JPH0331012A - Device for controlling suspension system - Google Patents

Abstract

PURPOSE:To improve stability of vehicle behaviour by changing suspension controlling characteristics to that adequate for a running road in the case where the road had low frictional coefficient, and by changing the suspension controlling characteristics to other characteristics in the case where output of decision for low frictional coefficient can not be obtained within a required duration. CONSTITUTION:In a deciding means 24c of a suspension system control device ECU24, a frictional coefficient of a road surface is decided on the basis of slipping behaviour of a wheel within specified duration according to an information of a wheel speed from a sensor 20, otherwise on the basis of an operating time or an operating frequency of a throttle valve control device ECU23 and an anti-skid brake control device ECU25. According to output from the deciding means 24c, a first suspension system control means 24a is selected, which changes characteristics of a suspension system 13 to that adequate for a low friction road. After that, if there is no output signal of a decision for low frictional coefficient within operating time of a timer T1, a second suspension system control means 24b is selected, which changes characteristics of the suspension system 13 to other control characteristics, i. e., an usual control specification.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a suspension control device for a vehicle that switches control characteristics of a suspension according to environmental conditions outside the vehicle, particularly the state of the coefficient of friction of the road surface on which the vehicle is traveling.

[Background Art] In recent years, many suspensions of vehicles, especially automobiles, use electronic control, and the control content is becoming more sophisticated year by year.

Conventional vehicle suspension control devices detect vehicle driving conditions such as the steering angle of the steering wheel, vehicle speed, and whether or not the brake pedal is being operated, and increase or decrease the damping force of the shock absorber depending on these detection signals. The system performs control such as switching to suppress rolling and pitching of the vehicle.

[Problems to be Solved by the Invention] However, in the conventional vehicle suspension control device as described above, even if the road surface is prone to slipping and has a low coefficient of friction (low μ road), the driver cannot manually Unless the suspension is adjusted using There is a problem in that the danger of the tuck-in phenomenon leading to spin cannot be avoided.

The present invention aims to solve the above-mentioned problems, and enables suspension control according to the state of the friction coefficient of the road surface on which the vehicle is running, thereby achieving excellent straight-line stability even on road surfaces with a low friction coefficient and suppressing the tendency to tuck-in. The purpose of the present invention is to provide a vehicle suspension control device that can perform the following functions.

[Means for Solving the Problems] Therefore, the vehicle suspension control device of the present invention (!
#Claim) is equipped with a suspension that is interposed between the wheels and the vehicle body and whose control characteristics can be switched in at least two stages, and determines that the road surface on which it is running has a low friction coefficient and outputs an output to that effect. a first suspension control means that receives the determination output from the determination means and controls the suspension to switch control characteristics suitable for a road surface with a low coefficient of friction; A timer that operates while switching to a control characteristic suitable for the condition, and a control characteristic that makes the suspension suitable for a road surface condition with a low coefficient of friction when there is no judgment output from the judgment means within the operating period of the timer. The present invention is characterized in that a second suspension control means for switching control to another control characteristic is provided.

Further, the vehicle suspension control device (claim 2) of the present invention is provided with a suspension that is interposed between a wheel and a vehicle body and whose control characteristics can be switched to at least two stages, and the vehicle travels on a road surface with a low coefficient of friction. and a first suspension control that receives the determination output from the determination means and switches the suspension to a control characteristic suitable for a road surface condition with a low coefficient of friction. means, a vehicle body acceleration detecting means for detecting vehicle body acceleration, and a vehicle body acceleration detected by the vehicle body acceleration detecting means exceeding a set value while the suspension is switched to a control characteristic suitable for a road surface condition with a low coefficient of friction; The present invention is characterized in that a second suspension control means is provided for controlling the suspension by switching the control characteristic to a control characteristic different from a control characteristic suitable for a road surface condition with a low coefficient of friction.

