Patent ID: 12208657

DETAILED DESCRIPTION

A description will hereinafter be made on an example of a controller, a vehicle, and a control method according to the present invention with reference to the drawings.

A description will hereinafter be made on a four-wheeled motor vehicle as the example of the vehicle according to the present invention. However, the vehicle according to the present invention may be a vehicle other than the four-wheeled motor vehicle. Examples of the vehicle other than the four-wheeled motor vehicle are a pedal-driven vehicle, a two-wheeled motor vehicle, a three-wheeled motor vehicle, and the like, each of which has at least one of an engine and an electric motor as a drive source. The pedal-driven vehicle means a vehicle in general that can travel forward on a road by a depression force applied to pedals. That is, the pedal-driven vehicles are a normal pedal-driven vehicle, an electrically-assisted pedal-driven vehicle, an electric pedal-driven vehicle, and the like. The two-wheeled motor vehicle or the three-wheeled motor vehicle means a so-called motorcycle, and the motorcycles are a bike, a scooter, an electric scooter, and the like.

A configuration, operation, and the like, which will be described below, constitute merely one example, and the present invention is not limited to a case with such a configuration, such operation, and the like. In the drawings, the same or similar members or portions will be denoted by the same reference sign or will not be denoted by the reference sign. A detailed structure will appropriately be illustrated in a simplified manner or will not be illustrated.

A description will hereinafter be made on a controller1according to an embodiment, a vehicle100including the controller1, and a control method executed by the controller1.

<Configurations of Vehicle and Controller>

FIG.1is a side view of the vehicle according to the embodiment of the present invention.FIG.2is a plan view of the vehicle according to the embodiment of the present invention. InFIG.1andFIG.2, a left side of each sheet corresponds to a front side of the vehicle100.

The vehicle100is an off-road vehicle and includes a vehicle body101and wheels103. The vehicle100according to this embodiment is a four-wheeled motor vehicle and includes four wheels103. More specifically, the vehicle100includes, as the wheels103, a front left wheel103FL, a front right wheel103FR, a rear left wheel103RL, and a rear right wheel103RR.

The vehicle100also includes a spring110and a shock absorber111. The spring110and the shock absorber111are provided between the vehicle body101and each of the wheels103. Thus, the vehicle100includes four springs110and four shock absorbers111. More specifically, the vehicle100includes, as the springs110, a spring110FL, a spring110FR, a spring110RL, and a spring110RR. The vehicle100includes, as the shock absorbers111, a shock absorber111FL, a shock absorber111FR, a shock absorber111RL, and a shock absorber111RR.

The spring110FL and the shock absorber111FL are provided between the vehicle body101and the front left wheel103FL. The spring110FR and the shock absorber111FR are provided between the vehicle body101and the front right wheel103FR. The spring110RL and the shock absorber111RL are provided between the vehicle body101and the rear left wheel103RL. The spring110RR and the shock absorber111RR are provided between the vehicle body101and the rear right wheel103RR.

The shock absorber111according to this embodiment is a shock absorber in a damping force adjustment type. That is, the shock absorber111is a shock absorber, a damping force characteristic of which can be changed. For this reason, the vehicle100includes an actuator112that adjusts a damping force of the shock absorber111. The actuator112is provided for each of the shock absorbers111. More specifically, the vehicle100includes four actuators112. Further more specifically, the vehicle100includes, as the actuators112, an actuator112FL, an actuator112FR, an actuator112RL, an actuator112RR. The actuator112FL adjusts the damping force of the shock absorber111FL. The actuator112FR adjusts the damping force of the shock absorber111FR. The actuator112RL adjusts the damping force of the shock absorber111RL. The actuator112RR adjusts the damping force of the shock absorber111RR. Any of various known shock absorbers can be used as the shock absorber111as long as the shock absorber is of the damping force adjustment type.

The controller1is electrically connected to the actuator112. The controller1outputs a command signal to the actuator112, and the command signal corresponds to the damping force of the shock absorber111. That is, the controller1is configured to control the damping force of the shock absorber111via the actuator112. More specifically, in this embodiment, the controller1outputs the command signal corresponding to the damping force of the shock absorber111FL to the actuator112FL. The controller1outputs the command signal corresponding to the damping force of the shock absorber111FR to the actuator112FR. The controller1outputs the command signal corresponding to the damping force of the shock absorber111RL to the actuator112RL. The controller1outputs the command signal corresponding to the damping force of the shock absorber111RR to the actuator112RR.

Here, in a state where the compression speed of the shock absorber111is the same, the damping force of the shock absorber111differs by the damping force characteristic of the shock absorber111. For example, the damping force characteristic of the shock absorber111is changed to be hard. In such a case, in the state where the compression speed of the shock absorber111remains the same, the damping force of the shock absorber111is increased. Meanwhile, for example, the damping force characteristic of the shock absorber111is changed to be soft. In such a case, in the state where the compression speed of the shock absorber111remains the same, the damping force of the shock absorber111is reduced. For this reason, in this embodiment, the controller1outputs the command signal corresponding to the damping force characteristic of the shock absorber111to the actuator112. That is, the controller1is configured to control the damping force characteristic of the shock absorber111via the actuator112. For example, in the case where the shock absorber111is a hydraulic shock absorber, the controller1controls a cross-sectional area of a channel, through which hydraulic oil for the shock absorber111flows, so as to control the damping force characteristic of the shock absorber111. Meanwhile, for example, in the case where the shock absorber111is a magnetic fluid shock absorber, the controller1controls a magnetic field or an electric field acting on a magnetic fluid for the shock absorber111, and kinetic viscosity of the magnetic fluid, so as to control the damping force characteristic of the shock absorber111.

