JP2008024143A - Suspension control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a suspension control device effectively suppressing pitching at braking by suspension control. <P>SOLUTION: The suspension control device is provided with a braking operation detection means 3 for detecting whether or not it is during braking operation by a driver; a vehicle speed detection means 2 for detecting a vehicle speed; and rear suspension control means 4C, 4D for controlling stroke of a rear suspension. When it is detected that it is during braking operation by the braking operation detection means 3, stretching of the rear suspension is suppressed by the rear suspension control means 4C, 4D according to the vehicle speed detected by the vehicle speed detection means 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a suspension control device that controls at least a rear suspension.

When the vehicle is braked suddenly by a brake operation by the driver, load movement occurs on the front side of the vehicle, which may cause a large pitching in which the front side sinks and the rear side rises. In such a case, the vehicle occupant feels uncomfortable and the riding comfort decreases. Therefore, various methods for suppressing such pitching have been proposed. In the suspension device described in Patent Document 1, by making the damping characteristic on the compression side of the front side shock absorber a hard characteristic at the start of sudden braking and making the damping characteristic on the extension side of the rear side shock absorber a hard characteristic, Suppresses pitching.
Japanese Patent Laid-Open No. 9-277813

  The coefficient of friction between the tire and the road surface increases as the vehicle speed decreases, and is highest immediately before the vehicle stops. Therefore, when braking suddenly while running at a walking speed (very low speed), a very large braking acceleration is generated, and the deceleration of the vehicle increases. As a result, as shown in FIG. 5, the pitch angle of the vehicle becomes very large, resulting in excessive pitching. When such excessive pitching occurs, the effect of suppressing the excessive pitching cannot be sufficiently obtained only by controlling the damping force of the shock absorber as in the above-described suspension device.

  Accordingly, an object of the present invention is to provide a suspension control device that effectively suppresses pitching during braking by suspension control.

  A suspension control device according to the present invention includes a braking operation detection unit that detects whether or not a braking operation is being performed by a driver, a vehicle speed detection unit that detects a vehicle speed, and a rear suspension control unit that controls a stroke of the rear suspension. When the braking operation detecting means detects that the braking operation is being performed, the rear suspension control means suppresses the extension of the rear suspension according to the vehicle speed detected by the vehicle speed detecting means.

  In this suspension control device, the braking operation detecting means detects whether or not the driver is performing a braking operation, and the vehicle speed detecting means detects the vehicle speed. In the suspension control device, when the braking operation is being performed, the rear suspension control means suppresses the extension of the stroke of the rear suspension according to the vehicle speed. The vehicle speed when this suppression control is performed is a vehicle speed region in which pitching (particularly excessive pitching) may occur in the vehicle during the braking operation. In this way, when there is a possibility of pitching during braking, it is possible to suppress the increase in the center of gravity of the vehicle by suppressing the extension of the rear suspension, effectively suppressing pitching (rear lift) during braking. can do. As a result, the vehicle occupant is not subject to discomfort due to excessive pitching, and the riding comfort is improved.

  In the suspension control device of the present invention, when the braking operation detecting means detects that the braking operation is being performed, the rear suspension control means suppresses the extension of the rear suspension when the vehicle speed detected by the vehicle speed detecting means is equal to or lower than a predetermined vehicle speed. It is good.

  In this suspension control device, when the braking operation is being performed, the rear suspension control means suppresses the extension of the rear suspension stroke when the vehicle speed is equal to or lower than the predetermined vehicle speed. Since the coefficient of friction between the tire and the road surface increases as the vehicle speed decreases, a very large deceleration occurs in the vehicle when braking during low-speed traveling, resulting in excessive pitching. That is, there is a possibility that a larger pitching occurs at a lower speed. The predetermined vehicle speed is set in consideration of the relationship between the friction coefficient between the tire and the road surface and the vehicle speed, and is a vehicle speed threshold value for determining a low speed range in which a large pitching may occur during braking. Therefore, in this suspension device, the rear suspension extension restraint control is performed only at a low speed at which a large pitching may occur, and therefore the suspension control for restraining the pitching is not performed in an unnecessary scene. Therefore, in an unnecessary scene, the suspension operates under normal control, and riding comfort is improved.

