Motor-driven closed hydraulic cylinder drive system

Abstract

The patent provides a motor-driven closed hydraulic cylinder driving system, which has stable transmission, stable performance, high transmission efficiency, no impact and shock when the high-pressure cavity of the cylinder is changed. The actual flow ratio of the first hydraulic pump / motor to the second hydraulic pump / motor is approximately equal to the effective area ratio of the rod cavity and the rodless cavity of the cylinder; one oil port of the first hydraulic pump / motor is connected to the rod cavity of the cylinder through the first oil path; the other oil port of the first hydraulic pump / motor is connected to the oil port of the hydraulic pump / motor with larger actual flow, i.e. the second hydraulic pump / motor, through the second oil path, and the second oil path is connected to the oil tank or the liquid supplementing path, or the other oil port of the first hydraulic pump / motor and the oil port of the second hydraulic pump / motor are respectively connected to the oil tank or the liquid supplementing path; the other oil port of the second hydraulic pump / motor is connected to the rodless cavity of the cylinder through the third oil path; the two hydraulic pump / motors are connected to the motor through a mechanical transmission mechanism.

Description

Technical Field

[0001] This patent relates to a closed hydraulic system, specifically a motor-driven closed hydraulic cylinder drive system. Background Technology

[0002] In the field of construction machinery, open hydraulic structures are generally used. Due to the use of a single engine, the hydraulic system design is very complex. The hydraulic oil flows continuously at high speed in the oil circuit and the action is controlled by throttling, resulting in a complex system structure and low efficiency.

[0003] Closed-loop hydraulic transmission can largely avoid ineffective hydraulic oil flow and offers high transmission efficiency. However, closed-loop hydraulic systems are primarily suitable for scenarios where the loads in both directions are relatively balanced and the oil intake and discharge volumes of the actuators are equal during forward and reverse movements, such as the swing and travel of excavators. For cylinder-type actuators, due to unbalanced loads and significant differences in oil intake and discharge volumes, closed-loop hydraulic applications are difficult to implement. While a balance valve structure can solve the volume balance problem between the rod-side and rodless chambers of the cylinder, the difference in volume during high-pressure transfer from one chamber to another inevitably generates impacts and vibrations, rendering it impractical. Furthermore, some structures using a single hydraulic pump / motor generate impacts when the pump / motor changes direction, affecting its lifespan and making them particularly unsuitable for use in high-load electric construction machinery.

[0004] For example, the technology described in the document with application publication number CN119900740A can achieve the same high performance, but when the high pressure chamber of the hydraulic cylinder changes, the sudden change in the working cross section inevitably causes impact or vibration, resulting in poor performance. Summary of the Invention

[0005] This patent provides a motor-driven closed hydraulic cylinder drive system, which features smooth transmission, stable performance, high transmission efficiency, and no impact or vibration during high-pressure chamber changes in the cylinder. It is especially suitable for electric engineering machinery with heavy operating loads.

[0006] To achieve the above technical objectives, the technical solution adopted in this patent is as follows:

[0007] A closed hydraulic cylinder drive system driven by an electric motor includes an electric motor, at least two hydraulic pumps / motors, and at least one cylinder; the ratio of the actual flow rates of the two hydraulic pumps / motors is approximately equal to the ratio of the effective working areas of the rod chamber and the rodless chamber of the cylinder; one port of the hydraulic pump / motor with the smaller actual flow rate, i.e., the first hydraulic pump / motor, is connected to the rod chamber of the cylinder through a first oil passage.

[0008] The other oil port of the first hydraulic pump / motor is connected to one oil port of the second hydraulic pump / motor, which has a larger actual flow rate, through a second oil circuit. The second oil circuit is connected to the oil tank or the replenishment oil circuit. Alternatively, the other oil port of the first hydraulic pump / motor and one oil port of the second hydraulic pump / motor are respectively connected to the oil tank or the replenishment oil circuit.

[0009] The other port of the second hydraulic pump / motor is connected to the rodless chamber of the cylinder through a third oil circuit; both hydraulic pumps / motors are simultaneously connected to the motor through a mechanical transmission mechanism.

