Pressure-compensated hydraulic pump, speed control system and control method, and engineering machinery

Abstract

The present invention relates to engineering machinery, and specifically discloses a pressure compensation control type hydraulic pump, including an electric proportional pressure compensator, a hydraulic pump, a hydraulically controlled reversing valve and a servo piston, wherein the electric proportional pressure compensator can be electrically connected to a controller, the first hydraulically controlled port of the hydraulically controlled reversing valve is connected to an internal oil leakage circuit through the electric proportional pressure compensator, and the first hydraulically controlled port is connected to an internal output oil circuit through a hydraulically controlled oil inlet circuit provided with a first throttle valve, the second hydraulically controlled port of the hydraulically controlled reversing valve is connected to the internal output oil circuit, and the pressure difference between the opening pressure of the electric proportional pressure compensator and the oil outlet pressure of the hydraulic pump can drive the hydraulically controlled reversing valve to reverse, thereby selectively connecting the rodless chamber of the servo piston to the internal output oil circuit or the internal oil leakage circuit. In addition, the present invention also discloses a speed control method, a speed control system and engineering machinery. The hydraulic pump of the present invention can stabilize the output flow of the hydraulic pump at a required value.

Description

Technical Field

[0001] The present invention relates to engineering machinery, and in particular to a speed control method for a heat dissipation device of an engineering machinery. In addition, the present invention also relates to a pressure compensation control type hydraulic pump, a speed control system for a heat dissipation device of an engineering machinery, and an engineering machinery. Background Art

[0002] During the operation of large-scale construction machinery, part of the pressure energy of its hydraulic system will be converted into heat energy, causing the oil temperature of the hydraulic system to rise. In order to maintain the temperature of the hydraulic oil within a reasonable range, it is necessary to use heat dissipation equipment to dissipate the heat of the hydraulic oil. Large-scale construction machinery such as excavators and loaders generally use an independent heat dissipation control system, that is, the input shaft of the cooling fan is not connected to the output shaft of the engine, but a hydraulic motor is used to drive the cooling fan to rotate.

[0003] Figure 1 The heat dissipation control system of an excavator in the prior art is shown, in which a cooling pump 1 is connected to the output shaft of an engine 2, and the hydraulic oil output by the cooling pump 1 enters a fan motor 3 to drive the fan motor 3 to rotate, and then drives the fan 4 to rotate through the fan motor 3. The temperature sensor 5 detects the temperature of the hydraulic oil and feeds it back to the controller 6, which determines the required speed of the fan 4 after performing corresponding calculations and outputs a certain current to the electric proportional relief valve 7, and controls the oil inlet pressure of the fan motor 3 by adjusting the pressure of the electric proportional relief valve 7, thereby controlling the speed of the fan.

[0004] However, during the operation of the construction machinery, the speed of the engine 2 will change with the load. The change in the speed of the engine 2 will cause the speed of the cooling pump 1 to change, so that the output flow of the cooling pump 1 will also change. The fluctuation in the output flow of the cooling pump 1 will cause the speed of the fan motor 3 to fluctuate, and thus cause the speed of the fan 4 to fluctuate, making it impossible to stabilize the speed of the fan 4 at the required value. This affects the heat dissipation effect of the hydraulic system on the one hand, and causes the fan 4 to generate greater noise on the other hand.

[0005] In view of this, it is necessary to design a pressure-compensated controlled hydraulic pump. Summary of the invention

[0006] The technical problem to be solved by the first aspect of the present invention is to provide a speed control method for a heat dissipation device of engineering machinery, which control method can stabilize the output flow of the hydraulic pump at the required value, thereby stabilizing the speed of the heat dissipation device within the speed setting range.

[0007] The technical problem to be solved by the second aspect of the present invention is to provide a pressure-compensated controlled hydraulic pump, which can stabilize the output flow of the hydraulic pump at a required value.

