Hydraulic transmission system and control method

Abstract

This application relates to the field of engineering machinery technology, and in particular to a hydraulic transmission system and control method. The main pump of the hydraulic transmission system drives a first drive mechanism and a second drive mechanism via oil passages. A pressure sensor in the hydraulic transmission system detects the system pressure and sends the detected system pressure to a controller. When the system pressure is less than or equal to a first predetermined pressure, the first and second drive mechanisms operate in series. When the system pressure is greater than the first predetermined pressure, the first and second drive mechanisms operate in parallel. In parallel mode, when the system pressure is less than or equal to a second predetermined pressure, the first and second drive mechanisms operate in series. The hydraulic transmission system and control method of this application solve the technical problems of traditional hydrostatic series transmission systems causing damage to hydraulic components under high loads due to excessive system pressure, and the need for a large main pump displacement in parallel transmission systems to achieve the same maximum speed.

Description

Technical Field

[0001] This application relates to the field of engineering machinery technology, and in particular to a hydraulic transmission system and control method. Background Technology

[0002] With the standardization of infrastructure construction, agricultural development and other projects, the target market for construction machinery is becoming more and more segmented, the operating conditions are becoming more and more complex, the construction scope is becoming wider and wider, the implementation period is becoming shorter and shorter, and the working time of the whole machine is becoming longer and longer. How to reduce the failure rate of the whole machine and improve the uptime and work efficiency of the whole machine has become an important issue.

[0003] Traditional small hydrostatic travel motor drive systems are generally either series or parallel. In series drive systems, excessively high system pressure under high loads can easily damage hydraulic components and reduce the overall lifespan of the machine. Parallel drive systems require a larger main pump displacement to achieve the same maximum speed, resulting in higher system costs. Summary of the Invention

[0004] The purpose of this application is to provide a hydraulic transmission system and control method, which to a certain extent solves the technical problems of traditional small hydrostatic series transmission systems, where excessive system pressure under high load conditions can easily cause damage to the hydraulic components of the whole machine, and parallel transmission systems, which require a large main pump displacement and high system cost to achieve the same maximum speed.

[0005] According to a first aspect of this application, a hydraulic transmission system is provided, including a main pump, a first drive mechanism, a second drive mechanism, a pressure sensor, and a controller; the main pump drives the first drive mechanism and the second drive mechanism through oil passages; the controller pre-stores a first predetermined pressure value and a second predetermined pressure value, wherein the first predetermined pressure value is greater than the second predetermined pressure value; the pressure sensor is capable of detecting system pressure and sending the detected system pressure to the controller; when the system pressure is less than or equal to the first predetermined pressure, the controller controls the first drive mechanism and the second drive mechanism to perform a series mode; when the system pressure is greater than the first predetermined pressure, the controller controls the first drive mechanism and the second drive mechanism to perform a parallel mode; in the parallel mode, when the system pressure is less than or equal to the second predetermined pressure, the controller controls the first drive mechanism and the second drive mechanism to perform a series mode.

[0006] Based on the above technical features, preferably, when the system pressure is greater than the first predetermined pressure, and the displacement required by the main pump at the current vehicle speed is less than or equal to the maximum displacement of the main pump, the controller controls the first drive mechanism and the second drive mechanism to execute parallel mode; when the system pressure is greater than the first predetermined pressure, and the displacement required by the main pump at the current vehicle speed is greater than the maximum displacement of the main pump, the controller controls the vehicle speed to decrease to the maximum vehicle speed of the main pump's maximum displacement in parallel mode.

[0007] Based on the above technical features, preferably, in parallel mode, when the system pressure is greater than the second predetermined pressure and V1≤λ*V, the controller controls the first drive mechanism and the second drive mechanism to execute the series mode; where λ is the safety factor for determining whether the vehicle is slipping, V is the theoretical vehicle speed, and V1 is the actual vehicle speed; in parallel mode, when the system pressure is greater than the second predetermined pressure and V1>λ*V, the first drive mechanism and the second drive mechanism continue to execute the parallel mode.

[0008] Based on the above technical features, preferably, the controller controls the main pump to output a corresponding flow rate according to the original actual vehicle speed: Q = X * V1 * I * V m / (η*10 3 ), where X is the number of travel motors, V1 is the original actual vehicle speed, I is the transmission ratio, and V m η represents the displacement of the walking motor, and η represents the total efficiency of the walking motor; both the first drive mechanism and the second drive mechanism are walking motors.

