Vehicle control device

Abstract

To provide a vehicle control device capable of preventing unintended vehicle behavior even when air is taken in through an oil inlet.SOLUTION: A control device is for a vehicle which comprises: an oil pump which pumps up oil in an oil pan; a plurality of engaging mechanisms which adjusts pressure of the oil discharged through the oil pump to predetermined source pressure and can selectively engage according to engaging pressure adjusted from the source pressure; and an automatic transmission which sets a plurality of shift stages using the plurality of engaging mechanisms. If a predetermined condition is met for determining that the oil pump has a high possibility to take in air when pumping up the oil from the oil pan (Yes in Step S1 or Step S5), a controller makes an upper limit value of the engaging pressure to be supplied to a predetermined engaging mechanism that sets a predetermined shift stage lower than both the upper limit value when the predetermined condition is not met and the source pressure (Step S6).SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a device for controlling hydraulic pressure for engaging or disengaging a plurality of engagement mechanisms in a transmission in which a plurality of gear stages can be set by a plurality of engagement mechanisms. [Background technology]

[0002] Patent Document 1 discloses a control device for an automatic transmission that aims to prevent air intake by the oil pump when the oil temperature is low, while suppressing loss caused by the rotating member stirring the oil when the oil is in a high speed gear. The device of Patent Document 1 has a first oil reservoir that is provided below the rotating member that constitutes the power transmission device and collects oil circulating in the transmission, and a second oil reservoir that is separated from the rotating member and has an oil hole that returns oil to the first oil reservoir while restricting the flow. The device of Patent Document 1 is configured to supply oil to the second oil reservoir only when the high speed gear is set, and to prohibit the setting of the high speed gear when the oil temperature is low. In other words, the device of Patent Document 1 prohibits the setting of the high speed gear when the oil temperature is low, so that oil is not supplied to the second oil reservoir and oil is stored only in the first oil reservoir. Therefore, Patent Document 1 states that by not supplying oil to the second oil reservoir when the oil temperature is low, a sufficient amount of oil can be stored in the first oil reservoir, thereby preventing air intake by the oil pump. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-205616 Summary of the Invention [Problem to be solved by the invention]

[0004] In the device of Patent Document 1, oil is stored only in the first oil reservoir except when the high-speed gear is in operation, so that air suction caused by the drop in the oil level at low oil temperatures, as well as air suction caused by the acceleration of the vehicle at low-speed gears where the acceleration is relatively large, can be suppressed. However, air suction can occur due to a combination of factors such as the vehicle running on a slope or the vehicle experiencing high acceleration, and since there is an upper limit to the amount of oil that can be increased, it can occur unavoidably even if the oil temperature is relatively high. In other words, even if measures are taken as in the device of Patent Document 1, air suction can occur even if the oil temperature is close to the normal range due to the combination of factors such as those described above. When air suction occurs, the engine speed may increase due to insufficient hydraulic pressure, making it impossible to engage a specified engagement mechanism, or the engagement mechanism may suddenly engage unintentionally due to the hydraulic pressure returning to its original pressure after it has dropped, which may cause unintended behavior of the vehicle, such as a decrease in acceleration or shock.

[0005] The present invention has been made in consideration of the above-mentioned technical problems, and aims to provide a vehicle control device that can suppress unintended behavior of the vehicle even if air is sucked up through the oil intake port. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides a control device for a vehicle including an internal combustion engine, drive wheels, an oil pump that sucks up oil remaining in an oil pan, a plurality of engagement mechanisms that adjust the oil pressure discharged by the oil pump to a predetermined base pressure and can be selectively engaged by supplying an engagement pressure adjusted from the base pressure, and an automatic transmission that is connected between the internal combustion engine and the drive wheels and can selectively set a plurality of gear stages by engaging or disengaging the plurality of engagement mechanisms, the control device comprising a controller that controls the oil pressure supplied to the plurality of engagement mechanisms, the controller determines whether or not a predetermined condition is met for determining that there is a high possibility of air being sucked in when the oil pump sucks up the oil from the oil pan, and if the predetermined condition is met, sets the upper limit value of the engagement pressure supplied to a predetermined engagement mechanism that sets the predetermined gear stage to a value smaller than when the predetermined condition is not met and smaller than the base pressure.

[0007] In addition, in the present invention, the multiple engagement mechanisms are configured to be able to continuously change the transmission torque capacity, and the upper limit value of the engagement pressure is obtained by multiplying the base pressure supplied to the specified engagement mechanism by a specified coefficient, and the specified coefficient is set to a value that enables the transmission torque capacity of the specified engagement mechanism to be maintained when the engagement pressure supplied to the specified engagement mechanism is the base pressure and when the engagement pressure is the upper limit value.

[0008] In addition, in the present invention, the controller may be configured to calculate a value obtained by multiplying a lower limit value of the engagement pressure, at which the transmission torque capacity can be maintained when the engagement pressure supplied to the specified engagement mechanism is the original pressure, by a predetermined safety factor, and set an upper limit value of the engagement pressure to be equal to or greater than the calculated value.

