Hydraulic transmission bulldozer reversing control method and bulldozer

Abstract

The application provides a hydraulic transmission bulldozer reversing control method and a bulldozer, and belongs to the field of bulldozer control. The technical scheme is as follows: a hydraulic transmission bulldozer reversing control method comprises the following steps: when the speed gear of the target driving gear is higher than the speed gear of the current driving gear, the direction gear is switched first, and then the speed gear is raised 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, at this time, the direction gear remains unchanged, and then the direction gear is switched; when the speed gear of the target gear is equal to the speed gear of the current gear, the direction gear is directly switched. In the scheme, the driver only needs to directly operate the reversing gear, and then the bulldozer automatically reverses through gear judgment, so that the operation process is simplified, and the bulldozer always operates at a lower speed gear when reversing, so that the gear impact is reduced.

Description

Technical Field

[0001] This invention relates to the field of bulldozer control, and in particular to a reversing control method for a hydraulically driven bulldozer, as well as a bulldozer. Background Technology

[0002] A bulldozer is a type of earthmoving machinery primarily used for excavating, transporting, and disposing of soil and rock. It is widely used in open-pit mines, constructing spoil heaps, leveling truck spoil heaps, stockpiling loose ore and rock, leveling work platforms, and building sites. The main operating condition of a bulldozer is to scoop and transport loose materials back and forth over short distances. Due to its short single-trip distance, bulldozers typically use forward and reverse switching during the back-and-forth movement, rather than steering.

[0003] However, during operation, the bulldozer's own weight generates enormous inertia. Directly shifting gears would result in a strong reversing impact, which not only causes discomfort to the crew but also subjects the bulldozer's components to additional impact loads, thus affecting the machine's lifespan and performance. To reduce reversing impact, drivers typically reduce speed by first coasting in neutral or applying the full brakes, then shift gears to achieve the reversing action.

[0004] However, this operating method has obvious drawbacks: 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's brakes and shorten their service life. Summary of the Invention

[0005] This invention addresses the problems of cumbersome operation and large shifting impact when reversing bulldozers, and provides a hydraulic transmission bulldozer reversing control method.

[0006] To solve the above problems, the technical solution adopted by the present invention is a hydraulic transmission bulldozer reversing control method. The bulldozer includes multiple driving gears, each driving gear including a direction gear and a speed gear. The direction gear includes forward and reverse, and the speed gear includes multiple speed ranges divided from small to large. The method includes:

[0007] S1. The driver switches from the current driving gear to the target driving gear, with the current gear being the opposite in direction to the target gear;

[0008] S2. By controlling the clutch and engine, execute:

[0009] S2-1. When the speed gear of the target driving gear is higher than the speed gear of the current driving gear, first switch the steering gear, while keeping the speed gear unchanged, and then shift the speed gear to the speed gear of the target driving gear;

[0010] S2-2. When the speed of the target driving gear is lower than the speed of the current driving gear, the current speed gear is downgraded to the speed of the target driving gear. At this time, the steering gear remains unchanged, and then the steering gear is switched.

[0011] S2-3. When the target gear speed is equal to the current gear speed, directly switch to the direction gear.

[0012] In this solution, the driver only needs to perform the gear shifting operation, and the bulldozer will automatically shift direction based on the gear position, which simplifies the operation process. At the same time, the bulldozer always shifts at a lower speed gear during the shifting process, reducing the impact of gear shifting.

[0013] Preferably, in step S2, when switching the direction gear, the following steps are included:

[0014] S2.1 Ensure that the clutch pressure of the current speed gear remains unchanged, and release the clutch pressure of the current direction gear;

[0015] S2.2 The engine speed is reduced, causing the torque converter to enter reverse transmission or reverse operation to assist braking;

[0016] S2.3 The clutch of the target direction gear is filled with oil to point KP, and the corresponding planetary carrier becomes controlled.

[0017] S2.4 When the clutch pressure of the target direction gear rises to the set value, the vehicle brakes.

[0018] When the S2.5 transmission output speed drops to the set range, the braking process is considered to be over, and the vehicle switches to the gear in the target direction.

