JP5041026B2 - Control device for belt type continuously variable transmission - Google Patents

Description

  The present invention relates to a control device for a belt-type continuously variable transmission mounted on a vehicle having a four-wheel drive function.

  In recent years, a continuously variable transmission (CVT) capable of changing a gear ratio steplessly has been adopted as a vehicle-mounted transmission. At present, belt-type continuously variable transmissions that combine a pair of variable-diameter pulleys and belts that span the pulleys are the mainstream as on-vehicle continuously variable transmissions. The belt type continuously variable transmission is configured to change speed by changing a ratio (pulley ratio) of belt wrapping radii of two pulleys on the input side and the output side.

  In such a belt type continuously variable transmission, the belt transmits torque while causing a slight slip to the pulley, and the motion accompanied by the slip has μ-V characteristics. In this case, energy for exciting the belt is always generated. On the other hand, the belt spanned between the two pulleys has a string portion that is not in contact with either pulley, so that string vibration is generated in the belt string portion as the continuously variable transmission operates. Become.

  Conventionally, the invention described in Patent Document 1 is known as an invention focusing on the string vibration of such a belt type continuously variable transmission. In the invention described in Patent Document 1, the occurrence of belt slip due to insufficient belt clamping pressure is detected by increasing the string vibration of the belt string portion, and when the occurrence is detected, the belt clamping pressure of the pulley is increased to detect belt slip. Try to prevent.

JP 2001-108082 A

  By the way, the resonance phenomenon occurs when the frequency of the string vibration of the belt string portion described above is matched with the natural frequency of the vehicle member, so that a roaring sound that makes the vehicle occupant feel uncomfortable may occur. Such a roaring sound is particularly noticeable in a four-wheel drive vehicle as described below.

  Some four-wheel drive vehicles have a variable torque distribution ratio between the front and rear wheels depending on the situation. And, two-wheel drive travel that travels by distributing torque only to the main drive wheels (for example, front wheels), and four-wheel drive travel that travels by distributing torque to both the main drive wheels and the auxiliary drive wheels (for example, rear wheels); There are things that switch depending on the situation. In such a four-wheel drive vehicle, the auxiliary drive wheel is drivingly connected to the transmission during four-wheel drive travel, and the drive connection is released during two-wheel drive travel. For this reason, when switching from two-wheel drive traveling to four-wheel drive traveling, the transmission range of the string vibration of the belt string portion of the belt-type continuously variable transmission is expanded, and almost no string vibration occurs during two-wheel drive traveling. String vibration is transmitted to the members that have not been transmitted during four-wheel drive. Therefore, even when there is no member that resonates with the string vibration of the belt string part during two-wheel drive traveling, a resonance phenomenon may occur according to the expansion of the transmission range of the string vibration during four-wheel drive traveling. .

  In order to avoid the occurrence of such a resonance phenomenon, it is necessary to design each member so that the natural frequency of the member installed in the transmission range of the string vibration does not match the frequency of the string vibration. However, it is difficult to make such a design for all members in the transmission range of string vibration, and even such a design can be applied to all members in the extended transmission range of string vibration during four-wheel drive driving. It becomes even more difficult to do.

  Many four-wheel drive vehicles that can switch between two-wheel drive travel and four-wheel drive travel have been developed based on two-wheel drive vehicles. Even though the two-wheel drive vehicle used as a base here is designed to prevent resonance with the string vibration of the belt string part of the belt type continuously variable transmission, There may be a member in which the resonance phenomenon occurs. In such a case, in order to eliminate any member that causes resonance, a significant design change from the base vehicle is required when the four-wheel drive function is added. For this reason, it is a fact that the prevention of the roaring noise during four-wheel drive traveling must be compromised to some extent.

  By the way, even in a four-wheel drive vehicle that always performs four-wheel drive driving, if the torque distribution of the front and rear wheels is switched according to the situation, the transmission status of the string vibration to each part of the vehicle changes according to the change of the torque distribution To do. For example, when the torque distribution ratio to the rear wheel is small, even a member that is hardly affected by string vibration may increase the influence of string vibration to a degree that cannot be ignored if the torque distribution ratio to the rear wheel increases. . Therefore, even in a four-wheel drive vehicle that always performs four-wheel drive traveling, the same problem may occur if the torque distribution of the front and rear wheels is changed.

  The present invention has been made in view of the current situation, and the problem to be solved is to effectively generate a roaring sound caused by resonance with the string vibration of the belt string portion of the belt-type continuously variable transmission. It is an object of the present invention to provide a control device for a belt type continuously variable transmission that can be suppressed to a low level.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a belt mounted on a four-wheel drive vehicle in which torque distribution of front and rear wheels is variable and spanned between two pulleys on an input side and an output side. A device for controlling a belt-type continuously variable transmission that changes speed by changing a winding radius for the two pulleys, wherein the frequency of the string vibration of the belt suppresses the occurrence of resonance due to the string vibration. The gist of the present invention is to provide a clamping pressure adjusting means for adjusting the belt clamping pressure of the pulley according to the torque distribution of the front and rear wheels.

  When the torque distribution of the front and rear wheels changes, the transmission range of the string vibration of the belt string portion of the belt-type continuously variable transmission changes, and the string vibration can be transmitted to the vehicle members that have not been transmitted until then. The intensity of the string vibration transmitted to the sound changes. As a result, the influence of the string vibration reaches a member that has not been related to the string vibration until then, and the frequency of the appropriate string vibration that can sufficiently suppress the resonance with each member is changed.