[0008] The technical problem to be solved by the third aspect of the present invention is to provide a speed control system for a heat dissipation device of an engineering machinery, wherein the speed control system can stabilize the speed of a cooling fan at a required value.

[0009] The technical problem to be solved by the fourth aspect of the present invention is to provide an engineering machine whose hydraulic system has good heat dissipation effect and whose heat dissipation device has low noise.

[0010] In order to solve the above technical problems, the first aspect of the present invention provides a speed control method for a heat dissipation device of engineering machinery, comprising the following steps: first, obtaining the hydraulic oil temperature in the hydraulic system in which the heat dissipation device is located, and obtaining a corresponding first pressure value according to the hydraulic oil temperature, and generating a corresponding second pressure value according to the load pressure generated by the heat dissipation device; second, comparing the first pressure value and the second pressure value; third, adjusting the displacement of the hydraulic pump used to drive the heat dissipation device in the hydraulic system according to the comparison result, so that when the speed of the hydraulic pump changes, the flow rate of the hydraulic pump is stabilized within the flow setting range, thereby stabilizing the speed of the heat dissipation device within the speed setting range.

[0011] Preferably, the first step includes: obtaining a corresponding current value according to the temperature of the hydraulic oil, and obtaining a corresponding first pressure value according to the current value.

[0012] Preferably, the second step includes: inputting the first pressure value and the second pressure value into a pressure comparison module respectively, so as to compare the first pressure value and the second pressure value.

[0013] Specifically, the third step includes: when the speed of the hydraulic pump decreases, the first pressure value is greater than the second pressure value, and the displacement of the hydraulic pump is controlled to increase; when the speed of the hydraulic pump increases, the first pressure value is less than the second pressure value, and the displacement of the hydraulic pump is controlled to decrease.

[0014] A second aspect of the present invention provides a pressure-compensated controlled hydraulic pump, comprising a pressure control device, a hydraulic pump body and a displacement regulating device, wherein the displacement regulating device is suitable for comparing a first pressure value formed by the pressure control device and a second pressure value at the oil outlet of the hydraulic pump, and regulating the displacement of the hydraulic pump according to the comparison result, so that when the rotational speed of the hydraulic pump body changes, the flow rate of the hydraulic pump body is stabilized within a set range.

[0015] Preferably, the pressure control device is an electric proportional pressure compensator.

[0016] Preferably, the displacement regulating device comprises a hydraulically controlled reversing valve and a servo piston for regulating the displacement of the hydraulic pump body, the oil outlet of the hydraulic pump is connected to an internal output oil circuit, the oil inlet of the hydraulic pump is connected to an internal input oil circuit, the first hydraulically controlled port of the hydraulically controlled reversing valve is connected to the internal oil leakage circuit through the pressure control device, the rodless chamber of the servo piston is respectively connected to the internal output oil circuit and the internal oil leakage circuit via the hydraulically controlled reversing valve, the pressure difference between the oil outlet pressure of the pressure control device and the hydraulic pump acts on the valve core of the hydraulically controlled reversing valve through the first hydraulically controlled port and the second hydraulically controlled port of the hydraulically controlled reversing valve, thereby driving the hydraulically controlled reversing valve to reverse, thereby selectively connecting the rodless chamber of the servo piston to the internal output oil circuit or the internal oil leakage circuit.

[0017] Specifically, the first hydraulically controlled port is connected to the internal output oil circuit via a hydraulically controlled oil inlet circuit provided with a first throttle valve, and the second hydraulically controlled port of the hydraulically controlled reversing valve is connected to the internal output oil circuit.

[0018] Specifically, the hydraulic pump body is a variable displacement piston pump.

[0019] Specifically, the hydraulically controlled reversing valve is a two-position three-way reversing valve.

[0020] Preferably, a second throttle valve is provided on the connecting oil circuit between the rodless chamber of the servo piston and the hydraulically controlled reversing valve.

