JP2990367B2 - Shift negative pressure booster - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention (1) Industrial Field of the Invention The present invention is mainly for shifting a transmission of a large vehicle such as a truck by using a negative pressure of a negative pressure source. The present invention relates to a shift negative pressure booster.

(2) Prior art Such a shift negative pressure booster is disclosed, for example, in Japanese Patent Publication No. 54-3527.
It is already known as disclosed in Japanese Patent Publication No.

(3) Problems to be Solved by the Invention In the shift negative pressure booster disclosed in the above publication, the booster piston is boosted by the negative pressure of the negative pressure source according to the movement of the input member, and the shift operation is performed by the transmission. However, during the shift, no reaction force is generated on the input member, and therefore, the magnitude of the output of the booster piston cannot be perceived by the operator, so that a good shift feeling can be obtained. There is a disadvantage that there is no.

The present invention has been made in view of such circumstances, and a shift force of a booster piston acts on an input rod during a shift of a transmission so that a good shift feeling can be obtained. It is an object of the present invention to provide a shift negative pressure booster.

B. Configuration of the Invention (1) Means for Solving the Problems In order to achieve the above object, a negative pressure booster for shifting according to the present invention includes a negative pressure source; a booster shell; And a first and a second valve cylinder projecting from both ends of the booster piston and penetrating through both end walls of the booster shell; The booster pistons are respectively housed in the second valve cylinder and can move through a fixed stroke defined by an inner movement limit on the booster piston side and an outer movement limit on the opposite side. First and second reaction pistons partitioned into first and second reaction chambers on the side and first and second atmosphere chambers on the opposite side; and moving the first and second reaction pistons inward respectively. Bias towards the limit First and second urging means connected to the first and second reaction force pistons so that each reaction force piston can be driven only in a direction opposing the force of the corresponding urging means; An input member that penetrates through the second valve cylinder and is connected to the speed change lever; and a first and second bearing that are connected to the first and second valve cylinders and slidably fit and support the input member. An atmosphere introduction hole for opening the atmosphere chamber to the atmosphere; a negative pressure introduction path formed in the input member, one end of which communicates with the negative pressure source and the other end of which is open to the outer surface of the input member; When each of the reaction force pistons is located at the inward movement limit, the corresponding working chamber and reaction force chamber are shut off from the other end opening of the negative pressure introduction passage and each of the atmosphere chambers is disposed. When each reaction force piston moves toward the outward movement limit, each working chamber and reaction force chamber are connected. First and second control valves that are shut off by each atmosphere chamber and communicate with the other end opening of the negative pressure introduction path; and an output member that is driven by the booster piston to give a shift operation to the transmission. I do.

(2) Operation In the above configuration, if the first reaction force piston is moved toward the outer movement limit thereof by the speed change lever via the input member, the first operation chamber and the first operation chamber are switched by the switching operation of the first control valve. (1) Since the reaction chamber becomes incommunicable with the first atmospheric chamber and communicates with the negative pressure introduction passage (and thus the negative pressure source) in the input member, the first
And a second working chamber, and between the first atmospheric chamber and the first reaction chamber. According to the pressure difference between the first and second working chambers, the booster piston is actuated to the low working pressure side of the first working chamber to drive the output member to give the transmission a predetermined shift operation. it can. The first atmosphere chamber and the first
According to the pressure difference between the reaction force chambers, a reaction force acts on the input member, so that a reaction force corresponding to the output of the booster piston is transmitted to the pilot.

When the shift drive of the booster piston to the first working chamber side is completed, the first reaction force piston reaches the outer movement limit and prevents further movement of the input member, so that the pilot can know that the shift has ended. it can. Then, when the input to the input member is released, the first reaction force piston is returned to the inward movement limit by the first urging means, and accordingly, the first control valve connects the first working chamber and the first reaction force chamber. Since it is shut off from the negative pressure introduction passage (accordingly, a negative pressure source) in the input member and communicates with the first atmospheric chamber, it is connected between the first and second working chambers and between the first atmospheric chamber and the first reaction chamber. The pressure difference disappears, and the thrust of the booster piston and the reaction of the first reaction force piston disappear, so that the booster piston and the input member can remain in the shift position.

