A hydrostatic drive system for a vehicle (10) comprises an open circuit (100), a closed travel circuit (120), an electronic controller (320), and a main variable displacement hydraulic pump (102) driven by an internal combustion engine (12) equipped with a speed sensor (350). The main variable displ
A hydrostatic drive system for a vehicle (10) comprises an open circuit (100), a closed travel circuit (120), an electronic controller (320), and a main variable displacement hydraulic pump (102) driven by an internal combustion engine (12) equipped with a speed sensor (350). The main variable displacement hydraulic pump may be configured to supply hydraulic fluid to a hydraulic consumer (34, 44, 50) via a hydraulic supply line (106). A pressure relief valve (118) may be connected to a reservoir (300) and may be permanently connected to the hydraulic supply line of the open circuit. The electronic controller may be configured to run a strong braking mode in which the electronic controller at least partially increases the displacement of the main variable displacement hydraulic pump such that hydraulic fluid is discharged via the permanently connected pressure relief valve into the reservoir if the sensed engine speed is higher than a predetermined maximum engine speed.
대표청구항▼
1. A hydrostatic drive system for a vehicle, comprising: an open circuit including: a main variable displacement hydraulic pump configured to be driven by an internal combustion engine equipped with a speed sensor, the main variable displacement hydraulic pump being configured to supply hydraulic fl
1. A hydrostatic drive system for a vehicle, comprising: an open circuit including: a main variable displacement hydraulic pump configured to be driven by an internal combustion engine equipped with a speed sensor, the main variable displacement hydraulic pump being configured to supply hydraulic fluid to at least one hydraulic consumer via a hydraulic supply line, anda pressure relief valve connected to a reservoir, the pressure relief valve being connected to the hydraulic supply line such that hydraulic fluid in the hydraulic supply line is discharged into the reservoir if a preset maximum operation pressure is reached in the open circuit;a closed circuit configured to propel the vehicle including: an auxiliary variable displacement hydraulic pump configured to be driven by the internal combustion engine and to propel the vehicle, anda hydraulic motor connected to the auxiliary variable displacement hydraulic pump; andan electronic controller connected to the speed sensor and the main variable displacement hydraulic pump, the electronic controller being configured to run a strong braking mode in which the electronic controller at least partially increases the displacement of the main variable displacement hydraulic pump such that hydraulic fluid is discharged via the pressure relief valve into the reservoir if an engine speed is determined, based on a signal received from the speed sensor, which is higher than a predetermined maximum engine speed, wherein the electronic controller is configured to control the displacement of the main variable displacement hydraulic pump by increasing and decreasing the displacement during the strong braking mode such that the engine speed varies within a predetermined engine speed range including the predetermined maximum engine speed, and wherein the electronic controller is additionally configured to control at least one of the displacement of the auxiliary variable displacement hydraulic pump and a displacement of the hydraulic motor by increasing and decreasing the displacements during the strong braking mode such that the engine speed varies within a predetermined engine speed range including the predetermined maximum engine speed. 2. The hydrostatic drive system for a vehicle of claim 1, wherein the hydraulic motor is a variable displacement hydraulic motor. 3. The hydrostatic drive system for a vehicle of claim 1, further comprising a main valve unit configured to control the hydraulic fluid supply from the main variable displacement hydraulic pump to the at least one hydraulic consumer, the main valve unit including the pressure relief valve. 4. The hydrostatic drive system for a vehicle of claim 1, further comprising an unloading valve integrated in a main valve unit and connected to the reservoir, the unloading valve being adapted to discharge the hydraulic fluid output from the main hydraulic pump into the reservoir during the strong braking mode. 5. The hydrostatic drive system for a vehicle of claim 1, wherein the closed circuit further comprises at least one secondary pressure relief valve connected to a hydraulic supply line and a hydraulic return line such that during braking at least a part of hydraulic fluid in the closed circuit is throttled at the at least one secondary pressure relief valve and circulated in the closed circuit. 6. The hydrostatic drive system for a vehicle of claim 1, further comprising: a flush and boost valve unit connected in parallel to the hydraulic motor;a pressure limiting valve connected to the flush and boost valve unit and to a reservoir; anda boost pump provided in the closed circuit, the boost pump being configured to be driven by the internal combustion engine and to replace hydraulic fluid throttled at said pressure limiting valve of the flush and boost valve unit and flushed into the reservoir during braking. 