[0009] In addition, in the present invention, the vehicle may further include a torque converter provided between an output shaft of the internal combustion engine and an input shaft of the automatic transmission, and the specified condition may be configured to include an output torque of the torque converter being equal to or greater than a specified threshold value.

[0010] Furthermore, in the present invention, the predetermined condition may be configured to include a condition in which the gear ratio among the plurality of gears and among forward gears, the gear ratio having the largest gear ratio is set as the target gear ratio. Effect of the Invention

[0011] The vehicle control device of the present invention is provided with an automatic transmission capable of setting multiple gear stages by generating hydraulic pressure by sucking up oil remaining in an oil pan with an oil pump, adjusting the hydraulic pressure to a predetermined base pressure, and engaging or disengaging multiple engagement mechanisms with an engagement pressure adjusted from the base pressure. The vehicle control device determines whether or not a predetermined condition is met for determining whether or not there is a high possibility of air being sucked in, i.e., so-called air suction, occurring when sucking up oil from the oil pan to set a predetermined gear stage. If the predetermined condition is met, the upper limit value of the engagement pressure supplied to engage a predetermined engagement mechanism that sets the predetermined gear stage is set to a value smaller than that when the predetermined condition is not met and smaller than the base pressure. That is, the vehicle control device of the present invention is configured to lower the engagement pressure supplied to the predetermined engagement mechanism below the base pressure when there is a high possibility of air suction occurring. Therefore, even if air suction occurs and the hydraulic pressure supplied temporarily decreases, it is possible to prevent or suppress the occurrence of a situation in which a valve provided to supply engagement pressure to the predetermined engagement mechanism does not switch over. Therefore, it is possible to prevent or suppress an increase in engine speed or an inability to set the target gear position, which would otherwise occur due to such a situation.

[0012] Furthermore, the upper limit of the engagement pressure supplied to the predetermined engagement mechanism is calculated by multiplying the base pressure by a predetermined coefficient, and the predetermined coefficient is set to a value that allows the transmission torque capacity of the predetermined engagement mechanism to be maintained when the engagement pressure supplied to the predetermined engagement mechanism is the base pressure and when the engagement pressure is the upper limit. Therefore, even if the engagement pressure supplied to the predetermined engagement mechanism decreases from the base pressure to the hydraulic pressure of the upper limit, the transmission torque capacity of the predetermined engagement mechanism is maintained, so that the vehicle can be driven with the desired gear position appropriately set.

[0013] In addition, the lower limit value for setting the upper limit value of the engagement pressure supplied to the predetermined engagement mechanism is set to a value obtained by further multiplying the lower limit value of the hydraulic pressure capable of maintaining the transmission torque capacity when the engagement pressure is the original pressure by a predetermined safety factor. Therefore, even if the engagement pressure that can be supplied to the predetermined engagement mechanism is significantly reduced due to air suction, the upper limit value is reduced accordingly, thereby preventing or suppressing a situation in which the transmission torque capacity of the predetermined engagement mechanism is reduced and it is not possible to set a predetermined gear stage. In addition, since air suction occurs only for a relatively short time, even if a lower limit is set in this way, the engagement pressure supplied to the predetermined engagement mechanism is reduced, so that a situation in which the vehicle behavior deteriorates can be suppressed compared to a case in which the upper limit value is not set.

[0014] In addition, when the output torque of the torque converter is equal to or greater than a predetermined threshold, an upper limit of the engagement pressure to be supplied to the predetermined engagement mechanism is set. Furthermore, when the gear stage with the largest gear ratio among the forward gears among the multiple gear stages is set as the target gear stage, an upper limit of the engagement pressure to be supplied to the above-mentioned predetermined engagement mechanism is set. When the output torque of the torque converter is equal to or greater than a predetermined threshold, or when the gear stage with the largest gear ratio among the forward gears is set as the target gear stage, the acceleration of the vehicle increases or is likely to increase, and there is a high possibility that air suction will occur. Therefore, by setting an upper limit of the engagement pressure in such cases, it is possible to prevent or suppress the internal combustion engine from revving up due to air suction. [Brief description of the drawings]

[0015] [Figure 1] 1 is a skeleton diagram for explaining an example of a vehicle equipped with an automatic transmission control device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram illustrating an example of a controller. [Diagram 3] 4 is a flowchart illustrating an example of control executed by the control device for the automatic transmission according to the embodiment of the present invention. [Figure 4] 3 is a time chart for illustrating changes over time in a command pressure of a first clutch, a command pressure of a line pressure, an actual oil pressure of the first clutch, and a turbine torque when the control shown in FIG. 2 is executed. [Diagram 5] 11 is an explanatory diagram for explaining an upper limit value of an engagement pressure in a predetermined engagement mechanism. FIG. [Figure 6] 11 is an explanatory diagram for explaining a lower limit value of a line pressure when an upper limit value of an engagement pressure in a predetermined engagement mechanism is set. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention will be described below based on the embodiments shown in the drawings. Note that the embodiments described below are merely examples of the present invention and are not intended to limit the present invention.

