Hydraulic circuit for hybrid vehicles

Abstract

To achieve low cost and downsizing while decreasing the number of components.SOLUTION: A hydraulic circuit for a hybrid vehicle comprises: an internal combustion engine; an electric generator to which output of the internal combustion engine is transmitted; and a direct clutch which is arranged between the internal combustion engine and the electric generator and connects / disconnects the output of the internal combustion engine with / from a drive shaft. The hydraulic circuit for the hybrid vehicle includes a solenoid valve which switches output pressure applied to the direct clutch based on a given line pressure. When the direct clutch is in a disengagement state so that the output of the internal combustion engine is not transmitted to the drive shaft, the hydraulic circuit sets the output pressure to be a first pressure. When the direct clutch is in an engagement state so that the output of the internal combustion engine is transmitted to the drive shaft, the hydraulic circuit sets the output pressure to be a second pressure that is higher than the first pressure. When abnormality occurs in the hydraulic circuit, the hydraulic circuit switches the line pressure to be the first pressure or less.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a hydraulic circuit for a hybrid vehicle. [Background technology]

[0002] The direct clutch of a hybrid vehicle is connected and disconnected by hydraulic pressure from a hydraulic circuit. The hydraulic circuit generates low hydraulic pressure to disengage the direct clutch during series running, when the output of the internal combustion engine is not transmitted to the drive shaft. The hydraulic circuit generates high hydraulic pressure to engage the direct clutch during direct running, when the output of the internal combustion engine is transmitted to the drive shaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2009 / 128288 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the event of an abnormality, the hydraulic circuit must forcibly cut off the generation of high hydraulic pressure so that the direct clutch does not remain constantly engaged. For this reason, conventionally, a hydraulic circuit for connecting and disconnecting the direct clutch has, for example, two relay valve circuits, and when an abnormality occurs in one relay valve circuit, the generation of hydraulic pressure is cut off by the other relay valve circuit.

[0005] However, a hydraulic circuit having two such relay valve circuits increases the number of parts and the circuit size, and furthermore, the hydraulic circuit requires the setting and control of the two relay valve circuits, resulting in high costs.

[0006] The present invention has been made in view of the above, and an object of the present invention is to provide a hydraulic circuit for a hybrid vehicle that can reduce the number of parts, thereby achieving cost reduction and size reduction. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, a hydraulic circuit for a hybrid vehicle according to the present invention is a hydraulic circuit for a hybrid vehicle including an internal combustion engine, a generator to which an output of the internal combustion engine is transmitted, and a direct clutch provided between the internal combustion engine and the generator for connecting and disconnecting the output of the internal combustion engine to a drive shaft, the hydraulic circuit having a solenoid valve for switching an output pressure to be applied to the direct clutch based on a given line pressure, the hydraulic circuit sets the output pressure to a first pressure when the direct clutch is in a disengaged state so as not to transmit the output of the internal combustion engine to the drive shaft, sets the output pressure to a second pressure higher than the first pressure when the direct clutch is in an engaged state so as to transmit the output of the internal combustion engine to the drive shaft, and Before The pressure is switched to below the first pressure. Effect of the Invention

[0008] According to the present invention, the number of parts can be reduced, thereby achieving cost reduction and size reduction. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the configuration of a hybrid vehicle. [Diagram 2] FIG. 2 is a diagram showing the configuration of a hydraulic circuit. [Diagram 3] FIG. 3 is a flowchart showing the flow of control of the hydraulic circuit by the electronic control unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments will be described with reference to the drawings.

[0011] 1 is a diagram showing the configuration of a hybrid vehicle 10 according to an embodiment. The hybrid vehicle 10 includes a drive shaft 20, an internal combustion engine 22, a battery 24, an inverter 26, a motor generator 28, a direct clutch 30, a hydraulic circuit 32, and an electronic control unit 34.

[0012] Wheels are provided at both ends of the drive shaft 20. When a driving force is applied to the drive shaft 20, the drive shaft 20 rotates about its axial direction, thereby causing the hybrid vehicle 10 to travel.

[0013] The internal combustion engine 22 burns fuel to generate rotational energy. The battery 24 stores electric power. The inverter 26 converts electric power between the battery 24 and the motor generator 28.

[0014] The motor generator 28 has a rotating shaft connected to the drive shaft 20 via a transmission, a differential, etc. The motor generator 28 operates as a generator or an electric motor. When the motor generator 28 operates as a generator, it generates electric power from the rotational energy of the rotating shaft and stores the generated electric power in the battery 24 via the inverter 26. When the motor generator 28 operates as an electric motor, it rotates the rotating shaft with the electric power received from the battery 24 via the inverter 26.

