Excavator cold start and temperature regulation control method and system

Abstract

A method and system for cold start and temperature regulation control of an excavator belongs to the technical field of excavators. The method for cold start and temperature regulation control of an excavator includes: when the warm-up conditions are met during the warm-up phase, the hot start valve is controlled to be disconnected, and the pump current is increased for pressurization processing; the hot start valve is set as a bucket confluence valve; it is determined whether the control stop condition is met, and if so, the current pump current is maintained for warm-up; otherwise, the engine speed is adjusted to the target speed point; and the pump current is adjusted according to the actual torque error. The present invention uses the bucket confluence valve as a hot start valve to reduce the use of parts and reduce costs; the engine set speed is adjusted during the warm-up process so that it tends to have a lower fuel consumption rate under the current working conditions, thereby improving economy.

Description

Technical Field

[0001] The present invention relates to the technical field of excavators, and in particular to a method and system for cold start-up and temperature regulation control of an excavator. Background Art

[0002] Excessively low or high hydraulic oil temperatures in excavators can damage the engine and hydraulic system to a certain extent, shortening their service life. When the ambient temperature is low, the excavator needs to be warmed up before formal operation. This is usually done by holding the pressure to raise the engine coolant and hydraulic system oil temperatures to the required operating temperature.

[0003] For example, CN113357231B discloses an automatic rapid warm-up system and method for a hydraulic excavator. The system includes: detecting the hydraulic oil temperature; when the hydraulic oil temperature is below a certain threshold, adjusting the throttle knob to increase the throttle, controlling the proportional solenoid valve to reduce the hydraulic pump's displacement, and preventing the hydraulic pump from excessively displacing at low temperatures; when the temperature is within a preset temperature range, the throttle knob simultaneously inputs a signal to increase the entire machine's throttle, controlling the proportional solenoid valve to maintain the hydraulic pump's displacement at a fixed level. The hydraulic pump's flow rate increases as the entire machine's throttle signal increases, further increasing the heat generated by overflow and accelerating the warm-up speed. This solution increases the hydraulic oil circuit pressure and the after-treatment exhaust temperature by controlling the flow rate of the warm-up start valve and pump, thereby warming up the engine through the heat generated by overflow. However, this solution fails to consider the economic factors brought about by fuel consumption during the warm-up process.

[0004] For example, CN118498468A discloses a control method, device, storage medium, and excavator system for an excavator system. This method uses the current return temperature as a judgment reference. When the current return temperature is less than or equal to a preset temperature threshold, it obtains the absolute value of the temperature difference, that is, the absolute value of the difference between the current return temperature and the preset temperature threshold. Finally, it determines a first target opening as the opening corresponding to the absolute value of the temperature difference, adjusts the opening of the first return oil throttle valve to the first target opening, and closes the second return oil throttle valve. Compared with existing solutions, this method can control the return oil from passing through the cooler, thereby increasing the heating speed. This solves the problem that the two parallel one-way valves in the prior art excavator cannot directly control the return oil from passing through the cooler when the hydraulic oil temperature is low and rapid heating is required. Although the return oil is controlled to not pass through the cooler, this solution does not take into account economic factors. That is, the warm-up process does not consider reducing fuel consumption by adjusting the engine speed.

[0005] For example, CN117514979A discloses a thermal management method, controller, and thermal management system for an electric excavator. The method includes: obtaining the hydraulic oil temperature of the hydraulic oil in the hydraulic oil tank; when the hydraulic oil temperature is lower than a first preset oil temperature, adjusting the flow rate of the coolant in the first branch and the flow rate of the coolant in the second branch by controlling the opening of the reversing valve, so as to heat the hydraulic oil in the hydraulic oil tank with the coolant flowing in the first branch. The present application can adjust the flow rate of the coolant passing through the hydraulic oil tank according to the hydraulic oil temperature through an electronically controlled proportional reversing valve, heat the hydraulic oil with the heat of the coolant, increase the heating rate of the hydraulic oil in low-temperature environments, reduce the waiting time for warm-up, enable the machine to quickly reach normal working conditions, and at the same time reduce the workload of the electronic fan and reduce energy consumption. This solution controls the opening of the reversing valve according to the oil temperature to warm up the engine, and also does not consider the economic impact of the engine speed on the fuel consumption rate.