[Function] In the above-described vehicle suspension control device of the present invention (claim 1), when the first determination means determines that the traveling road surface has a low coefficient of friction, the first suspension control means controls the suspension. The control characteristics are switched to low sag control characteristics when the road surface has a low coefficient of friction. When the switching control is performed in this way, the timer is activated, and if there is no judgment output from the judgment means within the operation period, the second suspension control means controls the suspension control characteristics to be suitable for the road surface condition with a low coefficient of friction. Control is performed by switching from one control characteristic to another control characteristic.

Furthermore, the above-mentioned vehicle suspension control device of the present invention (
In claim 2), similarly, by the determining means.

When it is determined that the road surface on which the vehicle is traveling is in a road surface condition with a low coefficient of friction, the first suspension control means switches control characteristics of the suspension to a road surface condition with a low coefficient of friction and a low sag control characteristic. When the vehicle body acceleration detected by the vehicle body acceleration detecting means exceeds the set value in this switching controlled state, the second suspension control means changes the suspension control characteristics to a control suitable for a road surface condition with a low coefficient of friction. Control is performed by switching from one control characteristic to another control characteristic.

[Embodiment] Below, a vehicle suspension control device as an embodiment of the present invention will be explained with reference to the drawings. Fig. 1 is a control block diagram thereof, and Fig. 2 shows its engine system, suspension system, brake system, and control system. Overall configuration diagram showing the system, parts 3 to 5
Each of the figures is a flow chart for explaining an example of a control procedure for switching the suspension from a normal specification to a low μ road specification, and each of Figures 6 to 8 is a control procedure for switching the suspension from a low μ road specification to a normal specification. Flowcharts for explaining examples, FIGS. 9 and 10 (a).

11(b) and FIGS. 11(a) and 11(b) are block diagrams showing examples of information communication states within the control system.

Now, the engine system in this embodiment is as shown in FIG. 2. In this FIG. 2, the engine E has an intake passage 2 and an exhaust passage 3 that communicate with its combustion chamber 1.
In the intake passage 2, an air cleaner (not shown), an air flow sensor 4. A throttle valve 5 and an electromagnetic fuel injection valve (electromagnetic valve) 6 are provided, and an exhaust passage 3
A catalytic converter (three-way catalyst) and a muffler (silencer) (not shown) for purifying exhaust gas are provided in order from the upstream side. In addition, a spark plug 7 is provided in the combustion chamber 1, and a bypass passage 8 that bypasses the throttle valve 5 is provided in the throttle valve 5 portion of the intake passage 2. A bypass valve 9 is provided.

Note that the number of solenoid valves 6 corresponding to the number of cylinders is provided in the intake manifold portion. Also, throttle valve 5. The opening degrees of the bypass valves 9 are adjusted by motors to and 11, respectively. In particular, the opening of the throttle valve 5 is adjusted by a so-called throttle-by-wire method in which the throttle valve 5 is driven by an amount corresponding to the amount of depression of the accelerator pedal 28 by a motor 10 that receives a throttle drive command.

With this configuration, the air taken in through the air cleaner according to the opening degree of the throttle valve 5 is mixed with the fuel from the solenoid valve 6 in the intake manifold part to an appropriate air-fuel ratio, and the spark plug is heated in the combustion chamber 1. 7 is ignited at an appropriate timing.1 After being combusted and generating engine torque, the mixture is discharged as exhaust gas to the exhaust passage 3, and the catalytic converter converts Co,
After the three harmful components of HC and NOX are purified, the sound is muffled by a muffler and released into the atmosphere.

Furthermore, in this embodiment, as shown in FIG.
is attached to a vehicle body (not shown) via a suspension 13. Each suspension 13 has an air spring 14 and a shock absorber 15, and the spring constant and damping force are adjusted by air pumps 16 and 17, respectively.
The control characteristics can be switched in at least two stages. In this example, the two-stage control characteristics are a normal specification for road conditions with a high friction coefficient (high μ road) and a low μ road specification (suitable for road conditions with a low friction coefficient (low μ road)). Both the spring 14 and the absorber 15 are set in advance to be soft.

Furthermore, each wheel 12 is equipped with a brake (braking mechanism) 18 driven by a pump 19 and a sensor 20 for detecting wheel speed, and the vehicle body is equipped with a G sensor for detecting vehicle acceleration. (Vehicle body acceleration detection means) 2
1 is provided.