The command signal that is output from the controller1to the actuator112differs by a type of the shock absorber111and a type of the actuator112. For example, in the case where the shock absorber111is configured that the damping force characteristic thereof is changed according to a value of an electric current into the actuator112, the command signal output from the controller1is the electric current. That is, the controller1outputs the electric current corresponding to the damping force characteristic of the shock absorber111to the actuator112. Meanwhile, for example, in the case where the shock absorber111is configured that the damping force characteristic thereof is changed according to a value of a voltage into the actuator112, the command signal output from the controller1is the voltage. That is, the controller1outputs the voltage corresponding to the damping force characteristic of the shock absorber111to the actuator112.

The vehicle100according to this embodiment also includes: a longitudinal acceleration sensor113, a lateral acceleration sensor114, a signal output device115, and an unsprung acceleration sensor116, each of which is electrically connected to the controller1.

The longitudinal acceleration sensor113is provided to the vehicle body101and detects longitudinal acceleration of the vehicle body101. The lateral acceleration sensor114is provided to the vehicle body101and detects lateral acceleration of the vehicle body101.

The signal output device115outputs a signal corresponding to a speed of the vehicle100. Conventionally, various configurations are adopted to calculate the speed of the vehicle. For this reason, as the signal corresponding to the speed of the vehicle100, any of various signals that have conventionally been used to calculate the speed of the vehicle can be used. The signal output device115is a signal output device that outputs any of such conventionally known signals. For example, a configuration to calculate the speed of the vehicle on the basis of a gear stage of a transmission and an engine speed has conventionally been known. In the case where such a configuration is adopted for the vehicle100, the signal output device115is a device that outputs a signal related to the gear stage of the transmission and the engine speed. In addition, for example, a configuration to calculate the speed of the vehicle on the basis of a wheel rotational frequency has been known. In the case where such a configuration is adopted for the vehicle100, the signal output device115is a wheel rotational frequency sensor.

The unsprung acceleration sensor116detects vertical acceleration of an unsprung portion of the vehicle100. In the vehicle100, the unsprung portion of the vehicle100is a portion on the wheel103side with the shock absorber111being a reference. For example, the wheel103, an unillustrated hub, an unillustrated axle, and the like correspond to the unsprung portion of the vehicle100. In this embodiment, the vehicle100includes, as the unsprung acceleration sensors116, an unsprung acceleration sensor116FL, an unsprung acceleration sensor116FR, an unsprung acceleration sensor116RL, and an unsprung acceleration sensor116RR.

The unsprung acceleration sensor116FL is provided at a position near the shock absorber111FL in the unsprung portion of the vehicle100. The unsprung acceleration sensor116FL detects the vertical acceleration that is generated to the unsprung portion near the shock absorber111FL. The unsprung acceleration sensor116FR is provided at a position near the shock absorber111FR in the unsprung portion of the vehicle100. The unsprung acceleration sensor116FR detects the vertical acceleration that is generated to the unsprung portion near the shock absorber111FR. The unsprung acceleration sensor116RL is provided at a position near the shock absorber111RL in the unsprung portion of the vehicle100. The unsprung acceleration sensor116RL detects the vertical acceleration that is generated to the unsprung portion near the shock absorber111RL. The unsprung acceleration sensor116RR is provided at a position near the shock absorber111RR in the unsprung portion of the vehicle100. The unsprung acceleration sensor116RR detects the vertical acceleration that is generated to the unsprung portion near the shock absorber111RR.

The number and the arrangement positions of the unsprung acceleration sensors116merely constitute one example. Any number and any arrangement position of the unsprung acceleration sensor116can be adopted as long as the vertical acceleration that is generated to the unsprung portion near each of the shock absorbers111can be calculated by detection, estimation, or the like. The longitudinal acceleration sensor113, the lateral acceleration sensor114, the signal output device115, and the unsprung acceleration sensor116may separately be provided, or at least two thereof may be configured as one unit. For example, a so-called inertial measurement unit may be used as the longitudinal acceleration sensor113and the lateral acceleration sensor114.

Here, for example, like an off-road vehicle or the like, there is a vehicle that possibly jumps during travel. A jump means a state where tires of all the wheels come off a road surface during the travel. When the vehicle that has jumped lands on the ground and the damping force of the shock absorber is small, the shock absorber reaches a so-called maximum stroke. That is, when the vehicle that has jumped lands on the ground, the shock absorber is compressed to an end on a compression side, and a piston in the shock absorber collides with a stopper. As a result, an instantaneous shock is transmitted to an occupant, which worsens riding comfort of the occupant. In order to solve this problem, the damping force of the shock absorber has to be increased so as to prevent the shock absorber from reaching the maximum stroke. However, when the damping force of the shock absorber is simply increased, the shock absorber becomes too stiff. As a result, the instantaneous shock is transmitted to the occupant after all, which worsens the riding comfort of the occupant.

