Vehicle drive system

Abstract

To provide a technology for suppressing excessive vibration in an electric oil pump in a vehicle equipped with an engine and an electric oil pump. [Solution] The drive unit comprises a drive system including an engine, a casing housing the drive system, an oil circulation path provided in the casing, an electric oil pump that circulates oil along the oil circulation path, an oil reservoir provided inside or near the electric oil pump and storing oil branched off from the oil circulation path, and a control device that adjusts the amount of oil stored in the oil reservoir, the control device changing the amount of oil stored in the oil reservoir according to the engine speed.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a driving device for a vehicle.

Background Art

[0002] Patent Document 1 discloses a transaxle for a hybrid vehicle. An inverter, an engine, etc. are attached to this transaxle. Further, this transaxle includes pump parts such as an oil cooler and an oil pump. That is, in the technology of Patent Document 1, a drive mechanism such as an engine and an oil pump are integrally configured.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a vehicle including an engine and an electric oil pump, when the engine rotates, a frequency vibration occurs in the rotational speed of the engine. When the frequency of the vibration generated by the rotation of the engine coincides with the resonance frequency of the electric oil pump, resonance occurs in the electric oil pump. In this specification, in a vehicle including an engine and an electric oil pump, a technology for suppressing excessive vibration from occurring in the electric oil pump is provided.

Means for Solving the Problems

[0005] The technology disclosed herein is embodied in a vehicle drive system. In a first embodiment, the drive system includes a drive system including an engine, a casing housing the drive system, an oil circulation path provided in the casing, an electric oil pump for circulating oil along the oil circulation path, an oil reservoir provided inside or near the electric oil pump and branching off from the oil circulation path to store the oil, and a control device for adjusting the amount of oil stored in the oil reservoir, wherein the control device changes the amount of oil stored in the oil reservoir according to the rotational speed of the engine.

[0006] Depending on the engine speed, vibrations occur at a frequency that closely matches the resonant frequency of the electric oil pump. In such cases, the control device changes the amount of oil stored in the oil reservoir. Generally, the resonant frequency of the electric oil pump is determined by its structure, shape, and materials. By changing the amount of oil stored in the oil reservoir, the resonant frequency of the electric oil pump changes. As a result, the occurrence of resonance caused by engine operation in the electric oil pump is suppressed. Consequently, excessive vibration in the electric oil pump is prevented.

[0007] In a second aspect of this technology, in addition to the first aspect described above, the control device may change the amount of oil stored in the oil reservoir depending on whether the engine is operating in a specific rotational speed range or not. The specific rotational speed range is not particularly limited, but it may be a rotational speed range that causes resonance in the electric oil pump. In such a configuration, when the engine is operating in a specific rotational speed range, the resonant frequency of the electric oil pump is changed, thereby suppressing the occurrence of resonance in the electric oil pump caused by the engine's operation. Consequently, excessive vibration in the electric oil pump is suppressed.

[0008] In a third aspect of this technology, in addition to the first or second aspect described above, the device may further include at least one valve for connecting and disconnecting the electric oil pump and the oil reservoir. The control device may change the amount of oil stored in the oil reservoir by controlling the operation of the at least one valve. In this configuration, the control device can change the amount of oil stored in the oil reservoir by controlling the operation of the valve.

[0009] The technology disclosed herein is embodied in a drive system for another vehicle. In a fourth embodiment, the drive system comprises a drive system including an engine, a casing housing the drive system, an oil circulation path provided in the casing, an electric oil pump for circulating oil along the oil circulation path, and a pump control device for controlling the rotational speed of the electric oil pump, wherein the pump control device changes the rotational speed of the electric oil pump in accordance with the rotational speed of the engine.

[0010] Depending on the engine speed, vibrations occur at a frequency that closely matches the resonant frequency of the electric oil pump. The control device changes the rotation speed of the electric oil pump according to the engine speed. The rotation of the electric oil pump can generate vibrations that cancel out or at least reduce the vibrations caused by the engine's operation. Therefore, the occurrence of resonance caused by the engine's operation is suppressed in the electric oil pump. Consequently, excessive vibrations in the electric oil pump are suppressed.