Engine system and suspension system as mentioned above.

In order to control the brake system, in this embodiment, the engine control ECU 22. Throttle valve control ECU2
3. Suspension control ECU 24° anti-skid brake ECU 25. An A/T JinECU 26 and a master control ECU 27 are provided.

Here, the master control ECU 27 controls each ECU to be described later.
22 to 26, accelerator opening information from the accelerator pedal 28, shift position information from the shift lever 29, and steering angle information from the steering wheel 30.

Based on various other sensor information (vehicle acceleration information, wheel speed information, etc.), appropriate commands are sent to each of the ECUs 22 to 26.

The engine control ECU 22 is based on the intake air amount information from the air flow sensor 4 that detects the intake air amount from the Karman vortex information, the rotation speed information of the engine E, etc.
Fuel amount increase/decrease command from 27.

The opening degree of the bypass valve 9 according to the ignition timing change command.

It controls the increase/decrease in the amount of fuel injected from the solenoid valve 6 and the advance/retard of the ignition timing of the two spark plugs 7.

The throttle valve control ECU 23 sends a throttle drive command to the motor 10 based on a throttle opening command from the ECU 27 according to the amount of depression of the accelerator pedal 28.
This motor 10 controls the opening degree of the throttle valve 5, but also has another function as a driving force control means (so-called traction control). That is, the throttle valve control ECU (sometimes referred to as traction control ECU) 23 controls the driving force of the wheels 12 by adjusting the output of the engine E by the opening degree of the throttle valve 5 according to the condition of the road surface. It also has a function that works to suppress idling (slip). Here, the condition of the running road surface is detected by information from various sensors (not shown), etc., and is detected by the ECtJ2 via the ECU 27 or directly.
3.

The suspension control ECU 24 normally uses the G sensor 21
In response to vehicle body acceleration (posture) information from the sensor 20, wheel speed information from the sensor 20, and damping force/spring force change commands from the ECU 27, the suspension 13 is sent via the air pumps 16 and 17.
In this embodiment, this suspension control ECU 24 has the functions of a first suspension control means 24a and a second suspension control means 24b, which will be described later. are doing.

The anti-skid brake EC1J25 receives a brake oil pressure change command from the ECU 27 and controls the increase/decrease of the brake oil pressure via the pump 19.It controls the braking force of the brake 18 according to the condition of the road surface, and adjusts the braking force during braking. It functions as a braking force control means that operates to suppress skidding of the wheels 12.

The A/T control ECU 26 controls an automatic transmission mechanism (A/T; not shown) mounted on the vehicle, and receives shift lever position information from a shift lever 29.

Shift control is executed by a shift stage change command from the ECU 27.

Next, the features of this device will be explained in detail with reference to FIG. Incidentally, in FIG. 1, the same reference numerals as those already described indicate the same parts, so the explanation thereof will be omitted.

In FIG. 1, reference numeral 24c denotes a determination means provided in the suspension control ECU 24 to determine the friction coefficient μ of the running road surface. It determines μ, and when it determines that the road surface on which it is traveling has a low coefficient of friction (hereinafter referred to as a low μ road), it outputs an output to that effect. In addition, in this embodiment, the wheels are idling (
A throttle valve control ECU (traffic ball control ECU) 23 that can suppress wheel slippage and an anti-skid brake control ECU that suppresses wheel skidding during braking.
25, the determining means 24c determines the friction coefficient μ based on the operating time or operating frequency of the throttle valve control ECU 23 or the operating time or operating frequency of the anti-skid brake control ECU 25 within a continuous predetermined period. It is also possible to determine.

