Tempo estimado de leitura: 21 minuto

Questão 1: A Especificação da Válvula de Controle Direcional do Sistema Hidráulico do Expansor de Tubo

Figure 1-1 shows the hydraulic system of a 600-ton pipe expander used in a factory. It can realize the action cycle of vertical cylinder fast down, sealing control cylinders on both sides synchronously fast forward, mold sealing one vertical, side cylinder pressurization-two cylinders synchronously rewind the mold opening and the vertical cylinder quickly retreats the mold opening action cycle. Directional Control Valve

When the solenoid 2DT is energized, the electromagnetic directional valve 10 is switched to the left position, and the hydraulic pump 1—the left position of the electro-hydraulic directional valve 8—the left position of the valve 10—the double hydraulic control check valve 13—the rodless cavity of the vertical cylinder 19, The vertical cylinder 19 quickly descends and seals the mold. Directional Control Valve

Quando a pressão de vedação do molde atinge o valor especificado, o manômetro de contato elétrico 14 envia um sinal, o solenóide 2DT é cortado, 1DT, 5DT, 6DT são energizados e o óleo hidráulico passa através da válvula 8 para a direita e o válvula de desvio 9 - a válvula de reversão eletromagnética 11 para a direita - A posição esquerda da válvula de reversão eletromagnética 12-a verificação de controle hidráulico duplo válvulas 16 and 18 enter the rodless chambers of the side cylinders 20 and 21 respectively, and the cylinders on both sides fast forward and seal the mold synchronously. Directional Control Valve

Quando a pressão de vedação do molde atinge o valor especificado, o medidor de pressão de contato elétrico 17 envia um sinal, a pressão hidráulica de ultra-alta pressão 15 e 2 ~ / move para trás ao mesmo tempo e, respectivamente, injeta óleo de alta pressão no sem haste cavidade do cilindro vertical 19 e dos cilindros laterais 20 e 21 para atingir a força de pressão de Saída 6MN (600tf).

When the electromagnets 1DT, 4DT, 7DT are energized, the cylinders on both sides will retreat and open the mold synchronously. When the end of the stroke is reached, the stroke will open and a signal will be sent. The electromagnet 1DT is de-energized and the 3DT is energized, and the vertical cylinder quickly moves upward to open the mold. Directional Control Valve

In order to improve work efficiency and reduce power consumption, the system adopts pressure compensation variable axial piston pump 1 to achieve low-pressure and high-speed operation of vertical cylinders and side cylinders, and high-pressure and low-speed operation during mold sealing. The specifications of the three hydraulic cylinders are the same. Directional Control Valve

The vertical cylinder and the side cylinder move slowly. The vertical cylinder moves down quickly for 70 seconds, and the side cylinder moves forward quickly for 60 seconds. The return time is longer, resulting in extremely low production efficiency. Directional Control Valve

It can be seen from the working principle of the system that the vertical cylinder’s rapid downward movement and the side cylinder’s rapid forward movement are performed independently. A hydraulic source provides flow, and its operating speed is determined by the output flow of the hydraulic pump 1. When the vertical cylinder and the side cylinder are running quickly, because there is no load, the working pressure of the system is very low at this time and the pressure compensation variable bomba hidráulica outputs at full flow. Directional Control Valve

O cilindro hidráulico se move lentamente e o tempo de funcionamento é muito longo, indicando que a entrada de fluxo real para o cilindro hidráulico é muito pequeno. Isso pode ter as seguintes duas situações:

• The volumetric efficiency of hydraulic pump 1 is too low, causing the actual maximum flow output of the pump to be too small. Directional Control Valve
• The system pressure loss is too large so that the pump is in a constant power variable adjustment condition and cannot output at full flow. Directional Control Valve

É verificado por inspeção que a perda de volume da bomba hidráulica 1 não é grande e a eficiência volumétrica não diminuiu. Conclui-se que o último pode causar problemas no sistema.