[0021] Specifically, a safety oil circuit is connected between the rodless chamber of the servo piston and the internal oil leakage circuit, and a third throttle valve is provided on the safety oil circuit. One end of the safety oil circuit is connected to the connecting oil circuit between the rodless chamber of the servo piston and the hydraulically controlled reversing valve, and the connection point is located between the first throttle valve and the second throttle valve; and the connection position of the other end of the safety oil circuit on the internal oil leakage circuit is located behind the connection position of the oil outlet of the electric proportional pressure compensator.

[0022] The third aspect of the present invention provides a speed control system for a heat dissipation device of engineering machinery, comprising a temperature sensor for detecting the temperature of hydraulic oil, a fan motor for driving a fan to rotate, a controller and a pressure-compensated controlled hydraulic pump as described in any one of the technical solutions of the second aspect, wherein the temperature sensor is electrically connected to the controller, and the controller is capable of receiving and controlling a first pressure value formed by the pressure control device according to a signal from the temperature sensor, and the pressure generated by the fan motor driving the fan is fed back to the oil outlet of the hydraulic pump to form a second pressure value.

[0023] The fourth aspect of the present invention provides an engineering machinery, including a radiator for cooling hydraulic oil and a speed control system for the heat dissipation device of the engineering machinery as described in the technical solution of the third aspect, wherein the fan motor can drive the fan to rotate to cool the radiator.

[0024] In the basic embodiment of the pressure-compensated controlled hydraulic pump of the present invention, when the speed of the power drive device that provides mechanical energy to the hydraulic pump changes, the displacement regulating device can adjust the displacement of the hydraulic pump so that the output flow of the hydraulic pump is stabilized at the required value, thereby stabilizing the speed of the actuator driven by the hydraulic pump at the required value, and the operation of the actuator is more stable.

[0025] Other advantages of the present invention and the technical effects of the preferred embodiments will be further described in the following specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a hydraulic principle diagram of a heat dissipation control system of an engineering machinery in the prior art;

[0027] Figure 2 is a flow chart of a method for controlling the rotation speed of a heat dissipation device for engineering machinery according to the present invention;

[0028] Figure 3 It is a hydraulic principle diagram of the pressure compensation control type hydraulic pump of the present invention;

[0029] Figure 4 It is a hydraulic principle diagram of a speed control system of a heat dissipation device for engineering machinery of the present invention;

[0030] Figure 5 This is the relationship between the fan speed and torque;

[0031] Figure 6 is a control curve diagram of the electric proportional pressure compensator of the present invention;

[0032] Figure 7 It is a schematic diagram of a curve showing a change in fan speed with load in a speed control system of the present invention;

[0033] Figure 8 The present invention is a control flow chart of a rotation speed control system for heat dissipation equipment of engineering machinery.

[0034] Reference numerals

[0035] 11 Hydraulic pump body 12 Hydraulic control reversing valve

[0036] 121 First hydraulic control port 122 Second hydraulic control port

[0037] 13 servo piston 14 electric proportional pressure compensator

[0038] 15 controller 16 first throttle valve

[0039] 17 Second throttle valve 18 Third throttle valve

[0040] 21 Internal input oil circuit 22 Internal output oil circuit

[0041] 23 Internal oil drain circuit 24 Hydraulic control oil inlet circuit

[0042] 25 Safety oil circuit

[0043] 31 Temperature sensor 32 Fan

[0044] 33 fan motor 34 power drive device

[0045] 35 oil tank 36 overflow valve

[0046] 37 Main reversing valve

[0047] 41 first working oil circuit 42 second working oil circuit

[0048] 43 Main oil inlet circuit 44 Main oil return circuit

[0049] AFirst working oil portBSecond working oil port

[0050] C Engine speed D Fan speed in the prior art

[0051] E Fan speed in the present invention F Fan target speed DETAILED DESCRIPTION

[0052] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0053] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connection" and "setting" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0054] The terms "first", "second" and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second" and "third" may explicitly or implicitly include one or more of the said features.