  In the suspension control device of the present invention, when the braking operation detecting means detects that the braking operation is being performed, the rear suspension control means locks the rear suspension when the vehicle speed detected by the vehicle speed detecting means is equal to or lower than a predetermined vehicle speed. Good.

  In this suspension control device, the rear suspension control means locks (fixes) the stroke displacement of the rear suspension to suppress the extension of the stroke. By locking in this way, the operation of the rear suspension is prohibited, and the vehicle is pulled downward by the unsprung weight in addition to the sprung weight on the rear side. As a result, the rear lift is suppressed, and pitching during braking can be effectively suppressed.

  In the suspension control device of the present invention, when the braking operation detecting means detects that the braking operation is being performed, the rear suspension control means may contract the rear suspension when the vehicle speed detected by the vehicle speed detecting means is equal to or lower than a predetermined vehicle speed. Good.

  In this suspension control device, the rear suspension control means contracts the stroke of the rear suspension to suppress the extension of the stroke. By forcibly contracting the rear suspension in this way, the rear lift is suppressed and pitching during braking can be effectively suppressed.

  The suspension control device of the present invention includes a deceleration detection means for detecting the deceleration of the vehicle. When the deceleration detected by the deceleration detection means is equal to or greater than a predetermined deceleration, the rear suspension control means extends the rear suspension. It is good also as a structure which suppresses.

  In this suspension control device, the deceleration of the vehicle is detected by the deceleration detection means. In the suspension control device, when the braking operation is in progress, when the deceleration is equal to or greater than the predetermined deceleration, the rear suspension control means suppresses the extension of the rear suspension stroke according to the vehicle speed. During slow braking even during low-speed traveling, there is no large pitching that makes the passenger uncomfortable. Conversely, excessive braking occurs during sudden braking during low-speed driving. The predetermined deceleration is a deceleration threshold for determining a relatively abrupt braking in which a large pitching may occur during braking. Therefore, in this suspension device, the rear suspension extension suppression control is performed at the time of sudden braking in which a large pitching may occur. Therefore, the suspension control for suppressing the pitching is not performed in an unnecessary scene. Therefore, in an unnecessary scene, the suspension operates under normal control, and riding comfort is improved.

  According to the present invention, the pitching during braking can be effectively suppressed by suppressing the extension of the rear suspension.

  Hereinafter, an embodiment of a suspension control device according to the present invention will be described with reference to the drawings.

  In the present embodiment, the suspension control device according to the present invention is applied to a suspension control device that performs vehicle attitude control, vehicle height control, and the like in accordance with vehicle conditions. The suspension control apparatus according to the present embodiment includes an electromagnetic suspension for each wheel, and the stroke of the suspension is arbitrarily changed by the electromagnetic suspension.

  The suspension control device 1 according to the present embodiment will be described with reference to FIGS. FIG. 1 is a configuration diagram of a suspension control apparatus according to the present embodiment. FIG. 2 is a graph showing the relationship between the vehicle speed and the friction coefficient between the tire and the road surface. FIG. 3 is a schematic diagram of the vehicle showing a case where the rear electromagnetic suspension is not locked and a case where the rear electromagnetic suspension is locked when a brake operation is performed at a low speed.

  The suspension control device 1 controls the suspension of each wheel in order to improve steering stability and riding comfort. In particular, the suspension control device 1 controls the rear suspension in order to suppress excessive pitching that occurs when the brake is operated during low-speed traveling. For this purpose, the suspension control device 1 includes a vehicle speed sensor 2, a brake stroke sensor 3, electromagnetic suspensions 4A, 4B, 4C, 4D of each wheel, an ECU [Electronic Control Unit] 5, and the like.

  In the present embodiment, the vehicle speed sensor 2 corresponds to vehicle speed detection means described in the claims, the brake stroke sensor 3 corresponds to braking operation detection means described in the claims, and the rear electromagnetic suspensions 4C, 4D. Corresponds to the rear suspension control means described in the claims.

  The vehicle speed sensor 2 is a sensor that detects the speed of the vehicle. The vehicle speed sensor 2 detects the vehicle speed and transmits the detected vehicle speed to the ECU 5 as a vehicle speed signal. The brake stroke sensor 3 is a sensor that detects the stroke of the brake pedal. The brake stroke sensor 3 detects the stroke of the brake pedal, and transmits the detected stroke to the ECU 5 as a brake signal.