7. The hydrostatic drive system for a vehicle of claim 1, the electronic controller being configured to run a soft braking mode as long as a predetermined engine speed is not reached, the soft braking mode including increasing the displacement of the auxiliary variable displacement hydraulic pump at least partially such that a part of hydraulic fluid circulating in the closed circuit is flushed into the reservoir. 8. A method of braking a vehicle, the vehicle comprising: an open circuit including a main variable displacement hydraulic pump configured to be driven by an internal combustion engine and to supply hydraulic fluid to at least one hydraulic consumer via a hydraulic supply line, and a pressure relief valve connected to a reservoir, the pressure relief valve being connected to a hydraulic supply line and being configured to discharge the hydraulic fluid in the hydraulic supply line into the reservoir if a preset pressure level is reached in the open circuit; anda closed circuit configured to propel the vehicle including an auxiliary variable displacement hydraulic pump configured to be driven by the internal combustion engine and to propel the vehicle, and a hydraulic motor connected to the auxiliary variable displacement hydraulic pump;the method comprising: receiving a signal indicating the engine speed of the internal combustion engine; andif an engine speed is determined, based on the signal received, which is higher than a predetermined maximum engine speed, running a strong braking mode including increasing the displacement of the main variable displacement hydraulic pump such that hydraulic fluid is discharged via the pressure relief valve into the reservoir, wherein the strong braking mode includes the step of varying the displacement of the auxiliary variable displacement hydraulic pump. 9. The method of claim 8, the strong braking mode further including controlling the displacement of the main variable displacement hydraulic pump by increasing and decreasing the displacement during the strong braking mode such that the engine speed is varying within a predetermined engine speed range including the predetermined maximum engine speed. 10. The method of claim 8, wherein the step of varying the displacement of the auxiliary variable displacement hydraulic pump includes increasing the displacement to a maximum displacement. 11. The method of claim 8, further comprising braking by varying the displacement of the auxiliary variable displacement hydraulic pump such that hydraulic fluid circulating in the closed circuit is one or more of partly flushed into the reservoir and partly throttled and circulated in the closed circuit. 12. A method of braking a vehicle including an open hydraulic circuit for supplying at least one hydraulic consumer, and a closed travel circuit, the method comprising the steps of: receiving a signal indicating an engine speed of an internal combustion engine for driving a main variable displacement pump of the open circuit and a variable displacement travel pump of the closed circuit; andif an engine speed is determined, based on the signal received, which is higher than a predetermined maximum engine speed, running a strong braking mode including controlling the displacement of the main variable displacement hydraulic pump by increasing and decreasing the displacement such that the engine speed varies within a predetermined engine speed range including a predetermined maximum engine speed resulting in that hydraulic fluid is discharged into a reservoir via a pressure relief valve connected to a hydraulic supply line of the open circuit, the pressure relief valve being configured to avoid a pressure in the open circuit above a maximum operation pressure, and wherein the strong braking mode includes varying the displacement of the variable displacement travel pump. 13. The method of claim 12, further including controlling the displacement of the variable displacement travel pump of the closed circuit for propelling the vehicle as desired. 14. The method of claim 12, wherein varying the displacement of the variable displacement travel pump includes increasing the displacement to a maximum displacement. 15. The method of claim 12, further including braking by varying the displacement of the variable displacement travel pump such that hydraulic fluid circulating in the closed circuit is one or more of partly flushed into the reservoir and partly throttled and circulated in the closed circuit. 16. The method of claim 15, further including driving a boost pump in the closed circuit by the internal combustion engine to replace fluid partly flushed out of the closed circuit into the reservoir.
연구과제 타임라인
LOADING...
LOADING...
LOADING...
LOADING...
LOADING...
이 특허에 인용된 특허 (9)
Oberhausser, Martin; Weickert, Thomas, Control arrangement for at least two hydraulic consumers and pressure differential valve for said control arrangement.
※ AI-Helper는 부적절한 답변을 할 수 있습니다.