Meanwhile, the controller1according to this embodiment controls the damping force of the shock absorber111in a manner to prevent the damping force of the shock absorber111from becoming excessively large while suppressing the shock absorber111from reaching the maximum stroke when the vehicle100that has jumped lands on the ground. A description will hereinafter be made on a detailed configuration of an example of the controller1that controls the damping force of the shock absorber111just as described.

<Detailed Configuration of Controller>

FIG.3is a block diagram illustrating the controller according to the embodiment of the present invention.

The controller1includes a receiving section2, a jump detecting section3, and a control section4. The receiving section2is a functional section that receives detection values of the longitudinal acceleration sensor113, the lateral acceleration sensor114, the signal output device115, and the unsprung acceleration sensor116.

The jump detecting section3is a functional section detecting that the vehicle100has jumped. In this embodiment, the jump detecting section3detects that the vehicle100has jumped on the basis of the detection values of the longitudinal acceleration sensor113and the lateral acceleration sensor114. More specifically, in a state where the vehicle100jumps, tires of all the wheels103are brought into a state of coming off the road surface. Thus, in the state where the vehicle100jumps, a propelling force does not act on the vehicle100. As a result, in the state where the vehicle100jumps, the longitudinal acceleration of the vehicle body101, which is detected by the longitudinal acceleration sensor113, is reduced. In addition, in the state where the vehicle100jumps, the lateral acceleration of the vehicle body101, which is detected by the lateral acceleration sensor114, is reduced. Accordingly, in this embodiment, the jump detecting section3determines that the vehicle100has jumped when the detection value of the longitudinal acceleration sensor113becomes smaller than a prescribed threshold value and the detection value of the lateral acceleration sensor114becomes smaller than a prescribed threshold value. The threshold value of the longitudinal acceleration sensor113and the threshold value of the lateral acceleration sensor114may not be the same value.

Here, the above-described jump detection method for the vehicle100by the jump detecting section3is merely one example. For example, in the case where the vehicle100includes a vertical acceleration sensor that detects the vertical acceleration of the vehicle body101, the jump detecting section3may detect that the vehicle100has jumped on the basis of a detection value of the vertical acceleration sensor. More specifically, in the state where the vehicle100jumps, the tires of all the wheels103come off the road surface. Thus, input from the road surface to the vehicle body101no longer exists, and the vertical acceleration of the vehicle body101is reduced. Thus, the jump detecting section3may detect that the vehicle100has jumped when the detection value of the vertical acceleration sensor becomes smaller than a prescribed threshold value.

For example, in the case where the vehicle100includes a stroke sensor that measures a relative distance between the vehicle body101and the unsprung portion, the jump detecting section3may detect that the vehicle100has jumped on the basis of a detection value of the stroke sensor. More specifically, in a state where the vehicle100travels on the road surface, weight of the vehicle body101is applied to the spring110and the shock absorber111. Meanwhile, in the state where the vehicle100jumps, the weight of the vehicle body101is not applied to the spring110and the shock absorber111. Accordingly, the relative distance between the vehicle body101and the unsprung portion becomes longer in the state where the vehicle100jumps than in the state where the vehicle100travels on the road surface. In this way, the jump detecting section3can detect that the vehicle100has jumped on the basis of the detection value of the stroke sensor. Here, a method for calculating the relative distance between the vehicle body and the unsprung portion on the basis of the vertical acceleration of the vehicle body and the vertical acceleration of the unsprung portion has conventionally been known. Thus, in the case where the vehicle100includes the vertical acceleration sensor that detects the vertical acceleration of the vehicle body101, the jump detecting section3may calculate the relative distance between the vehicle body101and the unsprung portion on the basis of the detection value of the vertical acceleration sensor and the detection value of the unsprung acceleration sensor116and may thereby detect that the vehicle100has jumped.

The stroke sensor has a long arm section. Thus, in the case where such a stroke sensor is used for the off-road vehicle, it is concerned that the arm section of the stroke sensor contacts a rock, a branch, or the like, which causes failure of the stroke sensor. For this reason, the vehicle100is configured not to use the stroke sensor. In this way, it is possible to improve durability of the vehicle100.

The control section4is a functional section that executes landing damping force control. The landing damping force control is control to restrict the damping force of the shock absorber111during compression to be equal to or smaller than a prescribed damping force when the jump detecting section3detects the jump of the vehicle100.

The thus-configured controller1is mounted to the vehicle100that includes the shock absorber111in the damping force adjustment type. Accordingly, in the vehicle100, the damping force of the shock absorber111can be increased to such a damping force that does not cause the shock absorber111to reach the maximum stroke when the vehicle100that has jumped lands on the ground. In addition, in the controller1according to this embodiment, when the jump detection section3detects the jump of the vehicle100, the control section4restricts the damping force of the shock absorber111during the compression to be equal to or smaller than the prescribed damping force by the landing damping force control. Accordingly, in the vehicle100, to which the controller1is mounted, it is possible to suppress the shock absorber111from becoming too stiff at the time when the vehicle100that has jumped lands on the ground. Thus, the controller1according to this embodiment can suppress an instantaneous shock from being transmitted to the occupant at the time when the vehicle100that has jumped lands on the ground and can improve the riding comfort of the occupant at the time when the vehicle100lands on the ground in comparison with the background art.

