福州大学：《液压与气压传动》课程电子教案（PPT教学课件）Chapter 07 Basic Hydraulic Circuits

Chapter 7 Basic Hydraulic Circuits Chapter list 7.1 Pressure Control Circuits 7.2 Speed Control Circuits 7.3 Directional Control Circuits 7.4 Multi-actuator Control Circuits Homepage List Upwards Downwards Retumn Exit

Chapter 7 Basic Hydraulic Circuits 1 7.1 Pressure Control Circuits 7.2 Speed Control Circuits 7.3 Directional Control Circuits 7.4 Multi-actuator Control Circuits Chapter list

Chapter 7 Basic Hydraulie Circuits Introduction Any hydraulic system is constituted by several basic hydraulic circuits.A hydraulic basic circuit is a group of components. Let's classify:the functions in hydraulic system by: pressure control circuits:control entire or partial operating pressure; speed control circuits:control and regulate motion speed of actuator elements; Directional control circuits:control and shift motion direction of actuator; Multi-actuator control circuits:control and shift operating cycle between several actuators. Homepage List Upwards Downwards Retumn Exit

Chapter 7 Basic Hydraulic Circuits 2 Introduction Any hydraulic system is constituted by several basic hydraulic circuits. A hydraulic basic circuit is a group of components. Let’s classify: the functions in hydraulic system by: pressure control circuits: control entire or partial operating pressure; speed control circuits: control and regulate motion speed of actuator elements; Directional control circuits: control and shift motion direction of actuator; Multi-actuator control circuits: control and shift operating cycle between several actuators

Chapter 7 Basic Hydraulie Cireuits 7.1 Pressure Control Circuits Used to control and regulate the entire and partial pressure to realize a satisfied force and torque requirements,enhance working efficiency and improve the properties in a hydraulic system(six types shown in below) 7.1.1 Pressure regulated circuits 7.1.2 Pressure-venting circuits 7.1.3 Pressure-reducing circuits 7.1.4 Pressure-increasing circuits 7.1.5 Pressure counterbalance circuits 7.1.6 Pressure-holding circuits Hmepage List Upward达s Downwards Retumn Exit

Chapter 7 Basic Hydraulic Circuits 3 7.1 Pressure Control Circuits 7.1.1 Pressure regulated circuits 7.1.2 Pressure-venting circuits 7.1.3 Pressure-reducing circuits 7.1.4 Pressure-increasing circuits 7.1.5 Pressure counterbalance circuits 7.1.6 Pressure-holding circuits Used to control and regulate the entire and partial pressure to realize a satisfied force and torque requirements, enhance working efficiency and improve the properties in a hydraulic system (six types shown in below)

Chapter 7 Basie Hydraulie Cireuits 7.1.1 Pressure regulated circuits 1.Pressure regulated from remote port 月 To system system X仪 Curren System pressure 九 c) Play Play Play Dy吧 DVD D吧 Fig.7-1 a)Pressure regulated from remote port b)Multistage pressure regulated circuit c)Step less pressure regulated circuit 1-Relief-valve pilot 2,3-Pressure regulated valves 4-Directional valve Homepage List Upwards Downwards Retumn Exit

Chapter 7 Basic Hydraulic Circuits 4 7.1.1 Pressure regulated circuits 1. Pressure regulated from remote port Fig.7-1 a)Pressure regulated from remote port b)Multistage pressure regulated circuit c) Step less pressure regulated circuit 1-Relief-valve pilot 2,3-Pressure regulated valves 4-Directional valve

Chapter 7 Basie Hydraulie Cireuits 2.Multistage pressure regulated circuits As shown in Fig.7-1b. 3.Step less pressure regulated circuits As shown in Fig.7-1c. 5 Homepage List Upwards Downwards Retumn Exit

Chapter 7 Basic Hydraulic Circuits 5 2. Multistage pressure regulated circuits As shown in Fig.7-1b. As shown in Fig.7-1c. 3. Step less pressure regulated circuits

Chapter 7 Basic Hydraulic Circuits 7.1.2 Pressure-venting circuits The function The function of a pressure venting circuit is to unload the pumping and to keep the pump idling when the hydraulic system is during the regular off- working,which it will realize to save the energy,reduce the heating and get a long life of use. The methods There are two methods of unloaded pump:one is venting by pressure (pump operating under zero or near zero pressure,is called the pressure- venting)and the other is venting by flow rate(pump operating under zero or neat zero flow rates,is called flow-venting). Homepage List Upwards Downwards Retun Exit