  In that respect, in the above configuration, the belt clamping pressure of the pulley is adjusted in accordance with the change in the torque distribution of the front and rear wheels so that the frequency of the string vibration of the belt becomes a frequency that suppresses the occurrence of resonance due to the string vibration. It has become. If the belt clamping pressure of the pulley is changed, the tension of the belt can be changed to change the frequency of the string vibration. Therefore, in the above configuration, even if the range of the string vibration frequency that can sufficiently suppress the resonance with the string vibration changes according to the change in the torque distribution of the front and rear wheels, the frequency of the string vibration is actually changed accordingly. Thus, the frequency of the string vibration can be set to a frequency that can suppress the occurrence of resonance due to the string vibration. Therefore, according to the above configuration, it is possible to effectively suppress the generation of a roaring sound caused by resonance with the string vibration of the belt string portion of the belt type continuously variable transmission.

  According to a second aspect of the present invention, in the control device for the belt-type continuously variable transmission according to the first aspect, the clamping pressure adjusting means has a frequency of the string vibration to a frequency capable of suppressing the occurrence of the resonance. The gist of the invention is to calculate an increase amount of the belt clamping pressure that can be changed, and to adjust the belt clamping pressure based on the calculated increase amount.

  If the belt clamping pressure is increased, not only the frequency of the string vibration of the belt string portion changes, but also the slip of the belt with respect to the pulley can be suppressed, and the magnitude of the string vibration itself can be reduced. Therefore, if the belt clamping pressure is adjusted by increasing the belt clamping pressure as in the above-described configuration, it is possible to more effectively suppress the resonance of the vehicle member due to the string vibration, and thus the generation of the roaring sound. become able to.

  According to a third aspect of the present invention, in the control device for the belt type continuously variable transmission according to the first or second aspect, the clamping pressure adjusting means has a gear ratio of the belt type continuously variable transmission within a specified range. The gist of the present invention is that the belt clamping pressure is adjusted in accordance with the torque distribution of the front and rear wheels on the condition that it exists.

  When the pulley ratio is changed to change the transmission ratio of the belt type continuously variable transmission, the string length of the belt string portion changes, and the frequency of string vibration changes. Therefore, the resonance of the vehicle member due to the string vibration may or may not occur depending on the gear ratio of the belt type continuously variable transmission. Here, in the above-described configuration, the adjustment of the belt clamping pressure according to the torque distribution of the front and rear wheels is performed on condition that the gear ratio of the belt type continuously variable transmission is within a specified range. Therefore, it is possible to adjust the belt clamping pressure only when the gear ratio of the belt-type continuously variable transmission is in a region where the resonance of the vehicle member due to string vibrations occurs as it is. By avoiding the belt clamping pressure adjustment, the resonance of the vehicle member due to the string vibration can be suppressed more efficiently.

  According to a fourth aspect of the present invention, in the control device for a belt-type continuously variable transmission according to any one of the first to third aspects, the four-wheel drive vehicle distributes torque only to the main drive wheels. Switching between two-wheel drive running for running and four-wheel drive running for running by distributing torque to both the main drive wheel and the auxiliary drive wheel according to the situation, the clamping pressure adjusting means, The gist is to determine the adjustment amount of the belt clamping pressure based on the magnitude of the torque transmitted to the auxiliary drive wheel.

  When switching from two-wheel drive running to four-wheel drive running in a four-wheel drive vehicle as described above, that is, when starting torque distribution to the sub drive wheels, string vibration generated at the belt string portion of the belt-type continuously variable transmission The transmission range is greatly expanded. As a result, the range of the vehicle member affected by the string vibration changes greatly. For this reason, when the torque distribution to the auxiliary drive wheels is started, the string vibrations are also transmitted to the vehicle members that have not been related to the string vibrations until then, and the transmission of the torque to the auxiliary drive wheels starts with the string vibrations. A resonance of the vehicle member may occur.

  Since the state of transmission of string vibration to each vehicle member changes depending on the magnitude of torque distributed to the sub drive wheel, the range of members that can resonate with the string vibration is also distributed to the sub drive wheel. It varies depending on the magnitude of torque. Therefore, the appropriate value of the string vibration frequency that can sufficiently suppress the resonance of the vehicle member may also change depending on the magnitude of the torque transmitted to the auxiliary drive wheel. In that respect, in the above configuration, the adjustment amount of the belt clamping pressure is determined by the magnitude of the torque distributed to the auxiliary drive wheels, so that it is possible to more accurately suppress the resonance of the vehicle member due to the string vibration. .

  Note that, as the clamping pressure adjusting means, as described in the fifth aspect of the invention, the clamping pressure adjusting means may be configured to maintain a constant gear ratio when adjusting the belt clamping pressure. .

BRIEF DESCRIPTION OF THE DRAWINGS The schematic which shows typically the structure of the drive system of the four-wheel drive vehicle used as the application object about 1st Embodiment of this invention. The flowchart which shows the process sequence of the belt clamping pressure adjustment routine employ | adopted as the same embodiment. The flowchart which shows the process sequence of the belt clamping pressure adjustment routine employ | adopted as 2nd Embodiment of this invention. The flowchart which shows the process sequence of the belt clamping pressure adjustment routine employ | adopted as 3rd Embodiment of this invention. The flowchart which shows the process sequence of the belt clamping pressure adjustment routine employ | adopted as 4th Embodiment of this invention. The flowchart which shows the process sequence of the belt clamping pressure adjustment routine employ | adopted as 5th Embodiment of this invention.

  (First embodiment)

  Hereinafter, a first embodiment of a control device for a belt type continuously variable transmission according to the present invention will be described in detail with reference to FIGS. 1 and 2. In the present embodiment, a belt-type continuously variable transmission mounted on a part-time four-wheel drive vehicle in which the front wheels are main drive wheels to which torque is constantly transmitted and the rear wheels are auxiliary drive wheels to which torque is transmitted only when necessary. The machine is an object to which the control device according to the present invention is applied.