Here, in the landing damping force control, the control section4of the controller1according to this embodiment suppresses an increase in the stroke of the shock absorber111, which is caused by the restriction of the damping force of the shock absorber111during the compression and thereby further improves the riding comfort of the occupant at the time when the vehicle100lands on the ground. A description will hereinafter be made on an example of such landing damping force control. Hereinafter, in order to facilitate understanding of the landing damping force control according to this embodiment, a description will firstly be made on behavior of the vehicle100in the case where the maximum stroke of the shock absorber111is suppressed without changing the damping force characteristic of the shock absorber111. Thereafter, a description will be made on the behavior of the vehicle100in the case where the landing damping force control according to this embodiment is executed.

FIG.4is a view for illustrating the behavior of the vehicle according to the embodiment of the present invention from a jumping state to a state after landing on the ground. A horizontal axis T illustrated inFIG.4represents time.

The vehicle100that is jumping at time T1lands on a road surface120at time T2. Kinetic energy at the time of landing of the vehicle100is absorbed by the shock absorber111when the kinetic energy is converted into thermal energy during the compression of the shock absorber111. Then, at time T3, the shock absorber111of the vehicle100is brought into the most compressed state. The control section4of the controller1executes the landing damping force control in a first compression process of the shock absorber111after the jump detecting section3detects the jump of the vehicle100. That is, the control section4executes the landing damping force control in a period from the time T2to the time T3inFIG.4.

FIG.5is a graph illustrating behavior of the shock absorber in the case where the damping force characteristic of the shock absorber is not changed at the time when the vehicle according to the embodiment of the present invention performs the operation illustrated inFIG.4. A horizontal axis T illustrated inFIG.5represents the time. A vertical axis ST illustrated inFIG.5represents the stroke of the shock absorber111. In this vertical axis ST, a state where the vehicle100is stopped on the road surface120is set to 0 as a reference state. In addition, this vertical axis ST has a positive value in a compression direction of the shock absorber111from the reference state and has a negative value in an extension direction of the shock absorber111from the reference state. Furthermore, the damping force of the shock absorber111, the behavior of which is illustrated inFIG.5, is set to such a magnitude that can suppress the maximum stroke of the shock absorber111.

At the time T1, the vehicle100is jumping. Thus, at the time T1, the weight of the vehicle body101is not applied to the spring110and the shock absorber111. For this reason, the shock absorber111is in an extended state from the reference state. When the vehicle100lands on the road surface120at the time t2, the weight of the vehicle body101is applied to the shock absorber111, and the shock absorber111is compressed. Then, at the time T3, the shock absorber111of the vehicle100is brought into the most compressed state.

FIG.6is a graph illustrating a compression speed of the shock absorber when the shock absorber is operated as illustrated inFIG.5. A horizontal axis T illustrated inFIG.6represents the time. A vertical axis DV illustrated inFIG.6represents the compression speed of the shock absorber111.

When the vehicle100lands on the road surface120at the time T2and the shock absorber111starts being compressed, the compression speed of the shock absorber111is gradually increased. In addition, in a compression process of the shock absorber111, the kinetic energy at the time of landing of the vehicle100is converted into the thermal energy, and the kinetic energy is thereby absorbed by the shock absorber111. Accordingly, the compression speed of the shock absorber111is gradually reduced while the shock absorber111is compressed. Then, at the time T3, at which the shock absorber111of the vehicle100is the most compressed, the compression speed of the shock absorber111becomes zero.

FIG.7is a graph illustrating the damping force during the compression of the shock absorber when the shock absorber is operated as illustrated inFIG.5. A horizontal axis T illustrated inFIG.7represents the time. A vertical axis DF illustrated inFIG.7represents the damping force of the shock absorber111during the compression.

The damping force of the shock absorber111corresponds to a function of the compressed/extended speed of the shock absorber111. Thus, in the case where the damping force characteristic of the shock absorber111is not changed, a waveform that represents the damping force of the shock absorber111during the compression is the same as a waveform that represents the compression speed of the shock absorber111. More specifically, when the vehicle100lands on the road surface120at the time T2and the compression speed of the shock absorber111is increased, the damping force of the shock absorber111during the compression is also increased. Then, when the compression speed of the shock absorber111starts being reduced, the damping force of the shock absorber111during the compression is also reduced. At the time T3, at which the shock absorber111of the vehicle100is the most compressed, the damping force of the shock absorber111during the compression becomes zero.

As illustrated inFIG.5toFIG.7, in the case where the maximum stroke of the shock absorber111is suppressed without changing the damping force characteristic of the shock absorber111, as described above, the shock absorber may become too stiff. As a result, when the vehicle100lands on the ground, the instantaneous shock may be transmitted to the occupant, which may worsen the riding comfort of the occupant. For example, in the case where the damping force of the shock absorber111becomes larger than a prescribed damping force DF1illustrated inFIG.7, the instantaneous shock may be transmitted to the occupant during landing on the vehicle100, which may worsen the riding comfort of the occupant.

