POWER STEERING APPARATUS
First Claim
1. A power steering apparatus comprising:
- a steering-assist hydraulic power cylinder having a first hydraulic chamber and a second hydraulic chamber divided by a piston;
a reversible pump configured to selectively supply working fluid to either one of the first and second hydraulic chambers of the power cylinder, while producing a pump pressure by pressurizing the working fluid;
a controller configured to control a driving state of the pump; and
a hydraulic circuit comprising;
(a) a first hydraulic line provided to connect the first hydraulic chamber and a first port of the pump, and cooperated with the first hydraulic chamber to construct a first hydraulic pressure transmission path through which the pump pressure is transmitted to a first pressure-receiving surface of the piston facing the first hydraulic chamber;
(b) a second hydraulic line provided to connect the second hydraulic chamber and a second port of the pump, and cooperated with the second hydraulic chamber to construct a second hydraulic pressure transmission path through which the pump pressure is transmitted to a second pressure-receiving surface of the piston facing the second hydraulic chamber; and
(c) a variable volume section disposed in each of the first and second hydraulic pressure transmission paths, a volume of the variable volume section being elastically varied responsively to a hydraulic pressure change in the associated hydraulic pressure transmission path,wherein each of an apparent modulus of volume elasticity of working fluid in the first hydraulic pressure transmission path and an apparent modulus of volume elasticity of working fluid in the second hydraulic pressure transmission path is set to a value greater than or equal to 100 MPa, the apparent modulus of volume elasticity of working fluid in the first hydraulic pressure transmission path corresponding to a ratio of a hydraulic pressure change in the first hydraulic pressure transmission path to a rate of change in working fluid quantity in the first hydraulic pressure transmission path, the working fluid quantity change in the first hydraulic pressure transmission path including a change in volume of the first hydraulic pressure transmission path itself, occurring due to the hydraulic pressure change in the first hydraulic pressure transmission path, and the apparent modulus of volume elasticity of working fluid in the second hydraulic pressure transmission path corresponding to a ratio of a hydraulic pressure change in the second hydraulic pressure transmission path to a rate of change in working fluid quantity in the second hydraulic pressure transmission path, the working fluid quantity change in the second hydraulic pressure transmission path including a change in volume of the second hydraulic pressure transmission path itself, occurring due to the hydraulic pressure change in the second hydraulic pressure transmission path.
1 Assignment
0 Petitions
Accused Products
Abstract
In a hydraulic power cylinder equipped power steering apparatus, a part of each of first and second hydraulic lines, associated with respective hydraulic chambers of the power cylinder, is constructed by a low-rigidity line functioning as a variable volume hydraulic-line section and formed of an elastically-deformable, flexible tube, made of a synthetic rubber. The line length of the low-rigidity line, which is disposed in each of the first and second hydraulic lines, is dimensioned so that each of an apparent modulus Ke of volume elasticity of working fluid in a first hydraulic pressure transmission path and an apparent modulus Ke of volume elasticity of working fluid in a second hydraulic pressure transmission path is set within a specified apparent volume modulus range, defined by an inequality 100 MPa≦Ke≦300 MPa.
12 Citations
19 Claims
-
1. A power steering apparatus comprising:
-
a steering-assist hydraulic power cylinder having a first hydraulic chamber and a second hydraulic chamber divided by a piston; a reversible pump configured to selectively supply working fluid to either one of the first and second hydraulic chambers of the power cylinder, while producing a pump pressure by pressurizing the working fluid; a controller configured to control a driving state of the pump; and a hydraulic circuit comprising; (a) a first hydraulic line provided to connect the first hydraulic chamber and a first port of the pump, and cooperated with the first hydraulic chamber to construct a first hydraulic pressure transmission path through which the pump pressure is transmitted to a first pressure-receiving surface of the piston facing the first hydraulic chamber; (b) a second hydraulic line provided to connect the second hydraulic chamber and a second port of the pump, and cooperated with the second hydraulic chamber to construct a second hydraulic pressure transmission path through which the pump pressure is transmitted to a second pressure-receiving surface of the piston facing the second hydraulic chamber; and (c) a variable volume section disposed in each of the first and second hydraulic pressure transmission paths, a volume of the variable volume section being elastically varied responsively to a hydraulic pressure change in the associated hydraulic pressure transmission path, wherein each of an apparent modulus of volume elasticity of working fluid in the first hydraulic pressure transmission path and an apparent modulus of volume elasticity of working fluid in the second hydraulic pressure transmission path is set to a value greater than or equal to 100 MPa, the apparent modulus of volume elasticity of working fluid in the first hydraulic pressure