  FIG. 1 shows a configuration of a drive system of a four-wheel drive vehicle to which a control device for a belt-type continuously variable transmission according to the present embodiment is applied. As shown in the figure, an engine 10 that is a drive source of the four-wheel drive vehicle is connected to a belt-type continuously variable transmission 12 via a torque converter 11. The belt-type continuously variable transmission 12 includes a pair of variable-diameter pulleys, that is, an input-side primary pulley 13 and an output-side secondary pulley 14, and a belt 15 wound around these pulleys. Shifting is performed by changing the radius ratio (pulley ratio). The belt winding radius of each pulley in the belt type continuously variable transmission 12 is adjusted by adjusting the hydraulic pressure (sheave pressure) applied to the pulleys.

  The output side of such a belt-type continuously variable transmission 12 is connected to a front differential 17 that allows the differential of the left and right front wheels 16, and the front differential 17 is connected to a propeller shaft 19 via a transfer 18 that is a diverter. ing. The propeller shaft 19 is connected to a rear differential 22 that allows differential between the left and right rear wheels 21 via an electronic control coupling 20 that changes the torque distribution of the front wheels 16 and the rear wheels 21.

  Such a four-wheel drive vehicle is provided with an electronic control unit 23 for controlling the belt type continuously variable transmission 12. The electronic control unit 23 is a central processing unit (CPU) that performs various arithmetic processes related to the control of the belt-type continuously variable transmission 12, a read-only memory (ROM) that stores control programs and data, and arithmetic results of the CPU. Are provided with a random access memory (RAM) for temporarily storing and an input / output port (I / O) for signal transmission / reception with the outside. In the input port of the electronic control unit 23, the vehicle speed, the accelerator operation amount, the torque (rear torque) transmitted to the rear wheel 21 via the electronic control coupling 20 by the sensors installed in each part of the vehicle, the electronic control Detection signals such as the input torque to the coupling 20 and the steering angle of the vehicle are input. Then, the electronic control unit 23 calculates an optimum gear ratio based on the vehicle speed and the accelerator operation amount in the current running state while the vehicle is running, and each of the belt-type continuously variable transmissions 12 so as to obtain the calculated gear ratio. The sheave pressure applied to the pulley is adjusted.

  Now, in the belt-type continuously variable transmission 12 mounted on such a four-wheel drive vehicle, the string portion (the portion not in contact with either pulley) of the belt 15 spanned between both pulleys is the belt while the vehicle is running. -Vibrates by being vibrated by a small slip between pulleys. The vibration of the belt string portion (string vibration) is transmitted to each part of the vehicle through a torque transmission path from the engine 10 to each drive wheel.

  The frequency f of such string vibration is obtained by the following equation (1). In the following formula (1), “n” is an arbitrary integer, “L” is the chord length (belt chord length), “T” is the tension of the belt 15, and “ρ” is the linear density of the belt 15. Respectively. The chord length L changes according to the change in the pulley ratio of the belt-type continuously variable transmission 12, that is, the change in the transmission ratio, and the tension T of the belt 15 changes according to the belt clamping pressure of each pulley. ing.

  On the other hand, when the natural frequency of the vehicle member to which the string vibration is transmitted matches the frequency of the string vibration, that is, the natural frequency is “m / n” times (m, n: any integer) times the frequency of the string vibration. If they match, the vehicle member causes a resonance phenomenon and a roaring sound is generated. Here, in the four-wheel drive vehicle as described above, the transmission state of the engine torque to the rear wheel 21 side changes due to the change in the torque distribution of the front and rear wheels by the electronic control coupling 20, and as a result, the transmission of the string vibrations described above. The situation changes, and the range of members affected by the string vibration changes. For example, when torque transmission to the rear wheel 21 is not performed, the influence of the string vibration may not be negligible with the start of torque transmission to the rear wheel 21 even for a member that has hardly transmitted string vibration. For this reason, even if the frequency f and the magnitude of the string vibration do not change, if the torque distribution of the front and rear wheels changes, the state of occurrence of resonance of the vehicle member due to the string vibration may change.

  Therefore, in the present embodiment, the presence / absence of torque distribution to the rear wheel 21 is monitored, and the belt clamping pressure of each pulley of the belt type continuously variable transmission 12 is adjusted according to the monitoring result so that the string vibration frequency f is set. By changing, the occurrence of resonance of the vehicle member due to the string vibration is suppressed. The adjustment of the belt clamping pressure at this time is performed by increasing the sheave pressure applied to each pulley of the belt-type continuously variable transmission 12, and simultaneously increasing the sheave pressure of both pulleys to obtain a pulley ratio (gear ratio). ) Is kept constant, and the belt clamping pressure is increased.

  In the four-wheel drive vehicle to which the present embodiment is applied, there is no member that causes resonance with the string vibration during two-wheel drive traveling using only the front wheels 16. When the four-wheel drive traveling by the front wheel 16 and the rear wheel 21 is started, there is a member that can resonate with the string vibration according to the expansion of the string vibration transmission range associated therewith. Therefore, in the present embodiment, such belt clamping pressure is adjusted in accordance with the start of torque transmission to the rear wheel 21.