[0017] An example of a vehicle Ve according to an embodiment of the present invention will be described with reference to Fig. 1. In the vehicle Ve shown in Fig. 1, an engine (Eng) 1, which corresponds to an "internal combustion engine" in the embodiment of the present invention, and an automatic transmission 2, which is provided between the engine 1 and driving wheels (not shown) and can set a plurality of gear ratios, which are the input rotation speed relative to the output rotation speed, by engaging or disengaging each of a plurality of engagement mechanisms, are arranged side by side on the central axis of rotation of the engine 1.

[0018] The engine 1 can be configured in the same manner as a conventional gasoline engine or diesel engine, etc. That is, the engine 1 is configured to output a driving torque by burning a mixture of supplied fuel and air, and to output a braking torque according to friction torque, pumping loss, etc. by stopping the combustion of the mixture.

[0019] A torque converter 4 is connected to an output shaft 3 of the engine 1. This torque converter 4 is configured similarly to a conventional torque converter. That is, the torque converter 4 is configured with a pump impeller 5 connected to the engine 1, a turbine runner 6 arranged opposite to the pump impeller 5, and a stator 9 arranged between the pump impeller 5 and the turbine runner 6 and connected to a case 8 via a one-way clutch 7.

[0020] Furthermore, the torque converter 4 is provided with a lock-up clutch 10 for transmitting the output of the engine 1 to the automatic transmission 2 without amplifying it by the torque converter. The lock-up clutch 10 is configured to be able to engage the output shaft 3 of the engine 1 with the turbine runner 6. This lock-up clutch 10 can be configured in the same manner as a conventional lock-up clutch. In other words, the lock-up clutch 10 is configured to be able to appropriately change the rotation speed difference between the engine 1 and the turbine runner 6.

[0021] An input shaft 12 of a stepped automatic transmission 2 is connected to the output shaft 11 of the turbine runner 6. The automatic transmission 2 shown in Fig. 1 is configured to be able to set forward first to eighth gears in addition to reverse and neutral. Specifically, the automatic transmission 2 is configured from a double pinion type planetary gear mechanism 13, a Ravigneaux type planetary gear mechanism 14, four clutch mechanisms C1, C2, C3, C4 which are hydraulic friction engagement devices which are the above-mentioned multiple engagement mechanisms, and two brake mechanisms B1, B2.

[0022] The double pinion type planetary gear mechanism 13 is disposed on the opposite side of the torque converter 4 from the engine 1 on the central axis of rotation, and is composed of a sun gear 15 fixed to the case 8, a ring gear 16 disposed concentrically with the sun gear 15, an inner pinion gear 17 meshing with the sun gear 15, an outer pinion gear 18 meshing with the inner pinion gear 17 and the ring gear 16, and a carrier 19 that holds the inner pinion gear 17 and the outer pinion gear 18 so that they can rotate and revolve. The input shaft 12 of the automatic transmission 2 is connected to the carrier 19. In other words, the torque of the engine 1 is transmitted to the carrier 19.

[0023] The Ravigneaux type planetary gear mechanism 14 is disposed on the opposite side of the double pinion type planetary gear mechanism 13 from the torque converter 4, and is composed of a first sun gear 20 having a relatively large diameter, a second sun gear 21 disposed alongside the first sun gear 20 and having a smaller diameter than the first sun gear 20, a ring gear 22 disposed concentrically with the first sun gear 20, a short pinion gear 23 meshing with the second sun gear 21, a long pinion gear 24 meshing with the short pinion gear 23, the first sun gear 20, and the ring gear 22, and a carrier 25 that holds the short pinion gear 23 and the long pinion gear 24 so that they can rotate and revolve. An output gear 26 that meshes with an output member such as a differential unit (not shown) is connected to the ring gear 22.

[0024] The first clutch mechanism C1 is configured to selectively connect the ring gear 16 and the second sun gear 21. The second clutch mechanism C2 is configured to selectively connect the input shaft 12 and the carrier 25. The third clutch mechanism C3 is configured to selectively connect the ring gear 16 and the first sun gear 20. The fourth clutch mechanism C4 is configured to selectively connect the carrier 19 and the first sun gear 20. The first brake mechanism B1 is configured to selectively fix the first sun gear 20. The second brake mechanism B2 is configured to selectively fix the carrier 25. The automatic transmission 2 is configured to set one of the above-mentioned gear stages by selectively engaging these engagement mechanisms. In the following description, when describing any one of the clutch mechanisms C1, C2, C3, and C4 and the brake mechanisms B1 and B2, they may be simply referred to as engagement mechanisms.

[0025] Each of the above-mentioned first forward speed to eighth forward speed change stages is set by controlling the engaged and disengaged states of the engagement mechanisms. The following Table 1 shows each speed change stage and the engaged and disengaged states of each clutch mechanism C1, C2, C3, C4 and each brake mechanism B1, B2. In Table 1, a "○" symbol indicates an engaged state, and a blank space indicates a disengaged state. Note that in Table 1, reverse and neutral are not shown. [Table 1]

[0026] As shown in Table 1, each forward gear is set by engaging either the first clutch mechanism C1 or the second clutch mechanism C2, and either one of the third clutch mechanism C3, the fourth clutch mechanism C4, and each brake mechanism B1, B2.