transmission path corresponding to a ratio of a hydraulic pressure change in the first hydraulic pressure transmission path to a rate of change in working fluid quantity in the first hydraulic pressure transmission path, the working fluid quantity change in the first hydraulic pressure transmission path including a change in volume of the first hydraulic pressure transmission path itself, occurring due to the hydraulic pressure change in the first hydraulic pressure transmission path, and the apparent modulus of volume elasticity of working fluid in the second hydraulic pressure transmission path corresponding to a ratio of a hydraulic pressure change in the second hydraulic pressure transmission path to a rate of change in working fluid quantity in the second hydraulic pressure transmission path, the working fluid quantity change in the second hydraulic pressure transmission path including a change in volume of the second hydraulic pressure transmission path itself, occurring due to the hydraulic pressure change in the second hydraulic pressure transmission path. - View Dependent Claims (2, 3, 4, 5)
-
-
6. A power steering apparatus comprising:
-
a steering-assist hydraulic power cylinder having a first hydraulic chamber and a second hydraulic chamber divided by a piston; a reversible pump configured to selectively supply working fluid to either one of the first and second hydraulic chambers of the power cylinder, while producing a pump pressure by pressurizing the working fluid; a controller configured to control a driving state of the pump; and a hydraulic circuit comprising; (a) a first hydraulic line provided to connect the first hydraulic chamber and a first port of the pump, and cooperated with the first hydraulic chamber to construct a first hydraulic pressure transmission path through which the pump pressure is transmitted to a first pressure-receiving surface of the piston facing the first hydraulic chamber; and (b) a second hydraulic line provided to connect the second hydraulic chamber and a second port of the pump, and cooperated with the second hydraulic chamber to construct a second hydraulic pressure transmission path through which the pump pressure is transmitted to a second pressure-receiving surface of the piston facing the second hydraulic chamber, wherein each of the first and second hydraulic pressure transmission paths comprises a high-rigidity line formed of a steel tube, and a low-rigidity line formed of a flexible tube, which is made of a synthetic rubber, and wherein each of a volume ratio of a volume of the low-rigidity line included in the first hydraulic pressure transmission path to a total volume of the first hydraulic pressure transmission path and a volume ratio of a volume of the low-rigidity line included in the second hydraulic pressure transmission path to a total volume of the second hydraulic pressure transmission path is set to a value less than or equal to 40%. - View Dependent Claims (7, 8, 9)
-
-
10. A power steering apparatus comprising:
-
a steering-assist hydraulic power cylinder having a first hydraulic chamber and a second hydraulic chamber divided by a piston; a reversible pump configured to selectively supply working fluid to either one of the first and second hydraulic chambers of the power cylinder, while producing a pump pressure by pressurizing the working fluid; a controller configured to control a driving state of the pump; and a hydraulic circuit comprising; (a) a first hydraulic line provided to connect the first hydraulic chamber and a first port of the pump, and cooperated with the first hydraulic chamber to construct a first hydraulic pressure transmission path through which the pump pressure is transmitted to a first pressure-receiving surface of the piston facing the first hydraulic chamber; and (b) a second hydraulic line provided to connect the second hydraulic chamber and a second port of the pump, and cooperated with the second hydraulic chamber to construct a second hydraulic pressure transmission path through which the pump pressure is transmitted to a second pressure-receiving surface of the piston facing the second hydraulic chamber, wherein an apparent modulus of volume elasticity of working fluid in the first hydraulic pressure transmission path and an apparent modulus of volume elasticity of working fluid in the second hydraulic pressure transmission path are set to be substantially identical to each other, the apparent modulus of volume elasticity of working fluid in the first hydraulic pressure transmission path corresponding to a ratio of a hydraulic pressure change in the first hydraulic pressure transmission path to a rate of change in working fluid quantity in the first hydraulic pressure transmission path, the working fluid quantity change in the first hydraulic pressure transmission path including a change in volume of the first hydraulic pressure transmission path itself, occurring due to the hydraulic pressure change in the first hydraulic pressure transmission path, and the apparent modulus of volume elasticity of working fluid in the second hydraulic pressure transmission path corresponding to a ratio of a hydraulic pressure change in the second hydraulic pressure transmission path to a rate of change in working fluid quantity in the second hydraulic pressure transmission path, the working fluid quantity change in the second hydraulic pressure transmission path including a change in volume of the second hydraulic pressure transmission path itself, occurring due to the hydraulic pressure change in the second hydraulic pressure transmission path. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
-
Specification