[0015] The direct clutch 30 is provided between the internal combustion engine 22 and the motor generator 28. The direct clutch 30 connects and disconnects the rotating shaft of the internal combustion engine 22 and the rotating shaft of the motor generator 28. Specifically, the direct clutch 30 switches between an engaged state and a disengaged state. In the engaged state, the direct clutch 30 transmits the output of the internal combustion engine 22 to the drive shaft 20. On the other hand, in the disengaged state, the direct clutch 30 does not transmit the output of the internal combustion engine 22 to the drive shaft 20. Note that the direct clutch 30 connects the rotating shaft of the internal combustion engine 22 and the rotating shaft of the motor generator 28, so that the output from the internal combustion engine 22 is transmitted to the motor generator 28. Thus, the direct clutch 30 can connect and disconnect the output of the internal combustion engine 22 to and from the drive shaft 20.

[0016] By disengaging the direct clutch 30, the hybrid vehicle 10 performs series running, in which the output of the internal combustion engine 22 is not transmitted to the drive shaft 20, but the output of the battery 24 is used to run the vehicle. By engaging the direct clutch 30, the hybrid vehicle 10 performs direct running, in which the output of the internal combustion engine 22 is transmitted to the drive shaft 20. During direct running, the hybrid vehicle 10 can operate the motor generator 28 as a generator to charge the battery 24 with electricity.

[0017] The hydraulic circuit 32 operates the direct clutch 30 by hydraulic pressure to switch the direct clutch 30 between a disengaged state and an engaged state. Specifically, when the direct clutch 30 is in a disengaged state and the output of the internal combustion engine 22 is not transmitted to the drive shaft 20 (during series running), the hydraulic circuit 32 sets the output pressure provided to the direct clutch 30 to a first pressure. When the output pressure provided from the hydraulic circuit 32 is the first pressure, the direct clutch 30 is not operated and is in a disengaged state. Furthermore, when the direct clutch 30 is in an engaged state and the output of the internal combustion engine 22 is transmitted to the drive shaft 20 (during direct running), the hydraulic circuit 32 sets the output pressure provided to the direct clutch 30 to a second pressure higher than the first pressure. When the output pressure provided from the hydraulic circuit 32 is the second pressure, the direct clutch 30 is operated and is in an engaged state.

[0018] In addition, the hydraulic circuit 32 normally keeps the line pressure, which is the hydraulic pressure of the internal piping, in a high pressure state. The high pressure state is a pressure at which the hydraulic circuit 32 can generate at least the second pressure.

[0019] Moreover, the hydraulic circuit 32 switches the line pressure to a low pressure state in the event of an abnormality. The low pressure state is a state where the hydraulic circuit 32 cannot generate a pressure for operating the direct clutch 30 to be in an engaged state, for example, a state below the first pressure. For example, the hydraulic circuit 32 switches the line pressure from a high pressure state to a low pressure state when an abnormality occurs inside the hydraulic circuit 32. For example, in the event of switching from direct running to series running, the hydraulic circuit 32 switches the line pressure from a high pressure state to a low pressure state when the direct clutch 30 does not become in a disengaged state despite being controlled to disengage the engaged direct clutch 30. As a result, in the event of an abnormality, the hydraulic circuit 32 can switch the output pressure to a pressure that disengages the direct clutch 30, forcibly disengaging the direct clutch 30.

[0020] The electronic control unit 34 is a semiconductor circuit or a module that is configured with a processor or a dedicated circuit. The electronic control unit 34 controls various devices provided in the hybrid vehicle 10.

[0021] In this embodiment, the electronic control unit 34 controls the hydraulic circuit 32 as one of various devices included in the hybrid vehicle 10. When the hybrid vehicle 10 is made to run in series, the electronic control unit 34 controls the hydraulic circuit 32 to output an output pressure of a first pressure from the hydraulic circuit 32. When the hybrid vehicle 10 is made to run in direct current, the electronic control unit 34 controls the hydraulic circuit 32 to output an output pressure of a second pressure from the hydraulic circuit 32.

[0022] Furthermore, the electronic control unit 34 judges whether or not an abnormality has occurred in the hydraulic circuit 32. For example, when the electronic control unit 34 controls the engaged direct clutch 30 to be disengaged in order to switch from direct driving to series driving, but the direct clutch 30 does not become disengaged, the electronic control unit 34 judges that an abnormality has occurred in the hydraulic circuit 32. When the electronic control unit 34 judges that an abnormality has occurred in the hydraulic circuit 32, it controls the hydraulic circuit 32 to change the line pressure from a high pressure state to a low pressure state. In this way, the electronic control unit 34 can disengage the direct clutch 30 when an abnormality has occurred in the hydraulic circuit 32.

[0023] 2 is a diagram showing the configuration of the hydraulic circuit 32. The hydraulic circuit 32 has a hydraulic pump 42, a solenoid valve 44, an on-off solenoid valve 46, and a regulator valve 48.