As described above, in the landing damping force control that is executed after landing of the vehicle100, the control section4of the controller1according to this embodiment restricts the damping force of the shock absorber111during the compression to be equal to or smaller than the prescribed damping force DF1. Then, when the vehicle100that has jumped lands on the ground, the control section4suppresses the shock absorber111from becoming too stiff, suppresses the instantaneous shock from being transmitted to the occupant, and thereby improves the riding comfort of the occupant in comparison with the background art. As will be described later inFIG.8, in the landing damping force control, the control section4of the controller1suppresses the increase in the stroke of the shock absorber111, which is caused by the restriction of the damping force of the shock absorber111during the compression and thereby further improves the riding comfort of the occupant at the time when the vehicle100lands on the ground.

FIG.8is a graph illustrating the damping force of the shock absorber during the compression in the case where the vehicle according to the embodiment of the present invention performs the operation illustrated inFIG.4and the controller mounted to the vehicle executes the landing damping force control. A horizontal axis T illustrated inFIG.8represents the time. A vertical axis DF illustrated inFIG.8represents the damping force of the shock absorber111during the compression. InFIG.8, the damping force of the shock absorber111during the compression in the case where the damping force characteristic of the shock absorber111is not changed, that is, the waveform illustrated inFIG.7is also indicated by a two-dot chain line.

As illustrated inFIG.8, in the landing damping force control that is executed after landing of the vehicle100, the control section4of the controller1according to this embodiment controls the damping force characteristic of the shock absorber111such that the damping force of the shock absorber111during the compression approximates a target damping force DF2that is a damping force equal to or smaller than the prescribed damping force DF1. By controlling the damping force characteristic of the shock absorber111as in this embodiment, when the vehicle100that has jumped lands on the ground, the damping force of the shock absorber111during the compression can be restricted to be equal to or smaller than the prescribed damping force DF1. In this way, it is possible to suppress the instantaneous shock from being transmitted to the occupant.

In addition, by controlling the damping force characteristic of the shock absorber111as in this embodiment, as illustrated inFIG.8, in a region where the damping force of the shock absorber111during the compression is relatively small, the damping force of the shock absorber111during the compression can be increased to be larger than that in the case where the damping force characteristic of the shock absorber111is not changed. Furthermore, by controlling the damping force characteristic of the shock absorber111as in this embodiment, as illustrated inFIG.8, in a region where the damping force of the shock absorber111during the compression is relatively large, the damping force of the shock absorber111during the compression can be reduced to be smaller than that in the case where the damping force characteristic of the shock absorber111is not changed.

Here, as illustrated inFIG.8, when the damping force characteristic of the shock absorber111is controlled as in this embodiment, in the region where the damping force of the shock absorber111during the compression is relatively large, energy absorbed by the shock absorber111is reduced to be smaller by a magnitude indicated by a region A than that in the case where the damping force characteristic of the shock absorber111is not changed. Meanwhile, as illustrated inFIG.8, when the damping force characteristic of the shock absorber111is controlled as in this embodiment, in the region where the damping force of the shock absorber111during the compression is relatively small, the energy absorbed by the shock absorber111can be increased to be larger by a magnitude indicated by a region B1and a region B2than that in the case where the damping force characteristic of the shock absorber111is not changed. Accordingly, by controlling the damping force characteristic of the shock absorber111as in this embodiment, it is possible to suppress the increase in the stroke of the shock absorber111, which is caused by the restriction of the damping force of the shock absorber111during the compression and to further improve the riding comfort of the occupant at the time when the vehicle100lands on the ground.

The above-described landing damping force control for controlling the damping force characteristic of the shock absorber111such that the damping force of the shock absorber111approximates the target damping force DF2can also be implemented by a method for changing the damping force characteristic of the shock absorber111in a stepless manner. However, in this embodiment, the method for changing the damping force characteristic of the shock absorber111stepwise is adopted. This is because, when the damping force characteristic is changed, a formula, a map, or the like that is used to calculate the damping force of the shock absorber111from the compressed/extended speed of the shock absorber111is changed. In addition, in the case where the damping force characteristic is changed, the compressed/extended speed of the shock absorber111is also changed. Accordingly, as the number of changes of the damping force characteristic of the shock absorber111is increased, work of calculating the damping force of the shock absorber111becomes more complicated. Accordingly, compared to the method for changing the damping force characteristic of the shock absorber111in the stepless manner, the method for changing the damping force characteristic of the shock absorber111stepwise can suppress the number of the changes of the damping force characteristic of the shock absorber111. As a result, the damping force of the shock absorber111can be controlled easily.

A detailed description will hereinafter be made on the method for changing the damping force characteristic of the shock absorber111stepwise. Here, for the description of the method, the damping force characteristic of the shock absorber111in a state before the jump detecting section3detects the jump of the vehicle100is set as a first damping force characteristic C1.