[0010] When the hydraulic cylinder is working, the difference in hydraulic oil displacement between the two chambers is balanced through a replenishment oil circuit or an oil tank. When the two ports of the two hydraulic pumps / motors are connected through a second oil circuit, excess hydraulic oil enters the oil tank through the second oil circuit, and insufficient hydraulic oil is replenished from the oil tank through the second oil circuit, or from the replenishment oil circuit through the second oil circuit. When the two ports of the two hydraulic pumps / motors are respectively connected to an oil tank or a replenishment oil circuit, excess hydraulic oil enters the oil tank, and insufficient hydraulic oil is replenished from the oil tank through the oil tank, or from the replenishment oil circuit.

[0011] To compensate for insufficient hydraulic oil caused by leaks, a first check valve is installed between the first and second hydraulic lines, allowing oil to flow from the second line to the first line. Similarly, a first check valve is installed between the third and second hydraulic lines, allowing oil to flow from the second line to the third line. This is used to replenish hydraulic oil from the tank or replenishment line to the cylinder when the hydraulic oil level in the cylinder is insufficient due to leaks or other reasons.

[0012] As a further improvement to the aforementioned motor-driven closed hydraulic cylinder drive system, the replenishing hydraulic circuit includes a replenishing hydraulic pump, the inlet of which is connected to the oil tank. The replenishing hydraulic pump pumps hydraulic oil from the tank into the second hydraulic circuit, providing a minimum oil pressure guarantee for the hydraulic pump / motor and replenishing hydraulic oil to the second hydraulic pump / motor with a larger flow rate; alternatively, when the hydraulic oil volume in the first or third hydraulic circuit is insufficient due to leakage or other reasons, resulting in low pressure, the replenishing hydraulic circuit replenishes hydraulic oil to the first or third hydraulic circuit.

[0013] As a further improvement to the aforementioned motor-driven closed hydraulic cylinder drive system, it also includes a first check valve and a second check valve; the replenishing oil circuit includes a replenishing hydraulic pump, the inlet of which is connected to the oil tank, and the outlet of which is connected to the first oil circuit and the third oil circuit respectively by a first check valve and a second check valve. When the first check valve is open, hydraulic oil flows from the outlet of the replenishing hydraulic pump or the second oil circuit into the first oil circuit. When the second check valve is open, hydraulic oil flows from the outlet of the replenishing hydraulic pump or the second oil circuit into the third oil circuit.

[0014] At this time, the difference in hydraulic oil displacement between the two chambers during cylinder operation is balanced through the replenishment oil circuit and the replenishment check valve (first check valve or second check valve). When the two ports of the two hydraulic pumps / motors are connected through the second oil circuit, excess hydraulic oil enters the lower-pressure rod chamber through the second oil circuit and the first check valve, or enters the lower-pressure rodless chamber through the second oil circuit and the second check valve; insufficient hydraulic oil is pumped in from the oil tank through the replenishment hydraulic pump to make up the difference. When the two ports of the two hydraulic pumps / motors are respectively connected to the replenishment oil circuit, excess hydraulic oil enters the lower-pressure rodless chamber through the second check valve, and insufficient hydraulic oil is pumped in from the oil tank through the replenishment hydraulic pump to make up the difference.

[0015] As a further improvement to the aforementioned motor-driven closed hydraulic cylinder drive system, the first hydraulic pump / motor and / or the second hydraulic pump / motor are variable pumps / motors.

[0016] As a further improvement to the aforementioned motor-driven closed hydraulic cylinder drive system, the mechanical transmission mechanism is a speed-changing mechanism with two output shafts, which are respectively connected to a first hydraulic pump / motor and a second hydraulic pump / motor.

[0017] As a further improvement to the aforementioned motor-driven closed hydraulic cylinder drive system, the input shafts of the first hydraulic pump / motor and the second hydraulic pump / motor are arranged coaxially and connected to the motor.

[0018] As a further improvement to the aforementioned motor-driven closed hydraulic cylinder drive system, the first, second, or third oil circuits are connected to the oil tank via an overflow valve.