From the above analysis, it can be seen that when the hydraulic cylinder is running fast, the total partial pressure loss caused by the oil passing through the hydraulic valves is very large, especially the pressure loss through the electromagnetic reversing valve and the two-way hydraulic lock is the largest, which greatly exceeds their rated pressure Loss value. The total partial pressure loss of the hydraulic valve is combined with the pressure loss along the pipeline and the partial pressure loss, which will inevitably increase the working pressure of the system and reduce the actual output flow of the pump, thereby reducing the operating speed of the hydraulic cylinder. Slow, the running time becomes longer. Directional Control Valve

Conclusão: A principal causa dos problemas do sistema é a seleção inadequada das especificações da válvula de reversão eletromagnética e da trava hidráulica bidirecional.

The best way to solve this problem: select the electromagnetic directional valve and two-way hydraulic lock with appropriate specifications, and replace the corresponding components in the system, thereby reducing the partial pressure loss of the hydraulic valve. Directional Control Valve

When selecting a hydraulic valve to form a hydraulic system, in addition to considering the proper function of the selected hydraulic valve, it is also necessary to consider that its specifications should meet the performance requirements of the system. The improper selection of component specifications in this example will cause slow movement of the main and side cylinders and affect the normal working performance of the system, but will also cause excessive resistance loss, resulting in large energy loss and increased oil temperature. Directional Control Valve

Pergunta 2: Seleção do tipo de válvula direcional no sistema hidráulico da máquina de prensagem

Figure 1-4 shows the hydraulic system of a stretch-bending machine designed and manufactured by a certain factory, which can realize the stretching and bending of the profile. Operate the manual reversing valve 2. The oil enters the rodless cavity of the stretching hydraulic cylinders 4 and 5 through the left position, and the pistons of the stretching hydraulic cylinders 4 and 5 move forward to carry out the stretching process of the profile.

When the required stretch rate is reached, the manual reversing valve 3 is then operated to connect to the circuit in its left position, and the oil enters the rodless cavity of the bending hydraulic cylinder 6 to bend the profile. After bending and shaping, the workpiece is unloaded, and the bending hydraulic cylinder 6 and the stretching hydraulic cylinders 4 and 5 are retracted, thereby completing a profile stretching and bending action cycle. The system pressure is set by overflow valve 1. After improvement, the hydraulic system adopts an electromagnetic directional valve and electromagnetic overflow valve, as shown in Figure 1-4(b). Directional Control Valve

Existing problems: The system adopts an electromagnetic overflow valve, which has obvious effects on reducing power consumption and reducing oil heating and leakage. However, when the stretching and bending actions begin, there is obvious hydraulic shock, accompanied by equipment flutter, which affects the quality of the product. Directional Control Valve

The electromagnetic reversing valve selected has the same specifications as the original manual reversing valve. The only difference is the reversing operation method. What is the problem? Directional Control Valve

The electromagnetic reversing valve changes the working position of the valve by using the suction force of the electromagnet to push the spool relative to the valve body. It switches quickly and the reversing time is short. Therefore, hydraulic shock will inevitably occur when the reversing valve is switched. The manual reversing valve is used to manipulate the lever and push the spool to move relative to the valve body to change the position. It does not switch as quickly as the former.

It gradually opens or closes the valve port. It has the effect of throttling and damping, so it has an impact on the hydraulic pressure. Has a buffering effect. Therefore, the commutation stability of the modified system is poor. Directional Control Valve

Usar a mesma especificação da válvula de reversão eletro-hidráulica em vez da válvula de reversão eletromagnética pode eliminar o choque hidráulico. Ao mesmo tempo, também tem as vantagens de operação flexível da válvula de reversão eletromagnética e fácil controle automático do programa. O sistema hidráulico após a transformação adicional é mostrado na Figura 1- Conforme mostrado em 2 (c). O ajuste da válvula de reversão eletro-hidráulica controla o amortecedor no circuito de óleo sob pressão para ajustar o tempo de reversão, melhorando assim a estabilidade da reversão.