In the landing damping force control that is executed after landing of the vehicle100, in a state where the compression speed of the shock absorber111is lower than a prescribed speed, the control section4of the controller1according to this embodiment sets the damping force characteristic of the shock absorber111to a second damping force characteristic C2that is harder than the first damping force characteristic C1. That is, in the case where the compression speed of the shock absorber111is the same, the damping force of the shock absorber111with the second damping force characteristic C2is larger than the damping force of the shock absorber111with the first damping force characteristic C1. InFIG.8, in a period from the time T2to time T4and a period from time T5to the time T3, the compression speed of the shock absorber111is lower than the prescribed speed. In addition, in this embodiment, in all the periods in which the compression speed of the shock absorber111is lower than the prescribed speed, the damping force characteristic of the shock absorber111is the second damping force characteristic C2. In at least a part of any of the periods in which the compression speed of the shock absorber111is lower than the prescribed speed, it is possible to suppress the increase in the stroke of the shock absorber111, which is caused by the restriction of the damping force of the shock absorber111during the compression, as long as the damping force characteristic of the shock absorber111is the second damping force characteristic C2.

In the landing damping force control that is executed after landing of the vehicle100, in a state where the compression speed of the shock absorber111is equal to or higher than the prescribed speed, the control section4of the controller1according to this embodiment sets the damping force characteristic of the shock absorber111to a third damping force characteristic C3that is softer than the second damping force characteristic C2. That is, in the case where the compression speed of the shock absorber111is the same, the damping force of the shock absorber111with the third damping force characteristic C3is smaller than the damping force of the shock absorber111with the second damping force characteristic C2. InFIG.8, in a period from the time T4to the time T5, the compression speed of the shock absorber111is equal to or higher than the prescribed speed. That is, inFIG.8, in the period from the time T4to the time T5, the damping force characteristic of the shock absorber111is the third damping force characteristic C3. Timing at which the damping force characteristic of the shock absorber111is set to the third damping force characteristic C3may be timing before the compression speed of the shock absorber111becomes equal to or higher than the prescribed speed. In addition, timing at which the damping force characteristic of the shock absorber111is changed from the third damping force characteristic C3to another damping force characteristic may be timing after the compression speed of the shock absorber111becomes smaller than the prescribed speed.

When the damping force characteristic of the shock absorber111is changed stepwise, just as described, the damping force characteristic of the shock absorber111can be controlled in the manner to approximate the target damping force DF2. By the way, the control section4may change the damping force characteristic that is changed to the second damping force characteristic C2according to the period during the single landing damping force control. Similarly, the control section4may change the damping force characteristic that is changed to the third damping force characteristic C3according to the period during the single landing damping force control. However, in this embodiment, during the single landing damping force control, the control section4uses the single damping force characteristic as the second damping force characteristic C2and uses the single damping force characteristic as the third damping force characteristic C3. That is, in this embodiment, the control section4is configured to output the command signal with a constant value at the time of setting the second damping force characteristic C2during the single landing damping force control. In addition, the control section4is configured to output the command signal with the constant value at the time of setting the third damping force characteristic C3during the single landing damping force control. This is because, as described above, the damping force of the shock absorber111can be controlled easily as the number of the changes of the damping force characteristic of the shock absorber111is reduced.

Here, the controller1according to this embodiment can receive the signal corresponding to the speed of the vehicle100from the signal output device115. That is, the controller1according to this embodiment can grasp the speed of the vehicle100. In such a case, at least for each time of the landing damping force control, the control section4preferably changes the damping force characteristic used as the second damping force characteristic C2and the damping force characteristic used as the third damping force characteristic C3according to the speed of the vehicle100. This is because the kinetic energy at the time of landing of the vehicle100differs by the speed of the vehicle100. Accordingly, at least for each time of the landing damping force control, the damping force characteristic used as the second damping force characteristic C2and the damping force characteristic used as the third damping force characteristic C3are changed according to the speed of the vehicle100. In this way, it is possible to use the further preferred damping force characteristic as each of the second damping force characteristic C2and the third damping force characteristic C3and to further improve the riding comfort of the occupant at the time of landing of the vehicle100.

The compression speed of the shock absorber111can be calculated by any of various methods.

For example, the controller1according to this embodiment includes the unsprung acceleration sensor116that detects the vertical acceleration of the unsprung portion of the vehicle100. In the case where vertical motion of the vehicle body101as a sprung portion of the vehicle100and vertical motion of the unsprung portion are compared after landing of the vehicle100, the vertical motion of the vehicle body101is slower than the vertical motion of the unsprung portion. Accordingly, it is possible to calculate the rough relative distance between the vehicle body101and the unsprung portion from the detection value of the unsprung acceleration sensor116. That is, it is possible to calculate the rough stroke of the shock absorber111from the detection value of the unsprung acceleration sensor116and to calculate the rough compression speed of the shock absorber111.

More specifically, in this embodiment, the control section4calculates the compression speed of the shock absorber111as follows on the basis of the detection value of the unsprung acceleration sensor116. As described with reference toFIG.6, in a compression process of the shock absorber111after landing of the vehicle100, after the compression speed of the shock absorber111is increased, the compression speed of the shock absorber111is reduced. That is, in the compression process of the shock absorber111after landing of the vehicle100, there is a state where compression acceleration of the shock absorber111becomes the maximum while the compression speed of the shock absorber111is increased. In this embodiment, the state where the compression acceleration of the shock absorber111becomes the maximum is calculated from the detection value of the unsprung acceleration sensor116.