[0009] Based on the above technical features, preferably, the controller adjusts the displacement of the main pump according to T = P * Q / (2π * n): where T is the main pump torque, Q is the main pump flow rate, P is the main pump pressure, and n is the main pump speed; the controller compares the input torque of the main pump with the output torque of the engine, and if the main pump torque is greater than or equal to the engine output torque, the controller controls the displacement of the main pump to decrease.

[0010] Based on the above technical features, preferably, the hydraulic transmission system further includes a replenishing pump, a proportional directional valve, and a swashplate angle adjuster; the replenishing pump can adjust the displacement of the main pump via the proportional directional valve and the swashplate angle adjuster, thereby adjusting the vehicle speed; the controller can output a corresponding current value to control the opening of the proportional directional valve so as to adjust the displacement of the main pump via the swashplate angle adjuster.

[0011] Based on the above technical features, preferably, the hydraulic transmission system further includes a high-pressure shut-off valve and an oil tank; the high-pressure shut-off valve includes a pressure-reducing valve and a shuttle valve; the two inlets of the shuttle valve are respectively connected to the first and second oil ports of the main pump, and the outlet of the shuttle valve is connected to the first inlet of the pressure-reducing valve; the second inlet of the pressure-reducing valve is connected to either the first or second oil port of the main pump, and the outlet of the pressure-reducing valve is connected to the oil tank; when the system pressure is greater than a third predetermined pressure, the second inlet of the pressure-reducing valve is connected to the outlet of the pressure-reducing valve; the pressure sensor detects the pressure at the outlet of the shuttle valve.

[0012] According to a second aspect of this application, a control method for a hydraulic transmission system is provided, the control method comprising:

[0013] Determine whether the system pressure is less than or equal to the first predetermined pressure;

[0014] If the system pressure is less than or equal to the first predetermined pressure, the first drive mechanism and the second drive mechanism shall operate in series.

[0015] If the system pressure is greater than the first predetermined pressure, the first drive mechanism and the second drive mechanism will operate in parallel mode;

[0016] In parallel operation mode, determine whether the system pressure is less than or equal to the second predetermined pressure;

[0017] If the system pressure is less than or equal to the second predetermined pressure, the first drive mechanism and the second drive mechanism operate in series; wherein the first predetermined pressure value is greater than the second predetermined pressure value.

[0018] Based on the above technical features, preferably, the step of determining whether the system pressure is less than or equal to the first predetermined pressure includes:

[0019] If the system pressure is greater than the first predetermined pressure, and the displacement required by the main pump at the current vehicle speed is less than or equal to the maximum displacement of the main pump, the first drive mechanism and the second drive mechanism shall operate in parallel mode.

[0020] If the system pressure is greater than the first predetermined pressure, and the displacement required by the main pump at the current vehicle speed is greater than the maximum displacement of the main pump, the vehicle speed is reduced to the maximum vehicle speed of the main pump in parallel mode.

[0021] Based on the above technical features, preferably, in parallel mode, the step of determining whether the system pressure is less than or equal to the second predetermined pressure includes:

[0022] If the system pressure is greater than the second predetermined pressure and V1≤λ*V, the first drive mechanism and the second drive mechanism execute the series mode; where λ is the safety factor for determining whether the vehicle is slipping, V is the theoretical vehicle speed, and V1 is the actual vehicle speed.

[0023] If the system pressure is greater than the second predetermined pressure and V1 > λ*V, the first drive mechanism and the second drive mechanism will operate in parallel mode.

[0024] The hydraulic transmission system of this application includes a main pump, a first drive mechanism, a second drive mechanism, a pressure sensor, and a controller. The main pump drives the first and second drive mechanisms via oil passages. The controller pre-stores a first predetermined pressure value and a second predetermined pressure value, where the first predetermined pressure value is greater than the second predetermined pressure value. The pressure sensor detects the system pressure and sends the detected system pressure to the controller. When the system pressure is less than or equal to the first predetermined pressure, the controller controls the first and second drive mechanisms to operate in series. When the system pressure is greater than the first predetermined pressure, the controller controls the first and second drive mechanisms to operate in parallel. In parallel mode, when the system pressure is less than or equal to the second predetermined pressure, the controller controls the first and second drive mechanisms to operate in series.

