Abstract : The application of gear flow meter in the conventional hydraulic system is analyzed. The application of the gear flow meter in the hydraulic system of the machine tool is introduced. The shortcomings in the design of the hydraulic system of the machine tool are solved.
Keywords: gear flow meter machine hydraulic system position monitoring machine tool hydraulic system as an auxiliary power source, is an integral part of the machine tool, such as spindle loose knives, gravity balance, clamping and release of the functional components, tool magazine drive, etc. Open hydraulic drive. In order to ensure the reliable operation of the machine tool, each time an action command is executed, a reliable completion signal must be detected after the action is completed to perform the next action so as to prevent the malfunction signal from causing the machine tool to malfunction and cause a safety accident. Therefore, it is very important for the hydraulic system of the machine tool to detect the arrival signal of the component.
Flowmeter as a detection element is widely used in coal and petrochemical industries. As a flow detection control element, high-precision flowmeter has a certain application in the aerospace hydraulic servo control system, but it is less applied in the conventional machine tool hydraulic system. The number of pulses issued by the flowmeter can truly reflect the principle of the stroke of the cylinder. The gear flowmeter is applied to the hydraulic system of the machine tool, which solves the shortcomings of the previous system design and has achieved good results.
1 Introduction to Gear Flowmeters There are many kinds of flowmeters, their functional principles are different, and their application fields are also different. The gear flow meter is based on the principle of a gear motor. The two spur gears are driven by the liquid flow in the measuring chamber without contact; the motion of the gears is detected by two non-contact sensors located in the cover plate, between the sensor chamber and the metering ring chamber. , With a non-magnetic anti-pressure diaphragm; When the measuring mechanism rotates a tooth, the sensor sends out a pulse signal, corresponding to a tooth's oil ΔV through the flow meter, through the preamplifier, the signal is converted into a square wave signal; two channels Detection can have higher resolution and confirm traffic direction.
The gear flow meter has high precision, good viscosity and temperature characteristics, high working pressure and relatively low price, and is suitable for application in the hydraulic system of the machine tool. Its structure is shown in Figure 1.
In the research and development of a national high-speed Gantry five-axis machining center, a certain company was involved in the double swing head exchange by four self-locking studs to achieve a double swing head loose card. In order to solve the above problem, a flow meter is provided in the hydraulic loose card loop as a snap-release in-position detection element. The flow meter can truly detect whether the cylinder clamping and releasing is in place by detecting the amount of oil passing through. Because the flow meter is installed on the loop, it is not limited by the size of the mechanical structure, and successfully solves the problem of the double pendulum head loose card in place detection. The schematic diagram is shown in Figure 3.
Set the required oil volume for each pull screw to clamp V0 = 10mL, and the total oil required for the clamp action is 4V0 = 40mL. The author selected the German KRACHT company VC0.2 model gear flowmeter, and the gear geometric volume ΔV=0.245mL, ie Every time a pulse signal gear flowmeter passes 0.245mL oil, the number of pulses needed to complete the clamping action is:
When the pull-pin is released, the flow meter measures the amount of oil in the same oil chamber. The number of pulses is the same as the clamping action, but in the opposite direction. Therefore, after the pull-pin loose card operation is performed, whether the number of pulses received by the flow meter reaches the corresponding value (the corresponding relationship between the number of detected pulses and the pull pin state is shown in Table 1) is used to judge whether the operation is completed correctly or not. The dual-channel pulse signal can be The direction of rotation of the flow meter is detected so as to determine whether it is released or locked. 
2.2 Position detection Applying the machine with pallet exchange function, the pallet changer is driven by hydraulic pressure. In order to avoid the impact between the pallet exchanger, the pallet and the turntable, it needs to switch to low speed before contacting with each other, and then run at high speed after contact. The usual method is to set the limit switch or proximity switch during the stroke of the cylinder and issue the speed switching signal. The schematic diagram is shown in Figure 4. Disadvantages of this solution are: (1) Setting a limit switch or proximity switch requires a certain amount of space; (2) Inconvenient adjustment of a set point, and the number of set points is limited by space; (3) Vulnerable to environmental interference and error signal.
In order to solve the above problems, the company adopted the method of configuring the gear flow meter on the hydraulic circuit of the high-speed vertical machining center tray exchanger to increase the cylinder displacement measurement and set the corresponding speed switching point in the middle of the stroke of the cylinder to realize the pallet exchanger. Speed ​​control, schematic diagram shown in Figure 5.
Setpoint pulse number calculation formula: 
In the formula: nset is to set the number of transmission point pulses;
Lset is to set the sending point location;
L0 is the total stroke of the cylinder;
D is the cylinder diameter;
ΔV is the flowmeter geometric volume.
3 Conclusion Based on the number of issued pulses can truly reflect the principle of the cylinder stroke, gear flow meter can be applied to the hydraulic system for position monitoring and detection. The gear flowmeter has the advantages of not occupying the mechanical design space, flexible position detection setpoint, and being less susceptible to environmental interference. It has a broad application prospect in the hydraulic system of the machine tool.
