Hydraulic transmission bulldozer reversing control method and bulldozer

Abstract

The invention provides a hydraulic transmission bulldozer reversing control method and a bulldozer, and belongs to the field of bulldozer control. According to the technical scheme, the hydraulic transmission bulldozer reversing control method comprises the steps that when the speed gear of a target driving gear is higher than the speed gear of a current driving gear, a direction gear is switched firstly, and then the speed gear is lifted to the speed gear of the target driving gear; when the speed gear of the target driving gear is lower than the speed gear of the current driving gear, the current speed gear is lowered to the speed gear of the target driving gear, the direction gear is kept unchanged at the moment, and then the direction gear is switched; and when the target gear speed gear is equal to the current gear speed gear, the direction gear is directly switched. According to the scheme, a driver only needs to directly conduct gear reversing operation, then the bulldozer conducts reversing automatically through gear judgment, the operation process is simplified, meanwhile, when the bulldozer conducts reversing at a low speed gear all the time, and gear shifting impact is reduced.

Description

Technical Field

[0001] The invention relates to the field of bulldozer control, in particular to a hydraulic transmission bulldozer reversing control method and a bulldozer. Background Art

[0002] Bulldozer is a kind of earth-moving machinery, mainly used for excavation, transportation and dumping of rock and soil. It is widely used in open-pit mines, construction dumps, leveling of automobile dumps, piling of scattered ore and rock, leveling of work platforms and construction sites. The main working condition of bulldozer is to shovel loose materials back and forth within a short distance. Due to the short single stroke, bulldozers generally use forward and backward reversing and switching between forward and backward during the back and forth process, rather than turning.

[0003] However, during the operation of a bulldozer, its own weight will generate huge inertia. If the gear is switched directly, there will be a strong switching shock, which will not only cause discomfort to the personnel, but also make the various parts of the bulldozer bear additional impact loads, thus affecting the mechanical life and performance. In order to reduce the switching shock, the common operation method of the driver is to first reduce the speed by coasting in neutral or braking the whole vehicle, then switch the gears, and finally achieve the switching.

[0004] However, this operation mode has obvious disadvantages: on the one hand, the operation process is complicated, which increases the labor intensity of the driver; on the other hand, frequent braking operations will accelerate the wear of the vehicle brakes and shorten their service life. Summary of the invention

[0005] Aiming at the problems of complicated operation and large gear shifting impact when the bulldozer is currently changing direction, the present invention provides a hydraulic transmission bulldozer changing direction control method.

[0006] In order to solve the above problems, the technical solution adopted by the present invention is a method for controlling the direction change of a hydraulic transmission bulldozer, wherein the bulldozer includes a plurality of driving gears, each of which includes a direction gear and a speed gear, the direction gear includes forward and backward, and the speed gear includes a plurality of speed intervals divided from small to large, and the method includes: S1. The driver switches from the current driving gear to the target driving gear, and the direction of the current gear is opposite to that of the target gear; S2. Through the control of the clutch and engine, execute: S2-1. When the target travel gear speed gear is higher than the current travel gear speed gear, first switch the direction gear, then the speed gear remains unchanged, and then the speed gear is increased to the target travel gear speed gear; S2-2. When the target travel gear speed gear is lower than the current travel gear speed gear, the current speed gear is reduced to the target travel gear speed gear, the direction gear remains unchanged, and then switch the direction gear; S2-3. When the target gear speed gear is equal to the current gear speed gear, directly switch the direction gear.

[0007] In this solution, the driver only needs to directly perform the gear shifting operation, and then the bulldozer will automatically change direction through gear judgment, which simplifies the operation process. At the same time, when changing direction, the bulldozer always operates at a lower speed gear, reducing the gear shifting shock.

[0008] Preferably, in step S2, when switching the direction gear, the following steps are included: S2.1 Ensure that the clutch pressure of the current speed gear remains unchanged and the clutch pressure of the current direction gear is released; S2.2 The engine speed is reduced, causing the torque converter to enter reverse or reverse operation to assist braking; S2.3 The clutch oil filling of the target direction gear reaches the KP point, and the corresponding planetary carrier becomes controlled; S2.4 The clutch pressure of the target gear increases to the set value, and the vehicle brakes; S2.5 When the transmission output speed drops to the set range, the braking process is considered to be completed and the vehicle switches to the target direction gear; S2.6 The engine resumes the set speed, the target direction gear clutch is engaged, and the reversing is completed.