[0019] The beneficial effects of this patent are as follows:

[0020] When the motor rotates, it drives the first and second hydraulic pumps to rotate simultaneously. When oil enters through the port of the first hydraulic pump connected to the rod chamber, oil exits through the port of the second hydraulic pump connected to the rodless chamber. Similarly, when oil exits through the port of the first hydraulic pump connected to the rod chamber, oil enters through the port of the second hydraulic pump connected to the rodless chamber. Since the actual flow ratio of the two hydraulic pumps (the first and second hydraulic pumps) is the same as the ratio of the hydraulic action cross-sectional areas of the two chambers (the rod chamber and the rodless chamber) of the cylinder, the hydraulic oil can flow smoothly. Moreover, since the flow rate of the oil in the two chambers of the cylinder is proportional to the motor speed, when the motor is rotating stably, the piston speed of the cylinder is stable when the high-pressure chamber of the cylinder changes (one chamber changes from high pressure to low pressure, while the other chamber changes from low pressure to high pressure) and before and after the change, resulting in smooth high-speed operation of the system. Simultaneously, the oil ports of the two hydraulic pumps that are not connected to the cylinders are connected together, or they are respectively connected to the oil tank or replenishment line. Most of the hydraulic oil entering and leaving the cylinders forms a circuit through the two pumps. The insufficient or excess hydraulic oil is exchanged with the hydraulic oil in the replenishment line or oil tank, which can both dissipate heat and flush the hydraulic pumps / motors and cylinders. In addition, each hydraulic pump operates in a unidirectional direction, eliminating the impact caused by reversing and ensuring the service life of the hydraulic pumps / motors.

[0021] This structure offers smooth transmission, stable performance, and high transmission efficiency, making it highly valuable for practical applications. Attached Figure Description

[0022] Figure 1 , 2 These are all schematic diagrams of the closed hydraulic cylinder drive system of Example 1.

[0023] Figure 3 This is a schematic diagram of the closed hydraulic cylinder drive system of Example 2.

[0024] Figure 4 This is a schematic diagram of the closed hydraulic cylinder drive system of Example 3.

[0025] Figure 5-8 These are all schematic diagrams of the closed hydraulic cylinder drive system of Example 4.

[0026] Figure 9 This is a schematic diagram of the closed hydraulic cylinder drive system of Example 5.

[0027] Figure 10 This is a schematic diagram of the closed hydraulic cylinder drive system of Example 6.

[0028] Figure 11 This is a schematic diagram of the closed hydraulic cylinder drive system of Example 7. Detailed Implementation

[0029] Example 1:

[0030] Please see Figure 1 , 2 This embodiment 1 provides a motor-driven closed hydraulic cylinder drive system, including a motor 5, two hydraulic pumps / motors, namely a first hydraulic pump / motor 1 and a second hydraulic pump / motor 2, and a cylinder 4.

[0031] One port of the hydraulic pump / motor with a smaller actual flow rate (i.e., the first hydraulic pump / motor 1) is connected to the rod chamber of the cylinder via the first oil passage 11. The other port of the first hydraulic pump / motor 1 is connected to one port of the hydraulic pump / motor with a larger actual flow rate (i.e., the second hydraulic pump / motor 2) via the second oil passage 12. The other port of the second hydraulic pump / motor 2 is connected to the rodless chamber of the cylinder 4 via the third oil passage 13. The first oil passage 11 is connected to the second oil passage 12 via a first check valve 21 that only allows hydraulic oil to flow from the second oil passage to the first oil passage. The third oil passage 13 is connected to the second oil passage 12 via a second check valve 22 that only allows hydraulic oil to flow from the second oil passage to the third oil passage. Both hydraulic pumps / motors are simultaneously connected to the motor 5 via a speed-changing mechanism 7 with two output shafts. The two hydraulic pumps / motors operate at different speeds.

[0032] The motor 5 drives the first hydraulic pump / motor 1 and the second hydraulic pump / motor 2 simultaneously through the speed change mechanism 7. The ratio of the actual flow rate of the first hydraulic pump / motor 1 to that of the second hydraulic pump / motor 2 is approximately equal to the ratio of the effective working area of ​​the rod chamber and the rodless chamber of the cylinder 4.