[0006] Current technologies often require the operator to operate the action handle to bring the working device to its limit position, increasing the heat generated by the overflow valve to achieve a warm-up effect. This requires the operator to operate the handle for extended periods of time, which can also cause fatigue. Furthermore, warming up the engine at a fixed set speed fails to consider energy consumption.

[0007] Therefore, there is an urgent need to develop a new excavator cold start and temperature regulation control method to solve the current defects and shortcomings. Summary of the Invention

[0008] In view of this, the main purpose of the present invention is to provide a cold start and temperature adjustment control method for an excavator, in order to at least partially solve the above technical problems.

[0009] To achieve the above objectives, as a first aspect of the present invention, a method for cold start-up and temperature regulation control of an excavator is proposed, comprising the following steps:

[0010] During the warm-up phase, when the warm-up conditions are met, the hot-up start valve is controlled to be disconnected, and the pump current is increased to perform pressurization processing; the hot-up start valve is configured as a bucket merging valve;

[0011] Determine whether the control stop condition is met. If so, maintain the current pump current to warm up the engine; otherwise, adjust the engine speed to the target speed point and adjust the pump current according to the actual torque error.

[0012] As a second aspect of the present invention, a cold start and temperature adjustment control system for an excavator is proposed, comprising: a pump, a main valve, a hot start valve and a control unit, wherein the hot start valve is configured as a bucket merging valve; wherein the output end of the pump is connected to the main valve, and the main valve is connected to an oil tank through the hot start valve, and the oil tank is connected to the main valve through an overflow valve, and the input end of the pump is connected to the oil tank through the engine, and the control unit is electrically connected to an oil temperature sensor, and the oil temperature sensor is used to collect the temperature of the hydraulic oil, and the control unit is used to compare the hydraulic oil temperature with the operating temperature range and control the action of the main valve and the hot start valve.

[0013] Based on the above technical solutions, the excavator cold start and temperature adjustment control method and system of the present invention have at least one of the following beneficial effects compared to the prior art:

[0014] 1. During the warm-up process, the point close to the optimal fuel economy curve is determined based on the torque range and speed range corresponding to the current temperature, and the engine set speed is adjusted to achieve a lower fuel consumption rate under the current operating conditions, thereby improving economy;

[0015] 2. The bucket confluence valve is used as the hot start valve, eliminating the need to add additional components and reducing costs;

[0016] 3. The oil circuit is cooled and controlled by a fan, which is more controllable than traditional coolant cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments.

[0018] Figure 1 It is a flow chart of the excavator cold machine start-up and temperature adjustment control method of the present invention;

[0019] Figure 2 This is a structural framework diagram of the excavator cold start and temperature adjustment control system of the present invention;

[0020] Figure 3 It is a schematic diagram of the universal characteristic curve of the excavator cold machine starting and temperature adjustment control method of the present invention.

[0021] In the above drawings, the meanings of the reference numerals are as follows:

[0022] 1. Pump; 2. Main valve; 3. Hot start valve; 4. Fuel tank; 5. Overflow valve; 6. Fuel cylinder. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0024] The terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the embodiments of the present invention. The singular forms "a", "an", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0025] This application found that most existing technologies require the operator to operate the action handle to make the working device reach the working limit, increase the overflow heat generated by the overflow valve to achieve the warm-up effect, which requires the driver's working time to operate. Long-term operation of the handle will also make the driver tired. At the same time, warming up at a fixed set speed does not take into account energy consumption. After in-depth research, it was found that by detecting the hydraulic oil temperature to achieve warm-up control, normal operation and cooling control mode switching, the excavator's operating temperature can be automatically adjusted. At the same time, the engine economy is taken into account, so that it is as close to the optimal economic range as possible within a reasonable speed range.

[0026] The bucket merging valve is set in the structure of the normal working stage of the excavator. Its function is to merge the oil from different oil pumps 1 and supply it to the bucket cylinder 6 according to work requirements, so as to increase the movement speed and force of the bucket. For example, when performing operations such as excavation and loading and unloading, which require oil with a large flow and pressure to drive the bucket, the bucket merging valve will work to connect the oil circuit to realize the merging function, and therefore will not participate in the oil circuit in and out during the warm-up phase. The cylinder here does not simply refer to the bucket cylinder, but can be the cylinder of any actuator; when the bucket is moving, the bucket merging valve is responsible for merging the oil flow to the bucket. When the bucket is not moving, the bucket merging valve does not play a merging role to ensure that the working oil circuit supplies oil to the actuator.