  Incidentally, the adjustment of the belt clamping pressure at this time is performed for all vehicles in which the frequency f of the string vibration is affected by the string vibration in the state of torque transmission to the rear wheel 21 in the adjustable range of the belt clamping pressure. It is performed so as to deviate from the resonance frequency of the member (the natural frequency and a frequency that is “n / m” times the frequency). The adjustable range of the belt clamping pressure here is a range between the minimum value of the belt clamping pressure that can prevent the belt 15 from slipping and the belt clamping pressure when the sheave pressure is set to the maximum value. is there. Note that the range of the vehicle member affected by the string vibration changes depending on the magnitude of the torque (rear torque) transmitted to the rear wheel 21, and therefore the optimum value of the frequency f of the string vibration that can avoid the resonance of the vehicle member is It will change depending on the magnitude of the rear torque. Therefore, in this experiment, an increase in the sheave pressure that can change the frequency f of the string vibration to an optimum value that can avoid resonance is obtained in advance for each magnitude of the rear torque. The relationship between the cost and the rear torque is stored in the ROM of the electronic control unit 23 as a calculation map. Then, when adjusting the belt clamping pressure, the electronic control unit 23 uses the calculation map to obtain the optimum sheave pressure increase margin according to the magnitude of the rear torque at that time, and in accordance with the calculated increase margin, The pressure is adjusted.

  Further, in the four-wheel drive vehicle to which the present embodiment is applied, the torque distribution of the front and rear wheels is constant during normal four-wheel drive traveling except when the tire slips, etc., and the belt type continuously variable transmission 12 A linear relationship is established between the output torque and the rear torque. Therefore, in the present embodiment, the sheave pressure is adjusted using the detected value of the output torque of the belt-type continuously variable transmission 12 (for example, the torque of the secondary pulley 14) as the index value of the magnitude of the rear torque. I have to. In other words, the calculation map actually stores the relationship between the output torque of the belt-type continuously variable transmission 12 and the optimum sheave pressure increase margin at the output torque.

  FIG. 2 shows a flowchart of a “belt clamping pressure adjustment routine” employed in this embodiment. The processing of this routine is periodically executed by the electronic control unit 23 as time interruption processing while the vehicle is running.

  When this routine is started, the electronic control unit 23 first determines in step S10 whether there is torque distribution to the rear wheels 21 from the detection result of the rear torque, that is, whether the torque distribution rate of the rear wheels 21 is “0”. Check if it is. Specifically, the confirmation of the presence or absence of torque distribution to the rear wheel 21 here is performed based on whether or not the rear torque is “0”.

  Here, if there is no torque distribution to the rear wheel 21 (S10: NO), the electronic control unit 23 ends the processing of this routine as it is. On the other hand, if there is torque transmission to the rear wheel 21 (S10: YES), the electronic control unit 23 uses the calculation map stored in the ROM in step S20, and the sheave pressure according to the magnitude of the rear torque at that time. Calculate the ascending allowance. In the subsequent step S30, the electronic control unit 23 increases the sheave pressure according to the calculation result to increase the belt clamping pressure, and then ends the processing of this routine.

As described above, in the present embodiment, the belt clamping pressure is adjusted in accordance with the start of torque distribution to the rear wheel 21, and the frequency of the string vibration of the belt type continuously variable transmission 12 is changed. Therefore, by expanding the string vibration transmission range, even if there is a member that causes resonance with the string vibration when the torque distribution to the rear wheel 21 is started as it is, the occurrence of resonance is avoided to prevent a roaring sound. can do. In this embodiment, the electronic control unit 23 corresponds to the clamping pressure adjusting unit.
According to the control device for the belt type continuously variable transmission of the present embodiment described above, the following effects can be obtained.

  (1) In the present embodiment, the electronic control unit 23 adjusts the belt clamping pressure of each pulley of the belt type continuously variable transmission 12 according to the torque distribution of the front and rear wheels. When the torque distribution of the front and rear wheels changes, the transmission range of the string vibration of the belt string portion of the belt-type continuously variable transmission 12 changes, so that the string vibration can be transmitted to vehicle members that have not been transmitted until then. The intensity of the string vibration transmitted to the member changes. As a result, the influence of the string vibration reaches a member that has not been related to the string vibration until then, and the frequency of the appropriate string vibration that can sufficiently suppress the resonance with each member is changed. In this respect, in the present embodiment, the belt clamping pressure of each pulley is adjusted according to a change in torque distribution between the front and rear wheels. If the belt clamping pressure of the pulley is changed, the tension of the belt 15 changes and the frequency f of the string vibration is changed. Therefore, even if the range of the string vibration frequency that can sufficiently suppress the resonance with the string vibration changes according to the change in the torque distribution of the front and rear wheels, it is possible to actually change the string vibration frequency accordingly. It becomes. Therefore, according to the present embodiment, it is possible to effectively suppress the generation of a roaring sound caused by resonance with the string vibration of the belt string portion of the belt type continuously variable transmission 12.

  (2) In the present embodiment, the electronic control unit 23 adjusts the belt clamping pressure in accordance with the start of torque distribution to the rear wheel 21 that is the auxiliary drive wheel. When switching from two-wheel drive traveling to four-wheel drive traveling and torque distribution to the rear wheels 21 is started, the transmission range of the string vibration of the belt string portion of the belt-type continuously variable transmission 12 is expanded. Become. Therefore, the string vibration is also transmitted to a member that has not been related to the string vibration until then, and the resonance of the member due to the string vibration may occur when the torque distribution to the rear wheel 21 is started. In this respect, in the present embodiment, since the belt clamping pressure is adjusted in accordance with the start of torque distribution to the rear wheel 21, the resonance of the vehicle member due to the string vibration that causes the roaring sound is suitably suppressed. Will be able to.