[0009] Preferably, in step S2.4, the pressure of the clutch in the target direction gear is adjusted to control the rate of change of the output speed of the gearbox. By adjusting the pressure of the clutch in the target direction, the impact degree is ensured to be within a reasonable range.

[0010] Preferably, in step S2.4, the clutch engagement time of the target direction gear does not exceed the set maximum braking time, so as to avoid the clutch overheating damage, speed sensor failure and other hardware failures that cause switching failure.

[0011] Preferably, in step S2.2 and step S2.6, the engine is instructed to adjust the speed via CAN communication.

[0012] Preferably, the rate of change of the output speed of the gearbox is controlled by PID.

[0013] Preferably, in step S2.4, the clutch pressure of the target direction gear rises to a set value and is maintained for a certain period of time.

[0014] On the other hand, the present invention also provides a bulldozer, which adopts the above-mentioned hydraulic transmission bulldozer reversing control method.

[0015] It can be seen from the above technical solutions that the beneficial effect of the present invention is that in this solution, the driver only needs to operate the shift handle to switch gears according to the work requirements. The controller selects the corresponding method according to the current gear and the gear to be switched, controls the pressure of each clutch, and uses high and low gear switching, clutch slip, torque converter reverse transmission and reverse performance to achieve rapid braking of the whole vehicle. During this period, the vehicle speed change is tracked, PID control is performed, and the impact degree is reduced by adjusting the clutch pressure value to ensure comfort. After braking, reverse operation can be performed immediately to improve efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solution of the present invention, the accompanying drawings required for use in the description will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0017] Figure 1 This is a transmission diagram of the bulldozer's gearbox.

[0018] Figure 2 Schematic diagram of the pressure curve of the clutch of a bulldozer.

[0019] Figure 3 It is a schematic diagram of the pressure curves of the directional gear clutch and the speed gear clutch in the first embodiment of the present invention.

[0020] Figure 4 This is a flow chart of a method according to Embodiment 1 of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in this specific embodiment. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of them. Based on the embodiments in this patent, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this patent.

[0022] The bulldozer's travel power system includes the engine, torque converter, gearbox and other structures: In the torque converter, the pump wheel, guide wheel and turbine are the main structures. During normal transmission, the input shaft and output shaft rotate in the normal direction, and the input shaft speed is higher than the output shaft. The power of the engine is input from the pump wheel shaft and then output to the gearbox by the turbine shaft. When the vehicle is switching gears or reversing, the torque converter will be reversed or reversed.

[0023] The gearbox is mostly a planetary gearbox, including two direction gear clutches and multiple speed gear clutches. Figure 1 For example, it includes a forward gear clutch F, a reverse gear clutch R, and three speed gear clutches 1, 2, and 3. That is, through the engagement and disengagement of five clutches, the gearbox forms six driving gears of F1, F2, F3 and R1, R2, and R3, and gear shifting is achieved by switching the engagement and disengagement of the clutches.

[0024] The speed and torque of the sun gear, planet carrier and inner ring gear in each planetary mechanism can be calculated by formulas 1 and 2.

[0025]

[0026] Among them: S stands for the sun gear, R is the inner ring gear, C is the planet carrier; n is the speed, T is the torque, and Z is the number of teeth.

[0027] The power control system of a hydraulic transmission bulldozer consists of a controller, a shift handle, a foot accelerator, a hand accelerator, a brake pedal, a transmission input and output speed sensor, and a transmission clutch proportional valve.

[0028] The driver changes gears through the shift handle, controls the engine speed with the foot and hand accelerators, and controls the brakes with the brake pedal. In addition to determining the speed of each planetary gearbox, the input speed / output speed of the gearbox is also equal to the torque converter turbine speed. Combined with the engine speed (equal to the torque converter pump wheel speed), the torque converter state can be determined, judging whether it is a normal transmission condition, a reverse transmission condition, or a reverse condition. The output speed can determine the speed of the vehicle, and its change speed is the impact degree, which determines the driving comfort.