[0025] Based on the above technical features, the beneficial effects of this application are as follows:

[0026] In the hydraulic transmission system of this application, when the detected system pressure is less than or equal to a first predetermined pressure, the controller controls the first and second drive mechanisms to execute a series mode. At this time, the hydraulic transmission system can achieve a higher overall speed using a small-displacement main pump (the advantage of this series mode is that the displacement of the main pump can be reduced, thereby achieving cost reduction). This series mode continues until the system pressure exceeds the first predetermined pressure; that is, when the system pressure exceeds the first predetermined pressure, the controller controls the first and second drive mechanisms to execute a parallel mode. In this parallel mode, the system pressure will inevitably decrease, avoiding damage to the hydraulic components due to excessive system pressure and effectively extending the life of the hydraulic components. When the system pressure is less than or equal to a second predetermined pressure, it switches back to the series mode, at which point the hydraulic transmission system can achieve a higher overall speed using a small-displacement main pump.

[0027] In summary, the hydraulic transmission system of this application switches between series and parallel modes, which has the advantage of a small displacement main pump in the series mode, and can also prevent the problem of high pressure at the main pump port and high system pressure in the series mode, which could damage the hydraulic components of the whole machine.

[0028] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the hydraulic transmission system according to an embodiment of this application;

[0031] Figure 2 This is a schematic diagram of a hydraulic series transmission system in the prior art;

[0032] Figure 3 This is a schematic diagram of a hydraulic parallel transmission system in the prior art;

[0033] Figure 4 This is a schematic diagram of the hydraulic transmission system according to an embodiment of this application.

[0034] Figure label:

[0035] 1-Main pump; 101-Swashplate angle adjuster; 102-Proportional directional valve; 3-First one-way replenishing valve; 4-Second one-way replenishing valve; 5-Relief valve; 6-High pressure shut-off valve; 61-Pressure reducing valve; 62-Shuttle valve; 7-Replenishing pump; 8-First travel motor; 801-First main circuit; 802-First branch circuit; 9-Second travel motor; 901-Second main circuit; 902-Second branch circuit; 10-Solenoid directional valve; 11-Controller; 12-Pressure sensor. Detailed Implementation

[0036] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0037] The components of the embodiments of this application described and shown in the accompanying drawings can be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of this application provided in the drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application.

[0038] Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0039] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0040] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0041] With the standardization of infrastructure construction, agricultural development and other projects, the target market for construction machinery is becoming more and more segmented, the operating conditions are becoming more and more complex, the construction scope is becoming wider and wider, the implementation period is becoming shorter and shorter, and the working time of the whole machine is becoming longer and longer. How to reduce the failure rate of the whole machine and improve the uptime and work efficiency of the whole machine has become an important issue.

[0042] Traditional small hydrostatic travel motor drive systems are generally either series or parallel. In series drive systems, excessively high system pressure under high loads can easily damage hydraulic components and reduce the overall lifespan of the machine. Parallel drive systems require a larger main pump displacement to achieve the same maximum speed, resulting in higher system costs.

[0043] Specifically, such as Figure 2 As shown, a traditional series hydrostatic control system includes a main pump and two travel motors.

[0044] The main pump and the two travel motors are connected in series. The advantage of this series drive control mode is that the displacement of the main pump can be reduced, thereby reducing the overall cost of the machine. However, the disadvantages of this series drive control mode are also obvious. Under high load mode, the pressure at the main pump port is high, the system pressure is high, and the reliability of the main pump and the life of hydraulic system components will be greatly reduced under high pressure mode.

[0045] like Figure 3 As shown, a traditional parallel hydrostatic control system includes a main pump and two travel motors.

[0046] The main pump and two travel motors are connected in parallel. The advantage of this parallel drive control mode is that, under the same operating conditions, the parallel system has lower pressure, effectively extending the lifespan of hydraulic components. However, the disadvantages of this parallel drive control mode are also obvious: to achieve the same maximum speed, a larger main pump displacement is required, resulting in higher system costs.

[0047] In view of this, the first aspect of this application provides a hydraulic transmission system that, to a certain extent, solves the technical problems of traditional small hydrostatic series transmission systems where excessive system pressure under high load conditions can easily cause damage to the hydraulic components of the whole machine, and parallel transmission systems that require a large displacement of the main pump 1 and high system cost to achieve the same maximum speed.