[0024] The hydraulic pump 42 has a discharge port 42a connected to a first pipe 52. The hydraulic pump 42 is connected to a solenoid valve 44 via the first pipe 52. The hydraulic pump 42 delivers oil to the first pipe 52 at a predetermined flow rate.

[0025] The solenoid valve 44 has an input port 44a connected to the first pipe 52. The solenoid valve 44 has an output port 44b connected to the output pipe 54. The solenoid valve 44 controls the flow rate of oil flowing from the input port 44a to the output port 44b by electromagnetic force. Such a solenoid valve 44 can change the pressure (output pressure) of the output pipe 54 within a range equal to or less than the hydraulic pressure (line pressure) of the first pipe 52. The output pipe 54 connected to the output port 44b of the solenoid valve 44 is connected to the direct clutch 30. As a result, the direct clutch 30 can be switched between an engaged state and a disengaged state according to the pressure (output pressure) of the output pipe 54.

[0026] The on-off solenoid valve 46 has an input port 46a connected to the first pipe 52. The on-off solenoid valve 46 has an output port 46b connected to the second pipe 56. The on-off solenoid valve 46 switches between connecting and disconnecting the input port 46a and the output port 46b by electromagnetic force.

[0027] When the on-off solenoid valve 46 is in the on state, it connects between the input port 46a and the output port 46b. Therefore, when the on-off solenoid valve 46 is in the on state, it can make the pressure (signal pressure) of the second pipe 56 equal to the pressure (line pressure) of the first pipe 52.

[0028] When the on-off solenoid valve 46 is in the off state, it disconnects the input port 46a from the output port 46b. Therefore, when the on-off solenoid valve 46 is in the off state, it can make the pressure (signal pressure) in the second pipe 56 approximately zero.

[0029] The regulator valve 48 has an input port 48a and a feedback port 48b connected to the first pipe 52. In addition, the regulator valve 48 has a signal pressure input port 48c connected to the output port 46b of the on-off solenoid valve 46 via a second pipe 56.

[0030] The regulator valve 48 includes a spring therein. The regulator valve 48 adjusts the pressure (line pressure) in the first pipe 52 to be constant at a predetermined value in response to the sum of the pressure (signal pressure) in the second pipe 56 applied to the signal pressure input port 48c and the pressure of the spring.

[0031] When the on-off solenoid valve 46 is in the on state, the regulator valve 48 applies high pressure to the signal pressure input port 48c, so that the pressure (line pressure) of the first pipe 52 can be in a high pressure state. Also, when the on-off solenoid valve 46 is in the off state, the regulator valve 48 applies no high pressure to the signal pressure input port 48c, so that the pressure (line pressure) of the first pipe 52 can be in a low pressure state.

[0032] Here, the high line pressure when the on-off solenoid valve 46 is in the on state is a pressure that is high enough to switch the direct clutch 30 to the engaged state. On the other hand, the low line pressure when the on-off solenoid valve 46 is in the off state is a pressure that is low enough not to switch the direct clutch 30 to the engaged state.

[0033] Then, in normal times when no abnormality occurs in the hydraulic circuit 32, the on-off solenoid valve 36 is turned on by control by the electronic control unit 34. Therefore, in normal times, the on-off solenoid valve 46 can set the line pressure, which is the pressure in the first pipe 52, to a high pressure state by control by the electronic control unit 34.

[0034] Furthermore, in the event of an abnormality in the hydraulic circuit 32, the on-off solenoid valve 46 is turned off under the control of the electronic control unit 34. Therefore, in the event of an abnormality, the on-off solenoid valve 46 can set the line pressure, which is the pressure in the first pipe 52, to a low pressure state under the control of the electronic control unit 34.

[0035] When the direct clutch 30 is in a disengaged state and the output of the internal combustion engine 22 is not transmitted to the drive shaft 20 (during series running), the hydraulic circuit 32 as described above sets the output pressure output from the solenoid valve 44 to a first pressure based on the high line pressure through control by the electronic control unit 34. This allows the hydraulic circuit 32 to set the output pressure applied to the direct clutch 30 to the first pressure during series running. Therefore, during series running, the hydraulic circuit 32 can set the direct clutch 30 to a disengaged state without operating it.

[0036] Furthermore, when the direct clutch 30 is engaged to transmit the output of the internal combustion engine 22 to the drive shaft 20 (during direct running), the hydraulic circuit 32 sets the output pressure output from the solenoid valve 44 to a second pressure higher than the first pressure based on the high line pressure through control by the electronic control unit 34. This allows the hydraulic circuit 32 to set the output pressure applied to the direct clutch 30 to the second pressure during direct running. Therefore, during direct running, the hydraulic circuit 32 can operate the direct clutch 30 to bring it into an engaged state.