[0027] Therefore, the inventors propose a method for cold start and temperature regulation control of an excavator, comprising the following steps:

[0028] like Figure 1 As shown, during the warm-up phase, when the warm-up conditions are met, the hot-up start valve 3 is controlled to be disconnected, and the current of the pump 1 is increased for pressurization. The hot-up start valve 3 is configured as a bucket merging valve. In the overall machine structure, the bucket merging valve is used as the hot-up start valve 3, which expands the function of the bucket merging valve and eliminates the need to add other valves to hold pressure and cut off the oil circuit.

[0029] Determine whether the control stop condition is met. If so, maintain the current pump 1 current to warm up the engine; otherwise, adjust the engine speed to the target speed point and adjust the pump 1 current according to the actual torque error.

[0030] When the hot engine condition is met, the bucket merging valve is energized to close and close. The closing and closing here refer to the valve core being in the disconnected position, that is, the valve core of the bucket merging valve is in the open position. Figure 2 In the right position, the main valve 2 is in the middle position, and the oil path flowing back to the oil tank through the bucket merging valve is cut off.

[0031] Set the working temperature range, detect the temperature of the hydraulic oil under the current working conditions, and compare the temperature of the hydraulic oil with the working temperature range. When the temperature of the hydraulic oil is lower than the working temperature range, it is the warm-up stage; when the temperature of the hydraulic oil is within the working temperature range, it is the normal working stage; when the temperature of the hydraulic oil is higher than the working temperature range, it is the cooling stage.

[0032] The current operating condition corresponds to a target torque range, a target speed range, and a preset torque error. The actual torque error is calculated by subtracting the current torque value from the maximum value of the target torque range. When the actual torque error is less than the preset torque error, the current pump 1 current is maintained. The target torque range and target speed range are determined based on speed and torque limits and calibration to prevent engine de-energization or other malfunctions.

[0033] The warm-up condition is that the safety lock switch is on and the excavator is not moving. The safety lock switch is located in the cab and can be controlled by the driver.

[0034] Control stops when Pump 1's displacement exceeds the preset maximum or when the engine load exceeds the preset maximum. While increasing the current, the system monitors whether Pump 1's displacement has reached the preset maximum. If so, the current is no longer increased. If the engine load exceeds the preset maximum, the current is no longer increased, maintaining the current load for a cycle warm-up.

[0035] When the excavator is in normal working condition, that is, when the hydraulic oil temperature reaches the operating temperature range, the control unit sends a command to the display to prompt the driver that the warm-up is complete and normal operation can be carried out. At the same time, the warm-up start valve 3 is opened to allow the hydraulic oil to flow to the working oil circuit, realizing the normal operation of the excavator. The main valve 2 plays the role of distributing the flow direction of the hydraulic oil. It receives high-pressure hydraulic oil from the pump 1 and distributes the hydraulic oil to the various actuators of the excavator, such as the boom cylinder 6, the bucket cylinder 6, and the bucket cylinder 6, according to different operating instructions, to achieve corresponding actions, such as controlling the lifting and lowering of the boom, the extension and retraction of the bucket, and the digging and unloading of the bucket.

[0036] When the excavator is in a cooling state, that is, when it is detected that the hydraulic oil temperature exceeds the operating temperature range, the cooling fan is turned on for cooling control. The fan set current is obtained according to the correspondence between the hydraulic oil temperature and the fan speed, and the fan speed is controlled to reduce the temperature of the hydraulic oil. When the hydraulic oil temperature is lower than the maximum value of the ideal operating temperature, the fan maintains a lower speed to achieve the purpose of rapid response when the fan is turned on.

