JP7677130B2 - Hydraulic control device for automatic transmission - Google Patents

Description

The present invention relates to a hydraulic control device for an automatic transmission.

Patent Document 1 describes an example of a hydraulic control device that sets a line pressure command value based on the output torque of the engine and controls the line pressure by adjusting the opening of a solenoid valve for adjusting the line pressure based on the line pressure command value. The line pressure is the hydraulic pressure that is the basis for the hydraulic pressure supplied to hydraulic actuators of an automatic transmission, etc.

Japanese Patent Application Publication No. 8-278212

The oil passage for the oil discharged from the oil pump has an oil passage leading to the hydraulic actuator and an oil passage leading to the oil cooler. That is, part of the oil discharged from the oil pump is supplied to the hydraulic circuit, and the rest is supplied to the oil cooler. By passing the oil through the oil cooler, the temperature of the oil circulating in the hydraulic circuit of the automatic transmission is prevented from becoming too high.

In this hydraulic circuit, the greater the opening of the solenoid valve, the greater the amount of oil discharged from the oil pump that goes to the hydraulic actuator, increasing the line pressure, while the less oil goes to the oil cooler. Therefore, when the solenoid valve is fully open, the amount of oil going to the oil cooler is significantly reduced, making it easier for the oil temperature to rise.

As described above, the hydraulic control device sets the line pressure command value based on the engine output torque. Therefore, a large value may be set as the line pressure command value when the oil pump discharges a relatively small amount of oil, for example, due to a low engine speed. In such a case, the opening of the electromagnetic valve is increased to increase the line pressure toward the line pressure command value. However, if the line pressure command value is too high compared to the oil pump discharge, the line pressure may not reach the line pressure command value even if the electromagnetic valve is fully opened. In such a case, the electromagnetic valve is fully opened, and a state in which almost no oil is supplied to the oil cooler continues. As a result, the oil temperature may become too high.

The hydraulic control device for an automatic transmission to solve the above problem is applied to an automatic transmission that includes an oil pump that discharges oil by driving a drive source, a hydraulic actuator, an oil cooler that cools the oil, and a line pressure adjustment valve that distributes the oil discharged from the oil pump to the hydraulic actuator and the oil that heads to the oil cooler, and is configured so that the greater the opening of the line pressure adjustment valve, the greater the amount of oil headed for the hydraulic actuator, and the higher the line pressure, which is the hydraulic pressure supplied to the hydraulic actuator. This hydraulic control device includes a control unit that controls the opening of the line pressure adjustment valve based on a line pressure indication value that is an indication value of the line pressure. The control unit executes a setting process that sets a smaller value as the upper limit of the line pressure indication value as the rotation speed of the drive source decreases.

According to the above configuration, when the rotation speed of the drive source is relatively low and therefore the oil discharge amount of the oil pump is relatively small, the line pressure command value is unlikely to become large. As a result, it is possible to suppress the occurrence of an event in which the line pressure cannot be increased to the line pressure command value even if the opening degree of the line pressure adjustment valve is increased. In other words, it is possible to suppress the long-lasting event in which the line pressure adjustment valve is fully open and almost no oil is supplied to the oil cooler. Therefore, it is possible to suppress the oil temperature from becoming too high.

FIG. 1 is a schematic diagram showing the configuration of a power transmission system of a vehicle equipped with a hydraulic control device according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing the hydraulic control device and a hydraulic circuit of an automatic transmission. FIG. 3 is a flowchart illustrating a processing routine executed by the CPU of the hydraulic control device. FIG. 4 is a map showing the relationship between the upper limit of the line pressure command value and the amount of oil discharged from the oil pump.

An embodiment of a hydraulic control device for an automatic transmission will be described below with reference to FIGS.
FIG. 1 illustrates a power transmission system of a vehicle 10 on which a hydraulic control device 50 according to the present embodiment is mounted.

<Power transmission system of vehicle 10>
The vehicle 10 includes an engine 11, an automatic transmission 12, a propeller shaft 14, a differential 15, and a plurality of drive wheels 16. The automatic transmission 12 is a hydraulically driven multi-speed transmission, and includes a hydraulic circuit 13. Torque output from the automatic transmission 12 is transmitted to the plurality of drive wheels 16 via the propeller shaft 14 and the differential 15.