Here, when determining the friction coefficient μ in the slip state of the wheel 12, the wheel speed information (drive shaft pulse, driven wheel pulse) is directly received from the sensor 20 as shown in FIG. As shown in Figure (a) and Figure 11 (a), the ECU
23.25, the friction coefficient is determined in accordance with the procedure described later with reference to FIG. 1 based on the operating time or operating frequency of the throttle valve control ECU 23.
When determining the f friction coefficient, as shown in FIG. 10(a), traction control information from the ECU 23 or
As shown in FIG. 10(b), information on the lighting of the traction control activation lamp 23a is received, and the friction coefficient is determined according to the procedure described later in FIG. 4. Furthermore, when determining the friction coefficient based on the operating time or operating frequency of the anti-skid brake ECU 25, as shown in FIG.
ABS operation information from CU25 or Fig. 11 (
As shown in b), upon receiving the lighting information of the ABS operation lamp 25a, the friction coefficient is determined according to the procedure described later in FIG.

In addition, in this example, the switching of the spring constant and damping force after it is determined that the road is low has inherent differences depending on the capabilities of the system (type of actuator, number of switching stages, 1 front and rear wheel independent control). Here, as a simple system, by turning a solenoid (not shown) 0N10FF by the first suspension control means 24a, the front and rear spring constants and damping forces can be simultaneously switched between low μ road specification and normal specification. Indicates what is done.

On the other hand, in FIG. 1, reference numeral 24a designates first suspension control means 24b for switching and controlling the suspension 13 to a control characteristic suitable for a low μ road, that is, a preset low μ road specification in response to the determination output from the determination means 24C. is a second suspension control means that switches and controls the suspension 13 from the low-μ road specification to another control characteristic, that is, the normal specification, in accordance with the operation of one of timers T1 to T3, which will be described later.

Here, each of the timers T1 to T3 makes a determination to cancel the low μ road specification state of the suspension 13 and switch to the normal specification, and outputs a switching command to the second suspension control means 24b. The procedure for determining whether to cancel or switch when using T1 to T3 follows the flow described later in FIGS. 6 to 8, respectively.

Note that the timer T1 operates when the suspension 13 is switched to the low μ road specification, and if there is no low μ road determination output from the determining means 24c within the operating period, the timer T1 outputs a signal to the second suspension control means 24b. This outputs a command to switch to normal specifications. Furthermore, the timer T2 operates when the suspension 13 is switched to the low μ road specification and the vehicle body acceleration detected by the G sensor 21 exceeds a set value. If the vehicle acceleration remains above the set value,
It outputs a switching command to the normal specification to the second suspension control means 24b.

Further, the timer T3 has almost the same function as the timer T1, and when the number of slips occurring within its operating period is below a certain value, it issues a command to the second suspension control means 24b to switch to the normal specification. This is what is output.

Since the vehicle suspension control device as an embodiment of the present invention is configured as described above, the friction coefficient determination, switching to the low μ road specification, and cancellation determination of the low μ road specification 2 are carried out as follows. Switching to the specifications is performed.

The friction coefficient determination and the switching to the low μ road specification are performed according to any of the procedures shown in FIGS. 3 to 5.

In this example, basically, according to the procedure shown in FIG.
The friction coefficient μ of the road surface is determined when the wheels 12 are in a slip state. In other words, if a slip rate equal to or higher than the determination value is detected a predetermined number of times within a predetermined time set by a slip determination timer (not shown) in the determination means 24c, the friction coefficient μ of the road surface is low. It is determined that this is the case, and the switching control to the low μ road specification is performed.

To explain in detail with reference to FIG. 3, first, the determining means 24c
In step Al), the driving wheel speed A and the driven wheel speed vN are calculated in response to the driving wheel pulse and the driven wheel pulse from the sensor 20. From these values, the slip ratio α is determined as V.
A/V) is calculated as 4 (step A2),
Then, it is determined whether or not the calculated slip rate α exceeds the determination value (step A3), and if it exceeds the determination value, a slip number counter (not shown, provided in the determination means 24c) is incremented. After that (step A, 1), it is determined whether the number of slips in the counter exceeds a determination value (step A5). If the number of slips exceeds the determination value, it is determined that the friction coefficient μ of the running road surface is low, and the determination means 24c sends a switching command to the first suspension control means 24a to set the suspension 13 to a low friction coefficient μ. Switching control is performed to the road specifications (step A6). After this switching control, or after it is determined in step A5 that the number of slips does not exceed the determination value, a slip determination timer that sets a predetermined time for slip determination is added (step A7), and this slip determination timer is kept constant. Step A8)
, when the predetermined value is reached, the slip determination timer and the slip count counter are cleared (step A9).