  Each of the electromagnetic suspensions 4A, 4B, 4C and 4D includes an electromagnetic damper incorporating a motor and a coil spring, and is a suspension that changes the stroke by changing the damping force of the electromagnetic damper by the motor. A control current is supplied from the ECU 5 to each of the electromagnetic suspensions 4A, 4B, 4C, 4D. In each of the electromagnetic suspensions 4A, 4B, 4C, and 4D, the motor is driven according to the supplied control current, the damping force of the electromagnetic damper is changed, and the stroke is changed by a predetermined amount. Further, in each of the electromagnetic suspensions 4A, 4B, 4C, and 4D, when the supply of control current from the ECU 5 is stopped, the suspension becomes inoperative (suspension displacement fixed state).

  The ECU 5 is an electronic control unit that includes a CPU [Central Processing Unit], a ROM [Read Only Memory], a RAM [Random Access Memory], a motor driver, and the like, and performs overall control of the suspension control device 1. The ECU 5 receives detection signals from the sensors 2, 3 and the like at regular intervals, and controls the electromagnetic suspensions 4A, 4B, 4C, 4D based on the detection signals.

  The basic control in the ECU 5 will be described. The ECU 5 stabilizes the vehicle posture based on detection signals from the vehicle speed sensor 2, a G sensor (not shown) in each direction of the vehicle, a steering angle sensor (not shown), a vehicle height sensor (not shown), and the like. The target stroke change amount of each wheel suspension is set in order to perform control (roll control, pitching control, bounce control, etc.) and vehicle height adjustment. Then, the ECU 5 sets a control current (target current) necessary for achieving the target stroke change amount, and supplies the control current to the motors of the electromagnetic suspensions 4A, 4B, 4C, and 4D.

  Pitching suppression control during brake operation during low-speed traveling in the ECU 5 will be described. The ECU 5 determines based on the brake signal from the brake stroke sensor 3 whether the brake is being operated (whether the brake pedal has been depressed from the detected stroke).

  When the brake is being operated, the ECU 5 determines whether the vehicle speed is lower than the low speed determination vehicle speed based on the vehicle speed signal from the vehicle speed sensor 2. The low speed determination vehicle speed is a vehicle speed threshold value for determining a low speed range in which large pitching may occur during braking, and is, for example, several km / h, which is about the walking speed. The low speed determination vehicle speed is set in advance by experiment or simulation in consideration of the relationship between the friction coefficient between the tire and the road surface and the vehicle speed. In the determination of whether or not the vehicle speed is low, a vehicle speed lower than the low speed determination vehicle speed is determined as a low speed while the vehicle is running, except when the vehicle speed is 0 km / h.

  As shown in FIG. 2, the coefficient of friction between the tire and the road surface increases as the vehicle speed decreases, and is highest immediately before stopping. Therefore, even if the brake oil pressure is the same, when braking is performed while traveling at a low speed such as the walking speed, a much larger deceleration is generated in the vehicle than in other vehicle speed ranges. Therefore, there is a possibility that a larger pitching occurs at a lower speed.

  When the brake is being operated and the speed is low, the ECU 5 prohibits the operation of the rear electromagnetic suspensions 4C and 4D in order to lock the rear suspension (that is, the supply of control current to the rear electromagnetic suspensions 4C and 4D is stopped). Alternatively, the ECU 5 sets the stroke contraction amount as the target stroke change amount of the rear electromagnetic suspensions 4C and 4D in order to forcibly contract the rear suspension stroke, and the target stroke change amount becomes the same as described above. For this purpose, a control current necessary for this is supplied to motors of the rear electromagnetic suspensions 4C and 4D. In these two pitching suppression controls, either the operation prohibition control or the stroke contraction control may be performed, or the stroke contraction control is performed when the pitching cannot be sufficiently suppressed after performing the operation prohibition control. You may do it.

  The stroke contraction amount is a contraction amount of a stroke of the suspension for actively suppressing a rear lift (and consequently an increase in the height of the center of gravity of the vehicle) in order to suppress pitching when a brake operation is performed during low-speed traveling. The stroke contraction amount may be set in advance by experiment or simulation, or may be set as a variable amount in consideration of the stroke amount of the rear suspension, the height of the center of gravity of the vehicle, or the like.