In particular, the air introduction hole is formed in a bearing connected to the valve cylinder and fittingly supporting the input member, so that only the negative pressure introduction passage is formed in the input member (that is, the air introduction hole is not formed). Therefore, the structure of the input member itself is made as simple and narrow as possible as compared with the case where both the air introduction hole and the negative pressure introduction path are formed in the input member, and the manufacturing process thereof is facilitated.

(3) Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, a booster shell 1 of a shift negative pressure booster B for a vehicle is fixed to an appropriate position of a vehicle body (not shown) at a mounting flange 1a at a right end thereof. A booster piston 2 is slidably fitted to the booster shell 1, so that the inside of the booster shell 1 is the first left side in the figure.
It is partitioned into a working chamber 3 ₁ and the right second working chamber 3 _2.

The booster piston 2 is provided with cylindrical connecting flanges 4 ₁ and 4 ₂ protruding from both left and right end surfaces thereof, and the first and second valve cylinders 5 ₁ and 5 ₂ are respectively connected to these connecting flanges 4 ₁ and 4 ₂ . It is fitted and fixed with a plurality of rivets 6 ₁ , 6 ₂ . These valve tube 5 _1, 5 ₂ are arranged so as to respectively slidably penetrate the left and right end walls of the booster shell 1.

Bearings 10 ₁ and 10 ₂ are screwed to outer ends of the first and second valve cylinders 5 ₁ and 5 ₂ , respectively, and the input member penetrates the valve cylinders 5 ₁ and 5 ₂ by the two bearings 10 ₁ and 10 ₂ . 11 is slidably supported.

The input member 11 is connected to the shift lever 12 at the right end. Also the output member 38 which is integrally formed on the bearing 10 ₁ of the left shift arm 39 of the transmission is attached.

The first and second valve tube 5 _1, 5 _{2 1} first and second reaction piston 7, 7 ₂ is fitted slidably. The first reaction force piston ₇₁ has a first air chamber of the first valve tube 5 within _a bearing 10 ₁ side 1
3 _1, is partitioned into first reaction chamber 14 ₁ and the booster piston 2 side. The second reaction piston 7 _2, bearing a second valve tube 5 within ₂
10 _2-side second and atmospheric chamber 13 _2, the booster piston 2 side 2
It is partitioned into a reaction chamber 14 _2. Each the bearing 10 _1, 10 ₂ air introducing hole 15 ₁ for taking air into the air chamber 13 _1, 13 ₂ corresponding, 15 ₂ are provided.

The first and second reaction force chamber 14 _1, 14 ₂ are respectively communicated with the through hole 16 _1, 16 ₂ via the first and second working chambers 3 _1, 3 _2. Second
As shown in the figure, each of the through holes 16 ₁ , 16 ₂ is provided with the rivet 6 ₁ ,
6 Like the ₂ for hole connecting flange 4 _1, 4 is ₂ and drilled through the valve tube 5 _1, 5 _2.

Referring again to FIG. 1, the first and second reaction force pistons 7 ₁ , 7
_2, their inner ends the first and second valve cylinder so as to face the surface 5 _1, 5 ₂ formed on the inner peripheral surface an annular shoulder _81, and _82, as opposed to their outer end face can slide a predetermined stroke l ₁ defined by the bearing 10 _1, 10 tubular stopper 9 ₁ formed on the inner end of the _2, 9 ₂ and the. In other words, each of the reaction force pistons 7 ₁ and 7 ₂ is restricted in its inward movement limit by the shoulders 8 ₁ and 8 ₂ ,
The outer movement limit is restricted by the stoppers 9 ₁ and 9 ₂ .

The first and the second reaction piston 7 _1, 7 _2, a shallow circular recess open to its outer end face in the corresponding reaction piston concentrically 18
_1, and 18 _2, the valve hole that penetrates the valve chamber 19 _1, 19 ₂ which opens in an eccentric location of the recess 18 _1, 18 ₂ bottom, the valve chamber 19 _1, 19 ₂ of the valve seat 20 _1, 20 ₂ 21 ₁ and 21 ₂ are provided. Valve seats 19 ₁ and 19 ₂ have a valve seat
20 _1, 20 ₂ cooperate with the first opening and closing the valve hole 21 _1, 21 _2, a second poppet valve 22 _1, 22 _2, the valve spring 2 for biasing it in the valve closing direction
3 _1, 23 ₂ and are accommodated. First and second poppet valves 22 ₁ , 22
Valve rod 24 _1, 24 ₂ of ₂ penetrates the valve hole 21 _1, 21 ₂ slidably, but is intended to protrude from the first and second reaction force piston _71, 7 ₂ of the inner end surface , cross-section so as not to close the valve hole 21 _1, 21 ₂ is formed into a cross shape (see FIG. 3).