[0048] The following will refer to Figure 1 This application describes a hydraulic transmission system according to some embodiments.

[0049] like Figure 1 As shown, the hydraulic transmission system of this application includes a main pump 1, a proportional directional valve 102, a first one-way replenishing valve 3, a second one-way replenishing valve 4, a relief valve 5, a high-pressure shut-off valve 6, a replenishing pump 7, a first drive mechanism, a second drive mechanism, a solenoid directional valve 10, a controller 11, and a pressure sensor 12.

[0050] like Figure 1 As shown, the main pump 1 drives the first drive mechanism and the second drive mechanism through oil passages, thereby driving the front and rear axles. The first drive mechanism (first travel motor 8) drives the front axle, and the second drive mechanism (second travel motor 9) drives the rear axle.

[0051] The controller 11 stores a first predetermined pressure value and a second predetermined pressure value in advance, wherein the first predetermined pressure value is greater than the second predetermined pressure value; the pressure sensor 12 can detect the system pressure and send the detected system pressure to the controller 11; when the system pressure is less than or equal to the first predetermined pressure, the controller 11 controls the first drive mechanism and the second drive mechanism to perform a series mode; when the system pressure is greater than the first predetermined pressure, the controller 11 controls the first drive mechanism and the second drive mechanism to perform a parallel mode; in the parallel mode, when the system pressure is less than or equal to the second predetermined pressure, the controller 11 controls the first drive mechanism and the second drive mechanism to perform a series mode.

[0052] In other words, in the hydraulic transmission system of this application, when the detected system pressure is less than or equal to a first predetermined pressure, the controller 11 controls the first drive mechanism and the second drive mechanism to execute a series mode. At this time, the hydraulic transmission system can achieve a higher speed of the whole machine through the small displacement main pump 1 (the advantage of this series mode is that the displacement of the main pump 1 can be reduced, thereby achieving the purpose of reducing the cost of the whole machine). This series mode ends when the system pressure is greater than the first predetermined pressure. That is, when the system pressure is greater than the first predetermined pressure, the controller 11 controls the first drive mechanism and the second drive mechanism to execute a parallel mode. In this parallel mode, the system pressure will inevitably decrease, which can avoid damage to the hydraulic components of the whole machine due to excessive system pressure and can effectively extend the service life of the hydraulic components. Until the system pressure is less than or equal to a second predetermined pressure, it switches to the series mode. At this time, the hydraulic transmission system can achieve a higher speed of the whole machine through the small displacement main pump 1.

[0053] In summary, the hydraulic transmission system of this application switches between series and parallel modes, which has the advantage of selecting a small displacement main pump 1 in the series mode, and can also prevent the problem of high pressure at the main pump 1 port and high system pressure in the series mode, which would cause damage to the hydraulic components of the whole machine.

[0054] In this embodiment, as Figure 1 As shown, the first drive mechanism and the second drive mechanism can be the travel motor of the excavator. The following description will take the travel motor as an example.

[0055] In this embodiment, as Figure 1 As shown, the main pump 1 includes two oil ports. When rotating forward, one oil port is the oil outlet and the other is the oil suction port; when rotating backward, the opposite occurs. Similarly, the first travel motor 8 and the second travel motor 9 each include two oil ports. When rotating forward, one oil port is the oil inlet and the other is the oil outlet.

[0056] In this embodiment, as Figure 1 As shown, the hydraulic transmission system also includes a first one-way replenishing valve 3 and a second one-way replenishing valve 4. Oil from the replenishing pump 7 replenishes the system via the first one-way replenishing valve 3 and the second one-way replenishing valve 4. When the system pressure is too high, the system discharges oil from the replenishing pump 7 through the high-pressure shut-off valve 6, thereby reducing the swashplate angle of the main pump 1 and decreasing the system flow rate.