  (3) In the present embodiment, the electronic control unit 23 adjusts the belt clamping pressure by increasing the belt clamping pressure. The change of the frequency f of the string vibration can be performed by either increasing or decreasing the belt clamping pressure. However, if the belt clamping pressure is increased, not only the frequency of the string vibration of the belt string portion changes, but also the slip of the belt with respect to the pulley can be suppressed, and the magnitude of the string vibration itself can be reduced. For this reason, if the belt clamping pressure is adjusted not by decreasing the clamping pressure but by increasing the belt clamping pressure, the resonance of the vehicle member due to the string vibration, and hence the generation of the roaring sound, can be more effectively performed. It becomes possible to suppress.

(4) In the present embodiment, the electronic control unit 23 determines the belt clamping pressure based on the magnitude of the transmission torque (rear torque) to the rear wheel 21 that is grasped from the output torque of the belt type continuously variable transmission 12. An increase amount of the sheave pressure at the time of adjustment is determined, and in turn, an adjustment amount of the belt clamping pressure is determined. Since the state of transmission of the string vibration to each member of the vehicle changes depending on the magnitude of the rear torque, the range of members that can resonate with the string vibration also changes depending on the magnitude of the rear torque. Therefore, the appropriate value of the string vibration frequency that can sufficiently suppress the resonance of the vehicle member also changes depending on the magnitude of the rear torque. In this respect, in the present embodiment, the adjustment amount of the belt clamping pressure is determined by the magnitude of the rear torque, and the resonance of the vehicle member due to the string vibration can be suppressed more accurately.
(Second Embodiment)

  Next, a second embodiment that embodies the control device for a belt type continuously variable transmission according to the present invention will be described with reference to FIG. 3, focusing on differences from the above embodiment. In the present embodiment and each of the following embodiments, the same or similar configurations as those of the above-described embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the four-wheel drive vehicle as described above, when one of the left and right front wheels 16 slips (idles) during two-wheel drive traveling using only the front wheels 16, and the differential amount of the left and right front wheels 16 becomes larger than a certain amount, Some start torque transmission to 21 and maintain transmission of driving force to the road surface. On the other hand, the increase in the differential amount between the left and right front wheels 16 also occurs when the steering angle of the vehicle increases, and in this case, torque distribution to the rear wheels 21 is started. Thus, there is a correlation between the steering angle of the vehicle and the torque distribution state of the front and rear wheels, and it is possible to grasp the torque distribution state to some extent from the steering angle. Therefore, in the present embodiment, the determination is made based on the confirmation of the torque distribution state of the front and rear wheels and the detection result of the steering angle of the four-wheel drive vehicle. Specifically, the steering angle is equal to or greater than a predetermined determination value. Sometimes it is determined that torque is distributed to the rear wheel 21, and the belt clamping pressure of the belt type continuously variable transmission 12 is adjusted.

  FIG. 3 shows a flowchart of a “belt clamping pressure adjustment routine” employed in this embodiment. The processing of this routine is also periodically executed by the electronic control unit 23 as time interruption processing while the vehicle is traveling.

  When this routine is started, the electronic control unit 23 first checks in step S110 whether or not the steering angle of the vehicle is equal to or greater than a predetermined determination value α. Here, the determination value α is set to the minimum value of the steering angle range in which torque distribution to the rear wheels 21 is performed by increasing the differential amount of the left and right front wheels 16. Therefore, if the steering angle is equal to or greater than the determination value α, the engine torque is distributed to the rear wheels 21.

Here, if the steering angle is less than the determination value α (S110: NO), the electronic control unit 23 ends the processing of this routine as it is. On the other hand, if the steering angle is equal to or greater than the determination value α and torque distribution to the rear wheel 21 is performed (S110: YES), the electronic control unit 23 calculates the increase in the sheave pressure in step S20, In the subsequent step S30, the belt clamping pressure is increased.
According to the control device for the belt type continuously variable transmission of the present embodiment described above, the following effects can be further obtained in addition to the effects described in the above (1) to (4).

(5) In the present embodiment, the electronic control unit 23 checks whether engine torque is distributed to the rear wheels 21 based on the detection result of the steering angle of the four-wheel drive vehicle. Since there is a correlation between the steering angle and the state of torque distribution, the state of torque distribution to each wheel can be grasped to some extent from the steering angle. Therefore, the state of torque distribution between the front and rear wheels can also be confirmed based on the detection result of the steering angle of the four-wheel drive vehicle as in the above configuration. Then, by adjusting the belt clamping pressure based on the result, it is possible to effectively suppress the generation of a roaring sound caused by resonance with the string vibration of the belt string portion of the belt type continuously variable transmission 12. Become.
(Third embodiment)
Next, a third embodiment that embodies the belt type continuously variable transmission control device of the present invention will be described with reference to FIG. 4, focusing on differences from the above embodiment.

  In the four-wheel drive vehicle as described above, the two-wheel drive traveling is usually performed only by the main drive wheel, and the four-wheel drive traveling is performed as necessary. As such a four-wheel drive vehicle, the driver can arbitrarily select the full-time four-wheel drive mode in which the torque distribution of the front and rear wheels is fixed and the four-wheel drive driving is always performed by operating a fixed switch installed in the passenger compartment. There is what I did. In such a four-wheel drive vehicle, it is possible to confirm whether engine torque is distributed to the rear wheels 21 as auxiliary drive wheels based on the operation state of the fixed switch. That is, when the fixed switch is “ON” and the full-time four-wheel drive mode is selected, it can be determined that the engine torque is distributed to the rear wheels 21. Therefore, in the present embodiment, confirmation of the presence / absence of torque distribution to the rear wheel 21 is performed based on the operation state of the fixed switch. Specifically, the rear side of the fixed switch is “ON”. It is determined that torque is distributed to the wheels 21, and the belt clamping pressure of the belt type continuously variable transmission 12 is adjusted.