[0055] Figure 2 The basic flow chart of the speed control method for the heat dissipation device of engineering machinery provided by the present invention is shown. Specifically, firstly, the hydraulic oil temperature in the hydraulic system where the heat dissipation device is located is obtained, and the corresponding first pressure value is obtained according to the hydraulic oil temperature, and the corresponding second pressure value is generated according to the load pressure generated by the heat dissipation device; the magnitude of the first pressure value and the second pressure value are compared; according to the comparison result, the displacement of the hydraulic pump used to drive the heat dissipation device in the hydraulic system is adjusted, so that when the speed of the hydraulic pump changes, the flow of the hydraulic pump is stabilized within the flow setting range, thereby stabilizing the speed of the heat dissipation device within the speed setting range. Since the displacement of the hydraulic pump multiplied by the speed of the hydraulic pump is equal to the flow of the hydraulic pump multiplied by the time, when the speed of the hydraulic pump changes, the control method can adjust the displacement of the hydraulic pump in real time, so that the output flow of the hydraulic pump is basically stabilized at the required value, thereby stabilizing the speed of the heat dissipation device driven by the hydraulic pump at the required value, and the operation of the heat dissipation device is more stable.

[0056] Preferably, the displacement control mechanism of the hydraulic system includes an electric proportional pressure compensator, which obtains a corresponding current value based on the hydraulic oil temperature and inputs the current value into the electric proportional pressure compensator to control the opening pressure of the electric proportional pressure compensator, and the opening pressure is a first pressure value.

[0057] Specifically, the pressure comparison module of the hydraulic system includes a servo piston 13 for controlling the displacement and a hydraulically controlled reversing valve 12 for controlling the extension and contraction of the servo piston 13. The first pressure value and the second pressure value act on the hydraulically controlled ports at both ends of the hydraulically controlled reversing valve 12 respectively; the valve core of the hydraulically controlled reversing valve 12 can move toward the smaller one of the first pressure value and the second pressure value, thereby comparing the first pressure value and the second pressure value. When the speed of the hydraulic pump decreases, the first pressure value is greater than the second pressure value, and the displacement of the hydraulic pump is controlled to increase. When the speed of the hydraulic pump increases, the first pressure value is less than the second pressure value, and the displacement of the hydraulic pump is controlled to decrease.

[0058] A pressure-compensated controlled hydraulic pump according to an embodiment of the present invention is described in detail with reference to Figure 3 , including an electric proportional pressure compensator 14, a hydraulic pump body 11, a hydraulically controlled reversing valve 12 and a servo piston 13 for adjusting the displacement of the hydraulic pump body 11. The electric proportional pressure compensator 14 is electrically connected to a controller 15 so that the opening pressure of the electric proportional pressure compensator 14 can be adjusted by the controller 15. Figure 6Commonly, the electric proportional pressure compensator 14 adopts an inverse proportional control method, and increasing the current can reduce its opening pressure. The oil outlet of the hydraulic pump is connected to the internal output oil circuit 22, and the oil inlet is connected to the internal input oil circuit 21. The power drive device 34 is connected to the hydraulic pump body 11 to provide power to the hydraulic pump body 11. Therefore, the speed change of the power drive device 34 will cause the speed change of the hydraulic pump body 11, further affecting the output flow of the hydraulic pump body 11. The hydraulic pump body 11 can drive the actuator connected to it through the hydraulic circuit, and the output flow fluctuation of the hydraulic pump body 11 will cause the speed of the actuator to fluctuate. The first hydraulic control port 121 of the hydraulically controlled reversing valve 12 is connected to the internal oil leakage circuit 23 through the electric proportional pressure compensator 14, and the first hydraulic control port 121 is connected to the internal output oil circuit 22 through the hydraulically controlled oil inlet circuit 24 provided with a first throttle valve 16, wherein the first throttle valve 16 plays a role of pressure limitation and current limitation, so that the pressure of the first hydraulic control port 121 of the hydraulically controlled reversing valve 12 is less than the pressure of the second hydraulic control port 122, and the second hydraulic control port 122 of the hydraulically controlled reversing valve 12 is connected to the internal output oil circuit 22, and the hydraulically controlled reversing valve 12 is preferably a two-position three-way reversing valve. The rodless chamber of the servo piston 13 is respectively connected to the internal output oil circuit 22 and the internal oil leakage circuit 23 via the hydraulically controlled reversing valve 12. The pressure difference between the opening pressure of the electric proportional pressure compensator 14 and the oil outlet pressure of the hydraulic pump acts on the valve core of the hydraulically controlled reversing valve 12 through the first hydraulically controlled port 121 and the second hydraulically controlled port 122, thereby driving the hydraulically controlled reversing valve 12 to reverse, thereby selectively connecting the rodless chamber of the servo piston 13 with the internal output oil circuit 22 or the internal oil leakage circuit 23, and the rodless chamber of the servo piston 13 is filled with oil or discharged with oil, so that the push rod of the servo piston 13 is extended or retracted, thereby adjusting the displacement of the hydraulic pump body 11 by adjusting the inclination angle of the swash plate of the hydraulic pump 11.

