JPH0794209B2 - Control device for four-wheel drive vehicle - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application) Control for controlling 4 / 2-wheel drive switching in a four-wheel drive vehicle that automatically switches from four-wheel drive to two-wheel drive when the vehicle speed exceeds a set vehicle speed value Regarding the device.

(Prior art) Conventionally, control of a four-wheel drive vehicle that switches to four-wheel drive immediately after starting or when traveling at low speed on a low μ road surface and automatically switches to two-wheel drive when traveling at a high speed above a set vehicle speed Various devices have been proposed (for example, JP-A-56-43031).

(Problems to be solved by the invention) However, when the set vehicle speed value for switching from four-wheel drive to two-wheel drive is constant, there is a risk of spinout accompanying acceleration on a low μ road surface. There is a risk that the vehicle will be switched to two-wheel drive, and on the other hand, even if the four-wheel drive is no longer needed on a high μ road surface, the four-wheel drive will continue without switching to two-wheel drive. This causes a decrease in fuel consumption and noise generation.

The present invention has been made to solve the problems in the control device that automatically switches from four-wheel drive to two-wheel drive by the vehicle speed control as described above.

(Means for Solving Problems) In order to achieve the above object, the present invention provides a four-wheel drive vehicle in which vehicle speed is automatically switched 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. , Road surface condition detecting 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 detecting means detects a high friction road surface, the reference vehicle speed value is set to a low speed value to reduce the friction. When the road surface is detected, the reference vehicle speed value setting means sets the reference vehicle speed value to a higher speed side than that of the high friction road surface.

(Operation) In the present invention, when the high friction road surface is detected by the road surface state detecting means, the reference vehicle speed value is set to the low speed side, and when the low friction road surface is detected, the reference vehicle speed value is higher than that of the high friction road surface. By setting to the high speed side and delaying the timing of switching to the two-wheel drive, it is possible to effectively prevent spinout on a low friction road surface, improve fuel efficiency on a high friction road surface, and prevent noise generation.

(Embodiment) The present invention will be described in more detail based on an embodiment shown in the drawings.

1 and 2 show a four-wheel drive switching device for performing 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 a clutch 3 Connected by.

Reference numeral 11 is an input shaft integrally connected to an output shaft (not shown) of the transmission, 12 is an input gear for a low speed stage, and 13 is an input gear for the low speed stage.
Is the input gear for the high speed stage, and the input shaft
11 is rotatably supported. Further, a synchronization device 14 is configured on the input shaft 11 to facilitate switching during traveling.

Reference numeral 15 is an idler gear, which includes an idler gear 15a that meshes with the input gear 12, and an idler gear 1 that meshes with the input gear 13.
5b is integrally formed and is rotatably supported on the idler shaft 16. An output gear 17 meshes with the idler gear 15b and is fixedly fitted to the output rear shaft 18. A rear 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). twenty three
Is a hydraulic clutch device, which transmits power to the output front shaft 25 when the hydraulic piston 24 is moved, and transmits power to the front tire 28 via the front flange 26, the propeller shaft 27, and a front differential (not shown). Reference numeral 29 denotes a rotation speed detection sensor of the output rear shaft 18.

FIG. 3 shows a hydraulic circuit for controlling engagement / disengagement of the hydraulic clutch 23 of the switching device, where 111 is a manual valve and the other end is formed integrally with the shift shaft 30 for operating the synchronizing device 14. The illustrated state is a high-speed shift state and the hydraulic pressure is maintained at a medium pressure. When the manual valve 111 moves leftward, a low speed shift state is set and the hydraulic pressure is switched to high pressure.

112 is a regulator valve, 113 is a modulator valve, 11
4 is a check valve. A change valve 115 is constituted by solenoid valves S1 and S2 and the manual valve 111.

Next, the operation of the hydraulic circuit will be described. The oil discharged from the oil pump 180 driven by the motor 150 fills the communicating oil passage to increase the pressure. Since the solenoid S2 is in the closed state, the pressure oil that has passed through the orifice 130 moves the spool 120 to the right to overcome the spring 125 and move (state shown in the figure), and the piston chamber 24 of the pressure oil clutch 23 is moved.
The clutch 23a is engaged by flowing into a and moving the piston 24 to the left. Further, the pressure regulation of the rise of the pressure oil is that the spool 121 is moved to the right by the pressure oil that has passed through the orifices 131 and 132, and the state (the state shown in the figure) that balances the load of the spring 122 is the set pressure regulation state, and the balance is lost. As the pressure rises, the spool 121 will be moved further to the right, but the pressure oil in the oil passage 170 will move to the pressure adjusting portion 121a.
When it flows to the oil drain passage 171 further, the hydraulic pressure will decrease,
The pressure oil is kept constant. The spool 123 of the modulator valve 113 in this state is pushed to the left by the spring 124. This is because the solenoid S1 is in the open state and the pressure oil that has passed through the orifice 133 flows into the oil discharge passage, so that the spring 124 cannot be overcome.