This example illustrates: For hydraulic equipment that requires high commutation stability, it is advisable to use an electro-hydraulic directional valve or a controllable commutation time. Directional Control Valve

The manual reversing valve constitutes the hydraulic system. Directional Control Valve

Pergunta 3: O problema da válvula hidráulica do sistema hidráulico da plataforma de elevação

Figure 1-6 shows the hydraulic system of a lifting platform made by a factory, which can realize equipment lifting, lowering, and stopping at any position. Directional Control Valve

When 2DT is energized, oil-electromagnetic reversing valve 5 right position-hydraulically controlled check valve 7-plunger cylinder 8 lower cavity-plunger moves upwards-the weight is lifted. When the 1DT is energized, the oil-hydraulic control check valve 7-electromagnetic reversing valve 5 left position-throttle valve 4-oil tank, the plunger moves downwards-the weight drops. The descending speed of the weight is controlled by the throttle valve 4, and the descending stop position is controlled by the hydraulically controlled check valve 7. When the 3DT is energized, oil-hydraulic pump 1-relief valve 2-oil tank (unloading). Directional Control Valve

There is a problem: when the weight is descending, it emits beat-like vibration and noise. Directional Control Valve

All hydraulic components in the detection system are normal, so the problem of the system is not caused by the failure of the component itself. In the system, a throttle valve is used to adjust the descending speed of the plunger cylinder, so when the oil flows in the reverse direction, the hydraulic control check valve outlet pressure is backpressure. The control oil pressure is still the setting value of the overflow valve 6, so the force balance of the valve core is broken, the valve core drops to close the valve port, and the pressure in the oil outlet cavity becomes zero.

At this time, the control oil pressure set by the overflow valve 6 opens the hydraulic control check valve again, the oil flows in the reverse direction, and backpressure is generated in the reverse oil outlet cavity, and the hydraulic control check valve is closed again. This was repeated so that the plunger cylinder was lowered and stopped intermittently, and vibration and noise were emitted at the same time. Directional Control Valve

Método de solução

• Increase the control oil pressure. Increasing the setting pressure of the relief valve 6 means increasing the minimum control pressure, which can reduce vibration and noise within a certain range of the descending speed of the plunger cylinder, but is disadvantageous for saving the power of the control part. Directional Control Valve
• Change the setting of the throttle valve. Set the throttle valve above the hydraulic control check valve to make the hydraulic control check valve reverse the backpressure of the oil chamber to zero. This helps eliminate vibration and noise, but increases the power consumption when the plunger cylinder rises. Directional Control Valve
• Select the appropriate hydraulic valve. Choosing a hydraulically controlled check valve with an external drain port can eliminate vibration and noise. Directional Control Valve
• The problems exposed in the system are caused by the improper selection of component types. When selecting a hydraulic control check valve, in addition to knowing its function as a hydraulic lock, you must also understand its structure type. When there is backpressure, you should choose a hydraulic control check valve with an external drain. Directional Control Valve

Pergunta 4: A pressão do óleo de controle da válvula hidráulica do sistema hidráulico de posicionamento do espalhador de guindaste

Figure 1-7 shows the positioning hydraulic system of the container crane spreader, which can realize the movement and positioning of the container spreader. The hydraulic cylinder 5 is required to travel left and right in the horizontal direction and be accurately positioned at any position, without drifting or shifting, and its movement speed should be adjusted.

In order to meet the positioning requirements of the spreader, an external leakage type (with a load relief valve core) dual hydraulic control one-way valve 4 is set at the oil inlet and outlet ports of the hydraulic cylinder 5 to lock the hydraulic cylinder. Because of the four one-way valves, the oil can flow through the speed control valve in the same direction no matter the piston moves to the left or right, so the reciprocating speed of the piston is equal, and the system working pressure is set by the overflow valve 1. Directional Control Valve

Since the neutral function of the reversing valve 2 in the system is O type, when the reversing valve 2 is switched to the neutral position, the oil circuit between the hydraulic cylinder 5 and the reversing valve 2 is closed, and a certain pressure is still maintained, namely The control oil circuit of the hydraulic control check valve still has pressure, so that it cannot be closed immediately. The hydraulic control check valve is not closed until the control oil circuit pressure oil is relieved due to the internal leakage of the reversing valve.

Therefore, there is still a period of time from when the reversing valve is in the neutral position to when the piston stops moving, and the hydraulic cylinder cannot be positioned accurately. Directional Control Valve

Change the original system with the O-type reversing valve to the Y-type reversing valve. The improved system is shown in Figure 1-7. Due to the Y-type neutral function of the reversing valve, when the reversing valve is in the neutral position, the control oil circuit of the hydraulic control check valve is immediately connected to the oil tank, and the pressure drops rapidly, so the hydraulic control check valve can be closed in time and locked tightening effect.  Directional Control Valve

Pergunta 5: Seleção do tipo de válvula hidráulica para circuito de aumento de velocidade do acumulador

The hydraulic equipment made by a factory is shown in Figure 1-8. Due to the long intermittent time and the high-speed movement of the actuators, an accumulator is used as an auxiliary power source and used in conjunction with a hydraulic pump with a small flow rate. When the manual reversing valve 5 is in the neutral position, the hydraulic cylinder 6 stops and the hydraulic pump 1 charges the accumulator 4 through the one-way valve 2, and the accumulator stores energy at this time.