Wherein the recess 18 _1, 18 _2, the holding plate 25 _1, 25 ₂ for supporting the valve spring 23 _1, 23 ₂ is incorporated fitted and held by the return spring 17 _1, 17 ₂ of the inner end. The return springs 17 ₁ and 17 ₂ and the holding plate 2
5 _1, 25 ₂ engages the fourth spring 17 ₁ back as shown in FIG, 17 ₂ of the inner end in the circumferential edge in order to stabilize the contact position with the annular rib 2
6 _1, 26 ₂ are formed in the holding plate 25 _1, 25 _2.

In this way, each holding plate 25 ₁ , 25 _2
1 and 7 ₂ and the return springs 17 ₁ and 17 ₂ .

The holding plate 25 ₁ , 25 ₂ has a housing 27 following the valve chambers 19 ₁ , 19 _2.
1, 27 ₂ are formed so as to bulge into the atmosphere chamber 13 _1, 13 ₂ side, the housing 27 _1, 27 air chamber 13 ₁ is in the end wall of _2, 13 ₂ opening to hole 28 _1, 28 _Two are provided. The housing 27 _1, 27 _2, filters 29 _1, 29 ₂ is loaded, wire mesh 3 to hold it
0 _1, 30 ₂ or the perforated plate is engaged with the inner end portion of the housing 27 _1, 27 _2.

Said first and second reaction force chamber 14 _1, 14 ₂ circularly shaped first and second flat valve 31 _1, 31 ₂ are disposed respectively, and these flat valves 31 _1, 31 _2, the input member It is slidably supported on 11.

The input member 11 is provided with a negative pressure introduction passage 32 having one end communicating with a negative pressure source S (for example, in an intake manifold of the engine). The other end of the negative pressure introduction passage 32 is connected to the center of the booster piston 2. The input member 11 is open to the outer peripheral surface of the input member 11 facing the negative pressure chamber 33 provided in the section, and is always in communication with the negative pressure chamber 33.

First and second flat valve 31 _1, 31 _2, the has a valve seal 34 _1, 34 ₂ which can seated on both end faces of the booster piston 2 surrounds the negative pressure chamber 33, the valve seal 34 _1, When 34 ₂ is seated on the booster piston 2, between a negative pressure chamber 33 and the reaction force chamber 14 _1, 14 ₂ is blocked, so as to communicate therebetween when separated from the booster piston 2. These flat valves 31
_1, 31 ₂ closing direction, i.e., in order to constantly urge the seating direction of the booster piston 2, the reaction piston _71, 7 ₂ and the flat valve 31 _1, 31 ₂ valve spring 35 between the ₁ , 35 ₂ is provided in a compressed state.
These valve springs 35 _1, 35 _2, the return spring 17 _1, 17 ₂ are set smaller set load than, therefore the valve spring 35 _1,
The reaction pistons 7 ₁ and 7 ₂ are not moved outward by 35 ₂ .

The first and second flat valves 31 ₁ and 31 ₂ are connected to the first and second flat valves 31 ₁ and 312, respectively.
The poppet valves 22 ₁ and 22 ₂ can receive the valve rods 24 ₁ and 24 ₂ . In particular, when the flat valves 31 ₁ and 31 ₂ are seated on the booster piston 2, the reaction pistons 7 ₁ and 7 ₂ are connected to the valve cylinders 5 ₁ and 7 ₂ .
When reaching the inward movement limit in contact with the shoulders 8 ₁ , 8 ₂ of 5 ₂ , the flat valves 31 ₁ , 31 ₂ receive the valve rods 24 ₁ , 24 ₂ and the poppet valve 22
_1, 22 ₂ is adapted to open the. At this time, the gap l ₂ between the poppet valves 22 ₁ and 22 ₂ and the valve seats 20 ₁ and 20 ₂ is
It is set smaller than the stroke l ₁ of 7 ₁ and 7 ₂ .