Next, in order to switch from the intermediate pressure state to the low pressure state shown in the figure, the solenoid S1 is switched from the open state to the closed state, whereby the spool 123 of the modulator valve 113 moves to the right and the oil passage
When the pressure oil in 172 flows out to the oil discharge passage 171, the pressure oil in the circuit is decompressed from the intermediate pressure and switched to a low pressure.

The above is the four-wheel drive state at the high speed stage, and the two-wheel drive state from this state can be achieved 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 discharged, so the pressure in the oil passage 135 decreases, and the load of the spring 125 causes the spool 120 to move to the left and close the oil passage 134. Since the oil passage that has engaged the hydraulic clutch 23a disappears, the clutch is disengaged and the four-wheel drive is switched to the two-wheel drive. By keeping the solenoid S1 in the two-wheel drive state closed, the pressure oil in the circuit is kept in a low pressure state by the modulator valve 113, so that the time lag when switching from two-wheel drive to four-wheel drive is shortened. be able to. In addition, because of the low pressure, the motor 150 that drives the oil pump 180 can be of low power, which consumes less power.

Next, when the hydraulic clutch requires high pressure (high transmission capacity is required), it is when the gear is changed to the low speed stage. In that case, the manual valve is moved to the left,
The pressure oil that has flowed into the orifice 131 is shut off, and the regulator valve 112 is pressure-controlled between the pressure oil that has passed through the orifice 132 and the spring 122, so that the high pressure is maintained. In this case, the solenoid S2 is closed only,
Four-wheel drive is always used.

Table 1 shows a matrix of shift speeds, hydraulic pressure states, and solenoid open / close states.

Next, the electronic circuit for controlling the hydraulic circuit configured as described above will be described with reference to FIG. 4. The battery 210 is connected to the ignition switch 211 and Vcc through the regulator section 259 and Vcc of the microcomputer 250. .
Output signals from various sensors are input to the input side of the microcomputer 250. The types of input sensors are, in order from the top, the front rotation sensor 29 'and the rear rotation sensor.
29, steering sensor 255, climbing plate sensor 230, and throttle sensor 231. From the top, the switches are a fixed mode switch 258, a transfer position manual switch 256, and a brake switch 257. Fixed mode switch 258 and H ₂ are 2WD, A ₄ is auto, H _S is differential 4WD, and H _L is lock 4WD, respectively. Rotation sensor 29 ′, 29
Outputs a frequency proportional to the number of revolutions induced in the coil as a pulse signal. The brake switch 257 is input to the microcomputer 250 via the level converter 251.

On the other hand, the output side of the microcomputer 250 is connected to various indicator lamps, solenoid valves, DC motors and buzzers. In other words, if you explain in order from the top, 253
Is a 4WD indicator light, 254 is a differential 4WD indicator light, S1 and S2 are solenoid valves, 213 is a DC motor, and
252 indicates a buzzer, respectively.

In the electronic circuit configured as described above, the microcomputer 250 internally edits and processes the input signal received from the uphill / downhill sensor and outputs it as a drive level to the output side 101-106. The output drive level is passed through the respective drive circuits, that is, the indicator lamp drive circuits 253a and 254a, the solenoid valve drive circuits S1a and S2a, the buzzer drive circuit 252a, and the DC motor drive circuit 213a in order from the top. , Input to each device and operate the device.

When there is no output to 103 and 104, solenoid valves S1, S
2 is closed, and when the solenoid drive level is output from the output side 103, the solenoid valve S1 is changed from closed to open. When it is output to 104, the solenoid valve
S2 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 reverse direction, and the engagement of the hub is released.

For switches, for example, H _{L of} fixed mode switch 258
When (Lock 4WD) is turned on, it is output to the output side 103 of the microcomputer 250 through the level converter 251.
There is no output to 104, and the solenoid valve S1 is energized and S2 is de-energized.

Next, two-wheel drive (2WD) and four-wheel drive (4WD) of the four-wheel drive vehicle control device by the microcomputer 250 of the above electronic circuit
The switching control will be described with reference to the flowcharts shown in FIGS.