[0057] Specifically, the hydraulic transmission system also includes a high-pressure shut-off valve 6 and an oil tank. The high-pressure shut-off valve 6 includes a pressure-reducing valve 61 and a shuttle valve 62. The two inlets of the shuttle valve 62 are connected to the outlet and suction port of the main pump 1, respectively (for example, taking the upper port of the main pump 1 as the outlet and the lower port as the suction port). The outlet of the shuttle valve 62 is connected to the first inlet of the pressure-reducing valve 61. The second inlet of the pressure-reducing valve 61 is connected to the outlet of the main pump 1, and the outlet of the pressure-reducing valve is connected to the oil tank. When the system pressure exceeds a third predetermined pressure (the third predetermined pressure is, for example, an instantaneous pressure, such as 32 MPa), the second inlet of the pressure-reducing valve 61 connects to the outlet of the pressure-reducing valve, thereby releasing some oil and serving as a safety measure.

[0058] In this embodiment, as Figure 1 As shown, pressure sensor 12 detects the pressure at the outlet of shuttle valve 62. Thus, regardless of whether the main pump 1 rotates forward or backward, pressure sensor 12 can detect the maximum system pressure; that is, one pressure sensor 12 can detect the maximum system pressure.

[0059] In this embodiment, as Figure 1 As shown, the hydraulic transmission system also includes a replenishing pump 7, a proportional directional valve 102, and a swashplate angle adjuster 101. The replenishing pump 7 can adjust the displacement of the main pump 1 via the proportional directional valve 102 and the swashplate angle adjuster 101 (thereby adjusting the corresponding flow rate of the main pump 1), thereby adjusting the vehicle speed; the controller 11 can output a corresponding current value to control the opening of the proportional directional valve 102 to adjust the displacement of the main pump 1 via the swashplate angle adjuster 101.

[0060] Furthermore, in the embodiments of this application, when the system pressure is greater than the first predetermined pressure, the controller 11 controls the first travel motor 8 and the second travel motor 9 to execute the parallel mode: if the system pressure is greater than the first predetermined pressure, and the displacement required by the main pump 1 at the current vehicle speed is less than or equal to the maximum displacement of the main pump 1, the controller 11 controls the first travel motor 8 and the second travel motor 9 to execute the parallel mode; when the system pressure is greater than the first predetermined pressure, and the displacement required by the main pump 1 at the current vehicle speed is greater than the maximum displacement of the main pump 1, the controller 11 controls the vehicle speed to be reduced to the maximum vehicle speed of the main pump 1 at the maximum displacement in the parallel mode.

[0061] Furthermore, it's worth mentioning that traditional parallel drive control, besides requiring a large main pump displacement and resulting in high system cost when the system reaches the same maximum speed, also suffers from the following drawbacks: 1. When the front and rear axles of the machine are tilted upwards during material handling, the rear axle motor has a low load. Due to the characteristics of the hydraulic system, system flow is lost through the rear axle motor, causing the entire machine to lose power. 2. When the machine experiences slippage, the parallel system will cause system flow to flow to the motor on the slipping side, resulting in reduced traction force.

[0062] In view of this, in order to solve the problems existing in the above-mentioned parallel drive control mode, this application makes the following design:

[0063] In the embodiments of this application, in parallel mode, when the system pressure is greater than the second predetermined pressure and V1≤λ*V, the controller 11 controls the first travel motor 8 and the second travel motor 9 to execute series mode; where λ is the safety factor for determining whether the vehicle is slipping, V is the theoretical vehicle speed, and V1 is the actual vehicle speed. In parallel mode, when the system pressure is greater than the second predetermined pressure and V1>λ*V, the first travel motor 8 and the second travel motor 9 continue to execute parallel mode.

[0064] In this embodiment, as Figure 1 As shown, in the series mode, the controller 11 controls the solenoid directional valve 10 to be in the right-hand conducting state, that is, the first main line 801 is connected to the oil inlet of the first travel motor 8, the oil outlet of the first travel motor 8 is connected to the oil inlet of the second travel motor 9, and the oil outlet of the second travel motor 9 is connected to the second main line 901.

[0065] See also Figure 1 In parallel mode, the controller 11 controls the solenoid directional valve 10 to be in the left-hand conducting state, that is, the first main line 801 is connected to the oil inlet of the first travel motor 8, the oil outlet of the first travel motor 8 is connected to the second branch line 902, the first branch line 802 is connected to the oil inlet of the second travel motor 9, and the oil outlet of the second travel motor 9 is connected to the second main line 901.