  Even when the fixed switch is “OFF”, the engine torque may be distributed to the rear wheels 21 depending on the situation. However, the torque distribution to the rear wheel 21 at this time is not performed constantly, and even if the vehicle member resonates as a boundary and a squealing noise is generated, it is temporary. I am doing so.

  FIG. 4 shows a flowchart of a “belt clamping pressure adjustment routine” employed in this embodiment. The processing of this routine is also periodically executed by the electronic control unit 23 as time interruption processing while the vehicle is traveling. Here, it is assumed that the full-time 4WD mode is selected when the fixed switch is “ON”, and the part-time 4WD mode is selected when it is “OFF”.

When this routine is started, the electronic control unit 23 first checks in step S210 whether or not the fixed switch is “ON”. Here, if the fixed switch is “OFF” (S210: NO), the electronic control unit 23 ends the processing of this routine as it is. On the other hand, if the fixed switch is “ON” (S210: YES), the electronic control unit 23 calculates an increase in the sheave pressure in step S20, and then increases the belt clamping pressure in step S30.
According to the control device for the belt type continuously variable transmission of the present embodiment described above, the following effects can be further obtained in addition to the effects described in the above (1) to (4).

(6) In the present embodiment, the electronic control unit 23 confirms the presence or absence of torque distribution to the rear wheels 21 based on the operation state of a fixed switch for fixing the vehicle travel mode to four-wheel drive travel. I am doing so. As described above, it is possible to grasp the torque distribution state of the front and rear wheels to some extent also based on the operation state of the fixed switch. Then, by adjusting the belt clamping pressure based on the monitoring result, it is possible to effectively suppress the generation of a roaring sound caused by resonance with the string vibration of the belt string portion of the belt type continuously variable transmission 12. It becomes like this.
(Fourth embodiment)
Next, a fourth embodiment of the belt type continuously variable transmission control device according to the present invention will be described with reference to FIG.

  When the pulley ratio is changed to change the speed ratio γ of the belt-type continuously variable transmission 12, the winding length of the belt 15 around the pulley changes, and the chord length L of the belt chord portion also changes. . Here, as shown in the above equation (1), when the string length L of the belt string portion changes, the frequency f of the string vibration also changes. Therefore, the resonance of the vehicle member due to the string vibration may or may not occur depending on the speed ratio of the belt type continuously variable transmission 12. That is, at a certain gear ratio, even if vehicle member resonance occurs in response to the start of torque distribution to the rear wheels 21, the vehicle member resonance may not occur at another gear ratio. Therefore, in the present embodiment, adjustment of the belt clamping pressure according to the torque distribution of the front and rear wheels is performed by a specific method in which vehicle member resonance due to string vibration occurs if the speed ratio γ of the belt-type continuously variable transmission 12 remains unchanged. I do it only when it is in range.

  FIG. 5 shows a flowchart of a “belt clamping pressure adjustment routine” employed in this embodiment. The processing of this routine is also periodically executed by the electronic control unit 23 as time interruption processing while the vehicle is traveling. Here, only when the speed ratio γ of the belt-type continuously variable transmission 12 is in a range less than the specified value β, the occurrence of resonance of the vehicle member due to string vibration is concerned.

  When this routine is started, the electronic control unit 23 first checks whether torque is distributed to the rear wheels 21 in step S310. The confirmation of the presence / absence of torque distribution to the rear wheel 21 here is either the above-described method based on the detection result of the rear torque, the method based on the detection result of the steering angle, the method based on the operation state of the fixed switch, or those methods. This can be done by a combination of Here, if torque distribution to the rear wheel 21 is not made (S310: NO), the electronic control unit 23 ends the processing of this routine as it is.

On the other hand, if the torque is distributed to the rear wheels 21 (S310: YES), the electronic control unit 23 determines whether or not the speed ratio γ of the belt-type continuously variable transmission 12 is less than the predetermined value β in step S320. To check. Here, if the speed ratio γ is equal to or greater than the predetermined value β (S320: NO), the electronic control unit 23 ends the processing of this routine as it is. On the other hand, if the speed ratio γ is less than the predetermined value β and there is a possibility that resonance of the vehicle member due to string vibration may occur unless the belt clamping pressure is adjusted as it is (S320: YES), electronic control is performed. In step S20, the unit 23 calculates an increase in the sheave pressure, and in step S30, increases the belt clamping pressure.
According to the control device for the belt type continuously variable transmission of the present embodiment described above, the following effects can be further obtained in addition to the effects described in the above (1) to (4).

(7) In the present embodiment, the electronic control unit 23 adjusts the belt clamping pressure according to the torque distribution of the front and rear wheels, provided that the speed ratio γ of the belt-type continuously variable transmission 12 is within a specified range. I am trying to implement it. Therefore, it is possible to adjust the belt clamping pressure only when the speed ratio γ of the belt-type continuously variable transmission 12 is in a region where the vibration of the vehicle member due to string vibration is generated as it is. The unnecessary belt clamping pressure adjustment can be avoided, and the suppression of the resonance of the vehicle member due to the string vibration can be more efficiently achieved.
(Fifth embodiment)
Next, a fifth embodiment of the belt type continuously variable transmission control apparatus according to the present invention will be described with reference to FIG. 6 focusing on differences from the above embodiment.

  In a vehicle equipped with the belt-type continuously variable transmission 12, a sequential mode that allows a gear shifting operation like a vehicle equipped with a manual transmission may be adopted as a gear shifting mode. In such a sequential mode, shift control is performed so that the speed ratio γ of the belt-type continuously variable transmission 12 is fixed to the speed ratio corresponding to the speed selected by the driver's operation.