In Fig. 5, initial setting (a) such as RAM clear check and flag setting is performed.
256 is automatically set. And level converter 251
After the manual switch 256 is read (b) and chattering is removed (c), the brake 257, the climbing plate sensor 230, the throttle sensor 231, the steering sensor 255,
The wheel rotation sensors 29, 29 'are read (d) and chattering is removed (e).

Next, the vehicle speed is calculated (f) to determine whether the vehicle is stopped (g), and if it is stopped, the vehicle stop flag is turned on (h), and the slip ratio η is 0 (i). ) To the parameter (PARM) and the parameter one generation before (BPAR
M) is set to 0, that is, "continuation of conventional control" (j). Then, the vehicle stop control (D) is performed after the on / off judgment (x) of the vehicle stop flag.

When the vehicle is not stopped, the tire angle β ₁ is calculated (k), and when β ₁ is 10 degrees or less, the theoretical rotation difference η ₂ due to steering of the front and rear wheels is 0 (m), That is, this η
₂ is ignored, and when β ₁ is 10 degrees or more, η ₂ is calculated (n) by η ₂ = 2 (1-cosβ ₁ ) / (1 + cosβ ₁ ).

Next, the actual rotation difference η ₁ between the front and rear wheels is calculated as η ₁ = 1- (NF1 / NR6) NF1: Front propeller shaft rotation speed NR6: Rear propeller shaft rotation speed (o), and the slip ratio η is η = | Η ₁ −η ₂ | + κ κ: Calculate (p) with a correction coefficient.

Next, as shown in FIG. 9, flags are set in correspondence with bits (0) to (7), and parameters (1,
2, 4, 8, 16) are assigned to represent each control content. Then, a parameter word is created (q). The correspondence relationship between the arithmetic sum of parameter values and the control contents of each flag represented by each parameter value (1,2,4,8,16) is as shown in Table 2.
That is, 1 (on), 0 (off) of each flag (corresponding bit)
There is a case in which each parameter stands, and an arithmetic sum of a predetermined combination of parameters is established depending on whether each flag is turned on or off, and each of the values corresponds to a value of 0 to 31 as shown in Table 2.

Parameter word creation (q) will be described with reference to the subroutine shown in FIG. Here, the explanation of the parameter (PARM) is shown in FIG. 9, and the control contents of each parameter value are shown in Table 2 below.

Further, FIG. 10 shows a parameter (BPARM) one generation before, where F in FIGS. 9 and 10 represents the meaning of the flag.

In FIG. 8, the tire (front wheel) angle β ₁ is compared (a) with the tire angle α ₁ (reference value) at the start of steering control, and α ₁
In the case of ≧ β ₁ , PARM = that the continuation of conventional control is included
Set to 0 (clear all flags) (B). When α ₁ <β _1, the vehicle speed (rear wheel rotation speed) NR is further compared with the vehicle speed (rear wheel rotation speed) NR3 (reference value) at the start of steering control (C).
If NR3 ≧ NR, PARM = 0 (clear all flags) (B). When NR3 <NR, PARM = 1 (bit (0) is turned on and 0 otherwise for steering control)
(OFF) and (FR3) are created (D).

Next, the vehicle speed NR is compared with the vehicle speed control start rotational speed NR5 (reference value) (e), when NR5 ≧ NR, α ₁ and β ₁ are directly compared (g), and when NR5 <NR, the vehicle speed control is performed. To
Set 1 (ON) to bit (1) of PARM. Create (FR5) and add (F). This is shown in FIG. 8 as PARM ∪
Write 2. (Hereinafter, the symbol ∪ means that the previous bit is not affected and 1 (on) is set only for that bit.) Then, α ₁ and β ₁ are compared (g) again, and α ₁ ≧ β ₁
Then, the slip ratio η ₁ and the slip ratio η _X (reference value) at the start of the slip control are compared (re) as they are, and when α ₁ <β ₁ , the PARM bit (2 ) Is set to 1 (on), the flag Fα is turned on, and then η ₁ and η _X are compared (re).

When η ₂ ≤ η _X, the brake switch 25
On / off judgment (7) of 7 is performed, and when η ₁ > η _X , ₁ is set to bit (3) of PARM containing slip control.
After the flag Fη is turned on and the flag Fη is turned on and added (nu), it is determined whether the brake switch 257 is on or off (ru).

When the brake switch 257 is off, the slip control flag (BF
η) is turned on (wa), and if the brake switch 257 is turned on, the brake control is the content P
After 1 (on) is set to the bit (4) of ARM to add (wo) the flag Fα, it is determined (wa) whether or not the flag (BFη) is on.