[0037] Among them, since the relief valve 5 is in a closed state, the hydraulic oil that initially reaches the inlet of the relief valve 5 no longer flows, then the hydraulic pump continues to work, which will cause the system pressure to continue to rise. The pressure gradually increases, which will generate some heat and form pressure buildup. Pressure buildup will cause the system pressure to rise abnormally, which may cause damage to the hydraulic components, such as seal rupture, pipeline burst, etc. In order to prevent pressure buildup, the hydraulic system presets an overflow pressure. When the pressure of the hydraulic oil is greater than the overflow pressure, the relief valve 5 opens, and the hydraulic oil returns to the oil tank 4 through the relief valve 5 to avoid the current oil circuit pressure at the inlet of the relief valve 5 being too high, allowing the hydraulic oil to flow, thereby releasing excess pressure, and also playing a role in pressure relief protection. The pump 1 continues to pump oil from the oil tank 4 through the engine, and the temperature of the hydraulic oil in the oil circuit continues to rise, and the oil circuit circulates to achieve the warm-up process.

[0038] The target torque range and target speed range for the current operating condition are obtained through table lookup. Specifically, the corresponding row and column in the table are found based on the current hydraulic oil pressure and engine speed values, thereby determining the target torque range and target speed range for the current operating condition. If the data points in the table are discrete and the actual measured value falls between two data points, an interpolation algorithm is used to calculate a more accurate target value.

[0039] The target torque range and the target speed range are combined with the universal characteristic curve to obtain the target speed point. The process of determining the target speed point takes into account minimizing fuel consumption, that is, achieving the lowest fuel consumption possible during the warm-up phase. Therefore, the speed point corresponding to the part of the equal fuel consumption line with the lowest value in the area is found, that is, along the optimal economy curve, the speed value corresponding to the equal fuel consumption line that falls within the target area and has the relatively lowest fuel consumption is found as the target speed point. This can enable the engine to consume relatively less fuel when warming up.

[0040] In a preferred embodiment, Figure 2As shown, the present invention also discloses an excavator cold engine start and temperature adjustment control system, including a pump 1, a main valve 2, a hot engine start valve 3 and a control unit. The output end of the pump 1 is connected to the main valve 2, and the main valve 2 is connected to the oil tank 4 through the hot engine start valve 3. The oil tank 4 is connected to the main valve 2 through the overflow valve 5. The input end of the pump 1 is connected to the oil tank 4 through the engine. The control unit is electrically connected to an oil temperature sensor. The oil temperature sensor is used to collect the temperature of the hydraulic oil. The control unit is used to compare the hydraulic oil temperature with the working temperature range and control the action of the main valve 2 and the hot engine start valve 3. The oil temperature sensor is installed in the hydraulic system to accurately collect the temperature of the hydraulic oil and provide a basis for the control unit to judge the temperature state of the hydraulic oil so as to take the corresponding temperature adjustment process later.

[0041] During the warm-up phase, the driver first sends a warm-up control instruction to the controller through the display. When the control unit receives the warm-up instruction, it detects the temperature of the hydraulic oil, which is collected by the oil temperature sensor. Assuming that the ideal operating temperature range of the excavator is T1-T2, when the hydraulic oil temperature collected by the oil temperature sensor is lower than T1, and the safety lock switch is turned on, and the excavator does not move, the warm-up action begins. When the warm-up conditions are met, the hot start valve 3 is controlled to receive the maximum current, so that the valve core of the hot start valve 3 is in the disconnected state, preventing the oil from flowing back to the oil tank 4 through the hot start valve 3. At the same time, the current of the pump 1 is gradually increased, so that the displacement of the pump 1 gradually increases, thereby increasing the pressure in the oil circuit. When the pressure in the oil circuit reaches the preset overflow pressure point, the oil overflows through the overflow valve 5, and the overflow resistance generates heat, which accelerates the temperature rise of the oil. The schematic diagram is shown as follows. Figure 2 The displacement of pump 1 corresponds to the opening of pump 1, and the current flow rate is calculated based on the current speed and current displacement value.

[0042] During the pressurization process, a table is consulted based on the current oil temperature to determine the target torque range and target speed range that the engine can withstand at the current temperature. Based on the engine fuel economy curve, the corresponding target speed point on the economy curve that can achieve maximum power within this target torque range and target speed range is found. This speed point is sent to the engine as the set speed for speed control. Simultaneously, the current of Pump 1 is controlled based on the actual current torque value and the maximum ideal torque value, so that the current torque value at the engine end reaches the torque at the current operating point. The difference between the maximum ideal torque value and the current torque is calculated, and this difference is used to close the loop control of the current value of Pump 1. This difference is recorded as the actual torque error, and the deviation threshold of this difference is recorded as the preset torque error. When the actual torque error is less than the preset torque error, the current control of Pump 1 is stopped, and the current value of Pump 1 is maintained.