Note that the friction coefficient determination based on slip as described above is the same whether or not a control system (traction control, anti-skid brake) for reducing the slip of the wheels 12 is provided as in this embodiment. However, especially when equipped with the above control system, there is almost no slippage, so
The determination value of the slip ratio α in step A3 needs to be set much smaller than in the case where the above control system is provided.

In addition, in the judgment procedure shown in Fig. 3, there is only one judgment value for the slip rate α and one judgment value for the number of slips, but by providing multiple judgment values, it is possible to simply judge whether or not it is a low μ road. Not only that, but also extremely low μ such as snow and ice
It is now possible to distinguish between roads and low-μ roads with relatively high grip, such as rain or dirt (gravel), and it is also possible to adjust the suspension control characteristics accordingly in more detail than with two levels. Become.

Further, in the case of a front-wheel drive vehicle, the sensor 20 is provided at least one front wheel and two rear wheels to obtain a drive shaft pulse and a driven wheel pulse. Regarding the two rear wheel sensors 2o, data is taken from the inner wheel of the two rear wheels when cornering, and data is the average value of the two sensors 20 when the vehicle is traveling straight.

Also, as mentioned above, the low-μ road specifications.

Both the spring 14 and the absorber 15 are set to be soft,
Especially on snowy roads, the springs 14 in the front and rear suspensions 13. In addition to softening all of the absorbers 15, if the road is rainy, only the spring 14 of the rear wheel suspension 13 may be softened, or other controls depending on the weather may be performed.

By the way, as mentioned above, the system of this embodiment is equipped with a traction control system and an anti-skid brake system (ABS), and even if these systems are used, it is difficult to determine the friction coefficient.

It is possible to switch to a low μ road specification.

The traction control system operates to reduce the drive output force to suppress slipping of the wheels 12 when the road surface is low and the wheels 12 slip. Therefore,
When determining the friction coefficient μ of the running road surface using the traction control system, the driving export force is reduced within a predetermined time set by an output reduction determination timer (not shown) in the determination means 24c. When this control operation is detected a certain number of times (or for a certain period of time) or more, it is determined that the friction coefficient μ of the road surface is low, and control is performed to switch to the low μ road specification.

To explain in detail with reference to FIG. 4, first, the second determination means 24c
In step Bl), it is determined whether or not the information that the driving export force is being reduced is received as shown in Figures 1o (a) and (b). After adding up a medium counter (not shown; provided in the determination means 24c) (step B2), it is determined whether the count value of the counter has reached the determination value (step B3). When the count value reaches the judgment value, it is determined that the friction coefficient μ of the road surface is low,
From the determination means 24c to the first suspension control means 24a
A switching command is sent to the suspension 13 to control the suspension 13 to be switched to the low μ road specification (step B4).

After this switching control or after it is determined in step B3 that the count value has not reached the determination value, an output reduction determination timer is added to set a predetermined time for determining output reduction in step B5). It is determined whether or not the timer has reached a certain value (predetermined time) (step B6), and if the timer has reached the certain value.

The output reduction determination timer and the output reduction counter are cleared (step B7).

On the other hand, the anti-skid brake system operates to reduce braking force (braking force) to suppress skidding of the wheels 12 during braking due to a low μ road surface. Therefore, when determining the friction coefficient μ of the traveling road surface using the anti-skid brake system, the output reduction determination timer (
If a control operation to reduce the braking force is detected more than a certain number of times (or time) within a predetermined time set in Controls switching to road specifications.

To explain in detail with reference to FIG. 5, first, the determination means 24c, as shown in FIG.
Step C1)
, during the drive output power reduction, after adding up the output reduction counter (step C2), it is determined whether the count value of the counter has reached the determination value (step C3).
. When the count value reaches the determination value, it is determined that the friction coefficient μ of the road surface is low, and the determination means 24c sends a switching command to the first suspension control means 24a to set the suspension 13 to a low friction coefficient μ. After the switching control to the road specification (step C4) or after it is determined in step C3 that the count value has not reached the judgment value, a predetermined time for determining that the output is being reduced is set. A determination timer is added (step C5), a determination is made as to whether or not this determination timer has reached a certain value (predetermined time), step C6), and if the determination timer has reached a certain value, an output reduction determination timer and an output Clear the counter (step C7).