[0059] The following is the working principle of the pressure compensation control type hydraulic pump according to the above embodiment of the present invention.

[0060] When the speed of the power drive device 34 increases and causes the speed of the hydraulic pump body 11 to increase, Figure 5, the speed of the actuator increases, thereby increasing its torque. The load pressure generated by the actuator is fed back to the oil outlet of the hydraulic pump, making the pressure of the second hydraulic control port 122 greater than the first hydraulic control port 121. The electric proportional pressure compensator 14 reaches the opening pressure, and the hydraulic oil of the internal output oil circuit 22 enters the valve cavity from the second hydraulic control port 122 of the hydraulic control reversing valve 12. The hydraulic oil flows out from the first hydraulic control port 121 and flows to the internal oil drain circuit 23 through the electric proportional pressure compensator 14. The valve core moves and connects the rodless cavity of the servo piston 13 with the internal output oil circuit 22. Oil enters the rodless cavity, and the displacement of the hydraulic pump body 11 decreases. As the displacement of the hydraulic pump body 11 gradually decreases, the The output flow rate is reduced, thereby reducing the load pressure of the actuator fed back to the oil outlet of the hydraulic pump. At this time, the pressure of the second hydraulic control port 122 is less than that of the first hydraulic control port 121. The electric proportional pressure compensator 14 is closed because the opening pressure is not reached. The hydraulic oil of the hydraulic control oil inlet oil circuit 24 enters the valve chamber from the first hydraulic control port 121, and the hydraulic oil is discharged from the second hydraulic control port 122. The valve core moves and connects the rodless chamber of the servo piston 13 with the internal oil leakage oil circuit 23. The rodless chamber leaks oil, and the displacement of the hydraulic pump body 11 increases. In this way, the opening pressure of the electric proportional pressure compensator 14 and the oil outlet pressure of the hydraulic pump are always in dynamic balance, thereby maintaining the output flow of the hydraulic pump body 11 basically at the required value. If the output flow of the hydraulic pump body 11 needs to be increased or decreased, the opening pressure of the electric proportional pressure compensator 14 can be increased or decreased.

[0061] In this way, when the speed of the power drive device 34 changes, the servo piston 13 can adjust the displacement of the hydraulic pump body 11, so that the output flow of the hydraulic pump body 11 is basically stable at the required value, and then the speed of the actuator driven by the hydraulic pump is stabilized at the required value, and the operation of the actuator is more stable; moreover, by controlling the opening pressure of the electric proportional pressure compensator 14 through the controller 15, the required value of the output flow of the hydraulic pump body 11 can be conveniently adjusted; the valve core of the hydraulically controlled reversing valve 12 continuously moves slightly and adjusts its relative position in the valve body under the action of the opening pressure of the electric proportional pressure compensator 14 and the oil outlet pressure of the hydraulic pump, so that the rodless chamber of the servo piston 13 can enter or exit oil, and the output flow of the hydraulic pump body 11 can be accurately and sensitively adjusted.

