During the use of a certain type of lithium pallet truck
, the operator found that its hydraulic transmission had a relatively strong shifting shock in terms of shift control. The shift shock not only reduces the service life of the transmission components and the reliability of the vehicle, but also reduces the comfort of the driver. In order to solve the problem of strong shift shock, we decided to improve the shift control system of the hydraulic transmission. 1. Improve the front shift control principle. The shift control system of the hydraulic transmission of this type of lithium pallet truck before the improvement is mainly composed of the pressure regulating valve 1, the pilot valve 2, the shift valve 3, the reverse gear clutch 4, the forward gear clutch 5, and the reversing valve 6. , The accumulator 7 and the micro valve 8 are composed, as shown in Figure 1. The system pressure oil is divided into 2 roads at node a: one road of pressure oil enters the pilot valve 2 to control the shift valve 3; the other road of pressure oil enters the node b and is divided into 3 roads. After the first channel of pressure oil passes through node c, it enters the reversing valve 6. The second path enters the accumulator 7 via the pressure regulating valve 1. The third way goes directly to the micro valve 8. After the pressure oil enters the reversing valve 6, according to the working gear of the whole vehicle, it can be divided into the following 5 working states: one is the neutral state, the second is the forward Ⅰ work, the third is the forward Ⅱ work, the fourth is the reverse gear one work, and the fifth is Work backward in second gear. (1) Neutral state. At this time, the reversing valve 6 is in the neutral state, the pilot valve 2 is in the de-energized state, and there is no pressure oil in the four clutches of R1, R2, F1, F2, and the lithium pallet truck has no power output at this time. (2) Forward Ⅰ work. At this time, the control coil SF of the reversing valve 6 is energized and the right position is turned on, the pilot valve 2 is in a de-energized state, and the pressure oil enters the forward clutch F1 through the shift valve 3 in the right position. The forklift runs at the first gear speed. (3) Forward Ⅱ gear works. At this time, the directional valve 6 is still in the right-position conduction state, the pilot valve 2 is energized and is in the lower-position conduction state, the shift valve 3 is switched to the left-position conduction state, and the pressure oil passes through the shift valve. 3 Enter the forward second gear clutch F2, at this time the forklift runs at the second gear speed. (4) Reverse first gear work. At this time, the control coil SR of the reversing valve 6 is energized and is in the left-position conductive state, the pilot valve 2 is in a power-off state, and the pressure oil enters the reverse clutch R1 through the shift valve 3, and the forklift presses Reverse the first gear speed. (5) Reverse Ⅰ gear work. At this time, the reversing valve 6 is still in the left conduction state, the pilot valve 2 is energized and is in the lower conduction state, and the pressure oil enters the reverse Ⅱ gear clutch R2 through the shift valve 3. At this time, the vehicle presses The vehicle runs at the second gear speed in the reverse direction. 2. The overall idea of u200bu200bthe improvement plan is as follows: on the basis of retaining the original shift control system structure, a proportional pressure reducing valve is added between the pressure regulating valve and the reversing valve to achieve proportional control; at the same time in the shift valve The oil return port is equipped with an adjustable throttle valve to make the pressure inside the clutch change according to a predetermined rule. The principle of the improved shift control system is shown in Figure 2. First, on the basis of keeping the original control valve unchanged, a proportional pressure reducing valve 8 is connected in series in the main control oil circuit of the system. The proportional pressure reducing valve is a cartridge valve, which is installed on the side of the control valve body, as shown in Figure 3. By adjusting the control handle of the proportional pressure reducing valve, the pressure oil entering the reversing valve 7 can be controlled to reduce the shift shock. Secondly, install an adjustable throttle valve 6 in the oil return path of the clutch shift valve. The function of installing the adjustable throttle valve 6 is to delay the gear disengagement time, so that the other gear has enough engagement time, so as to prevent serious impact when shifting. 3. Improved effect The improved shift control system has the following two advantages: one is simple structure, low cost of improvement, convenient installation and maintenance; second, stable performance and long service life. After refitting according to the above scheme, the reliability, durability and riding comfort of the whole vehicle have been effectively improved, and it has been widely recognized by the market.
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