When the pressure of the accumulator reaches a certain set value, the pilot-operated external control sequence valve 3 for unloading is opened, so that the pressure oil output by pump 1 flows back to the tank through valve 3, and pump 1 is in the unloading state. When the left or right position of valve 5 is connected to the circuit, pump 1 and accumulator 4 simultaneously supply oil to the hydraulic cylinder 6 to make it move quickly. The set pressure of sequence valve 3 in the loop is higher than the maximum working pressure of the system to ensure that all the flow of pump 1 enters the system during the working stroke. Directional Control Valve

When the oil pressure from the accumulator drops due to the leakage at the pilot valve port, the pilot valve spool is closed, the main valve spool is also closed, and the unloading channel of the hydraulic pump is cut off, so the above sequence occurs The phenomenon of repeated opening and closing of the valve. Through the above analysis, it is concluded that the reason for the problem of the system is that the pilot-operated external control sequence valve is selected as the unloading valve. Directional Control Valve

Pergunta 6: O problema da válvula hidráulica do sistema hidráulico da máquina de revestimento de borracha butílica

In recent years, hollow glass doors and windows have been widely used due to their good heat insulation, sound insulation, anti-frost and sealing properties, and long service life. Butyl rubber is the first seal through aluminum hollow glass doors and windows. It is solid at room temperature and becomes semi-fluid when heated to 110～140℃. The glue can be extruded to realize glue application under the pressure of 12～15MPa. . Butyl coating is an indispensable link in the production process of aluminum hollow glass doors and windows.

The butyl rubber coating machine is special equipment designed and manufactured for this process. It heats, pressurizes, and extrudes the butyl rubber to evenly coat the middle of both sides of the aluminum spacer. Process requirements: The butyl rubber must be evenly coated and not cut off to ensure the performance of the hollow glass doors and windows. Directional Control Valve

The composition of the hydraulic system of the butyl rubber coating machine is shown in Figure 1-9. The systems are shown in Figure 1-9 and Figure 1-9 has been applied in practice, and the principles of the two are similar. Now take Figure 1-9 as an example for illustration.

The working principle is: when the 1YA is energized, the left position of the reversing valve is connected to the circuit, and the hydraulic cylinder 5 moves from right to left to extrude the butyl rubber for gluing. When the pressure in the rodless chamber of the hydraulic cylinder rises to the upper limit value of the electric contact pressure gauge 8, the pressure gauge contact sends a signal to de-energize the solenoid 1YA, the reversing valve is in the neutral position, and the hydraulic pump is closed at the same time, and the hydraulic cylinder is replaced by the hydraulic pressure. The one-way valve 4 and the accumulator 7 are controlled to maintain pressure.

When the pressure in the rodless chamber of the hydraulic cylinder drops to the lower limit set by the electric contact pressure gauge, the pressure gauge sends a signal to energize the 1YA, and the hydraulic pump supplies oil to the system again to increase the pressure in the rodless chamber, thereby causing the hydraulic cylinder The pressure remains within the required working range. When the piston of the hydraulic cylinder reaches the predetermined position before the endpoint, the electromagnet 2YA is energized,

the right position of the reversing valve is connected to the circuit, the hydraulic cylinder moves from left to right, and the piston rod retracts. It should be pointed out that the hydraulic cylinder 5 and the butyl rubber cylinder 6 are installed on the same horizontal line and fixed on the bracket respectively. The space between the two is used to fill the solid butyl rubber. Directional Control Valve

Problemas no sistema hidráulico da máquina de revestimento de borracha butílica: Durante a operação, verificou-se que a borracha butílica foi aplicada de forma desigual, e o fluxo de cola extrudada tornou-se cada vez mais fino até que o fluxo parou, e o desempenho das portas de vidro ocas e as janelas produzidas não atendiam aos requisitos. O sistema mostrado na Figura 1-9 deve ser protegido.