And Thus, a first control valve V ₁ of the present invention is constituted by the first poppet valve 22 ₁ and the first flat valve 31 _1, the second poppet valve
22 ₂ and the second second control valve V ₂ by the flat valve 31 ₂ is formed.

The input member 11 includes first and second reaction force pistons 7 ₁ , 7
₂ the first and second valve tube 5 _1, 5 ₂ of the shoulder _81, 82 reaction force piston 7 when simultaneously is in contact with the _1, 7 ₂ contact stages respectively the inner end face abuts the part 36 _1, 36 ₂ are formed, further first
And abutment ring 37 _1, 37 ₂ are provided respectively opposed to exist a gap l ₃ to the second inner end face of the flat valve 31 _1, 31 _2. Gap l ₃
Is set to l ₁ > l ₃ > l ₂ .

The booster piston 2 is provided with a seal member 40 that is in close contact with the inner peripheral surface of the booster shell 1. Also in the end walls of the booster shell 1 seal member 41 closely respectively on the outer circumferential surface of the valve tube 5 _1, 5 ₂ is mounted. More reaction piston 7 _1, 7 _2, mounting seal member 43, 43 closely respectively on the outer circumferential surface of the seal member 42 and the input member 11 closely respectively the inner peripheral surface of the valve tube 5 _1, 5 ₂ Is done. Furthermore the flat valve 31 _1, 31 _2, the sealing member 44, 44 is mounted in close respectively to the outer peripheral surface of the input member 11. Dust boots 45 are extended between the booster shell 1 and the bearings 10 ₁ and 10 ₂ , respectively.

 Next, the operation of this embodiment will be described.

FIG. 1 shows the state of the negative pressure booster B when the shift lever 12 is located at the neutral position. In this state, the booster piston 2 occupy axial center position in the booster shell 1, the first and second flat valve 31 _1, 31 ₂ are both seated on both sides of the booster piston 2, the first and second
The reaction piston _71, 7 ₂ are both the first and second valve tube 5 _1, 5 ₂ of the shoulder
8 ₁ , 8 ₂ and the first and second poppet valves 2
2 _1, 22 ₂ are opened is caught the valve rod 24 _1, 24 ₂ to the flat valve 31 _1, 31 _2.

Therefore, while each reaction chamber 14 ₁ , 14 ₂ is cut off from the negative pressure chamber 33, it is communicated with the corresponding atmosphere chamber 13 ₁ , 13 ₂ , so that the reaction chambers 14 ₁ , 14 ₂ and Like the atmosphere chambers 13 ₁ and 13 ₂ , the first and second working chambers 3 ₁ and 3 ₂ communicating with the holes 16 ₁ and 16 ₂ were introduced from the atmosphere introduction holes 15 ₁ and 15 ₂ . Filled by the atmosphere. At that time, the air chamber 13 _1, 13 ₂ from the reaction force chamber 14 _1, 14 ₂
Air flowing in is filtered by the filter 29 _1, 29 _2.
The filter 29 _1, 29 _2, the valve hole 21 _1, 21 constriction such as ₂ also performs the role of sound absorbing material for absorbing the wind noise caused when the air flows.

As a result, between the working chambers 3 ₁ and 3 ₂ and also in the atmosphere chambers 13 ₁ and 1
Since there is no pressure difference between each of the reaction force chambers 3 ₂ and the reaction force chambers 14 ₁ and 14 ₂ , the input member 11 applies the force of the return springs 17 ₁ and 17 ₂ to the reaction force pistons 7 ₁ and 7 _2. It is held in a neutral position under the skilled Seddan unit 36 _1, 36 _2.

From this state, in order to establish the selected gear train of the transmission, if moving the input member 11 by the shift lever 12 to the left in FIG. For example, first input member 11 via an equivalent Seddan 36 ₁ by leftward move the first reaction force piston ₇₁ Te, first poppet valve 22 ₁ is closed, then contact ring 37 ₁ as shown in Figure 5 causes the first opening flat valve 31 ₁ . During this time,
Change to a second closed state of the poppet valve 22 ₂ in the open state and the second flat valve 31 ₂ does not occur.