[0011] In a fifth aspect of this technology, in addition to the fourth aspect described above, the pump control device may change the rotational speed of the electric oil pump depending on whether the engine is operating in a specific rotational speed range or not. While not particularly limited, the specific rotational speed range may be a rotational speed range that causes resonance in the electric oil pump. In this case, the pump control device may change the rotational speed of the electric oil pump so that vibrations of opposite phase are generated in the electric oil pump. In such a configuration, the operation of the electric oil pump generates vibrations of opposite phase to those generated by the engine operation. By changing the rotational speed of the electric oil pump, vibrations can be generated that cancel out or at least reduce the vibrations caused by the engine operation. Therefore, the occurrence of resonance caused by the engine operation is suppressed in the electric oil pump. Consequently, excessive vibrations in the electric oil pump are suppressed. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram showing the configuration of the drive unit. [Figure 2] This is a schematic cross-sectional view of an electric oil pump. [Figure 3] This is a schematic top view of an electric oil pump. [Figure 4] This is a diagram to explain the flow of oil. [Figure 5] This diagram illustrates the magnitude of vibration in an electric oil pump. [Modes for carrying out the invention]

[0013] (First embodiment) The drive unit 2 of the first embodiment will be described with reference to the drawings. The drive unit 2 of this embodiment is installed in a so-called hybrid vehicle having an engine 22 and a motor 24 for driving. In a modified example, the drive unit 2 may be installed in a vehicle that has an engine but no motor for driving. The drive unit 2 comprises a control device 10, an engine 22, a motor 24, a gear group 26, a pair of drive shafts 28, and an electric oil pump 30. Hereinafter, the engine 22, motor 24, and gear group 26 may be collectively referred to as the "drive system". The drive system is housed in a casing 4.

[0014] The casing 4 is the outer shell of the drive unit 2 and is made of, for example, metal. The casing 4 is provided with an oil circulation path (not shown). The oil circulation path is a path through which oil circulates for the purpose of lubrication and cooling. Details of the circulation path will be described later with reference to Figure 4.

[0015] The control device 10 controls the operation of the drive system based on commands from, for example, a higher-level control device (not shown). Furthermore, as will be described in detail later, the control device 10 adjusts the amount of oil stored in the oil reservoir 38 located inside or near the electric oil pump 30.

[0016] Engine 22 is a heat engine that generates power by burning fuel, such as a gasoline engine or a diesel engine. Motor 24 is a motor for driving the vehicle to which the drive unit 2 is installed. Power is supplied to motor 24 from a battery (not shown) via a power converter (not shown). Specifically, the DC power output from the battery is converted to AC power by the power converter, and the converted AC power is supplied to motor 24.

[0017] The gear group 26 includes a speed reduction device, a differential device, etc. The speed reduction device is mechanically connected to the engine 22 and the motor 24. The speed reduction device amplifies the torque output by the engine 22 and the motor 24. The differential device is mechanically connected to the engine 22 and the motor 24 via the speed reduction device. The differential device is connected to a pair of drive wheels (not shown) via a pair of drive shafts 28. Thus, the torque output by the engine 22 and the motor 24 is amplified by the speed reduction device and then distributed to the pair of drive shafts 28 by the differential device. The vehicle can travel by driving the pair of drive wheels with the torque distributed to the pair of drive wheels.

[0018] The electric oil pump 30 is attached to the lower part of the casing 4. The electric oil pump 30 circulates oil along the oil circulation path in the casing 4. Specifically, the electric oil pump 30 sucks the oil staying in the lower part of the casing 4 and pumps it to each part of the casing 4 via the oil circulation path in the casing 4.