When the flag (BFη) one generation before is off, the current parameter (PARM) is immediately replaced with the parameter (BPARM) one generation ago, and when the flag (BFη) is on, the current parameter (PARM) is next. ), The steering control flag (F
Judge whether α) is on or not.

If the flag (Fα) is off, the current parameter (PARM) is immediately replaced with the parameter (BPARM) one generation before, as described above, and if the flag (Fα) is on, the current parameter (PARM) is next. In the steering control flag (FR
3) Determine whether or not is on.

When the flag (FR3) is off, the current parameter (PARM) is immediately replaced with the parameter (BPARM) (as in the above).
However, when the flag (FR3) is on, the flag (Fη) is turned on (re) and the parameter (PARM) is replaced with the parameter (BPARM) regardless of what the previous state was.

When the parameter word creation (q) is completed as described above,
In FIG. 1, it is judged (r) whether or not the downhill sensor 230b is turned on. When the downhill sensor 230b is on, the downhill flag is turned on (v), and when the downhill sensor 230b is off, the elapsed timer after the downhill sensor is turned off.
It is determined (s) whether T1 has started. If T1 has started, then compare (u) with T1 and the His timer T_T1 during the next control after turning off the downhill sensor. If T1 has not started, start T1. After (t), T1 and T_T1 are compared (u).

When T_T1> T1, the downhill flag is turned off and T1 is cleared (w), and when T_T1≤T1, the downhill flag is turned on (v ').

Then, determine whether the vehicle stop flag is on or off (x)
If the vehicle stop flag is on, the process proceeds to vehicle stop control (D), and in FIG. 6, the on / off judgment (F) of the slope sensor 230a is performed.
NR is compared with the reference vehicle speed value NR2 (G), and when NR2> NR, the vehicle moves to downhill control (C), and in Fig. 7, the solenoid valve S1 is turned on and S2 is turned off to directly drive four-wheel drive ( L / C4W
Switch to (D) (L) and return to in the flowchart. Also N
When R2 ≤ NR, the process moves to Fig. 7 to search for a parameter (I).

When the uphill sensor 230a is off, the downhill flag is judged to be on / off (H). When it is on, the downhill control (C) is performed and the direct-coupled four-wheel drive (L) is performed as described above. / C4WD) (L) When the downhill flag is off, the process moves to FIG. 7 to search for a parameter (I).

When the vehicle stop flag is off, it is next determined whether the uphill sensor 230a is on or off (y). Climbing sensor 230a
When is turned on, the vehicle moves to the uphill control (E), and in FIG. 6, the vehicle speed NR is compared with the reference vehicle speed value NR2 (G) as described above, and if NR2> NR, the downhill control ( C), turn on solenoid valve S1 and turn off S2, switch to direct drive four-wheel drive (L / C4WD) (L), and return to the flowchart.

If the uphill sensor 230a is off, it is next judged whether the downhill flag is on or off (z), and if the downhill flag is on, the process goes to downhill control (C). After switching (L) to direct drive four-wheel drive (L / C4WD), return to in the flowchart. If the downhill flag is off, the parameter (PA
RM) search (I).

In the search (I) of the parameter (PARM), when the parameter is (0, 1, 4), the process returns to the flowchart again and starts from the program of manual switch reading (b).

When the parameter is (8 to 12,14,24 to 28,30), it is judged whether or not it is a rapid throttle based on the throttle opening depressed within a certain time (J), and in the case of a rapid throttle (for example within 50 msec) When more than 2 steps are taken), move to downhill control (C), turn on solenoid valve S1 and turn off solenoid valve S2, and drive directly connected four-wheel drive (L / C4WD)
Switch to (L) and return to in the flowchart.

When the throttle is not sudden throttle, the vehicle speed control speed NR5 (reference value) is set to a higher vehicle speed control speed NR6 (NR5 <NR
After changing (K) to 6), turn on solenoid valve S1 and turn on S2
Turn off and switch to direct drive four-wheel drive (L / C4WD) (L),
Return to in the flow chart.

When the parameter is (2,3,5 to 7,21,23), the solenoid valve S1 is turned off and S2 is turned on to switch to the two-wheel drive (2WD) (M), and the process returns to the flowchart.

When the parameter is (13, 15, 29, 31), the solenoid valve S1 is turned off and S2 is turned off to switch to the differential four-wheel drive (N), and then the process returns to the flowchart.