<Hydraulic circuit 13>
As shown in Fig. 2, the hydraulic circuit 13 includes an oil pan 21, an oil pump 22, a pressure regulating mechanism 23, a hydraulic actuator 24, and an oil cooler 25. The oil pan 21 stores oil circulating through the hydraulic circuit 13. The oil pump 22 operates by receiving rotation input from the engine 11 to the automatic transmission 12. The oil pump 22 pumps up oil in the oil pan 21 in response to its operation, and pressurizes and discharges the oil. In this embodiment, the engine 11 corresponds to the drive source of the oil pump 22. The oil discharged from the oil pump 22 is distributed to the hydraulic actuator 24 and the oil cooler 25.

The hydraulic circuit 13 includes a first oil passage 26 that supplies the oil discharged from the oil pump 22 to the hydraulic actuator 24, and a second oil passage 27 that branches off from the first oil passage 26. The second oil passage 27 is an oil passage that supplies the oil discharged from the oil pump 22 to the oil cooler 25.

The pressure regulating mechanism 23 is disposed on the hydraulic actuator 24 side of the branch point of the first oil passage 26 with the second oil passage 27. The pressure regulating mechanism 23 operates to regulate the line pressure, which is the hydraulic pressure supplied to the hydraulic actuator 24. The pressure regulating mechanism 23 has an electromagnetic line pressure regulating valve 23a. The opening degree of the line pressure regulating valve 23a regulates the distribution ratio between the amount of oil discharged from the oil pump 22 that is directed to the hydraulic actuator 24 and the amount of oil that is directed to the oil cooler 25. In other words, the higher the opening degree of the line pressure regulating valve 23a, the more of the oil discharged from the oil pump 22 that is directed to the hydraulic actuator 24, and the higher the line pressure. On the other hand, the higher the opening degree, the less of the oil discharged from the oil pump 22 that is directed to the oil cooler 25.

The hydraulic actuator 24 adjusts the supply of oil to the parts of the automatic transmission 12 that require oil supply. The parts that require oil supply are, for example, a torque converter and friction engagement elements such as clutches and brakes. The hydraulic actuator 24 has, for example, multiple solenoid valves.

The oil cooler 25 cools the oil circulating through the hydraulic circuit 13. Specifically, the oil cooler 25 cools the oil that flows into the oil cooler 25 via the second oil passage 27, and returns the cooled oil to the oil pan 21.

The hydraulic circuit 13 is provided with a hydraulic sensor 31 that detects the line pressure P. A detection signal from the hydraulic sensor 31 is output to the hydraulic control device 50.
<Hydraulic control device 50>
The hydraulic control device 50 receives detection signals from a plurality of sensors, including an oil pressure sensor 31. The hydraulic control device 50 detects a line pressure P based on the detection signal from the oil pressure sensor 31. An example of a sensor other than the oil pressure sensor 31 is a crank angle sensor 32. The hydraulic control device 50 detects an engine speed Ne based on the detection signal from the crank angle sensor 32. This engine speed Ne corresponds to the "speed of the drive source."

The hydraulic control device 50 includes a CPU 51 and a memory 52. The memory 52 stores a control program executed by the CPU 51. The CPU 51 executes the control program, whereby the CPU 51 controls the line pressure adjustment valve 23a and the hydraulic actuator 24. Therefore, in this embodiment, the CPU 51 corresponds to the "control unit."

<Control process of line pressure P>
3 and 4, a control process for the line pressure P will be described. The process routine shown in Fig. 3 is executed by the CPU 51 at each predetermined control cycle in order to control the opening degree of the line pressure adjusting valve 23a.

As shown in FIG. 3, in step S11 of this processing routine, the CPU 51 acquires the required line pressure value PRq, which is the required value for the line pressure. The required line pressure value PRq is determined by the vehicle speed at that time, the gear position of the automatic transmission 12, etc.

In the next step S13, the CPU 51 sets an upper limit PL of the line pressure command value. The line pressure command value PTr is a command value for the line pressure P and is used to control the opening degree of the line pressure adjustment valve 23a. In this embodiment, the CPU 51 sets the upper limit PL using the map shown in FIG. 4.

Figure 4 shows a map showing the relationship between the upper limit PL of the line pressure indication value and the oil discharge amount of the oil pump 22. In this map, the higher the oil discharge amount, the higher the upper limit PL. The higher the engine speed Ne, the higher the oil discharge amount. Therefore, the CPU 51 estimates the oil discharge amount based on the engine speed Ne. The CPU 51 then obtains a value corresponding to this estimated value of the oil discharge amount as the upper limit PL from the map shown in Figure 4. This allows the CPU 51 to set the upper limit PL. Therefore, in this embodiment, the process of step S13 corresponds to a "setting process" that sets a smaller value as the upper limit PL as the engine speed Ne is smaller.

