8~12, 14, 24~28°30), it is determined whether the throttle is sharp or not based on the throttle opening degree depressed within a certain period of time (
J) L, in the case of sudden throttle (for example, when more than 2 steps are stepped within 50m5ec), the drop-off control (C
), turn on the solenoid valve S1, turn off the solenoid valve S2, switch to direct four-wheel drive (L/C4WD) (L), and return to step (2) in the flowchart.

If the throttle is not sudden, the vehicle speed control rotation speed NR5 (
The vehicle speed control rotation speed NR6 (NR
After changing (K) to 5<NR6), solenoid valve S
1 on, S2 off, direct four-wheel drive (L/C4W)
Switch to D) (L) and return to ■ in the flowchart.

When the parameters are (2, 3, 5 to 7.21.23), the solenoid valve S1 is turned off.

Turn on S2 and switch to two-wheel drive (2WD) (M),
Return to ■ in the flowchart.

When the parameters are (13, 15, 29, 31), the solenoid valve S1 is turned off and the solenoid valve S2 is turned off to switch to differential four-wheel drive (N), and then return to step (2) in the flowchart.

When the parameter is (16 to 20.22).

Turn on solenoid valve S1 and turn off S2 to switch to direct four-wheel drive (L/C4WD) and return to (L) ■.

It should be noted that FIG. 11 is a flowchart showing a subroutine for a timer interrupt of the microcomputer, and since this timer interrupt means is commonly used, a description thereof will be omitted.

The above is 2WD and 4W by microcomputer 250.
This shows an example of the switching control with D, but when switching from 4WD to 2WD by vehicle speed control, the control to change the vehicle speed setting value between low μ road surface and high μ road surface is performed using other control shown in FIG. A more detailed explanation will be given based on the conceptual diagram of FIG. 12, in which .

In Fig. 12, after performing vehicle speed read and throttle read (d), chattering removal (e), vehicle speed = 1 calculation (f), and slip ratio calculation (p), the slip ratio ηl is determined as the slip ratio at the start of slip control ( Compare (N)L with reference value) η. If the slip ratio
Compare (Q) with

If NR is smaller than NR5, return to the start and N
If R is larger than NR5, the solenoid valve S1 of the hydraulic circuit is turned off, S2 is turned on, and the drive is set to two-wheel drive (M).

If the slip rate is larger than the reference value, that is, on a low μ road surface, then it is determined whether or not the throttle is to be applied suddenly (J).
L, solenoid valve S1 in case of sudden throttle
Turn on, turn S2 off and set the drive to direct four-wheel drive.L
), if the throttle is not sudden, the reference value NR5 for starting vehicle speed control is changed to a higher reference value NR6 (K).

Then, compare the current vehicle speed NR and the changed reference value NR6 (Q). If it is smaller than NR6, turn on solenoid valve S1 and turn off S2 to leave the drive in direct four-wheel drive mode. ).

When NR becomes larger than NR6, solenoid valve S1 is turned off and solenoid valve S2 is turned on to switch to two-wheel drive (M).

As shown in 2 below, the vehicle speed control starting rotation speed (set vehicle speed value) for switching the drive to two-wheel drive is set to the high speed side on low μ road surfaces to ensure driving safety; In this case, set it to the low speed side for better fuel efficiency! −, Noise generation can be prevented.

Note that the switching of the vehicle speed control starting rotation speed may be automatically performed by a rain sensor rather than by detecting slip, that is, determining whether the road surface is a low μ road surface or a high μ road surface.

(Effects of the Invention) As described above, the present invention provides a part-time four-wheel drive vehicle that automatically switches to two-wheel drive when the vehicle speed exceeds a set vehicle speed by vehicle speed control. value) is set on the high-speed side, and even if the vehicle speed increases, four-wheel drive continues more than on high-friction roads, ensuring stable driving, and vehicle speed control starts on high-friction roads. The rotation speed (set vehicle speed value) is set to the low speed side, and the vehicle speed is lower than that on a low-friction road surface.

Since the switch to two-wheel drive is performed quickly when the vehicle lifts up, it is possible to improve fuel efficiency and prevent noise generation.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of a four-wheel drive switching mechanism controlled by a control device according to the present invention;
The figure is a sectional view showing the hydraulic clutch device of the same switching mechanism.
FIG. 4 is a hydraulic circuit diagram of the switching mechanism, FIG. 4 is an electronic circuit diagram of the switching mechanism, FIGS. 5 to 8 are flowcharts showing an embodiment of four-wheel drive switching control according to the present invention, and FIGS.
0 is a diagram showing parameters in the same embodiment, and FIG. 11 is a subroutine showing a timer interrupt in the same embodiment.
FIG. 12 is a schematic diagram showing another embodiment of the present invention. 18...Output rear shaft. 23...Hydraulic clutch. 24...Hydraulic piston. 25...Output front shaft. 29...Rear rotation speed detection sensor. 29'...Front rotation speed detection sensor. 250...Microcomputer. 255...Steering sensor.

Claims (1)

[Claims] In a four-wheel drive vehicle that automatically switches from four-wheel drive to two-wheel drive when the vehicle speed exceeds a reference vehicle speed value by vehicle speed control, a road surface condition detection means detects whether the road surface is a high-friction road surface or a low-friction road surface. When the road surface condition detecting means detects a high friction road surface, the reference vehicle speed value is set to a lower speed side, and when a low friction road surface is detected, the reference vehicle speed value is set to a higher speed side than in the case of a high friction road surface. 1. A control device for a four-wheel drive vehicle, comprising reference vehicle speed value setting means.