Manufacturing method for oil pressure control valve

A manufacturing method for an oil pressure control valve that includes:

• a sleeve that is shaped in a tubular form and has a plurality of oil ports, each of which radially communicates between an inside and an outside of the sleeve, wherein a female threaded portion is formed at one end portion of the sleeve;
• a spool that is received in the sleeve and is configured to slide along an inner wall of the sleeve, wherein the spool opens or closes a corresponding one or more of the plurality of oil ports depending on an axial position of the spool to change an output oil pressure of the oil pressure control valve;
• a drive device that is configured to generate a drive force for moving the spool toward the female threaded portion;
• a spring that is configured to urge the spool in a direction away from the female threaded portion against the drive force;
• and
• an adjustment screw that includes:
• a male threaded portion that is threadably engaged with the female threaded portion of the sleeve;
• and
• a rotation transmitting portion that is a hole which opens at an end surface of the adjustment screw and has a radial cross-section shaped in a non-circular form such that a tool, which has a radial cross-section shaped in a form that corresponds to the non-circular form of the radial cross-section of the rotation transmitting portion, is insertable into the rotation transmitting portion, wherein the adjustment screw is configured to adjust a set load of the spring when the adjustment screw is rotated integrally with the tool inserted into the rotation transmitting portion to change a position of the adjustment screw in an axial direction according to a rotation amount of the adjustment screw, the manufacturing method comprising:
• a pressure adjusting step that includes rotating the adjustment screw by a pressure adjusting device and thereby adjusting the set load of the spring to adjust the output oil pressure of the oil pressure control valve, which is generated under a predetermined drive condition of the drive device, to a target oil pressure, wherein the pressure adjusting step includes:
• a preparing stage that includes placing the tool in contact with an inner wall of the rotation transmitting portion by the pressure adjusting device without forming a gap between the tool and the rotation transmitting portion at least in a rotational direction of the tool;
• an adjustment rotation amount calculating stage that includes:
• sensing a pre-adjustment oil pressure, which is the output oil pressure at a pre-adjustment rotational position of the adjustment screw under the predetermined drive condition, by the pressure adjusting device after the preparing stage;
• and
• thereafter calculating an adjustment rotation amount of the adjustment screw by the pressure adjusting device from the pre-adjustment rotational position of the adjustment screw to a target rotational position of the adjustment screw, which corresponds to the target oil pressure, based on:
• a differential pressure between the pre-adjustment oil pressure and the target oil pressure;
• and
• a correction amount which corresponds to a product characteristic of the oil pressure control valve;
• and
• a rotating stage that includes rotating the adjustment screw by the adjustment rotation amount by the pressure adjusting device.