Returning to FIG. 3, when the setting of the upper limit PL is completed, the CPU 51 proceeds to step S15. In step S15, the CPU 51 sets the smaller of the line pressure request value PRq and the upper limit PL as the line pressure command value PTr.

In the next step S17, the CPU 51 controls the opening degree of the line pressure adjustment valve 23a based on the line pressure command value PTr. Specifically, the CPU 51 increases the opening degree of the line pressure adjustment valve 23a when the line pressure P is lower than the line pressure command value PTr, and decreases the opening degree of the line pressure adjustment valve 23a when the line pressure P is higher than the line pressure command value PTr. After performing this valve control, the CPU 51 temporarily ends this processing routine.

<Actions and Effects of the Present Embodiment>
When the engine speed Ne is relatively low, the oil discharge amount of the oil pump 22 is relatively small, i.e., the oil discharge pressure of the oil pump 22 is relatively low, so it is difficult to increase the line pressure P. Therefore, in this embodiment, when the engine speed Ne is low, it is difficult to set a large value as the line pressure command value PTr compared to when the engine speed Ne is high.

Specifically, the lower the engine speed Ne, the smaller the upper limit PL of the line pressure command value is set. The line pressure command value PTr is then set so as not to exceed the upper limit PL. As a result, the lower the engine speed Ne, the less likely the line pressure command value PTr is to become large.

In this embodiment, the opening of the line pressure adjustment valve 23a is controlled based on the line pressure command value PTr set in this manner. As a result, the opening of the line pressure adjustment valve 23a can be prevented from becoming fully open, and thus the situation in which almost no oil is supplied to the oil cooler 25 can be prevented from continuing for a long period of time. In other words, the oil cooler 25 can be prevented from no longer cooling the oil. Therefore, the temperature of the oil circulating through the hydraulic circuit 13 can be prevented from becoming too high.

<Example of change>
The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

The driving source of the oil pump 22 does not have to be the engine 11. For example, the oil pump 22 may be a pump driven by an electric motor. In this case, the vehicle on which the hydraulic control device is mounted may be a hybrid vehicle equipped with the engine 11 and an electric motor as power sources, or a vehicle that does not have the engine 11 as a power source but has an electric motor.

- The automatic transmission to which the hydraulic control device 50 is applied does not have to be a multi-speed transmission as long as it has an oil pump 22. For example, the automatic transmission may be a continuously variable transmission.

The hydraulic control device 50 is not limited to being equipped with the CPU 51 and the memory 52 and executing software processing. In other words, the hydraulic control device 50 may have any one of the following configurations (a) to (c).
(a) The hydraulic control device 50 includes one or more processors that execute various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program codes or instructions configured to cause the CPU to execute processes. Memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or special-purpose computer.
(b) The hydraulic control device 50 includes one or more dedicated hardware circuits that execute various processes. Examples of the dedicated hardware circuits include application specific integrated circuits, i.e., ASIC and FPGA. Note that ASIC is an abbreviation for "Application Specific Integrated Circuit" and FPGA is an abbreviation for "Field Programmable Gate Array."
(c) The hydraulic control device 50 includes a processor that executes some of the various processes in accordance with a computer program, and a dedicated hardware circuit that executes the remaining processes among the various processes.

REFERENCE SIGNS LIST 11 engine 12 automatic transmission 13 hydraulic circuit 22 oil pump 23a line pressure adjusting valve 24 hydraulic actuator 25 oil cooler 50 hydraulic control device 51 CPU

Claims (1)

The present invention is applied to an automatic transmission including an oil pump that discharges oil by driving a drive source, a hydraulic actuator, an oil cooler that cools the oil, and a line pressure regulating valve that distributes the oil discharged from the oil pump to the hydraulic actuator and the oil to the oil cooler, and the greater the opening of the line pressure regulating valve, the greater the amount of oil that flows to the hydraulic actuator, and the higher the line pressure, which is the hydraulic pressure supplied to the hydraulic actuator, becomes.
a control unit that controls an opening degree of the line pressure regulating valve based on a line pressure command value that is an command value of the line pressure,
The control unit executes a setting process to set a smaller value as the upper limit of the line pressure command value as the rotation speed of the drive source decreases.

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