A steering assist system for a hybrid vehicle capable of being driven by both of an engine and a drive motor, including a first assist portion and a second assist portion configured to assist a steering force respectively utilizing the engine and an electric motor each as a drive source, wherein the steering force is assisted only by the second assist portion in a motor-driven state in which the vehicle is driven only by the drive motor, and wherein the steering assist system is configured to, upon occurrence of a failure of the second assist portion in the motor-driven state, drive the engine, execute assist switching from an assist by the second assist portion to an assist by the first assist portion, and gradually increase, in the assist switching, an assist force by the first assist portion up to a set assist force when the vehicle is being steered.

A power steering system for a vehicle, the power steering system comprising a power steering pump, an electrical machine unit, a clutch arrangement and a power steering control system configured to control the power steering system, wherein the electrical machine unit is configured to drive the power steering pump and to be operatively connected to and powered by an energy storage of the vehicle, and the power steering pump is configured to be connected to a torque output source arranged downstream of a transmission system of the vehicle, the power steering pump being configured to be driven by means of torque provided by the torque output source.

A power steering system for a vehicle, the power steering system comprising a power steering pump, an electrical machine unit, a clutch arrangement and a power steering control system configured to control the power steering system, wherein the electrical machine unit is configured to drive the power steering pump and to be operatively connected to and powered by an energy storage of the vehicle, and the power steering pump is configured to be connected to a torque output source arranged downstream of a transmission system of the vehicle, the power steering pump being configured to be driven by means of torque provided by the torque output source.

Self-propelled vehicles that include swiveling caster wheels and independent drive wheels are disclosed. The self-propelled vehicles are selectively steered in a caster wheel steering mode or a drive wheel steering mode. The vehicle includes a steering position sensor to measure the position of the steering system. A control unit varies the rotational speed of first and second drive wheels based at least in part of the signal from the steering position sensor.

Self-propelled vehicles that include swiveling caster wheels and independent drive wheels are disclosed. The self-propelled vehicles are selectively steered in a caster wheel steering mode or a drive wheel steering mode. The vehicle includes a steering position sensor to measure the position of the steering system. A control unit varies the rotational speed of first and second drive wheels based at least in part of the signal from the steering position sensor.

A hydraulic drive system (1) including a meter-in compensator (37) and a bleed-off compensator (42) comprises a plurality of sensors (64 to 68), a controller (62), and an outlet pressure switching valve (61). The controller (62) determines whether or not the state of a wheel loader (2) which is detected based on the signals output from the sensors (64 to 68) meets a predetermined steering limiting condition. When the controller (62) determines that the state of the wheel loader (2) meets the steering limiting condition, it outputs a command signal to the outlet pressure switching valve (61). The outlet pressure switching valve (61) reduces the flow rate of the hydraulic oil flowing to steering cylinders (18L, 18R), in response to the command signal in such a manner that the flow rate becomes lower than that corresponding to the operation amount of a handle of a steering device (35).

A hydraulic drive system (1) including a meter-in compensator (37) and a bleed-off compensator (42) comprises a plurality of sensors (64 to 68), a controller (62), and an outlet pressure switching valve (61). The controller (62) determines whether or not the state of a wheel loader (2) which is detected based on the signals output from the sensors (64 to 68) meets a predetermined steering limiting condition. When the controller (62) determines that the state of the wheel loader (2) meets the steering limiting condition, it outputs a command signal to the outlet pressure switching valve (61). The outlet pressure switching valve (61) reduces the flow rate of the hydraulic oil flowing to steering cylinders (18L, 18R), in response to the command signal in such a manner that the flow rate becomes lower than that corresponding to the operation amount of a handle of a steering device (35).

The present invention relates to a hydraulic steering system for a vehicle, in particular an industrial truck, comprising: a steering cylinder having two chambers and a hydraulic connection at each of the two chambers for activating a steering movement of at least one wheel of the vehicle; at least one hydraulic pump; at least one hydraulic tank for receiving hydraulic oil; and a steering block which comprises: two first hydraulic connections for connecting to the two hydraulic connections of the steering cylinder; at least two second hydraulic connections for supplying hydraulic oil from the hydraulic pump to the steering block and feeding the hydraulic oil back into the hydraulic tank; and a controllable valve assembly which receives control signals from a steering angle detection device and is designed to convey hydraulic oil to the steering cylinder on the basis of said control signals; the controllable valve assembly being further designed to be shiftable into at least one neutral position in which it allows a flow of hydraulic oil between the two chambers of the steering cylinder. The hydraulic steering system further comprises a pump device which is designed to stimulate the flow of hydraulic oil between the two chambers of the steering cylinder when the valve assembly is in the neutral position.

The present invention relates to a hydraulic steering system for a vehicle, in particular an industrial truck, comprising: a steering cylinder having two chambers and a hydraulic connection at each of the two chambers for activating a steering movement of at least one wheel of the vehicle; at least one hydraulic pump; at least one hydraulic tank for receiving hydraulic oil; and a steering block which comprises: two first hydraulic connections for connecting to the two hydraulic connections of the steering cylinder; at least two second hydraulic connections for supplying hydraulic oil from the hydraulic pump to the steering block and feeding the hydraulic oil back into the hydraulic tank; and a controllable valve assembly which receives control signals from a steering angle detection device and is designed to convey hydraulic oil to the steering cylinder on the basis of said control signals; the controllable valve assembly being further designed to be shiftable into at least one neutral position in which it allows a flow of hydraulic oil between the two chambers of the steering cylinder. The hydraulic steering system further comprises a pump device which is designed to stimulate the flow of hydraulic oil between the two chambers of the steering cylinder when the valve assembly is in the neutral position.

A steering system includes a user-manipulable steering control, a steering actuator, a pump, and a first valve assembly configured to control a flow of fluid from the pump to the steering actuator in response to manipulation of the steering control. The steering system also includes a rotary device coupled to the steering control. The rotary device is configured to direct fluid in response to manipulation of the steering control. The steering system further includes a second valve assembly movable between a first position in which the rotary device is not in fluid communication with the steering actuator and a second position in which the second valve assembly fluidly communicates the rotary device with the steering actuator.