  When the rear suspension is not locked, the rear suspension is freely displaceable, so that the vehicle is pulled downward only by the sprung weight on the rear side. The ease of appearance of the pitching behavior in this case can be obtained as the value of Axo by equation (1). When the rear suspension is locked, the rear suspension is displaced and fixed, so that the vehicle is pulled downward by the unsprung weight in addition to the sprung weight on the rear side. The ease of the pitching behavior in this case can be obtained as the value of Axo ′ by the equation (2). When the rear suspension is actively contracted, the rear suspension is fixed with the displacement contracted, so the rear side pulls the vehicle downward with the unsprung weight in addition to the unsprung weight and forces the vehicle height. Will be reduced. The ease of the pitching behavior in this case can be obtained as the value of Axo ″ by equation (3).

As shown in FIG. 3, WB is a wheel base, W _f is a wheel load applied to the front wheel, W _r is a wheel load applied to the rear wheel, m _usr is an unsprung mass, and g is a gravitational acceleration. _Where (m _usr · g) is the unsprung weight, H _g is the height of the center of gravity of the vehicle, and ΔH _g is the amount of change (amount of decrease) in the height of the center of gravity. Axo, Axo ′, and Axo ″ are parameters that indicate the ease with which the pitching behavior occurs, and the smaller the value, the more likely the pitching behavior to appear.

In Expression (2), since the subtraction term of the unsprung weight is eliminated from Expression (1), Axo ′ in Expression (2) is larger than Axo in Expression (1). Further, when the rear suspension is actively contracted, ΔH _g becomes a negative value, so Axo ″ in Expression (3) is further larger than Axo ′ in Expression (2). Therefore, Axo <Axo ′ <Axo ″. Thus, when the rear suspension is locked, the pitching behavior is difficult to occur, and when the rear suspension is contracted, the pitching behavior is further difficult to occur.

  With reference to FIG. 1, the pitching suppression operation in the suspension control device 1 will be described. In particular, the processing in the ECU 5 will be described along the flowchart of FIG. FIG. 4 is a flowchart showing a flow of pitching suppression control in the ECU of FIG.

  The vehicle speed sensor 2 detects the vehicle speed and transmits a vehicle speed signal to the ECU 5. The brake stroke sensor 3 detects the stroke of the brake pedal and transmits a brake signal to the ECU 5. The ECU 5 receives detection signals from the sensors 2 and 3 at regular intervals.

  At regular time intervals, the ECU 5 determines whether or not the brake is being operated from the stroke amount of the brake pedal (S1). If it is determined in S1 that the brake is not being operated, the ECU 5 returns to the process of S1. On the other hand, if it is determined in S1 that the brake is being operated, the ECU 5 determines whether or not the vehicle speed is low (S2). If it is determined at S2 that the speed is not low, the ECU 5 returns to the process of S1.

  When it is determined that the speed is low in S2 (that is, when it is predicted that excessive pitching may occur), the ECU 5 stops the supply of control current to the rear electromagnetic suspensions 4C and 4D (S3). Then, the rear electromagnetic suspensions 4C and 4D stop operating and do not undergo stroke displacement. As a result, the weight on the rear side increases by the unsprung weight, and the rear side is pulled down. As a result, the height of the center of gravity of the vehicle is lowered, and pitching is suppressed. In this case, as shown in FIG. 3, the center of gravity height Hg is lowered and the pitching is suppressed as in the vehicle V <b> 2 without the excessive pitching state as in the vehicle V <b> 1.

  Further, the ECU 5 sets the stroke contraction amount as the target stroke change amount, and supplies the control current necessary for achieving the target stroke change amount to the rear electromagnetic suspensions 4C and 4D (S3). Then, in the rear electromagnetic suspensions 4C and 4D, the motor is driven according to the control current, and the stroke of the electromagnetic damper is shortened by the stroke contraction amount. As a result, the weight on the rear side increases by the unsprung weight, and is forcibly pulled downward, and the rear side is pulled down. As a result, the height of the center of gravity of the vehicle is further reduced, and pitching is further suppressed.

  According to the suspension control device 1, it is possible to effectively suppress pitching (rear lift) during braking by suppressing the extension of the stroke of the rear suspension during braking during low-speed traveling. As a result, the vehicle occupant is not subject to discomfort due to excessive pitching, and the riding comfort is improved.