[0019] S2.6 The engine returns to the set speed, the target direction gear clutch engages, and the reversing ends.

[0020] Preferably, in step S2.4, the clutch pressure of the target direction gear is adjusted to control the rate of change of the transmission output speed. By adjusting the clutch pressure in the target direction, the impact is ensured to be within a reasonable range.

[0021] Preferably, in step S2.4, the clutch engagement time of the target direction gear does not exceed the set maximum braking time. This avoids reversing failure caused by clutch overheating and damage, as well as hardware failures such as speed sensor malfunction.

[0022] Preferably, in steps S2.2 and S2.6, the engine speed is adjusted via CAN communication.

[0023] Preferably, the rate of change of the gearbox output speed is controlled by PID.

[0024] 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.

[0025] On the other hand, the present invention also provides a bulldozer that employs the above-described hydraulic transmission bulldozer reversing control method.

[0026] As can be seen from the above technical solution, the beneficial effects of this invention are as follows: In this solution, the driver only needs to operate the gear shift lever to switch gears according to the operational requirements. The controller selects the corresponding method based on the current gear and the gear to be switched to, and controls the pressure of each clutch. By utilizing high and low gear switching, clutch slippage, torque converter reverse transmission, and reverse rotation performance, the vehicle can achieve rapid braking. During this process, the controller tracks changes in vehicle speed and performs PID control, adjusting the clutch pressure value to reduce impact and ensure comfort. After braking, reverse operation can be performed immediately, improving efficiency. Attached Figure Description

[0027] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a simplified diagram of the gearbox of a bulldozer.

[0029] Figure 2 This is a schematic diagram of the pressure curve of a bulldozer's clutch.

[0030] Figure 3 This is a schematic diagram of the pressure curves of the directional gear clutch and the speed gear clutch in Embodiment 1 of the present invention.

[0031] Figure 4 This is a flowchart of the method according to Embodiment 1 of the present invention. Detailed Implementation

[0032] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the specific embodiments. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this patent, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this patent.

[0033] The bulldozer's walking power system includes structures such as the engine, hydraulic torque converter, and gearbox:

[0034] In a hydraulic torque converter, the pump impeller, guide impeller, and turbine are the main components. During normal transmission, both the input and output shafts rotate in their normal directions, with the input shaft rotating at a higher speed than the output shaft. The engine's power is input through the pump impeller shaft and then output to the transmission through the turbine shaft. However, during gear shifting or reversing operations, the hydraulic torque converter may experience reverse transmission or reverse rotation.

[0035] Most transmissions use planetary transmissions, which include two directional gear clutches and multiple speed gear clutches, to... Figure 1 For example, it includes a forward clutch F, a reverse clutch R, and three speed gear clutches 1, 2, and 3. That is, through the engagement and disengagement of the five clutches, the transmission forms six driving gears: F1, F2, F3, R1, R2, and R3. At the same time, gear shifting is achieved by switching the engagement and disengagement of the clutches.

[0036] The rotational speeds and torques of the sun gear, planet carrier, and internal gear ring in each planetary mechanism can be calculated using formulas 1 and 2.

[0037]

[0038] Where: S represents the sun gear, R represents the internal gear ring, C represents the planet carrier; n represents the rotational speed, T represents the torque, and Z represents the number of teeth.

[0039] The power control system of a hydraulically driven bulldozer consists of a controller, gear shift lever, foot throttle, hand throttle, brake pedal, input and output speed sensors of the gearbox, and proportional valves of each clutch of the gearbox.

[0040] The driver uses the gear shift lever to change gears, the foot accelerator and hand accelerator to control engine speed, and the brake pedal to control the brakes. The input / output speed of the transmission not only determines the speed of each planetary gear set within the transmission, but the input speed is also equal to the torque converter turbine speed. Combined with the engine speed (which equals the torque converter pump impeller speed), the torque converter state can be determined, identifying whether it is in normal transmission, reverse transmission, or reverse transmission mode. The output speed determines the vehicle speed; its rate of change reflects the magnitude of the impact, thus determining ride comfort.