[0043] The present invention will be further described below through specific examples. It should be noted that the following examples are merely illustrative and are not intended to limit the present invention. Based on the embodiments of the present invention shown below, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the embodiments of the present invention.

[0044] Example 1

[0045] The working temperature range is T1-T2. The temperature of the hydraulic oil is detected by the oil temperature sensor and compared with the working temperature range T1-T2. When the temperature of the hydraulic oil is lower than T1, the engine is warmed up. During the warm-up process, the temperature is further divided into temperature segments [T 01 , T 02 , T1], when the temperature of the hydraulic oil is less than T 01 At this time, by looking up the table, the maximum speed and torque range of the engine at the current temperature are [n 01 , n 01max ],[t 01 , t 01max ], in this case, calculate the speed n1 and torque t1 corresponding to the optimal operating point of the engine, set the set speed to n1, and increase the pump current at the same time to make the torque tend to the set torque t1. When the temperature reaches T 02 When the maximum speed and torque range of the engine at the current temperature are obtained by re-looking up the table, they are [n 02 , n 02max ][t 02 , t 02max ] Repeat the above steps. When the temperature reaches T1, stop warming up and resume normal operation. Subtract the current torque value of the current operating condition from the maximum value of the target torque range to obtain the difference. The torque error is set to 5%. When the difference is less than the torque error of 5%, maintain the current pump current.

[0046] like Figure 3 As shown in the figure, the line connecting the points of intersection of the constant power curve and the constant fuel consumption curve represents the optimal fuel economy curve. Within the maximum speed and torque range, the point on the optimal fuel economy curve closest to the small circle on the constant fuel consumption curve is the target speed. This target speed corresponds to a target torque and speed. The dashed line at the point of intersection represents the fuel economy curve. The speed point is found so that it falls on the dashed line. The speed is fixed at a constant value, and the torque is found so that its intersection with the speed falls on the dashed line. This indicates the current maximum power.

[0047] In the excavator's control system, a table correlating hydraulic oil temperature with fan speed was established through pre-established data collection. For example, when the hydraulic oil temperature is 50°C, the corresponding fan speed is set to 1000 rpm; when the hydraulic oil temperature is 60°C, the corresponding fan speed is set to 1500 rpm, and so on. This table covers different hydraulic oil temperature ranges and the corresponding fan speed values, providing basic data for subsequent interpolation calculations. A temperature sensor capable of accurately measuring the hydraulic oil temperature is installed in the hydraulic system. It constantly monitors the actual hydraulic oil temperature and transmits the temperature signal in real time to the excavator's control system. A controller is also installed to control the fan motor current. The fan speed is adjusted by varying the current. Lower current results in higher fan speed and improved heat dissipation. An inversely proportional solenoid valve is used to maintain a low fan speed, ensuring a fast response during operation.

[0048] When the excavator is cooling down (e.g., due to elevated hydraulic oil temperatures after prolonged, intensive operation or due to elevated ambient temperatures), the hydraulic oil temperature sensor continuously collects the actual hydraulic oil temperature and transmits this value to the control system. Upon receiving the current hydraulic oil temperature, the control system compares it with the preset optimal hydraulic oil operating temperature range. If the current temperature exceeds the upper limit of the operating temperature range, the control system determines that the fan should be activated for cooling and begins calculating the fan current setting based on this correspondence.

[0049] The process of using the linear interpolation formula to calculate the corresponding fan setting current is as follows: Assuming T a 、T b Indicates the two end temperature of the temperature range (in this embodiment, T a =50℃, T b =60℃), N a 、N b Indicates the corresponding fan speed range endpoint value (N a =1000 rpm, N b =1500 rpm), T represents the actual hydraulic oil temperature (55°C), N 风扇 Indicates the fan speed to be calculated. The calculation formula is as follows:

[0050]

[0051] Substituting the values ​​into the =1250 rpm. Based on the corresponding relationship between fan speed and current, the set current value required to achieve the fan speed of 1250 rpm is calculated. A table lookup shows that the corresponding current is 2.5 A. The control system sends the calculated fan set current value of 2.5 A to the fan motor's current controller. Based on the received command, the current controller adjusts the current output to the fan motor, causing the fan motor to operate at the set current, thereby allowing the fan to reach the calculated speed of 1250 rpm.