Note that in the determination procedure shown in FIGS. 4 and 5, there is one determination value for each number of output reduction operations, but by providing multiple values, the magnitude of the friction coefficient μ of the running road surface can be determined in detail. Adjust the suspension control characteristics accordingly.
It also becomes possible to make more fine-grained adjustments as needed than in stages.

In addition, in the determination procedure shown in Figures 4 and 5, the friction coefficient is determined only based on the presence or absence of an operation that limits (reduces) the drive export force or braking force, but through communication, the friction coefficient μ of the road surface is determined. The suspension specifications may be changed based on the information on the amount of control and the information on the amount of control operation.

Now, after the suspension 13 has been switched to the low-μ road specification as described above, the cancellation determination 9 of the low-μ road specification is switched to the normal specification by any one of the procedures shown in FIGS.

In this embodiment, basically, the low μ road specification/normal specification is switched using the timer T1 according to the procedure shown in FIG. That is, as shown in FIG. 6, it is determined in step Di) whether or not the current suspension control is set to low μ road specifications, and if it is not set to low μ road specifications, the determination means 24C makes a determination. Based on the output, it is determined whether the friction coefficient μ of the road surface is currently determined to be low (step D2). In this step D2, the friction coefficient μ
If it is determined that the coefficient is low, the first suspension control means 24a switches the 0N10 FF of the solenoid to control the suspension 13 to the low μ road specification (Step D3; the procedure up to this point is shown in Figs. 3 to 5 above). (This is similar to the determination procedure described by ). After this switching control,
Alternatively, after determining in step D2 that the friction coefficient μ is not low, the timer T1 is added after switching to the low μ road specification (step D4). On the other hand, if it is determined in step D1 that the road specification is low, it is also determined whether the friction coefficient μ of the road surface is currently determined to be low based on the determination output from the determining means 24c. Determination is made (step D5). If it is determined in step D5 that the friction coefficient μ is low, the specifications of the suspension 13 and the condition of the road surface correspond, so the timer T1 is reset.
- However, if it is determined in step D5 that the friction coefficient μ is not low, the process moves to step D4. That is, the timer T1 indicates that the suspension 13 is low μ.
The road surface is changed from a low μ road to a road surface with a high friction coefficient when there is no low μ road determination output from the determining means 24c within the operating period (for example, about 1 to 2 minutes). It is determined that the suspension has changed to the normal specification, and outputs a command to switch to the normal specification to the second suspension control means 24b.

As a result, in the low-μ road specification state, if a low-μ road state determination output is not obtained from the determining means 24c for a predetermined period of time set by the timer T1, the suspension 13 is controlled to switch to the normal specification. Ru.

On the other hand, the road surface is no longer in a low μ road condition.
The occurrence of the condition for canceling the road specification can be determined not only from the determination output from the determining means 24c but also from the vehicle body acceleration. For example, taking advantage of the fact that the lateral G generated during cornering is low on low μ roads but high on high μ roads,
Acceleration that cannot occur on a low μ road is detected by timer T.
If the friction coefficient μ continues for a predetermined time set in step 2 or more, it is determined that the friction coefficient μ of the road surface is not so low, and the suspension 13 is switched to the normal specification.

To explain in detail with reference to FIG. 7, first, the acceleration (deceleration) of the vehicle body is determined from the time derivative (or difference) of the wheel speed from the sensor 20 or the output from the G sensor 21 (step El), and then the current Suspension control is low μ
Determine whether the road specifications are met (step E2)
. If the low μ road specification is selected, it is determined whether the vehicle body acceleration obtained in step E1 exceeds the maximum determination value (minimum determination value for deceleration) that can occur on a low μ road ( Step E3). If it is determined that the acceleration is exceeded, timer T2 is added after the acceleration determination (step E5), while if it is determined that the acceleration is not exceeded, timer T2 is added.
2 (step E4), it is determined whether the value of timer T2 has reached a certain value (step E6).
. When it is determined in this step E6 that the value of the timer T2 has reached a certain value, it is determined that the driving road surface has changed from a low μ road to a road surface with a high friction coefficient, and the second suspension control means 24b is set to the normal specification. A switching command is output to control the suspension 13 to switch from the low μ road specification to the normal specification (step E7).