[0027] Specifically, the first forward gear is set by engaging the first clutch mechanism C1 and the second brake mechanism B2. The second forward gear is set by engaging the first clutch mechanism C1 and the first brake mechanism B1. The third forward gear is set by engaging the first clutch mechanism C1 and the third clutch mechanism C3. The fourth forward gear is set by engaging the first clutch mechanism C1 and the fourth clutch mechanism C4. The fifth forward gear is set by engaging the first clutch mechanism C1 and the second clutch mechanism C2. The sixth forward gear is set by engaging the second clutch mechanism C2 and the fourth clutch mechanism C4. The seventh forward gear is set by engaging the second clutch mechanism C2 and the third clutch mechanism C3. The eighth forward gear is set by engaging the second clutch mechanism C2 and the first brake mechanism B1.

[0028] Therefore, when changing the gear between the first forward gear and the fifth forward gear, the engagement of the first clutch mechanism C1, which is commonly engaged, is maintained, and the transmission torque capacity of one of the clutch mechanisms C3, C4 or the brake mechanisms B1, B2 is reduced while the transmission torque capacity of the other is gradually increased. Similarly, when changing the gear between the fifth forward gear and the eighth forward gear, the engagement of the second clutch mechanism C2, which is commonly engaged, is maintained, and the transmission torque capacity of one of the clutch mechanisms C3, C4 or the brake mechanisms B1, B2 is reduced while the transmission torque capacity of the other is gradually increased. In other words, the gear is changed by clutch-to-clutch control like the conventional stepped automatic transmission 2.

[0029] Such a shift control is similar to a conventionally known shift control, and a shift map is prepared in advance that defines the ranges of each gear according to the accelerator opening and the vehicle speed, and a shift is performed when the accelerator opening and the vehicle speed change across a line (shift line) that defines each range. Therefore, a target gear is determined by a required driving force such as the accelerator opening and the vehicle speed or the rotation speed of a rotating member corresponding thereto, and each clutch mechanism C1, C2, C3, C4 and each brake mechanism B1, B2 are engaged and released to set the target gear. The shift control is not only capable of changing the gears one gear at a time, but also of so-called jump shift to gears that are two or more gears apart, and so-called multiple shift control in which a target gear is set via an intermediate gear (intermediate gear) during jump shift.

[0030] Each of the clutch mechanisms C1, C2, C3, and C4 and each of the brake mechanisms B1 and B2 are configured as hydraulic engagement mechanisms, that is, each of the clutch mechanisms C1, C2, C3, and C4 and each of the brake mechanisms B1 and B2 are configured to be able to change the torque capacity to be transmitted by switching between engagement and release by controlling the hydraulic pressure.

[0031] The control of engagement and release of each of the clutch mechanisms C1, C2, C3, and C4 and each of the brake mechanisms B1 and B2 is performed by a conventionally known hydraulic control device 27. Although not shown, the hydraulic control device 27 has a valve body in which multiple oil passages are formed, multiple regulator valves, multiple linear solenoid valves, etc., and adjusts the hydraulic pressure from the oil pump to supply engagement pressure to each of the clutch mechanisms C1, C2, C3, and C4 and each of the brake mechanisms B1 and B2. An example of the hydraulic control device 27 will be described below.

[0032] The hydraulic control device 27 uses a mechanical or electric oil pump to draw up oil remaining in an oil pan located under the automatic transmission 2 through a strainer. The drawn-up oil is adjusted from the oil discharge pressure of the oil pump to line pressure by a line pressure control valve such as a primary regulator valve. A linear solenoid valve is connected to the line pressure control valve, and the linear solenoid valve uses a modulator pressure, which is a constant hydraulic pressure, as the source pressure and outputs a signal pressure based on the throttle opening of the engine 1, etc. The modulator pressure is output by adjusting the modulator valve according to the biasing force of a spring when the line pressure exceeds a predetermined pressure.

[0033] The hydraulic control device 27 is provided with a control valve to which the line pressure adjusted as described above is supplied. The control valve is supplied with the line pressure through an oil passage, and the spool is operated toward one end in the axial direction against the elastic force of a spring provided inside. By operating the spool in this manner, hydraulic pressure according to the supplied line pressure is supplied to each solenoid valve provided in each of the clutch mechanisms C1, C2, C3, and C4 and each of the brake mechanisms B1 and B2. Conversely, when the supply of line pressure is stopped, the spool returns to its original position, which is the other end in the axial direction, due to the elastic force of the spring. In that case, the supply of line pressure to each solenoid valve is cut off.

[0034] Each of the clutch mechanisms C1, C2, C3, and C4 and each of the brake mechanisms B1 and B2 is provided with a hydraulic actuator, and the hydraulic pressure adjusted by each linear solenoid valve is supplied to each hydraulic actuator as the engagement pressure of the engagement mechanism. An orifice is provided in an oil passage that supplies hydraulic pressure to the linear solenoid valve of the first clutch mechanism C1. The first clutch mechanism C1 is engaged to form the first forward gear stage, so that when a so-called garage shift is performed in which forward and reverse are switched multiple times during parking, the orifice is used to slow down the rate at which the hydraulic pressure drops from the solenoid valve corresponding to the first clutch mechanism C1, thereby suppressing a delay in hydraulic response.