[0033] See Figure 1 When motor 5 starts, both the first hydraulic pump / motor 1 and the second hydraulic pump / motor 2 operate as hydraulic pumps. When the rod chamber is a high-pressure chamber, the first hydraulic pump / motor 1 outputs hydraulic oil into the rod chamber of cylinder 4, while the hydraulic oil flowing out of the rodless chamber of cylinder 4 enters the second hydraulic pump / motor 2. A portion of the hydraulic oil coming out of the second hydraulic pump / motor 2 returns to the first hydraulic pump / motor 1, and the excess hydraulic oil flows back into the second hydraulic pump / motor 2 through the second check valve 22.

[0034] See Figure 2 Both the first hydraulic pump / motor 1 and the second hydraulic pump / motor 2 operate as motors. When the rodless chamber is a high-pressure chamber, the first hydraulic pump / motor 1 outputs hydraulic oil into the rod chamber of the cylinder 4. The hydraulic oil flowing out of the rodless chamber of the cylinder 4 enters the second hydraulic pump / motor 2, driving it. A portion of the hydraulic oil exiting the second hydraulic pump / motor 2 enters the first hydraulic pump / motor 1, driving it. Excess hydraulic oil passes through the first check valve 21 and enters the rod chamber of the cylinder 4. Of course, the hydraulic oil flowing out of the first hydraulic pump / motor 1 also enters the rod chamber of the cylinder 4. The arrows in the diagram indicate the flow direction of the hydraulic oil.

[0035] Example 2:

[0036] Please see Figure 3 This embodiment 2 provides a motor-driven closed hydraulic cylinder drive system. The main difference between embodiment 2 and embodiment 1 is that it also includes an oil tank 8, a replenishing hydraulic pump 3, and a replenishing drive motor 6 that drives the replenishing hydraulic pump 3. The oil outlet of the replenishing hydraulic pump 3 is connected to the second oil circuit 12. That is to say, while the oil outlet of the replenishing hydraulic pump 3 is connected to the second oil circuit, it is also connected to the first oil circuit 11 through the first check valve 21, and to the third oil circuit 13 through the second check valve 22.

[0037] In addition to being the same as that described in Example 1, the working process of Example 2 may also include the following working process.

[0038] When motor 5 starts, both the first hydraulic pump / motor 1 and the second hydraulic pump / motor 2 operate as hydraulic pumps. When the rod chamber is in a low-pressure state, hydraulic oil from the rod chamber of cylinder 4 enters the first hydraulic pump / motor 1, and hydraulic oil from the second hydraulic pump / motor 2 enters the rodless chamber of cylinder 4. Hydraulic oil from the first hydraulic pump / motor 1 enters the second hydraulic pump / motor 2. Simultaneously, the replenishing hydraulic pump 3 operates, and hydraulic oil in the oil tank 8 replenishes the second hydraulic pump / motor 2 through the second oil circuit 12 to compensate for any insufficient hydraulic oil.

[0039] When both the first hydraulic pump / motor 1 and the second hydraulic pump / motor 2 operate as motors, and the rod chamber is a high-pressure chamber, the hydraulic oil exiting the rod chamber of cylinder 4 enters the first hydraulic pump / motor 1, and the hydraulic oil flowing out of the first hydraulic pump / motor 1 enters the second hydraulic pump / motor 2. The hydraulic oil exiting the second hydraulic pump / motor 2 enters the rod chamber of cylinder 4. Simultaneously, the replenishing hydraulic pump 3 operates, and the hydraulic oil in the oil tank 8 enters the second hydraulic pump / motor 2 through the second oil passage 12, replenishing the second hydraulic pump / motor 2 to compensate for any insufficient hydraulic oil.

[0040] In addition, since there are replenishing check valves, namely the first check valve 21 and the second check valve 22, when the hydraulic oil volume in the cylinder chamber (rod chamber or rodless chamber) is insufficient due to leakage, hydraulic oil can be replenished into the cylinder from the oil tank (when the replenishing hydraulic pump is working) or the second oil circuit through the replenishing check valve.

