Vehicle height adjustment device

1. A vehicle height adjustment device comprising:

a changer configured to change a relative position of a body of a vehicle relative to an axle of a wheel of the vehicle; and

a controller configured to control the changer to make the relative position a target value so as to control a vehicle height of the body of the vehicle, the controller being configured to control the changer to maintain the relative position irrespective of the target value when a decreasing malfunction occurs causing the vehicle height to decrease;

wherein the changer comprises an actuator driven when supplied with a current and capable of changing the relative position, and

wherein the controller comprises:

an actuator driver configured to drive the actuator, a relay configured to electrically connect the actuator driver and the actuator to each other and break a connection between the actuator driver and the actuator,

a malfunction detector configured to detect the decreasing malfunction, and

a relay driver configured to shut off the relay when the malfunction detector detects the decreasing malfunction

a target current setter configured to set a target current supplied to the actuator in accordance with the target value of the relative position, and

a current detector configured to detect a current supplied to the actuator and

wherein the malfunction detector is configured to determine that the decreasing malfunction has occurred when the target current set by the target current setter is a maintaining current for maintaining the relative position or an increasing current for increasing the relative position and when a detection value detected by the current detector is a decreasing current for decreasing the relative position and

wherein the maintaining current is less than a first reference current, the increasing current is equal to or higher than the first reference current and less than a second reference current, which is set in advance to be higher than the first reference current, and the decreasing current is equal to or higher than the second reference current.

2. The vehicle height adjustment device according to claim 1 , further comprising a relative position detector configured to detect the relative position,

wherein the malfunction detector is configured to determine that the decreasing malfunction has occurred when the target current set by the target current setter is the maintaining current for maintaining the relative position or the increasing current for increasing the relative position and when the detection value detected by the current detector is the decreasing current for decreasing the relative position and when a period of time in which the relative position detected by the relative position detector keeps decreasing is a predetermined period of time.

3. The vehicle height adjustment device according to claim 2 ,

wherein the changer comprises

a spring comprising one end supported on a side of the body and comprising another end supported on a side of the wheel,

an adjustor comprising an accommodation chamber to accommodate a fluid and configured to adjust a length of the spring in accordance with an amount of the fluid in the accommodation chamber,

a storage chamber storing the fluid,

a pump comprising a cylinder and configured to, when a relative distance between the body and the wheel increases, take into the cylinder the fluid stored in the storage chamber and configured to, when the relative distance between the body and the wheel decreases, discharge the fluid from the cylinder, and

the actuator driven when supplied with a current and configured to switch among a state of guiding the fluid discharged from the pump into the accommodation chamber to increase the amount of the fluid in the accommodation chamber, a state of guiding the fluid in the accommodation chamber into the storage chamber to decrease the amount of the fluid in the accommodation chamber, and a state of maintaining the amount of the fluid in the accommodation chamber, and

wherein when the decreasing malfunction of a decrease in the vehicle height occurs, the controller is configured to maintain the state of maintaining the amount of the fluid in the accommodation chamber.

4. The vehicle height adjustment device according to claim 1 ,

wherein the changer comprises

a spring comprising one end supported on a side of the body and comprising another end supported on a side of the wheel,

an adjustor comprising an accommodation chamber to accommodate a fluid and configured to adjust a length of the spring in accordance with an amount of the fluid in the accommodation chamber,

a storage chamber storing the fluid,

a pump comprising a cylinder and configured to, when a relative distance between the body and the wheel increases, take into the cylinder the fluid stored in the storage chamber and configured to, when the relative distance between the body and the wheel decreases, discharge the fluid from the cylinder, and

the actuator driven when supplied with a current and configured to switch among a state of guiding the fluid discharged from the pump into the accommodation chamber to increase the amount of the fluid in the accommodation chamber, a state of guiding the fluid in the accommodation chamber into the storage chamber to decrease the amount of the fluid in the accommodation chamber, and a state of maintaining the amount of the fluid in the accommodation chamber, and

wherein when the decreasing malfunction of a decrease in the vehicle height occurs, the controller is configured to maintain the state of maintaining the amount of the fluid in the accommodation chamber.