  Here, the frequency of the string vibration generated in the belt string portion changes according to the speed ratio γ of the belt type continuously variable transmission 12 as described above. Therefore, the resonance of the vehicle member due to the string vibration may occur only in a specific shift stage in the sequential mode. Therefore, in the present embodiment, in the sequential mode, the adjustment of the belt clamping pressure according to the torque distribution of the front and rear wheels is performed. If the currently selected shift stage is left as it is, the vehicle member may be resonated due to string vibration. This is done only when the speed is the same. For example, when in the LOW gear, if the belt clamping pressure of the belt type continuously variable transmission 12 is not adjusted, there is a possibility that the resonance of the vehicle member due to the string vibration occurs according to the torque distribution to the rear wheel 21. If there is no such probability at the gear position, the belt clamping pressure is adjusted only when the LOW gear is selected.

  FIG. 6 shows a flowchart of a “belt clamping pressure adjustment routine” employed in this embodiment. The processing of this routine is periodically executed by the electronic control unit 23 as time interruption processing when the speed change mode of the vehicle is set to the sequential mode.

  When this routine is started, the electronic control unit 23 first checks whether torque is distributed to the rear wheels 21 in step S410. The confirmation of the presence / absence of torque distribution to the rear wheels 21 is also performed by any of the above-described method based on the detection result of the rear torque, the method based on the detection result of the steering angle, the method based on the operation state of the fixed switch, or those methods. This can be done by a combination of Here, if torque distribution to the rear wheel 21 is not made (S410: NO), the electronic control unit 23 ends the processing of this routine as it is.

On the other hand, if torque is distributed to the rear wheels 21 (S410: YES), the electronic control unit 23 causes the resonance of the vehicle member due to string vibrations in step S420 if the currently selected shift stage is left as it is. It is confirmed whether or not the gear position (resonance generation gear position). Here, if the currently selected shift speed is not the resonance generation speed (S420: NO), the electronic control unit 23 ends the processing of this routine as it is. On the other hand, if the currently selected shift stage is the resonance generation shift stage and the belt member pressure is not adjusted as it is, the vehicle member will be resonated due to string vibration (S420: YES). In step S20, an increase in the sheave pressure is calculated, and in step S30, the belt clamping pressure is increased.
According to the control device for the belt type continuously variable transmission of the present embodiment described above, the following effects can be further obtained in addition to the effects described in the above (1) to (4).

(8) In the present embodiment, the electronic control unit 23 is in a sequential mode in which the speed ratio γ of the belt-type continuously variable transmission 12 is fixed to the speed ratio corresponding to the speed selected by the driver's operation. The belt clamping pressure is adjusted in accordance with the torque distribution of the front and rear wheels on the condition that a preset specific gear position is selected. For this reason, it is possible to adjust the belt clamping pressure only when the vehicle gear is in a specific shift stage that causes resonance of the vehicle member due to string vibration, and avoids unnecessary belt clamping pressure adjustment. Thus, the resonance of the vehicle member due to the string vibration can be more efficiently suppressed.
(Sixth embodiment)
Next, a sixth embodiment that embodies the control device for a belt-type continuously variable transmission according to the present invention will be described focusing on differences from the above-described embodiment.

In each of the above embodiments, the amount of increase in the sheave pressure when adjusting the belt clamping pressure, that is, the adjustment amount of the belt clamping pressure, is based on the magnitude of the torque (rear torque) distributed to the rear wheel 21 that is the auxiliary driving wheel. To decide. However, depending on the vehicle, the magnitude of the rear torque may not be monitored. In such a case, the adjustment amount of the belt clamping pressure cannot be determined directly based on the rear torque. However, the magnitude of the rear torque can be estimated roughly based on the input torque of the electronic control coupling 20 and the speed ratio γ of the belt type continuously variable transmission 12. Therefore, even when the magnitude of the rear torque is not monitored, the same belt clamping pressure adjustment can be performed by determining the adjustment amount of the belt clamping pressure based on the input torque and the gear ratio γ. Note that the input torque of the electronic control coupling 20 can be obtained by calculating from the generated torque of the engine 10 and the gear ratio γ, in addition to directly detecting the input torque.
It should be noted that each of the embodiments described above can be implemented with the following modifications.

  In the first to fifth embodiments, the torque of the secondary pulley 14 is detected as the output torque of the belt-type continuously variable transmission 12, and the detected value is used as an index value for the magnitude of the rear torque, so that the belt clamping pressure I was trying to make adjustments. However, the output torque of the belt-type continuously variable transmission 12 is obtained from the torque of an arbitrary rotating element arranged in the portion from the secondary pulley 14 to the electronically controlled coupling 20 in the torque transmission path from the engine 10 to the rear wheel 21. It is possible. Therefore, instead of the secondary pulley 14, the detected value of the torque of these rotating elements is detected as the output torque of the belt-type continuously variable transmission 12, and the detected value is used as an index value of the magnitude of the rear torque, so that the belt clamping pressure Make adjustments. Further, if the torque of a rotating element (such as the axle of the rear wheel 21) after the electronic control coupling 20 in the torque transmission path is detected, the rear torque can be directly detected, and the belt clamping pressure by directly detecting the rear torque. It is also possible to make adjustments.

  In the above embodiment, the belt clamping pressure of the belt type continuously variable transmission 12 is adjusted by increasing the belt clamping pressure more than before. However, since the frequency of the string vibration is also changed by reducing the belt clamping pressure, it is possible to suppress the resonance of the vehicle member due to the string vibration through the reduction of the belt clamping pressure. For example, when there is no room to further increase the belt clamping pressure, or when it is easier to obtain a string vibration frequency that can avoid resonance of the vehicle member than by an increase in the belt clamping pressure, It is preferable to suppress the roaring sound caused by the vibration of the vehicle member due to the string vibration through the reduction of the belt clamping pressure.