[0035] 2 shows a block diagram for explaining the configuration of an electronic control unit (hereinafter, simply referred to as ECU) 28 for controlling the engine 1, the clutch mechanisms C1, C2, C3, C4, and the brake mechanisms B1, B2. The ECU 28 corresponds to the "controller" in the embodiment of the present invention, and is mainly composed of a microcomputer. The ECU 28 is configured to receive data from various sensors mounted on the vehicle Ve, and to output command signals to the engine 1, the clutch mechanisms C1, C2, C3, C4, the brake mechanisms B1, B2, and the hydraulic control device 27 based on the input data and pre-stored maps and arithmetic expressions.

[0036] 2 shows an example of data input to the ECU 28. Specifically, data such as vehicle speed, accelerator opening, RPM of the output shaft 3 of the engine 1 (engine 1 RPM), output torque of the engine 1, RPM of the output shaft 11 of the torque converter 4 (i.e., input RPM of the automatic transmission 2), output RPM which is the RPM of the output gear 26, a shift range selected by a shift lever, and temperature of oil which generates engagement pressure for selectively engaging each of the clutch mechanisms C1, C2, C3, C4 and each of the brake mechanisms B1, B2 are input to the ECU 28. Based on the input data, the ECU controls the output of the engine 1, the engagement or release of each of the clutch mechanisms C1, C2, C3, C4 and each of the brake mechanisms B1, B2, the amount of oil and oil pressure supplied from the hydraulic control device 27 to parts requiring oil, and the like.

[0037] In the control device for the automatic transmission 2 configured in this manner, when the gear stage is set in the automatic transmission 2 according to the driving state of the vehicle Ve, the target gear stage is set by controlling the hydraulic pressure as described above. The hydraulic pressure for executing such control is supplied to the necessary parts by sucking up the oil dropped in the oil pan by the oil pump. Therefore, mainly when the oil temperature is lower than the oil temperature in the normal range of the oil, when the vehicle Ve is driving on an inclined driving road or when the acceleration or deceleration of the vehicle Ve changes significantly, the oil remaining in the oil pan may become uneven. In that case, the intake port of the oil pump may be exposed from the oil surface of the oil pan, and the oil pump may suck in air, which is called air suction. When air suction occurs, the line pressure decreases, so that, for example, a situation may occur in which the control valve does not switch, and the hydraulic pressure to a specific solenoid valve may suddenly drop temporarily, and the corresponding engagement mechanism may not be engaged.

[0038] In order to prevent such air suction, as described above, it is possible to change the structure by increasing the amount of oil, changing the position or direction of the oil pump intake port, or changing the shape of the oil pan. However, due to the structure of the vehicle Ve, such changes are difficult to make, and even if the amount of oil is increased, air suction may occur even when the oil temperature is close to the temperature in the normal range due to a combination of factors such as a sudden start on a road with a large incline. Therefore, in the present invention, in order to suppress a shortage of oil to each clutch mechanism C1, C2, C3, C4 and each brake mechanism B1, B2 due to a decrease in line pressure when the line pressure decreases, the engagement pressure supplied to each clutch mechanism C1, C2, C3, C4 and each brake mechanism B1, B2 is configured to be reduced in advance when there is a high possibility of air suction occurring. In other words, the hydraulic pressure required for the parts to which hydraulic pressure is supplied is kept lower than the line pressure, thereby suppressing the vehicle Ve from immediately behaving unintentionally even if air suction occurs.

[0039] A flowchart for explaining an example of such control is shown in Fig. 3. The flowchart shown in Fig. 3 is executed by appropriate components in the ECU 28. The flowchart shown in Fig. 3 is a control for determining the upper limit value of the hydraulic pressure described above when there is a possibility of air suction occurring based on the current state of the vehicle Ve and a target vehicle state when the vehicle Ve starts moving.

[0040] In step S1, it is determined that the vehicle Ve is in a steady state. That is, in step S1, it is determined whether or not a gear shift is being performed in the vehicle Ve, and whether or not a gear shift is about to be performed. For example, even if the vehicle Ve is stopped, it is determined in step S1 that the vehicle Ve is in a steady state. If it is determined that the vehicle Ve is not in a steady state, and therefore the result of the determination in step S1 is affirmative, this flow chart is temporarily terminated without executing the subsequent control.

[0041] On the other hand, if it is determined that the vehicle Ve is in a steady state because it is not performing a gear shift, the result of the determination in step S1 is affirmative and the process proceeds to step S2. If the process proceeds to step S2, it is determined that the shift range is set to the drive range. In step S2, the shift range is determined based on the operating state of a manual valve that switches the shift range between drive, reverse, neutral, etc., in accordance with the position of a shift lever mounted on the vehicle Ve. If the result of the determination in step S2 is negative because a shift range other than the drive range, such as reverse or neutral, is selected as the shift range, the process temporarily ends without executing the subsequent control.

[0042] On the other hand, if the drive range is selected as the shift range and the result of the determination in step S2 is affirmative, the process proceeds to step S3, where a gear determination is performed. In step S3, it is determined that the target gear for the vehicle Ve is a predetermined gear. The predetermined gear is a gear such as a forward first gear that relatively increases the acceleration of the vehicle Ve. Alternatively, the gear may be set according to an engagement mechanism that is likely to become unable to engage when the line pressure drops due to the structure of the hydraulic control device 27.

