(1. Li Jin Shaoguan College, Shaoguan 512005, China 2. Song Dechao Tongji University, Shanghai 200092, China 3. Liu Jinlong Zhenjiang Hydraulic Parts Factory Zhenjiang, Jiangsu 212005, China)
Abstract: Due to the flow amplification capability of TLF coaxial flow amplifier, it has the advantages of small size, light weight, good fine-tuning characteristics, small pressure loss, convenient installation and low price. Widely used in articulated industrial vehicles such as loaders, graders, mining vehicles, forklifts, tractors, wood handlers, and various small vehicles. Therefore, understanding the working principle and common faults of the TLF coaxial flow amplifier helps to improve our production efficiency.
Keywords: flow amplification; works; Troubleshooting <br> CLC: literature identification code: A Article ID: 7445
Operation principle for model TLF coaxial flow amplifying steering and its trouble removal
Li Jin, Song De-chao, Liu Jin-long
(1. Shaoguan university, Shaoguan 512005, Guangdong, China; 2. Tongji university, Shanghai 200092, China; 3. Zhenjiang Hydraulic Components Manufacturing Co Ltd, Zhenjiang 212005, Jiangsu, China)
Abstract: Because model TLF-coaxial flow amplifier was flow amplification ability, it also provides the following characteristics: compact volume and light weight, good adjusting characteristics and small pressure loss, convenient installation layout and reasonable prices. It was used in the area of ​​industry Applications of articulated vehicles (such as loaders, graders, mining vehicles, forklifts, tractors, haulers as well as small-size vehicles). Thus, to work principle and common trouble of model TLF coaxial flow amplifying steering understanding, that is helpful to Enhance our production working efficiency.
Keywords: Flow amplification, Operation principle, Trouble removal
TLF series load sensing flow amplification full hydraulic steering gear (referred to as coaxial flow amplifier). It is a hydrostatic steering element with flow amplification capability. At low speed steering (10 rpm), the effective displacement of the steering element is equal to the metered displacement; as the input speed increases (10-40 rpm), the effective displacement increases as the input speed increases; when the input speed is greater than 40 rpm, The effective displacement of the steering element is substantially constant at its nominal equivalent displacement. Compared with the existing full hydraulic steering gear, the coaxial flow amplification steering gear has the advantages of small size, light weight, good fine adjustment characteristics, small pressure loss, convenient installation and installation, and low price. Therefore, it is widely used in articulated industrial vehicles such as loaders, graders, mining vehicles, forklifts, tractors, wood handlers, and various small vehicles.
1. The main composition and function of TLF coaxial flow amplifier [1]
Like the traditional BZZ series of full hydraulic steering gears, the coaxial flow amplifier consists of a control steering valve and a cycloidal metering device. The valve sleeve has various grooves and holes, and various orifices are formed between the slots. Figure 2 is a diagram showing the internal oil passage of the steering gear when the steering wheel is rotated in a certain direction. The valve core is deflected relative to the valve sleeve, and the variable orifices are opened except for C9 and C10, so that the pressure oil enters the steering hydraulic cylinder through the cycloidal metering device, and the rotor pushed by the oil drives the valve sleeve to move along the rotation direction of the valve core, and closes. The throttle port is made such that the volume of oil supplied to the steering cylinder is proportional to the steering wheel angle. In the coaxial flow amplifier, a load sensing variable orifice C1 is arranged on the control rotary valve, and an external priority valve controls the pressure difference between the two ends to keep it constant, so that the opening area of ​​the orifice is proportional to the flow rate .
The coaxial flow amplifier further adds a flow amplification throttle port C8 on the control rotary valve, and the upstream of the throttle port upstream of the throttle port C1 changes synchronously with the opening degree of the throttle port C1 to form one and include The water amount in which the control oil passages are connected in parallel with the metering device amplifies the oil passage. Therefore, the amount of oil supplied to the cylinder is equal to the sum of the flow rate through the control oil passage and the flow rate of the amplification oil passage.
A check valve is connected in series in the amplification circuit. When the steering cylinder reaches the end of the planet, the valve prevents oil from flowing back along the amplifying oil path, avoiding the formation of an internal oil circulation in the steering gear, causing the system pressure to rise until the steering cylinder has reached the end.
Fig1. With the flow of the hydraulic steering system amplifier Fig2. Steering internal Circuit chart
1. Steering hydraulic cylinder 2. Combination valve block 3. Coaxial flow amplifier 4. Supply working oil circuit 5. Priority valve 2. The working principle of the TLF coaxial flow amplifier does not rotate relative to the valve sleeve of the coaxial flow amplifier when the steering wheel is not turned. Except for the throttle ports C9 and C10, the other throttle ports are closed. Due to the large oil resistance of C9, the LS port maintains a low pressure under the partial pressure of C9 and C10. At this time, as long as the PP port has a lower pressure, the priority valve spool can be pushed to the right side, and the valve port leading to the steering oil passage is closed, so that most of the oil is supplied to the working oil passage through the EF port.