Chapter 7 Basic Hydraulic Circuits 6 7.1.2 Pressure-venting circuits The function The methods The function of a pressure venting circuit is to unload the pumping and to keep the pump idling when the hydraulic system is during the regular off￾working, which it will realize to save the energy, reduce the heating and get a long life of use. There are two methods of unloaded pump: one is venting by pressure (pump operating under zero or near zero pressure, is called the pressure￾venting) and the other is venting by flow rate (pump operating under zero or neat zero flow rates, is called flow-venting)

Chapter 7 Basic Hydraulie Cireuits 1.Pressure-venting by the neutral of a directional valve To system Play DVD TX✉ Fig.7-2a Pressure-venting by the neutral of a directional valve Play DVD Fig.7-2b Pressure-venting by a solenoid operated reliefvalve 3 Play DVD W☒& Fig.7-2c Pressure-venting by a pump limited pressure Play y吧 Fig.7-2d Pressure-venting by an accumulator Homepage List Upward达s Downwards Retumn Exit

Chapter 7 Basic Hydraulic Circuits 7 1. Pressure-venting by the neutral of a directional valve Fig.7-2a Pressure-venting by the neutral of a directional valve Fig.7-2b Pressure-venting by a solenoid operated relief valve Fig.7-2c Pressure-venting by a pump limited pressure Fig.7-2d Pressure-venting by an accumulator

Chapter 7 Basic Hydraulic Circuits 2.Pressure-venting by pilot-operated relief valve As shown in Fig.7-2b. 3.Pressure-venting by a pump limited pressure As shown in Fig.7-2c. 4.Pressure-venting by an accumulator As shown in Fig.7-2d. 8 Homepage List Upwards Downwards Retumn Exit

Chapter 7 Basic Hydraulic Circuits 8 2. Pressure-venting by pilot -operated relief valve As shown in Fig.7-2b. 3. Pressure-venting by a pump limited pressure As shown in Fig.7-2c. 4. Pressure-venting by an accumulator As shown in Fig.7-2d

Chapter 7 Basic Hydraulic Cireuits 7.1.3 Pressure-reducing circuits The function:Used to drop a stable branch circuit pressure below the normal operating pressure of system. Usually a fixed pressure-reducing valve is installed to a branch circuit such as Fig.7-3a.Fig.7-3b is a two-stage pressure-reducing circuit To ensure a stable working speed,the lowest pressure should not be less than 0.5MPa,and the highest setting pressure should be at least less than 0.5MPa of the system pressure.When the actuator elements speed in a reducing-circuit needs to be regulated,the speed-regulating valve should be installed in the latter of the reducing-valve in order to avoid the affection of speed during the working. Homepage List Upwards Downwards Retumn Exit

Chapter 7 Basic Hydraulic Circuits 9 7.1.3 Pressure-reducing circuits The function: Used to drop a stable branch circuit pressure below the normal operating pressure of system. Usually a fixed pressure-reducing valve is installed to a branch circuit such as Fig. 7-3a. Fig. 7-3b is a two-stage pressure-reducing circuit. To ensure a stable working speed, the lowest pressure should not be less than 0.5MPa, and the highest setting pressure should be at least less than 0.5MPa of the system pressure. When the actuator elements speed in a reducing-circuit needs to be regulated, the speed-regulating valve should be installed in the latter of the reducing-valve in order to avoid the affection of speed during the working

Chapter 7 Basic Hydraulic Circuits To system To system a Play Play DVD DVD Fig.7-3 a)One-stage pressure-reducing b)Two-stage pressure-reducing 1,6-Pilot-operated pressure-reducing valve 2-Rated pressure-reducing valve 3-Check valve 4-Hydraulic cylinder 5-Two positions with two-ports directional valve 10 Homepage List Upwards Downwards Retumn Exit

Chapter 7 Basic Hydraulic Circuits 10 1,6- Pilot-operated pressure-reducing valve 2- Rated pressure-reducing valve 3- Check valve 4- Hydraulic cylinder 5-Two positions with two-ports directional valve Fig.7-3 a)One-stage pressure-reducing b) Two-stage pressure-reducing