[0041] Example 3:

[0042] Please see Figure 4This embodiment 3 provides a motor-driven closed hydraulic cylinder drive system. The main difference between Embodiment 3 and Embodiment 2 is that the input shafts of the first hydraulic pump / motor 1 and the second hydraulic pump / motor 2 are coaxially connected and directly connected to the motor 5 or connected to the motor 5 through a speed change mechanism. The two hydraulic pumps / motors operate at the same speed. The working process of Embodiment 3 is the same as that of Embodiment 2.

[0043] Example 4:

[0044] Please see Figure 5-8 This embodiment 4 provides a motor-driven closed hydraulic cylinder drive system, including a motor 5, two hydraulic pumps / motors, namely the first hydraulic pump / motor 1 and the second hydraulic pump / motor 2, a cylinder 4, and an oil tank 8.

[0045] One port of the hydraulic pump / motor with a smaller actual flow rate (i.e., the first hydraulic pump / motor 1) is connected to the rod chamber of the cylinder via the first oil passage 11. The other port of the first hydraulic pump / motor 1 is connected to one port of the hydraulic pump / motor with a larger actual flow rate (i.e., the second hydraulic pump / motor 2) via the second oil passage 12. The other port of the second hydraulic pump / motor 2 is connected to the rodless chamber of the cylinder 4 via the third oil passage 13. The second oil passage 12 is directly connected to the oil tank 8. The two hydraulic pumps / motors are simultaneously connected to the motor 5 via a speed change mechanism 7 with two output shafts. The two hydraulic pumps / motors operate at different speeds.

[0046] The motor 5 drives the first hydraulic pump / motor 1 and the second hydraulic pump / motor 2 simultaneously through the speed change mechanism 7. The ratio of the actual flow rate of the first hydraulic pump / motor 1 to that of the second hydraulic pump / motor 2 is approximately equal to the ratio of the effective working area of ​​the rod chamber and the rodless chamber of the cylinder 4.

[0047] See Figure 5 When motor 5 starts, both the first hydraulic pump / motor 1 and the second hydraulic pump / motor 2 operate as hydraulic pumps. When the rod chamber is the high-pressure chamber, the first hydraulic pump / motor 1 outputs hydraulic oil into the rod chamber of cylinder 4, while the hydraulic oil flowing out of the rodless chamber of cylinder 4 enters the second hydraulic pump / motor 2. A portion of the hydraulic oil from the second hydraulic pump / motor 2 returns to the first hydraulic pump / motor 1, and the excess hydraulic oil flows into the oil tank 8. (See also...) Figure 6 When the rodless chamber is a high-pressure chamber, the hydraulic oil output from the second hydraulic pump / motor 2 enters the rodless chamber of the cylinder 4, and the hydraulic oil flowing out of the rod chamber of the cylinder 4 enters the first hydraulic pump / motor 1. The hydraulic oil coming out of the first hydraulic pump / motor 1 enters the second hydraulic pump / motor 2, and the insufficient hydraulic oil enters the second hydraulic pump / motor 2 from the oil tank 8 through the second oil circuit 12.

[0048] See Figure 7Both the first hydraulic pump / motor 1 and the second hydraulic pump / motor 2 operate as motors. When the rodless chamber is a high-pressure chamber, the hydraulic oil flowing from the first hydraulic pump / motor 1 enters the rod chamber of the cylinder 4, and the hydraulic oil flowing from the rodless chamber of the cylinder 4 enters the second hydraulic pump / motor 2, driving the second hydraulic pump / motor 2. A portion of the hydraulic oil from the second hydraulic pump / motor 2 enters the first hydraulic pump / motor 1 to drive the first hydraulic pump / motor 1, while the excess hydraulic oil flows into the oil tank 8. (See also...) Figure 8 When the rod chamber is a high-pressure chamber, the hydraulic oil flowing out of the rod chamber of cylinder 4 enters the first hydraulic pump / motor 1, driving the first hydraulic pump / motor 1. The hydraulic oil coming out of the first hydraulic pump / motor 1 enters the second hydraulic pump / motor 2, and the insufficient hydraulic oil enters the second hydraulic pump / motor 2 from the oil tank 8 through the second oil circuit 12.