Further more specifically, in this embodiment, the control section4differentiates the detection value of the unsprung acceleration sensor116so as to detect a state where a sign of jerk is changed from positive to negative. This state corresponds to the state where the compression acceleration of the shock absorber111becomes the maximum. In the compression process of the shock absorber111after landing of the vehicle100, in the case where a state before the compression speed of the shock absorber111becomes the prescribed speed can be detected, it is possible to estimate that the compression speed of the shock absorber111becomes equal to or higher than the prescribed speed after first prescribed time from the state. In addition, in the case where the state before the compression speed of the shock absorber111becomes the prescribed speed can be detected, it is possible to estimate that the compression speed of the shock absorber111becomes lower than the prescribed speed after second prescribed time from the state that is later than the first prescribed time.

Here, the control section4preferably changes the above-described first prescribed time and second prescribed time according to the speed of the vehicle100. This is because the kinetic energy at the time of landing of the vehicle100differs by the speed of the vehicle100and thus a magnitude of the change in the compression speed of the shock absorber111from the state of the shock absorber111calculated from the detection value of the unsprung acceleration sensor116varies. Accordingly, it is possible to further accurately estimate the compression speed of the shock absorber111by changing the above-described first prescribed time and second prescribed time according to the speed of the vehicle100.

In the case where the vehicle100includes the vertical acceleration sensor that detects the vertical acceleration of the vehicle body101, the relative distance between the vehicle body101and the unsprung portion can be calculated on the basis of the detection value of the vertical acceleration sensor and the detection value of the unsprung acceleration sensor116. That is, it is possible to calculate the stroke of the shock absorber111and the compression speed of the shock absorber111on the basis of the detection value of the vertical acceleration sensor and the detection value of the unsprung acceleration sensor116. In this case, for example, the control section4may differentiate the stroke of the shock absorber111to directly calculate the compression speed of the shock absorber111.

When the compression speed of the shock absorber111is calculated on the basis of the detection value of the vertical acceleration sensor and the detection value of the unsprung acceleration sensor116, it is possible to further accurately calculate the compression speed of the shock absorber111. Meanwhile, when the compression speed of the shock absorber111is calculated only on the basis of the detection value of the unsprung acceleration sensor116, the control configuration can be simplified.

In the case where the vehicle100includes the stroke sensor that measures the relative distance between the vehicle body101and the unsprung portion, it is possible to calculate the stroke of the shock absorber111on the basis of the detection value of the stroke sensor and to calculate the compression speed of the shock absorber111. In this case, for example, the control section4may differentiate the stroke of the shock absorber111to directly calculate the compression speed of the shock absorber111. However, as described above, in the case where the stroke sensor is used for the off-road vehicle, the failure of the stroke sensor is concerned. For this reason, the vehicle100is configured not to use the stroke sensor. In this way, it is possible to improve the durability of the vehicle100.

<Operation of Controller>

Next, a description will be made on operation of the controller1.

FIG.9is a flowchart illustrating the operation of the controller according to the embodiment of the present invention.

When a control initiation condition is satisfied, in step S10, the controller1initiates the control illustrated inFIG.9. The control initiation condition is that an engine of the vehicle100is started, or the like. Step S20is a jump detection step. In step S20, the jump detecting section3of the controller1determines whether the vehicle100has jumped. The jump detecting section3repeats the jump detection step in step S20until determining that the vehicle100has jumped, in other words, until detecting that the vehicle100has jumped. When the jump detecting section3detects the jump of the vehicle100, the processing of the controller1proceeds to step S30.

Step S30is a landing damping force control step. In step S30, the control section4of the controller1executes the control for restricting the damping force of the shock absorber111during the compression to be equal to or smaller than the prescribed damping force DF1. That is, in step S30, the control section4executes the landing damping force control. In this embodiment, in the landing damping force control step in step S30, the control section4executes step S31to step S36and controls the damping force characteristic of the shock absorber111stepwise such that the damping force of the shock absorber111during the compression approximates the target damping force DF2that is the damping force equal to or smaller than the prescribed damping force DF1. A specific description will hereinafter be made on step S31to step S36.

Step S31is a damping force characteristic hardening changing step. In step S31, the control section4changes the damping force characteristic of the shock absorber111from the first damping force characteristic C1to the second damping force characteristic C2, which is harder than the first damping force characteristic C1. Step S32after step S31is a damping force characteristic change determination step. In step S32, the control section4determines whether timing to change the damping force characteristic of the shock absorber111from the second damping force characteristic C2to the third damping force characteristic C3has arrived. The control section4repeats step S32until the timing to change the damping force characteristic of the shock absorber111from the second damping force characteristic C2to the third damping force characteristic C3arrives. In the case where the timing to change the damping force characteristic of the shock absorber111from the second damping force characteristic C2to the third damping force characteristic C3has arrived, the processing proceeds to step S33.