[0062] Specifically, the hydraulic pump body 11 is a variable displacement piston pump, and the displacement of the variable displacement piston pump is more convenient to adjust. The push rod of the servo piston 13 can conveniently adjust the displacement of the hydraulic pump body 11 by adjusting the inclination angle of the swash plate of the variable displacement piston pump.

[0063] Preferably, a second throttle valve 17 is provided on the connecting oil path between the rodless chamber of the servo piston 13 and the hydraulically controlled reversing valve 12. The second throttle valve 17 can adjust the speed of oil inlet and outlet of the rodless chamber of the servo piston 13. When the flow rate of the second throttle valve 17 is large, the response speed of the pressure compensation control type hydraulic pump is fast, but the hydraulic oil disturbance in the system and the impact on the pipeline are large.

[0064] Preferably, a safety oil circuit 25 is connected between the rodless chamber of the servo piston 13 and the internal oil leakage oil circuit 23, and a third throttle valve 18 is provided on the safety oil circuit 25. One end of the safety oil circuit 25 is connected to the connecting oil circuit between the rodless chamber of the servo piston 13 and the hydraulic control reversing valve 12, and the connecting point is located between the first throttle valve 16 and the second throttle valve 17; and the connecting position of the other end of the safety oil circuit 25 on the internal oil leakage oil circuit 23 is located after the connecting position of the oil outlet of the electric proportional pressure compensator 14. The valve core of the hydraulic control reversing valve 12 continuously moves slightly in the valve chamber. When the valve core is at a certain position, the hydraulic control reversing valve 12 will be closed, thereby causing the rodless chamber of the servo piston 13 to form a dead chamber, that is, the oil circuit between the rodless chamber and the hydraulic control reversing valve 12 is formed into a rigid oil circuit. It should be noted that the first, second and third throttle valves can also be replaced by damping holes.

[0065] See also Figure 4 On the basis of the technical solution of the pressure compensation control type hydraulic pump of the present invention, the present invention provides a speed control system for a heat dissipation device of an engineering machinery, comprising a temperature sensor 31 for detecting the oil temperature of hydraulic oil, a fan motor 33 for driving a fan 32 to rotate, and a pressure compensation control type hydraulic pump, wherein a hydraulic pump body 11 is connected to a power drive device 34, which can be a common drive device such as an engine or a motor, an internal input oil circuit 21 and an internal oil drain oil circuit 23 are both connected to an oil tank 35, a first working oil port A and a second working oil port B of the fan motor 33 are respectively connected to a first working oil circuit 41 and a second working oil circuit 42, the first working oil circuit 41 and the second working oil circuit 42 are connected to a main oil inlet oil circuit 43 and a main oil return oil circuit 44 via a main reversing valve 37 to switch the fan motor 33 forward or reverse, and a controller 15 is electrically connected to the temperature sensor 31 to be able to receive and control the opening pressure of the electric proportional pressure compensator 14 according to the signal of the temperature sensor 31, thereby controlling the displacement of the hydraulic pump body 11 to adjust the speed of the fan 32.

[0066] The following is the working principle of the speed control system of the heat dissipation device for engineering machinery according to the basic embodiment of the present invention.