[0066] Furthermore, in the embodiments of this application, in order to ensure that the overall speed does not change abruptly when switching between series and parallel operation, the controller 11 controls the main pump 1 to output a corresponding flow rate according to the original actual vehicle speed V1: Q = X * V1 * I * V m / (η*10 3 ), where X is the number of travel motors, V1 is the original actual vehicle speed, I is the transmission ratio, and V m η represents the motor displacement, and η represents the overall motor efficiency. Controller 11 outputs a corresponding current value to control the opening of the proportional directional valve 102, control the swashplate angle adjuster 101, and control the main pump 1 to output a corresponding flow rate.

[0067] The actual vehicle speed V1 can be obtained through a speed sensor, the transmission ratio I is the transmission ratio of the entire system, and the motor displacement V... m As fixed parameters, the overall motor efficiency η is a fixed theoretical parameter. When the system switches to series connection, the number of motors X is two; when the system switches to parallel connection, the number of motors X is one.

[0068] Simultaneously, the controller 11 adjusts the displacement of the main pump 1 according to T = P * Q / (2π * n): where T is the torque of the main pump 1, Q is the flow rate of the main pump 1, P is the pressure of the main pump 1, and n is the speed of the main pump 1; the controller 11 compares the input torque of the main pump 1 with the output torque of the engine, such as the torque of the main pump 1 T ≥ T f T f To output torque to the engine, the controller 11 outputs a corresponding current value to control the opening of the proportional directional valve 102, and controls the swashplate angle adjuster 101 to reduce the displacement of the main pump 1, so that the displacement of the main pump 1 is at a reasonable value.

[0069] Based on the features described above, Figure 4 The control method of the hydraulic transmission system of this application is described using an example.

[0070] Control methods include:

[0071] S101, the whole machine detects the system pressure through pressure sensor 12 and feeds it back to controller 11.

[0072] S102, determine whether the system pressure P1 is ≤ X1, where X1 is the first predetermined pressure, for example, 32MPa.

[0073] S103, if P1≤X1, the first drive mechanism and the second drive mechanism execute the series mode (at this time, the electromagnetic reversing valve 10 is in the right-hand conducting state). This mode ends when P1>X1.

[0074] S104, if P1 > X1, the first drive mechanism and the second drive mechanism operate in parallel mode.

[0075] In parallel operation mode, the system needs to determine whether the pump displacement Vp1 required at the current vehicle speed is less than or equal to Vp. max Maximum displacement of main pump 1. If not, execute S105; if yes, execute S106.

[0076] S105, if the displacement required by the main pump 1 at the current vehicle speed is greater than the maximum displacement of the main pump 1, the vehicle speed is reduced to the maximum vehicle speed V2 of the main pump 1 at the maximum displacement in parallel mode.

[0077] S106: If the displacement required by the main pump 1 at the current vehicle speed is less than or equal to the maximum displacement of the main pump 1, the first drive mechanism and the second drive mechanism operate in parallel mode (at this time, the solenoid directional valve 10 is in the left-hand conducting state), and the vehicle speed is not changed. It should be noted that steps S105 and S106 are respectively determining whether Vp1 ≤ Vp in parallel mode. max There are two cases for the maximum displacement of main pump 1, so the order of steps S105 and S106 is not important.

[0078] S107: When the system is in parallel mode, the system pressure will inevitably decrease. At this time, determine whether the system pressure P1 is ≤ X2, where X2 is the second predetermined pressure, for example, 15MPa. If yes, execute S103 to switch to series mode; otherwise, execute S108.

[0079] S108, if the system pressure is greater than the second predetermined pressure, the system obtains the current pump displacement Vp1 through the current current value (the system can obtain the opening degree of the proportional reversing valve 102 through the current current value, and thus obtain the current pump displacement Vp1), and then derives the current theoretical vehicle speed V to determine whether V1 ≤ λ*V. If so, it is determined that the current vehicle speed is in a slipping state or the rear axle is in a lift-off state, and S103 is executed to switch to series mode. If not, S106 is executed to switch to parallel mode.

[0080] When V1≤λ*V, the first drive mechanism and the second drive mechanism operate in series; where λ is the safety factor for determining whether the vehicle is slipping, V is the theoretical vehicle speed, and V1 is the actual vehicle speed; when V1>λ*V, the first drive mechanism and the second drive mechanism operate in parallel.