Step S33is a damping force characteristic softening changing step. In step S33, the control section4changes the damping force characteristic of the shock absorber111from the second damping force characteristic C2to the third damping force characteristic C3, which is softer than the second damping force characteristic C2. Step S34after step S33is the damping force characteristic change determination step. In step S34, the control section4determines whether timing to change the damping force characteristic of the shock absorber111from the third damping force characteristic C3to the second damping force characteristic C2has arrived. The control section4repeats step S34until the timing to change the damping force characteristic of the shock absorber111from the third damping force characteristic C3to the second damping force characteristic C2arrives. In the case where the timing to change the damping force characteristic of the shock absorber111from the third damping force characteristic C3to the second damping force characteristic C2has arrived, the processing proceeds to step S35.

Step S35is the damping force characteristic hardening changing step. In step S35, the control section4changes the damping force characteristic of the shock absorber111from the third damping force characteristic C3to the second damping force characteristic C2, which is harder than the third damping force characteristic C3. Step S36after step S35is a termination determination step. In step S36, the control section4determines whether to terminate the landing damping force control. The control section4repeats step S36until determining to terminate the landing damping force control. When the control section4determines to terminate the landing damping force control, processing proceeds to step S40, and the control section4terminates the control illustrated inFIG.9. A condition that the control section4determines to terminate the landing damping force control is termination of the first compression process of the shock absorber111after the jump detecting section3detects the jump of the vehicle100, for example.

<Effects of Controller>

The controller1according to this embodiment is mounted to the vehicle100, which includes the shock absorber111in the damping force adjustment type between the vehicle body101and the wheel103, and controls the damping force of the shock absorber111. The controller1includes the jump detecting section3and the control section4. The jump detecting section3detects that the vehicle100has jumped. When the jump detecting section3detects the jump of the vehicle100, the control section4executes the landing damping force control to restrict the damping force of the shock absorber111during the compression to be equal to or smaller than the prescribed damping force DF1.

As described above, with the controller1that is configured as described above, it is possible to suppress the instantaneous shock caused by the maximum stroke of the shock absorber111and is also possible to suppress the instantaneous shock caused by the shock absorber111that is too stiff when the vehicle100that has jumped lands on the ground. Therefore, with the controller1that is configured as described above, it is possible to improve the riding comfort of the occupant at the time of landing of the vehicle100in comparison with the background art.

Preferably, the control section4of the controller1is configured to control the damping force characteristic of the shock absorber111such that the damping force of the shock absorber111during the compression approximates the target damping force DF2that is the damping force equal to or smaller than the prescribed damping force DF1in the landing damping force control.

With the controller1that is configured as described above, it is possible to suppress the increase in the stroke of the shock absorber111, which is caused by the restriction of the damping force of the shock absorber111during the compression, and to thereby further improve the riding comfort of the occupant at the time of landing of the vehicle100.

Preferably, the control section4of the controller1is configured to control the damping force characteristic of the shock absorber111as follows in the landing damping force control for controlling the damping force characteristic of the shock absorber111such that the damping force of the shock absorber111approximates the target damping force DF2. The damping force characteristic of the shock absorber111in the state before the jump detecting section3detects the jump of the vehicle100is set as the first damping force characteristic C1. In this case, in the landing damping force control, in at least the part of any of the periods in which the compressed speed of the shock absorber111is lower than the prescribed speed, the control section4sets the damping force characteristic of the shock absorber111to the second damping force characteristic C2that is harder than the first damping force characteristic C1. In addition, in the landing damping force control, in the state where the compression speed of the shock absorber111is equal to or higher than the prescribed speed, the control section4sets the damping force characteristic of the shock absorber111to the third damping force characteristic C3that is softer than the second damping force characteristic C2.

The damping force characteristic of the shock absorber111is changed stepwise as described above. In this way, compared to the case where the damping force characteristic of the shock absorber111is changed in the stepless manner, it is possible to suppress the number of the changes of the damping force characteristic of the shock absorber111. As a result, the damping force of the shock absorber111can be controlled easily.

Preferably, the control section4is configured to output the command signal at the constant value when changing the damping force characteristic of the shock absorber111stepwise to the second damping force characteristic C2. In addition, the control section4is configured to output the command signal at the constant value when changing the damping force characteristic of the shock absorber111stepwise to the third damping force characteristic C3.

When the controller1is configured as described above, it is possible to further suppress the number of the changes of the damping force characteristic of the shock absorber111and to control the damping force of the shock absorber111easily.

Preferably, the vehicle100, to which the controller1is mounted, is the off-road vehicle. The travel of the off-road vehicle including the jump can easily be assumed. Therefore, the controller1capable of improving the riding comfort of the occupant at the time when the vehicle100lands on the ground is preferably mounted to the off-road vehicle.

The description has been made so far on the controller1according to this embodiment. However, the controller according to the present invention is not limited to that in the description of this embodiment, and only a part of this embodiment may be implemented.

REFERENCE SIGNS LIST

1: Controller2: Receiving section3: Jump detecting section4: Control section100: Vehicle101: Vehicle body103: Wheel103FL: Front left wheel103FR: Front right wheel103RL: Rear left wheel103RR: Rear right wheel110(110FL,110FR,110RL,110RR): Spring111(111FL,111FR,111RL,111RR): Shock absorber112(112FL,112FR,112RL,112RR): Actuator113: Longitudinal acceleration sensor114: Lateral acceleration sensor115: Signal output device116(116FL,116FR,116RL,116RR): Unsprung acceleration sensor120: Road surface