[0043] For example, in the above-mentioned control valve, due to its structure, a port other than the port to which the line pressure is supplied may be supplied with hydraulic pressure equivalent to the line pressure supplied to a specific linear solenoid valve, and the oil passage from the primary regulator valve to the other port may be relatively long. In that case, when the line pressure decreases due to air suction, the decrease in line pressure is not immediately reflected in the other port, and the hydraulic pressure supplied to the other port may temporarily exceed the line pressure. As a result, compared to other valves, the spool is more likely to move unintentionally, and the control valve may not switch, i.e., it is more likely to fail.

[0044] In this way, since there may be an engagement mechanism that is structurally prone to failure, in such a case, the gear that engages the engagement mechanism may be set as the predetermined gear. If the result of the negative determination in step S3 is that such a predetermined gear is not set as the target gear, the flow chart is temporarily ended without executing the subsequent control.

[0045] On the other hand, if a predetermined gear is set as the target gear and thus a positive determination is made in step S3, the process proceeds to step S4, where a turbine torque determination is performed. In step S4, it is determined whether the turbine torque is equal to or greater than a predetermined threshold. The turbine torque is calculated, for example, by multiplying the output torque of the engine 1 by the torque ratio of the torque converter. The predetermined threshold is set to a turbine torque that may cause air suction due to acceleration of the vehicle Ve, based on the amount of oil, the characteristics of the oil, the structure of the oil pan, and the like. Alternatively, it is determined in advance based on the results of experiments, simulations, and the like. If a negative determination is made in step S4 because the turbine torque is smaller than the predetermined threshold, the flow chart is temporarily terminated without executing the subsequent control.

[0046] On the other hand, if the turbine torque is equal to or greater than the predetermined threshold value and thus the answer is YES in step S4, the process proceeds to step S5, where it is determined that the oil temperature is within a predetermined range. The upper limit oil temperature in the predetermined range is set to an oil temperature at which air intake does not occur or is unlikely to occur, depending on the amount of oil, the oil characteristics, the structure of the oil pan, and the like, as described above.

[0047] The lower limit oil temperature in the predetermined region may be set in consideration of other air suction countermeasures. As described above, a structure or control for preventing air suction from occurring when the oil temperature is extremely low may already be implemented. If such countermeasures have been implemented, there is no need to execute the control for the air suction countermeasure described below, so the lower limit oil temperature in the predetermined region is set to an oil temperature that is not subject to the countermeasures. The upper limit oil temperature and the lower limit oil temperature in such a predetermined region are determined in advance based on the results of experiments, simulations, etc. If the oil temperature is outside the predetermined region and the negative determination is made in step S5, the flow chart is temporarily terminated without executing the subsequent control.

[0048] On the other hand, if the oil temperature is within the predetermined range and the result of the determination in step S5 is affirmative, the process proceeds to step S6, where air intake control is executed. In step S6, the engagement pressure required for engaging each of the clutch mechanisms C1, C2, C3, and C4 and each of the brake mechanisms B1 and B2 to set the above-mentioned predetermined gear shift stage is set to the maximum value of the hydraulic pressure that can be supplied, that is, an upper limit value that is a value smaller than the line pressure, which is the base pressure.

[0049] Normally, when each engagement mechanism is engaged, the line pressure, which is the maximum hydraulic pressure that can be supplied to each engagement mechanism, is supplied to the engagement mechanism. In other words, a hydraulic pressure greater than the hydraulic pressure required to ensure the transmission torque capacity of each engagement mechanism is generated in each hydraulic actuator of each engagement mechanism. In step S6, the upper limit of the engagement pressure supplied to each engagement mechanism is set to a value smaller than the value in the case where the conditions in steps S1 to S5 described above are not satisfied, that is, a value smaller than the line pressure.

[0050] Specifically, in step S6, the line pressure, which is the maximum hydraulic pressure that can be applied to each engagement mechanism, is multiplied by a predetermined coefficient greater than 0 and less than 1. The predetermined coefficient is set to a value that allows each engagement mechanism to maintain a transmission torque capacity equivalent to that when line pressure is supplied to each engagement mechanism, even when each engagement mechanism is engaged by an engagement pressure based on the upper limit value. In step S6, the hydraulic pressure commanded to each engagement mechanism is controlled based on the upper limit value of the engagement pressure of each engagement mechanism thus determined.

[0051] The air intake countermeasure control in step S6 will be specifically described with reference to the time chart shown in Fig. 4. In Fig. 4, the case where the first forward gear is set will be described, and the first clutch mechanism C1 will be described as a predetermined engagement mechanism corresponding to the above-mentioned predetermined linear solenoid valve. First, at time t0, the drive range is selected by the driver as the shift range, and the first forward gear is set as the target gear. In addition, the output torque of the engine 1 is increased according to the vehicle speed and the accelerator opening, and the turbine torque is increased accordingly.