[0081] Relevant calculation derivation formulas:

[0082] The required pump output flow rate Q can be calculated using the formula: Q = X * V1 * I * V m / (η*10 3 ), where X is the number of travel motors, V1 is the actual travel speed of the whole machine, I is the transmission ratio, and V m Let η be the motor displacement and η be the overall motor efficiency.

[0083] Vp1 = Q / n, where Q is the pump flow rate and n is the rotational speed of the main pump 1.

[0084] V2=n*Vp max *10 3 / (X*I*V m Vp max The maximum displacement of main pump 1, X is the number of travel motors, I is the transmission ratio, and V is the maximum displacement of main pump 1. m n represents the motor displacement, and n represents the main pump speed.

[0085] V = n * Vp1 * 10 3 / (X*I*V m V is the theoretical travel speed of the whole machine, Vp1 is the current pump displacement, X is the number of travel motors, I is the transmission ratio, and V m This refers to the motor displacement.

[0086] In summary, system pressure sensor 12 detects system pressure P1. If P1 ≤ X1, the system executes series mode. In this mode, the hydraulic system's advantage is that a higher overall speed can be achieved using the small-displacement main pump 1. This mode continues until system pressure P1 > X1.

[0087] If P1 is greater than X1, the system needs to determine whether the required pump displacement Vp1 at the current vehicle speed is ≤ Vp max If the maximum displacement of main pump 1 is within the specified range, parallel mode is executed. Otherwise, the overall speed is reduced to the maximum vehicle speed V2 of main pump 1's maximum displacement in parallel mode, and then parallel mode is executed again. In parallel mode, to address the issue of reduced traction caused by system flow diverting to the slipping motor when slippage occurs, the system calculates the current pump displacement Vp1 based on the current value, derives the theoretical vehicle speed V, and compares it with the actual speed V1. If V1 ≤ λ*V, the system switches to series mode to resolve the issue of reduced traction.

[0088] In summary, the hydraulic transmission system of this application switches between series and parallel modes, which not only has the advantage of a smaller displacement main pump 1 in the series mode, but also prevents the problem of high pressure at the main pump 1 port and high system pressure, which could damage the hydraulic components of the entire machine. Furthermore, it avoids the problems of no power and reduced traction force of the entire machine in the parallel mode.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A hydraulic transmission system, characterized in that, It includes a main pump (1), a first drive mechanism, a second drive mechanism, a pressure sensor (12), and a controller (11); The main pump (1) drives the first drive mechanism and the second drive mechanism through an oil passage; The controller (11) has a first predetermined pressure value and a second predetermined pressure value stored in advance, wherein the first predetermined pressure value is greater than the second predetermined pressure value; The pressure sensor (12) can detect the system pressure and send the detected system pressure to the controller (11); When the system pressure is less than or equal to the first predetermined pressure, the controller (11) controls the first drive mechanism and the second drive mechanism to perform a series mode; when the system pressure is greater than the first predetermined pressure, the controller (11) controls the first drive mechanism and the second drive mechanism to perform a parallel mode. In parallel mode, when the system pressure is less than or equal to the second predetermined pressure, the controller (11) controls the first drive mechanism and the second drive mechanism to perform series mode.

2. The hydraulic transmission system according to claim 1, characterized in that, When the system pressure is greater than the first predetermined pressure, and the displacement required by the main pump (1) at the current vehicle speed is less than or equal to the maximum displacement of the main pump (1), the controller (11) controls the first drive mechanism and the second drive mechanism to execute parallel mode; when the system pressure is greater than the first predetermined pressure, and the displacement required by the main pump (1) at the current vehicle speed is greater than the maximum displacement of the main pump (1), the controller (11) controls the vehicle speed to be reduced to the maximum vehicle speed of the main pump (1) in parallel mode.

3. The hydraulic transmission system according to claim 1, characterized in that, In parallel mode, when the system pressure is greater than the second predetermined pressure and V1≤λ*V, the controller (11) controls the first drive mechanism and the second drive mechanism to execute the series mode; where λ is the safety factor for judging whether the vehicle is slipping, V is the theoretical vehicle speed, and V1 is the actual vehicle speed. In parallel mode, when the system pressure is greater than the second predetermined pressure and V1 > λ*V, the first drive mechanism and the second drive mechanism continue to operate in parallel mode.