[0019] Referring to FIGS. 2 and 3, the structure of the electric oil pump 30 will be described. As shown in FIG. 2, the electric oil pump 30 includes a pump rotor 32, a pump motor 34, and a control board 36. The pump rotor 32 is mechanically connected to the pump motor 34. The pump motor 34 is a small electric motor and is the prime mover of the electric oil pump 30. The pump motor 34 rotationally drives the pump rotor 32. When the pump rotor 32 of the electric oil pump 30 rotates, the oil staying in the casing 4 is sucked into the electric oil pump 30. The control board 36 drives the electric oil pump 30 based on a command input from, for example, a higher-level control device (for example, the control device 10).

[0020] In addition, an oil reservoir portion 38 for storing oil branched from the oil circulation path in the casing 4 is provided inside the electric oil pump 30. In a modification, the oil reservoir portion 38 may not be provided inside the electric oil pump 30 and may be provided, for example, near the electric oil pump 30.

[0021] Here, referring to FIG. 4, the oil flow path will be described. As shown in FIG. 4, the oil flow path includes an oil circulation path (i.e., lubrication path) provided in the casing 4 and an oil reservoir path branched from the oil circulation path. The oil staying at the lower part of the casing 4 is supplied to the switching valve via a strainer by the drive of the electric oil pump 30. The switching valve is provided at the branch point between the lubrication path and the oil reservoir path. The switching valve adjusts the amount of oil flowing into the lubrication path and the amount of oil flowing into the oil reservoir path.

[0022] Normally, the entire amount of oil supplied to the switching valve is supplied to the lubrication path. The oil supplied to the lubrication path is used, for example, as lubricating oil during the drive of the engine 22 etc., and as oil for cooling the engine 22, the motor 24 etc. The oil flowing through the lubrication path stays again at the lower part of the casing 4.

[0023] Also, a switching valve is provided on the downstream side of the oil reservoir portion 38. The switching valve adjusts the amount of oil discharged from the oil reservoir portion 38. The oil discharged from the oil reservoir portion 38 stays again at the lower part of the casing 4.

[0024] The control device 10 controls the above switching valve according to the rotational speed of the engine 22. Specifically, the control device 10 controls the operation of the switching valve between the case where the engine 22 operates in a specific rotational speed range and the case where it does not, thereby changing the amount of oil stored in the oil reservoir portion 38. In one example, the control device 10 controls the switching valve provided at the branch point between the lubrication path and the oil reservoir path, and changes (i.e., increases) the amount of oil stored in the oil reservoir portion 38 by increasing the flow rate of the oil flowing into the oil reservoir path. Also, in another example, the control device 10 controls the switching valve provided on the downstream side of the oil reservoir portion 38, and changes (i.e., decreases) the amount of oil stored in the oil reservoir portion 38 by discharging oil from the oil reservoir portion 38.

[0025] When engine 22 rotates, vibrations are generated. The frequency of these vibrations depends on the rotational speed of engine 22. If the frequency of the vibrations generated by the operation of engine 22 approximately matches the resonant frequency of electric oil pump 30, resonance occurs in electric oil pump 30, causing the vibration of electric oil pump 30 to become excessively large. The specific rotational speed range of engine 22 described above is the rotational speed range that causes resonance in electric oil pump 30.

[0026] As described above, according to the configuration of this embodiment, the control device 10 changes the amount of oil stored in the oil reservoir 38 when the engine 22 is operating in a specific rotational speed range. Generally, the resonant frequency of the electric oil pump 30 is determined by the structure, shape, material, etc. of the electric oil pump 30. The resonant frequency of the electric oil pump 30 changes as the amount of oil stored in the oil reservoir 38 changes. Therefore, even when the engine 22 rotates in a specific rotational speed range, resonance in the electric oil pump 30 is suppressed. Consequently, excessive vibration in the electric oil pump 30 is suppressed.

[0027] (Second example) Next, a second embodiment will be described with reference to Figure 5. In the second embodiment, the rotational speed of the electric oil pump 30 is changed in order to suppress resonance in the electric oil pump 30. The drive unit 2 of the second embodiment does not need to have an oil reservoir 38. Other aspects are the same as those of the drive unit 2 of the first embodiment.