[0041] The controller reads input data from the engine, gear shift lever, foot throttle, hand throttle, brake pedal, and various speed sensors to understand the driver's operating intentions and the overall status of the bulldozer. Through internal program calculations, it determines the engine control parameters and the control current of the proportional valves of each clutch in the gearbox to control the bulldozer to perform various walking actions.

[0042] During gearbox shifting, a typical clutch pressure curve is as follows: Figure 2 The meaning of each stage is as follows:

[0043] During the waiting phase, there is no pressure in the clutch piston chamber, the clutch discs and friction discs separate, and the planetary carrier components controlled by the clutch rotate freely.

[0044] During the oil filling stage, a short period of high oil pressure is provided to quickly fill the clutch piston chamber with oil.

[0045] KP point is the clutch engagement point. As the piston moves into position, the light plate and the friction plate begin to contact each other. At this time, the braking torque provided by the clutch is zero.

[0046] During the pressurization phase, the pressure inside the clutch piston chamber continues to rise, and the braking torque also continues to rise. The planetary carrier components controlled by the clutch gradually stop rotating, and the planetary mechanism transmits power at a fixed speed ratio.

[0047] During the rapid pressurization phase, as the pressure continues to rise, the clutch can provide greater torque to ensure a safe transmission factor.

[0048] Stable phase.

[0049] The total time for the normal gear shift stages of oil filling, boosting, and rapid boosting is usually within 1.0-1.6 seconds.

[0050] Based on the above principles, this solution provides a hydraulic transmission bulldozer reversing control method. In the following description, the six driving gears F1, F2, F3, and R1, R2, R3 are defined with two indicators: directional gear and speed gear. The directional gears include forward and reverse, and the speed gears are the aforementioned gears 1, 2, and 3, corresponding to the five clutches respectively. Figure 4 As shown, this method includes:

[0051] S1. The driver switches from the current driving gear to the target driving gear, with the current gear being the opposite in direction to the target gear;

[0052] S2. Selective execution through control of the clutch and engine:

[0053] S2-1. When the speed gear of the target driving gear is higher than the speed gear of the current driving gear, first switch the steering gear, while keeping the speed gear unchanged, and then shift the speed gear to the speed gear of the target driving gear;

[0054] S2-2. When the speed of the target driving gear is lower than the speed of the current driving gear, the current speed gear is downgraded to the speed of the target driving gear. At this time, the steering gear remains unchanged, and then the steering gear is switched.

[0055] S2-3. When the target gear speed is equal to the current gear speed, directly switch to the direction gear.

[0056] In the above three steps, when switching gears, the current speed gear is the same as the target speed gear, and then the following specific steps are performed:

[0057] S2.1 Ensure that the clutch pressure of the current speed gear remains unchanged, and release the clutch pressure of the current direction gear;

[0058] S2.2 Utilizes CAN communication to control the engine to reduce its speed, causing the torque converter to enter reverse transmission or reverse operation mode to assist braking;

[0059] S2.3 The clutch of the target direction gear is filled with oil to point KP, and the corresponding planetary carrier becomes controlled.

[0060] 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. During this process, the clutch pressure of the target direction gear is adjusted, and the rate of change of the gearbox output speed is controlled by PID to ensure that the impact is within a reasonable range. At the same time, the maximum braking time of the direction clutch is obtained by referring to the table. See Table 1 for an example. The clutch engagement time of the target direction gear does not exceed the set maximum braking time to avoid overheating and damage to the clutch, as well as hardware failures such as speed sensor malfunction, which may cause reversing failure.

[0061]

[0062] Table 1

[0063] When the S2.5 transmission output speed drops to the set range, the braking process is considered to be over, and the vehicle switches to the gear in the target direction.

[0064] S2.6 uses CAN communication to control the engine to restore the set speed, the target direction gear clutch completes engagement, and the reversing ends.