4. The hydraulic transmission system according to claim 1, characterized in that, The controller (11) controls the main pump (1) to output the corresponding flow rate according to the original actual vehicle speed: Q=X*V1*I*V m / (η*10 3 ), where X is the number of travel motors, V1 is the original actual vehicle speed, I is the transmission ratio, and V m η is the displacement of the travel motor, and η is the total efficiency of the travel motor. Both the first drive mechanism and the second drive mechanism are walking motors.

5. The hydraulic transmission system according to claim 1, characterized in that, The controller (11) adjusts the displacement of the main pump (1) according to T = P * Q / (2π * n): Where T is the main pump torque, Q is the main pump flow rate, P is the main pump pressure, and n is the main pump speed. The controller (11) compares the input torque of the main pump (1) with the output torque of the engine. If the torque of the main pump (1) is greater than or equal to the output torque of the engine, the controller (11) controls the displacement of the main pump (1) to decrease.

6. The hydraulic transmission system according to claim 1, characterized in that, The hydraulic transmission system also includes a replenishing pump (7), a proportional directional valve (102), and a swashplate angle adjuster (101); The replenishing pump (7) can adjust the displacement of the main pump (1) via the proportional directional valve (102) and the swashplate angle adjuster (101), thereby adjusting the vehicle speed; The controller (11) can output a corresponding current value to control the opening of the proportional directional valve (102) so as to adjust the displacement of the main pump (1) through the swashplate angle adjuster (101).

7. The hydraulic transmission system according to claim 1, characterized in that, The hydraulic transmission system also includes a high-pressure shut-off valve (6) and an oil tank; The high-pressure shut-off valve (6) includes a pressure reducing valve (61) and a shuttle valve (62); The two oil inlets of the shuttle valve (62) are connected to the first oil port and the second oil port of the main pump (1) respectively, and the oil outlet of the shuttle valve (62) is connected to the first oil inlet of the pressure reducing valve (61). The second oil inlet of the pressure reducing valve (61) is connected to the first oil port or the second oil port of the main pump (1), and the oil outlet of the pressure reducing valve (61) is connected to the oil tank. When the system pressure is greater than the third predetermined pressure, the second oil inlet of the pressure reducing valve (61) is connected to the oil outlet of the pressure reducing valve (61); The pressure sensor (12) detects the pressure at the outlet of the shuttle valve (62).

8. A control method for a hydraulic transmission system, characterized in that, The hydraulic transmission system includes a main pump (1), a first drive mechanism, and a second drive mechanism; The main pump (1) drives the first drive mechanism and the second drive mechanism through an oil passage; The control method includes: Determine whether the system pressure is less than or equal to the first predetermined pressure; If the system pressure is less than or equal to the first predetermined pressure, the first drive mechanism and the second drive mechanism shall operate in series. If the system pressure is greater than the first predetermined pressure, the first drive mechanism and the second drive mechanism will operate in parallel mode; In parallel operation mode, determine whether the system pressure is less than or equal to the second predetermined pressure; If the system pressure is less than or equal to the second predetermined pressure, the first drive mechanism and the second drive mechanism operate in series; wherein the first predetermined pressure value is greater than the second predetermined pressure value.

9. The control method for the hydraulic transmission system according to claim 8, characterized in that, The steps to determine whether the system pressure is less than or equal to the first predetermined pressure include: If the system pressure is greater than the first predetermined pressure, and the displacement required by the main pump (1) at the current vehicle speed is less than or equal to the maximum displacement of the main pump (1), the first drive mechanism and the second drive mechanism shall operate in parallel mode. If the system pressure is greater than the first predetermined pressure, and the displacement required by the main pump (1) at the current vehicle speed is greater than the maximum displacement of the main pump (1), the vehicle speed is reduced to the maximum vehicle speed of the main pump (1) in parallel mode.

10. The control method for the hydraulic transmission system according to claim 8, characterized in that, In parallel operation, the steps for determining whether the system pressure is less than or equal to the second predetermined pressure include: If the system pressure is greater than the second predetermined pressure and V1≤λ*V, the first drive mechanism and the second drive mechanism execute the series mode; where λ is the safety factor for determining whether the vehicle is slipping, V is the theoretical vehicle speed, and V1 is the actual vehicle speed. If the system pressure is greater than the second predetermined pressure and V1 > λ*V, the first drive mechanism and the second drive mechanism will operate in parallel.

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