[0052] By setting the first forward gear, the command hydraulic pressure to the first clutch mechanism C1 is set to a maximum value, and at time t1, the line pressure is increased according to the turbine torque, i.e., the input torque to the first clutch mechanism C1. At time t1, the line pressure outputs a hydraulic pressure according to the turbine torque such that an engagement pressure is output to an extent that slip does not occur in the first clutch mechanism C1. After that, at time t2, the hydraulic pressure actually supplied to the hydraulic actuator of the first clutch mechanism C1 is increased to a hydraulic pressure according to the line pressure. Therefore, at time t2, the transmission torque capacity of the first clutch mechanism C1 increases, and the increase rate of the turbine torque decreases accordingly.

[0053] After that, the turbine torque increases in response to the increase in the output torque of the engine 1, and at time t3, the turbine torque exceeds a predetermined threshold value, and control to increase the transmission torque capacity of the first clutch mechanism C1 is started at the same time. That is, at time t3, as the turbine torque increases, the line pressure is increased to increase the engagement pressure so as not to cause slippage in the first clutch mechanism C1, and the command oil pressure to the first clutch mechanism C1 is reduced. In other words, as the turbine torque exceeds a predetermined threshold value, the acceleration of the vehicle increases, and there is a possibility that air suction will occur. Therefore, by making the line pressure higher than the actual oil pressure of the first clutch mechanism C1, control is performed to suppress the occurrence of a control valve failure even if air suction occurs.

[0054] Specifically, the upper limit of the hydraulic pressure commanded to the first clutch mechanism C1 is set to a value obtained by multiplying the line pressure by a predetermined coefficient as described above. The lower limit of the line pressure when the hydraulic pressure commanded to the first clutch mechanism C1 is set to such an upper limit is, for example, a value obtained by multiplying a predetermined safety factor by the minimum value at which the first clutch mechanism C1 does not slip when turbine torque is input. Such an upper limit of the engagement pressure and the lower limit of the line pressure when the upper limit is set are determined in advance based on the results of experiments, simulations, etc., and are shown in Figures 5 and 6, respectively.

[0055] FIG. 5 shows the results of a trial to see whether or not a so-called failure occurs in the control valve when air suction occurs due to the conditions of steps S1 to S5 being satisfied. The vertical axis in FIG. 5 is the magnitude of the hydraulic pressure supplied to the hydraulic actuator of the first clutch mechanism C1, and the horizontal axis is the line pressure (PL pressure). The dashed line in FIG. 5 shows the case where the hydraulic pressure supplied to the first clutch mechanism C1 is the line pressure. As shown in FIG. 5, when the hydraulic pressure supplied to the first clutch mechanism C1 is the line pressure, the control valve fails regardless of the magnitude of the engagement pressure. Therefore, as a result of gradually lowering the engagement pressure supplied to the first clutch mechanism C1, the control valve does not fail even if air suction occurs at the boundary position of the solid line shown in FIG. 5. Therefore, the relationship between the engagement pressure supplied to the first clutch mechanism C1 and the line pressure that satisfies the position of the solid line is determined as a predetermined coefficient. Note that, as shown in FIG. 5, if the value multiplied by the line pressure is equal to or less than the predetermined coefficient, the control valve does not fail.

[0056] FIG. 6 shows the relationship between the lower limit of the line pressure when the upper limit of the engagement pressure of the first clutch mechanism C1 is set as described above, and the hydraulic pressure required for the first clutch mechanism C1 to secure the transmission torque capacity. As shown in FIG. 6, the lowest solid line among the four solid lines is an experimental value of the hydraulic pressure required to achieve the transmission torque capacity in the first clutch mechanism C1. The second solid line from the bottom among the four solid lines shown in FIG. 6 is an actual measurement value of the hydraulic pressure required to achieve the transmission torque capacity in the first clutch mechanism C1. The second solid line from the top among the four solid lines shown in FIG. 6 is a value obtained by multiplying the actual measurement value of the hydraulic pressure required to achieve the transmission torque capacity in the first clutch mechanism C1 by a predetermined safety factor for reliably securing the transmission torque capacity. The top solid line among the four solid lines shown in FIG. 6 is a value obtained by multiplying the actual measurement value of the hydraulic pressure required to secure the transmission torque capacity in the first clutch mechanism C1 by a predetermined safety factor and the reciprocal of a predetermined coefficient for setting the upper limit of the engagement pressure.

[0057] That is, the top solid line shown in FIG. 6 is the lower limit value of the line pressure when the upper limit value of the engagement pressure of the first clutch mechanism C1 described above is set, and when the line pressure becomes smaller than the lower limit value, the upper limit value of the engagement pressure of the first clutch mechanism C1 is not further reduced. In other words, the lower limit value when setting the upper limit value of the engagement pressure of the first clutch mechanism C1 is set to be equal to or greater than the value shown in the second solid line from the top in FIG. 6. In other words, the upper limit value of the engagement pressure is set to be equal to or greater than the value obtained by multiplying the lower limit value of the engagement pressure capable of maintaining the transmission torque capacity in the first clutch mechanism C1 by a predetermined safety factor. Therefore, even if the line pressure becomes smaller than the lower limit value, the hydraulic pressure is controlled to maintain the engagement pressure for ensuring the transmission torque capacity of the first clutch mechanism C1, so that the insufficiency of the engagement pressure of the first clutch mechanism C1 can be prevented or suppressed by setting the upper limit value of the engagement pressure.