When turning the steering wheel in a certain direction, close C9, C10 and open other variable orifices. Changing the opening of the throttle port C1 is proportional to the steering wheel speed. When the steering wheel is at a certain speed, C1 corresponds to an opening degree. If some disturbance occurs, the flow rate through the steering oil passage increases, causing the pressure difference across C1 to increase, passing through the PP port and the LS port to both ends of the priority valve spool, pushing the force spool to the right, turning off the small steering The oil circuit and the valve port reduce the flow of the steering oil until the pressure difference between the two ends of C1 returns to the previous value. On the contrary, when the external disturbance causes the flow to decrease, the pressure difference between C1 decreases, and the priority valve spool moves to the left. Open the valve port of the steering oil passage to increase the flow rate of the steering oil passage, and the priority valve keeps the pressure difference between the two ends of C1 substantially unchanged. The flow through C1 is proportional to the steering wheel speed. Since the series variable orifice C8 and the check valve amplifying oil passage are connected in parallel with the control oil passages of the series C1, C4, C5 and the cycloidal metering device, and the opening degree of the C8 changes synchronously with the opening degree of the C1, the supply steering is performed. The oil flow rate of the cylinder should be:
Q = nq(1+N•SQRT(1+(Δp1+Δp2+Δp3)/Δp4))
Where n----steering wheel speed (r/min), q----metering device displacement (L/r), N----the number of holes on the valve sleeve that constitute C8 divided by the number of holes forming C1 Ratio, Δp1----the sum of the upper pressure drops (Mpa), Δp2-----pressure drop (Mpa) on the metering device, Δp3 -----pressure drop on the check valve (Mpa), Δp4- ---- Pressure drop (Mpa), if Δp1 + Δp2 = Δp3 then Q = nq (1 + N) At this time, the flow rate supplied to the steering hydraulic cylinder is equal to N+1 times the flow rate through the metering device [1].
The system shown in Figure 1 is a coaxial flow amplifier that cooperates with a priority valve. It can preferentially distribute the flow according to the steering oil path requirements, and the remaining flow of the hydraulic pump can be supplied to the working oil circuit. If the steering oil circuit and the working oil circuit do not meet the maximum flow requirement at the same time, the hydraulic pump oil supply amount may be slightly larger than the two oil passages.
3. TLF type coaxial flow amplifier common faults and troubleshooting (1) oil leakage at the joint surface, journal or back cover gasket.
The cause of the failure (one-to-one correspondence and elimination method): 1 the joint surface has dirt or fastening bolts loose; 2 the joint surface or the journal rubber ring is damaged; 3 the back cover bolt washer is not flat or damaged. Remedy: 1 Remove dirt, tighten bolts; 2 Replace new rubber ring; 3 Smooth or replace gasket.
(2) Normally turning the steering wheel slowly, and turning the steering wheel quickly.
The cause of the failure (one-to-one correspondence and elimination method): 1 oil supply shortage; 2 pipeline pressure loss between the priority valve and the steering gear is too large; 3 priority valve spool is stuck; 4 priority valve and steering control There is air in the oil road. Remedy: 1 repair or replace the oil pump; 2 select the priority control spring with large control pressure, or redesign the pipeline to use the external control type priority valve; 3 eliminate the stuck fault or replace the priority valve; 4 turn the steering wheel to make the steering wheel Continue to the steering wheel after the limit position, forcing the steering safety valve to open and remove air.
(3) There is foam in the oil, and an irregular sound is emitted. When the steering wheel is turned, the cylinder does not move when moving.
Cause of the malfunction: There is air in the steering system. Remedy: 1 Check the oil level to make up the oil in the tank; 2 Check the oil suction line for air leakage and remove it; 3 Eliminate the air in the system.
(4) Both the fast forward and the slow steering wheel are heavy.
The cause of the failure: the steel ball check valve in the valve body fails. Remedy: Replace the steel ball or remove dirt.
(5) Light when no load, sink when there is load.
Fault reason: 1 steering safety valve or system relief valve set pressure value, lower than the pressure required for work; 2 steering safety valve or system overflow valve stuck; 3 oil viscosity is too large. Remedy: 1Re-adjust the steering safety valve and system relief valve; 2Remove dirt; 3 Replace with qualified oil.
(6) When the steering wheel is turned to the limit position, the steering wheel is still very light.
Cause of failure: The bidirectional buffer setting pressure value is lower than the steering relief valve setting pressure value. Remedy: Re-adjust the two-way buffer valve so that its opening pressure is higher than the steering relief valve setting pressure value of 4 to 6 MPa.
(7) The steering wheel cannot be automatically returned to the center, and the pressure drop in the middle position increases.
The cause of the malfunction: the spring piece is broken. Remedy: Replace the damaged spring piece.
(8) The pressure runout increases significantly and cannot even rotate.
Cause of the fault: The dial, the linkage shaft opening is broken or deformed to replace the dial or the linkage shaft. Remedy: Replace the dial or the linkage shaft (do not replace it with other things).
(9) The steering wheel rotates or swings left and right.
The cause of the fault: the rotor and the linkage shaft are misplaced. Remedy: Reassemble (the rotor bottom groove is aligned with the end of the linkage shaft end point mark).
4. Summary In view of the wide application of TLF coaxial flow amplifiers in various engineering vehicles such as loaders, graders, mining vehicles, forklifts, tractors, wood handlers and various small vehicles, this paper describes the working principle of TLF coaxial flow amplifiers. The analysis of its common faults helps us to solve similar faults in the actual project, so as to improve work efficiency and ensure the timely completion of work tasks.
references:
[1] Huang Zhende, Li Furong, Wu Jifei. Coaxial flow amplifier and its application[J]. Construction Machinery, 1999, (12): 29-30.
About the author: Li Jin (1979--), male, Xiangyang, Hunan, lecturer at Shaoguan College, Guangdong Province, graduated from Tongji University, majoring in automotive and engineering vehicles.
Contact number or 13602249623 Address: 204, Building 1, Hanjiashan Campus, Shaoguan College, Guangdong Province, China Post Code: 512005
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