Keywords: gear flow meter machine hydraulic system position monitoring machine tool hydraulic system as an auxiliary power source, is an integral part of the machine tool, such as spindle loose knives, gravity balance, clamping and release of the functional components, tool magazine drive, etc. Open hydraulic drive. In order to ensure the reliable operation of the machine tool, each time an action command is executed, a reliable completion signal must be detected after the action is completed to perform the next action so as to prevent the malfunction signal from causing the machine tool to malfunction and cause a safety accident. Therefore, it is very important for the hydraulic system of the machine tool to detect the arrival signal of the component.
Flowmeter as a detection element is widely used in coal and petrochemical industries. As a flow detection control element, high-precision flowmeter has a certain application in the aerospace hydraulic servo control system, but it is less applied in the conventional machine tool hydraulic system. The number of pulses issued by the flowmeter can truly reflect the principle of the stroke of the cylinder. The gear flowmeter is applied to the hydraulic system of the machine tool, which solves the shortcomings of the previous system design and has achieved good results.
1 Introduction to Gear Flowmeters There are many kinds of flowmeters, their functional principles are different, and their application fields are also different. The gear flow meter is based on the principle of a gear motor. The two spur gears are driven by the liquid flow in the measuring chamber without contact; the motion of the gears is detected by two non-contact sensors located in the cover plate, between the sensor chamber and the metering ring chamber. , With a non-magnetic anti-pressure diaphragm; When the measuring mechanism rotates a tooth, the sensor sends out a pulse signal, corresponding to a tooth's oil ΔV through the flow meter, through the preamplifier, the signal is converted into a square wave signal; two channels Detection can have higher resolution and confirm traffic direction.
The gear flow meter has high precision, good viscosity and temperature characteristics, high working pressure and relatively low price, and is suitable for application in the hydraulic system of the machine tool. Its structure is shown in Figure 1.
Figure 1 Gear Flowmeter Structure
2 Application of Gear Flowmeter in Hydraulic System of Machine Tool 2.1 Clamp Release In Place Detection Application There are many auxiliary actions for hydraulic chuck to loosen on the machine, such as spindle loose card knife, servo shaft holding brake loose card, and tray exchange tray Songka, exchange the double swing head when the double swing head loose card and so on. The hydraulic cylinder that performs the chucking and releasing action is more implanted inside the functional components. Due to the compact mechanical structure, it is difficult to directly install the proximity switch or the displacement sensor inside to obtain the position signal. Some of the functional components transmit the displacement of the piston to the outside of the functional component when the structure permits, such as spindle loose knives and turntable loose cards. However, the rotary shaft annular brake, pallet clamping pull nails, double swing head exchange pull nails, etc., must be used when the clamping mechanism is inserted inside the mechanical body, due to the structure of the limit can not be directly measured displacement signal. The usual method is to use the pressure signal instead of the displacement signal, that is, the loose card pressure reaches the set value and marks the stop of the piston movement, which indirectly determines that the loose card movement has been completed. The schematic diagram is shown in FIG. 2 . However, if for some reason the cylinder is stuck in the middle position, an error signal will be issued, causing the machine to malfunction and causing a safety accident. Figure 2 Pressure switch detection loose card in place signal schematic
In the research and development of a national high-speed Gantry five-axis machining center, a certain company was involved in the double swing head exchange by four self-locking studs to achieve a double swing head loose card. In order to solve the above problem, a flow meter is provided in the hydraulic loose card loop as a snap-release in-position detection element. The flow meter can truly detect whether the cylinder clamping and releasing is in place by detecting the amount of oil passing through. Because the flow meter is installed on the loop, it is not limited by the size of the mechanical structure, and successfully solves the problem of the double pendulum head loose card in place detection. The schematic diagram is shown in Figure 3.
Figure 3 flow meter detection loose card in place signal schematic
Set the required oil volume for each pull screw to clamp V0 = 10mL, and the total oil required for the clamp action is 4V0 = 40mL. The author selected the German KRACHT company VC0.2 model gear flowmeter, and the gear geometric volume ΔV=0.245mL, ie Every time a pulse signal gear flowmeter passes 0.245mL oil, the number of pulses needed to complete the clamping action is:
Table 1 Correspondence between the number of detected pulses and the status of pull pins
In order to solve the above problems, the company adopted the method of configuring the gear flow meter on the hydraulic circuit of the high-speed vertical machining center tray exchanger to increase the cylinder displacement measurement and set the corresponding speed switching point in the middle of the stroke of the cylinder to realize the pallet exchanger. Speed ​​control, schematic diagram shown in Figure 5.
Lset is to set the sending point location;
L0 is the total stroke of the cylinder;
D is the cylinder diameter;
ΔV is the flowmeter geometric volume.
3 Conclusion Based on the number of issued pulses can truly reflect the principle of the cylinder stroke, gear flow meter can be applied to the hydraulic system for position monitoring and detection. The gear flowmeter has the advantages of not occupying the mechanical design space, flexible position detection setpoint, and being less susceptible to environmental interference. It has a broad application prospect in the hydraulic system of the machine tool.
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