[0058] Then, at time t4, the line pressure is increased in order to increase the hydraulic pressure supplied to the first clutch mechanism C1 in response to the increase in turbine torque. Then, at time t5, the turbine torque is reduced due to the execution of a gear shift or the arrival of a target vehicle speed, and the command hydraulic pressure for the first engagement mechanism and the line pressure are reduced accordingly. Then, at time t6, the turbine torque becomes smaller than a predetermined threshold value, and the air suction countermeasure control ends. Therefore, the hydraulic pressure supplied to the first clutch mechanism C1 is no longer restricted, and the command hydraulic pressure for the first clutch mechanism C1 is set to the maximum value.

[0059] According to the control device for the vehicle Ve in the embodiment of the present invention, when a predetermined condition is satisfied, such as the turbine torque being equal to or greater than a predetermined threshold value when a predetermined gear is set among the forward gears, the air suction countermeasure control is executed. In the air suction countermeasure control, the hydraulic pressure supplied to each engagement mechanism is reduced within a range in which slip does not occur, that is, within a range in which the transmission torque capacity can be maintained. Therefore, even if air suction occurs in the oil pump and the line pressure decreases, the hydraulic pressure supplied to the control valve and the like as described above is less likely to decrease. Therefore, it is possible to suppress the occurrence of fluctuations in hydraulic pressure linked to the decrease in the line pressure in each engagement mechanism, and to suppress the occurrence of failures in the control valve. Therefore, it is possible to prevent or suppress the occurrence of unintended behavior of the vehicle Ve, such as the inability to form a target gear because a predetermined engagement mechanism cannot be engaged, or the occurrence of a shock in the vehicle Ve due to a large fluctuation in the transmission torque capacity of the engagement mechanism. In addition, with such a configuration, the effect of air suction can be mitigated regardless of the oil temperature, so that even if the oil temperature is close to the temperature in the normal range, it is possible to suppress the occurrence of unintended behavior of the vehicle Ve due to air suction.

[0060] Although the embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned example, and may be modified as appropriate within the scope of achieving the object of the present invention. For example, in the above-mentioned control, the air suction countermeasure control is configured to be executed when the first forward gear is set, but depending on the structure of the hydraulic control device 27, it may be configured to be executed when the reverse gear is set. Even in that case, it may be configured to determine whether or not to execute the air suction countermeasure control based on the magnitude of the turbine torque, the oil temperature, etc. [Explanation of symbols]

[0061] 1 Engine 2 Automatic transmission 4 Torque converter 5. Pump impeller 6 Turbine Runner 7 One-way clutch 9 Stator 27 Hydraulic control device 28 ECU B1, B2 brake mechanism C1, C2, C3, C4 clutch mechanism Vehicle

Claims

1. A control device for a vehicle including an internal combustion engine, drive wheels, an oil pump that draws up oil remaining in an oil pan, a plurality of engagement mechanisms that adjust the oil pressure discharged by the oil pump to a predetermined base pressure and can be selectively engaged by being supplied with an engagement pressure that adjusts the base pressure, and an automatic transmission that is connected between the internal combustion engine and the drive wheels and can selectively set a plurality of gear stages by engaging or disengaging the plurality of engagement mechanisms, a controller for controlling the hydraulic pressure supplied to the engagement mechanisms; The controller: determining whether a predetermined condition is satisfied for determining that there is a high possibility that air will be sucked in by the oil pump when the oil pump sucks up the oil from the oil pan; When the predetermined condition is satisfied, the upper limit value of the engagement pressure supplied to a predetermined engagement mechanism that sets the predetermined gear stage is set to a value smaller than that when the predetermined condition is not satisfied and is set to a value smaller than the base pressure. A vehicle control device comprising:

2. The vehicle control device according to claim 1, the plurality of engagement mechanisms are configured to be capable of continuously changing a transmission torque capacity, the upper limit value of the engagement pressure is obtained by multiplying the base pressure supplied to the predetermined engagement mechanism by a predetermined coefficient; The predetermined coefficient is set to a value that can maintain the transmission torque capacity of the predetermined engagement mechanism when the engagement pressure supplied to the predetermined engagement mechanism is the base pressure and when the engagement pressure is the upper limit value. A vehicle control device comprising:

3. The vehicle control device according to claim 2, The controller: calculating a value obtained by multiplying a lower limit value of the engagement pressure capable of maintaining the transmission torque capacity when the engagement pressure supplied to the predetermined engagement mechanism is the base pressure by a predetermined safety factor; The upper limit value of the engagement pressure is set to be equal to or greater than the calculated value. A vehicle control device comprising:

4. The vehicle control device according to any one of claims 1 to 3, a torque converter provided between an output shaft of the internal combustion engine and an input shaft of the automatic transmission, The predetermined condition includes that the output torque of the torque converter is equal to or greater than a predetermined threshold value. A vehicle control device comprising:

5. The vehicle control device according to any one of claims 1 to 3, The predetermined condition includes that the gear ratio having the largest gear ratio among the plurality of forward gear ratios is set as the target gear ratio. A vehicle control device comprising:

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