[0029] The controller reads the input data of the engine, shift handle, foot accelerator, hand accelerator, brake pedal, various speed sensors, etc., understands the driver's operating intention and the status of the bulldozer, and determines the control parameters of the engine and the control current of the clutch proportional valves of the transmission through internal program calculations to control the bulldozer to perform various walking movements.

[0030] During the gearbox shifting process, the typical clutch pressure curve is as follows Figure 2 , the meaning of each stage is as follows: In the waiting stage, there is no pressure in the clutch piston cavity, the clutch light plate and friction plate are separated, and the planetary carrier components controlled by the clutch rotate freely; During the oil filling stage, high oil pressure is provided for a short period of time to allow the oil to quickly fill the clutch piston cavity; KP point is the clutch engagement point. As the piston moves into position, the light plate and the friction plate begin to contact. At this time, the braking torque provided by the clutch is zero; In the boost phase, the pressure in the clutch piston cavity continues to rise, the braking torque also continues to rise, the planetary carrier component controlled by the clutch gradually stops rotating, and the planetary mechanism drives at a fixed speed ratio; In the rapid pressure increase stage, the pressure continues to rise, and the clutch can provide greater torque to ensure the transmission safety factor; Stable phase.

[0031] The total time for the normal gear shifting stages of oil filling, pressure boosting and rapid pressure boosting is usually within 1.0-1.6s.

[0032] Based on the above principle, this scheme provides a hydraulic transmission bulldozer reversing control method. In the following description, the six driving gears F1, F2, F3 and R1, R2, R3 define two indicators, namely, the direction gear and the speed gear. The direction gear includes forward and reverse, and the speed gear is the above-mentioned 1st, 2nd, and 3rd gear, which correspond to five clutches respectively. Figure 4 As shown, the method includes: S1. The driver switches from the current driving gear to the target driving gear, and the direction of the current gear is opposite to that of the target gear; S2. Through the control of the clutch and engine, selective execution: S2-1. When the target travel gear speed gear is higher than the current travel gear speed gear, first switch the direction gear, then the speed gear remains unchanged, and then the speed gear is increased to the target travel gear speed gear; S2-2. When the target travel gear speed gear is lower than the current travel gear speed gear, the current speed gear is reduced to the target travel gear speed gear, the direction gear remains unchanged, and then switch the direction gear; S2-3. When the target gear speed gear is equal to the current gear speed gear, directly switch the direction gear.

[0033] In the above three steps, when switching the direction gear, the current speed gear is the same as the target speed gear, and then the following specific steps are performed: S2.1 Ensure that the clutch pressure of the current speed gear remains unchanged and the clutch pressure of the current direction gear is released; S2.2 uses CAN communication to control the engine to reduce speed, so that the torque converter enters reverse or reverse working conditions to assist braking; S2.3 The clutch oil filling of the target direction gear reaches the KP point, and the corresponding planetary carrier becomes controlled; S2.4 The clutch pressure of the target direction gear rises to the set value and is maintained for a certain period of time. The vehicle brakes. During this process, the clutch pressure of the target direction gear is adjusted, and the rate of change of the gearbox output speed is PID controlled to ensure that the impact degree is within a reasonable range. At the same time, the maximum braking time of the directional clutch is obtained by looking up the table. An example is shown in Table 1. The clutch engagement time of the target direction gear does not exceed the set maximum braking time to avoid clutch overheating damage and hardware failures such as speed sensor failure, which may cause switching failure;

[0034] Table 1 S2.5 When the transmission output speed drops to the set range, the braking process is considered to be completed and the vehicle switches to the target direction gear; S2.6 uses CAN communication to control the engine to resume the set speed, the target direction gear clutch is engaged, and the reversing is completed.

