Suspension device

1. A suspension device comprising:

a spring provided between an upper member and a lower member;

a motor provided in juxtaposition with the spring to generate power in accordance with a speed at which a movable shaft is operated, the movable shaft being movable in accordance with operations of the upper member and the lower member in an expansion-contraction direction of the spring;

a power consumption circuit including a variable load circuit, the variable load circuit being configured to generate a damping force in the motor by consuming the power generated in the motor and to change the damping force; and

an electronic control unit configured to control the variable load circuit such that consumed power by the variable load circuit is increased along with an increase in a speed of the movable shaft, wherein

the electronic control unit is configured to maintain a resistance value of the variable load circuit to a specified value when the speed of the movable shaft is equal to or lower than a specified speed.

2. A suspension device comprising:

a spring provided between an upper member and a lower member;

a motor provided in juxtaposition with the spring to generate power in accordance with a speed at which a movable shaft is operated, the movable shaft being movable in accordance with operations of the upper member and the lower member in an expansion-contraction direction of the spring;

a power consumption circuit including a variable load circuit, the variable load circuit being configured to generate a damping force in the motor by consuming the power generated in the motor and to change the damping force; and

an electronic control unit configured to control the variable load circuit such that consumed power by the variable load circuit is increased along with an increase in a speed of the movable shaft, wherein

the electronic control unit has a conversion table that indicates a relationship between the speed of the movable shaft and a resistance value of the variable load circuit, and is configured to output a load resistance value setting signal based on refer the conversion table, the load resistance value setting signal being used to set the resistance value of the variable load circuit to a value corresponding to the speed of the movable shaft.

3. A suspension device comprising:

a spring provided between an upper member and a lower member;

a motor provided in juxtaposition with the spring to generate power in accordance with a speed at which a movable shaft is operated, the movable shaft being movable in accordance with operations of the upper member and the lower member in an expansion-contraction direction of the spring;

a power consumption circuit including a variable load circuit, the variable load circuit being configured to generate a damping force in the motor by consuming the power generated in the motor and to change the damping force; and

an electronic control unit configured to control the variable load circuit such that consumed power by the variable load circuit is increased along with an increase in a speed of the movable shaft, wherein

the variable load circuit has: a load resistor that has a predetermined resistance value; and a switch connected in series with the load resistor, and

the electronic control unit is configured to generate a pulse width modulation signal such that a duty ratio is reduced as a resistance value of the variable load circuit is increased, the pulse width modulation signal being used to switch an opened-closed state of the switch.

4. A suspension device comprising:

a spring provided between an upper member and a lower member;

a motor provided in juxtaposition with the spring to generate power in accordance with a speed at which a movable shaft is operated, the movable shaft being movable in accordance with operations of the upper member and the lower member in an expansion-contraction direction of the spring;

a power consumption circuit including a variable load circuit, the variable load circuit being configured to generate a damping force in the motor by consuming the power generated in the motor and to change the damping force; and

an electronic control unit configured to control the variable load circuit such that consumed power by the variable load circuit is increased along with an increase in a speed of the movable shaft, wherein

the electronic control unit is configured to switch an operation between a first operation mode and a second operation mode in accordance with a mode switching signal provided from outside, and

the electronic control unit is configured to,

in the first operation mode, control a resistance value of the variable load circuit such that the resistance value of the variable load circuit is increased along with an increase in the speed of the movable shaft, and

in the second operation mode, control the resistance value of the variable load circuit such that the damping force in the variable load circuit becomes the largest for the speed of the movable shaft.

5. The suspension device according to claim 4 , wherein

the electronic control unit has: a first conversion table that indicates a relationship between the speed of the movable shaft and the resistance value of the variable load circuit, the first conversion table being provided for the first operation mode; a second conversion table that indicates a relationship between the speed of the movable shaft and the resistance value of the variable load circuit, the second conversion table being provided for the second operation mode; and

the electronic control unit is configured to read a duty ratio setting value used to realize the speed of the movable shaft and the resistance value of the variable load circuit from either one of the first conversion table and the second conversion table in accordance with the mode switching signal and to generate a pulse width modulation signal with the duty ratio that corresponds to the read duty ratio setting value.

6. A suspension device comprising:

a spring provided between an upper member and a lower member;

a motor provided in juxtaposition with the spring to generate power in accordance with a speed at which a movable shaft is operated, the movable shaft being movable in accordance with operations of the upper member and the lower member in an expansion-contraction direction of the spring;

a power consumption circuit including a variable load circuit, the variable load circuit being configured to generate a damping force in the motor by consuming the power generated in the motor and to change the damping force; and

an electronic control unit configured to control the variable load circuit such that consumed power by the variable load circuit is increased along with an increase in a speed of the movable shaft, wherein

the electronic control unit is configured to generate a load resistance value setting signal including a duty ratio that corresponds to the speed of the movable shaft, and

the variable load circuit includes: a buck-boost circuit that is configured to steps up or steps down a motor voltage generated in the motor based on of the load resistance value setting signal to generate an output voltage with a constant voltage value; and a secondary battery, to which the output voltage is applied, and to which regenerative power generated in the motor is stored.

7. The suspension device according to claim 6 , wherein

the duty ratio of the load resistance value setting signal is set such that the damping force generated by the variable load circuit by consuming the power generated in the motor becomes a target damping force.