[0028] As described above, when the engine 22 operates in a specific rotational speed range, resonance occurs in the electric oil pump 30. The dashed line graph in Figure 5 shows the relationship between the frequency of vibrations caused by the rotation of the engine 22 and the magnitude of the vibrations of the electric oil pump 30 at that time. As shown by the dashed line in Figure 5, when the frequency of vibrations caused by the rotation of the engine 22 approaches the resonant frequency FR of the electric oil pump 30, resonance occurs in the electric oil pump 30, and the vibrations of the electric oil pump 30 become significantly larger. In other words, when the engine 22 operates in a specific rotational speed range, the vibrations of the electric oil pump 30 become excessively large.

[0029] Therefore, in the drive unit 2 of the second embodiment, the control device 10 changes the rotational speed of the electric oil pump 30 according to the rotational speed of the engine 22. Specifically, the control device 10 changes the rotational speed of the electric oil pump 30 between when the engine 22 is operating in a specific rotational speed range and when it is not. Vibration is also generated when the electric oil pump 30 rotates. The frequency of vibration due to the rotation of the electric oil pump 30 depends on the rotational speed of the electric oil pump 30. In this embodiment, the control device 10 changes the rotational speed of the electric oil pump 30 so that it generates vibrations in the electric oil pump 30 that are in opposite phase to the vibrations caused by the operation of the engine 22. The solid line graph in Figure 5 shows the relationship between the frequency of vibration generated by the rotation of the engine 22 and the magnitude of the vibration of the electric oil pump 30 when the rotational speed of the electric oil pump 30 is changed as described above. As shown in the solid line graph of Figure 5, even when the frequency of vibrations generated by the rotation of the engine 22 approaches the resonant frequency FR of the electric oil pump 30, the magnitude of vibrations in the electric oil pump 30 is suppressed to become excessively large, depending on the operating speed range of the engine 22. This is because the vibrations caused by the operation of the engine 22 and the vibrations caused by the operation of the electric oil pump 30 interfere with each other in a way that cancels each other out. Therefore, the occurrence of resonance caused by the operation of the engine 22 is suppressed in the electric oil pump 30. Consequently, the occurrence of excessive vibrations in the electric oil pump 30 is suppressed. The combination of the control device 10 and the control board 36 is an example of the "pump control device" of this technology.

[0030] The specific examples of the technology disclosed in this specification have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples described above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of Symbols]

[0031] 2: Drive unit, 4: Casing, 10: Control unit, 22: Engine, 24: Motor, 26: Gear group, 28: Drive shaft, 30: Electric oil pump

Claims

1. A vehicle drive system, The drivetrain, including the engine, A casing housing the aforementioned drive system, An oil circulation path provided in the casing, An electric oil pump that circulates oil along the aforementioned oil circulation path, An oil reservoir is provided inside or near the electric oil pump, and branches off from the oil circulation path to store the oil, A control device for adjusting the amount of oil stored in the oil reservoir, Equipped with, The control device is a drive device that changes the amount of oil stored in the oil reservoir according to the rotational speed of the engine.

2. The drive device according to claim 1, wherein the control device changes the amount of oil stored in the oil reservoir depending on whether the engine is operating in a specific rotational speed range or not.

3. The system further comprises at least one valve for connecting and disconnecting the electric oil pump and the oil reservoir, The drive device according to claim 1 or 2, wherein the control device changes the amount of oil stored in the oil reservoir by controlling the operation of at least one valve.

4. A vehicle drive system, The drivetrain, including the engine, A casing housing the aforementioned drive system, An oil circulation path provided in the casing, An electric oil pump that circulates oil along the aforementioned oil circulation path, A pump control device that controls the rotation speed of the electric oil pump, Equipped with, The pump control device is a drive device that changes the rotational speed of the electric oil pump according to the rotational speed of the engine.

5. The drive device according to claim 4, wherein the pump control device changes the rotational speed of the electric oil pump depending on whether the engine is operating in a specific rotational speed range or not.

Images