Also, low μ road specification cancellation determination 9 according to the procedure shown in FIG.
Switching to the normal specification is basically performed based on the same principle as shown in Fig. 6, but in the procedure shown in Fig. 6, a means for determining whether or not it is in a low μ road condition is used. 24c
In contrast, in the procedure shown in FIG. 8, the slip and control information to suppress it (traction control information and ABS operation information) are ), it is determined that the friction coefficient μ of the road surface is not so low, and the suspension 13 is switched to the normal specification.

To explain in detail with reference to FIG. 8, first, it is determined whether the current suspension control is for low μ road specifications (
Step Fl). If the low μ road specification is selected, it is determined whether or not the timer T3 (corresponding to the slip determination timer or output reduction determination timer explained in FIGS. 3 to 5) has reached a certain value ( Step F3). If it is determined that the constant value has been reached, it is determined whether the slip count counter or the output reduction counter (corresponding to Figures 3 to 5) is below the constant value (step F3).
If it is determined that the friction coefficient is below a certain value, it is determined that the road surface is changing from a low μ road to a road surface with a high coefficient of friction.
A switching command to the normal specification is output to the second suspension control means 24b, and the suspension 13 is controlled to switch from the low μ road specification to the normal specification (step F4), and then the timer T3 and the counter are cleared (step F5). . Further, if it is determined in step F3 that the counter is not below a certain value, the process moves to step F5.

In this way, according to the device of this embodiment, the slip state of the wheel 12 within a continuous predetermined period.

Depending on the operating time or operating frequency of the traction control ECU 23 or the operating time or operating frequency of the anti-skid brake ECU 25, the low-μ road condition of the traveling road surface is determined extremely accurately by the first determining means 24c, and the determination result is Accordingly, the first suspension control means 2
4a, the control characteristics of the suspension 13 are switched to control characteristics suitable for a preset low μ road, and it becomes possible to optimize the control characteristics of the suspension 13 according to the friction coefficient μ of the road surface.

Therefore, by lowering the spring constant of the suspension 13 on a low μ road, part of the centrifugal load during cornering can be absorbed by the suspension 13, and as a result, the lateral grip of the wheels 12 can be maintained. . In addition, on low μ roads, tuck-in is generally more likely to occur due to throttle off during cornering, increasing the risk of spin. can be suppressed. Furthermore, on low-μ roads, stability in one direction decreases even when driving straight, and it becomes easy to wander due to unevenness or slope of the road surface. By optimizing the balance of forces,
Straight-line stability can be greatly improved.

As described above, according to this embodiment, it is possible to not only suppress a decrease in the grip force of the driving wheels as in the case of using a traction control system, but also to control the balance of the dynamic characteristics with the driven wheels. .

A more sophisticated optimization of vehicle motion can be achieved.

In addition, according to this embodiment, by using the timers T1 to T3, when a low μ road judgment output cannot be obtained, when the vehicle body acceleration exceeds a set value, or when the If the information can no longer be obtained, it is determined that the low μ road condition is no longer present, and the second suspension control means 24b automatically switches the suspension 13 from the low μ road specification to the normal specification, so that the friction coefficient of the road surface is always maintained. The suspension 13 can be controlled to switch to the optimum control characteristic according to μ.

In the above embodiment, when returning the suspension 13 from the low μ road specification to the normal specification, the operation is performed by the second suspension control means 24b, but the driver can return the suspension 13 by operating a switch or the like. You can.