  In addition, since the suspension control apparatus 1 performs suspension control for suppressing pitching only during low-speed traveling, unnecessary suspension control is not performed in a vehicle speed range where excessive pitching does not occur. Therefore, in an unnecessary scene, the rear suspension operates under normal control, and riding comfort is improved.

  As mentioned above, although embodiment which concerns on this invention was described, this invention is implemented in various forms, without being limited to the said embodiment.

  For example, in the present embodiment, an electromagnetic suspension is provided on four wheels and applied to a device that performs suspension control on four wheels, but any device that performs suspension control on at least two rear wheels may be used.

  In this embodiment, the electromagnetic suspension is applied as the rear suspension control means, but other means such as a suspension with a stroke lock mechanism may be applied.

  In the present embodiment, the brake stroke sensor is applied as the braking operation detection means. However, other detection means such as a brake pedal depression force, a master cylinder hydraulic pressure, and a brake pedal ON / OFF may be applied.

  Further, in the present embodiment, when the brake is operated and the vehicle is traveling at a low speed, the rear suspension extension is controlled to suppress the pitching, but the brake is operated and the vehicle is traveling at a low speed. It is also possible to perform a control for suppressing the extension of the rear suspension in order to suppress the pitching in the case of sudden braking with a deceleration of not less than a predetermined deceleration. By performing the suppression control only during a sudden braking operation in this way, the suppression control is not performed during a gentle braking operation such as during a traffic jam, so the passenger does not receive the discomfort due to the suspension extension suppression control, Ride comfort does not decrease. The deceleration detection means may be configured to directly detect the deceleration (including the braking force increase speed) by a sensor, or the sensor may detect an amount related to a braking force such as a stroke of the brake pedal or a pedaling force. It is good also as a structure which calculates change speed.

  In the present embodiment, the rear suspension extension control is performed to suppress the pitching when the brake is being operated and the vehicle is traveling at a low speed. However, the pitching is not performed during the brake operation even in other vehicle speed regions. If this occurs, the rear suspension extension control may be performed to suppress pitching even in other vehicle speed regions.

It is a block diagram of the suspension control apparatus which concerns on this Embodiment. It is a graph which shows the relationship between a vehicle speed and the friction coefficient between a tire and a road surface. FIG. 2 is a schematic diagram of a vehicle showing a case where a rear electromagnetic suspension is not locked and a case where a rear electromagnetic suspension is locked when a brake operation is performed at a low speed. It is a flowchart which shows the flow of the pitching suppression control in ECU of FIG. It is a schematic diagram of a vehicle in which excessive pitching has occurred when a brake operation is performed at low speed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Suspension control apparatus, 2 ... Vehicle speed sensor, 3 ... Brake stroke sensor, 4A ... Left front electromagnetic suspension, 4B ... Right front electromagnetic suspension, 4C ... Left rear electromagnetic suspension, 4D ... Right rear electromagnetic suspension, 5 ... ECU

Claims (5)

Braking operation detecting means for detecting whether or not the driver is performing a braking operation;
Vehicle speed detection means for detecting the vehicle speed;
Rear suspension control means for controlling the stroke of the rear suspension,
A suspension control device characterized in that when the braking operation detecting means detects that a braking operation is being performed, the rear suspension control means suppresses the extension of the rear suspension according to the vehicle speed detected by the vehicle speed detecting means.   The rear suspension control means suppresses the extension of the rear suspension when the braking operation detecting means detects that the braking operation is being performed and the vehicle speed detected by the vehicle speed detecting means is equal to or lower than a predetermined vehicle speed. The suspension control apparatus according to 1.   The rear suspension control means locks the rear suspension when the vehicle speed detected by the vehicle speed detection means is below a predetermined vehicle speed when the braking operation detection means detects that the braking operation is being performed. Suspension control device to be described.   The rear suspension is contracted by the rear suspension control means when the braking operation detecting means detects that the braking operation is being performed and the vehicle speed detected by the vehicle speed detecting means is equal to or lower than a predetermined vehicle speed. Suspension control device to be described. A deceleration detecting means for detecting the deceleration of the vehicle;
The extension of the rear suspension is suppressed by the rear suspension control means when the deceleration detected by the deceleration detection means is equal to or greater than a predetermined deceleration. Suspension control device to be described.

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