[0067] refer to Figure 3 and Figure 7The pressure-compensated controlled hydraulic pump of the present invention is applied to the speed control system of the heat dissipation equipment. The hydraulic pump drives the hydraulic oil to enter the main oil inlet circuit 43 and the second working oil circuit 42 in sequence, and then flows back to the oil tank 35 through the first working oil circuit 41 and the main return oil circuit 44, forming a circulating oil circuit to drive the fan motor 33 to rotate forward. When the fan motor 33 rotates forward, it can drive the fan 32 to rotate forward to dissipate heat for the radiator; after the main reversing valve 37 is reversed, the hydraulic pump 11 drives the hydraulic oil to enter the main oil inlet circuit 43 and the first working oil circuit 41 in sequence, and then flows back to the oil tank 35 through the second working oil circuit 42 and the main return oil circuit 44, forming a circulating oil circuit to drive the fan motor 33 to reverse. When the fan motor 33 reverses, it can drive the fan 32 to reverse, thereby blowing away dust on the radiator. When the engine speed increases and causes the speed of the hydraulic pump 11 to increase, the load pressure generated by the fan motor 33 increases and is fed back to the oil outlet of the hydraulic pump 11. The opening pressure of the electric proportional pressure compensator 14 is less than the oil outlet pressure of the hydraulic pump, and the displacement of the pressure compensation control type hydraulic pump is adaptively reduced; the displacement of the hydraulic pump body 11 gradually decreases, and then the output flow of the hydraulic pump body 11 decreases, thereby reducing the load pressure fed back to the oil outlet of the hydraulic pump by the fan motor 33. The opening pressure of the electric proportional pressure compensator 14 is greater than the oil outlet pressure of the hydraulic pump, and the displacement of the pressure compensation control type hydraulic pump is adaptively increased. The temperature sensor sends the detected oil temperature to the controller 15, and the controller 15 outputs the corresponding current after calculation to control the opening pressure of the electric proportional pressure compensator 14 to increase or decrease the output flow of the hydraulic pump.

[0068] So, reference Figure 7 , wherein C is the engine speed, D is the fan speed in the prior art, E is the fan speed in the present invention, and F is the fan target speed. When the engine speed changes, the displacement of the pressure-compensated controlled hydraulic pump can change accordingly, so that the output flow of the hydraulic pump body 11 is basically stable at the required value, and then the speed of the fan motor 33 is basically stable at the required value. The fan speed E in the present invention is more in line with the fan target speed F, which can achieve better heat dissipation effect and can avoid or effectively reduce the noise generated by the speed fluctuation of the fan 32.

[0069] Preferably, in order to prevent impurities from mixing into the hydraulic oil and keep the hydraulic oil clean, the oil tank 35 is a closed oil tank.

[0070] Preferably, the probe of the temperature sensor 31 is arranged at the bottom of the oil tank 35 to obtain the real-time oil temperature of the hydraulic oil. Of course, the probe of the temperature sensor 31 can also be designed at other positions according to design requirements.

[0071] In order to control the pressure of the main oil inlet oil circuit 43 and allow excess flow to overflow back to the oil tank 35 , an overflow valve 36 is provided between the main oil inlet oil circuit 43 and the main oil return oil circuit 44 .

[0072] Preferably, the main reversing valve 37 is an electromagnetic reversing valve, which is electrically connected to the controller 15. The controller 15 can control the reversing of the main reversing valve 37 to switch the fan motor 33 to forward or reverse rotation.

[0073] A one-way valve is connected in parallel at both ends of the fan motor 33, and the one-way valve can replenish oil to the second working oil port B of the fan motor 33 when the fan motor 33 is reversed. The fan motor 33 rotates forward in a normal state. When it switches to reverse, the disturbance of the hydraulic oil in the system is large, which prevents the pressure of the second working oil port B of the fan motor 33 from being too high.

[0074] The engineering machinery of the present invention comprises a radiator for cooling hydraulic oil and a speed control system for a heat dissipation device for engineering machinery according to any one of the above technical solutions, and the fan motor 33 can drive the fan 32 to rotate to cool the radiator. The engineering machinery of the present invention adopts all the technical solutions of all the above embodiments, and therefore has at least all the beneficial effects brought by the technical solutions of the above embodiments.