[0037] Moreover, in the event of an abnormality, the hydraulic circuit 32 as described above can switch the line pressure from a high pressure state to a low pressure state under the control of the electronic control unit 34. As a result, in the event of an abnormality, the hydraulic circuit 32 can switch the line pressure to a low pressure state at which the direct clutch 30 cannot be operated, thereby reliably putting the direct clutch 30 into a disengaged state.

[0038] 3 is a flowchart showing the flow of control of the hydraulic circuit 32 by the electronic control unit 34. The electronic control unit 34 controls the on / off solenoid valve 46 of the hydraulic circuit 32, for example, according to the flow shown in FIG.

[0039] First, in S11, when the hybrid vehicle 10 starts to operate, the electronic control unit 34 starts the operation of the hydraulic pump 42 and controls the on / off solenoid valve 46 to the on state. This allows the electronic control unit 34 to set the line pressure of the hydraulic circuit 32 to a high pressure state. With the line pressure of the hydraulic circuit 32 in a high pressure state, the electronic control unit 34 can switch between series running and direct running by controlling the solenoid valve 44.

[0040] Next, in S12, the electronic control unit 34 determines whether or not an abnormality has occurred in the hydraulic circuit 32 during operation of the hybrid vehicle 10. For example, when the direct clutch 30 does not become disengaged despite the electronic control unit 34 controlling the direct clutch 30 from an engaged state to become disengaged, the electronic control unit 34 determines that an abnormality has occurred in the hydraulic circuit 32. Also, the electronic control unit 34 may determine that an abnormality has occurred in the hydraulic circuit 32 when, for example, an abnormality in the solenoid valve 44 is detected by another method.

[0041] If no abnormality has occurred in the hydraulic circuit 32 (No in S12), the electronic control unit 34 returns to S12 and repeats the process of S12 until the end of operation of the hybrid vehicle 10. If the electronic control unit 34 determines that an abnormality has occurred in the hydraulic circuit 32 (Yes in S12), the electronic control unit 34 advances the process to S13.

[0042] In S13, the electronic control unit 34 controls the on / off solenoid valve 46 to the off state. This allows the electronic control unit 34 to switch the line pressure of the hydraulic circuit 32 from a high pressure state to a low pressure state. When the line pressure is in a low pressure state, the hydraulic circuit 32 outputs a sufficiently low output pressure that cannot operate the direct clutch 30. This allows the electronic control unit 34 to forcibly disengage the direct clutch 30 when an abnormality occurs in the hydraulic circuit 32.

[0043] When the electronic control unit 34 finishes the process of S13, it ends this flow.

[0044] The hydraulic circuit 32 of the hybrid vehicle 10 according to the embodiment described above can forcibly disengage the direct clutch 30 when an abnormality occurs by switching the on / off solenoid valve 46. This allows the hydraulic circuit 32 of the hybrid vehicle 10 according to the embodiment to achieve a fail-safe function when an abnormality occurs with a small number of parts. With such a hydraulic circuit 32 of the hybrid vehicle 10, the number of parts can be reduced, resulting in lower costs and a smaller size.

[0045] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. Various modifications can be made to the embodiments. [Explanation of symbols]

[0046] 10 Hybrid vehicle, 20 Drive shaft, 22 Internal combustion engine, 24 Battery, 26 Inverter, 28 Motor generator, 30 Direct clutch, 32 Hydraulic circuit, 34 Electronic control unit, 42 Hydraulic pump, 44 Solenoid valve, 46 On-off solenoid valve, 48 Regulator valve, 52 First pipe, 54 Output pipe, 56 Second pipe

Claims

1. An internal combustion engine; a generator to which the output of the internal combustion engine is transmitted; a direct clutch provided between the internal combustion engine and the generator for connecting and disconnecting an output of the internal combustion engine to and from a drive shaft; A hydraulic circuit for a hybrid vehicle comprising: a solenoid valve for switching the output pressure to be applied to the direct clutch based on a given line pressure; The hydraulic circuit includes: when the direct clutch is in a disengaged state and output from the internal combustion engine is not transmitted to the drive shaft, the output pressure is set to a first pressure; When the direct clutch is in an engaged state to transmit the output of the internal combustion engine to the drive shaft, the output pressure is set to a second pressure higher than the first pressure, When an abnormality occurs in the hydraulic circuit, the line pressure is changed to a value equal to or lower than the first pressure. Hydraulic circuit of a hybrid vehicle.

2. The hydraulic circuit includes: a regulator valve that adjusts the line pressure to a constant level; an on-off solenoid valve that switches between an on state in which the line pressure is applied to a signal pressure input port of the regulator valve and an off state in which the line pressure is not applied to the signal pressure input port of the regulator valve; and The on-off solenoid valve is in the on state when no abnormality occurs in the hydraulic circuit, and is in the off state when an abnormality occurs in the hydraulic circuit.

2. A hydraulic circuit for a hybrid vehicle according to claim 1.

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