[0049] Example 5:

[0050] Please see Figure 9 This embodiment 5 provides a motor-driven closed-loop hydraulic cylinder drive system. The main difference between embodiment 5 and embodiment 4 is that it also includes replenishing check valves, namely a first check valve 21 and a second check valve 22. The first check valve 21 is connected between the first oil passage 11 and the second oil passage 12, and the second check valve 22 is connected between the third oil passage 13 and the second oil passage 12, all connected to the oil tank 8. The first check valve 21 only allows hydraulic oil to flow from the second oil passage 12 or the oil tank 8 to the first oil passage 11, and the second check valve 22 only allows hydraulic oil to flow from the second oil passage 12 or the oil tank 8 to the third oil passage 13.

[0051] Its working process is basically the same as that of Example 4. Of course, since this example has a replenishing check valve, when the hydraulic oil volume in the cylinder chamber (rod chamber or rodless chamber) is insufficient due to leakage, hydraulic oil can be replenished into the cylinder from the oil tank or the second oil circuit through the replenishing check valve.

[0052] Example 6:

[0053] Please see Figure 10 This embodiment 6 provides a motor-driven closed hydraulic cylinder drive system. The main difference between Embodiment 6 and Embodiment 5 is that the input shafts of the first hydraulic pump / motor 1 and the second hydraulic pump / motor 2 are coaxially connected and directly connected to the motor 5 or connected to the motor 5 through a speed change mechanism. The two hydraulic pumps / motors operate at the same speed. The working process of Embodiment 6 is the same as that of Embodiment 5.

[0054] Example 7:

[0055] Please see Figure 11This embodiment 7 provides a motor-driven closed hydraulic cylinder drive system, including a motor 5, two hydraulic pumps / motors, namely a first hydraulic pump / motor 1 and a second hydraulic pump / motor 2, and a cylinder 4.

[0056] The hydraulic pump / motor with a smaller actual flow rate, i.e., the first hydraulic pump / motor 1, has one port connected to the rod chamber of the cylinder via the first oil passage 11, and the other port connected to the oil tank 8. The hydraulic pump / motor with a larger actual flow rate, i.e., the second hydraulic pump / motor 2, has one port connected to the oil tank 8, and the other port connected to the rodless chamber of the cylinder 4 via the third oil passage 13. A first check valve 21 is connected between the first oil passage 11 and the other port of the first hydraulic pump / motor 1. Under the action of the first check valve 21, hydraulic oil can only flow into the first oil passage 11 from the oil tank 8 or the other port of the first hydraulic pump / motor 1.

[0057] The second check valve 22 is connected between the third oil circuit 13 and one of the ports of the second hydraulic pump / motor 2. Under the action of the second check valve 22, hydraulic oil can only flow into the third oil circuit 13 from the oil tank 8 or one of the ports of the second hydraulic pump / motor 2. The two hydraulic pumps / motors are simultaneously connected to the motor 5 via a speed change mechanism 7 with two output shafts, and the two hydraulic pumps / motors operate at different speeds. Of course, the input shafts of the first hydraulic pump / motor 1 and the second hydraulic pump / motor 2 can also be coaxially connected and directly connected to the motor, or connected to the motor via a speed change mechanism, similar to... Figure 4 and Figure 10 At this time, the two hydraulic pumps / motors operate at different speeds.

[0058] The motor 5 drives the first hydraulic pump / motor 1 and the second hydraulic pump / motor 2 simultaneously through the speed change mechanism 7. The ratio of the actual flow rate of the first hydraulic pump / motor 1 to that of the second hydraulic pump / motor 2 is approximately equal to the ratio of the effective working area of ​​the rod chamber and the rodless chamber of the cylinder 4.