When the parameter is (16 to 20, 22), the solenoid valve S1 is turned on and S2 is turned off to switch to the direct drive four-wheel drive (L / C4WD) and return to (L).

Note that FIG. 11 is a flowchart showing a subroutine of a timer interrupt of the microcomputer, but the explanation of the timer interrupt means is omitted because this timer interrupt means is normally performed.

The above is an example of the switching control between 2WD and 4WD by the microcomputer 250. Control for changing the vehicle speed set value between the low μ road surface and the high μ road surface when switching from 4WD to 2WD by the vehicle speed control Will be described in more detail based on the conceptual diagram of FIG. 12 in which other controls of FIG. 12 are omitted.

In FIG. 12, after performing vehicle speed lead and throttle lead (d), chattering removal (e), vehicle speed calculation (f) and slip ratio calculation (p), the slip ratio η ₁ is the slip ratio at the start of slip control (reference Value) η _X (N), and when the slip ratio is smaller than the reference value, that is, when the road surface is high μ, the current vehicle speed NR is compared with the vehicle speed control start rotation speed NR5 (Q). To do.

4 when NR is smaller than NR5, that is, when the coefficient of friction is high (slip ratio <reference value) and the vehicle speed is low (vehicle speed <reference value).
When the NR is larger than NR5, the solenoid valve S1 of the hydraulic circuit is turned off and S2 is turned on to drive the vehicle in two wheels (M).

When the slip ratio is larger than the reference value, that is, when the road surface has a low μ, it is determined whether or not the throttle is next sharp (J).
However, when the throttle is abrupt, the solenoid valve S1 is turned on and S2 is turned off to set the drive to direct drive four-wheel drive (L),
Reference value NR5 for starting vehicle speed control if the throttle is not sudden
To a reference value NR6 higher than this (K).

Then, the current vehicle speed NR and the changed reference value NR6 are compared (Q), and if smaller than NR6, the solenoid valve S1
Is turned on, S2 is turned off, and the drive remains in the direct-coupled four-wheel drive state (L). When NR becomes larger than NR6, solenoid valve S1 is turned off and S2 is turned on to switch to two-wheel drive ( M).

As described above, the vehicle speed control start rotation speed (set vehicle speed value) for switching the drive to the two-wheel drive is set to the high speed side on a low μ road surface to ensure driving safety, and to the low speed side on a high μ road surface. You can set it to improve fuel efficiency and prevent noise.

Note that the vehicle speed control start rotation speed may be switched automatically by a rainfall sensor instead of detecting slip, that is, determining whether the road surface is a low or high μ road surface.

(Advantages of the Invention) As described above, the present invention is a part-time four-wheel drive vehicle that automatically switches to two-wheel drive when the vehicle speed becomes equal to or higher than the set vehicle speed by controlling the vehicle speed control start speed (set vehicle speed) on a low friction road surface. Value) is set to the high speed side, and even if the vehicle side goes up, four-wheel drive is continued more than on the high friction road surface, so stable running can be secured, and vehicle speed control starts on the high friction road surface. The rotation speed (set vehicle speed value) is set to a low speed side, and switching to two-wheel drive due to an increase in vehicle speed is performed faster than on a low friction road surface, so it is possible to improve fuel efficiency and prevent noise generation Is.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a four-wheel drive switching mechanism which is switch-controlled by a control device according to the present invention.
FIG. 3 is a sectional view showing a hydraulic clutch device of the same switching mechanism,
FIG. 4 is a hydraulic circuit diagram of the same switching mechanism, FIG. 4 is an electronic circuit diagram of the same switching mechanism, and FIGS. 5 to 8 are flow charts showing an embodiment of four-wheel drive switching control according to the present invention.
FIG. 11 is a diagram showing parameters in the same embodiment, FIG. 11 is a subroutine showing a timer interrupt in the same embodiment, and FIG.
The drawing is a schematic view 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 …… Micro Computer, 255 ... Steering sensor.

Front page continuation (56) References JP 59-184026 (JP, A) JP 59-160630 (JP, A) Actual opening 61-41035 (JP, U) Actual opening 59-154426 (JP , U)

Claims (1)

[Claims] 1. 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 and detects whether the road surface is a high-friction road surface or a low-friction road surface. And a road surface condition detecting means for setting the reference vehicle speed value to a low speed side when the road surface condition detecting means detects the high friction road surface, and sets the reference vehicle speed value to the high value when detecting the low friction road surface. A control device for a four-wheel drive vehicle, comprising: a reference vehicle speed value setting means that is set at a speed higher than that of a frictional road surface.