[Effects of the Invention] As detailed above, according to the vehicle suspension control device of the present invention, the determination means determines the friction coefficient of the traveling road surface, and when the road surface condition has a low friction coefficient, the first While the suspension control means switches the control characteristics of the resuspension to the control characteristics suitable for the road surface condition with a low coefficient of friction, if there is no judgment output from the judgment means within the timer operation period, or when the vehicle body acceleration detection means If the detection result exceeds the set value, the second suspension control means switches the suspension to a control characteristic different from the control characteristic suitable for the road surface condition with a low coefficient of friction. It becomes possible to optimize the control characteristics of the suspension according to the friction coefficient of
On road surfaces with a low coefficient of friction, it is possible to stabilize vehicle behavior, improve straight-line stability, and suppress the tendency to tuck-in.

In addition, when the road surface condition no longer has a low friction coefficient, the second suspension control means automatically switches the suspension to the normal specification, which has the effect of constantly switching and controlling the suspension to the optimal control characteristics according to the friction coefficient of the road surface. be.

[Brief explanation of drawings]

1 to 11 show a vehicle suspension control device as an embodiment of the present invention, FIG. 1 is a control block diagram thereof, and FIG. 2 is its engine system. An overall configuration diagram showing the suspension system, brake system, and control system, and Figures 3 to 5 are flowcharts for explaining an example of a control procedure for switching the suspension from normal specifications to low μ road specifications, and Figures 6 to 8. 9 and 10 are flowcharts for explaining an example of a control procedure for switching the suspension from a low μ road specification to a normal specification.
11(a) and 11(b) are block diagrams showing examples of information communication states within the control system. 1-Combustion chamber, 2--Intake passage, 3--Exhaust passage, 4-
・-Air flow sensor, 5-・-Throttle valve, 6-・
・Electromagnetic fuel injection valve (electromagnetic valve), 7-・- spark plug,
8... Bypass path, 9-Bypass valve, 10.11.
・-Motor, 12-Wheel, 13-Suspension, 14
-Air spring, 15-Shock absorber, 16°17-
Air pump, 18-=brake (braking mechanism). 19-pump, 20-sensor, 21-G sensor (acceleration detection means), 22-engine control ECU. 23-Throttle valve control ECU (traction control EC
U, driving force control means), 23a-1 - traction control operation lamp, 24 - suspension control ECU, 24a
-First suspension control means, 24b-Second suspension control means, 24c-Determination means, 25-Anti-skid brake ECU (braking force control means), 25a-
・ABS operation lamp, 26-A/T control ECU, 27-
Master control ECU, 28-accelerator pedal, 29...
-Shift lever 3o... -Steering wheel, E-...
Engine, T1-T3-timer.

Claims (2)

[Claims] (1) Determination means that is provided with a suspension that is interposed between the wheels and the vehicle body and whose control characteristics can be switched to at least two levels, determines that the road surface on which the vehicle is traveling has a low friction coefficient, and outputs an output to that effect. and a first suspension control means for switching and controlling the suspension to a control characteristic suitable for a road surface condition with a low coefficient of friction in response to the determination output from the determination means; a timer that operates when the characteristic is switched to a control characteristic, and a timer that operates when the timer is switched to a control characteristic that is different from a control characteristic suitable for a road surface condition with a low coefficient of friction when there is no judgment output from the judgment means within the operation period of the timer. 2nd to control switching
1. A suspension control device for a vehicle, characterized in that a suspension control device is provided. (2) Determination means that is provided with a suspension that is interposed between the wheels and the vehicle body and whose control characteristics can be switched to at least two stages, and that determines that the road surface on which the vehicle is traveling has a low coefficient of friction and outputs an output to that effect. a first suspension control means that receives a determination output from the determination means and controls the suspension to switch to a control characteristic suitable for a road surface condition with a low friction coefficient; a vehicle body acceleration detection means that detects vehicle body acceleration; When the vehicle body acceleration detected by the vehicle body acceleration detection means exceeds a set value while the control characteristics have been switched to a control characteristic suitable for a road surface condition with a low coefficient of friction, the suspension is controlled to be suitable for a road surface condition with a low coefficient of friction. 1. A suspension control device for a vehicle, comprising: a second suspension control means for switching control to a control characteristic different from the control characteristic.