As a result, the first reaction force chamber 14 ₁ is cut off between the first air chamber 13 _1, so communicates with the negative pressure chamber 33, the first reaction chamber 14 ₁ and the first working chamber 3 ₁ , The negative pressure of the negative pressure source S is supplied through the negative pressure introducing passage 32 and the negative pressure chamber 33. Accordingly, the first
And since the second working chamber 3 _1, 3 between ₂ pressure difference larger becomes generated, the input member 11 operated booster to the first working chamber 3 ₁ side of the low pressure booster piston 2 receives this pressure difference , And a shift operation is given to the shift arm 39 via the output member 38.

During the movement of the booster piston 2, the first atmospheric chamber 13 ₁
And since the pressure difference in between the first reaction chamber 14 ₁ is generated,
This pressure difference acts become reactive force rightward in FIG. 5 in the first reaction piston _71, and transmitted to the input member 11, thereby the operator can obtain a good shift feeling.

When the establishment of the predetermined gear train leftward movement of the booster piston 2 is stopped, as shown in Figure 6 the first reaction force piston ₇₁
By but abuts against the stopper 9 _1, since the movement of the input member 11 is prevented, the operator can know the establishment of the gear train.

So if released input to the input member 11 from the shift lever 12, the first reaction force piston ₇₁ again abuts the reaction force and the return shoulder 8 ₁ of the first valve tube 5 ₁ by the force of the spring 17 ₁ To the first poppet valve 22
₁ in the open state, the second flat valve 31 ₁ is restored respectively in a closed state, the first reaction chamber 14 ₁ and the first working chamber 3 _1, second reaction chamber 14 ₂ and the second working chamber Like the 3 ₂ becomes the atmospheric pressure state.
Thus, between the two working chambers 3 ₁ and 3 ₂ , and between the atmosphere chambers 13 ₁ and 13 ₂ and the reaction chamber
Since the equilibrium state of the atmospheric pressure is returned between each of the pistons 14 ₁ and 14 ₂ , the booster piston 2 and the input member 11 can remain at the shift end position.

By the way, the poppet valves 22 ₁ and 22 ₂ and the flat valves 31 ₁ and 31 ₂
Have high sealing properties when the valve is closed, so the reaction chambers 14 ₁ ,
14 negative pressure from leaking from ₂ or the negative pressure chamber 33 to reliably prevent, it is possible to suppress unnecessary consumption of the negative pressure of the negative pressure source S.

Shift the shift lever 12 from the above state to the neutral position,
If further be operated from the neutral position to the opposite side of the shift position and the, by the second poppet valve 22 ₂ and the second flat valve 31 ₂ is switched, the booster piston 2 to follow the movement of the input member 11 It will be understood from the above operation that the boosting operation is performed in the opposite direction to the above case, and that the input member 11 is subjected to the reaction force until the operation is completed.

When the shift lever 12 is operated when the negative pressure is lost from the negative pressure chamber 33 due to the failure of the system of the negative pressure source S, the operating force is changed from the input member 11 to the reaction force piston 7 ₁ (or 7 ₂ ), the stopper 9 ₁
(Or 9 ₂ ) and mechanically transmitted to the output member 38, so that the transmission can be manually shifted.

C. Effects of the Invention As described above, according to the present invention, during the shift of the transmission,
A sufficient pressure difference according to the thrust of the booster piston
Alternatively, a reaction force is effectively applied between the atmosphere chamber and the reaction force chamber before and after the second reaction force piston, and this can be accurately transmitted to the pilot via the input member as an operation reaction force corresponding to the output of the booster piston. As a result, a good shift feeling can be given to the pilot. Further, after the shift is completed, the reaction force disappears in the same manner as the thrust of the booster piston, so that the booster piston and the input member can be prevented from moving from the shift end position.

In particular, since the air introduction hole is formed in a bearing connected to the valve cylinder and fitted and supported by the input member, only the negative pressure introduction passage is formed in the input member (that is, the air introduction hole is not formed). The structure of the input member itself can be made simpler and smaller in diameter as compared with the case where both the air introduction hole and the negative pressure introduction path are formed in the input member, and the manufacturing process thereof is easy. Cost reduction and radial miniaturization.