[0035] Take F1 switching to R1 as an example: ① Control the current of each clutch proportional valve to ensure that the pressure of the 1st gear clutch remains unchanged, and the F direction clutch quickly releases pressure. At this time, the power transmission of the whole vehicle is interrupted, and it keeps moving forward under inertia; ② Use CAN communication to instruct the engine to reduce the speed, so that the torque converter enters the reverse or reverse working condition to assist braking; ③ Control the R direction clutch to complete the oil filling stage and KP point. At this time, the planetary carrier of the first row of planetary mechanisms controlled by it changes from a free state to a controlled state. The speed of each planetary carrier in the gearbox can be calculated by the speed formula; ④ Control the R direction clutch pressure to rise to the set value, as shown in Table 1, and keep it for a period of time. At this time, since the 1st gear clutch remains engaged, the braking torque of the R direction clutch and the reverse torque of the torque converter are The forward or reverse braking torque can be transmitted to the output end of the gearbox to brake the entire vehicle; ⑤ During this period, the controller performs PID control on the output speed change rate, and adjusts the R direction clutch pressure to ensure that the impact degree is within a reasonable range; ⑥ During this period, the controller looks up the table to obtain the longest braking time of the direction clutch, an example is shown in Table 1, to avoid clutch overheating damage, and hardware failures such as speed sensor failure, which cause switching failure; ⑦ When the gearbox output speed drops to a certain range, it is considered that the braking process is over and the vehicle can start to switch to reverse; ⑧ Use CAN communication to instruct the engine to restore the throttle set speed to increase the torque converter output torque; ⑨ The R direction clutch pressure rises rapidly, the vehicle moves backward according to the speed ratio, and the switching is completed.

[0036] In the above process, the pressure curve diagram of the 1st gear clutch, the F gear clutch and the R gear clutch is as follows: Figure 3 shown.

[0037] In addition, the correspondence of each case is shown in Table 2:

[0038] Table 2 Embodiment 2 Based on the reversing control method provided in the first embodiment, this embodiment further provides a bulldozer, which adopts the rapid reversing control method of the hydraulic transmission bulldozer in the first embodiment.

[0039] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for controlling the direction change of a hydraulically driven bulldozer, wherein the bulldozer comprises a plurality of travel gears, each travel gear comprises a direction gear and a speed gear, the direction gear comprises forward and reverse, and the speed gear comprises a plurality of speed intervals divided from small to large, characterized in that: Methods include: S1. The driver switches from the current driving gear to the target driving gear, and the direction of the current gear is opposite to that of the target gear; S2. Through the control of the clutch and engine, execute: S2-1. When the target travel gear speed gear is higher than the current travel gear speed gear, first switch the direction gear, then the speed gear remains unchanged, and then the speed gear is increased to the target travel gear speed gear; S2-2. When the target travel gear speed gear is lower than the current travel gear speed gear, the current speed gear is reduced to the target travel gear speed gear, the direction gear remains unchanged, and then switch the direction gear; S2-3. When the target gear speed gear is equal to the current gear speed gear, directly switch the direction gear.

2. The hydraulic transmission bulldozer reversing control method according to claim 1, characterized in that: In step S2, when switching the direction gear, the following steps are included: S2.1 Ensure that the clutch pressure of the current speed gear remains unchanged and the clutch pressure of the current direction gear is released; S2.2 The engine speed is reduced, causing the torque converter to enter reverse or reverse operation to assist braking; S2.3 The clutch oil filling of the target direction gear reaches the KP point, and the corresponding planetary carrier becomes controlled; S2.4 The clutch pressure of the target gear increases to the set value, and the vehicle brakes; S2.5 When the transmission output speed drops to the set range, the braking process is considered to be completed and the vehicle switches to the target direction gear; S2.6 The engine resumes the set speed, the target direction gear clutch is engaged, and the reversing is completed.

3. The hydraulic transmission bulldozer reversing control method according to claim 2, characterized in that: In step S2.4, the pressure of the clutch of the target direction gear is adjusted to control the rate of change of the output speed of the transmission.

4. The hydraulic transmission bulldozer reversing control method according to claim 2, characterized in that: In step S2.4, the clutch engagement time of the target direction gear does not exceed the set maximum braking time.

5. The hydraulic transmission bulldozer reversing control method according to claim 2, characterized in that: In step S2.2 and step S2.6, the engine is instructed to adjust the speed via CAN communication.

6. The hydraulic transmission bulldozer reversing control method according to claim 3, characterized in that: The rate of change of the gearbox output speed is controlled by PID.

7. The hydraulic transmission bulldozer reversing control method according to claim 2, characterized in that: In step S2.4, the clutch pressure of the target direction gear is increased to a set value and maintained for a certain period of time.

8. A bulldozer, characterized in that: A hydraulic transmission bulldozer reversing control method as described in any one of claims 1 to 7 is adopted.

Images