In the pressure performance test, when the hydraulic pump is not turned on and the manual control 1YA is energized, the pump reversal phenomenon also occurs. It is found that the two circuits shown in Figure 1-9 have certain defects: in the pressure holding stage, the energy storage The hydraulic oil in the hydraulic cylinder enters the rodless cavity of the hydraulic cylinder, but because the reversing valve adopts the M-type neutral function, the oil in the rod cavity of the hydraulic cylinder cannot return to the tank, that is, the oil return is closed, causing the piston of the hydraulic cylinder to be unable to move.

The glue cannot be squeezed out so that the glue flow becomes smaller and smaller until the flow stops at the end. For the system shown in Figure 1-9, when the hydraulic pump is not working and the left position of the reversing valve is turned on, the high pressure of the hydraulic oil in the accumulator causes the high-pressure oil to flow back into the hydraulic pump, causing the pump to reverse. Turn.

A Figura 1-10 é o diagrama esquemático do sistema hidráulico aprimorado da máquina de revestimento de borracha butílica. A função central da válvula de reversão adota o tipo K. No estágio de retenção de pressão, o cilindro hidráulico tem uma cavidade de haste para retornar o óleo, e o pistão do cilindro hidráulico pode continuar se movendo da esquerda para a direita dependendo da pressão do acumulador para que a cola possa ser aplicada.

Mesmo e nenhum corte ocorre. Na saída da bomba, uma válvula unidirecional é adicionada para prevenir efetivamente a reversão da bomba hidráulica causada pelo refluxo do óleo de alta pressão no acumulador.

Pergunta 7: A função central da válvula de reversão do sistema hidráulico da máquina hidráulica de moinho vertical

O princípio de funcionamento do moinho vertical é mostrado na Figura 1-11. As extremidades esquerda e direita do moinho são respectivamente conectadas às hastes dos cilindros hidráulicos esquerdo e direito.

A elevação do rebolo é controlada pela expansão e contração da haste do pistão do cilindro hidráulico. No processo de retificação, por um lado, o sistema hidráulico fornece pressão suficiente ao rebolo; por outro lado, o rebolo gira, o rebolo gira sob a ação do abrasivo e o movimento rotativo do rebolo é realizado pelo motor através da correia. O material no disco de moagem se move para a periferia do disco de moagem devido à força centrífuga que entra no canal, e o material é triturado sob a pressão e cisalhamento da máquina de moagem.

O sistema hidráulico da máquina hidráulica do moinho vertical é uma parte importante do moinho vertical, principalmente composto por um cilindro de óleo, acumuladores, tubulação hidráulica, estação hidráulica e outros componentes. Sua principal função é aplicar pressão suficiente no rebolo para esmagar o material. O princípio de funcionamento do sistema é o seguinte.

As shown in Figure 1-12, when the 1DT is energized, the left position of the reversing valve is connected to the circuit, the hydraulic cylinder 4 moves from up to down, and the grinding wheel moves down through the pressure provided by the hydraulic system. When the pressure in the rodless cavity of the hydraulic cylinder 4 rises to the upper limit of the electric contact pressure gauge 5, the pressure gauge contact sends a signal to de-energize the solenoid 1DT, the reversing valve is in the neutral position, and the hydraulic cylinder 4 is powered by the accumulator.

6 The leakage compensation system is working in the pressure-holding state; when the pressure of the rodless cavity of the hydraulic cylinder drops to the lower limit set by the electric contact pressure gauge 5, the contact of the electric contact pressure gauge 5 sends out a signal again, so that the 1DT is energized, and the hydraulic pump. The output hydraulic oil is sent to the system again.

O sistema é fornecido para aumentar a pressão da cavidade sem haste de modo que a pressão da cavidade sem haste do cilindro hidráulico seja mantida dentro da faixa de trabalho necessária. Quando o 2DT é energizado, a posição correta da válvula de reversão é conectada ao circuito, o cilindro hidráulico tem uma cavidade da haste para entrar no óleo e nenhuma cavidade da haste retorna o óleo e o pistão sobe. Quando o 1DT e o 2DT estão desligados, o sistema está em um estado neutro, conforme mostrado na figura.