[Brief description of the drawings]

1 shows an embodiment of the present invention. FIG. 1 is a longitudinal sectional side view of a negative pressure booster for speed change, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is a perspective view of a poppet valve. FIG. 4 is a front view of the holding plate, and FIGS. 5 and 6 are operation explanatory diagrams. B ...... vacuum booster, S ...... negative pressure source, V _1, V ₂ ...... first and second control valves, l ₁ ...... stroke 1 ...... booster shell, 2 ...... booster piston, 3 _1, 3
₂ …… First and second working chambers, 5 ₁ , 5 ₂ …… First and second valve cylinders, 7 ₁ , 7 ₂
…… First and second reaction force pistons, 8 ₁ , 8 ₂ … Shoulders, 9 ₁ , 9 ₂ ……
Stopper, 10 ₁ , 10 ₂ … Bearing, 11… Input member, 12…
Shift lever, 13 ₁ , 13 ₂ ..., first and second atmosphere chambers, 14 ₁ , 14 ₂ ...
1st, 2nd reaction chambers, 15 ₁ , 15 ₂ … Atmospheric introduction holes, 17 ₁ , 17 ₂ …
Return springs as first and second urging means, 22 ₁ , 22 ₂ ... First
2nd poppet valve, 31 ₁ , 31 ₂ ..., 1st, 2nd flat valve, 32
… Negative pressure introduction passage, 33… Negative pressure chamber, 38… Output member, 39…
… Shift arm

Claims (1)

(57) [Claims] A negative pressure source (S); a booster shell (1);
When; booster piston which divides this booster shell (1) reciprocably housed in its interior first and second working chamber in the (3 _1, 3 ₂₎ (2) and; the booster piston (2) First and second valve cylinders (5 ₁ , 5 ₂ ) projecting from both ends of the booster shell (1) and penetrating both end walls of the booster shell (1); and inside these first and second valve cylinders (5 ₁ , 5 ₂ ), respectively. It is accommodated and can move a fixed stroke defined by an inner movement limit on the side of the booster piston (2) and an outer movement limit on the opposite side, and moves inside the first and second valve cylinders (5 ₁ , 5 ₂ ). the first and second reaction force chamber of the booster piston (2) side, respectively (14 _1, 14 ₂₎ and the first and second atmospheric chamber on the opposite side (13 _1, 13 ₂₎ and the first and second partitioning in Reaction force pistons (7 ₁ , 7 ₂ ); and first and second reaction force pistons (7 ₁ , 7 ₂ ) for urging toward the inward movement limit, respectively. First and second biasing means (17 ₁ , 17 ₂ )
And connected to the first and second reaction force pistons (7 ₁ , 7 ₂ ) so that each reaction force piston can be driven only in a direction opposing the force of the corresponding urging means (17 ₁ , 17 ₂ ). And an input member (11) penetrating through the first and second valve cylinders (5 ₁ , 5 ₂ ) and connected to the shift lever (12); and the first and second valve cylinders (5 ₁ , 5 ₂ ). Are formed in bearings (10 ₁ , 10 ₂ ) that respectively slidably fit and support the input member (11) to open the first and second atmosphere chambers (13 ₁ , 13 ₂ ) to the atmosphere. Inlet hole (15 ₁ , 15 ₂ )
A negative pressure introducing path (32) formed in the input member (11), one end of which communicates with the negative pressure source (S) and the other end of which is open to the outer surface of the input member (11); And the second valve cylinder (5 ₁ ,
5 ₂₎ respectively disposed within each reaction piston (7 _1, 7 ₂₎
Is located at the inward movement limit, the corresponding working chambers (3 ₁ , 3 ₂ ) and the reaction force chambers (14 ₁ , 14 ₂ ) are shut off from the other end opening of the negative pressure introduction path (32), and Each of the working chambers (3 ₁ , 3 ₂ ) and the reaction chamber is communicated with each atmospheric chamber (13 ₁ , 13 ₂ ), and when each reaction force piston (7 ₁ , 7 ₂ ) moves toward the outward movement limit. (14 ₁ , 1
First and second control valves (V ₁ , V ₂ ) for shutting off 4 ₂ ) from the respective atmospheric chambers (13 ₁ , 13 ₂ ) and communicating with the other end openings of the negative pressure introducing passages (32); An output member (38) driven by (2) to provide a shift operation to the transmission; and a shift negative pressure booster.