Hydrostatic transmission

Hydrostatic transmission comprising a main line for a flow of hydraulic fluid;

• said main line having low pressure and high pressure flow sections;
• a pump and a hydraulic motor arranged in said main line;
• an oil drain line of said hydraulic motor being connected with said low pressure section;
• a control valve arranged in said main line upstream of the connection of said oil drain line to said low pressure section for controlling the flow of the hydraulic fluid to said hydraulic motor in response to the hydraulic pressure reigning in said main line, said control valve being a throttling valve (25) having a passage of adjustable cross-section and two ports respectively connected with said pump (2) and said hydraulic motor (3), said control valve reducing the flow of the hydraulic fluid responsive to an increasing pressure or decreasing temperature of the hydraulic fluid;
• a throttling pressure relief valve (22) located in a bypass (21) intermediate said high and low pressure sections (5,6), said control valve cooperating with said throttling pressure relief valve such that the throttling effect of said pressure relief valve reduces with increasing throttling effected by said control valve;
• and a valve body (26) of said control valve (25) being acted upon by an increased throttling effect of the hydraulic pressure in the direction of flow upstream of a throttle (29) arranged in said main line (4).