[0059] See Figure 11 When motor 5 starts, both the first hydraulic pump / motor 1 and the second hydraulic pump / motor 2 operate as hydraulic pumps. When the rod chamber is a high-pressure chamber, hydraulic oil is output from the oil tank 8 via the first hydraulic pump / motor 1 and enters the rod chamber of cylinder 4. Hydraulic oil flowing out of the rodless chamber of cylinder 4 enters the second hydraulic pump / motor 2, and hydraulic oil exiting from the second hydraulic pump / motor 2 enters the oil tank 8. When the rodless chamber is a high-pressure chamber, hydraulic oil is output from the oil tank 8 via the second hydraulic pump / motor 2 and enters the rodless chamber of cylinder 4. Hydraulic oil flowing out of the rod chamber of cylinder 4 enters the first hydraulic pump / motor 1, and hydraulic oil exiting from the first hydraulic pump / motor 1 enters the oil tank 8.

[0060] Because this embodiment has a replenishing check valve, when the hydraulic oil volume in the cylinder chamber (rod chamber or rodless chamber) is insufficient due to leakage or other reasons, hydraulic oil can be replenished from the oil tank to the cylinder through the replenishing check valve.

[0061] Of course, for embodiments 1-6, the first oil circuit 11, the second oil circuit 12, or the third oil circuit 13 can all be connected to the oil tank through the relief valve. When the second oil circuit 12 is connected to the oil tank through the relief valve, excess hydraulic oil in the hydraulic oil coming out of the second hydraulic pump / motor 2 can also flow into the oil tank through the relief valve.

[0062] This patent describes a motor-driven closed hydraulic cylinder drive system, comprising at least one motor, at least two hydraulic pumps / motors, and at least one cylinder. The ratio of the actual flow rates of the two hydraulic pumps / motors is approximately equal to the ratio of the effective working areas of the rod chamber and the rodless chamber of the cylinder. One port of the hydraulic pump / motor with the smaller actual flow rate is connected to the rod chamber of the cylinder, and one port of the hydraulic pump / motor with the larger actual flow rate is connected to the rodless chamber of the cylinder. The two hydraulic pumps / motors are simultaneously connected to the motor via a mechanical mechanism.

[0063] Structure 1: Two hydraulic pumps / motors are used, each connected to a gear, which is connected to the motor through a gear transmission mechanism. The ratio of the displacement of the two hydraulic pumps / motors plus the gear transmission ratio is the same as the ratio of the hydraulic action cross sections of the rod chamber and the rodless chamber of the cylinder.

[0064] Structure 2: Two hydraulic pumps / motors with the same displacement ratio as the ratio of the hydraulic action area of ​​the rod chamber and rodless chamber of the cylinder are arranged coaxially and connected to the motor.

[0065] To compensate for insufficient oil volume due to leakage, a fluid replenishment check valve is installed in both chambers of the cylinder. For example, a first check valve is installed between the rod chamber and the oil tank or the second oil circuit, and a second check valve is installed between the rodless chamber and the oil tank or the second oil circuit. When the oil volume is insufficient, hydraulic oil is drawn from the low-pressure oil circuit.

[0066] If the hydraulic pump / motor requires a replenishment system, a replenishment system (a replenishment oil circuit consisting of a replenishment hydraulic pump 3, a replenishment drive motor 6, etc.) can be set up in the low-pressure circuit to provide a minimum oil pressure guarantee for the hydraulic pump / motor driving the cylinder. However, this is not mandatory and should be configured according to the usage requirements of the hydraulic pump / motor.

[0067] The hydraulic pump / motor mentioned can be either a constant displacement pump or a variable displacement pump.

[0068] Overflow valves can be installed on the oil lines at both ends of the oil cylinder to protect the oil lines and related components. The overflow end of the overflow valve can be connected to the replenishing oil line or directly connected to the oil tank.

