Header height control with closed center pump

摘要

An agricultural combine (100) has a header height control circuit supplied with hydraulic fluid from a closed center pump (110). The pump (110) has a variable displacement that is controlled by a control line (200) connected to the pump (110). The control line (200) is supplied with fluid from the feederhouse lift cylinders (114) that passes through a valve (206). The valve (206) supplies hydraulic fluid from the feederhouse lift cylinders (114) to the control line (200) of the pump (110). Upon receiving fluid from the valve (206) the closed center pump (110) rapidly changes its outlet pressure to match the pressure in the feederhouse lift cylinders (114) and thus reduces the response time of the closed center pump (110).