[0065] Taking F1 to R1 shift as an example: ① Control the current of each clutch proportional valve to ensure that the pressure of the 1st gear clutch remains constant, and the F-direction clutch quickly releases pressure. At this time, the power transmission of the entire vehicle is interrupted, and it continues to move forward under inertia; ② Use CAN communication to instruct the engine to reduce its speed, so that the torque converter enters the reverse transmission or reverse operation 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 planetary mechanism 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, see Table 1 for an example, and maintain 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 reduced. The braking torque can be transmitted or reversed to the output end of the transmission 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 is within a reasonable range; ⑥ During this period, the controller looks up the maximum braking time of the direction clutch in a table (see Table 1 for an example) to avoid overheating damage to the clutch and hardware failures such as speed sensor malfunction, which could cause reversing failure; ⑦ When the transmission output speed drops to a certain range, the braking process is considered to be over, and the vehicle can begin to switch to reverse; ⑧ Using CAN communication, the engine is instructed to restore the throttle set speed to increase the torque converter output torque; ⑨ The R-direction clutch pressure rises rapidly, and the vehicle reverses according to the speed ratio, ending the reversing.

[0066] The pressure curves of the 1st gear clutch, F gear clutch, and R gear clutch during the above process are shown in the diagram below. Figure 3 As shown.

[0067] In addition, the correspondence for each case is shown in Table 2:

[0068]

[0069] Table 2

[0070] Example 2

[0071] Based on the reversing control method provided in Embodiment 1, this embodiment further provides a bulldozer that adopts the rapid reversing control method for a hydraulically driven bulldozer in Embodiment 1.

[0072] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those 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 invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A hydraulic transmission bulldozer reversing control method, the bulldozer including a plurality of travel ranges, each travel range including a direction range and a speed range, the direction range including forward and reverse, the speed range including a plurality of speed intervals divided from small to large, characterized by, The method comprises: S1. The driver switches from the current driving gear to the target driving gear, the direction gear of the current gear being opposite to that of the target gear; S2. By controlling the clutch and the engine, the following is performed: S2-1. When the speed gear of the target driving gear is higher than that of the current driving gear, the direction gear is switched first, at which time the speed gear remains unchanged, and then the speed gear is raised to the speed gear of the target driving gear; S2-2. When the speed gear of the target driving gear is lower than that of the current driving gear, the current speed gear is lowered to the speed gear of the target driving gear, at which time the direction gear remains unchanged, and then the direction gear is switched; S2-3. When the speed gear of the target gear is equal to that of the current gear, the direction gear is directly switched; In step S2, when the direction gear is switched, the following steps are included: S2.

1. The clutch pressure of the current speed gear is kept unchanged, and the clutch of the current direction gear is depressurized; S2.

2. The engine is lowered in speed, so that the torque converter enters a reverse transmission or reverse rotation working condition, to assist braking; S2.

3. The clutch of the target direction gear is filled with oil to reach a KP point, and the corresponding planet carrier becomes a controlled state; S2.

4. The clutch pressure of the target direction gear is raised to a set value, and the vehicle is braked; S2.

5. When the output speed of the gearbox is lowered to a set range, it is considered that the braking process is completed, and the vehicle is switched to the target direction gear; S2.

6. The engine is restored to a set speed, and the clutch of the target direction gear is completed, and the reversing is ended.

2. The hydraulic drive bulldozer reversal control method of claim 1, wherein, In step S2.4, the pressure of the clutch of the target direction gear is adjusted to control the change rate of the output speed of the gearbox.

3. The hydraulic drive bulldozer swing control method as set forth in claim 1, wherein, In step S2.4, the clutch engagement time of the target direction gear does not exceed a set maximum braking time.

4. The hydraulic drive bulldozer swing control method as set forth in claim 1, wherein In steps S2.2 and S2.6, the engine speed is adjusted through CAN communication.

5. The hydraulic drive bulldozer swing control method as set forth in claim 2, wherein The change rate of the output speed of the gearbox is controlled by PID.

6. The hydraulic drive bulldozer swing control method as set forth in claim 1, wherein, In step S2.4, the clutch pressure of the target direction gear is raised to a set value and maintained for a certain period of time.

7. A bulldozer characterized by The hydraulic transmission bulldozer reversing control method according to any one of claims 1-6 is adopted.

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