[0052] The present invention gradually increases the displacement of pump 1 by controlling the current of hot start valve 3 and pump 1, automatically increasing oil circuit pressure and raising the post-processing exhaust temperature. This eliminates the need for driver operation and reduces driver fatigue. Furthermore, the bucket confluence valve serves as hot start valve 3, reducing component usage and lowering costs. During the hot start process, the present invention controls the set engine speed, resulting in a lower fuel consumption rate under current operating conditions, thereby improving fuel economy.

[0053] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In the present invention, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in the present invention and features of different embodiments or examples without contradiction.

[0054] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0055] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may be performed out of the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention pertain.

[0056] In the several embodiments provided by the present invention, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces, indirect coupling or communication connection of devices or units, which may be electrical, mechanical or other forms.

[0057] In addition, the functional units in various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or hardware plus software functional units.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for cold start and temperature regulation control of an excavator, characterized in that: The steps include: During the warm-up phase, when the warm-up conditions are met, the warm-up start valve is controlled to be disconnected, and the pump current is increased to perform pressurization processing; the warm-up start valve is configured as a bucket merging valve; the passage back to the fuel tank through the bucket merging valve is cut off; The hot car condition is that the safety lock switch is on and the excavator is not moving; Determine whether the control stop condition is met, if so, keep the current pump current to warm up the car; Otherwise, the engine speed is adjusted to the target speed point, and the pump current is adjusted according to the actual torque error. The control stop condition is that the pump displacement exceeds the preset maximum displacement or the engine load exceeds the preset maximum load.

2. The excavator cold start and temperature adjustment control method according to claim 1, characterized in that: Set an operating temperature range, detect the temperature of the hydraulic oil in the current working condition, and compare the temperature of the hydraulic oil with the operating temperature range. When the temperature of the hydraulic oil is lower than the operating temperature range, it is the warm-up stage; when the temperature of the hydraulic oil is within the operating temperature range, it is the normal working stage; when the temperature of the hydraulic oil is higher than the operating temperature range, it is the cooling stage.

3. The excavator cold start and temperature adjustment control method according to claim 2, characterized in that: The current operating condition corresponds to a target torque range, a target speed range, and a preset torque error. The actual torque error is obtained by subtracting the current torque value of the current operating condition from the maximum value of the target torque range. When the actual torque error is less than the preset torque error, the current pump current is maintained.

4. The excavator cold start and temperature adjustment control method according to claim 2, characterized in that: When the excavator is in the normal working stage, the hot start valve is controlled to be connected, and the hydraulic oil flows to the working oil circuit.

5. The excavator cold start and temperature adjustment control method according to claim 2, characterized in that: When the excavator is in the cooling stage, the fan setting current is obtained according to the corresponding relationship between the temperature of the hydraulic oil and the fan speed, and the fan speed is controlled to reduce the temperature of the hydraulic oil.

6. The excavator cold start and temperature adjustment control method according to claim 3, characterized in that: The target torque range and the target speed range of the current working condition are both obtained by looking up a table, and the target torque range and the target speed range are combined with a universal characteristic curve to obtain the target speed point.

7. The excavator cold start and temperature adjustment control method according to claim 1, characterized in that: An overflow pressure is preset, and when the pressure of the hydraulic oil is greater than the overflow pressure, the overflow valve is opened.

8. An excavator cold start and temperature adjustment control system, characterized in that: It includes a pump, a main valve, a hot car starting valve and a control unit; the hot car starting valve is set as a bucket merging valve; wherein the output end of the pump is connected to the main valve, the main valve is connected to the oil tank through the hot car starting valve, the oil tank is connected to the main valve through a relief valve, the input end of the pump is connected to the oil tank through the engine, the control unit is electrically connected to an oil temperature sensor, the oil temperature sensor is used to collect the temperature of the hydraulic oil, the control unit adopts the excavator cold machine starting and temperature adjustment control method as described in any one of claims 1 to 7, for comparing the hydraulic oil temperature with the working temperature range and controlling the action of the main valve and the hot car starting valve.

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