  In the above embodiment, the belt clamping pressure of the belt type continuously variable transmission 12 is adjusted in accordance with the start of torque distribution to the rear wheel 21 that is the auxiliary drive wheel. However, if the vehicle member does not resonate due to string vibration until the rear torque becomes larger than a certain level, the belt clamping pressure may be adjusted when the rear torque becomes a certain value or more.

  In the first to fourth embodiments, the adjustment amount of the belt clamping pressure is determined based on the detection result of the magnitude of the rear torque. Since the magnitude of the rear torque is adjusted by the electronic control coupling 20, it can be grasped from the control command value of the electronic control coupling 20 without directly detecting it. Therefore, even if the adjustment amount of the belt clamping pressure is determined based on the control command value of the electronic control coupling 20, the same belt clamping pressure adjustment can be performed.

  In the above embodiment, the adjustment amount of the belt clamping pressure is determined based on the detected or estimated magnitude of the rear torque. As described above, since the frequency of the string vibration generated in the belt string portion of the belt-type continuously variable transmission 12 changes depending on the speed ratio γ, an appropriate belt that can avoid the occurrence of resonance of the vehicle member due to the string vibration. The adjustment amount of the clamping pressure may vary depending on the speed ratio γ. Therefore, in such a case, it is more effective to determine the adjustment amount of the belt clamping pressure based on the speed ratio γ or, if necessary, the speed ratio γ and the result of detection and estimation of the rear torque. In addition, the resonance of the vehicle member due to the string vibration can be suppressed.

  In each of the above embodiments, the adjustment amount of the belt clamping pressure is determined based on the magnitude of the rear torque, but the adjustment amount of the belt clamping pressure that can sufficiently suppress the resonance of the vehicle member due to the string vibration. However, the adjustment amount may always be a fixed value when there is almost no change regardless of the change in the rear torque.

  In each of the above embodiments, an example in which the present invention is implemented for the belt-type continuously variable transmission 12 mounted on a four-wheel drive vehicle having the front wheels 16 as main drive wheels and the rear wheels 21 as auxiliary drive wheels. As described above, the control device according to the present invention can be similarly applied to a belt type continuously variable transmission mounted on a four-wheel drive vehicle having a rear wheel as a main drive wheel and a front wheel as a sub drive wheel.

  In each of the above embodiments, the example in which the present invention is implemented for the belt type continuously variable transmission 12 mounted on a four-wheel drive vehicle capable of switching between two-wheel drive travel and four-wheel drive travel has been described. However, even in a four-wheel drive vehicle that always performs four-wheel drive traveling, if the torque distribution of the front and rear wheels is switched according to the situation, the transmission status of the string vibration to each part of the vehicle changes according to the change in the torque distribution To do. For example, when the torque distribution ratio to the rear wheel is small, even a member that is hardly affected by string vibration may increase the influence of string vibration to a degree that cannot be ignored if the torque distribution ratio to the rear wheel increases. . Therefore, even in a four-wheel drive vehicle that always performs four-wheel drive traveling, the same problem may occur if the torque distribution of the front and rear wheels is changed. Therefore, even in such a four-wheel drive vehicle that is always four-wheel drive, if the torque distribution of the front and rear wheels is switched according to the situation, the application of the present invention can reduce the string vibration of the belt string portion of the belt-type continuously variable transmission. It is possible to suppress the occurrence of the resulting roaring sound.

  DESCRIPTION OF SYMBOLS 10 ... Engine (power source), 11 ... Torque converter, 12 ... Belt type continuously variable transmission, 13 ... Primary pulley, 14 ... Secondary pulley, 15 ... Belt, 16 ... Front wheel (main drive wheel), 17 ... Front differential, DESCRIPTION OF SYMBOLS 18 ... Transfer, 19 ... Propeller shaft, 20 ... Electronic control coupling, 21 ... Rear wheel (sub drive wheel), 22 ... Rear differential, 23 ... Electronic control unit (clamping pressure adjusting means).

Claims (5)

It is mounted on a four-wheel drive vehicle with variable torque distribution between the front and rear wheels, and the speed is changed by changing the wrapping radius of the belt spanned between the two pulleys on the input side and the output side. A device for controlling a belt-type continuously variable transmission,
There is provided a clamping pressure adjusting unit that adjusts the belt clamping pressure of the pulley according to the torque distribution of the front and rear wheels so that the frequency of the string vibration of the belt is a frequency that suppresses the occurrence of resonance due to the string vibration. A control device for a belt type continuously variable transmission. The clamping pressure adjusting means calculates an increase amount of the belt clamping pressure capable of changing the frequency of the string vibration to a frequency capable of suppressing the occurrence of the resonance, and based on the calculated increase amount The control device for a belt-type continuously variable transmission according to claim 1, wherein the belt clamping pressure is adjusted. 2. The clamping pressure adjusting means adjusts the belt clamping pressure in accordance with torque distribution of the front and rear wheels on the condition that a transmission ratio of the belt-type continuously variable transmission is within a specified range. 3. A control device for a belt-type continuously variable transmission according to 2. The four-wheel drive vehicle has two-wheel drive running in which torque is distributed only to the main drive wheel and four-wheel drive travel in which torque is distributed to both the main drive wheel and the auxiliary drive wheel. Switch according to
The belt type continuously variable according to any one of claims 1 to 3, wherein the clamping pressure adjusting means determines an adjustment amount of the belt clamping pressure based on a magnitude of the torque transmitted to the auxiliary driving wheel. Transmission control device. The control device for a belt-type continuously variable transmission according to any one of claims 1 to 4, wherein the clamping pressure adjusting means maintains a transmission ratio constant when adjusting the belt clamping pressure.

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