[0069] When the motor rotates, it drives both pumps to rotate simultaneously. Oil enters through the port of the pump connected to the rod chamber and exits through the port of the pump connected to the rodless chamber; similarly, oil exits through the port of the pump connected to the rod chamber and enters through the port of the pump connected to the rodless chamber. Because the actual flow rate ratio of the pumps is the same as the ratio of the hydraulic action cross-sectional areas of the two chambers of the cylinder, the hydraulic oil can flow smoothly. Furthermore, since the oil flow rate in the two chambers of the cylinder is proportional to the motor speed, the piston speed of the cylinder remains stable when the high-pressure chamber changes (one chamber changes from high pressure to low pressure while the other changes from low pressure to high pressure) and before and after the change, ensuring smooth system operation. If the ports of the two pumps that are not connected to the cylinder are connected nearby, most of the hydraulic oil in the cylinder will pass through the two pumps in a loop. The insufficient or excess oil will be exchanged with the hydraulic oil in the low-pressure oil circuit (replenishment oil circuit or oil tank), which can both dissipate heat and flush the hydraulic pump / motor and the cylinder.

[0070] The scope of protection of this patent includes, but is not limited to, the above-described embodiments. The scope of protection of this patent is determined by the claims. Any substitutions, modifications, or improvements to this technology that are easily conceived by those skilled in the art shall fall within the scope of protection of this patent.

Claims

1. A closed-loop hydraulic cylinder drive system driven by an electric motor, characterized in that, It includes one motor, at least two hydraulic pumps / motors, and at least one cylinder; the ratio of the actual flow rates of the two hydraulic pumps / motors is approximately equal to the ratio of the effective working areas of the rod chamber and the rodless chamber of the cylinder; one port of the hydraulic pump / motor with the smaller actual flow rate, i.e., the first hydraulic pump / motor, is connected to the rod chamber of the cylinder through a first oil passage. The other oil port of the first hydraulic pump / motor is connected to one oil port of the second hydraulic pump / motor, which has a larger actual flow rate, through a second oil circuit. The second oil circuit is connected to the oil tank or the replenishment oil circuit. Alternatively, the other oil port of the first hydraulic pump / motor and one oil port of the second hydraulic pump / motor are respectively connected to the oil tank or the replenishment oil circuit. The other port of the second hydraulic pump / motor is connected to the rodless chamber of the cylinder through a third oil circuit; both hydraulic pumps / motors are simultaneously connected to the motor through a mechanical transmission mechanism.

2. The motor-driven closed hydraulic cylinder drive system according to claim 1, characterized in that, A first check valve is installed between the first oil circuit and the second oil circuit, allowing oil to flow from the second oil circuit to the first oil circuit. A second check valve is installed between the third oil circuit and the second oil circuit, allowing oil to flow from the second oil circuit to the third oil circuit.

3. The motor-driven closed hydraulic cylinder drive system according to claim 1, characterized in that, The fluid replenishment circuit includes a fluid replenishment hydraulic pump, whose inlet is connected to the oil tank.

4. The motor-driven closed hydraulic cylinder drive system according to claim 1, characterized in that, It also includes a first check valve and a second check valve; the replenishing oil circuit includes a replenishing hydraulic pump, the inlet of which is connected to the oil tank, and the outlet of which is connected to the first oil circuit and the third oil circuit respectively by a first check valve and a second check valve. When the first check valve is open, hydraulic oil flows from the outlet of the replenishing hydraulic pump or the second oil circuit into the first oil circuit. When the second check valve is open, hydraulic oil flows from the outlet of the replenishing hydraulic pump or the second oil circuit into the third oil circuit.

5. The motor-driven closed hydraulic cylinder drive system according to claim 1, characterized in that, The first hydraulic pump / motor and / or the second hydraulic pump / motor are variable displacement pumps / motors.

6. The motor-driven closed hydraulic cylinder drive system according to claim 1, characterized in that, The mechanical transmission mechanism is a speed-changing mechanism with two output shafts, which are respectively connected to the first hydraulic pump / motor and the second hydraulic pump / motor.

7. The motor-driven closed hydraulic cylinder drive system according to claim 1, characterized in that, The input shafts of the first hydraulic pump / motor and the second hydraulic pump / motor are arranged coaxially and connected to the motor.

8. The motor-driven closed hydraulic cylinder drive system according to claim 1, characterized in that, The first or third oil circuit is connected to the oil tank via an overflow valve.

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