[0075] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various specific technical features in any suitable manner. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A pressure-compensated controlled hydraulic pump, It is characterized in that The invention comprises a pressure control device, a hydraulic pump body (11) and a displacement adjustment device, wherein the displacement adjustment device is adapted to compare a first pressure value formed by the pressure control device and a second pressure value at an oil outlet of the hydraulic pump, and to adjust the displacement of the hydraulic pump body (11) according to the comparison result, so that when the rotation speed of the hydraulic pump body (11) changes, the flow rate of the hydraulic pump body (11) is stabilized within a flow rate setting range. The displacement regulating device comprises a hydraulically controlled reversing valve (12) and a servo piston (13) for regulating the displacement of the hydraulic pump body (11); the oil outlet of the hydraulic pump is connected to an internal output oil circuit (22); the oil inlet of the hydraulic pump is connected to an internal input oil circuit (21); the first hydraulic control port (121) of the hydraulically controlled reversing valve (12) is connected to the internal oil drain circuit (23) through the pressure control device; the rodless chamber of the servo piston (13) is respectively connected to the internal oil drain circuit (23) via the hydraulically controlled reversing valve (12). The internal output oil circuit (22) and the internal oil leakage circuit (23), the pressure difference between the pressure control device and the oil outlet pressure of the hydraulic pump acts on the valve core of the hydraulic control reversing valve (12) through the first hydraulic control port (121) and the second hydraulic control port (122) of the hydraulic control reversing valve (12), thereby driving the hydraulic control reversing valve (12) to change direction, thereby selectively making the rodless chamber of the servo piston (13) communicate with the internal output oil circuit (22) or the internal oil leakage circuit (23), The first hydraulic control port (121) is connected to the internal output oil circuit (22) via a hydraulic control oil inlet circuit (24) provided with a first throttle valve (16); the second hydraulic control port (122) of the hydraulic control reversing valve (12) is connected to the internal output oil circuit (22); and the hydraulic pump body (11) is a variable displacement piston pump.

2. The pressure-compensated controlled hydraulic pump according to claim 1, It is characterized in that The pressure control device is an electric proportional pressure compensator (14).

3. The pressure-compensated controlled hydraulic pump according to claim 1, It is characterized in that The hydraulically controlled reversing valve (12) is a two-position three-way reversing valve.

4. The pressure-compensated controlled hydraulic pump according to claim 2, It is characterized in that A second throttle valve (17) is provided on the connecting oil circuit between the rodless chamber of the servo piston (13) and the hydraulically controlled reversing valve (12).

5. The pressure-compensated controlled hydraulic pump according to claim 4, It is characterized in that A safety oil circuit (25) is connected between the rodless chamber of the servo piston (13) and the internal oil leakage circuit (23), and a third throttle valve (18) is provided on the safety oil circuit (25). One end of the safety oil circuit (25) is connected to the connecting oil circuit between the rodless chamber of the servo piston (13) and the hydraulically controlled reversing valve (12), and the connection point is located between the first throttle valve (16) and the second throttle valve (17); and the connection position of the other end of the safety oil circuit (25) on the internal oil leakage circuit (23) is located after the connection position of the oil outlet of the electric proportional pressure compensator (14).

6. A speed control system for heat dissipation equipment of engineering machinery, It is characterized in that It comprises a temperature sensor (31) for detecting the temperature of hydraulic oil, a fan motor (33) for driving a fan (32) to rotate, a controller (15) and a pressure-compensated controlled hydraulic pump according to any one of claims 1 to 5, wherein the temperature sensor (31) is electrically connected to the controller (15), and the controller (15) is capable of receiving and controlling a first pressure value formed by the pressure control device according to a signal from the temperature sensor (31), and the pressure generated by the fan motor (33) driving the fan (32) is fed back to the oil outlet of the hydraulic pump to form a second pressure value.

7. A construction machine, It is characterized in that It comprises a radiator for cooling hydraulic oil and a speed control system for a heat dissipation device for engineering machinery as claimed in claim 6, wherein the fan motor (33) can drive the fan (32) to rotate to cool the radiator.

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